Treatment of cadmium and lead ions from aqueous media and battery factory wastewater using a magnetic carboxymethyl cellulose/tea waste biochar/CoFe₂O₄/ZIF-67 composite bioaerogel.

A novel magnetic bioaerogel composite, CMCB@TWBM/ZIF-67, was synthesized by combining carboxymethyl cellulose (CMC), tea waste biochar modified with cobalt ferrite (TWBM), and ZIF-67, creating a functional material for effective heavy metal removal from water. Comprehensive characterization by FTIR, XRD, SEM, BET, and VSM confirmed its hierarchical porous structure (25.7 m2/g) and good magnetic properties (9.87 emu/g). Under optimal conditions (pH 6-7, 25 °C, 10 mg/L), it achieved maximum removal efficiencies of 99.06 % for Pb2+ and 97.42 % for Cd2+, with adsorption capacities of 111.6 and 71.43 mg/g, respectively, based on Langmuir isotherm models. The n and E parameters indicated favorable adsorption (n > 1, E < 8 kJ/mol), suggesting both physisorption and chemisorption mechanisms. Thermodynamic analysis showed negative enthalpy values (-76.724 and - 61.664 kJ/mol for Pb2+ and Cd2+, respectively), confirming that the process is spontaneous and exothermic. Application to real battery manufacturing wastewater demonstrated practical efficiencies of 93.16 % for Pb2+ and 90.96 % for Cd2+ despite competing ions. Regeneration tests demonstrated that the composite retained over 90 % of its efficiency after multiple reuse cycles, underscoring its stability and reusability. Overall, CMCB@TWBM/ZIF-67 shows great promise as a sustainable, high-performance adsorbent for large-scale heavy metal wastewater treatment.