Design and Fabrication of Co([CHITOSAN-AMPS-AA]/PEI-MBA) Nanocomposite Hydrogel as an Effective Solution for Removing Tin and Platinum Ions in Wastewater Treatment Applications: Selective Recovery of Platinum

A nanocomposite hydrogel Co([CHITOSAN-AMPS-AA]/PEI-MBA) was synthesized using silica and graphene oxide nanoparticles by a free radical polymerization method. The hydrogel was used to adsorb tin and platinum from wastewater produced during production of a commercial dehydrogenation process. The adsorbed platinum could be selectively released from the adsorbing hydrogel platinum. Various tests including FTIR, XRD, TGA, and Rheology were conducted to identify the hydrogel’s three-dimensional structure. The adsorption performance was evaluated using ICP, SEM, and EDS tests. The ability of hydrogel for multiple adsorptions was also assessed. The thermodynamical study and adsorption isotherms were investigated, and the possible structure of the synthesized adsorbing hydrogel was presented. The results showed that while the hydrogel could adsorb platinum physically in three consecutive cycles from wastewater, tin is chemically adsorbed during the process. The physically-adsorbed platinum could then be released selective. The adsorption isotherm of platinum and tin ions followed the Langmuir adsorption isotherm model while the adsorption rate represented a pseudo-first-order kinetic model. The hydrogel had an adsorption capacity of 263.16 mg/g for platinum and 188.88 mg/g for tin with the Gibbs free energy of − 1710.86 J/mol and − 4521.08 J/mol, respectively. It was found that the hydrogel can be reused for practical and large-scale wastewater treatment as less than 10% decrease in the adsorption capacity was observed after three consecutive adsorption–desorption cycles.