Efficient removal of thallium(I) from wastewater using flower-like manganese dioxide coated magnetic pyrite cinder

Abstract

The development of highly selective, effective, and regenerable adsorbents with good separability for thallium (Tl) removal remains a challenge. In this study, a hierarchical composite containing MnO2 and magnetic pyrite cinder was fabricated to remove Tl(I) from wastewater. SEM, TEM, XRD, BET, and VSM analyses indicate that the hierarchical composite was composed of amorphous, flower-like MnO2 as outer coating and magnetite-dominated pyrite cinder as inner core, with a specific surface area of 29.1 m2/g and saturation magnetization of 15.4 emu/g. Good Tl(I) adsorption was achieved over a wide pH range from 2 to 12. A maximum Tl(I) adsorption capacity of 320 mg/g was attained at pH 12. The presence of Na+, Mg2+, and humic acid had little effect on Tl(I) removal, indicating the high selectivity of this adsorbent. The adsorption isotherm data were better fitted by the Langmuir model, while the pseudo-second order model was more suitable for describing the kinetic data. The composite was effectively regenerated using 1 mol/L HCl solution in only 5 min, and the Tl(I) adsorption capacity of the composite did not change significantly even after the fifth regeneration. Tl(I) removal was mainly achieved via surface complexation, followed by oxidation and electrostatic attraction. This flower-shaped MnO2 coated pyrite cinder composite shows promise for Tl(I) removal due to its excellent efficiency, selectivity, separability, and reusability.