The utilization of lobster shell to prepare low-cost biochar for high-efficient removal of copper and cadmium from aqueous: Sorption properties and mechanisms

The target of this research was to explore the adsorption characteristics and mechanisms for the adsorption of copper and cadmium by lobster shell biochar. Two biochars were produced from lobster shells through pyrolysis at 300 and 600℃ (labeled LS300 and LS600). The kinetics and isotherm adsorption curves of Cu2+ and Cd2+ on these lobster shell biochars were determined. The adsorption kinetic curves were best depicted by the two-compartment model, and the Toth model was suitable for the isotherm data of Cu2+ and Cd2+. Compared with those of LS300, the adsorption capacities of LS600 for Cu2+ and Cd2+ were greater. The original biochar and Cu2+ or Cd2+-loaded biochar were analyzed by SEM-EDS, FTIR, and XRD to explore the adsorption mechanisms. Ion exchange with cations, precipitation with minerals, and interaction with functional groups were the potential mechanisms for the adsorption of Cu2+ and Cd2+ by the lobster shell biochars. The contribution rates of these three mechanisms were also calculated. The adsorption mechanism of Cu2+ onto the prepared biochar was dominated by ion exchange, while cation exchange and interaction with functional groups were the primary adsorption mechanisms of LS300 and LS600 for Cd2+, respectively. Moreover, the adsorption capacity of lobster shell biochar was higher than that of other reported biochars. The results of this study indicate that lobster shell biochar is a highly effective adsorbent for the removal of Cu2+ and Cd2+ from contaminated water.