Efficient scavenging of aqueous Pb(II)/Cd(II) by sulfide-iron decorated biochar: Performance, mechanisms and reusability exploration

Sulfide-iron decorated biochar described as BC-Fe-S was prepared and employed for the elimination of cadmium (Cd) and lead (Pb) from water. Characterizations not only proved the loading of Fe2O3 onto biochar, but also attested the sulfuration of biochar. The resultant BC-Fe-S exhibited pH-dependent uptake capacities with rapid equilibriums within 30 min conforming to pseudo-second-order model. Moreover, BC-Fe-S possessed excellent pollutants uptake in a high affinity to Langmuir model with theoretical monostromatic uptake capacities of 57.71 mg/g concerning Cd(II) and 124.62 mg/g for Pb(II). Thermodynamic consequences exposed that the contaminants uptake proceeded spontaneously with enhancive randomness and exothermic peculiarities. The BC-Fe-S was proved to bind the Cd(II)/Pb(II) primarily via chelation, ion exchange, co-precipitation, and electrostatic interaction. Additionally, the elimination of Cd(II)/Pb(II) by BC-Fe-S dropped fractionally after four adsorption-desorption processes. Overall, co-modification of sulfuration and Fe-based particles loading was useful for decorating biochar to adsorptive elimination of heavy metals from water.