Competitive adsorption behaviors of arsenite and fluoride onto manganese-aluminum binary adsorbents

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 2017-09, Vol.529, p.185-194
• Main Authors: Wu, Kun, Zhang, Nan, Liu, Ting, Ma, Chao, Jin, Pengkang, Zhang, Furong, Zhang, Jin, Wang, Xiaochang
• Format: Article
• Language: English
• Subjects: Adsorption; Aluminum oxide; Arsenite; Competition; Fluoride; Manganese oxide
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2017.05.039

[Display omitted] •The characteristics of As(III)&F adsorption onto Mn-Al binary oxide (MABO) is elucidated.•The capability of As in competing for active sites with F varied with As speciations.•The change of MABO surface plays an important role in the competition between As(III) and F.•F not only competes with As(III) for active sites but also retards As(III) oxidation by Mn oxides. The combined contamination of arsenic (As) and fluoride (F) in groundwater poses severe health risks. However, little information is available on the simultaneous removal of As(III)&F, not to mention their competition behaviors. Hence, we investigated the characteristics of competitive adsorption between As(III) and F onto the surface of Mn-Al binary oxides (MABO). The co-adsorption behaviors of As(III/V)&F, including isotherm and kinetic characteristics, were influenced by As speciations, solution pH, and Mn/Al molar ratios. With sequential addition of As(V)&F, the non-exchangeable fraction for each ion was approximately equal to their initially adsorbed amounts, respectively. Moreover, the adsorption amount of As(V) or F in the rapid reaction stage was attributed to the surface complexation formation. By contrast, when As(III) and F were adsorbed sequentially, the As(III) molecules adsorbed in the rapid reaction stage was more vulnerable and easily replaced by F ions. Additionally, the non-exchangeable fraction for adsorbed As was mainly As(V), which was converted from As(III) via redox reactions. These results suggested that the competition between As(III) and F is quite different with that between As(V) and F onto MABO surfaces. Furthermore, F complexation formation not only inhibits the adsorption of As(III), but also suppresses the oxidative reactivity of MABO.