Remediation and resource utilization of Cr(Ⅲ), Al(Ⅲ) and Zr(Ⅳ)-containing tannery effluent based on chitosan-carboxymethyl cellulose aerogel

Composite aerogel based on sodium carboxymethyl cellulose (CMCNa) and chitosan (CS), i.e., CS/CMCNa, was prepared through a sol-gel method. Then, CS/CMCNa was used for simulating the adsorption of metal ions (Cr³⁺, Al³⁺ and Zr⁴⁺) produced by the tanning industry. The adsorption process is consistent with the Langmuir isotherm adsorption model and pseudo-second order kinetics. The maximum fitted adsorption capacities of Cr³⁺, Al³⁺, and Zr⁴⁺ could reach 250.0, 111.1, and 100.0 mg/g, respectively. After metal ion adsorption, the obtained composite materials (CS/CMCNa-Cr³⁺, CS/CMCNa-Al³⁺, and CS/CMCNa-Zr⁴⁺) were used as re-tanning agents in the re-tanning process to leather. The re-tanning agent could increase the shrinkage temperature of leather by up to 5 °C. Compared with the traditional method, the method utilized in this study achieved the integration of mental ions-containing wastewater treatment and waste adsorbent/adsorbates recycling.