Combinatorial optimality of functional groups, process parameters, and Pd(II) adsorption-desorption characteristics...

Considering combinatorial optimality of functional group analysis, speciation, solution chemistry complexity, Pd(II) adsorption-desorption characteristics, this article addresses the competence and efficacy of anion exchange resins namely Amberlite IRA958, Dowex Marathon MSA, Lewatit TP214, and Amberlyst A21 commercial resins. Based on preliminary batch adsorption experiments conducted in the range of 2-10 pH, 0.2-2 g L^-1 adsorbent dosage, and 5-1080-min contact time, the optimal adsorption process parameters refer to 4 pH, 1.6, and 1.4 g L^-1 adsorbent dosage, and 840- and 720-min contact time for Amberlite IRA958 and Dowex Marathon MSA resins, respectively. Among alternate models, the best-fit models refer to the Freundlich isotherm and pseudo-second-order kinetic models to represent Pd(II) adsorption data obtained for both Dowex Marathon MSA and Amberlite IRA958 resins. Based on the Langmuir isotherm, the maximum monolayer adsorption capacity was evaluated to be 185.16 and 166.67 mg g^-1 for Dowex Marathon MSA and Amberlite IRA958 resins, respectively. For model electroless plating solutions as adsorbate system possessing desired solution chemistry complexity and resin cost, nitrogen- and oxygen-containing Amberlyst A21 resin is concluded to be optimal resin. This is not in agreement with the generalized rule of thumb that considers sulfur-nitrogen functional group containing commercial resins to be effective than resins with nitrogen-oxygen functional groups. Due to functional group interactions with the noble metal, no other by-products or exchanged chemicals have been produced in due course of Pd(II) adsorption process, which can be also regarded as an added advantage of the process. Graphical abstract.