The construction of SUZ-4@chitosan beads and its application for removing Pb2+ and Cd2+ in wastewater

For improving the adsorption behaviors of the adsorbent, including large adsorption capacity, high selectivity for Pb2+ and Cd2+, as well as good separability from wastewater, bioresource chitosan (CS) was introduced to modify SUZ-4 zeolite to form SUZ-4@CS beads for the first time. The adsorption ability of SUZ-4@CS beads was optimized when the mass ratio (SUZ-4:CS) was 1:1, and the aging time in NaOH solution was 24 h, and the conventional drying method was adopted rather than the vacuum one. The optimal adsorption ability of beads was 499.5 and 234.6 mg/g for Pb2+ and Cd2+, respectively. The parameters in the adsorption were adopted as 0.0075 g adsorbent for 50 mL, 250 mg/L Pb2+ solution, and 0.015 g adsorbent for 50 mL, 100 mg/L Cd2+ solution, pH = 6, t = 120 min. The connection between SUZ-4 and CS in the composite was verified to be through H-bonds rather than mechanical mixing by the characterizations. Ion exchange, precipitation, and surface complexation were involved in the ion uptake. Moreover, the prepared SUZ-4@CS(1:1) beads displayed good recyclability for both Pb2+ and Cd2+ during six recycles. Notably, SUZ-4@CS(1:1) beads could effectively remove Pb2+ and Cd2+ from the actual industrial wastewater to meet regulatory requirements. These findings demonstrate that SUZ-4@chitosan beads can be a promising adsorbent for water purification.