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The electrochemical reduction of nitrate and ammonium ion oxidation has been performed with the cathode (Al) and anode (Ti/RuO₂) in the explosive industry wastewater polluted with a significant quantity of NO₃– and NH₄⁺. For this, the influences of various other cathode materials (Fe, Cu, and C), the current density (j = 35.71 to 142.86 A m–²), wastewater pH (pH = 3–12), and treatment time (t = 180 min) were analyzed for nitrate ion reduction, ammonium ion oxidation, nitrite ion generation, and total nitrogen (TN) degradation. The maximum nitrate removal and TN removal efficiencies were found to be ≈51 and ≈63% at j = 142.86 A m–² and wastewater natural pH after 180 min treatment time, respectively. In this condition, SEC was calculated to be 74.4 kWh (kg NO₃– reduced)⁻¹. The mechanistic analysis suggested that the atomic hydrogen molecules, H⁺, and e– help in the nitrate ion reduction and the available Cl– ion in the wastewater helps in the oxidation of the ammonium ion into gaseous nitrogen through the electrochemical process. The new and used electrodes were characterized by FE-SEM, AFM, and XRD techniques. Electrodes were also characterized within untreated and treated wastewater through CV and EIS analysis. The in situ generated oxidizing species were identified by the p-nitrosodimethylaniline (RNO) bleaching test. Pseudo-first-order and nᵗʰ-order kinetic models were applied, and the reaction rate was calculated to understand the reaction rate of the nitrate reduction. The approximate operational cost estimation has been performed for the lab-scale batch reactor treatment of the explosive industry wastewater. No scum or sludge was produced throughout the treatment process. This study helps to understand the parametric, mechanistic, and kinetic aspects of electrochemical nitrate reduction and oxidation of the previously present and produced ammonium ion in the explosive industry wastewater.

This study reports an electrochemical reduction of the NO3− along with oxidation of the in-situ generated NH4+ with maximum selectivity of the N2 gas as the final-product. The use of aluminum as a cathode and Ti/RuO2 as an anode showed enhanced electrochemical nitrate reduction at the cathode and oxidation of the ammonium ion at the anode. Effects of various parameters like initial NO3− concentration (Co = 100−400 mg L−1), a dose of the Cl− as NaCl (NaCl = 100−400 mg L−1), current density applied (j = 83.3-333.3 A m−2), solution pH (pH = 4–10) and electrolysis time (t = 0−120 min) were studied in terms of NO3− reduction and total nitrogen (TN) removal efficiencies. Current efficiency (CE) was elaborated with respect to end products like N2, NO2− and NH4+. Specific electrical energy consumption (SEC) was calculated in kWh kg−1 NO3− removed for the electrochemical process. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were utilized for understanding the oxidation/reduction mechanism over electrodes and the characteristics of the electrodes in a different solution. The studied mechanism suggested a circular conversion of NO3− through complex processes into the N2 gas as the final product. The ultimate nitrate and TN degradation efficiency of ≈95 % with N2 selectivity of ≈100 % were achieved at the optimum condition of Co = 100 mg L−1, NaCl = 300 mg L−1, j = 333.3 A m−2, pH = 6 and time = 120 min with SEC = 927.4 kW h kg−1 NO3− removed. The 1st, 2nd, and nth-order kinetic models were used for the reaction kinetics. FE-SEM, XRD, and AFM techniques were used for the characterization of the electrodes before and after all the electrochemical runs. The operating cost was calculated for lab-scale treatment along with a comparison with previous studies. No sludge or scum got produced for each electrochemical run. Finally, this study delivers a superior perceptive for electrochemical characteristics of Al at the cathode side and Ti/RuO2 at anode side as well as electrochemical NO3− reduction and oxidation of the generated NH4+, simultaneously.

Present study proposed a sorption and desorption approach of aqueous mercury ion (Hg2+) on sulfur impregnated attapulgite (ATPS) adsorbent. Morphological characterization of natural and impregnated ATP confirmed the mesoporous nature of ATPS-adsorbents. The presence of various types of functional groups on the surface of ATPS was confirmed by using the zeta-potential measurement, X-ray fluorescence (XRF), and FT-IR analysis. Batch adsorption tests were carried out to detect the optimum condition of temperature for sulfur impregnation, and the results illustrated that the best adsorbent (ATPS-500) produced via the impregnation at 500 °C, with the highest equilibrium uptake of Hg2+ at initial pH 7. Different parameters like solution pHo, initial concentration of mercury (Co), temperature (T), contact time (t) and the effect of co-existing ions were optimized. Optimum pH and equilibrium contact time at the optimum dose of adsorbent (m) = 0.02 g in 50 mL and Co = 2.0 mg L − 1 were found to be pH~5 and 24 h at T = 313 K for ATPS-500.The best representation of adsorption kinetic was followed by the pseudo-first order kinetic model. The adsorption of Hg2+ions onto ATPS-500 was found to be endothermic. The heat of adsorption and changes in the entropy of Hg2+ions sorption on ATPS-500 were determined as 10.35 kJ mol−1 and 0.16 kJ mol−1 K − 1, respectively. Thermal regeneration represented that ATPS-500 was used for five desorption–sorption cycles with excellent efficiency of Hg2+ in each cycle.

The main objective of the present work was to understand the interactive behaviour of various operating parameters including concentration of pollutants during binary electrochemical mineralization of the two nitrogenous heterocyclic pollutants in the aqueous solution. Indole and pyrrole were selected as pollutants, whereas Pt/Ti was selected as anode and cathode. The effects of different operating parameters like current density, solution conductivity, initial concentration of the pollutants and time were studied. Taguchi method was used to optimize these operating parameters for obtaining the ultimate rate of degradation for the nitrogenous compounds. There were basically two responses, i.e. chemical oxygen demand (COD) degradation and specific energy consumption. These responses were maximized and minimized, respectively. At the optimum condition, removal efficiencies of pyrrole, indole and COD were found to be 46.1%, 62.4% and 61.4%, respectively. The optimum value of specific energy consumption was found to be 159.5 kWh per kg COD removed. Possible mineralization pathways are also proposed on the basis of the identified intermediates by gas chromatography coupled with mass spectroscopy. The operating cost was also calculated for the binary lab-scale treatment of the indole and pyrrole and compared with reported cost analysis for the electrochemical treatment.

Two kinetic models, i.e., schemes, surface adsorbed nitrogen as divergent (SND) and surface adsorbed NO as divergent (SNOD) towards NH4+ and N2 production, were developed to model simultaneous electrochemical reduction of the nitrate ion (NO3−) and oxidation of by-products. Experimental data for electrochemical reduction was collected in synthetic nitrate solution and actual wastewater using Al and Ti/RuO2 as cathode and anode, respectively. Sum of square errors (SSE) and Akaike's information criterion (AIC) analysis showed that the SND model well-represented all the concentration profiles of nitrogen species with the variation in all the operating parameters. Desorption of nitrite ion from the cathode surface was the rate-determining step for the SND kinetic model. Mechanistic and kinetic analysis suggested that N2 gas was the main product. However, NO2− gets formed as the by-product in the alkaline environment, whereas, NO2− and NH4+ were the by-products in the acidic environment.

This paper reports the use of novel ceria-zinc catalyst for the preparation of dimethyl carbonate (DMC) using transesterification of PC with methanol. Ceria-zinc oxide catalysts were prepared by a sol-gel method using citric acid, oxalic acid and tartaric acid as chelating agents (named as CZC, CZO, and CZT, respectively). The synthesized catalysts were characterized by XRD, N2 adsorption-desorption, FTIR, SEM-EDX, ICP-OES, and CO2-temperature program desorption. Experimental results revealed that the catalytic performance of CZC was closely related to the surface area and presence of basic sites in the catalyst. CZC showed high selectivity and PC conversion. Effects of operating parameters such as methanol/PC molar ratio, catalyst dose, reaction temperature, reaction time were studied. The reusability of CZC as a catalyst for DMC selectivity and PC conversion with turn-over frequency (TOF) was also studied.

In the present study, simultaneous adsorption of quinoline and pyridine onto adsorbents such as granular activated carbon (GAC) and bagasse fly ash (BFA) from pyridine–quinoline binary aqueous solution was studied at various temperatures (288–318 K). Gathered equilibrium adsorption data were further analysed using various multicomponent competitive isotherm models such as non-modified and modified competitive Langmuir isotherms, extended-Langmuir isotherm, extended-Freundlich model, Sheindorf–Rebuhn–Sheintuch (SRS) model, and non-modified and modified competitive Redlich–Peterson isotherm model. It was observed that increase in pyridine concentration decreased the total adsorption yield and the individual adsorption yield for both the quinoline and pyridine for both the adsorbents GAC and BFA at all the temperatures studied. Identical trend was observed during the equilibrium uptake of pyridine on to GAC and BFA with an increase in quinoline concentration. The extended-Freundlich model satisfactorily represented the binary adsorption equilibrium data of quinoline and pyridine onto GAC and BFA.

Propylene carbonate is an important organic carbonate having wide applications. In the present work, thermodynamic analysis of propylene carbonate synthesis routes was performed. Benson group contribution method and Rozicka–Domalski model were used to estimate the heat of formation and the heat capacities of some of the components, respectively. Urea alcoholysis was found to be a favorable method for producing propylene carbonate under mild conditions. This route was further studied experimentally using various MgAl and ZnAl hydrotalcite derived catalysts. The catalysts were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption–desorption, and Fourier transform infrared spectroscopy (FTIR) techniques. Yield of PC was found to be strongly correlated to the basicity of catalysts. Addition of a third element, Ca or La, was found to reduce the surface area of the catalysts. Fluorinated MgAlO (MgAlO-F) was found to possess greater basicity than MgAlO and greater catalyt...

Indole is a highly recalcitrant aromatic heterocyclic organic compound consisting of a five-membered nitrogen-containing pyrrole ring fused to a six-membered benzene ring. This study presents the results of the electro-chemical mineralization of indole in an aqueous solution using platinum-coated titanium (Pt/Ti) electrode. A central composite design was used to investigate the effect of four parameters namely initial pH (pHo), current density (j), conductivity (k) and treatment time (t) at 5 levels. Multiple responses namely chemical oxygen demand (COD) removal (Y 1) and specific energy consumption (Y 2) were simultaneously maximized and minimized, respectively, by optimizing the parameters affecting the mineralization of indole by using the desirability function approach. At the operating conditions of pH 8.6, j = 161 A/m2, k = 6.7 mS/cm and t = 150 min, 83.8% COD removal with specific energy consumption of 36.3 kWh/kg of COD removed was observed. Ultra performance liquid chromatography, UV–visible spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry of the indole solution were performed at the optimum condition of the treatment so as to report a plausible mechanism of indole degradation. Field emission scanning electron microscopy analysis of electrodes before and after treatment was performed for determining the changes on anode surface during the treatment. Thermal analysis of the solid residue (scum) obtained was also performed for exploring its disposal prospects. Present study shows that electro-chemical oxidation can be used for mineralization of nitrogenous heterocyclic compounds such as indole.

Diethyl carbonate, an important member in the family of organic carbonates, is a fuel additive like dimethyl carbonate (DMC). It holds an extra edge of having better gasoline/water distribution coefficient than DMC, and also DEC is widely used as an electrolyte in lithium ion batteries. Ethanolysis of ethyl carbamate (EC) is the most economical and greener route for DEC synthesis. Zn–Al–M (M=Ca, La, Mg and Y) have been synthesized using two methods and their activity have been explored DEC systhesis from EC and ethanol. The catalysts were characterized using thermogravimetric analysis, Brunauer, Emmett and Teller surface area, N2 adsorption–desorption textural analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, temperature-programmed desorption (TPD), atomic-force microscopy and Raman spectroscopy. Pure metal oxides were observed during the XRD analysis and Al2O3 was found to be in amorphous form. Third metal oxide prepared from impregnation method was found to be present on the surface as well as in impregnated form. CO2-TPD analysis showed close correlation between the basicity and the DEC yield. Zn–Al–Mg, prepared from precipitation method, being most basic, was found to be most effective although the performances of Zn–Al–Ca and Zn–Al–La were good. The effect of precipitants was also studied by synthesizing Zn–Al–Mg using NaOH and liquid NH3 as precipitants. DEC yield of 40.2% and turn over frequency of 1055 mgDEC gcat −1 h−1 was obtained in 5 h at 190 °C using Zn–Al–Mg prepared from precipitation method. Effect of reaction conditions was also studied and equilibrium constant of the reaction was estimated using the Benson group contribution method.

Diethyl carbonate (DEC) is a linear organic carbonate which has applications as a fuel additive, in production of polycarbonates, and as a solvent in lithium ion batteries. Ethanolysis of urea, as compared to other methods of DEC synthesis, has an edge having requirements of cheap and abundant raw materials. However, only few studies have been reported due to low acidity of ethanol. In the present study, cerium-zinc based oxides in various molar ratios were used for DEC synthesis from ethanol and urea. These catalysts were prepared by auto combustion technique and characterized by thermogravimetric analysis (TGA), Raman spectroscopy, X-ray diffraction (XRD), N 2 adsorption-desorption, field emission scanning electron microscope (FE-SEM), energy dispersive X-ray (EDX), Fourier transform infra-red (FTIR), and NH 3 - and CO 2 -temperature programmed desorption (TPD) methods. No additional phases except pure Ce and Zn oxide were observed in the catalyst from XRD analysis. Effects of pore surface area and surface acidity/basicity were found to be profound in the synthesis of DEC. DEC yield of 28.8% was obtained at 190 °C and 5 h using Ce 0.1 -Zn 0.9 mixed oxide. Effect of operating parameters such as ethanol/urea molar ratio, temperature, time and catalyst concentration were also studied.

In this study, ceria-zirconia based catalysts (CeO 2 , ZrO 2 and Ce 0.5 Zr 0.5 O 2 ) were synthesized by hydrothermal method and characterized by N 2 -sorption, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Acidity and basicity of synthesized catalysts were investigated by NH 3 and CO 2 temperature-programmed desorption (TPD). Brunauer-Emmett-Teller (BET) surface area of CeO 2 , Ce 0.5 Zr 0.5 O 2 and ZrO 2 were found to be 88, 117 and 70 m 2 g −1 and average crystallite sizes was 9.48, 7.09 and 9.45 nm, respectively. These catalysts were further used for direct conversion of CO 2 with methanol for the synthesis of dimethyl carbonate (DMC). DMC yield was found to be highly dependent upon the both basicity and acidity of catalysts. Ce 0.5 Zr 0.5 O 2 catalysts showed better activity as compared to CeO 2 and ZrO 2 catalysts. Effect of reaction conditions (such as catalyst dose, reaction temperature and reaction time) and catalyst reusability was studied with Ce 0.5 Zr 0.5 O 2 catalyst. The optimum operating condition for direct conversion of CO 2 into DMC at constant pressure of 150 bar were found to be reaction time = 24 h, catalyst dose = 1.25 g and temperature = 120 °C. Moreover, chemical equilibrium modeling was performed using Peng–Robinson–Stryjek–Vera equation of state (PRSV-EoS) along with the van der Waals one-fluid (1PVDW) mixing rule to calculate the heat of reaction and Gibbs free energy change.

Carbon dioxide has generated great interest in recent years because of its potential usage as an alternative to traditional sources of carbon such as natural gas, petroleum and coal. In this paper, CO2 in combination with methanol was used for dimethyl carbonate (DMC) synthesis in presence of cerium-calcium mixed oxide catalysts. Catalysts with different Ce/Ca molar ratios were synthesized using surfactant templating method and characterized by powder X-ray diffraction (XRD), Raman spectroscopy, N2–sorption, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and temperature-programmed desorption (TPD) of CO2 and NH3. The direct conversion of CO2 was found to be highly dependent upon the acidity and basicity of catalysts. Brunauer-Emmett-Teller (BET) surface area of Ce3 Ca1, Ce1 Ca1 and Ce1 Ca3 was found to be 102, 82, 109 m2/g, respectively, and the average pore diameter was 9, 12 and 5 nm, respectively. The Ce1 Ca1 catalyst performed the best due to its combined acidic-basic properties. In addition, the catalyst was reused up to five cycles without significant loss of performance.

Electrochemical oxidation of 4-chlorophenol (CP) was investigated (in terms of chemical oxygen demand (COD) and CP removal efficiencies) by using a dimensionally stable anode (DSA) namely ruthenium oxide coated titanium (Ti/RuO 2 ) electrode. Effect of process conditions such as current density ( j ), electrolyte concentration ( m ), initial pH (pH o ), time ( t ) and initial CP concentration ( C o ) has been studied. Current efficiency (CE) and specific energy consumption (SEC) were also measured. Gas chromatograph-mass spectrometry (GC/MS) analysis was used to understand the CP mineralization mechanism which has been established on the basis of intermediates identified such as benzoquinone, hydroquinone and organic acids. Reaction kinetics was expressed by pseudo-first order kinetic model. Maximum COD removal efficiency of 96.7% and CP removal efficiency of 97.2%, respectively, was observed at j = 222.22 A/m 2 , t = 180 min, pH o = 5.2 and m = 400 mg/l with SEC = 655 kWh/kg COD. Operating cost based on the studies performed on laboratory scale EC reactor has been calculated and compared with those reported for other pollutants degradation.

In this work, quinoline (a recalcitrant poly-nuclear aromatic compound) mineralization was studied by catalytic peroxidation process using ceria impregnated granular activated carbon. Various catalysts with different loading of ceria were prepared by wetness impregnation method and further characterized by liquid nitrogen adsorption–desorption technique, X-ray diffraction, scanning electron microscopy, thermo-gravimetric analysis and Fourier transform infrared spectroscopy. Effects of various parameters like ceria loading, pH, catalyst dose (C w), H2O2/quinoline molar ratio, initial concentration (C o) of quinoline, reaction temperature (T) and time on quinoline degradation and chemical oxygen demand (COD) removal efficiencies were studied. Quinoline degradation of 81.6% and COD removal of 86.5% were observed at optimum operating condition of pH = 4, C o = 100 mg/L, Ce loading = 7.5 wt%, H2O2/quinoline molar ratio = 1, C w = 0.5 g/L, T = 55 °C and reaction time = 4 h. The kinetics of the oxidation process was represented by the power law model.

Present study investigates the direct and indirect electrochemical (EC) oxidation of malachite green (MG) dye in acidic and basic medium using RuO2–TiO2 and Pt coated Ti mesh electrodes (Ti/RuO2–TiO2 and Ti/Pt electrodes). The effects of process parameters such as current density (j), initial pH (pHo) and NaCl (electrolyte) concentration (m) during the EC oxidation were also examined. This study investigates the effect of dissolved chlorine, chlorate, chlorite, and chlorine dioxide formed during EC oxidation at different pH. Active sites of electrodes surface promote the production of OH radicals ( OH). Synergistic effect of active chlorine species and OH radicals significantly enhanced the indirect EC oxidation of MG dye solution with Ti/RuO2–TiO2 anode. Gas chromatography-mass spectrometry (GC–MS), high performance liquid chromatography (HPLC), color and chemical oxygen demand (COD) were used to identify the EC oxidative degradation mechanism with both electrodes. Acidic pH was found to promote the dye degradation. Under optimum condition, MG dye was completely decolorized and 98% COD removal was obtained after 140 min of EC treatment. Based on the intermediate and by-products identification, it seems that MG dye degradation occurred via N-methylation and conjugated structure destruction.

In this study, teff (Eragrostis tef) straw has been chemically treated and tested as an adsorbent for Cr(VI) removal. Chemically treatment of teff straw was done by NaOH, H3PO4 and ZnCl2 solutions. Scanning electron micrograph and X-ray diffraction were used for anatomical characterization, whereas Fourier transform infrared spectroscopy was used for surface change characterization of adsorbents. Effects of different experimental parameters like pH (2–12), initial Cr(VI) concentration (100–900 mg/L), adsorbent dose (2.5–20 g/L), contact time (15–360 min) and temperature (288–318 K) were studied. Temperature increment was found to stimulate the adsorption process. Langmuir isotherm was found to give better representation over wide range of temperature for untreated, H3PO4- as well as ZnCl2-treated teff straw, and Freundlich isotherm best represented the isotherm data for NaOH-treated teff straw. Maximum Cr(VI) adsorption capacity of untreated, NaOH-, H3PO4- and ZnCl2-treated teff straw was found to be 86.1, 73.8, 89.3 and 88.9 mg/g, respectively. Respective values of average effective diffusion coefficient (D e) were found to be 2.8 × 10−13, 2.59 × 10−14, 1.32 × 10−13 and 1.14 × 10−13 m2/s, respectively. The negative value of ΔG o for all the adsorbents indicates Cr(VI) spontaneous adsorption. Isosteric heat of adsorption (ΔH st,a) was found to vary with surface coverage (θ). ΔH st,a increased for untreated, H3PO4- and ZnCl2-treated teff straw, and decreased steadily with θ for NaOH-treated teff straw.

Cylindrical rod-shaped copper succinate nanoparticles were prepared using the electrochemical method. Taguchi robust design was applied to optimize experimental parameters such as succinic ion concentration (Co), current applied (Iap), and pH (pH). The obtained copper succinate nano-rods were further thermally treated at different temperatures to produce copper oxide (CuO) nano-disks. At optimum conditions of Iap = 0.5 A, pH = 7, and Co = 0.25, the maximum productivity of copper nanoparticles before and after calcination at 500 °C was 1.53 g and 1.06 g, respectively. Products were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectrophotometry to determine their various physicochemical characteristics.

Tungsten trioxide (WO3) is an oxygen deficient metal oxide and well known semiconductor with a small band gap of between 2.4 and 2.8 eV. It is also used as a photo-catalyst for degradation of organic pollutants present in aqueous environment. It has stable physico-chemical properties and shows strong absorption of solar spectrum and thus can be used in visible-light driven photocatalysis. WO3 has a conduction band (ECB) of +0.4 V versus NHE (normal hydrogen electrode) at pH = 0. Therefore, pure WO3 has lower light energy conversion efficiency as compared to other widely used photocatalysts such as zinc oxide (ZnO) and titanium oxide (TiO2). This is because the reduction potential of the electrons in WO3 is low due to its low conduction band level. O2 cannot be efficiently trapped in the conduction band electrons to yield superoxide radicals and fast recombination of charge carriers takes place resulting in lesser photocatalytic activity of WO3. However, holes in the valence band (EVB = +3.1 V) are energetically favorably situated to oxidize water to hydrogen. To modify the energy band position and reduce the charge carrier recombination, doping or surface modification of WO3 is necessary. This review article demonstrates the effect of dopants (low band semiconductor catalyst) on the surface modification of WO3 to enhance the photo catalytic activity which helps in degradation of the organic pollutants present in the wastewater.

In this work, Ce–M catalysts (M = Co, Fe, Cu and Zn) synthesized by sol-gel method and characterized by various techniques have been evaluated for the transesterification of propylene carbonate (PC) with methanol for dimethyl carbonate (DMC) synthesis in a batch reactor. The catalysts were characterized by various techniques such as X-ray diffraction (XRD), N2-sorption analysis, scanning electron microscope (SEM-EDX) etc. Total basicity of CeCo, CeCu, CeZn and CeFe catalysts were 0.083, 0.698, 0.424 and 0.492 mmol/g with crystalline sizes found to be 19.4, 18.8, 9.6 and 21.6 nm, respectively. Best performing catalyst CeCu was further used for optimization of operating conditions such as methanol/PC molar ratio, catalysts dose, reaction time, reaction temperature and kinetics study. The reaction rate constant values as obtained using non-linear regression analysis were found to be 0.285, 0.570 1.255 and 1.596 h−1 at 120, 140, 160 and 180 °C, respectively for the CeCu catalyst. Reusability of the catalyst was studied in terms of PC conversion and turn over frequency.

Sulfur oxides emission because of burning of liquid fuels has become a global environmental challenge. Refineries need to meet ever-stringent liquid fuel standards by using newer desulfurization methods. Present paper reports the results of the studies on adsorptive removal of sulfur compounds from model fuel by zinc-impregnated granular activated carbon (GAC). Zn-loaded adsorbent (Zn-GAC) prepared by wet impregnation method was characterized for its textural, morphological, and structural characteristics by different techniques like liquid nitrogen adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The adsorbent was further used for the removal of dibenzothiophene (DBT), a sulfur compound, from iso-octane. Equilibrium adsorption was obtained in 6 h. The equilibrium adsorption data were well represented by the Redlich–Peterson isotherm. Thermodynamic parameters were calculated by applying the van’t Hoff and Clausius–Clapeyron equations. Values of change in enthalpy and entropy were found to be 4.89 kJ/mol and 30 J/mol K, respectively. Isosteric heat of adsorption was correlated with surface coverage and heterogeneous nature of the Zn-GAC.

In this paper, a series of CexZr1−xO2 solid solution spheres were synthesized by exo- and endo-templating methods and tested for dimethyl carbonate (DMC) synthesis using direct conversion of CO2. The synthesized catalysts were characterized by X-ray diffraction (XRD), N2-physisorption, scanning electron microscopy (SEM), and CO2/NH3-temperature-programmed desorption (TPD). Formation of CexZr1−xO2 solid solutions with tetragonal and cubic crystal structures depending on cerium/zirconium compositions was confirmed by XRD analysis. The specific surface area of the mixed oxide decreased and the average pore diameter increased with an increase in the ceria content, with the exception of the mixed oxides with x = 0.4–0.5 i.e. Ce0.4Zr0.6O2 and Ce0.5Zr0.5O2. The basic and acidic site density of the synthesized catalysts was in the order: ZrO2 < CeO2 < Ce0.5Zr0.5O2, and the basic and acidic site density per unit area followed the same order. The best Ce0.5Zr0.5O2 catalyst was further used for the optimization of reaction conditions such as reaction time, reaction temperature, catalyst dose and reusability for DMC synthesis. Furthermore, study of chemical equilibrium modeling was done using the Peng–Robinson–Stryjek–Vera equation of state (PRSV-EoS) along with the van der Waals one-fluid reaction condition so as to calculate change of Gibbs free energy (ΔG°) and heat of reaction (ΔH°).

Utilization of carbon-do-oxide (CO 2 ) to produce alternative chemicals such as dimethyl carbonate (DMC) is one of the high priority areas of research. In this paper, ceria based catalyst were synthesized, characterized and used for DMC synthesis from CO 2 and methanol. Prepared catalyst was characterized by various techniques such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM), temperature programmed desorption (TPD) by NH 3 and CO 2 , Fourier transform infrared spectroscopy (FTIR) and N 2 adsorption–desorption. The catalytic activities were correlated with the basic and acidic properties of ceria catalyst for the synthesis of DMC in a batch reactor. The larger acidic and basic sites facilitated the DMC formation due to activation of methanol to methoxyl species and further reaction with CO 2 . Molecular sieve has been used as dehydrating agent to remove water, shift the thermodynamic equilibrium and facilitate higher DMC formation. Ceria catalyst showed DMC yield of 2.046 mmol DMC/g.cat at reaction temperature of 120 °C, pressure 150 bar and reaction time of 4 h.

This study focuses on the photocatalytic degradation of quinoline, a recalcitrant heterocyclic nitrogenous aromatic organic compound, using the mixed oxide ZnO–TiO2 photo-catalyst. Photo-catalysts were synthesized by the solid-state reaction method at different calcination temperatures of 400 °C, 600 °C, and 800 °C. Different analytical methods, including Field emission scanning electron microscope, Brunauer-Emmett-Teller surface area, X-ray diffraction, UV–vis diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy analysis were used for the catalyst characterization. The highest pore surface area of 57.9 m2g−1 was obtained for the photo-catalyst calcined at 400 °C. The effects of calcination temperature, solution pH, initial concentration, catalyst dose as well as irradiation time were studied. At the optimum condition, i.e., calcination temperature of 400 °C, pH ≈8 and catalyst dose of 2.5 gL−1, maximum quinoline degradation and total organic carbon (TOC) removal efficiency of ≈92% and ≈78% were obtained after 240 min for initial quinoline amount of 50 mgL−1. The 1st, 2nd, and nth-order kinetic models were applied to analyze the quinoline degradation rate. The photocatalytic mechanism was studied by drawing energy level diagram with the help of the band-gap structures of the ZnO and TiO2, potential of the free radicals like OH and O2 and HOMO-LUMO energy gap of the quinoline molecule. The proposed pathways of quinoline mineralization were suggested on the basis of the identified intermediates by the gas chromatograph-mass spectrometer analysis and scavenger study.

Efficient removal of uranium from both aqueous and simulated seawater conditions using a nitrogen enriched nanoporous polytriazine (NENP-1), is reported. A maximum adsorption capacity of 489 mg g−1 with 97.8% adsorption efficiency was estimated at 25 °C and pH of 7, when 10 mg of NENP-1 was introduced to 10 mL of 500 mg L−1 aqueous uranium solution. Both linear and non-linear regression analyses have been performed. The adsorption follows a pseudo second order kinetics and fitted well with the Langmuir adsorption isotherm model. The negative values of ΔS (−52.08 J mol−1 K−1), ΔH (−24.37 kJ mol−1) and ΔG indicate that the uranium adsorption is a spontaneous exothermic process with a reduced entropy. Retention of 93% activity even after five consecutive cycles, achieving (0.012 mg L−1) the permissible limits of the WHO (0.015 mg L−1) and USEPA (0.03 mg L−1) and adsorption of uranium (50 mg g−1) from simulated seawater have made this a potential adsorbent for industrial applications.

Ceria and zinc oxide catalyst were impregnated onto various oxide supports, namely Al2O3, TiO2 and SiO2, individually by deposition-coprecipitation method. The synthesized catalysts (CZA, CZS and CZT having supports Al2O3, TiO2 and SiO2, respectively) were characterized by X-ray diffraction (XRD), NH3- and CO2-temperature programmed desorption (TPD) and N2 adsorption. These catalysts were used for synthesis of dimethyl carbonate (DMC) from methanol and propylene carbonate in a batch reactor. CZS was found to have larger average grain size as compared to CZA and CZT. Composite oxides (catalysts) were found to contain individual phases of ZnO, CeO2 and some spinel forms of Zn, Ce along with their supports. CZS having highest basicity and surface area showed better catalytic activity as compared to CZA and CZT. Effect of reaction temperature and methanol/PC molar ratio on DMC yield was studied and a reaction mechanism has been discussed. Maximum DMC yield of 77% was observed with CZS catalyst at 170 °C with methanol/PC molar ratio of 10.

In the present study, synthesis of copper succinate nanoparticles by electrochemical process has been reported. Succinic acid was used as an electrolyte and copper sheets were used as electrodes. Product was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction measurements (XRD), thermal degradation analysis (TGA), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) surface area. Various characterization results showed that the nanoparticles obtained at different pHs had copper succinate along with copper hydroxide in different proportions. BET surface area analysis indicated that the nanoparticles were in mesoporous in nature and SEM analysis showed that nanoparticles were of cylindrical morphology.

In this study, oxidative-extractive desulfurization (OEDS) of liquid fuel has been studied using an ionic liquid prepared by coordination of dimethyl sulfoxide (DMSO) with ZnCl2. Synthetic model liquid fuel was prepared by dissolving dibenzothiophene (DBT) in iso-octane. In addition, actual diesel was also tested for total sulfur removal. Oxidation in the OEDS process was achieved by adding hydrogen peroxide and acetic acid to the mixture. Different parameters such as oil to ionic liquid ratio, oxidant to sulfur ratio and temperature were optimized. Kinetic study was performed at different temperatures so as to calculate the reaction rate constants. Optimized conditions were also tested for their applicability on actual diesel. At the optimized conditions (oxidant to sulfur ratio = 6, oil to ionic liquid ratio = 3 and temperature = 30°C), 78% sulfur removal was observed from model oil (initial sulfur concentration = 1,000 mg/L) and 65% sulfur removal was observed for actual diesel oil (initial sulfur concentration = 140 mg/L).

Herein, copper nanoparticles were synthesized using electrochemical method at pH 5, 6.5, 9.5 and 12.5 (coded as Cu5, Cu6.5, Cu9.5 and Cu12.5, respectively). Copper was used as electrode whereas 0.15 M oxalic acid in aqueous solution was used as an electrolyte. Effect of pH of the electrolyte solution on the morphological, structural and textural properties of prepared copper nonoparticles was studied. Prepared nanoparticles were characterized by X-ray crystallography, Field emission scanning electron microscope, transmission electron microscopy, thermogravimetric analysis, differential thermal analysis and textural analysis. The morphology and sizes of the nanoparticles prepared varied with the initial pH of the solution. Sizes of synthesized Cu particles were found to be in the range of 20 nm to 7 μm. All the particles were mesoporous in nature. Cu5 was found to contain 67% copper hydroxide and 33% copper oxalate whereas Cu6.5, Cu9.5 and Cu12.5 essentially consisted of copper hydroxide.

In the present study, Cu-Zn-Al (CZA) hydrotalcite catalysts prepared by the coprecipitation method and calcined at 300, 500 and 800 °C (named as CZA300, CZA500 and CZA800) were used for the synthesis of dimethyl carbonate (DMC) from methanol and propylene carbonate (PC) in a batch reactor. The physicochemical characteristics of the catalysts were analyzed by various methods such as X-ray diffraction (XRD), liquid nitrogen adsorption–desorption textural analysis, energy dispersive atomic spectra (EDAX), scanning electron microscope (SEM), Fourier transformation infrared (FTIR), and NH3- and CO2-temperature-programmed desorption (TPD). The average pore diameter of CZA300, CZA500, and CZA800 catalysts was found to be 55.6, 52.5, and 49.3 A, respectively. Pore volume distribution analysis revealed that the CZA300 and CZA500 have bimodal pore distribution with pores centered at 36 ± 1 A and 131 ± 2 A. CZA300 catalyst has the highest amount of basic sites in weak and strong regions whereas CZA500 catalyst has t...

Present study investigates mechanism of electrochemical (EC) oxidative degradation of p-nitrophenol (PNP) by ruthenium oxide coated titanium (Ti/RuO2) electrode. First, the process proficiency was determined in terms of chemical oxygen demand (COD), total organic carbon (TOC), current efficiency (CE) and specific energy consumption (SEC) under different experiment conditions of initial pH (pHo), current density (j), electrolyte concentration (m) and initial PNP concentration (Co). Maximum COD and TOC removal efficiencies of 98.9% and 81.9%, respectively, were obtained at j = 168.9 A/m2, pHo = 5.5, Co = 100 mg/L and m = 300 mg/L with SEC of 535.7 kW h/kg COD. PNP degradation mechanism has also been proposed on the basis of identification of intermediates by gas chromatograph coupled with mass spectrometry (GC/MS). Various intermediates such as quinine, benzoquinone, organic acids and small mineralization products were obtained during the EC treatment of PNP. PNP was found to be oxidized by both direct (hydroxyl radical generated via water electrolysis on anode surface) and indirect (via mediators, hypochlorous acid and active chlorine generated during chlorine oxidation in solution) EC oxidation. Kinetics of EC oxidation was represented by pseudo-first order kinetic model.

A series of cerium–lanthanum catalysts prepared using the co-precipitation method were investigated for transesterification of propylene carbonate (PC) with methanol to produce dimethyl carbonate (DMC). Synthesized catalysts were characterized by XRD, CO2- and NH3-TPD, N2 adsorption/desorption and SEM–EDX techniques. Studies were carried out to study the effect of reaction conditions such as methanol/PC molar ratio (4–12), catalyst dose (2–10 wt.% of PC), reaction time (2–10 h) and temperature (140–180 °C) on the DMC yield. Highest PC conversion and DMC yield of 72% and 74%, respectively, were observed with catalysts having a 1:4 Ce/La molar ratio.

In this study, treatment of simulated alkali decrement wastewater containing terephthalic acid (TPA) has been investigated by electrochemical treatment using stainless steel as electrode material. Five operational parameters, namely current density: 31.25–156.25 A/m 2 ; electrode gap: 1–2 cm; NaCl concentration: 0–2 g/l; pH: 7–12 and TPA concentration: 400–1000 mg/l were investigated for their effect removal efficiency. For a solution having 400 mg/l TPA and 560 mg/l chemical oxygen demand (COD), 72% COD removal and ≈77% TPA removal efficiency was obtained at optimal conditions of current density ≈ 118 A/m 2 , electrode gap = 1 cm and pH ≈ 7. Presence of ethylene glycol in the wastewater was found to decrease the treatment efficiency. Settling characteristics of the slurry obtained at optimum condition have been studied. Thermal decomposition of residues has also been investigated.

In the present study, catalytic wet peroxidation (CWPO) process has been applied for the degradation of nitrobenzene bearing wastewater using copper impregnated granular activated carbon with hydrogen peroxide as oxidant. Various catalysts were prepared by varying the Cu loading on activated carbon and these were characterized by N2 adsorption–desorption, Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FE-SEM), thermogravimetric analysis (TGA), temperature programmed reduction (TPR) and UV–visible diffuse reflectance spectra (UV-DRS). Effect of parameters such as copper loading, pH, catalyst dose, hydrogen peroxide dose and temperature were explored on nitrobenzene and total organic carbon (TOC) removal. TOC removal of 89% was achieved after 4 h treatment at optimum condition of Cu loading = 2.5 wt%, pH ≈ 3.0, catalyst dosage = 0.25 g/l, oxidant dosage = 4.5 (moles of oxidant/moles of NB) and temperature = 55 °C.

In the present study, photocatalytic oxidation of dye bearing wastewater has been done using iron doped zinc oxide (Fe/ZnO) photocatalyst. Various photocatalysts were synthesized by solution combustion synthesis method, and their structural, morphological, and optical properties were studied using N2 adsorption–desorption, Fourier transform infrared spectroscopy, X-ray diffractometer, thermogravimetric analysis, field emission scanning electron microscope, transition electron microscope, and UV–visible diffuse reflectance spectra. Effect of various parameters such as the amount of iron doped, calcination temperature, calcination time, pH of the dye solution, catalyst dose, hydrogen peroxide dose, reaction temperature, and initial concentration of the dye solution were optimized. At optimum conditions, more that 71% color removal, 94% dye degradation, and 41% total organic carbon removal was observed for acid red 1 dye solution having an initial concentration of 50 mg/L and initial color of 2730 Pt:Co units.

In the present investigation, oxidation of furfural was carried out using alum-impregnated activated alumina, which led to the formation of 2-furancarboxylic acid (furoic acid). Operational parameters such as catalytic ratio were varied from 1 to 9%, temperature from 40 to 70°C, initial concentration from 0.1 to 0.5 m and time from 0.5–7.5 h, and were optimized using Box–Behnken design. The Fisher F-value of 55.10 confirmed that the second-order regression model used for prediction of results was satisfactory. By using the reaction scheme proposed, rate constants at various reaction temperatures were determined. Activation energy and frequency factor corresponding to the reaction were also calculated.

The modeling study on simultaneous adsorption of three binary systems (nitrobenzene–aniline (NI–AN), nitrobenzene–phenol (NI–PH) and phenol–aniline (PH–AN)) onto granular activated carbon (GAC) in aqueous solution were performed at 30 °C by conducting batch experiments. The single solute equilibrium adsorption data of nitrobenzene (NI), aniline (AN) and phenol (PH) were fitted with Langmuir, Freundlich and Redlich–Peterson model. The Redlich–Peterson and Freundlich model gave better fitting as compared to Langmuir model for individual adsorption. The binary adsorption data were examined and compared by using ideal adsorbed solution theory (IAST) and real adsorbed solution theory (RAST) models. IAST model didn’t provide an acceptable prediction of binary data except for low liquid concentration levels, as it undervalued AN and PH adsorption capacity and overvalued NI adsorption capacity. This is due to the non-ideality of binary mixtures at high concentration levels in the solution. The RAST model gave an excellent prediction of binary adsorption experimental data, thus it can be used as a reliable model for the design of industrial adsorption equipment .

In this study, various copper loaded SBA-15 catalysts were synthesized by an impregnation method and characterized by UV–visible DRS, NH3-TPD and TGA. The synthesized catalysts were used for the catalytic wet peroxidation (CWPO) of 2-picoline in aqueous solution using hydrogen peroxide as an oxidant. Copper loading on SBA-15 enhanced the surface acidity by the generation of Lewis acid sites. Effects of various operating parameters such as initial pH, catalyst dosage, hydrogen peroxide dosage, initial 2-picoline concentration, and temperature have been investigated. At the optimum conditions of pH = 6, catalyst dosage = 0.5 g/L, stoichiometric ratio of H2O2/picoline = 1.3 (i.e., molar ratio of H2O2/picoline = 20.15) and temperature = 338 K, more than 99% 2-picoline removal efficiency was observed for a solution containing 100 mg/L of 2-picoline by 5%Cu loaded SBA-15. Furthermore, the CWPO process was well-described by a two-step pseudo-first-order kinetic model. The power law model well described the depen...

This article provides the brief overview on effect of dopant on the performance of zinc oxide (ZnO) as photocatalysts for the degradation of dye wastewaters. ZnO itself is a semi conductor having wide band gap (3.37eV), thus requiring high energy to work as a photocatalyst. To decrease the band gap or to alter its requirement of high energy from light sources like UV to visible (solar), surface modification or doping of ZnO is necessary. This paper discusses how dopant modifies the characteristics of ZnO which helps in degradation of dyes in colored wastewaters.

Cerium supported SBA-15 (Ce/SBA-15) was synthesized by two-step synthesis method in acidic medium. It was further characterized by various characterization techniques such as X-ray diffraction, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy and N2 adsorption-desorption pore size distribution analysis. The Ce/SBA-15 showed highly ordered meso-structure with pore diameter≈70-100Ǻ and pore volume≈0.025cm(3)/g. Ce/SBA-15 was further evaluated as a catalyst for the oxidation of highly toxic and non-biodegradable material, pyridine, by catalytic wet-peroxidation method. The effects of various operating parameters such as catalyst dose (0.5-6g/l), stoichiometric ratio of H2O2/pyridine (1-6), initial pyridine concentration (50-800mg/l) and temperature (313-358K) have been evaluated and optimized. Ce/SBA-15 showed stable performance during reuse for six cycles with negligible cerium leaching. Kinetic and thermodynamic parameters and operation cost have also been determined.

In this study, Cu-loaded Santa Barbara amorphous (SBA)-15 catalysts were synthesized by impregnation method and further used for catalytic wet peroxidation (CWPO) of pyridine from aqueous solution using hydrogen peroxide as oxidant. The synthesized catalysts have been characterized by Brunauer–Emmett–Teller surface area: temperature-programmed reduction, H2-chemisorption, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. Characterization results indicate good dispersion of Cu species inside the porous structure of SBA-15. The effect of various parameters such as Cu loading on SBA-15, pH, catalyst dose, H2O2 concentration, and temperature have been studied for their effect on CWPO of pyridine. More than 97% pyridine removal and 92% total organic carbon removal was achieved at optimum condition. Cu/SBA-15 showed stable performance during reuse for six cycles with negligible copper leaching. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2577–2586, 2013

The present paper reports kinetic studies of the adsorption of aniline (AN), phenol (P), 4-chlorophenol (CP) and 4-nitrophenol (NP) from aqueous solution onto granular activated carbon (GAC). In FTIR spectral analysis, the transmittance of the peaks gets increased after the loading of AN, P, CP and NP signifying the participation of these functional groups in the adsorption and it seems that the adsorption of AN, P, CP and NP is chemisorptive in nature. The rates of adsorption were found to obey a pseudo-second order model and that the dynamics of AN, P, CP and NP adsorption are controlled by a combination of surface and pore diffusion. The diffusion coefficient were of the order of 10-10 m2 s-1. Thermal desorption at 623 K was found to be more effective than solvent desorption. GAC performed well for at least five adsorption-desorption cycle, with continuous decrease in adsorption efficiency after each thermal desorption. Owing to its relative high heating value, the spent GAC can be used as co-fuel for the production of heat in a boiler or a furnace.

Pure mesoporous nanosized ZnO samples have been synthesized by combustion synthesis method using different type of fuels such as citric acid, dextrose, glycine, oxalyl dihydrazide, oxalic acid, and urea. All these samples were found to have the standard hexagonal wurtzite structure with the lattice constants a and c having values 3.25 A and 5.21 A, respectively. The diffuse reflectance spectra of the prepared samples have shown the maximum absorption of light in the UV region stating that these catalysts can be used as photocatalysts. The BET surface area measurements of the prepared catalysts were found to vary according to the equivalence ratio. The presence of pronounced hysteresis in N2 adsorption–desorption isotherm curves indicated the three-dimensional network arrangement of pores in the ZnO samples prepared using dextrose and urea as fuels. The photodegradation ability of the various synthesized photocatalysts was tested for the photodegradation of an azo dye, namely, orange G dye solution. ZnO ph...

In the present paper, the removal of aniline by adsorption process onto granular activated carbon (GAC) is reported from aqueous solutions containing catechol and resorcinol separately. The Taguchi experimental design was applied to study the effect of such parameters as the initial component concentrations (C(0,i)) of two solutes (aniline and catechol or aniline and resorcinol) in the solution, temperature (T), adsorbent dosage (m) and contact time (t). The L27 orthogonal array consisting of five parameters each with three levels was used to determine the total amount of solutes adsorbed on GAC (q(tot), mmol/g) and the signal-to-noise ratio. The analysis of variance (ANOVA) was used to determine the optimum conditions. Under these conditions, the ANOVA shows that m is the most important parameter in the adsorption process. The most favourable levels of process parameters were T = 303 K, m = 10 g/l and t = 660 min for both the systems, qtot values in the confirmation experiments carried out at optimum conditions were 0.73 and 0.95 mmol/g for aniline-catechol and aniline-resorcinol systems, respectively.

The present paper reports isotherm, thermodynamic, and disposal studies for the adsorption/desorption of catechol (C) and resorcinol (R) from aqueous solution onto/from granular activated carbon (GAC). Isotherm data were generated for C and R solutions having initial concentrations of C and R in the range of (0.18 to 9.08) mmol·L−1 for the GAC dosage of 10 g·L−1 at temperatures of (288, 303, and 318) K. The adsorption of C and R onto GAC was favorably influenced by an increase in temperature. Equilibrium data were well-represented by the Tempkin isotherm model. Values of the change in entropy (ΔS0), heat of adsorption (ΔH0), and Gibbs energy (ΔG0) were determined. The desorption of C and R from GAC was studied by various solvents and a thermal desorption method. NaOH was found to be a better eluant for the desorption of C and R with a maximum desorption efficiency of 10.1 % and 11.4 %, respectively. Thermal desorption at 623 K was found to be better as compared to solvent desorption. GAC worked well for a...

The present study deals with the removal of phosphates from aqueous solution using activated carbon developed from coir pith. Batch adsorption experiments were performed to delineate the effect of initial pH, contact time, adsorbent dose and temperature on the removal of phosphates by coir-pith activated carbon (CAC) (activated by H2SO4). The removal was found to be maximum in the pH range of 6–10. The kinetics of adsorption showed that the phosphate adsorption onto CAC was a gradual process with a quasi-equilibrium being attained in 3 h. The adsorption equilibrium data followed the Temkin isotherm. Thermodynamic parameters such as ΔG o , ΔH o , and ΔS o were evaluated by applying the Arrhenius and van't Hoff equations, and it was found that the adsorption of phosphate on CAC was spontaneous and endothermic.

Oxygen is the most essential requirement for aerobic bioprocesses. The microbial growth in a bioreactor depends upon the oxygen transfer rate (OTR). The OTR is widely used to study the growth behavior of microbial and plant cell cultures. The mass transfercoefficient(kLa)determinesthemagnitudeoftheOTR.Therearemanytechniquesformeasuringoxygenconcentration andOTRinbioreactors.Zirconia,electrochemical,infrared,ultrasonicandlasercellsareusedtomeasureoxygenconcentration in the liquid medium. Optical sensors are better alternatives to measure oxygen concentration in small bioreactors. Sulfite oxidation and gassing-out methods with a Clark-type electrode have been used for OTR measurements in bioreactors. Many new novel techniques have evolved recently for intermittent and continuous online measurement of OTR/kLa in various types ofbioreactors.Thepresentpapergivesanoverviewofvariousmeasurementtechniquesandtheirlimitationsand/orsuitability for measurementof OTR/kLa in various kinds of bioreactors, especially small bioreactors. c � 2009 Society of Chemical Industry

The present study deals with the competitive adsorption of cadmium (Cd(II)) and nickel (Ni(II)) ions from aqueous solution onto rice husk ash (RHA). Non-competitive Redlich–Peterson (R–P) and Freundlich models represent the single metal ion equilibrium sorption data. The adsorption capacities for the binary mixtures–RHA system are in the order Ni(II) > Cd(II). The combined equilibrium sorption of Cd(II) and Ni(II) ions onto RHA is found to be antagonistic in nature and the extended Freundlich model was found to best represent the binary equilibrium isotherm data.