A Comparative Study of Electrochemical Treatment of Para-Toluic Acid (p-TA) from Aqueous Solution: Process Optimization and Sludge Analysis

Abstract

The present study deals with the removal of para-toluic acid (p-TA) as well as chemical oxygen demand (COD) from synthetic solution. Pretreatment of aqueous solution was done by acid precipitation at different pH levels (3–6) and temperatures (15–60 °C). The pretreated solution was further treated by electrocoagulation (EC) and electro-Fenton (EF) treatment technologies using iron anode and graphite cathode. Optimization of various independent operating parameters viz. initial pH (1–9), current density (30.48–152.44 A/m2), electrolyte concentration (for EC) (0.03–0.07 mol/L), H2O2 concentration (for EF) (300–700 mg/L), and electrolysis time (10–90 min) was performed using central composite design (CCD) in response surface methodology (RSM). At optimum operating conditions, maximum removal percent of p-TA 64.83, 74.50; COD 61.27, 68.21; and energy consumption (kWh/kg COD removed) 69.71, 41.60 were obtained by EC and EF processes, respectively. In this study, it was observed that the EF process was more efficient than EC process based on percent removal of p-TA and COD with minimum energy consumption (E.consumption). Sludge obtained after EC and EF treatments was analyzed for various physicochemical characteristics like settling, point of zero charge, XRD, FTIR, SEM/EDX, and DTA/TGA.