Degradation of diclofenac using palladized anaerobic granular sludge: Effects of electron donor, reaction medium and deactivation factors

Abstract

Biogenic nanopalladium (Bio-Pd) was formed by Anaerobic Granular Sludge (AGS). The Bio-Pd hosted in AGS (Pd-AGS) was used to degrade a pharmaceutical compound diclofenac (DCF) under the conditions of various electron donors, Pd loadings and reaction media. Results showed that hydrogen was the most effective electron donor for the Pd-AGS, followed by formate, glucose and acetate. The Pd-AGS was able to produce effective hydrogen/electron donors from organic compounds via microbial metabolism to initiate Pd activity. Over 96% of DCF (initial concentration of 20 mg L^-1) was removed using the Pd-AGS within 90 min, and a maximum specific activity K_obs of 1.53 L g^-1 min^-1 was obtained at 3.0 wt% Pd loading, in the presence of hydrogen. The Pd-AGS exhibited a relatively high activity in the medium of PBS or Na₂SO₄ (25 mM) at pH = 7-7.5, but lost activity in the medium of Na₂CO₃ (40 mM) or NaOH (40 mM). The Pd-AGS was more resistant to deactivation by chloride or sulphide comparing to free Pd nanoparticles. The Pd-AGS could reduce DCF and nitrate simultaneously with high nitrogen selectivity. The Pd-AGS, as a novel form of Pd catalyst with AGS, shows promise for applications in reducing chlorinated organic compounds in contaminated water.

Keywords: Anaerobic granular sludge; Biogenic nanopalladium; Diclofenac; Hydrodechlorination.