Simultaneous removal of thallium and chloride from a highly saline industrial wastewater using modified anion exchange resins

Simultaneous removal of thallium (Tl) and chloride from a highly saline industrial wastewater was investigated using modified anion ion exchange resins. The removal of thallium was mainly driven by the exchange of Tl-chlorocomplex (TlCl4−) formed in the oxidation of thallous (Tl (I)) to thallic ion (Tl (III)) by hydrogen peroxide (H2O2) under saline conditions. Over 97% of thallium and chloride removal was achieved using the modified resins, with a wide optimal conditions found to be H2O2 dosage 1.0-25.0 mL/L, pH 1.6-4.3, and flow rate 0.5-4.7 mL/L. The modified resins had an exchange capacity of 4.771 mg Tl/g dry resins for thallium and 1800 mg Cl/g dry resins for chloride. Stable regeneration could be achieved with the modified resins: over 97% of thallium and 90% of chloride can be eluted using Na2SO3 solution and alternating hot (60 °C) H2SO4 and cold (25 °C) water, and over 98% removal of thallium and chloride was achieved after five consecutive regeneration cycles.