Preparation of trimesic acid cross-linked chitosan adsorbent and its selective separation performance for lead ions

Background Efficient lead extraction and recovery from wastewater are crucial for advancing sustainable metal recycling and reducing environmental pollution. Method Herein, a chitosan-TMA composite (CSTA) was synthesized via one-step cross-linking of chitosan with trimesic acid, exhibiting superior Pb(II) adsorption selectivity and capacity in aqueous solutions. Significant Findings The experimental results showed that the maximum adsorption capacity of CSTA for Pb(II) reached 98.59 mg/g at the optimal pH value of 6.0, which was much higher than that of unmodified chitosan (17.62 mg/g). Further investigation of the adsorption process revealed that the Pb(II) adsorption behavior on CSTA followed the pseudo-second-order kinetic model, suggesting a predominantly chemisorption-controlled process, and conformed to the Langmuir adsorption isotherm model with a theoretical maximum capacity of 104.17 mg/g at room temperature. Competitive adsorption experiments in a multi-cation solution (containing Zn 2+ , Cu 2+ , Ni 2+ , Co 2+ , Sr 2+ , Cd 2+ , and Ag + , pH 6.0) demonstrated CSTA's exceptional selectivity for lead, achieving a high adsorption capacity of 96.33 mg/g, significantly surpassing that of other metal ions. Combined experimental and characterization analyses revealed that Pb(II) removal primarily occurs via coordination with oxygen atoms from carboxylic acid groups in TMA. This work provides both an effective adsorbent for lead-contaminated wastewater treatment and mechanistic insights for designing biomass-based water purification materials.