Facile synthesis of sodium lignosulfonate/polyethyleneimine/sodium alginate beads with ultra-high adsorption capacity for Cr(VI) removal from water

Chromium (VI) is a widely occurring toxic heavy metal ion in industrial wastewater that seriously impacts the environment. In this study, we used environmentally friendly sodium lignosulfonate (SL), polyethyleneimine (PEI), and sodium alginate (SA) to synthesize SL/PEI/SA beads by employing a simple crosslinking method with to develop a novel absorbent with excellent adsorption capacity and practical application in wastewater treatment. We studied the adsorption performance of SL/PEI/SA through batch adsorption and continuous dynamic adsorption experiments. SL/PEI/SA has ultra-high adsorption capacity (2500 mg·g-1) at 25 ℃, which is much higher than that of existing adsorbents. Humic acids and coexisting anions commonly found in wastewater have minimal effect on the adsorption performance of SL/PEI/SA. In the column system, 1 g SL/PEI/SA can treat 8.1 L secondary electroplating wastewater at a flow rate of 0.5 mLmin-1, thereby enabling the concentration of Cr(VI) in secondary electroplating wastewater to meet the discharge standard (< 0.2 mg·L-1). It is worth noting that the concentration of competitive ions in secondary electroplating wastewater is more than 500 times higher than that of Cr(VI). These results demonstrate that the novel SL/PEI/SA beads can be effectively applied in the removal of Cr(VI) in wastewater.