Green composite hydrogel coupling regulated with waste aluminum sludge and biomass for highly selective Pb(Ⅱ)-removal

The highly selective removal of Pb(Ⅱ) from complex wastewater is crucial for effectively treating lead-containing industrial wastewater. Herein, a composite hydrogel adsorbent (LSS-SA) was synthesized by modifying waste Al-rich sludge via free radical polymerization of sodium lignosulfonate (LS) and acrylamide, followed by encapsulation within a sodium alginate (SA) matrix. The LSS-SA possessed a fibrous network morphology and exhibited a 192.70 % increase in specific surface area compared to pure SA. Notably, LSS-SA demonstrated exceptional selectivity for Pb(Ⅱ) against competing divalent metals (Zn(Ⅱ), Cd(Ⅱ), Ni(Ⅱ)), achieving maximum selectivity coefficients of 67.78, 63.60, and 159.94, respectively. The high selectivity for Pb(Ⅱ) was primarily attributed to strong coordination with sulfonic acid groups and amino groups. The adsorbent also demonstrated strong anti-interference capability against co-existing ions, excellent regenerability (above 95.14 %) and low cost ($ 841.36/t). These results, together with dynamic column studies and simulated wastewater tests, collectively demonstrate the potential of LSS-SA as an efficient and sustainable adsorbent for treating actual lead-containing wastewater.