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

作　　者：Junyi DU Daishe WU Huayun XIAO Ping LI 

机构地区：[1]Department of Environmental Science and Engineering,Nanchang University,Nanchang 330031,China

出　　处：《Frontiers of Environmental Science & Engineering》2011年第2期212-226,共15页环境科学与工程前沿（英文）

基　　金：This work was supported by the National Natural Science Foundation of China(Grant No.40601004).

摘　　要：This research investigates the adsorptionmechanisms of fluoride(F)on four clay minerals(kaolinite,montmorillonite,chlorite,and illite)underdifferent F^(-)concentrations and reaction times by probingtheir fluoride superficial layer binding energies and elementcompositions using X-ray photoelectron spectroscopy(XPS).At high F^(-)concentrations(C_(0)=5-1000 mg·L^(-1)),the amount of F^(-)adsorbed(Q_(F)),amount of hydroxidereleased by clay minerals,solution F^(-)concentration,andthe pH increase with increasing C_(0).The increases areremarkable at C_(0)>50 mg·L^(-1).The QF increases significantlyby continuously modifying the pH level.At C_(0)<5-100 mg·L^(-1),clay minerals adsorb H+to protonatealuminum-bound surface-active hydroxyl sites in thesuperficial layers and induce F^(-)binding.As the C_(0)increases,F^(-),along with other cations,is adsorbed toform a quasi-cryolite structure.At C_(0)>100 mg·L^(-1),newminerals precipitate and the product depends on the criticalAl^(3+)concentration.At[Al^(3+)]>10^(-11.94)mol·L^(-1),cryoliteforms,while at[Al^(3+)]<10^(-11.94)mol·L^(-1),AlF_(3) is formed.At low C_(0)(0.3-1.5 mg·L^(-1)),proton transfer occurs,andthe F^(-)adsorption capabilities of the clay minerals increasewith time.

关 键 词：clay mineral fluoride(F) adsorption mechanism X-ray photoelectron spectroscopy(XPS) 

分 类 号：O64[理学—物理化学]