The oxidation of Fe(II) with Cu(II) in acidic sulfate solutions with air at elevated pressures

The oxidation of ferrous ions in acidic sulfate solutions in the presence of cupric ions at elevated air pressures was investigated in a high-intensity gas–liquid contactor. The study was required for the design of the regeneration steps of the novel Vitrisol^® desulphurization process. The effects of the Fe²⁺ concentration, Cu²⁺ concentration, Fe³⁺ concentration, initial H₂SO₄ concentration, and partial oxygen pressure on the reaction rate were determined at three different temperatures, i.e., T?=?50?°C, 70?°C, and 90?°C. Most of the experiments were determined to be affected by the mass transfer of oxygen, and therefore true intrinsic kinetics could not be fully determined. An increase in Fe²⁺ and Cu²⁺ concentrations, as well as the partial pressure of oxygen and temperature, increased the Fe²⁺ oxidation rate. H₂SO₄ did not influence the Fe²⁺ oxidation rate. An increase in Fe³⁺ concentration decreased the Fe²⁺ oxidation rate. Although determined from experiments partially affected by mass transfer, a first order of reaction in Fe²⁺ was observed, fractional orders in both Cu²⁺ and O₂ were measured, a zero order in H₂SO₄ was determined, and a negative, fractional order in Fe³⁺ was obtained. The activation energy was estimated to be 31.3?kJ/mol.     

Fenton-driven regeneration of MTBE-spent granular activated carbon—Effects of particle size and iron amendment procedures

Fenton-driven regeneration of spent granular activated carbon (GAC) can be used to regenerate organic contaminant-spent GAC. In this study, the effects of GAC particle size (>2 mm to <0.35 mm) and acid pre-treatment of GAC on Fenton-driven oxidation of methyl-tert-butyl ether (MTBE)-spent GAC were evaluated. Iron (Fe) was amended to the GAC using two methods: (1) untreated—where GAC was amended with a concentrated solution of ferrous sulfate and (2) acid pre-treatment—where GAC was amended with acid followed by sequential applications of a dilute ferrous sulfate solution. Subsequently, MTBE was amended to the GAC, followed by oxidative treatments with H₂O₂. H₂O₂ reaction and MTBE oxidation were inversely correlated with GAC particle size and were attributed to shorter intraparticle diffusion transport distances for both H₂O₂ and MTBE. Image analysis of the GAC cross-sections (i.e., prepared thin sections) revealed that the Fe amended to the GAC extended to the center of the GAC particles. Fe accumulated at higher levels on the periphery of the untreated GAC but Fe dispersal was more uniform in the acid pre-treated GAC. In the acid pre-treated GAC, conditions for MTBE oxidation were favorable and greater levels of MTBE oxidation were measured for all particle size fractions tested. Modeling and critical analysis of H₂O₂ diffusive transport and reaction indicated limited H₂O₂ penetration into large GAC particles which contributed to a decline in MTBE removal. Residual MTBE remaining on the GAC limited the quantity of MTBE that could be re-adsorbed, but no reduction in MTBE sorption capacity resulted from oxidative treatments.     

Wet oxidation of acetic acid by H2O2 catalyzed by transition metal-exchanged NaY zeolites

During the wet oxidation of contaminated wastewaters, the destruction of low molecular weight carboxylic acid intermediates such as acetic, glyoxalic, and oxalic acids is often the rate-controlling step. Oxidation of acetic acid, a very recalcitrant intermediate, requires compelling treatment severity. Heterogeneous catalytic wet oxidation of model acetic acid aqueous solutions was conducted under mild conditions (below the normal boiling point of water) using hydrogen peroxide over various transition metal-exchanged NaY zeolites. Treatment of Cu²⁺–NaY with oxalic acid [OA] led to a catalyst, Cu²⁺–NaY [OA], with significantly improved properties in terms of total organic carbon (TOC) removal efficiency and catalyst stability against leaching. This catalyst outperformed homogeneous Cu²⁺ by a factor of 2–2·5 times. Continuous feeding of H₂O₂ reduced its undesirable decomposition. Improvement of the TOC-degradation performance by Cu²⁺–NaY [OA] was tentatively attributed to the removal of sodium and possibly aluminium in the zeolite. © 1998 Society of Chemical Industry     

Removal of ampicillin sodium in solution using activated carbon adsorption integrated with H2O2 oxidation

BACKGROUND: The removal of antibiotic ampicillin sodium using H₂O₂ and modified granular activated carbon (GAC) is discussed. Two types of modified activated carbons were used in experiment to catalyze ·OH production from H₂O₂. One was modified with base (NaOH; called B‐GAC), the other was modified with Fe(NO₃)₃ (Fe‐GAC) and the nominal Fe metal loading was 5 wt%. In the experiment, pH, contact time, dosage of activated carbon and H₂O₂ and initial concentration of ampicillin sodium were investigated to determine their influence on the removal efficiency. The stability of Fe‐GAC was also evaluated. RESULTS: With an initial ampicillin sodium concentration of 200 mg L^?1, 85.2% of chemical oxygen demand (COD) and 76.4% of total organic carbon (TOC) can be removed with 8.0 g L^?1 of B‐GAC and 80 mg L^?1 of H₂O₂ (at pH 5.0). For the Fe‐GAC/H₂O₂ process, with 5.0 g L^?1 of activated carbon and 80 mg L^?1 of H₂O₂, COD and TOC removal can be elevated to 91.2% and 79.5% (at pH 3.0), respectively. CONCLUSION: The integration of activated carbon and H₂O₂ treatment was more effective for the removal of ampicillin from aqueous solution than using activated carbon alone. In the process, adsorption played a dominant role and the addition of a small amount of H₂O₂ accelerated the reaction rate and improved the removal efficiency. pH also greatly affected removal efficiency. Copyright © 2011 Society of Chemical Industry     

Degradation Effect and Mechanism of Dinitrotoluene Wastewater by Magnetic Nano-Fe3O4/H2O2 Fenton-like

The characteristics and influencing factors for dinitrotoluene degradation by nano-Fe₃O₄-H₂O₂ were studied, and the nano-scale Fe₃O₄ catalyst was prepared by the coprecipitation method, with dinitrotoluene wastewater as the degradation object. The results showed that the catalytic reaction system within the pH value range of 1 to 9 could effectively degrade dinitrotoluene, and the optimal pH value was 3; with the increase of catalyst dosage, the degradation efficiency and the catalytic reaction rate of dinitrotoluene grew as well. The optimal catalyst dosage was 1.0 g/L when the H₂O₂ dosage was within the range of 0 to 0.8 mL/L; the degradation efficiency and reaction rate grew with the increase of H₂O₂ dosage. With further increase of H₂O₂ dosage, degradation efficiency and reaction rate decreased; under the best conditions with the H₂O₂ dosage of 0.8 mL/L, the catalyst concentration of 1 g/L and the pH value of 3 at room temperature (25 °C), the degradation rate of the 100-mg/L dinitrotoluene in 120 min reached 97.6%. Through the use of the probe compounds n-butyl alcohol and benzoquinone, it was proved that the oxidation activity species in the nano-Fe₃O₄-H₂O₂ catalytic system were mainly hydroxyl radical (?OH) and superoxide radicals (HO2 ?), based on which, the reaction mechanism was hypothesized.     

Basic rules of NO oxidation by Fe2+/H2O2/AA directional decomposition system

Basic rules of NO oxidation by a Fe²⁺/H₂O₂/AA directional decomposition system were researched based on the technical background of flue gas NO_x removal. Effects of gas‐liquid interfacial area, main gas, and solution parameters on NO oxidation efficiency (η) were analyzed. The results showed that adequate contact area was the precondition for high η by a Fe²⁺/H₂O₂/AA system. η decreased with the increase in NO concentration, which illustrated that this method would be efficient in oxidizing NO at a low concentration. η tended to decrease linearly with the growth in gas flow, however, the NO oxidation rate (v) rose with the increase in NO concentration and gas flow. η increased with the initial concentrations of H₂O₂ and Fe²⁺, but the amplitude decreased. Controlling the initial concentrations of H₂O₂ and Fe²⁺ to achieve reasonable synergies between generation rate and consumption rate of ·OH could weaken the invalid consumption of reactants. η increased with the increase in temperature in the range 30–60 °C, but it nearly did not change with temperature after 60 °C. This oxidation technology and the traditional wet flue gas desulphurization technology exhibited temperature synergy. Under typical pH of wet desulphurization, η and H₂O₂ consumption rate did not change obviously.     

A REACTION-EXTRACTION-REGENERATION SYSTEM FOR HIGHLY SELECTIVE OXIDATION OF BENZENE TO PHENOL

The reaction-extraction-regeneration system for the liquid-phase oxidation of benzene to phenol in the benzene-water-oxygen system was investigated. Phenol was extracted in the extractor to reduce the concentration of phenol in the benzene phase. As vanadium catalyst was oxidized to inactive species after the oxidation reaction, the regenerator was installed in the system to reduce the oxidation state of vanadium catalyst from V⁴⁺ or VO²⁺ to the active V³⁺ under H₂ flow. The effects of various operating parameters including concentration of VCl₃ catalyst, O₂ and H₂ flow rates, benzene bubble size, pH, surface area of Pt regeneration catalyst, the metal species, and amount of ascorbic acid were investigated. Ascorbic acid was employed as a reducing agent for helping reduce the V⁴⁺ form to the active form and therefore improving the activity of vanadium catalyst. VCl₃ catalyst concentration of 10 mol/m³ with pH of 3–4 in the reactor and Pt surface area of 0.05 m² in the regenerator showed optimal conditions for the system.     

Better Lime Purification of Raw Sugar Beet Juice by Advanced Fenton Oxidation Process

This work discusses the effects of Fenton oxidation pre-treatment on the lime purification of raw sugar beet juice using iron powder and hydrogen peroxide. During Fenton oxidation, particular attention was paid to the effect of reaction time and dosage of Fenton′s reagent to improve purification indexes of the raw juice throughout the clarification process. The total concentration of lime used for the purification was varied from 4.0 to 16.0 g of CaO/100 mL of juice. The results showed that higher color and total phenolic removal were achieved with an increase in H₂O₂ dosage and reaction time. At an initial pH of less than 6.2 and H₂O₂ concentration of 7000.0 ppm, color removal reached 85% and approximately 81% of total phenolic removal was achieved at a reaction time of 30 min (Treatment 5). It suggests that the quantity of CaO required for the efficient juice purification may be decreased from 16.0 g/100 mL for the control juice to approximately 12.0 g/100 mL for the juice obtained from Treatment 5. Fenton oxidation process improved the quality indexes of the purified juice, and can be combined with a conventional clarification process to achieve juice with high purity and low color.     

Combination of Ozone with Activated Carbon as an Alternative to Conventional Advanced Oxidation Processes

The objective of this study was to compare the efficiency of O₃/granular activated carbon (GAC) to enhance ozone transformation into ·OH radicals, with the common advanced oxidation processes (O₃/OH^?, O₃/H₂O₂). The results obtained with model systems under the given experimental conditions showed that the system O₃/OH^? (pH 9) and O₃/H₂O₂ (pH 7, [H₂O₂] = 1·10^?5 M) are more efficient than O₃/GAC (pH 7, [GAC] = 0.5 g/L) to enhance ozone transformation into ·OH radicals. However, in Lake Zurich water the O₃/GAC process has a similar efficiency as O₃/H₂O₂ for ozone transformation into ·OH radicals. The results also show that the presence of GAC during Lake Zurich water ozonation leads to (i) removal of hydrophilic and hydrophobic micropollutants, (ii) reduction of the concentration of CO₃ ^2?/HCO₃ ^?, and (iii) decrease of the concentration of dissolved organic carbon (DOC) present in the system.     

ACCELERATION OF THE WET OXIDATION REACTION OF PIPERAZINE BY HETEROGENEOUS Ru/TiO2 CATALYST

Wet air oxidation is a candidate technique for the effective treatment of wastewater contaminated by nitrogenous organic pollutants. Piperazine (PZ) is a cyclic diamine representing this class of compounds. In the present work, the wet oxidation reaction of PZ was studied for the first time. It was found that, in the studied range of temperatures of 180°–230°C and O₂ partial pressures of 0.69–2.07 MPa, the oxidation process was slow. Total organic carbon (TOC) conversion at 230°C and 0.69 MPa O₂ partial pressure was just 52% after 2 h. The investigated reaction was accelerated by a heterogeneous Ru/TiO₂ catalyst. Maximum TOC conversion (91%) was achieved during catalytic wet oxidation at 210°C and 1.38 MPa O₂ pressure. Kinetic data were collected over the range of temperatures 180°–210°C, O₂ partial pressures 0.34–1.38 MPa, and catalyst loading 0.11–0.66 kg/m³. The lumped TOC concentration decay was a two-step first-order process.     

Selective oxidation of propylene to acetone by molecular oxygen over Mx/2H5−x[PMo10V2O40]/HMS (M=Cu2+, Co2+, Ni2+)

The transition metal salts (Cu²⁺, Co²⁺ and Ni²⁺) of 10-molybdo-2-vanadophosphoric acid (H₅[PMo₁₀V₂O₄₀]) were supported on hexagonal mesoporous silica (HMS), and the resultant materials were used as catalysts for the selective oxidation of propylene to acetone by molecular oxygen. CuH₃[PMo₁₀V₂O₄₀]/HMS showed a high selectivity for acetone of 84.2% at 17.8% propylene conversion in a tubular fixed-bed reactor system under atmospheric pressure at 423 K. The high yield of acetone over CuH₃[PMo₁₀V₂O₄₀]/HMS at 423 K resulted from the proper acidity and oxidation ability of the heteropoly compound, the nature (acid property, redox property, etc.) of the Cu²⁺ counter-ion, the high surface area of the HMS support and the proper reaction temperature for the propylene oxidation.     

CuO Impregnated mesoporous silica KIT-6: a simple and efficient catalyst for benzene hydroxylation by C–H activation and styrene epoxidation reactions

Copper oxide doped mesoporous KIT-6 materials were synthesized by ultrasonication as impregnation method. The highly ordered nature of mesoporous CuO-KIT-6 materials analyzed by low angle X-ray diffraction. The high surface area, pore diameter and mesoporous nature of synthesized materials were confirmed by BET surface area analysis. Si–O–Si, Si–OH and Cu–O–Si bonds in the framework of CuO-KIT-6 were verified by FTIR spectroscopy. The Cu²⁺ ← O^2? charge-transfer transitions and d–d transitions of dispersed Cu²⁺ on ordered mesoporous KIT-6 were identified by DRS UV–Vis spectroscopy. The morphology of the synthesized CuO-KIT-6 materials was analyzed by HR-SEM. The 3D ordered nature of CuO-KIT-6 confirmed by TEM analysis. The highly ordered 3D mesoporous CuO-KIT-6 materials are excellent catalyst for benzene hydroxylation reaction through C-H activation and styrene epoxidation reaction with 30 % aqueous H₂O₂. The catalyst CuO-KIT-6 itself showed a good conversion towards both reactions.     

Quantification and redox property of the oxygen-bridged Cu<Superscript>2+</Superscript> dimers as the active sites for the NO decomposition over Cu-ZSM-5 catalysts

For a range of Cu-ZSM-5 catalysts with different Cu-exchange levels on the two kinds of ZSM-5 with different Si/A1 ratios, temperature programmed reduction using CO (CO-TPR) followed by H₂ (H₂-TPR), and temperature programmed desorption of oxygen (O₂-TPD) were conducted using an online mass spectrometer to characterize and quantify the copper species on the catalysts in the calcined state. Copper species on the ZSM-5 were quantitatively characterized as Cu²⁺, (Cu-O-Cu)²⁺ and CuO after calcination in oxygen environment. The N₂ formation activities of the catalysts in the decomposition of NO were well correlated with the quantified catalytic amounts of the Cu²⁺ ions involved in the Cu-dimers, (Cu-O-Cu)²⁺. The mol fraction of the Cu ions present as the Cu-dimers increased at the sacrifice of the isolated Cu²⁺ with increasing Cu ion exchange level, suggesting that the species could be formed between the two Cu²⁺ in close proximity. Oxygen that could be thermally desorbed from the oxidized catalysts in the O₂-TPD was responsible for the reduction of the Cu-dimers. It was concluded that the decomposition of NO over Cu-ZSM-5 catalyst proceeded by the redox of (Cu-O-Cu)²⁺, as active centers. With the temperature programmed surface reaction using N₂O or NO over an oxidized catalyst sample as well as the O₂-TPD, it was possible to estimate the change of the oxidation state of the Cu ions engaged in the Cu-dimers.     

Ceria-based Catalysts for the Production of H2 Through the Water-gas-shift Reaction: Time-resolved XRD and XAFS Studies

Hydrogen is a potential alternate energy source for satisfying many of our energy needs. In this work, we studied H₂ production from the water-gas-shift (WGS) reaction over Ce_1?x Cu _x O₂ catalysts, prepared with a novel microemulsion method, using two synchrotron-based techniques: time-resolved X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). The results are compared with those reported for conventional CuO _x /CeO₂ and AuO _x /CeO₂ catalysts obtained through impregnation of ceria. For the fresh Ce_1?x Cu _x O₂ catalysts, the results of XAFS measurements at the Cu K-edge indicate that Cu is in an oxidation state higher than in CuO. Nevertheless, under WGS reaction conditions the Ce_1?x Cu _x O₂ catalysts undergo reduction and the active phase contains very small particles of metallic Cu and CeO_2?x . Time-resolved XRD and XAFS results also indicate that Cu^δ+ and Au^δ+ species present in fresh CuO _x /CeO₂ and AuO _x /CeO₂ catalysts do not survive above 200 °C under the WGS conditions. In all these systems, the ceria lattice displayed a significant increase after exposure to CO and a decrease in H₂O, indicating that CO reduced ceria while H₂O oxidized it. Our data suggest that H₂O dissociation occurred on the O_vacancy sites or the Cu–O_vacancy and Au–O_vacancy interfaces. The rate of H₂ generation by a Ce_0.95Cu_0.05O₂ catalyst was comparable to that of a 5 wt% CuO _x /CeO₂ catalyst and much bigger than those of pure ceria or CuO.     

Influence of presence of tannic acid on removal of sodium dodecylbenzenesulphonate by O3 and advanced oxidation processes

BACKGROUND: The objective of the present investigation was to determine the role of the tannic acid (TAN) component of organic matter dissolved in water, in the removal of sodium dodecylbenzenesulphonate (SDBS) by ozone and by O₃/H₂O₂, O₃/granular activated carbon (GAC) and O₃/powdered activated carbon (PAC) advanced oxidation processes. RESULTS: Low doses of TAN (1 mg L^?1) during SDBS ozonation cause (i) an increased ozone decomposition rate and (ii) an increased SDBS removal rate. The SDBS removal rate with ozone in the presence of TAN was reduced when HCO₃^? ions were added. A rise in TAN concentration increased the SDBS removal rate, with a linear relationship between added TAN and the removal rate. SDBS was removed more effectively by O₃/GAC, O₃/PAC and O₃/H₂O₂ systems in the presence of TAN. CONCLUSIONS: Results obtained indicated two mechanisms involved in the generation of HO^· radicals by the O₃/TAN interaction: (i) direct generation of HO^· radicals from the reaction between ozone and TAN, and (ii) increased generation of O₂^?· radicals in the medium, enhancing the transformation of ozone into HO^· radicals by different radical reactions. In O₃/GAC and O₃/PAC systems, HO^· radicals are mainly generated in the O₃/TAN interaction, which is a homogeneous reaction with fast kinetics, whereas the O₃/GAC and O₃/PAC interactions are in a heterogeneous phase with much slower kinetics, and are therefore not competitive in the generation of HO^· radicals. Copyright © 2008 Society of Chemical Industry     

Highly stable Fe/γ‐Al2O3 catalyst for catalytic wet peroxide oxidation

BACKGROUND: A highly stable Fe/γ‐Al₂O₃ catalyst for catalytic wet peroxide oxidation has been studied using phenol as target pollutant. The catalyst was prepared by incipient wetness impregnation of γ‐Al₂O₃ with an aqueous solution of Fe(NO₃)₃· 9H₂O. The influence of pH, temperature, catalyst and H₂O₂ doses, as well as the initial phenol concentration has been analyzed. RESULTS: The reaction temperature and initial pH significantly affect both phenol conversion and total organic carbon removal. Working at 50 °C, an initial pH of 3, 100 mg L^?1 of phenol, a dose of H₂O₂ corresponding to the stoichiometric amount and 1250 mg L^?1 of catalyst, complete phenol conversion and a total organic carbon removal efficiency close to 80% were achieved. When the initial phenol concentration was increased to 1500 mg L^?1, a decreased efficiency in total organic carbon removal was observed with increased leaching of iron that can be related to a higher concentration of oxalic acid, as by‐product from catalytic wet peroxide oxidation of phenol. CONCLUSION: A laboratory synthesized γ‐Al₂O₃ supported Fe has shown potential application in catalytic wet peroxide oxidation of phenolic wastewaters. The catalyst showed remarkable stability in long‐term continuous experiments with limited Fe leaching, < 3% of the initial loading. Copyright © 2010 Society of Chemical Industry     

Oxidation and Oxidative Bromination Reactions Catalyzed By a Reusable Polymer-Anchored Iron(III) Complex in Water at Room Temperature

A polymer-anchored iron(III) catalyst was synthesized and characterized. Its catalytic activity was evaluated for the oxidation of various alkenes, sulfides, aromatic alcohols and ethylbenzene with 30 % H₂O₂ as the oxidizing agent. The catalyst was also effective for the oxidative bromination reaction with 80–100 % selectivity of monobrominated products with H₂O₂/KBr at room temperature. The above reactions require a minimum amount of H₂O₂ and short reaction time. Most importantly, all the above reactions occur in aqueous medium. The catalyst can be facilely recovered and reused six-atimes without significant decrease in its activity and selectivity.     

Comparative Study of the Physico-Chemical Properties of Nanocrystalline CuO–ZnO–Al2O3 Prepared from Different Precursors: Hydrogen Production by Vaporeforming of Bioethanol

The physico-chemical and catalytic properties of CuO–ZnO–Al₂O₃, synthesised by sol–gel process (SG), impregnation method (IMP) and a combination of both preparative procedures (ISG), were comparatively studied. Samples were characterised with thermogravimetric-differential thermal analysis (TG–DTA), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) techniques and oxygen chemisorption. XPS study was not consistent with the bulk findings and revealed the presence of Cu²⁺, Cu⁺ and/or Cu⁰ species at the catalysts surface. Surface analysis revealed also that copper enrichment occurred mainly at the surface of SG and IMP solids. The reducibility of the mixed oxides catalysts was always modified with respect to that of pure copper oxides phases and the reduction of CuO was markedly affected by the presence of ZnO–Al₂O₃. Temperature programmed reduction (H₂-TPR) analysis showed that the temperature corresponding to maximum reduction rate of copper oxide was ca. 256 °C for IMP sample and ca. 296 °C for both SG and ISG solids. These latter showing a high resistance to reduction suggest a strong interaction of copper species with ZnO–Al₂O₃, limiting thus copper particles sintering. CuO particle size was found to be ca. 20 nm for both SG and ISG solids and ca. 40 nm for IMP catalysts. Besides, at 300 °C SG and ISG samples showed superior amount of reversible O₂ uptake with respect to IMP solids. Catalytic activity of CuO–ZnO–Al₂O₃ was measured with bio-ethanol steam reforming reaction. SG catalysts exhibited both high selectivity to hydrogen and high stability with time on stream than IMP and ISG catalysts. This was attributed both to the particles size of copper species, their amount on the catalytic surface and to their strong interaction with ZnO–Al₂O₃.     

A novel carbon aerogel prepared for adsorption of copper(II) ion in water

A novel carbon aerogel with network pore and surface group of hydroxyl was prepared from cellulose colloid, through sol-gel reaction, freeze-drying and carbonization. Surfactant like isooctyl alcohol ether phosphate was taken as structure inducer in sol-gel reaction, for construction of porous network in the prepared samples. Characteristic of a specific area about 725.12 m²/g and total pore volume about 0.64 cm³/g, the prepared cellulose-based carbon aerogel of CCA₂, has a maximum capacity about 55.25 mg/g for Cu²⁺ in neutral aqueous solution. Its adsorption equilibrium can be reached within 10 min in an aqueous solution of pH7.0 at 25?°C, while desorption of Cu²⁺ need about 1 h eluted by HCl or HNO₃ solution of 0.01 M. And regeneration of the carbon aerogel in adsorption of Cu²⁺ can be repeated for five times, remaining 96% adsorption capacity. It is also found in adsorption process the kinetics nicely follows pseudo-second-order rate expression, and the isotherm fits Langmuir model.     

Adsorption of Cu2+ Cations from Aqueous Solution by S-doped TiO2

S-doped TiO₂ as a novel adsorbent for Cu²⁺ cations removal from aqueous solutions was synthesized by simple sol-gel process. Removal of Cu²⁺ cations from aqueous solutions was investigated with particular reference to the effects of initial Cu²⁺ cations concentration, pH-value, adsorbent dosage, and temperature on adsorption. It was found that the maximum adsorption capacity was 96.35 mg g^?1 at 328 K. The adsorption equilibrium isotherms and the kinetic data were well described by the Langmuir and pseudo-second-order kinetic models, respectively. The high uptake capability of S-doped TiO₂ makes it a potentially attractive adsorbent for the removal of heavy metal pollutants from aqueous solution.