Abstract:
Adsorption of Rh(III) ions from the aqueous phase containing chloride ions was investigated batchwise using 1,3,5-triazine pentaethylenehexamine (TAPEHA) resin, which is highly resistant to strong acidic conditions. The effects of pH, temperature, initial concentration, and contact time on adsorption were examined. Rh(III) adsorption is favorable from the aqueous phase containing 3.0 and 0.1 M HCl. In both acidic cases, Langmuir is best fitting isotherm equation to system. The kinetics of Rh(III) adsorption on TAPEHA polymer was found to obey the pseudo-second-order kinetic equation, at both cases. Langmuir monolayer adsorption capacities were calculated as 327.03 and 113.76 mg/g in 3.0 and 0.1 M HCl, respectively. Experimental maximum adsorption capacities were measured as 198 and 100 mg/g in 3.0 and 0.1 M HCl, respectively. Due to different Rh(III) complexes with chlorine depending on acid concentrations, adsorption of Rh(III) from solutions containing 3.0 and 0.1 M HCl occurred via two different mechanisms; namely, ion exchange and surface complexation. The reuse of TAPEHA was also studied by column procedure, and the adsorption capacity of TAPEHA was not changed by using it five times. Adsorbed Rh(III) ions onto TAPEHA were completely eluted with thiourea 3% (w/v) in 1.0 M HCl. These findings showed that TAPEHA has a high resistance to acidic solutions and a higher Rh(III) uptake capacity than commercial adsorbents. Hence it can be used for rhodium recycling.
