The present contribution investigates the influence of Ruthenium oxide (RuO2) microstructure on titanium substrate for treating pharmaceutical effluent. RuO2/Ti electrodes were prepared at two different sintering temperatures, viz. 450°C and 550°C, and subjected to degradation studies on pharmaceutical effluent. Fourier transform Infrared spectroscopy (FT-IR) was used to analyze intermediates formed during degradation. The performance of these electrodes was presented and discussed based on sintering temperatures. Electrodes prepared at 450°C and 550°C gave 84% and 96% colour removal. Chemical Oxygen Demand (COD)removal was found to be 68% and 79% for the electrodes prepared at 450°C and 550°C, respectively. The surface morphology of these electrodes was identified and studied by Scanning electron Microscopy (SEM). X-ray diffraction (XRD) patterns showed the presence of anatase phase TiO2 at 550°C. The microstructural changes in sintering the catalytic coating caused a significant improvement in anode performance in electrodes sintered at 550°C. The electrodes are electrochemically active, stable and chemically inert under operating conditions.
Keywords: Pharmaceutical effluent; RuO2/Ti anode; Electrooxidation; Microstructure; X Ray Diffraction; Scanning Electron
Microscopy
Introduction：
Pharmaceutical industries produce a wide variety of products using both organic and inorganic substances as raw materials, thereby generating a large quantity of complex toxic organic liquid wastes with high concentrations of inorganic TDS. These wastes are highly toxic to biological life and are usually characterized by the high BOD, COD, and COD: BOD ratio. In addition, wastes from drug manufacture also contain toxic components including cyanide[1]. Ground water quality is disturbed by the penetration of pharmaceutical industry effluents. Advanced oxidation processes (AOPs), which rely on the generation of very reactive short-lived hydroxyl radicals have been attempted to decontaminate pharmaceutical wastewater. Electrooxidation is one of the recent techniques which have been used in the treatment of pharmaceutical wastewater in an effective manner [2-5]. Industrial use of dimensionally stable anodes (DSA) for wastewater treatment has led to technological solutions, thus reducing operational and investment costs [6,7]. Such DSA-type materials have been used for the oxidation of model aqueous solutions containing non-biodegradable organics, typically found in pharma effluents Recent DSA research emphasis focuses on titanium-based anodes coated with a variety of oxide materials such as IrO2, Ru2, and SnO2. DSA with RuO2–TiO2 coated titanium has been used widely and successfully as an anode for Chlor-alkali production and electro-oxidation of wastewater due to its good electrocatalytic activity. RuO2 is a good electrocatalyst for oxygen evolution, in spite of its limited service life [8]. The coating of RuO2 by thermal decomposition of the precursors such as RuCl3, can persist on titanium mesh surfaces for long durations and cause the activation of titanium anode through its pores. Surface activation by RuO2 can occur only if the coating is sufficiently porous for the diffusion of the ions involved during electro-oxidation. The coating also shows a high pseudo capacitance value due to the redox reactions of RuO2. At 400oC, the normal firing temperature of RuCl3 on titanium substrate, ruthenium penetrates deep into the bulk of the substrate and accumulates in the near-surface region. The chemical stability and the electrochemical properties of RuO2 layers are strongly dependent on their preparation process.
Vahidhabanu S, Abilash John Stephen, Ananthakumar S and Ramesh Babu B
The Ti/RuO2 system has received considerable attention due to its excellent stability, electrocatalytic properties, and prevention of Ti passivation by the oxide coating. A further advantage is a large number of Ru-oxidation states at the electrode surface in the potential region between the hydrogen evolution reaction, HER, and the oxygen evolution reaction, OER. The electrochemical oxidation of organic substances was attributed to OCl−, OH−, nascent oxygen, and other reactive [9].
Titanium-based anodes are unavoidable in the electrooxidation techniques. This type of anode is mainly coated with catalytic oxides such as Ruthenium oxide or iridium oxide to enhance the oxidation process of the anode [10,11]. The present work aims to study the effect of sintering temperature on RuO2 coated titanium mesh anodes by preparing RuO2 coating at two different temperatures. The coated electrodes are then employed to treat pharmaceutical effluents [12-14]. The results were obtained to elucidate the effect of RuO2 microstructural modifications over Ti substrate at different sintering temperatures of 450°C (Electrode A) and 550°C (Electrode B) on efficient electrooxidation performance.
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