Interaction of anionic pollutants with Al-based adsorbents in aqueous media – A review

Simultaneous removal of arsenic and fluoride by freshly-prepared aluminum hydroxide

“…The Al-based coagulants and adsorbents are practically valuable for the removal of fluoride [5][6][7], and the exchange between fluoride and the hydroxyl groups occurs on the surfaces of aluminum (hydro)-oxides. The formation of aluminum fluoride complexes (Al-F complexes) occurs at acidic condition [7][8][9], and this effect facilitates fluoride removal as compared to its direct adsorption onto Al(OH) 3 precipitates [7].…”

Defluoridation of groundwater using aluminum-coated bauxite: Optimization of synthesis process conditions and equilibrium study

“…The weight loss upon thermal pre-treatment of RB at different temperatures are given in Table 2. The increased surface area may also be a contribution from the conversion of gibbsite in RB to boehmite (upon calcination at temperatures above 200 C), the later which has a higher surface area Kumar et al, 2014). Table 2 shows the thermal pre-treatment also markedly improved the net Al coating, hence increased incorporation of gibbsite into GACB.…”

“…On the other hand, two types of OH À groups are found at the edge faces, that is the doubly coordinated OH À groups and also OH À groups that are coordinated to single Al 3þ ions. The singly coordinated OH À groups at the edge faces are believed to readily protonate to form reactive AlOH þ 2 groups, which acts as Lewis acids sites for anion adsorption (Goldberg et al, 1996;Kumar et al, 2014;Dobias, 1993;McBrlde and Wessellnk, 1988;Jodin et al, 2005). The present observation thus suggest the crystal structure of gibbsite incorporated by the Al coating procedure, presumably possess higher percentage of specific surface area of edge faces, hence more reactive sites for fluoride adsorption than the intrinsic gibbsite.…”

“…Thermal pre-treatment of RB prior to Al coating resulted in a strong increase in specific surface areas and pore volumes of GACB, which may be attributed to evolution of water and other sublimable substances in the RB, prior to the Al coating (Kumar et al, 2014). The weight loss upon thermal pre-treatment of RB at different temperatures are given in Table 2.…”

NOM Removal by Adsorption

“…Readers interested in a detailed discussion of the application of alumina in water treatment should refer to comprehensive reviews by Kasprzyk-Hordern (2004) and Kumar et al (2014). In general, as a hydrous alumina precursor is heated, hydroxyl groups are driven off, leaving a porous solid structure of activated alumina.…”