Adsorption of Zn2+ ion by macadamia nut shell biochar modified with carboxymethyl chitosan and potassium ferrate.

A series of biochars and modified biochars were prepared by using macadamia nut shell (MNS) as raw material at different calcination temperatures and further using carboxymethyl chitosan (CMC) and K 2 FeO 4 as the modifying agent, respectively. These biochar and modified biochars were used as adsorbents for adsorbing Zn²⁺ ion in aqueous solution. It is found that the adsorption behaviors of modified biochars BC-CMC and BC-K 2 FeO 4 are consistent to the pseudo second-order kinetics model and the Langmuir equation. The maximum adsorption capacities for these adsorbents are increased in the following order: BC-CMC > BC-K 2 FeO 4 > > BC-700. Among these biochars, BC-CMC exhibits the highest adsorption capacity of 97.09 mg/g, which may be mainly due to that BC-CMC has more amino, hydroxyl and carboxyl functional groups. The BC-CMC also exhibits better desorption performance and reusability. Furthermore, BC-CMC also shows higher adsorption capacity for Cu²⁺ and Pb²⁺. Based on the results, the adsorption mechanism of BC-CMC for Zn²⁺ was also proposed. [Display omitted] • The modified biochars were prepared by using CMC and K 2 FeO 4 as modifying agent. • The adsorption capacity of BC-CMC for Zn²⁺ reaches to 97.09 mg/g. • The BC-CMC exhibits good desorption performance and reusability. • BC-CMC shows higher adsorption capacity for Cu²⁺ and Pb²⁺. • The possible adsorption mechanism of biochar for Zn²⁺ is proposed. [ABSTRACT FROM AUTHOR]