Regeneration of copper-loaded pine bark biochar using simultaneous bio-sulfide precipitation of copper

Abstract

This research investigated adsorption of copper from aqueous solution onto the pine bark biochar, removal of adsorbed copper by bio-sulfide precipitation, and simultaneous regeneration of pine bark biochar adsorbent. A sulfidogenic reactor was established and operated under anaerobic conditions. During the sulfidogenic phase, COD:SO42− was gradually increased from 24:1 to 4:1. Use of sulfide-rich effluent from bio-sulfide reactor at neutral pH yielded above 99% copper removal from the aqueous solution. In the experiment's second stage, pine bark biochar was prepared through slow pyrolysis at 650 °C from pine bark residue that had a carbon content of 81% and a surface area of 368 m2/g. This biochar was then used in subsequent experiments. Initially, copper was adsorbed onto the biochar under neutral pH at contact time of 6 h. Maximum biochar adsorption capacity of 106 mg/g of copper was obtained. Finally, biochar was regenerated by precipitating the adsorbed copper as copper sulfide using sulfide-rich effluent from the sulfidogenic reactor. Complete recovery of adsorbed copper from biochar as copper sulfide precipitates were obtained was also confirmed by EDX-SEM analysis of biochar and precipitates. Regenerated biochar could be reused as an adsorbent in the subsequent adsorption cycle. HIGHLIGHTS Pine bark biochar produced through slow pyrolysis at 650 °C successfully adsorbed copper from an aqueous solution.; Biochar adsorption capacity of 106 mg/g of copper was obtained.; Simultaneous removal of adsorbed copper and regeneration of biochar were accomplished through bio-sulfide precipitation.; The regenerated biochar could be reused in the successive adsorption cycle.;

Keywords

• adsorption
• biochar regeneration
• bio-sulfide precipitation
• continuously stirred tank reactor
• copper-loaded biochar
• loading rate