The adsorption of perrhenate ions by the bio-char prepared from Acidosasa edulis shoot shell at 773 K is investigated under acidic conditions. The effects of some important parameters including initial pH (1.0–6.0), adsorbent dose (0.8–8.0 g L−1), contact time (2–480 min) and initial perrhenate ion concentration (10–100 mg L−1), on the recovery of perrhenate ions from aqueous solution in batch experiments are tested. The adsorbent was characterized by scanning electron microscopy equipped with an energy-dispersive X-ray spectroscopy (SEM-EDX), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and specific surface area analysis. The adsorption data are well described by Freundlich isotherm and maximum perrhenate ions adsorption capacities of 14.6 mg g−1 for Acidosasa edulis shoot shell bio-char under the optimum conditions. Kinetics of adsorption are found to follow the pseudo-second-order rate equation. Thermodynamic analysis suggested that the adsorption is an endothermic process and occurs spontaneously. FTIR analysis confirmed the major involvement of hydroxyl and carboxyl groups during perrhenate ion adsorption. Further, more than 94% of total rhenium adsorbed could be recovered using 0.1 mol L−1 KOH as a desorption medium. The mechanism analysis indicates that the outer-sphere complexes and electronic attraction mechanism were involved in the adsorption of perrhenate ions. The results indicate that Acidosasa edulis shoot shell waste derived bio-char can act as an effective adsorbent material for perrhenate ions recovery from copper smelting acidic wastewater.

The Acidosasa edulis shoot shell (AESS) was used to remove Cu2+ from water for the first time. The biosorbent was characterized by acid–base titration, point zero charge determination, SEM, XRD and FTIR. The effects of operation parameters were studied. Kinetics data were best described by pseudo-second-order model. The equilibrium data of biosorption were best described by Langmuir isotherm model. The calculated thermodynamic parameters indicated that the biosorption was endothermic and spontaneous. Mechanism analysis indicated that biosorption of Cu2+ mainly occurred in the amorphous region of AESS. Phenolic sites and carboxyl sites in the amorphous region of AESS were mainly responsible for the biosorption. Phenolic sites formed complex with Cu2+, while carboxyl sites exchanged H+ with Cu2+ by ion-exchange mechanism. The results revealed that AESS could be used as an effective and low-cost biosorbent for Cu2+ removal from aqueous solutions.

•Rhenium can be as a reliable surrogate for radioactive technetium.•AESS biochar has strong adsorption ability to perrhenate in acidic solution.•Maximum adsorption capacity was 46.46 mg/g.•High hydrophobicity and basic site of biochar contribute to recovering perrhenate.In this work, a biochar was prepared from bamboo (Acidosasa edulis) shoot shell through slow pyrolysis (under 300–700 °C). Characterization with various tools showed that the biochar surface was highly hydrophobic and also had more basic functional groups. Batch sorption experiments showed that the biochar had strong sorption ability to perrhenate (a chemical surrogate for pertechnetate) with maximum sorption capacity of 46.46 mg/g, which was significantly higher than commercial coconut shell activated carbon and some adsorbents reported previously. Desorption experiments showed that more than 94% of total perrhenate adsorbed could be recovered using 0.1 mol/L KOH as a desorption medium. Pearson correlation analysis showed that the recovery of perrhenate by the biochars was mainly through surface adsorption mechanisms involving both high hydrophobicity and high basic sites of biochar surface.Download high-res image (166KB)Download full-size image