Regeneration of diclofenac-spent granular activated carbon by sulphate radical based methods: multi-response optimisation of adsorptive capacity and operating cost

Abstract

ABSTRACT In this study, regeneration of DCF-spent activated carbon by microwave (MW) activated persulphate (PS), (MW+PS) and PS alone was investigated. The regeneration processes were optimised to achieve high adsorptive capacity with low operating cost, simultaneously. Optimisation was carried out with Taguchi L9 experimental design. Optimum conditions determined for (MW+PS) process were found as PS dose of 0.3 g, MW power of 406 W, the regeneration time of 8 min and pH of 7, while the optimum conditions determined for PS processes were found as PS dose of 1.5 g PS, the regeneration time of 15 min and pH of 9. At optimum conditions, an adsorptive capacity of 9.8 mg DCF/g GAC with an operating cost of 0.020 €/g GAC and an adsorptive capacity of 5.0 mg DCF/g GAC with an operating cost of 0.077 €/g GAC were found for (MW+PS) and PS processes, respectively. ANOVA analysis found that the most effective parameter to the responses for both regeneration processes was the PS dose, and its effect was 43.5% and 72.5% for (MW+PS) and PS processes, respectively. The regenerated GAC after at least 6 regeneration cycles was found to have a capacity above the adsorptive capacity of the raw GAC.