Indium ion removal and recovery by means of water‐insoluble amphoteric starches

The removal and recovery of indium ion (In3+) from solutions with water‐insoluble amphoteric starches containing the phosphate anionic group and the quaternary ammonium or tertiary amine cationic group was investigated. The adsorption capacity of tertiary amine phosphate starch (TAP) and quaternary ammonium phosphate starch (QAP) is 0.54 meq/g and 0.48 meq/g, respectively. The adsorption process has been found to be concentration‐dependent and exothermic, and follows the Langmuir isothermal adsorption. The heat of adsorption (ΔH) is equal to −5.86 kJ/mol for QAP, and equal to −90.44 kJ/mol for TAP. The amount of adsorbed In3+ ion on the adsorbents decreases when inorganic acids (HCl or H2SO4) or sodium salts (NaCl or Na2SO4) are added to the solution. The adsorbed In3+ ion can be desorbed by treating with a HCl solution (1 and 3 M); the maximum percentage of desorption reaches about 80% when 1 N HCl solution is used.