Effect of CeO₂-Reinforcement on Pb Absorption by Coconut Coir-Derived Magnetic Biochar

Magnetic separable biochar holds great promise for the treatment of Pb²⁺-contaminated wastewater. However, the absorption effect of unmodified magnetic biochar is poor. Considering this gap in knowledge, CeO₂-doped magnetic coconut coir biochar (Ce-MCB) and magnetic coconut coir biochar (MCB) for Pb²⁺ absorption were prepared by the impregnation method, and the efficiency of Ce-MCB for Pb²⁺ absorption was evaluated in comparison with MCB. Conducting the absorption experiments, the study provided theoretical support for the exploration of the absorption mechanism. The quantitative analysis exposed that the enhanced absorption capacity of Ce-MCB was attributed to the increase in oxygen-containing functional groups and mineral precipitation. The Langmuir and Freundlich isotherm model showed that Ce-MCB is a suitable adsorbent for Pb²⁺. The absorption characteristics of Ce-MCB was fit well with the pseudo-second-order (PSO) and Langmuir models, which revealed that the absorption of Pb²⁺ in water was monolayer chemisorption with a maximum theoretical adsorption capacity of 140.83 mg·g^-1. The adsorption capacity of Ce-MCB for Pb(II) was sustained above 70% after four cycles. In addition, the saturation magnetization intensity of Ce-MCB was 7.15 emu·g^-1, which was sufficient to separate out from the solution. Overall, Ce-MCB has wide application prospects in terms of biomass resources recycling and environmental conservation.