La-aong Wuthiphun, Prawith Towatana, Surapol Arrykul, and Virasakdi Chongsuvivatwong

pp. 401 - 411

Abstract

      Arsenic adsorption efficiency of soil covering materials (lateritic soil, limestone powder, lime and fly ash) on arsenic-contaminated soil obtained from Ronpiboon District, Nakhon Sri Thammarat Province to solve arsenic air pollution problem was investigated using batch experiments. The four types of the aforementioned soil covering materials were examined to determine their arsenic adsorption efficiency, equilibrium time as well as adsorption isotherms.
       The results revealed that among soil covering materials mixed with arsenic-contaminated soil at 10% w/w, the efficiency of arsenic adsorption of fly ash, lateritic soil, lime and limestone powder were 84, 60, 38 and 1% respectively. The equilibrium time for lateritic soil at pH 4 was achieved within 4 hrs, whereas pH 7 and 12, the equilibrium time was 6 hrs. For fly ash, 2 hrs were required to reach the equilibrium at pH 12, while the equilibrium time was attained within 6 hrs at pH 4 and 7. Furthermore, lateritic soil possessed
high arsenic adsorption efficiency at pH 7 and 4 and best fit with the Langmuir isotherm. The fly ash showing high arsenic adsorption efficiency at pH 12 and 7 fit the Freundlich isotherm at pH 12 and Langmuir
isotherm at pH 7.
        This indicated that lateritic soil was suitable for arsenic adsorption at low pH, whilst at high pH, arsenic was well adsorbed by fly ash. The Freundlich and Langmuir isotherm could be used to determine quantities of soil covering materials for arsenic adsorption to prevent arsenic air pollution from arseniccontaminated soils.