Adsorption and desorption properties of indium (III) on cationic exchange fiber

The enrichment and recovery of indium (III) by cationic exchange fiber adsorption method were investigated. With the measurement of related parameters such as pH, temperature and adsorption time, the adsorption kinetic and the thermodynamic of sulfuric acid group modified polystyrene were studied. The results show that the maximum adsorptive capacity of cationic exchange fiber can be attained at pH=2-3.5; the adsorption behavior of cationic exchange fiber for indium (III) obeys the freundlich isotherm; the adsorption kinetic data fit the Ho pseudo-second order rate equation, and besides the intra-particle diffusion, other processes such as film diffusion also affect the rate of adsorption simultaneously. At 287-350K the adsorption mol fraction of indium (III) is 0.6-1.2 mmol/g, the changes of adsorption enthalpy is 35.68-32.36kJ/mol, the free energy is -16.63 -21.10 kJ/mol, the entropy of adsorption is 181.9-156.6 J/(K·mol), the adsorption rate constant are k _287K=0.09379 g/(mg·min), k _300K=0.1159 g/(mg·min), k _321K=0.4046 g/(mg·min) and k _350K=0.6678 g/(mg·min). The adsorption activity energy is 28.28 kJ/mol. At 303 K, 99% of the indium (III) adsorbed by the cationic exchange fiber can be easily and quickly eluted with 0.50 mol/L sulphuric acid solution.