G. Bhaskar Raju

Anodic oxidation of ketoprofen—An anti-inflammatory drug using boron doped diamond and platinum electrodes

The mineralization of ketoprofen (KP) by anodic oxidation was studied by employing boron doped diamond (BDD) and Pt electrodes. The redox behavior of KP molecule, fouling of electrodes, generation of oxygen and active chlorine species were studied by cyclic voltammetry. The effect of electrolyte, pH of aqueous medium and applied current density on the mineralization behavior of KP was also investigated. The degradation and mineralization were monitored by UV-vis spectrophotometer and total organic carbon analyzer, respectively. The results were explained in terms of in situ generation of hydroxyl radical (OH), peroxodisulfate (S(2)O(8)(2-)), and active chlorine species (Cl(2), HOCl, OCl(-)). The physisorbed OH on BDD was observed to trigger the combustion of KP in to CO(2) and H(2)O. The poor mineralization at both BDD and Pt anodes in the presence of NaCl as supporting electrolyte was ascribed to the formation of chlorinated organic compounds which are refractory. Complete mineralization of KP molecule was achieved using Na(2)SO(4) as supporting electrolyte.

Electrochemical oxidation of tannic acid contaminated wastewater by RuO2/IrO2/TaO2‐coated titanium and graphite anodes

The electrochemical oxidation of tannic acid contaminated wastewater by RuO2/IrO2/TaO2‐coated titanium and graphite anodes has been investigated. The effect of the process variables, such as initial pH, current density, processing time, concentration of the electrolyte and anode materials, on the degradation of tannic acid was studied. During the various stages of electrolysis, parameters such as COD, chloride ion concentration and UV–Vis spectra were examined and discussed. The maximum chemical oxygen demand (COD) removal efficiency of 94% was achieved at pH 5, operated at the current density of 8.10 mA/cm2, electrolyte (NaCl) concentration of 0.1 M and at 60 min of electrolysis using graphite anodes. The experimental results showed that the electrochemical oxidation process could effectively reduce the COD from the tannic acid contaminated wastewater. An acidic pH showed the maximum reduction of COD compared with neutral and alkaline pH. Increase in current density, process time and electrolyte (NaCl) concentration with the increase in COD removal. Graphite anodes showed maximum removal of COD and better tannic acid degradation when compared with RuO2/IrO2/TaO2‐coated titanium anodes.

Electroflotation of chalcopyrite fines with sodium diethyldithiocarbamate as collector

Abstract Electroflotation tests were conducted with a chalcopyrite fines-sodium diethyldithiocarbamate system with normal variables such as effect of concentration, pH of the collector and conditioning time, separately with oxygen and hydrogen bubbles generated electrolytically. Studies were attempted to check the effect of pH changes and electrolyte gases on the surface products. The surface products were extracted with carbon tetrachloride and analysed by UV-visible and I.R. spectrophotometric methods. It was found from the results that the qualitative nature of the surface product was unaffected by the above parameters.

Electro-flotation of chalcopyrite fines

Abstract Electro-flotation tests were conducted on chalcopyrite particles with a modified Hallimond tube designed for electro-flotation, using platinum anode—copper cathode and graphite anode—copper cathode systems. Flotation tests were carried out for fines of chalcopyrite of size below 20 microns with potassium ethylxanthate as collector. Studies were done on flotation with hydrogen and oxygen separately with the usual variables. Dissolution of chalcopyrite at various current densities, with reagent at optimum conditions and without reagent was also studied. It is observed that electro-flotation particularly with oxygen, is effective in the flotation of fine particles of chalcopyrite.

Comparative Study of Electrocoagulation and Electrooxidation Processes for the Degradation of Ellagic Acid From Aqueous Solution

A comparative study of electrocoagulation and electrooxidation processes for the degradation of ellagic acid from aqueous solution was carried out. For the electrocoagulation process, metallic iron was used as electrodes whereas graphite and RuO2/IrO2/TaO2 coated titanium electrodes were used for the electrooxidation processes. The effect of the process variables such as initial pH, concentration of the supporting electrolyte, applied current density, electrolysis time, and anode materials on COD removal were systematically examined and discussed. Maximum COD removal of 93% was obtained at optimum conditions by electrocoagultion using an iron electrode. The ellagic acid was degraded completely by electrooxidation using graphite electrodes under the optimum conditions. During electrooxidation, the chloride ion concentration was estimated and the effect of the Cl− ion was discussed. The finding of this study shows that an increase in the applied current density, NaCl concentration, and electrolysis time enhanced the COD removal efficiency. The UV–Vis spectra analysis confirms the degradation of ellagic acid from aqueous solution.

Mechanistic insight into active chlorine species mediated electrochemical degradation of recalcitrant phenolic polymers

Degradation of recalcitrant phenolic syntan by electro-oxidation was investigated. The kinetics of degradation of phenolic syntan was followed both in terms of TOC and COD measurements. The generation of oxidants such as Cl2, HOCl and free radicals of oxychloride in the presence of NaCl electrolyte was also monitored and their role in the oxidation of organics was discussed. The generation of ˙ClO free radicals was ascertained by electron spin resonance (ESR) spectroscopy coupled with the spin trapping technique. The effect of pH, electrolyte concentration and current density on the degradation of phenolic syntan was discussed. Also, the current efficiency (CE) and energy consumption (EC) were estimated. It was observed that the oxidation of phenolic syntan was proportional to the current density and electrolyte concentration. The kinetics of the degradation of phenolic syntan was found to follow first order rate equation with an R2 value of 0.9966. The intermediate compounds formed during electrooxidation were characterised using AOX, FT-IR and NMR techniques and the degradation pathway proposed. These results clearly suggest the effectiveness of the electrochemical technique for the treatment of wastewater containing a high concentration of phenolic syntan.

Degradation of Tannic Acid Using TiO2 Nanotubes as Electrocatalyst

Structured TiO2 nanotubes were grown on 2 mm thick titanium sheet by anodization of titanium in ethylene glycol medium containing 0.025 M NaF. The morphology of TiO2 nanotubes (TNT) was characterized using field emission scanning electron microscope. The potential of TNT as anode and also as photocatalyst for the degradation of tannic acid was studied. The mineralization of tannic acid was measured in terms Total Organic Carbon (TOC). Only 50% of TOC could be removed by exposing the tannic acid solution to UV-radiation (photolysis), whereas it was improved to 70% by electrooxidation (EO) using TNT as anode. Maximum degradation of 83% was achieved when electrooxidation was conducted under the influence of UV-radiation (photoelectrocatalytic process (PEC)). Among the electrolytes tried, Na2SO4 was observed to be very effective for the degradation of tannic acid. The kinetics of tannic acid degradation by photoelectrocatalytic process was found to follow zero-order rate expression.

Degradation of Tannic Acid Powered by TiO2 Nanoparticles

The wastewater from the coir, pharmaceutical, leather, paper and pulp industries is contaminated with water-soluble poly phenolic compounds (tannins). Among various tannins, tannic acid is a typical hydrolysable tannin prevalent in wastewater. The degradation of tannic acid using TiO2 nanoparticles as photocatalyst was investigated. The effect of catalyst concentration, pH of aqueous suspension and also electron acceptors such as hydrogen peroxide (H2O2) and ozone (O3) on the degradation of tannic acid was studied. The degradation of tannic acid was found to be more efficient and complete in the presence of UV/TiO2/O3 compared to UV/TiO2/H2O2. The kinetics of degradation was observed to follow first order rate equation which indicates that the mineralization process is diffusion controlled.

Studies on the Zetapotential of Calcite/p-Sulfonato-calix[4,8]arenes

Zeta potential of calixarenes has been reported for the first time. The water-soluble calixarenes has been used as dispersion media in solid/liquid interface. p-sulfonato-calix[4]arene (PSC4) and p-sulfonato-calix[8]arene (PSC8) were synthesized and characterized by FTIR, NMR, mass spectrometry, and HPLC techniques. It was proved that the zeta potential is a fast and simple measurement to know the adsorption behavior of sufonato calixarnes on calcite. The chemisorption of p-sulfonato-calix[n]arene was confirmed by shift in iso electric point, adsorption studies and FTIR. The calculated free energy of adsorption value and its sign suggests the chemical interaction between the calcite surface and p-sulfonato calix[4]and[8]arene.

Electrokinetic Behavior of Fluorite

The electrokinetic behavior of fluorite mineral was studied under various partical sizes and different concentrations of oleic acid at constant pH. The particle size has been reduced with an increase in activation time. The surface energies of milled fluorite minerals were calculated theoretically and experimentally. The zeta potential of the fluorite/water system has shifted to lower side with an increase in particle size. The isoelectric point (iep) of fluorite minerals has been shifted to lower side with increase in oleic acid concentration. This indicates the chemisorbed oleate formation on fluorite. A sharp decrease in zeta potential in the pH range of 6.5–8.4 and the decrease in calculated free energy of adsorption shows the formation of calcium dioleate precipitate on fluorite.