Coprecipitation of Arsenate with Metal O (1)

Arsenic mobilization in soils is predominantly governed by sorption/desorption processes, alongside the possibility of arsenic coprecipitation with aluminum and/or iron in natural environments. This study aims to investigate the mineralogical, chemical composition, and surface properties of aluminum-arsenate coprecipitates while exploring the sorption of phosphate and loss of arsenate from these materials. Aluminum-arsenate coprecipitates were synthesized under varied conditions (pH 4.0, 7.0, or 10.0, and As/Al molar ratios of 0, 0.01, or 0.1) and aged at 50 °C for 30 or 210 days. The experiment determined that without arsenate, gibbsite and bayerite formed at respective pH levels. However, in the presence of arsenate, poorly crystalline precipitates were observed. The results revealed that the nature and chemical composition of the aluminum precipitates were significantly affected by initial pH, molar ratio, and aging duration. Dissolution experiments indicated that arsenate was primarily located in the short-range ordered precipitates, and phosphate sorption was influenced by the presence of arsenate, demonstrating a complex interaction between these species. Overall, while significant amounts of phosphate could partially displace arsenate, the overall desorption remained less than 30%, suggesting a strong occlusion of arsenate within the precipitate matrix.