Treatment of synthetic catechol solution by electrocoagulation-magnetic granular activated pomegranate peel carbon: A cost-effective approach.

Abstract

The studies on purifying water and wastewaters contaminated with phenolic compounds have always been set up within recent years either full-scale or lab-scale experiments. In this research, treatment of the synthesized catechol (CC) solution was done by using magnetized granular activated pomegranate peel carbon (GAPPC) simultaneously with an electrocoagulation (EC) system for the first time. The experiments on both the EC-magnetic GAPPC and the magnetic GAPPC to find the optimum operating parameters like pH, contact time (CT), supportive electrolyte concentration, current densities (DC), adsorbent dosage, temperature to remove CC were conducted in batch-mode. The highest removal rate (88%) was achieved at pH = 6-8, CT = 30, supportive electrolyte = 0.25 g/L, DC = 0.5 A/m², magnetic GAPPC dosage = 0.25 g/L. Under this condition, the rate of anode dissociation was 2.9 mg/L as the produced coagulant, the used electrical energy was 3.5 kW h, and the produced sludge rate was not more than 220 mg/L. However, synergistic order to remove CC could be as EC-magnetic GAPPC > EC > > magnetic GAPPC. Chromatographic analysis suggested that benzoquinone could be regarded as EC degradation intermediate of CC and simple aliphatic acids as its semifinal oxidation products along with Fe-bonded complexes. Adsorption isotherm followed Freundlich model having higher R² representing multilayer adsorption. The adsorption kinetics investigation demonstrated that the pseudo-second-order model better fits the experimental data rather with higher R². The cost analysis revealed that treating aqueous CC solutions using EC-magnetic GAPPC does not cost more than $0.8. PRACTITIONER POINTS: Using simultaneously electrocoagulation and magnetic AC made by pomegranate peel is extremely cost-effective having high efficiency (88%) for removing CC. Benzoquinone is the intermediate of CC electrochemical degradation through EC-magnetic GAPPC treatment process, and formic and acetic acids, and Fe-bonded complexes as its semifinal and final products. Adsorption mechanism was multilayer following Freundlich isotherm model and kinetics adsorption was well-fitted with pseudo-second-order model. CC adsorption by magnetic GAPPC was a spontaneous and exothermal mechanism. The synergic order of EC-magnetite GAPPC was EC-magnetic GAPPC > EC > > magnetic GAPPC.