Role of protonation and functional groups in Pd(II) recovery and reuse characteristics of commercial anion exchange resin-synthetic electroless plating solution systems

Deliberating upon the role of solution chemistry complexity, protonation, speciation and pertinent functional groups on the adsorption-desorption characteristics, this work targets the efficacy of Lewatit TP-214 and Amberlyst A21 commercial anion exchange resins for Pd(II) recovery and reuse from synthetic electroless plating (ELP) solutions. For both resins, batch adsorption experiments involved optimality of pH, contact time, adsorbent dosage followed with concentration effect and kinetic studies. Equilibrium, kinetic, and thermodynamic models were considered for their fitness with the obtained Pd(II) batch adsorption characteristics. Among both resins, Lewatit TP-214 resin provided better performance in terms of adsorption and desorption characteristics along with optimal combinations of pH (8), equilibrium time (300 min), and adsorbent dosage (2 g L-1). Overall, both resins provided significantly lower Pd(II) absorption capacity and removal% for ELP systems in comparison with aqueous solutions. This is due to the inhibitory role of Ethylenediaminetetraacetic acid (EDTA) and ammonia during Pd(II) binding with active sites on the resins. The obtained desorption characteristics and associated Pd (II) adsorption and desorption mechanisms are promising to further commercial application of the said resins.