Arsenic Elimination from Water Solutions by Adsorption on Bone Char. Effect of Operating Conditions and Removal from Actual Drinking Water

Abstract

Consuming drinking water contaminated with As(V) represents a hazard to human health. Adsorption of As(V) onto bone char (BC) has been studied previously, but a detailed study is required for applying BC to remove arsenate present in drinking water. The effect of the operating conditions, water matrix, and presence of fluoride onto the adsorption capacity of BC toward As(V) were thoroughly investigated. The XRD examination confirmed the presence of hydroxyapatite in BC, and the TEM examination of BC showed the random piling of the layers of hydroxyapatite. The BC adsorption capacity was contrasted with that of reagent-grade hydroxyapatite, and it was found that the BC capacity was mainly attributed to its hydroxyapatite content. The BC capacity is augmented by diminishing the solution pH because of the rise of the electrostatic attraction between the arsenate in water and the positive charge of the BC surface. The adsorption capacity was improved by incrementing the temperature so that the adsorption of As(V) was endothermic. The adsorption mechanism of As(V) on BC comprised electrostatic attraction and ion exchange. The simultaneous elimination of fluoride and arsenate in drinking water samples in San Luis Potosi, SLP, Mexico, revealed that both pollutants could be effectively removed by adsorption on BC, and the presence of As(V) did not affect the adsorption capacity of BC toward fluoride. In contrast, the capacity of BC for adsorbing As(V) was enhanced in the drinking water compared with that of deionized water, and this synergistic behavior was due to a screening effect.