Palladium adsorption on natural polymeric sericin-alginate particles crosslinked by polyethylene glycol diglycidyl ether

The use of palladium (Pd) is growing and its scarcity, high price and the pollution generated in its mining motivate the development of research on its removal from effluents. In this work, the use of particles produced from waste sericin and alginate blend crosslinked by polyethylene glycol diglycidyl ether for Pd adsorption was evaluated by means of kinetic and equilibrium studies, thermodynamic parameters and characterization analyses. Sericin is a protein, present at Bombyx mori cocoons, which is discarded in the silk yarn process. Because of its chemical characteristics, the protein can form blends, as with alginate, a polysaccharide present in brown algae. The produced particles are macroporous with amorphous structure and surface area of 5.2 m(2)/g. In kinetics, removals above 97% were achieved from 0.5 mmol/L Pd solution (pH 2.5-3.0) with better pseudo-second order rate law fitting. The Langmuir model was better fitted to the equilibrium, but the surface has been proved to be energetically heterogeneous. External mass transfer resistance has proved to be the limiting step of adsorption. Chemisorption and physisorption are involved at metal uptake and maximum adsorbed capacities were 0.157, 0.191 and 0.249 mmol/g, at 25, 40 and 55 degrees C, indicating the feasibility of the adsorbent use for Pd removal/recovery.

Automated summary

This study evaluated the use of particles produced from waste sericin and alginate blend for Pd adsorption, showing high removal rates and better fitting with pseudo-second order rate law. External mass transfer resistance was identified as the limiting step of adsorption, and both chemisorption and physisorption were involved in metal uptake. The adsorbent demonstrated feasibility for Pd removal and recovery with maximum adsorbed capacities at different temperatures.