Metin Gençten

A detailed investigation on electro-Fenton treatment of propachlor: Mineralization kinetic and degradation intermediates

In this study, electrochemical removal of propachlor from water has been investigated by electro-Fenton process which provides continuous electrochemical production of hydroxyl radical which is a highly oxidizing agent. This radical can react with propachlor unselectively and can oxidize it into carbon dioxide and water. Effects of applied current, catalyst (Fe2(SO4)3) and supporting electrolyte (Na2SO4) concentrations on the degradation rate of propachlor have been examined and determined as 200 mA, 0.20 mM and 25 mM, respectively. The oxidation reaction showed a second-order reaction kinetic with an absolute rate constant value of (3.6±0.2)×10(9) M(-1) s(-1) which was determined by competition kinetic experiments. Total organic carbon analysis was employed to follow the mineralization of propachlor. The total mineralization was completed in a seven-hour electrolysis at 300 mA indicating that the electro-Fenton process is very effective in the mineralization of propachlor in water. Oxidation of propachlor with hydroxyl radical led to the formation of intermediate species. Some of these species were detected and quantified by chromatographic and spectroscopic methods such as HPLC, GC-MS and IC. A plausible mineralization pathway for the electrochemical removal of propachlor was proposed based on the identified by-products.

Investigation of acid red 88 oxidation in water by means of electro-Fenton method for water purification

In this study, electro-Fenton method was applied to acid red 88 (AR88) containing aqueous solutions for the removal of it from water. The mineralization of AR88 has been achieved by oxidation with hydroxyl radicals. These radicals were produced simultaneously by the electro-Fenton method using an electrochemical cell including a carbon felt cathode and a platinum anode. Applied current and concentrations of catalyst and supporting electrolyte were optimized to obtain the best effective parameters of 500 mA, 0.1 mM and 75 mM, respectively. The absolute rate constant for the oxidation reaction of AR88 with hydroxyl radical was determined as (1.57 ± 0.06) x 10(10) M(-1) s(-1). Total organic carbon (TOC) analysis was performed to determine whether the organics were converted to carbon dioxide or not. A two-hour electrolysis at 500 mA is enough to remove 87% of initial TOC values of 0.25 mM AR88 solution. Electro-Fenton treatment of AR88 led to the formation of five aromatic intermediates, five short-chain carboxylic acids and three inorganic ions. Identified intermediates and complete mineralization of AR88 allowed us to propose a mineralization pathway for first time in the literature.

A performance comparison of protective silicate-coated lead and non-coated lead electrodes in various kind electrolytes of gel valve-regulated lead-acid battery

A novel silicate-based protective film was formed on negative electrodes and compared of the performance in various electrolyte systems of lead-acid batteries. The sodium silicate-based coating for the negative electrode component of a gel valve-regulated lead-acid (gel-VRLA) battery was applied for the first time in the literature. The battery system was produced by sodium silicate-coated negative electrodes and lead oxide positive electrodes in various kinds of electrolyte. Electrochemical characterization of cells and battery prototypes were done by cyclic voltammetric (CV) analysis, electrochemical impedance spectroscopic (EIS) analysis, and cyclic charge-discharge tests. The surface morphologies of silicate-coated electrodes were investigated by scanning electron microscopic analysis after cyclic voltammetric analysis and charge-discharge tests. The coating of silicate on the surface of negative electrodes increased the corrosion resistance of a VRLA battery according to the Tafel polarization curves. Indeed, sulfation on the negative electrode component of the battery have significantly reduced with silicate coatings of them. Besides, the prepared novel silicate-based protective film have increased the battery performance of a VRLA. Silicate-based coatings for electrodes can be used for industrial battery production for many different battery types due to their amazing anti-corrosion properties in acidic media.

Electrochemical formation of molybdenum phosphate on a pencil graphite electrode and its potential application for the detection of phosphate ions

The one-step electrochemical preparation of a molybdenum phosphate coated pencil graphite electrode was achieved in phosphoric acid and lithium molybdate solutions at room temperature. The electrodes were prepared by cycling the potential between −1.0 V and +1.9 V (vs. Ag/AgCl) in one-step. The surface morphology of the electrodes was investigated by scanning electron microscopic analysis. The chemical structure of the surface was determined with X-ray photoelectron spectroscopy and X-ray diffraction spectroscopy. The electrochemical behaviors of the electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The prepared electrodes were used for the detection of phosphate in soil samples. The molybdenum phosphate modified pencil graphite electrode showed excellent sensitivity for phosphate analysis with a relatively low limit of detection and a limit of quantification of 1.25 × 10−6 M and 4.15 × 10−6 M, respectively. The novel sensor described herein is economical, easy and environmentally-friendly to prepare, and can be used in many environmental analyses for the detection of phosphate with high sensitivity.