Kinetic and Equilibrium Function and Switchable Catalytic Activity of Some Thermo-Responsive Hydrogel Metal Absorbents Based on Modified PNIPAM

Synthesis and identification of some thermo-responsive hydrogel metal absorbents based on Schiff base modified PNIPAM is described. PNIPAM hydrogel is produced through conventional free-radical polymerization method. The hydrogel is amino modified with different amines and then treated with various aldehydes to make polymeric Schiff-bases supposing to utilize as an absorbent for Cu salt. Characterization of the as-prepared hydrogels was performed properly and confirmed the corresponding structures. Kinetic and equilibrium function of the absorbents and the effect of distinct variables like pH, adsorbent amount and contact time in the absorption process are investigated in detail. Kinetic and adsorption isotherm data agreed with pseudo-second order model and Langmuir isotherm, respectively. The maximum value of adsorption capacity of the prepared adsorbent was around 8550 mg g−1. In addition, the corresponding switchable catalytic activity using one of the thermo-responsive hydrogel metal absorbents in the reduction of 4-nitro phenol to 4-amino phenol in the role of model reaction is examined.