Application of iron-coated sand and manganese-coated sand on the treatment of both As(III) and As(V)

In this study, manganese-coated sand (MCS) and iron-coated sand (ICS) were applied in the oxidation of As(III) and adsorption of As(V), respectively. ICS and MCS were prepared by mixing FeCl₃ and Mn(NO₃)₂, respectively, with Joomoonjin sand at 150°C. In the batch adsorption isotherms, adsorption of As(III) and As(V) onto ICS followed a Langmuir type. ICS showed a greater capacity in the removal of As(V) than As(III) and also in the removal of As(V) compared with MCS. Three different configurations of ICS and MCS were used to investigate the oxidation of As(III) and adsorption of As(V) in a column. In the homogenised system, arsenic breakthrough was approximately two-times delayed compared with the separately packed systems. After breakthrough of arsenic, concentration of As(III) in the effluents was below 40 ppb for the entire reaction period in all configurations, and most arsenic was identified as As(V) owing to near complete conversion of As(III) to As(V) by MCS. The catalytic activity of MCS on the oxidation of As(III) was maintained up to 700 pore volumes, which corresponds to the treatment of at least 300 mg As(III) based on the 1 kg MCS. Compared with the homogenised column, the released Mn(II) concentration from two-staged and four-staged columns was great for the entire reaction period. In the case where the same amount of ICS and MCS was packed in a filtration system, the homogenised column was identified as a better configuration compared with the two-staged and four-staged columns when considering the arsenic breakthrough time as well as the released concentration of Fe(III) and Mn(II).