Adsorption of Cd(II) onto Auricularia auricula spent substrate biochar modified by CS2: Characteristics, mechanism and application in wastewater treatment

Biochar is a promising adsorbent used to remove heavy metals from wastewater. In order to improve its per-formance in adsorption, the biochar derived from Auricularia auricula spent substrate (BC), was further modified by carbon disulfide (CS2), and the characteristics and mechanism of the modified biochar (SBC) for Cd(II) adsorption were investigated. CS2 modification induced sulfur (S)-containing groups onto SBC and increased S content by 9%. In batch adsorption experiments, the adsorption rate (R) and adsorption capacity (q) of SBC reached to 96.1% and 9.61 mg/g respectively, which were significantly greater than those of BC. Cd(II) was precipitated in the form of CdS, CdSO3 and CdSO4 in the presence of SBC. The adsorption was a spontaneous and endothermic reaction with the qmax of 450.51 mg/g. The q0 of 6.29 mg/g was achieved under the breakthrough time of 90 min and exhaustion time of 1140 min. During three adsorption-desorption cycles, SBC presented a favorable recyclability with the desorption rate increased from 69.51% to 99.12% with EDTA as eluent. SBC also performed perfectly in actual electroplating wastewater treatment.