Pd(II) adsorption characteristics of glutaraldehyde cross-linked chitosan copolymer resin

Deliberating upon the role of solution chemistry in influencing the Pd(II) adsorption and desorption characteristics using chitosan based resins, this work addresses the competence of glutaraldehyde cross-linked chitosan (GCC) co-polymer resin for the removal and recovery of Pd(II) from synthetic electroless plating solutions. GCC copolymer adsorbent was prepared by grafting of fixed weight ratio (1/17) of medium molecular weight chitosan and glutaraldehyde (25% in H₂O). Within the adsorption parametric range of 2-10pH, 60-300min contact time, 10-50mg adsorbent dosage and 50-500mg/L initial Pd(II) concentration, the solution chemistry associated to synthetic ELP solution has been evaluated to strongly reduce the adsorption capacity of the GCC resin. Batch equilibrium adsorption studies inferred upon the fitness of Langmuir isotherm with a monolayer adsorption capacity of 166.67mg/g. Adsorption kinetics and thermodynamic parametric evaluations affirmed pseudo-second-order kinetics and spontaneous exothermic Pd(II) adsorption on the resin. Further, speciation analysis provided valuable insights by indicating greater favourability of Pd(NH₃)₄²⁺ species (at pH=8) than PdEDTA^-2 (at lower pH) to foster chemisorption with the GCC resin. In summary, the observations affirmed that solution chemistry needs to be addressed in laboratory investigations to further industrial application and competitiveness of alternate resins.