REMOVAL OF ARSENITE AND ARSENATE IONS FROM AQUEOUS-SOLUTION BY BASIC YTTRIUM CARBONATE

A new method has been developed to remove arsenite and arsenate ions f rom aquatic systems by using basic yttrium carbonate (BYC). Various pa rameters such as pH, anion concentration and reaction time were studie d to establish optimum conditions. The removal by adsorption of arseni te and arsenate ions was found to be > 99% depending on initial concen tration in the pH range of 9.8-10.5 and 7.5-9.0, respectively. The ars enate was also removed by precipitation at pH lower than 6.5 due to di ssolution of BYC. The kinetic study shows that the adsorption follows the first order reaction. The adsorption isotherms of these anions wer e also studied at different temperatures. The equilibrium data fit wel l in the Langmuir model of adsorption. The Langmuir constants were cal culated at different temperatures and the adsorption capacity for both anions increases with temperature. Anions such as Cl-, Br-, I-, NO3- and SO42- have no interference in the removal process. The mechanism o f the removal by adsorption was interpreted in terms of the surface ch arge and ligand orientation of BYC. The method was applied on syntheti c wastewaters. Arsenite was oxidized to arsenate by 3% hydrogen peroxi de. The yttrium was regenerated as basic yttrium carbonate. Copyright (C) 1996 Elsevier Science Ltd.