[A-GE28] Energy-Environment-Water Nexus and Sustainable Development

[AGE28-10] Characterization of arsenic adsorption onto laterite by batch experiments

*Ngoc Le Tran Bich¹, Kengo Nakamura¹, Akihiro Matsuno¹, Ken Kawamoto¹ (1.Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama City, Saitama Prefecture 338-8570, Japan)

Keywords:Laterite, Arsenic, Adsorption, pH dependent

Arsenic in drinking water can be a serious human health risk in the world. In developing countries, it has been reported that arsenic can cause a variety of human health problems in local populations. Various techniques have been devised for arsenic removal from drinking water, including sand filtration, membrane filtration, and the use of adsorbents. The adsorption technology is considered the most suitable option because of its very high removal efficiency, cost-effectiveness, and low secondary waste generation. Laterite has been focused on as a natural and easily available adsorbent for arsenic removal in developing countries. The laterite is known to change it is surface charge properties when calcined and solution pH due to being rich in iron and aluminum oxides. This characteristic affects the adsorption and desorption of arsenic in drinking water. The laterite is due to metal oxides and hydroxides, which can control the adsorption and desorption of arsenic by changing the pH of the arsenic solution. Our laterite was collected in Vietnam. The adsorption tests by batch were carried out using raw laterite (RL) and heat-treated (heated at 500°C for 1 hour) laterite (TTL) from three particle size fractions (0.25-0.6, 0.6-2, and 2-4.75 mm). In the adsorption tests, the initial pH of the solutions varied from pH 2, 4, 6, and 8. Adsorption tests showed that laterite was able to remove more than 90% of arsenic up to 300 mg/L under all conditions by RL and TTL. The Langmuir adsorption isotherm was applicable to solution concentrations up to 3000 mg/L. It is suggested that the adsorption of arsenic on laterite is by monolayer adsorption. However, the adsorption of arsenic on laterite in pH 4 solution was unstable, and the amount adsorbed was reduced in RL and TTL. In the future, it is necessary to study the desorption characteristics of adsorbed arsenic and the regeneration of laterite with adsorbed arsenic.