Highly efficient sorption of hexavalent chromium from aqueous solutions using xanthate-magnetic biochar derived from fish scales

Abstract

Disposing untreated chromium containing wastewater into natural water bodies affects human health and the environment due to its carcinogenic and non-degradable nature. Therefore, current research presents synthesis and comparison of chemically activated biochars via magnetization (MF@BC) and xanthation (XMF@BC) with its crude form (BC) derived via pyrolysis of fish scales for adsorptive removal of hexavalent chromium (Cr (VI)) from wastewater. Moreover, the prepared sorbents were characterized by SEM-EDX, FT-IR, BET, XRD and point of zero charge. The results indicated that MF@BC and XMF@BC possess a heterogeneous porous structure, abundant active sites, and larger specific surface area, auspicious for removal of Cr (VI) ions from wastewater. The effect of solution chemistry parameters i.e., sorbent dosage, pH, contact time, initial concentration of Cr (VI), and temperature were also investigated. The BC, MF@BC and XMF@BC presented Cr (VI) sorption potential of 77.6%, 91.9% and 94%, respectively for 20 mg/L Cr (VI) suspension at optimal solution specifications that are: pH (3), contact time (120 minutes) and (2 g/L) sorbent dosage. The kinetic and isotherms studies found that the Pseudo-second order (PSO) kinetic model and Elovich Isotherm model corresponded to Cr (VI) adsorption better. The thermodynamic studies showed that the Cr (VI) uptake by modified biochars occurred instinctively (-ΔG) and exemplified an endothermic response (+ΔH). The regeneration study revealed the effective Cr (VI) removal i.e., 52.2%, 60.7% and 72.3% for BC, MF@BC and XMF@BC, respectively up to six cycles. The FT-IR and XRD results confirmed the significant role of hydroxyapatite and cologne in synthesized biochars for enhanced Cr (VI) removal from water. In general, these results suggested the promising nature of synthesized biochars in remediation of Cr (VI) ions from wastewater.