Reduced graphene oxide coated graphite electrodes for treating Reactive Turquoise Blue 21 rinse water using an indirect
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Reduced graphene oxide coated graphite electrodes for treating Reactive Turquoise Blue 21 rinse water using an indirect electro‑oxidation process Naresh R. Vaghela1 · Kaushik Nath2 Received: 27 August 2020 / Accepted: 14 October 2020 © Springer Nature Switzerland AG 2020
Abstract The present study deals with the decolourization of synthetic Reactive Turquoise Blue 21 (RTB21) dye-based model wastewater using an indirect electro-oxidation process and enhanced by modified graphite electrodes. Graphene oxide (GO) was successfully synthesized and deposited on the surface of pre-treated graphite electrodes. It was further reduced to form reduced graphene oxide (rGO). The resultant newly developed anode electrodes were designated as (Gr)0, (rGO/ Gr)1, and (rGO/Gr)2 and used for the treatment of wastewater. Electrodes, thus developed, were characterized using Fourier-transform infrared spectroscopy, X-ray diffractions, Field emission scanning electron microscopy, and Contact angle (CA). The effect of process parameters such as initial pH, current density, electrolyte concentration, and temperature on the performance of novel anode electrodes was investigated. The colour removal efficiency was increased significantly almost 25.80% in the presence of a modified electrode with the highest efficiencies of about 96.69% in a natural pH environment, 200 A/m2, 2 g/L NaCl concentration, 30 °C temperature, and 15 min process time for 50 ppm RTB21 dye concentration for (rGO/Gr)2 electrode. The RTB21 decolourization by indirect electro-oxidation process follows the pseudo-first-order kinetics, and the activation energy was estimated to be 23.42 kJ/mol. The stability of (rGO/ Gr)2 electrode was also examined. The rGO coated electrode was a superior electrode for the indirect electro-oxidation process, giving enhanced colour removal (%). Keywords Graphene oxide · Reduced graphene oxide · Wastewater · Indirect electro-oxidation process
1 Introduction Discharge of rinse water associated with industrial dyeing operations poses a serious challenge towards its efficient reclamation. Annually 280,000 tons dyes are discharged into water bodies worldwide, out of which around 8000 tons comprise of reactive dyes with extremely high colour fastness, chemical stability, and resistance towards oxidation. Several physico-chemical methods for treating dye wastewater are available; however, most of these systems seem to be plagued with low practical efficiency
or low benefit–cost ratio. Common wastewater treatment techniques include adsorption [1], chemical coagulation [2], electrocoagulation [3], biological process [4], Fenton process [5], membrane filtration [6], and so on. But the issues of disposal of copious amounts of coloured sludge, membrane fouling, regeneration of spent adsorbents, equilibrium limitation, and many others render most of these processes unfeasible options. Another key problem with most of the approaches mentioned earlier is versatility for removing all classes of dyes. Adsorption suffers from expensive adsorbent regeneratio
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