Adsorption Isotherms of Arsenic on Conditioned Layered Double Hydroxides in the Presence of Various Competing Ions

Abstract

Analysis of effluents from various power plants indicates that, in addition to arsenic (As), these effluents also contain such ions as fluorides, nitrates, chlorides, carbonates, sulfates, and phosphates. Adsorption is considered the method of choice for the treatment of waste streams containing As. Of concern, therefore, is the impact of such competing anions on the capacity for As adsorption of the various materials utilized. In this work, we systematically investigated the effects of such ions on the As removal capacity of layered double hydroxides (LDHs), a class of materials investigated by our group and others as effective adsorbents for As and other heavy metals. The adsorption of As in the presence of each of these competing ions on LDH follows the extended Sips isotherm. It is concluded from our study that, of all of these ions, fluorides and nitrates have the least effect on As adsorption, followed by chlorides, carbonates, sulfates, and phosphates. Phosphates, in particular, have a very strong impact.