Simultaneous adsorption of fluoride and hexavalent chromium by synthetic mesoporous alumina: performance and interaction mechanism

Abstract

Combined pollution by fluoride (F−) and hexavalent chromium (Cr(vi)) in water bodies causes much environmental concern and its treatment is of the utmost importance.

Chromium VI and Fluoride Competitive Adsorption on Different Soils and By-Products

“…In the previous study, carried out in individual (simple) systems for Cr(VI) and F − separately (Romar-Gasalla et al [13]), the highest F − adsorption corresponded to forest soil, pyritic material, pine bark, and oak ash, with values between 30 and 40 mmol kg −1 , which represented between 60-72% of the highest concentration of F − added, while pine bark, pine sawdust, and pyritic material showed the highest adsorption of Cr(VI) for the highest concentration of Cr(VI) added, with 69, 40, and 32 mmol kg −1 , representing 98, 68, and 55%, respectively. Li et al [2] found higher affinity for F − than for Cr(VI) in synthetic alumina gels, while Mohapatra et al [38] obtained the opposite result in alumina nanofibers. The behavior observed in the present study can be related to the different composition of the sorbent materials used, and to their pH values (Table S1, Supplementary Material).…”

“…Li et al [2] found for synthetic alumina gels that the coexistence of F − and Cr(VI) in solution decreased Cr(VI) adsorption, but enhanced F − adsorption, due to the fact that alumina has higher affinity for F − than for Cr(VI), and Cr can form ≡CrOH 2 + groups, which could be new adsorption sites for F − . Deng et al [48], studying competitive adsorption in fibers impregnated with cerium, found that F − adsorption increased in a binary system in relation to a simple system, whereas Cr(VI) adsorption decreased (i.e., Cr(VI) favored F − adsorption, but F − hindered Cr(VI) adsorption).…”

“…In recent years there has been growing concern regarding F − and Cr(VI) pollution, due to both substances being transported into effluents from industries related to the extraction of minerals, foundries, dyes and pigments, semiconductors, and glass manufacturing [1,2]. These effluents can reach surface-and ground-waters by direct discharge or after passing through soils.…”

“…Although different methodologies have been developed to remove F − and Cr(VI) from waters, such as precipitation, electrocoagulation, ion exchange, or electro-dialysis, the use of adsorbent materials has been considered as the most economical and sustainable alternative [2]. Previous works have dealt with individual adsorption of F − and Cr(VI), separately, both in soils and in different waste materials [3,[7][8][9][10][11][12][13].…”

“…Previous works have dealt with individual adsorption of F − and Cr(VI), separately, both in soils and in different waste materials [3,[7][8][9][10][11][12][13]. In addition, some studies focused on simultaneous retention of F − and Cr(VI), using adsorbents such as a chitosan-alginate aluminum complex (CSAlg-Al) [4], or synthetic mesoporous alumina [2]. However, there is not enough information on simultaneous retention of these two anions in different soils, as well as on the adsorbent capacity of different byproducts derived from industrial activities.…”