Effect of different Fe(III) precursor on behavior and mechanism for removal thallium(I) by iron-carbon composites
摘要
Thallium (Tl) has been regarded as one of the highly toxic heavy metals due to the serious menace to the safety of humans and animals. In this manuscript, three iron-carbon composites were synthesized by different precursors Fe(NO3)3, Fe2(SO4)3 and FeCl3, and Tl(I) adsorption behavior and mechanism of the obtained composites were investigated by batch experiment. From the characterization of the sample structure, it was found that the highest BET surface areas, the loose structure, and the highest stability have been obtained in the precursor Fe(NO3)3. The forms of iron grafted over biochar were Fe(II)–OH, Fe(II)SO4, and Fe(III)–OH for precursors Fe(NO3)3, Fe2(SO4)3, and FeCl3, respectively. From the adsorption data, the Tl(I) removal performance of iron-carbon composites was strongly affected by iron precursors, and as the order of FeCl3 < Fe2(SO4)3 < Fe(NO3)3. The maximum Tl(I) adsorption capacity of precursor Fe(NO3)3, Fe2(SO4)3, and FeCl3 was 76.34 mg/g, 36.29 mg/g, and 21.08 mg/g, respectively. From the XPS, the redox reaction by oxidized Fe(II) and Tl(I) into Fe(III) and Tl(III) via providing electrons of hydroxyl of Fe(II)–OH group was the main adsorption mechanism of precursor Fe(NO3)3. The low removal performance at precursors FeCl3 and Fe2(SO4)3 was attributed to the absence of Fe(II)–OH and inhibition of SO42−.