Mechanism of iron salt impregnated biowaste biochar with a prevailing free radical initiator for effective removal of toxic thallium from solution

Thallium is an emerging metallic pollutant with extremely high toxicity which resulted in worldwide water pollution in the past decades. It is critical to develop multiple alternative methods for Tl removal to enrich control strategy towards Tl pollution in aquatic environment. It is proposed herein a highly effective and environmental-friendly Tl removal method by applying iron salt-impregnated biochar (BC) combined with persulfate (PS), using two most common iron salts (FeCl3 and Fe(NO3)3). It was found that FeCl3@BC-PS system achieved higher Tl removal capacity (164.42 mg/g), which exhibited a comparative preponderance relative to the reported iron based adsorbent composites, partially owing to significantly enhanced specific surface area (854.48 m2/g). The dominant Tl removal mechanisms include free radical based oxidation and chemical adsorption. Radical quenching experiments confirmed that SO4− and OH served as vital radicals for FeCl3@BC-PS and Fe(NO3)3@BC-PS, respectively. The study provides a reliable alternative for Tl-wastewater treatment with PS activation by catalyst based on the synergistic effect of biochar and iron salts.