Adsorption of fluoride on clay minerals and their mechanisms using X-ray photoelectron spectroscopy

作者：Du, Junyi; Wu, Daishe^*; Xiao, Huayun; Li, Ping

来源：Frontiers of Environmental Science & Engineering in China, 2011, 5(2): 212-226.

DOI：10.1007/s11783-010-0255-5

• clay mineral
• fluoride (F)
• adsorption mechanism
• X-ray photoelectron spectroscopy (XPS)

This research investigates the adsorption mechanisms of fluoride (F) on four clay minerals (kaolinite, montmorillonite, chlorite, and illite) under different F- concentrations and reaction times by probing their fluoride superficial layer binding energies and element compositions using X-ray photoelectron spectroscopy (XPS). At high F- concentrations (C (0) = 5-1000 mg center dot L-1), the amount of F- adsorbed (Q (F)), amount of hydroxide released by clay minerals, solution F- concentration, and the pH increase with increasing C (0). The increases are remarkable at C (0)> 50 mg center dot L-1. The QF increases significantly by continuously modifying the pH level. At C (0)< 5-100 mg center dot L-1, clay minerals adsorb H+ to protonate aluminum-bound surface-active hydroxyl sites in the superficial layers and induce F- binding. As the C (0) increases, F-, along with other cations, is adsorbed to form a quasi-cryolite structure. At C (0)> 100 mg center dot L-1, new minerals precipitate and the product depends on the critical Al3+ concentration. At [Al3+]> 10(-11.94) mol center dot L-1, cryolite forms, while at [Al3+]< 10(-11.94) mol center dot L-1, AlF3 is formed. At low C (0) (0.3-1.5 mg center dot L-1), proton transfer occurs, and the F- adsorption capabilities of the clay minerals increase with time.

• 出版日期2011-6
• 单位南昌大学