Binary Oxide Adsorbent Research Articles

Efficient removal of antimonate and antimonite by a novel lanthanum-manganese binary oxide: Performance and mechanism.

Antimony is a highly toxic pollutant and its removal from water gains increasing attention. To effectively remove both Sb(III) and Sb(V), a novel lanthanum-manganese binary oxide (L1M2BO) adsorbent was synthesized by a simple oxidation coupled with precipitation method. The as-prepared L1M2BO was detailedly characterized by the XRD, SEM, TEM, BET, FTIR and XPS techniques. It is amorphous and irregular in shape, with a particle size of 50-100nm and a specific surface area of 180.4m2/g. A remarkable synergistic effect between the lanthanum hydroxide and Mn oxide in improving antimony adsorption is shown. The maximum adsorption capacities of Sb(III) and Sb(V) are 364.6mg/g and 131.1mg/g at pH 7.0, respectively, which outcompete most of reported adsorbents. The adsorption behaviors of antimony fitted well the pseudo-second-order kinetic and Freundlich models. The adsorption mechanism of Sb(V) involves mainly the replacement of surface metal hydroxyl and forming inner-sphere complex. While the Sb(III) removal is a more complicated process, containing both Sb(III) adsorption and oxidation to Sb(V). Furthermore, the spent L1M2BO sorbent can be regenerated and reused. The L1M2BO could be used as an attractive adsorbent for antimony removal, owing to its easily fabrication, high effectiveness and reusability.

Adsorption performance and its mechanism of aqueous As(III) on polyporous calcined oyster shell-supported Fe-Mn binary oxide.

Fe-Mn binary oxide (FMBO) is a promising adsorbent for As(III) removal through combined adsorption and oxidation. The calcined oyster shell-supported Fe-Mn binary oxide (FMBO/OS) adsorbent was synthesized by the co-precipitation method. Results indicated that the calcined oyster shell, as a carrier, improved the stability of FMBO and its adsorption capacity for As(III). The maximum adsorption capacity of FMBO/OS on As(III) reached 140.5mg·g-1 . Under pH5.0 and 25°C, the removal efficiency of FMBO/OS to As(III) solution (C0 = 10mg·L-1 ) reached 87% within 12 h. Moreover, based on the characterization analyses, the removal mechanisms of As(III) were deduced to include the combined adsorption and oxidation process of FMBO and the synergistic effect of oyster shells. This work provides new insights into synthesizing efficient and green adsorbents to remove aqueous As(III). Meanwhile, it provides technical support for reusing waste biomass materials such as the oyster shell. PRACTITIONER POINTS: FMBO/OS was prepared by a simple hydrothermal co-precipitation method. The carrier alleviates the agglomeration of Fe-Mn oxides. The adsorbent shows a strong adsorption capacity of As(III) and good selectivity. The good results benefit from the synergistic effect of calcium arsenate generation. The prepared adsorbent can adsorb arsenic in real samples.

The preparation of a novel iron/manganese binary oxide for the efficient removal of hexavalent chromium [Cr(vi)] from aqueous solutions

To remove hexavalent chromium Cr(vi) efficiently, a novel Fe–Mn binary oxide adsorbent was prepared via a “two-step method” combined with a co-precipitation method and hydrothermal method. The as-prepared Fe–Mn binary oxide absorbent was characterized via transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectra (FTIR), thermogravimetric analysis (TGA), zeta potential, BET and X-ray photoelectron spectroscopy (XPS). The results indicated that the morphology of the adsorbent was rod-like with length of about 100 nm and width of about 50–60 nm, specific surface area was 63.297 m2 g−1, has the composition of α-Fe2O3, β-MnO2 and MnFe2O4 and isoelectric point was observed at pH value of 4.81. The removal of Cr(vi) was chosen as a model reaction to evaluate the adsorption capacity of the Fe–Mn binary oxide adsorbent, indicating that the Fe–Mn binary oxide adsorbent showed high adsorption performance (removal rate = 99%) and excellent adsorption stability (removal rate > 90% after six rounds of adsorption). The adsorption behavior of the Fe–Mn binary oxide was better represented by the Freundlich model (adsorption isotherm) and the pseudo-second-order model (adsorption kinetic), suggesting that the adsorption process was multi-molecular layer chemical adsorption. The possible adsorption mechanism of the Fe–Mn binary oxide for the removal of Cr(vi) included the protonation process and the electrostatic attraction interactions.

Development study of Diffusive Gradient in Thin Film (DGT) method with binding agent Fe−Ca complex for phosphate measurement

The inclusion of phosphorus as a phosphate compound into the aquatic system causes environmental problems, for which monitoring is required in particular on waste treatment. The Diffusive Gradient in Thin Film (DGT) technique with ferrihydrite as binding gel is commonly used for in situ phosphate measurement. Studies on Fe−Mn binary oxide adsorbent have been performed but are only able to absorb phosphate optimally at pH 3−5. In addition to ferric salts, calcium salt is an effective chemical reagent in absorbing phosphate. This research develops new technology by combining both reagent into Fe−Ca complex. The result of this study show that Fe−Ca complex has an antagonistic effect in absorbing phosphate at molar ratio of Fe−Ca 1: 1.5 to 1: 5 and has a synergistic effect when the molar ratio of Fe is increased from 1: 1 to 5: 1. The Optimum absorption occurs in the molar ratio of Fe−Ca complex 3: 1. The measurement of phosphate by spectrophotometric method of molybdenum blue known that Fe−Ca complex has wide working area that is in pH range 2.0−10.0 with optimum contact time 24 hours. Based on the results obtained Fe−Ca complex can be one alternative binding gel on phosphate measurement with DGT technique.

Presence of Fe-Al binary oxide adsorbent cake layer in ceramic membrane filtration and their impact for removal of HA and BSA

To enhance the removal of natural organic matter (NOM) in ceramic (Ce) membrane filtration, an iron-aluminum binary oxide (FAO) was applied to the ceramic membrane surface as the adsorbent cake layer, and it was compared with heated aluminum oxide (HAO) for the evaluation of the control of NOM. Both the HAO and FAO adsorbent cake layers efficiently removed the NOM regardless of NOM's hydrophobic/hydrophilic characteristics, and the dissolved organic carbon (DOC) removal in NOM for FAO was 1–1.12 times greater than that for HAO, which means FAO was more efficient in the removal of DOC in NOM. FAO (0.03 μm), which is smaller in size than HAO (0.4 μm), had greater flux reduction than HAO. The flux reduction increased as the filtration proceeded because most of the organic foulants (colloid/particles and soluble NOM) were captured by the adsorbent cake layer, which caused fouling between the membrane surface and the adsorbent cake layer. However, no chemically irreversible fouling was observed on the Ce membrane at the end of the FAO adsorbent cake layer filtration. This means that a stable adsorbent cake layer by FAO formed on the Ce membrane, and that the reduced pure water flux of the Ce membrane, resulting from the NOM fouling, can easily be recovered through physicochemical cleaning.

Removal of tungsten from molybdate solution by Fe–Mn binary oxide adsorbent

Abstract Considering the different geochemical enrichment behaviors of W and Mo, Fe–Mn binary oxide (FMBO), ferric hydroxide (Fe(OH)3) and manganese dioxide (MnO2) were studied to separate W from molybdate solution, respectively. The experimental results demonstrated that Fe–Mn binary oxide (FMBO) was the most suitable adsorbent for the separation. Under a wide pH (6.9–11.3) region, more than 80%W removal efficiency and less than 3%Mo loss could be obtained. In addition, the Fe–Mn binary oxide adsorbent can be regenerated by treating with 3 mol/L NaOH, and the W adsorption efficiency was retained after five adsorption–desorption–regeneration cycles. All these indicate that the Fe–Mn binary oxides have the potential for the separation of W from molybdate solution.

Enhanced fluoride removal performance by Ce–Zn binary metal oxide: Adsorption characteristics and mechanism

Excess fluoride in water can result in serious health problems. For this reason, we have developed a novel Ce–Zn binary metal oxide (Ce–Zn BMO) adsorbent for high-performance fluoride adsorption from drinking water. The Fourier transform infrared spectroscopy (FTIR) and X–ray photoelectron spectroscopy (XPS) results demonstrated both electrostatic interactions and ion exchange of surface hydroxyl groups of Ce–Zn BMO with fluoride ions. The Ce–Zn BMO adsorbent exhibited a good Langmuir adsorption capacity of 194mg/g at pH 7.0. The adsorbent has a wide pH range (3–7) applicability and negligible coexisting ion effect that makes it an attractive sustainable material for field applications. Column adsorption studies indicated the efficient treatable volume as ∼94-bed volume (BV) using natural water when the breakthrough point in the column was 1.5mg/L. Furthermore, six cycles reusability without much loss of adsorption capacity and effective column treatment of fluoride contaminated water indicated that Ce–Zn BMO could be developed into an efficient technology for high performance elevated fluoride water treatment.

Highly efficient removal of phosphate using a novel Fe-La binary (hydro) oxide as adsorbent: behavior and mechanism

Phosphate has been proved to be one of the main elements causing eutrophication of water bodies. However, the elevated phosphate concentrations in the water bodies are often due to the excess discharge of wastewater containing phosphate. Therefore, treatment of elevated phosphate-containing wastewater is of vital importance to alleviate the situation. In this study, a novel Fe-La binary (hydro) oxide adsorbent was synthesized via a facile coprecipitation method for effective phosphate removal from wastewater. The adsorbent grains were formed of primary nanoparticles. Batch experiments were carried out to investigate adsorption kinetics and equilibrium. The adsorption was fast and well fitted by the pseudo-second-order equation, indicating that the adsorption process might be chemical sorption. The adsorption isotherms could be well described by Freundlich model and the maximal adsorption capacity reached 80.7 mg/g at pH 6.0 +/- 0.1 and 67.4 mg/g at pH 9.0 +/- 0.1, respectively, much higher than many reported adsorbents. The phosphate adsorption was pH dependent and weakly acidic condition was favorable for the adsorption. The phosphatead sorption might be mainly achieved via the replacement of surface hydroxyl groups at the solid surface and the formation of inner-sphere surface complexes. Moreover, the spent adsorbent could be effectively regenerated using dilute NaOH solution and used repeatedly. All these results suggest that the adsorbent maybe a promising alternative for phosphate removal.

Fluoride removal from aqueous solution by Al(III)–Zr(IV) binary oxide adsorbent

In this study, a novel binary oxide adsorbent of Al2O3–ZrO2 was prepared via coprecipitation followed by calcination method, and the calcination temperatures were investigated. The adsorbent was characterized by XRD, EDX and XPS. The batch adsorption experiments were carried out at different parameters, such as solution pH, adsorbent dose, contact time, initial fluoride concentration and adsorption temperature, to evaluate the fluoride removal performance. The results showed that the adsorption isotherm was better described by the linear Langmuir model, and a maximum adsorption capacity was 114.54mg/g. The adsorption kinetics was well fitted by the linear pseudo-second-order, and the correlation coefficient value (R2) was 0.997. The thermodynamic parameters of ΔH0, ΔS0 and ΔG0 were calculated, which showed that the fluoride adsorption process was spontaneous and exothermic. And the possible adsorption mechanism of the adsorbent for fluoride could involve the ligand-exchange and ion-exchange based on the results in the study.

Removal behavior and mechanism of Co(II) on the surface of Fe–Mn binary oxide adsorbent

Abstract An amorphous Fe–Mn binary oxide adsorbent was developed using simultaneous oxidation and coprecipitation, and characterized by Brunauer–Emmett–Teller analysis, X-ray diffractometry, scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The removal behavior of the prepared absorbent for cobalt (II) was studied. Results showed that iron and manganese in adsorbent existed mainly in the +III and +IV oxidation states, respectively. The adsorbent exhibited the best depletion of Co(II) at pH 6–8, and the best removal ability at an ionic strength of 0.01 mmol L−1. The Freundlich isotherm model fitted the Co(II) adsorption data best. The FTIR spectra of the absorbent before and after Co(II) adsorption showed that the surface hydroxyl groups, Mn–OH and Fe–OH, existed at the surface and formed Mn–O–Co or Fe–O–Co. The iron oxide was the main adsorbent, and the manganese oxide also showed adsorption and oxidation ability. The XPS spectra confirmed that the Mn in the absorbent was reduced whereas the Fe showed no difference after reaction with Co(II). The XPS measurements of cobalt adsorbed on the adsorbent indicate that Co(II) has been oxidized to Co(III).

A comprehensive study of Cd(II) ions removal utilizing high-surface-area binary Mg–Si hybrid oxide adsorbent

Presented work concerns the application of synthetic oxide adsorbent in the removal of cadmium ions from its model, water solutions. In this study, a novel magnesium–silicon (Mg–Si) binary oxide adsorbent was prepared by a modified co-precipitation method, utilizing sodium silicate and magnesium sulphate solutions as precursors of silica and magnesium oxide, respectively. The material was thoroughly characterized in order to evaluate chemical composition (AAS, EDS and gravimetric method), crystalline structure (XRD), morphology (SEM), particle size distribution (DLS), characteristic functional groups (FTIR) and porous structure parameters (BET and BJH models). It was proved that the adsorbent is amorphous, with a micrometric-sized, irregular-shaped particles and relatively large surface area of 540 m2/g. Batch adsorption experiments were conducted to investigate the adsorption of Cd(II) ions on the prepared adsorbent, including evaluation of adsorption kinetics, the intraparticle diffusion model, the effect of pH, contact time, mass of the adsorbent, temperature and the effect of competitive Cl− and NO3 − anions. During the study, it was confirmed that the adsorption of Cd(II) ions reached equilibrium within 30 min, which was found to fit well with a pseudo-second-order kinetic model type 1 (r 2 = 0.998–0.999). The Mg–Si adsorbent exhibited high adsorption capacity for Cd(II) ions at pH above 7, and the maximum quantity of cadmium(II) ions adsorbed in optimal time was achieved for the highest metal ion concentrations: 18.22 (Cl−) and 15.46 (NO3 −) mg/g. The competitive anions present in the model cadmium salt solutions hindered adsorption in the sequence Cl−>NO3 −.

Preparation of Mn-Fe Binary Oxide for Arsenic Removal from Aqueous Solution

Adsorption removal of arsenic from contaminated drinking water was carried out by using Mn-Fe binary oxide adsorbent. Main phase of adsorbents was influenced by pH value of solution, and pH of 10 is the suitable synthesis condition to achieve the Mn-Fe binary oxide suspension adsorbents. Adsorbents with Mn/Fe mole ratio from 6/4 to 2/8 exhibits higher arsenite removal larger than 99.6%.

Antimony(V) removal from water by iron-zirconium bimetal oxide: Performance and mechanism

A Fe-Zr binary oxide adsorbent has been successfully synthesized using a co-precipitation method. It showed a better performance for antimonate (Sb(V)) removal than zirconium oxide or amorphous ferric oxide. The experimental results showed that the Fe-Zr adsorbent has a capacity of 51 mg/g at an initial Sb(V) concentration of 10 mg/L at pH 7.0. Sb(V) adsorption on the Fe-Zr bimetal oxide is normally an endothermic reaction. Most of the Sb(V) adsorption took place within 3 hr and followed a pseudo second-order rate law. Co-existing anions such as SO42−, NO3− and Cl− had no considerable effects on the Sb(V) removal; PO43− had an inhibitory effect to some extent at high concentration; while CO32− and SiO44− showed significant inhibitory effects when they existed in high concentrations. The mechanism of Sb(V) adsorption on the adsorbent was investigated using a combination of zeta potential measurements, XPS, Raman, FT-IR observations and SO42− release determination. The ionic strength dependence and zeta potential measurements indicated that inner-sphere surface complexes were formed after Sb(V) adsorption. Raman and XPS observations demonstrated that both Fe-OH and Zr-OH sites at the surface of the Fe-Zr adsorbent play important roles in the Sb(V) adsorption. FT-IR characterization and SO42− release determination further demonstrated that the exchange of SO42− with Sb(V) also could promote the adsorption process. In conclusion, this adsorbent showed high potential for future application in Sb(V) removal from contaminated water.

Co(II) Adsorption in Aqueous Media by a Synthetic Fe–Mn Binary Oxide Adsorbent

Co(II) adsorption on high-purity amorphous Fe–Mn binary oxide adsorbent was investigated. The Co(II) adsorption behavior of this synthetic material was studied and discussed as a function of contact time, pH and initial concentration. The Langmuir and Freundlich isotherm models were applied to fit the Co(II) adsorption data on Fe–Mn binary oxide with mesoporous particles of irregular surface morphology and a specific surface area of 201.8 m2 g−1 with a maximum capacity of 32.25 mg g−1. Various kinetic models applied to the adsorption rate data of the Co(II) ion were evaluated. The results show that the pseudo-second order and the intra-particle mass transfer diffusion models correlated best with the experimental rate data. The adsorption activation energy was found to be 9.07 kJ mol−1 indicating that it corresponds to a physical adsorption. The evaluated thermodynamics parameters of the adsorption values indicated the endothermic and spontaneous nature of the adsorption. The results obtained confirmed that Fe–Mn binary oxide had the potential to be utilized as a low-cost and relatively effective adsorbent for Co(II) removal from wastewater.

Removal of phosphate from aqueous solution by magnetic Fe–Zr binary oxide

Phosphorus removal was a crucial aspect in controlling eutrophication problem of water pollution. Zirconium oxide was a suitable adsorbent for phosphate removal due to its good adsorption efficiency, but it suffered from the separation inconvenience. In this paper, magnetic Fe–Zr binary oxide was synthesized and used as adsorbent for removing phosphate from aqueous solution. The adsorbent was characterized by energy dispersive analysis system of X-ray, scanning electron microscopy (SEM), infrared spectrum (IR), X-ray powder diffraction (XRD) analysis and BET surface area measurements. The results showed that kinetic data followed a pseudo-second-order model and equilibrium data were well fitted by the Langmuir model. The maximum adsorption capacity was 13.65mg P/g at pH 4. The adsorption mechanism was mainly derived from ion-exchange of zirconium species and partly originated from magnetite species of Fe–Zr binary oxide. The main advantages of magnetic Fe–Zr binary oxide adsorbent consisted in its separation convenience and highly efficient reusability compared to the other adsorbents.

Adsorptive removal of arsenic from water by an iron–zirconium binary oxide adsorbent

Arsenate and arsenite may exist simultaneously in groundwater and have led to a greater risk to human health. In this study, an iron–zirconium (Fe–Zr) binary oxide adsorbent for both arsenate and arsenite removal was prepared by a coprecipitation method. The adsorbent was amorphous with a specific surface area of 339 m 2/g. It was effective for both As(V) and As(III) removal; the maximum adsorption capacities were 46.1 and 120.0 mg/g at pH 7.0, respectively, much higher than for many reported adsorbents. Both As(V) and As(III) adsorption occurred rapidly and achieved equilibrium within 25 h, which were well fitted by the pseudo-second-order equation. Competitive anions hindered the sorption according to the sequence PO 4 3 - > SiO 3 2 - > CO 3 2 - > SO 4 2 - . The ionic strength effect experiment, measurement of zeta potential, and FTIR study indicate that As(V) forms inner-sphere surface complexes, while As(III) forms both inner- and outer-sphere surface complexes at the water/Fe–Zr binary oxide interface. The high uptake capability and good stability of the Fe–Zr binary oxide make it a potentially attractive adsorbent for the removal of both As(V) and As(III) from water.

Benzotriazole removal from water by Zn–Al–O binary metal oxide adsorbent: Behavior, kinetics and mechanism

In this study, a novel Zn–Al–O binary metal oxide adsorbent was prepared and used to remove the emerging polar contaminant benzotriazole from water. The adsorption behavior, kinetics and mechanism were systemically studied. Results showed that benzotriazole was rapidly and effectively adsorbed by the adsorbent. Instantaneous adsorption was observed under each studied condition, and the adsorption reached equilibrium within 30min. High initial benzotriazole concentration enhanced the adsorption. The amount of absorbed benzotriazole increased with increasing adsorbent dosage, but decreased with increasing ionic strength. Solution pH had little effect on benzotriazole adsorption. The adsorption isotherm was consistent with S-type. Langmuir isotherm model fitted the equilibrium data better than Freundlich, Dubinin–Radushkevich and Temkin isotherm models. The maximum monolayer adsorptive capacity of benzotriazole with and without electrolytes was 7.30mgg−1 and 9.51mgg−1, respectively. Elovich and pseudo-second-order models were most suitable for describing the adsorption kinetics. Interactions between the surface sites of the adsorbent and benzotriazole may be a combination of electrostatic interaction, ion exchange and hydrogen bond.

Removal of phosphate from water by a Fe–Mn binary oxide adsorbent

Phosphate removal is important in the control of eutrophication of water bodies and adsorption is one of the promising approaches for this purpose. A Fe–Mn binary oxide adsorbent with a Fe/Mn molar ratio of 6:1 for phosphate removal was synthesized by a simultaneous oxidation and coprecipitation process. Laboratory experiments were carried out to investigate adsorption kinetics and equilibrium, in batch mode. The effects of different experimental parameters, namely contact time, initial phosphate concentration, solution pH, and ionic strength on the phosphate adsorption were investigated. The adsorption data were analyzed by both Freundlich and Langmuir isotherm models and the data were well fit by the Freundlich isotherm model. Kinetic data correlated well with the pseudo-second-order kinetic model, suggesting that the adsorption process might be chemical sorption. The maximal adsorption capacity was 36 mg/g at pH 5.6. The phosphate adsorption was highly pH dependent. The effects of anions such as Cl - , SO 4 2 - , and CO 3 2 - on phosphate removal were also investigated. The results suggest that the presence of these ions had no significant effect on phosphate removal. The phosphate removal was mainly achieved by the replacement of surface hydroxyl groups by the phosphate species and formation of inner-sphere surface complexes at the water/oxide interface. In addition, the adsorbed phosphate ions can be effectively desorbed by dilute NaOH solutions. This adsorbent, with large adsorption capacity and high selectivity, is therefore a very promising adsorbent for the removal of phosphate ions from aqueous solutions.

Adsorption behavior and mechanism of arsenate at Fe–Mn binary oxide/water interface

Preliminary study revealed that a prepared Fe–Mn binary oxide adsorbent with a Fe:Mn molar ratio of 3:1 was more effective for As(V) removal than pure amorphous FeOOH, which was unanticipated. In this paper, the As(V) adsorption capacities of Fe–Mn binary oxide and amorphous FeOOH were compared in detail. Furthermore, the adsorption behaviors as well as adsorption mechanism of As(V) at the Fe–Mn binary oxide/water interface were investigated. The higher uptake of As(V) by the Fe–Mn binary oxide may be due to its higher surface area (265 m 2/g) and pore volume (0.47 cm 3/g) than those of amorphous FeOOH. The As(V) adsorption process on the Fe–Mn binary oxide is endothermic and the increase of temperature is favoring its adsorption. A slight increase in the As(V) adsorption was observed with increasing ionic strength of the solution, which indicated that As(V) anions might form inner-sphere surface complexes at the oxide/water interface. The Zeta potential along with FTIR analysis confirmed further the formation of inner-sphere surface complexes between As(V) anions and the surface of Fe–Mn binary oxide. In addition, the influences of coexisting ions such as phosphate, bicarbonate, silicate, sulfate, chloride, calcium and magnesium which are generally present in groundwater on As(V) adsorption were examined. Among the tested anions, chloride and sulfate had no significant effect on As(V) removal, silicate decreased obviously the As(V) removal, while phosphate caused the greatest percentage decrease in As(V) adsorption. On the contrary, the presence of cations of Ca 2+ and Mg 2+ enhanced the adsorption of As(V).

Removal Mechanism of As(III) by a Novel Fe−Mn Binary Oxide Adsorbent: Oxidation and Sorption

A novel Fe-Mn binary oxide adsorbent was developed for effective As(III) removal, which is more difficult to remove from drinking water and much more toxic to humans than As(V). The synthetic adsorbent showed a significantly higher As(III) uptake than As(V). The mechanism study is therefore necessary for interpreting such result and understanding the As(III) removal process. A control experiment was conducted to investigate the effect of Na2SO3-treatment on arsenic removal, which can provide useful information on As(III) removal mechanism. The adsorbent was first treated by Na2SO3, which can lower its oxidizing capacity by reductive dissolution of the Mn oxide and then reacted with As(V) or As(III). The results showed that the As(V) uptake was enhanced while the As(III) removal was inhibited after the pretreatment, indicating the important role of manganese dioxide during the As(III) removal. FTIR along with XPS was used to analyze the surface change of the original Fe-Mn adsorbent and the pretreated adsorbent before and after reaction with As(V) or As(III). Change in characteristic surface hydroxyl groups (Fe-OH, 1130, 1048, and 973 cm(-1)) was observed by the FTIR. The determination of arsenic oxidation state on the solid surface after reaction with As(III) revealed that the manganese dioxide instead of the iron oxide oxidized As(III) to As(V). The iron oxide was dominant for adsorbing the formed As(V). An oxidation and sorption mechanism for As(III) removal was developed. The relatively higher As(III) uptake may be attributed to the formation of fresh adsorption sites at the solid surface during As(III) oxidation.