Efficiently selective adsorption of Pb(II) with functionalized alginate-based adsorbent in batch/column systems: Mechanism and application simulation

Abstract

Efficient and selective capture of metal ions from actual wastewater is the global challenge but of utmost significance towards the treatment and recovery of toxic metal wastes. Herein, a novel N/O-enrichment adsorbent (CM0.5AP0.75) with throughout adsorption sites and square-built ions/molecules diffusion pathway, transformed from polyethyleneimine/melamine co-functionalized alginate, was simply obtained utilizing sol-gel technology. Benefiting from the synergy effect of monovacancy nitrogen/oxygen species (high content and strong surface polarity) of adsorbent and discrepant physicochemical property of metal ions, the CM0.5AP0.75 possessed a strong adsorption capacity (596.68 mg/g) towards Pb2+ and a selectivity order of Pb2+ > Cu2+ > La3+ > Cd2+ > Ni2+. Specific focus is placed on highest selectivity of CM0.5AP0.75 for Pb2+ (distribution coefficient (Kd) of 4.6 × 104 mL/g and selective coefficient (k) of 2956.15 in Pb2+/Ni2+ binary system) that could be utilized to verify the efficient selective separation of targeted lead ions in batch/column operating systems. The FT-IR, along with XPS analysis, confirmed that the selective capture of Pb2+ mainly depended on ion-exchange/surface-complexation under the guidance of Hard-Soft-Acid-Base theory. For potential applications, the cooperation of bead-like shape and enhanced strength-toughness (formation of coating skin and incorporation of rigid melamine; max percentage of water uptake = 71.89%) endowed the prepared adsorbent with minimal loss in performance and continuous impact resistance. More convincingly, compared with other works that mostly focused on static adsorption, the work was firstly tied to give a comprehensive evaluation of dynamic adsorption behavior of flowing unitary/binary/quinary metal ions on CM0.5AP0.75 in fixed-bed columns, especially dynamic selective adsorption (continuous adsorption of 7000 min; high column selectivity of Pb2+). The study provides theoretical and practical guidance for the efficient remediation of actual wastewater.