Argon Plasma Treated Phosphatic Clays for Efficient Heavy Metal Pb(II) Immobilization

Phosphatic clays, one type of phosphorite industry wastes, could induce environmental issues and geological disasters when they are piled in the open air. Previous research demonstrated that phosphatic clays usually exhibit poor performance in heavy metal immobilization mostly due to low phosphate content. Thus, phosphatic clays could not be applied in practical heavy metal remediation without pretreatment. If the adsorption performance of phosphatic clays could be improved, employing phosphatic clays for heavy metal immobilization may act as an eco-friendly, economic way to not only reutilize phosphorite industry wastes but also remedy environmental heavy metal pollution at the same time. In this study, we propose an argon plasma treatment approach to remarkably improve the effectiveness of phosphatic clay performances in heavy metal immobilization. The optimal Pb(II) sorption capacity of 66.7 mg g^-1 can be obtained at pH 6 and 25°C by using 15-min argon plasma treated phosphatic clays, which is two times as large as those of the untreated phosphatic clays and almost reaches those of raw apatite minerals. Moreover, the Pb(II) desorption ratios of Pb(II)-adsorbed phosphatic clays are also reduced by 30%-60% at different pH conditions. Therefore, applying argon-plasma technique to transform waste phosphatic clays into efficient heavy-metal sorbents is a promising road to phosphorite waste reclamation and environmental remediation.