Effective and selective separation of perrhenate from acidic wastewater by super-stable,superhydrophobic, and recyclable biosorbent

? A ZnO-biochar hybrid composite was prepared by solvothermal-pyrolysis synthesis. ? The superhydrophobic composite is suitable for selective recovery of Re(VII). ? The adsorption mechanism is elucidated by experiments and material characterization. The recovery of scattered metal ions such as perrhenate (Re(VII)) from industrial effluents has enormous economic benefits and promotes resource reuse. Nanoscale-metal/biochar hybrid biosorbents are attractive for recovery but are limited by their insufficient stability and low selectivity in harsh environments. Herein, a superstable biochar-based biosorbent composed of ZnO nanoparticles with remarkable superhydrophobic features is fabricated, and its adsorption/desorption capabilities toward Re(VII) in strongly acidic aqueous solutions are investigated. The ZnO nanoparticle/biochar hybrid composite (ZBC) exhibits strong acid resistance and high chemical stability, which are attributable to strong C-O-Zn interactions between the biochar and ZnO nanoparticles. Due to the advantages of its hydrolytic stability, superhydrophobicity, and abundance of Zn-O sites, the ZBC proves suitable for the effective and selective separation of Re(VII) from single, binary and multiple ion systems (pH= 1), with a maximum sorption capacity of 29.41 mg/g. More importantly, this material also shows good recyclability and reusability, with high adsorption efficiency after six adsorption-desorption cycles. The findings in this work demonstrate that a metal/biochar hybrid composite is a promising sorbent for Re(VII) separation.