Adsorption Performance and Mechanism of Synthetic Schwertmannite to Remove Low-Concentration Fluorine in Water

Fluorine (F) in water has a negative effect on the environment and human health. Schwertmannite has potential remediation to contamination in solution. In this study, the adsorption mechanism and influencing factors of synthetic schwertmannite for low-concentration F were studied through batch experiments. The results suggested that the adsorption of F by schwertmannite reached equilibrium after about 60 min, and the adsorption efficiency exceeded 94%. The experimental data can be best-fit by the pseudo-second-order kinetic and Langmuir models well. Schwertmannite showed effective adsorption at pH 4, dosage 1.5 g L-1, low temperature, and low concentration of co-existing anion. The adsorption process was a spontaneous and exothermic reaction, which was dominated by chemical adsorption. FT-IR and XPS spectra analysis revealed that F adsorption on schwertmannite through the surface complexation and anion exchange reaction between SO42- and OH- with F-, especially the primary role of OH-. The results can provide theoretical support for the schwertmannite application in the treatment of F-containing wastewater.

Automated summary

The study demonstrated that synthetic schwertmannite has excellent adsorption capability for low-concentration fluoride, with optimal performance under specific conditions. The adsorption process is mainly dominated by chemical adsorption, facilitated by surface complexation and anion exchange reactions.