Ganapathy Sozhan

Remediation of phosphate-contaminated water by electrocoagulation with aluminium, aluminium alloy and mild steel anodes.

The present study provides an electrocoagulation process for the remediation of phosphate-contaminated water using aluminium, aluminium alloy and mild steel as the anodes and stainless steel as the cathode. The various parameters like effect of anode materials, effect of pH, concentration of phosphate, current density, temperature and co-existing ions, and so forth, and the adsorption capacity was evaluated using both Freundlich and Langmuir isotherm models. The adsorption of phosphate preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules. The results showed that the maximum removal efficiency of 99% was achieved with aluminium alloy anode at a current density of 0.2 A dm(-2), at a pH of 7.0. The adsorption process follows second-order kinetics.

Effects of alternating and direct current in electrocoagulation process on the removal of cadmium from water

In practice, direct current (DC) is used in an electrocoagulation processes. In this case, an impermeable oxide layer may form on the cathode as well as corrosion formation on the anode due to oxidation. This prevents the effective current transfer between the anode and cathode, so the efficiency of electrocoagulation processes declines. These disadvantages of DC have been diminished by adopting alternating current (AC) in electrocoagulation processes. The main objective of this study is to investigate the effects of AC and DC on the removal of cadmium from water using aluminum alloy as anode and cathode. The results showed that the removal efficiency of 97.5 and 96.2% with the energy consumption of 0.454 and 1.002 kWh kl(-1) was achieved at a current density of 0.2A/dm(2) and pH of 7.0 using aluminum alloy as electrodes using AC and DC, respectively. For both AC and DC, the adsorption of cadmium was preferably fitting Langmuir adsorption isotherm, the adsorption process follows second order kinetics and the temperature studies showed that adsorption was exothermic and spontaneous in nature.

Studies Relating to Removal of Arsenate by Electrochemical Coagulation: Optimization, Kinetics, Coagulant Characterization

The present investigation aims to remove arsenate [As(V)] by electrochemical coagulation using mild steel as anode and cathode. The results showed that the optimum removal efficiency of 98.6% was achieved at a current density of 0.2 A dm−2, at a pH of 7.0. The effect of current density, solution pH, temperature, co-existing ions, adsorption isotherm, and kinetics has been studied. Kinetics reveals that the removal of arsenate by electrochemical coagulation is very rapid in the first 15 min and remains almost constant with the progress of reaction. The adsorption kinetics obeys the second-order rate expression. An equilibrium isotherm was measured experimentally and the results were analyzed by Langmuir, Freundlich, Dubinin- Redushkevich, and Frumkin using the linearized correlation co-efficient. The characteristics parameters for each isotherm were determined. The Langmuir adsorption isotherm was found to fit the equilibrium data for arsenate adsorption. Temperature studies showed that the adsorption was endothermic and spontaneous in nature.

Adsorption of herbicide 2-(2,4-dichlorophenoxy)propanoic acid by electrochemically generated aluminum hydroxides: an alternative to chemical dosing

This research article presents an in situ electrosynthesis of aluminum hydroxides by anodic dissolution of sacrificial aluminum anode and their application towards the adsorption of herbicide 2-(2,4-dichlorophenoxy)propanoic acid (2,4-DP) from aqueous solution. Different sacrificial anode material like iron, magnesium, zinc and aluminum are tested and stainless steel is used as the cathode. The optimization of different experimental parameters like current density, pH, temperature and inter-electrode distance on the adsorption of 2,4-DP was carried out. The results showed that the maximum removal efficiency of 93.0% was achieved with aluminum as sacrificial anode at a current density of 0.10 A dm−2 and pH of 7.0. The adsorption of 2,4-DP preferably followed the Langmuir adsorption isotherm. The adsorption kinetic studies showed that the adsorption of 2,4-DP was best described using the second-order kinetic model. Thermodynamic parameters indicates that the adsorption of 2,4-DP on aluminum hydroxides was feasible, spontaneous and endothermic.

Simultaneous removal of Co, Cu, and Cr from water by electrocoagulation

This study provides an electrocoagulation process for the removal of metals such as cobalt, copper, and chromium from water using magnesium as anode and galvanized iron as cathode. The various parameters like pH, current density, temperature, and inter electrode distance on the removal efficiency of metals were studied. The results showed that maximum removal efficiency was achieved for cobalt, copper, and chromium with magnesium as anode and galvanized iron as cathode at a current density of 0.025 A dm−2 at pH 7.0. First- and second-order rate equations were applied to study adsorption kinetics. The adsorption process follows second-order kinetics model with good correlation. The Langmuir and Freundlich adsorption isotherm models were studied using the experimental data. The Langmuir adsorption isotherm favors monolayer coverage of adsorbed molecules for the adsorption of cobalt, copper, and chromium. Temperature studies showed that adsorption was endothermic and spontaneous in nature.

Novel cross-linked anion exchange membrane based on hexaminium functionalized poly(vinylbenzyl chloride)

Hydroxide anion exchange membranes (HAEMs) are of recent research interest, since these membranes can potentially replace the noble metal catalysts used in electrochemical energy conversion systems such as fuel cells and electrolysers. The conductivity and stability of state-of-the-art anion exchange membranes are far below those required for real applications. Herein, we report a novel anion exchange membrane based on aminated and cross-linked poly(vinylbenzyl chloride) prepared by an easy, viable synthetic route. β-Hydrogen free, multi-nitrogen containing ‘hexamethylenetetramine’ was used and explored as an amination/cross-linking agent for the first time in this study. FT-IR and 1H-NMR analysis results confirmed the successful quaternization of poly(vinylbenzyl chloride) with hexamine. TGA results showed the degradation temperature of the quaternized polymer is as high as 160 °C. AFM analysis revealed that the membrane possesses phase separated morphology with hydrophobic and hydrophilic domains. The ionic conductivity of the membranes increased when the amine to polymer ratio was increased from 0.2 to 0.33, and the highest ionic conductivity achieved was 6.8 × 10−3 S cm−1. The membrane has good chemical and alkaline stability which strongly suggests that the membrane would be a promising material for electrochemical energy conversion systems.

Studies on the removal of arsenate from water through electrocoagulation using direct and alternating current

Abstract Using alternating current in an electrocoagulation process offers an alternative to conventional electrocoagulation processes, where the direct current is used. The main objective of the present investigation is to study the effects of alternating current (AC) and direct current (DC) on the removal efficiency of arsenate by electrocoagulation using magnesium as anode and cathode. The effect of current density, solution pH, temperature, co-existing ions, adsorption isotherm and kinetics has been studied. The optimum removal efficiency of 98.3% and 97.9% was achieved with the energy consumption of 0.724 and 1.035 kWh/m3 at a current density of 0.2 A/dm2, at pH of 7.0 for AC and DC, respectively. The adsorption of arsenate preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules for both AC and DC. The adsorption process follows second-order kinetics model with good correlation coefficient. Temperature studies showed that adsorption was endothermic and sp...

Eco-friendly and facilely prepared silica modified amorphous titania (TiO2–SiO2) electrocatalyst for the O2 and H2 evolution reactions

An eco-friendly silica modified amorphous titania (TiO2–SiO2) electrocatalyst is prepared. This silica modified amorphous titania (TiO2–SiO2) composite material is prepared by facile spurting of silica (obtained from a sustainable resource) over a titanium plate and identified as an active electrocatalyst for O2 and H2 evolution by water oxidation. The prepared composite shows a maximum current density of 12 mA cm−2 at 2 V (versus RHE) in 1 M KOH electrolyte. This is because the semiconductor heterostructure of the structurally and chemically dissimilar amorphous TiO2–SiO2 composite introduces new collective electronic states with improved electrical conductivity, with a decrease in the work function. The catalytic activity is found to be stable in continuous operation for about 10 h. The physicochemical characterization of the electrocatalyst was carried out using scanning electron microscopy, energy dispersive X-rays, X-ray diffraction, X-ray photoelectron spectra, and electron paramagnetic resonance and the work function was examined by a Scanning Kelvin Probe. Because of the simple, cheap, and scalable preparation procedure, the electrocatalyst is highly promising for practical low cost and high technology applications. Interestingly, the system is active in the oxygen and hydrogen evolution reactions, leading to a promising bifunctional electrocatalyst.

Sulfonated Polystyrene-Block-(Ethylene-Ran-Butylene)-Block-Polystyrene (SPSEBS) Membrane for Sea Water Electrolysis to Generate Hydrogen

Sea water oxidation is one of the promising ways to produce hydrogen since it is available in plentiful supply on the earth. However, in sea water electrolysis poisonous chlorine evolution is the most favored reaction over oxygen evolution at the anode. In this work, study has been focused on the development of electrode materials with high selectivity for oxygen evolution reaction over chlorine evolution. We employed perm selective membrane i.e. sulfonated polystyrene-block-(ethylene-ran-butylene)-block-polystyrene (SPSEBS) which electrostaticlly repels the chloride ion (Cl-) to the electrode surface and thereby enhances the oxygen evolution and reduces the chlorine evolution at the anode. The electrochemical behavior of both modified and bare IrO2 electrodes were characterized using polarization studies and the gas evolution efficiencies are calculated based on bulk electrolysis method. The surface morphology of the electrode was analyzed before and after electrolysis using scanning electron microscope (SEM). The results suggest that the nearly 95% oxygen evolution efficiency could be achieved when the surface of IrO2/Ti electrode was modified with perm selective membrane.

Quaternized poly(styrene-co-vinylbenzyl chloride) anion exchange membranes: role of different ammonium cations on structural, morphological, thermal and physio-chemical properties

Different ammonium cation containing anion exchange membranes are investigated in this study. Anion exchange polymers have been prepared from styrene and vinylbenzyl chloride monomers by free radical polymerization, followed by a quaternization process. Amines such as trimethylamine (TMA), tris(trimethylsilyl)amine (TTSA), hexamine (HMA), N,N,N′,N′-tetramethyl hexanediamine (TMHDA), and N,N,N′,N′-tetramethyl ethylenediamine (TMEDA) are used in this study. FT-IR and 13C-NMR results confirm the successful quaternization of the co-polymers with different amines. TGA results reveal that the thermal stability of the anion exchange polymers is as high as 165 °C. SEM images show that the membrane morphological features are tuned by the different ammonium cations. The ionic conductivity, ion-exchange capacity and water uptake values of the membranes also change with the different ammonium cations, which reveal the distinctive roles of the different amines used. Among the membranes, the membrane containing the trimethylammonium (TMA+) cation demonstrates the highest ionic conductivity, ion-exchange capacity and water uptake. On the other hand, the hexaminium (HMA+) containing anion exchange membrane displays the lowest ionic conductivity, ion-exchange capacity and water uptake due to the highly entangled structure of the polymer caused by the cross-linking of the polymer units.