R E M E D I A T I O N T R E A T M E N T
Removal of phosphate and nitrate ions aqueous using
strontium magnetic graphene oxide nanocomposite: Isotherms,
kinetics, and thermodynamics studies
Hassan Sereshti
1| Elham Zamiri Afsharian
1| Mehdi Esmaeili Bidhendi
2|
Hamid Rashidi Nodeh
1,3| Muhhammad Afzal Kamboh
4| Mustafa Yilmaz
51
School of Chemistry, College of Science, University of Tehran, Tehran, Iran
2
School of Environment, College of
Engineering, University of Tehran, Tehran, Iran
3
Department of Food Science & Technology, Faculty of Food Industry and Agriculture, Standard Research Institute (SRI), Karaj, Iran
4
Department of Chemistry, Shaheed Benazir Bhutto University, Shaheed Benazirabad, Sindh, Pakistan
5
Department of Chemistry, Selcuk University, Konya, Turkey
Correspondence
Hassan Sereshti, School of Chemistry, College of Science, University of Tehran, Tehran, Iran. Email: sereshti@ut.ac.ir
Mustafa Ylmaz, Department of Chemistry, Selcuk University, Konya, Turkey. Email: myilmaz42@yahoo.com; myilmaz42@gmail.com
Abstract
Magnetic Fe
3O
4nanoparticle decorated graphene oxide (GO) was modified with
strontium nanoparticles (MGO-Sr) and applied for enhanced removal of phosphate
and nitrate ions from river and sewage water samples. The nanocomposite's features
were investigated using Fourier transform-infrared spectrometry, field
emission-scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray
dif-fraction. The effective parameters, adsorption efficiency, regeneration, and field
application of MGO-Sr were also studied. Adsorption isotherm and kinetic models
were applied for evaluation of experimental adsorption process. The data was in well
comply with Langmuir isotherm and pseudo-second-order comparing with other
models. Langmuir maximum adsorption capacity was obtained equal to 238.09 mg/g
for phosphate and 357.14 mg/g for nitrate. Van't Hoff thermodynamic predicted an
exothermic nature for adsorption process followed by a physisorption mechanism.
The prepared nanocomposite provided a high-removal efficiency toward phosphate
and nitrate ions in river and sewage water. Hence, it is applicable in water
remedia-tion process.
K E Y W O R D S
adsorption equilibrium, inorganic anions, phosphate and nitrate, magnetized GO
1
| I N T R O D U C T I O N
Recently, the increase in nutrient pollution around the world, which is caused by the excess of nitrate and phosphate ions in the air and water, is one of the most widespread, costly, and challenging environ-mental problems.1-3Nitrate is a common nitrogenous compound usu-ally generated by natural processes of the nitrogen cycle from the anthropogenic sources, including septic tanks storage, nitrogen-rich fertilizers, turf grass, and agricultural fertilizer.4,5Therefore, increasing of nitrate in environmental water poses a threat to human health.6 Proposed by the World Health Organization (WHO), concentrations lower than 10 mg/L have been stated as the safe levels of nitrates in
water sources. Phosphates are commonly used as fertilizers and also present in detergents, baking powder, toothpaste, cured meat, evapo-rated milk, soft drinks, processed cheese, pharmaceuticals, and water softeners.3,7 Not only have increasing phosphate ions brought
con-cern about several human disease it causes, it has also drawn a pro-found attention toward its effects on eutrophication.8Consequently,
WHO set the maximum level of phosphate ions in drinking water 50μg/L. Therefore, treatment and prevention methods should be considered to protect aquifers from nitrate and phosphate ions leaching.9-11 Hence, various types of water treatment techniques,
including the physical, biological, and chemical methods, are being applied to remove phosphate and nitrate from aqueous solutions.12-14
DOI: 10.1002/ep.13332
Environ Prog Sustainable Energy. 2020;39:e13332. wileyonlinelibrary.com/journal/ep © 2019 American Institute of Chemical Engineers 1 of 12 https://doi.org/10.1002/ep.13332
Electrocoagulation,15 degradation,16 and fermentation17 are
com-monly used techniques for this purpose. However, due to high-energy consumption, sustainability and by-products issues, utilization of such methods is limited. Recently, adsorption-based techniques are being developed for water decontamination due to ease of application, low cost, flexibility, and simplicity.18-21Despite all these, it is important to find a suitable adsorbent for efficient removal of pollutants. To date, engineered adsorbents, that is, carbonaceous material, polymeric adsorbents, bio-char, and metal oxide adsorbents have been success-fully used for nitrate and phosphate removal.2,21-24GO is one of the crucial carbonaceous adsorbent, that is, produced when graphite is chemically oxidized to graphite oxide and subsequently exfoliated by ultrasonication. Recently, GO-based adsorbents have received much attention due to their mechanical properties, high specific surface area, low-production cost, and stability in aqueous media.25-27
Combining magnetic nanoparticles (MNPs) such as Fe3O4and
car-bonaceous materials, the solid–liquid separation is performed easily through collection and using an external magnetic field.3,28In addition, using MNPs has several other potential benefits such as increasing sorbents surface area, having low cost, utilizing smaller particle size, and high chemical activity that could improve the adsorbent's effi-ciency.29Nevertheless, the main problem related to the nanoparticles (MNPs) is their agglomeration because they tend to reduce the sur-face energy.30Therefore, anchoring MNPs onto the graphene-based substrates efficiently avoids the nanoparticles aggregation.31
To increase the adsorption capacity, magnetic GO has been functionalized with different types of nanomaterials.32-34
Strontium-based materials have gained tremendous attention due to their promis-ing scientific35and technological36applications in various fields.
Further-more, they have relatively high electrical value, chemical stability, thermal and corrosion resistivity.37Since strontium-based nanoparticles
are positively charged (Sr2+), they are successfully used for removal of various types of ionic contaminates specially phosphate compounds.34,38
Beside, strontium-based nanoparticles were successfully applied water treatment.33,39,40
In this research, Fe3O4 MNPs are anchored onto GO substrate
and functionalized with strontium nanoparticles (MGO-Sr) to synthe-size a sorbent with a high adsorption capacity. The newly synthesynthe-sized nanocomposite is applied for phosphate and nitrate removal from aqueous solution. This could be probably ascribed by electrostatic interactions between positively charged adsorbent and negatively charged phosphate and nitrate ions. Finally, validity of the adsorption time and adsorption equilibrium are tested through isotherm and kinetic models. The proposed mechanism is confirmed by thermody-namic models.
2
| E X P E R I M E N T A L
2.1 | Reagents and chemicals
Strontium nitrate (Sr[NO3]2), methanol, sulfuric acid (H2SO4), potassium
permanganate (KMnO4), potassium di-hydrogen phosphate (KH2PO4),
sodium nitrate (NaNO3), hydrochloric acid (HCl), sodium hydroxide
(NaOH), sodium chloride (NaCl), ferrous chloride tetrahydrate (FeCl2.4H2O), ferric chloride hexahydrate (FeCl3.6H2O), ammonium
molybdate )Mo7O24(NH4).4H2O) and stannous chloride )SnCl2.2H2O)
were obtained from Merck Chemicals (Darmstadt, Germany).
2.2 | Instruments
Fourier transform-infrared spectrometry (FT-IR) spectra of the nanomaterials were recorded in the wavenumber range from 450 to 4,000 cm−1 using Bruker Equinox 55 FT-IR spectrometer (Bremen, Germany). A Field emission scanning electron microscope was from MIRA3 TESCAN (Brno, Czech Republic) used for analysis of surface morphology of the nanocomposite. A Philips X-ray diffractometer (Amsterdam, Netherlands) with angle range (2θ) from 10 to 80 (CuK radiation, λ = 1.5418A) was used for crystalline analysis of Fe3O4@GO–Sr. A Vista-MPX ICP-OES Varian, Inc. (Melbourne,
Australia) equipped with a slurry nebulizer and a charge coupled device detector was used for determination of released strontium ions in aqueous solutions.
2.3 | Synthesis of MGO-Sr nanocomposite
Magnetic graphene oxide (MGO) nanoparticles were prepared as reported by Roy et al41Strontium nanoparticles were dispersed on MGO sheets as follows. Briefly, strontium nitrate solution (0.1M) was prepared by dissolving 2.1163 g of strontium nitrate powder in distilled water, then MGO (1 g) was added into the solution. The mixture was sonicated for 30 min to achieve a homogenous mixture. Next, the solution was stirred vigorously for 1 hr at pH 11. Afterward, the solution was trans-ferred to autoclave and heated to 120C and kept at this temperature for 24 hr. Finally, the product (MGO-Sr nanoadsorbent) was separated from the solution using an external magnet, then washed with distilled water and dried at 80C for 24 hr.
2.4 | Adsorption procedure
Batch-wise adsorption was carried out by mixing a certain amount of the synthesized adsorbent in an aqueous solution containing phos-phate and nitrate ions (Figure 1). Adsorption performance of MGO-Sr nanocomposite was investigated at different pH)3–10), adsorbent dose (10–100 mg), salt concentration (0–2%, wt/vol), contact time (5–180 min), concentration of analytes (10–200 mg/L), and tempera-ture (293–308 K). After adsorption completed, the adsorbent was separated from the solution using an external magnet (Nd-Fe-B mag-net, 6× 3 × 2 cm, 1.4 Tesla). The remaining concentrations of phos-phate and nitrate ions in the solution were measured with a UV-visible spectrophotometer. For this purpose, HCl 1N (Reagent 1), and ammonium molybdate/SnCl2(Reagent 2 and 3) were used for
deter-mination nitrate and phosphate, respectively. Reagents were prepared according to our previous work,42reagent 1 (R1) is a 1 ml of HCl (1N). Reagents R2 and R3 are prepared as following; 2.5 g ammonium molybdate was dissolved in 50 ml of distilled water and then 28 ml sulfuric acid was added then diluted to 100 ml with distilled water
(R.2). In other flask, 12.5 g of tin(II)chloride was dissolved in 50 ml of glycerol (R.3). Hence, by adding of 1 ml of R.2 and 0.1 ml of R.3 into water samples contain phosphate the blue color (λmax= 690 nm) was
obtained.
The removal efficiency (E%) and adsorption capacity (qe) were
cal-culated using Equations (1) and (2), respectively.
E% = C0−Ce= C0 × 100 ð1Þ qe= V Cð 0−CeÞ= m ð Þ ð2Þ
where qe(mg/g) is the equilibrium adsorption capacity, C0(mg/L) is
the concentration of the analyte before adsorption, Ce(mg/L) is the
concentration of the analyte after adsorption, m(g) is the adsorbent dose, and V(L) is the volume of aqueous solution.
3
| R E S U L T S A N D D I S C U S S I O N
3.1 | Characterization
3.1.1 | FT-IR spectroscopy
Functional groups of Sr nanoparticles, MGO-Sr nanocomposite, and phosphate/nitrate-loaded adsorbent were analyzed with FT-IR spec-troscopy (Figure 2a). The IR spectrum (A) shows the Sr-OH2spectrum
with sharp peaks at 593 and 432 cm−1assigned for Sr O stretching vibration. The sharp peak at 3,617 cm−1confirms the excess hydrox-ide (OH−) form of strontium.43,44Furthermore, the peaks at 2,500,
1,463, and 856 cm−1can be assigned to the residual NO3−ions from
Sr(NO3)2, since these peaks are completely present in sodium nitrate's
(NaNO3) FT-IR spectrum. 45
Figure 2a(B) shows the FT-IR spectrum of MGO-Sr with various distinct peaks at 3,612 (OH−), 3,434 (O H stretching vibration), 2,921 (C H), 2,848 (C H), 1,769, 1,450 (C C/C C), 1,208 (C OH), 633 (Sr O), 558 (Fe O), and 430 cm−1 (Sr O). Additionally, the peak at 558 cm−1is corresponding to Fe O bond and the peaks at 3,612 (OH) and 633 cm−1are related to Sr O bond that confirm the presence of iron oxide and strontium oxide on the surface of MGO. Moreover, the loading of phosphate and nitrate onto the MGO-Sr was checked via FT-IR spectroscopy. Figure 2a(C) indicates that the main changes in the spectrum of MGO-Sr-phosphate have occurred in the wavenumber range from 900 to 1,100 cm−1as compared with the spectrum of MGO-Sr in Figure 2a(B). Besides, peaks at 1,024, 1,050, and 950 cm−1are ascribed to vibrations of PO43−and P OH.46,47In Figure 2a(D), the bands at 1,770, 1,383,
1,260, 1,050, and 860 cm−1are assigned to both NO3−and NO2
vibra-tions.48 These approved the successful loading of phosphate and
nitrate ions onto the as prepared nanocomposite.
3.1.2 | XRD analysis
The X-ray diffraction (XRD) technique was applied to investigate the crystallinity of MGO-Sr nanocomposite and phosphate/nitrate-loaded nanocomposite compared to that of Fe3O4MNPs which was used as
the control (Figure 2b). The presence of several main characteristics signals at 18.2, 30.16, 35.72, 43.26, 57.36, and 62.84 in the XRD profile reveals an agreeable crystalline structure for Fe3O4
MNPs. The fabricated MGO-Sr XRD profile provided several sharp peaks compared to that of Fe3O4MNPs. The sharp peak at 25.36is
assigned to graphitic structure of GO.49,50 Decorated strontium hydroxide onto MGO in MGO-Sr provided excellent crystalline struc-ture due to the appearance of several sharp XRD diffraction peaks at 16.56, 19.16, 25.36, 27.16, 3,036, 33.31, 35.86, 37.36, 42.16, 47.71, 49.96, 50.81, 51.81, 54.66, 55.82, and 62.91. Besides, the sharp and narrow signals suggest a high purity crystalline structure for strontium nanoparticles. Hence, after loading of phosphate and nitrate ions onto the nanocomposite, there appeared no significant change in XRD diffraction but peak intensity slightly decreased.
3.1.3 | Field emission-scanning electron microscopy
Surface morphology of the synthesized strontium hydroxide and MGO-Sr nanocomposite as field emission-scanning electron micros-copy (FE-SEM) micrographs are shown in Figure 3a,b, respectively. Figure 3a shows the aggregated framework of strontium hydroxide. In contrast, Figure 3b shows the smooth and uniform surface for the synthesized GO sheets. Additionally, MNPs, which are decorated onto the surface of graphene sheets, are clearly visible. Also, Figure 3b indi-cates that strontium hydroxide has been introduced onto the surface F I G U R E 1 Removal procedure of phosphate and nitrate ions
using Sr-based magnetic graphene oxide nanocomposite [Color figure can be viewed at wileyonlinelibrary.com]
F I G U R E 2 (a) FT-IR spectra of (A) strontium hydroxide nanoparticles, (B) Sr-based magnetic graphene oxide (MGO-Sr), (C) MGO-Sr-phosphate, and (D) MGO-Sr-nitrate. (b) XRD pattern for Fe3O4MNPs, MGO-Sr nanocomposite, MGO-Sr-phosphate, and MGO-Sr-nitrate. FT-IR,
Fourier transform-infrared spectrometry; XRD, X-ray diffraction [Color figure can be viewed at wileyonlinelibrary.com]
F I G U R E 3 FE-SEM micrograph for (a) strontium hydroxide and (b) MGO-Sr and EDX elemental analysis of (c) strontium hydroxide and (d) MGO-Sr nanocomposite. FE-SEM, field emission-scanning electron microscopy; MGO-Sr, Sr-based magnetic graphene oxide [Color figure can be viewed at
of GO (red line). Thus, it could be claimed that the GO substrate has successfully prevented the aggregation of magnetic and strontium nanoparticles.
3.1.4 | Energy-dispersive X-ray spectroscopy
The newly synthesized materials are further characterized with Energy-dispersive X-ray spectroscopy (EDX) elemental analysis tech-nique. Figure 3c reveals the presence of oxygen and strontium ele-ments in strontium hydroxide. Besides, after the modification of MGO with strontium, elements such as oxygen, carbon, iron, and strontium were observed in EDX spectrum of MGO-Sr nanocomposite (Figure 3d). Thus, due to the above evidence, it was concluded that the MGO-Sr nanocomposite has been synthesized successfully.
3.2 | Study of effective parameters on adsorption
The pH of sample solution is an important factor, since it may affect both the surface properties of the adsorbent and the chemical struc-ture of analytes.51-53Therefore, the removal efficiency of the adsor-bent at pH values in the range of 3–10 was studied. The results in
Figure 4a showed that in different pH regions, there was no signifi-cant difference in the adsorption efficiency. This indicates that the adsorbent can be used for the removal of phosphate and nitrate ions from water samples with different pH values. However, at pH 5–8, the removal efficiency was higher, probably because the adsorbent surface is positively charged and can attract phosphate and nitrate ions. The slight decrease in efficiency at pH >8 is probably due to the repulsion between the analytes and negatively surface charge of adsorbent. These trends can be explain by the zeta potential of mag-netic graphene-based materials which is in the pH range of ~4– 6.54,55
Besides, at pH ~6 strontium found as positive charge (Sr2+) that can increase the electrostatic interaction between ions (H2PO14−and NO3−) and adsorbent surface.
Adsorbent dosage is another parameter that could affect the sorp-tion efficiency. The effect of adsorbent dosage on the efficiency was examined by various amount of MGO-Sr (initial concentration was 20 mg/L with procedure time of 60 min). Figure 4b shows that by increasing the amount of adsorbent from 10 to 90 mg, the efficiency was increased from 63 to 95% fir phosphate ions and increased from 49 to 77% for nitrate ions. This probably is due to the increasing the adsorbent active sites. The adsorption efficiency does not increased
F I G U R E 4 Effect of pH (a) and adsorbent dosage (b) on the phosphate and nitrate adsorption efficiency and (c) influence of NaCl salt on the adsorption performance [Color figure can be viewed at wileyonlinelibrary.com]
significantly for both ions by adding of adsorbent up to 30 mg. Hence, 30 mg was considered as the optimum amount of the adsorbent.
Concentration of salt is another parameter that was investigated in the removal process of phosphate and nitrate from water media. In this study, the concentration of salt was studied according to the sorption procedure at 0, 0.01, 1, 5, and 10 (wt/vol%) and the results were displayed in Figure 4c. As it is obvious, the average removal effi-ciency of phosphate and nitrate were 78 and 98%, respectively. Hence, it could be concluded that addition of salt has no effect on removal of target ions. Thus, salt addition was ignored for further studies.
3.3 | Time dependency and adsorption kinetics
In the kinetic studies, evaluation of the influence of contact time is essential. The effect of contact time on the adsorption of phosphate and nitrate ions was investigated in the range of 5–180 min (Figure 5a). The results showed that after 90 min, the adsorption reaches equilibrium for both analytes, and further increase in contact time had no significant effect the adsorption capacity of MGO-Sr.
The adsorption kinetics was investigated by pseudo-first-order, pseudo-second-order, and intraparticle diffusion using Equations (3), (4), and (5).19,56,57 ln qð e−qtÞ = lnqe−k1t ð3Þ t =qt= 1= k2qe2+ t= qe ð4Þ qt= kit1=2+ Ci ð5Þ
In these equations, qe is the maximum adsorption capacity
(mg g−1) and qtis equilibrium adsorption capacity (mg/g) at different
times (t). k1(min−1) and k2(g mg−1min−1) are the pseudo-first-order
and pseudo-second-order rate constants, respectively. Ciis the
thick-ness of boundary layer and ki is intraparticle diffusion constant. In
Equation (3), the slope and the intercept are related to1=
qe(theoretical)
and1=
k1, respectively (Figure 5b). In Equation (4), the slope and
inter-cept correspond to qeand k2, respectively (Figure 5c). The linear
con-figuration of intraparticle diffusion (5) is shown in (Figure 5d). The reliability of the proposed models was evaluated using linear form of Equations (3–5). The computed values of the kinetic parame-ters are shown in Table 1. The pseudo-second-order model with R2> 0.99 and superior qefor both nitrate and phosphate ions was
entirely proportional to experimental contact time. In addition, the pseudo-second-order theoretical qe(136.98 mg/g for phosphate and
135.13 mg/g for nitrate ions) is thoroughly close to its experimental
F I G U R E 5 Effect of contact time on adsorption efficiency, (a) the linear configuration of kinetic models (b) first-order, (c) pseudo-second-order, and (d) intraparticle diffusion [Color figure can be viewed at wileyonlinelibrary.com]
value (133.23 mg/g for phosphate and 126.91 mg/g for nitrate ions) at 90 min (Figure 5a). Moreover, the data in Table 1 shows that the adsorption procedures gave different results for phosphate and nitrate ions. Thus, it may be controlled with various interactive (chem-ical and phys(chem-ical) adhesion. Two slopes in the intraparticle diffusion linear model (Figure 5d) suggest the possibility of the adsorption pro-cess advances through two stages. The sharp slope of the first stage indicates a fast adsorption process in the 5–60 min period and the much lower slop indicates a slow adsorption process in the 90–180 min period. The second part indicates that slow mass transfer occurs inside the adsorbent particle in adsorption process.58 It
demonstrated that adsorption of the analytes on the MGO-Sr is not controlled by intraparticle diffusion model.
3.4 | Effect of initial concentration and isotherm
studies
Initial concentration of analytes is another parameter that influences the adsorption process since materials give different adsorption capaci-ties (qe) at low and high concentration.59,60Therefore, the effect of
different concentrations of phosphate and nitrate ions (10–200 mg/L) on the adsorption performance of MGO-Sr was studied (Figure 6a(. As T A B L E 1 Kinetics models and their parameters for adsorption of phosphate and nitrate
Analytes
Model
Pseudo-first-order Pseudo-second-order Intraparticle diffusion
R2a q eb k1c R2 qe k2c R 2 1 Ci1 R 2 2 Ci2 Phosphate 0.755 94.54 0.006 0.999 136.98 0.00005 0.714 54.12 0.816 125.61 Nitrate 0.477 127.3 0.002 0.999 135.13 0.00004 0.969 10.59 0.91 103.27 aDetermination coefficient.
bThe equilibrium adsorption capacity (mg/g). c
The rate constant. Thickness of boundary layer.
F I G U R E 6 (a) Adsorption capacity, (b) Langmuir model with1= qmand
1=
kLqmas slop and intercept, respectively, (c) Freundlich model is shown in
that KFand1=nare equal to slop and intercept and eventually and (d) Dubinin–Radushkevich model in which qsindicates the slop and Kadindicates
can be seen, with increasing the concentration from 10 to 200 mg/L the qeincreased from 13.3 to 220.92 mg/g for phosphate ions and also
increased from 13.27 to 169.7 mg/g for nitrate ions. These results appropriately follow the IUPAC adsorption system (Type I) and repre-sent the single layer adsorption mechanism.61
Langmuir, Freundlich, and Dubinin–Radushkevich models were investigated to confirm the Type I system for the phosphate and nitrate ions. The following equations are linear forms of the models.62,63
Ce= qe= Ce= qm+ 1= kLqm ð6Þ ln qe= ln KF+ð ÞlnC1=n e ð7Þ ln qe= ln qs−Kadε2 ð8Þ
where qe (mg/g) is the equilibrium adsorption capacity, qm(mg/g) is
the uttermost adsorption capacity, Ce(mg/L) is the equilibrium
con-centration for ions after adsorption process, and kLis the Langmuir
constant. KF [(mg/g; L/mg) 1/n
] is Freundlich constant that defines adsorption of ions onto adsorbent.1=
nis the intensity of adsorption.
64
qs(mg/g) is the theoretical adsorption capacity and Kad(mol2kJ−2) is a
constant regarding the adsorption energy. The equation forε is given below in whichε is the isotherm constant, R (0.008314 kJ mol−1K−1) is universal gas constant, and T (K) is the temperature.
ε = RT ln 1 +1= Ce
ð8-1Þ
In addition, Langmuir model represents the single layer adsorption but Freundlich model describes the adsorption of several layers of phosphate and nitrate ions onto Fe3O4@GO–Sr. Also, Dubinin–
Radushkevich describes the multilayer adsorption by van der Waals forces. According to Equation (9), free energy of adsorption procedure for more accurate prediction of mechanism is required.
E = 2Kð adÞ1=2 ð9Þ
In which E (kJ/mol) is free energy and Kadis adsorption constant
shown at Equation (9). If the incoming value of E is less than −40 kJ/mol, adsorption mechanism follows a physical process.
Linearized forms of the three models are shown in Figure 6b–d and their given results are listed in Table 2. On the basis of determina-tion coefficient (R2) that obtained from the Langmuir, Freundlich, and Dubinin–Radushkevich models for both phosphate and nitrate ions, the adsorption process follows Langmuir model (R2> 0.98). Thus, due
to Langmuir isotherm, the adsorption mechanism occurs under a monolayer sorption pattern. Additionally, the 1/n value obtained for nitrate is lower than phosphate sorption, concluding that the adsor-bent is more appropriate for nitrate sorption. The value of qmwas
238.095 and 357.142 mg/g for phosphate and nitrate ions, respec-tively. Inappropriate qsand R
2
from Dubinin–Radushkevich indicates that the adsorption has not followed a multilayer mechanism. Finally, based on the findings (Table 2), the phosphate and nitrate ions adsorption onto the MGO-Sr follows a monolayer process (Langmuir model) and physical adsorption mechanism.
3.5 | Effect of temperature and thermodynamics
In order to define the possibility and nature of the adsorption mecha-nism, the thermodynamics studies were investigated. The effect of temperature on the adsorption of analytes onto MGO-Sr were investi-gated at 293, 298, and 308 K. According to the results given in Table 3, lnKcwas decreased with increasing the temperature.
There-fore, it can be concluded that the adsorption process is exothermic and the sorption efficiency is better at lower temperature.
The van't Hoff thermodynamic model was applied to describe the adsorption mechanism of phosphate and nitrate ions, enthalpy (ΔH, kJ/mol), entropy (ΔS, J mol−1K−1) and Gibbs free energy (ΔG, kJ/mol) were calculated using Equations (10) and (11).65,66
ln Kc=−ΔH=RT+ΔS=R ð10Þ
−ΔG = −RT lnKc ð11Þ
where KCis the thermodynamic equilibrium constant (KC= qe/Ce), qeis
the sorption capacity at equilibrium (mg/g), and Ceis the equilibrium
concentration in solution (mg/L).67 T (K) is temperature and R (0.0083145 kJ mol−1K−1) is the universal gas constant. In general, theΔG values between 0 and −20 kJ/mol indicate a physisorption
T A B L E 2 Adsorption isotherm and their parameters for the removal of phosphate and nitrate
Analytes
Isotherm
Langmuir Freundlich Dubinin–Radushkevich qma kLb R2c KFd ne R2 qsf R2
Phosphate 238.09 0.33 0.998 37.31 1.93 0.926 123.95 0.801 Nitrate 357.14 0.257 0.987 30.05 2.741 0.993 92.22 0.689
aThe uttermost adsorption capacity (mg/g). b
The Langmuir constant.
cDetermination coefficient.
dThe Freundlich constant [(mg/g; L/mg)1/n]. eA constant in Freundlich equation. f
mechanism and the values between −40 and −400 kJ/mol demon-strate a chemisorption mechanism.68-70Additionally, a positive
ΔH indicates an endothermic adsorption, while a negativeΔH indicates an exothermic adsorption. According to Table 3, the ΔG values are between 0 and−20 kJ/mol which represents the physisorption and spontaneous adsorption mechanism. According to the ΔH data, adsorption of nitrate and phosphate is exothermic. The negativeΔS indicates a decrease in randomness at the solid–liquid interface during the adsorption process.67
3.6 | Effect of coexisting ions
The coexisting ions in water samples may compete with phosphate and nitrate ions for binding on the adsorbent sites, and thus could affect the efficiency of removal process. Therefore, the influence of common ionic species in environmental water samples such as Na+, K+, Zn2+, Cu2+,Fe3+, SO42−, Br−, and Cl−was investigated. The
experi-mental conditions were: 500 mg/L of each of the mentioned ions, 50 mg of the adsorbent, and 50 mg/L of phosphate and nitrate ions. The results indicated that the removal of phosphate and nitrate ions were 91 and 80%, respectively, in the presence of the above mentioned coexisting ions.
3.7 | Real sample analysis
The field application and purification ability of MGO-Sr nano-composite was evaluated for removal of phosphate and nitrate ions from river water (Kordan River, Karaj, Iran) and wastewater (University of Tehran campus) samples. The real samples were filtered through a 0.2μm membrane for removal of suspended particles, and then the proposed procedure in section 2.4 was followed. The river water contained 0.46 mg/L phosphate and 0.06 mg/L nitrate, while the wastewater consisted of 0.09 mg/L phosphate ion and 0.36 mg/L nitrate ion. After conducting the adsorption process in the spiked river water (50 mg/L) the removal percentage were obtained 94.6 (RSD% 7.35, n = 3) and 76.7% (RSD% 6.69, n = 3) for phosphate and nitrate ions respectively. In spiked wastewater samples (50 mg/L), the removal percentage was 87.4% (RSD% 2.61, n = 3) for phosphate and 70.0% (RSD% 6.95, n = 3) for nitrate ions. These results demonstrated
the waste water complex matrices does not affect the adsorption effi-ciency. However, proposed removal percentages for phosphate and nitrate ions are acceptable in water treatment.
3.8 | Regeneration study
The regeneration protocol was carried out according to the procedure that reported previously.42After each adsorption process, the phos-phate and nitrate ions were eluted (desorbed) from MGO-Sr using 10 ml of NaOH solution (2M). Then, adsorbent was washed with excess distilled water to appropriate pH. The adsorption–desorption cycles were continued for fifth times. After fifth cycle, the removal efficiencies were declined to 74% for phosphate and 68% for nitrate ions. Thus, the proposed adsorbent can regenerate at least three times with high-removal efficiency (88% for phosphate and 80% for nitrate ions).
3.9 | Adsorption mechanism
The sorption mechanism for phosphate and nitrate ions uptake on the MGO-Sr adsorbent could be ascribed as follows. In the case of phos-phate ions the dissociation constants are pK1= 2.12, pK2= 7.21, and
pK3= 12.67.71 H3PO4$ K1 H2PO4−+ H+$ K2 HPO42−+ 2H+$ K3 PO43−+ 3H+
In pH 3–7, phosphate is dominant species in solution is H2PO1−4 . According to literature, graphene-based material possess surface zeta-potential is about ~5− 6. Thus, adsorbent surface is neutral at this pH level. At pH ~6 due to strontium's positive charge (Sr2+), surface charge remains positive with H2PO1−4 ion adsorption on MGO-Sr through electrostatic interactions. Consequently, in this pH range (~6), nitrate uptake occurs favorably. For pH values above 8, the adsorbent surface becomes negatively charged. Due to the negative charge of analytes, the uptake of ions decreases with increasing pH. Driving force of the adsorbing process is electrostatic attraction between the phosphate and nitrate anions and cations (Sr2+).
T A B L E 3 The thermodynamic parameters for adsorption of phosphate and nitrate ions onto MGO-Sr
Analytes Thermodynamic parameters ΔGa ΔHd ΔSe lnKCb 293Kc 298K 308K 293K 298K 308K Phosphate −13.59 −10.94 −9.07 −97.27 −0.28 4.49 3.86 3.47 Nitrate −10.94 −9.56 −8.91 −48.11 −0.12 5.58 4.42 3.54 Abbreviation: MGO-Sr, Sr-based magnetic graphene oxide.
a
Gibbs free energy (kJ/mol).
bThe thermodynamic equilibrium constant. cKelvin.
dEnthalpy (kJ/mol). e
3.10 | Comparison with other methods
Table 4 shows the comparison between different adsorbents for removal of phosphate and nitrate ions in recent years regarding to the time, pH, and qeparameters. The proposed adsorbent was compared
with MGO, 3D graphene, activated carbon, and magnetic chitosan. Comparing the results of MGO-Sr with MGO and other adsorbents, the synthesized MGO-Sr shows a quite high adsorption capacity at less adsorption time at pH ~6.
4
| C O N C L U S I O N
Nowadays, removal of phosphate and nitrate ions in drinking water is an important issue for their potential health effects. In this study, a new adsorbent (MGO-Sr) with high adsorption performance for phos-phate and nitrate ions from water sources was synthesized. The pro-posed procedure resulted in high qe (238.09 and 357.17 mg/g for
phosphate and nitrate, respectively) using 30 mg of adsorbent at pH ~6. The Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models were used to investigate the adsorption process and ulti-mately, based on findings, phosphate and nitrate uptake follows a monolayer sorption process under Langmuir model. Pseudo-first-order, pseudo-second-Pseudo-first-order, and intraparticle diffusion kinetic models were applied to describe the adsorption rate. According to the results, phosphate and nitrate ions removal follow the pseudo-second-order model, and not under the terms of intraparticle diffusion. Moreover, the thermodynamic model of van't Hoff shoed that adsorption of the target ions onto the MGO-Sr is an exothermic physisorption process. Finally, MGO-Sr could be used as an efficient sorbent for the enhanced removal of phosphate and nitrate ions from water.
A C K N O W L E D G M E N T S
The authors would like to thank the central laboratory, Faculty of Science for facilities and University of Tehran, Iran's National Elites
Foundation, and Iran High-Tech Laboratory Network for the financial support through the research grants.
O R C I D
Hassan Sereshti https://orcid.org/0000-0002-6300-1954
Hamid Rashidi Nodeh https://orcid.org/0000-0002-7920-289X
R E F E R E N C E S
1. Sowmya A, Meenakshi S. Effective utilization of the functional groups in chitosan by loading Zn (II) for the removal of nitrate and phosphate. Desalin. Water Treat. 2015;54:1674-1683. https://doi.org/10.1080/ 19443994.2014.891467.
2. Bock E, Smith N, Rogers M, et al. Enhanced nitrate and phosphate removal in a denitrifying bioreactor with biochar. J Environ Qual. 2015;44:605-613. https://doi.org/10.2134/jeq2014.03.0111. 3. Ogata F, Ueda A, Tanei S, Imai D, Kawasaki N. Simultaneous removal
of phosphate and nitrite ions from aqueous solutions using modified soybean waste. J. Ind. Eng. Chem. 2016;35:287-294. https://doi.org/ 10.1016/j.jiec.2016.01.007.
4. Stayner LT, Almberg K, Jones R, Graber J, Pedersen M, Turyk M. Atra-zine and nitrate in drinking water and the risk of preterm delivery and low birth weight in four Midwestern states. Environ Res. 2017;152: 294-303.
5. Sadler R, Maetam B, Edokpolo B, et al. Health risk assessment for exposure to nitrate in drinking water from village wells in Semarang, Indonesia. Environ Pollut. 2016;216:738-745.
6. Espejo-Herrera N, Cantor KP, Malats N, et al. Nitrate in drinking water and bladder cancer risk in Spain. Environ Res. 2015;137: 299-307.
7. Wang F, Liu D, Zheng P, Ma X. Synthesis of rectorite/Fe 3 O 4-CTAB composite for the removal of nitrate and phosphate from water. J Ind Eng Chem. 2016;41:165-174. https://doi.org/10.1016/j.jiec.2016. 07.017.
8. Lalley J, Han C, Mohan GR, et al. Phosphate removal using modified Bayoxide® E33 adsorption media. Environ Sci Water Res Technol.
2015;1:96-107. https://doi.org/10.1039/C4EW00020J.
9. Hamoudi S, Belkacemi K. Adsorption of nitrate and phosphate ions from aqueous solutions using organically-functionalized silica materials: T A B L E 4 Comparison with the recent studies
Material Analyte pH Time (min) qe(mg/g) References
MGO-Sr Phosphate ~6 90 238.09 This study
Nitrate 357.17
MGO Phosphate ~6 90 133.11 This study
Nitrate 117.40
3D graphene−La2O3composite Phosphate 6.2 25 82.6 26
Mg-MCMBa Phosphate 5.2 180 588.4 72
Activated carbon residue (ACR) Nitrate 4 150 3.8 73
Phosphate 6 750 0.8
Activate carbon (AC) Phosphate 4 500 0.7 73
Nitrate 6 1,500 3.6
Fe3O4/ZrO2/chitosan Phosphate ~6 480 26.5 74
Nitrate 240 89.3
Abbreviation: MGO, magnetic graphene oxide; MGO-Sr, Sr-based magnetic graphene oxide.
a
kinetic modeling. Fuel. 2013;110:107-113. https://doi.org/10.1016/j. fuel.2012.09.066.
10. Olgun A, Atar N, Wang S. Batch and column studies of phosphate and nitrate adsorption on waste solids containing boron impurity. Chem Eng J. 2013;222:108-119. https://doi.org/10.1016/j.cej.2013. 02.029.
11. Warwick C, Guerreiro A, Soares A. Biosensors and bioelectronics sensing and analysis of soluble phosphates in environmental samples: a review. Biosens Bioelectron. 2013;41:1-11. https://doi.org/10.1016/ j.bios.2012.07.012.
12. Mook WT, Chakrabarti MH, Aroua MK, et al. Removal of total ammo-nia nitrogen (TAN), nitrate and total organic carbon (TOC) from aqua-culture wastewater using electrochemical technology: a review. Desalination. 2012;285:1-13. https://doi.org/10.1016/j.desal.2011. 09.029.
13. Aloui F, Kchaou S, Sayadi S. Physicochemical treatments of anionic surfactants wastewater: effect on aerobic biodegradability. J Hazard Mater. 2009;164:353-359. https://doi.org/10.1016/j.jhazmat.2008. 08.009.
14. Rezaee A, Safari M, Hossini H. Bioelectrochemical denitrification using carbon felt/multiwall carbon nanotube. Environ Technol. 2015; 36:1057-1062. https://doi.org/10.1080/09593330.2014.974680. 15. Tian Y, He W, Zhu X, Yang W, Ren N, Logan BE. Improved
electro-coagulation reactor for rapid removal of phosphate from wastewater. ACS Sustain Chem Eng. 2017;5:67-71. https://doi.org/10.1021/ acssuschemeng.6b01613.
16. Ma Z, Yang Y, Jiang Y, Xi B, Lian X, Xu Y. Effects of anions on bio-chemical degradation of nitrate in groundwater. Environ Earth Sci. 2015;74:3985-3992. https://doi.org/10.1007/s12665-015-4454-z. 17. Yuan Y, Liu J, Ma B, Liu Y, Wang B, Peng Y. Improving municipal
wastewater nitrogen and phosphorous removal by feeding sludge fer-mentation products to sequencing batch reactor (SBR). Bioresour Technol. 2016;222:326-334. https://doi.org/10.1016/j.biortech. 2016.09.103.
18. Zhang M, Gao B, Yao Y, Xue Y, Inyang M. Synthesis of porous MgO-biochar nanocomposites for removal of phosphate and nitrate from aqueous solutions. Chem Eng J. 2012;210:26-32. https://doi.org/10. 1016/j.cej.2012.08.052.
19. Habila MA, Alothman ZA, Al-Tamrah SA, Ghafar AA, Soylak M. Acti-vated carbon from waste as an efficient adsorbent for malathion for detection and removal purposes. J. Ind. Eng. Chem. 2015;32:336-344. https://doi.org/10.1016/j.jiec.2015.09.009.
20. Ali I. New generation adsorbents for water treatment. Chem Rev. 2012;112:5073-5091. https://doi.org/10.1021/cr300133d. 21. Akceylan E, Yilmaz A, Yilmaz M. Synthesis and properties of calix
[4] arene polymers containing amide groups: exploration of their extraction properties towards dichromate and nitrite anions. Macromol Res. 2013;21:1091-1096.
22. Bozorgpour F, Ramandi HF, Jafari P, Samadi S, Yazd SS, Aliabadi M. Removal of nitrate and phosphate using chitosan/Al 2 O 3/Fe 3 O 4 composite nanofibrous adsorbent: comparison with chitosan/Al 2 O 3/Fe 3 O 4 beads. Int J Biol Macromol. 2016;93:557-565. 23. Li J, Lv G, Bai W, Liu Q, Zhang Y, Song J. Modification and use of
biochar from wheat straw (Triticum aestivum L.) for nitrate and phos-phate removal from water. Desalin Water Treat. 2016;57:4681-4693. 24. You X, Guaya D, Farran A, Valderrama C, Cortina JL. Phosphate
removal from aqueous solution using a hybrid impregnated polymeric sorbent containing hydrated ferric oxide (HFO). J Chem Technol Bio-technol. 2016;91:693-704.
25. Perreault F, Fonseca de Faria A, Elimelech M. Environmental applica-tions of graphene-based nanomaterials. Chem Soc Rev. 2015;44: 5861-5896. https://doi.org/10.1039/C5CS00021A.
26. Chen M, Huo C, Li Y, Wang J. Selective adsorption and efficient removal of phosphate from aqueous medium with graphene– lanthanum composite. ACS Sustain. Chem. Eng. 2016;4:1296-1302.
27. Wan Ibrahim WA, Rashidi Nodeh H, Sanagi MM. Graphene-based materials as solid phase extraction sorbent for trace metal ions, organic compounds, and biological sample preparation. Crit Rev Anal Chem. 2016;46:267-283. https://doi.org/10.1080/10408347.2015. 1034354.
28. Cui L, Xu W, Guo X, Zhang Y, Wei Q, Du B. Synthesis of strontium hydroxyapatite embedding ferroferric oxide nano-composite and its application in Pb2+ adsorption. J Mol Liq. 2014;197:40-47. https:// doi.org/10.1016/j.molliq.2014.04.027.
29. Lu A-H, Salabas EL, Schüth F. Magnetic nanoparticles: synthesis, pro-tection, functionalization, and application. Angew Chem Int Ed. 2007; 46:1222-1244. https://doi.org/10.1002/anie.200602866.
30. Mahmoudi E, Ng LY, Ba-Abbad MM, Mohammad AW. Novel nanohybrid polysulfone membrane embedded with silver nanoparticles on graphene oxide nanoplates. Chem Eng J. 2015;277:1-10. https://doi. org/10.1016/j.cej.2015.04.107.
31. Bahadır EB, Sezgintürk MK. Applications of graphene in electro-chemical sensing and biosensing. TrAC Trends Anal Chem. 2016;76: 1-14.
32. Sharma VK, McDonald TJ, Kim H, Garg VK. Magnetic graphene– carbon nanotube iron nanocomposites as adsorbents and antibacterial agents for water purification. Adv Colloid Interface Sci. 2015;225:229-240. https://doi.org/10.1016/j.cis.2015.10.006. 33. Rashidi Nodeh H, Sereshti H. Synthesis of magnetic graphene oxide
doped with strontium titanium trioxide nanoparticles as a nanocomposite for the removal of antibiotics from aqueous media. RSC Adv. 2016;6:89953-89965.
34. Shahabuddin S, Sarih NM, Afzal Kamboh M, Rashidi Nodeh H, Mohamad S. Synthesis of polyaniline coated graphene oxide@SrTiO3 nanocube nanocomposites for enhanced removal of carcinogenic dyes from aqueous solution. Polymers (Basel). 2016;8:305-310. https://doi.org/10.20944/preprints201608.0128.v1.
35. Kulkarni VM, Bodas D, Paknikar KM. Lanthanum strontium manga-nese oxide (LSMO) nanoparticles: a versatile platform for anticancer therapy. RSC Adv. 2015;5:60254-60263. https://doi.org/10.1039/ C5RA02731D.
36. Manikantan J, Ramalingam HB, Shekar BC, Murugan B, Kumar RR, Santhoshi JS. Wide band gap of strontium doped hafnium oxide nanoparticles for opto-electronic device applications—synthesis and characterization. Mater Lett. 2017;186:42-44. https://doi.org/10. 1016/j.matlet.2016.08.026.
37. Iqbal MJ, Ashiq MN. Physical and electrical properties of Zr–Cu substituted strontium hexaferrite nanoparticles synthesized by co-precipitation method. Chem Eng J. 2008;136:383-389. https://doi. org/10.1016/j.cej.2007.05.046.
38. Shahabuddin S, Muhamad Sarih N, Mohamad S, Joon Ching J. SrTiO3 Nanocube-doped polyaniline nanocomposites with enhanced photo-catalytic degradation of methylene blue under visible light. Polymers (Basel). 2016;8:27.
39. Kanazawa T, Lu D, Maeda K. Photochemical synthesis of Fe (III)–Cr (III) mixed oxide nanoparticles on strontium titanate powder and their application as water oxidation cocatalysts. Chem Lett. 2016;45: 967-969.
40. Sood S, Umar A, Mehta SK, Sinha ASK, Kansal SK. Efficient photo-catalytic degradation of brilliant green using Sr-doped TiO2 nanoparticles. Ceram Int. 2015;41 (3533-3540.
41. Roy E, Patra S, Madhuri R, Sharma PK. Europium doped magnetic graphene oxide-MWCNT nanohybrid for estimation and removal of arsenate and arsenite from real water samples. Chem Eng J. 2016; 299:244-254.
42. Rashidi Nodeh H, Sereshti H, Zamiri Afsharian E, Nouri N. Enhanced removal of phosphate and nitrate ions from aqueous media using nanosized lanthanum hydrous doped on magnetic graphene nanocomposite. J Environ Manage. 2017;197:265-274. https://doi. org/10.1016/j.jenvman.2017.04.004.
43. Salavati-Niasari M, Hosseinzadeh G, Davar F. Synthesis of lanthanum hydroxide and lanthanum oxide nanoparticles by sonochemical method. J Alloys Compd. 2011;509:4098-4103.
44. Hussain SK, Nagaraju G, Pavitra E, Raju GSR, Yu S. La(OH)3:Eu 3+ and La2O3:Eu3+ nanorod bundles: growth mechanism and lumines-cence properties. CrstEngComm. 2015;17:9431-9442.
45. NIST. NIST Standard Reference Data. National Institute of Standards and Technolnology: Gaithersburg, MD; 2016.
46. Granados-Correa F, Bonifacio-Martinez J, Serrano-Gomez J. Synthe-sis and characterization of calcium phosphate and its relation to Cr (VI) adsorption properties. Rev Int Contam Ambient. 2010;26: 129-134.
47. Roguska A, Pisarek M, Andrzejczuk M, Dolata M, Lewandowska M, Janik-Czachor M. Characterization of a calcium phosphate–TiO2 nanotube composite layer for biomedical applications. Mater Sci Eng C. 2011;31:906-914.
48. García-Ruiz C. Nitrocellulose in propellants: characteristics and ther-mal properties. In: Wythers MC, ed. Advances in Materials Science Research. Nova Science Publishers: New York, USA; 2012:202-220. 49. Tran DNH, Kabiri S, Wang L, Losic D. Engineered graphene–
nanoparticle aerogel composites for efficient removal of phosphate from water. J Mater Chem A. 2015;3:6844-6852.
50. Zhou K, Zhu Y, Yang X, Li C. One-pot preparation of graphene/ Fe3O4 composites by a solvothermal reaction. New J Chem. 2010;34: 2950-2955.
51. Mahpishanian S, Sereshti H, Baghdadi M. Superparamagnetic core-shells anchored onto graphene oxide grafted with phenylethyl amine as a nano-adsorbent for extraction and enrichment of organophos-phorus pesticides from fruit, vegetable and water samples. J Chromatogr A. 2015;1406:48-58. https://doi.org/10.1016/j.chroma. 2015.06.025.
52. Kamboh MA, Wan Ibrahim WA, Rashidi Nodeh H, Sanagi MM, Sherazi STH. The removal of organophosphorus pesticides from water using a new amino-substituted calixarene-based magnetic spo-ropollenin. New J Chem. 2016;40:3130-3138. https://doi.org/10. 1039/C5NJ02284C.
53. Khoshhesab ZM, Ayazi Z, Farrokhrouz Z. Ultrasound-assisted mixed hemimicelle magnetic solid phase extraction followed by high perfor-mance liquid chromatography for the quantification of atorvastatin in biological and aquatic samples. Anal Methods. 2016;8:4934-4940. 54. Mishra S, Yadav A, Verma N. Carbon gel-supported Fe-graphene
disks: synthesis, adsorption of aqueous Cr (VI) and Pb (II) and the removal mechanism. Chem Eng J. 2017;326:987-999.
55. Xing M, Xu L, Wang J. Mechanism of Co (II) adsorption by zero valent iron/graphene nanocomposite. J Hazard Mater. 2016;301:286-296. 56. Abbaszadeh S, Wan Alwi SR, Ghasemi N, Rashidi Nodeh H, Colin
Webb C, Muhamad II. Use of pristine papaya peel to remove Pb(II) from aqueous solution. Chem Eng Trans. 2015;45:961-966. 57. Bhatti AA, Kamboh MA, Solangi IB, Memon S. Synthesis of calix
[6] arene based XAD-4 material for the removal of reactive blue 19 from aqueous environments. J Appl Polym Sci. 2013;130:776-785. 58. Cantuaria ML, de Almeida Neto AF, Nascimento ES, Vieira MGA.
Adsorption of silver from aqueous solution onto pre-treated benton-ite clay: complete batch system evaluation. J Clean Prod. 2016;112: 1112-1121.
59. Kannan N, Sundaram MM. Kinetics and mechanism of removal of methylene blue by adsorption on various carbons—a comparative study. Dye Pigment. 2001;51:25-40.
60. Fu J, Chen Z, Wang M, et al. Adsorption of methylene blue by a high-efficiency adsorbent (polydopamine microspheres): kinetics, isotherm, thermodynamics and mechanism analysis. Chem Eng J. 2015;259:53-61. https://doi.org/10.1016/j.cej.2014.07.101.
61. Shrestha S, Son G, Lee SH, Lee TG. Isotherm and thermodynamic studies of Zn (II) adsorption on lignite and coconut shell-based acti-vated carbon fiber. Chemosphere. 2013;92:1053-1061.
62. Cechinel MAP, de Souza AAU. Study of lead (II) adsorption onto acti-vated carbon originating from cow bone. J Clean Prod. 2014;65: 342-349.
63. Ismail NA, Bakhshaei S, Kamboh MA, Abdul Manan NS, Mohamad S, Yilmaz M. Adsorption of phenols from contaminated water through titania-silica mixed imidazolium based ionic liquid: equilibrium, kinetic and thermodynamic modeling studies. J Macromol Sci Part A. 2016; 53:619-628.
64. Saygılı H, Güzel F. High surface area mesoporous activated carbon from tomato processing solid waste by zinc chloride activation: pro-cess optimization, characterization and dyes adsorption. J Clean Prod. 2016;113:995-1004.
65. Mahmoud ME, Nabil GM, El-Mallah NM, Bassiouny HI, Kumar S, Abdel-Fattah TM. Kinetics, isotherm, and thermodynamic studies of the adsorption of reactive red 195 A dye from water by modified Switchgrass Biochar adsorbent. J. Ind. Eng. Chem. 2016;37:156-167. 66. Maszkowska J, Wagil M, Mioduszewska K, Kumirska J, Stepnowski P,
Białk-Bielinska A. Thermodynamic studies for adsorption of ionizable pharmaceuticals onto soil. Chemosphere. 2014;111:568-574. 67. Demiral H, Güngör C. Adsorption of copper (II) from aqueous
solu-tions on activated carbon prepared from grape bagasse. J Clean Prod. 2016;124:103-113.
68. Rashidi Nodeh H, Wan Ibrahim WA, Ali I, Sanagi MM. Development of magnetic graphene oxide adsorbent for the removal and preconcentration of As(III) and As(V) species from environmental water samples. Environ Sci Pollut Res. 2016;23:9759-9773. https:// doi.org/10.1007/s11356-016-6137-z.
69. Liu W, Yin P, Liu X, Dong X, Zhang J, Xu Q. Thermodynamics, kinetics, and isotherms studies for gold (III) adsorption using silica functionalized by diethylenetriaminemethylenephosphonic acid. Chem Eng Res Des. 2013;91:2748-2758.
70. Lee K-Y, Park M, Kim J, et al. Equilibrium, kinetic and thermodynamic study of cesium adsorption onto nanocrystalline mordenite from high-salt solution. Chemosphere. 2016;150:765-771.
71. Yan L, Yang K, Shan R, et al. Kinetic, isotherm and thermodynamic inves-tigations of phosphate adsorption onto core-shell Fe3O4@LDHs com-posites with easy magnetic separation assistance. J Colloid Interface Sci. 2015;448:508-516. https://doi.org/10.1016/j.jcis.2015.02.048. 72. Zhang Y, Guo X, Wu F, et al. Mesocarbon microbead
carbon-supported magnesium hydroxide nanoparticles: turning spent Li-ion battery anode into a highly efficient phosphate adsorbent for waste-water treatment. ACS Appl Mater Interfaces. 2016;8:21315-21325. https://doi.org/10.1021/acsami.6b05458.
73. Kilpimaa S, Runtti H, Kangas T, Lassi U, Kuokkanen T. Journal of industrial and engineering chemistry physical activation of carbon res-idue from biomass gasification: novel sorbent for the removal of phosphates and nitrates from aqueous solution. Korean Soc Ind Eng Chem. 2014;21:1-11. https://doi.org/10.1016/j.jiec.2014.06.006. 74. Jiang H, Chen P, Luo S, Tu X, Cao Q, Shu M. Synthesis of novel
nanocomposite Fe3O4/ZrO2/chitosan and its application for removal of nitrate and phosphate. Appl Surf Sci. 2013;284:2-9. https://doi. org/10.1016/j.apsusc.2013.04.013.
How to cite this article: Sereshti H, Zamiri Afsharian E, Esmaeili Bidhendi M, Rashidi Nodeh H, Afzal Kamboh M, Yilmaz M. Removal of phosphate and nitrate ions aqueous using strontium magnetic graphene oxide nanocomposite: Isotherms, kinetics, and thermodynamics studies. Environ Prog Sustainable Energy. 2020;39:e13332.https://doi.org/10.1002/ ep.13332
