Optimization of Electro-Charge Loading in Electrocoagulation Using Response Surface Methodology for the Abatement of Salicylic Acid from Wastewater

Abstract

The present investigation demonstrates a batch electrocoagulation (EC) process performance for the abatement of salicylic acid–laden wastewater. The electro-charge loading optimization was assessed using response surface methodology (RSM) with a central composite design (CCD) model. The EC at an optimum electro-charge loading of 20.69 Fm−3 in the presence of NaCl electrolyte with concentration of 1 g L−1 and a pH of 7.0, resulted in 88.38%±3.52% reduction of salicylic acid with an initial concentration of 50 mg L−1. The analysis of variance (ANOVA) and regression equation resulted in a p-value of <0.05, F-value of 113.65, and a unit value of desirability for the optimized model, suggesting the model is statistically significant. Moreover, at an optimum surface-to-volume ratio (S/V) of 6.8 m3 m−2, about 1.23 kWh m−3 of energy consumption was observed. Further, in the case of chemical coagulation, about 37%±2.2% removal efficiency of salicylic acid was obtained at an optimum pH and alum dose of 7.0 and 250 mg L−1, respectively. Also, the EC process demonstrated satisfactory performance during the treatment of real institutional wastewater spiked with 50 mg L−1 of salicylic acid by achieving 75.2%±5.7% removal efficacy at optimum operating conditions. Finally, the sludge characterization revealed the presence of metal hydroxide species [Al(OH)3] flocs, responsible for effectively adsorbing and separating salicylic acid molecules from wastewater.