An investigation into the prospects of arsenic(v) removal from contaminated groundwater using untreated bauxite ore

Abstract

Steady-state experiments were conducted on arsenic (V) removal from contaminated groundwater using two different grades of bauxite ore. The materials considered were refractory grade bauxite (RB) with high alumina and low iron content and feed bauxite (FB) with moderate alumina and high iron content. Adsorption studies were carried out for different parameters such as pH, adsorbent dosage, As(V) concentration and reaction time to establish optimum conditions. RB was found to be the better adsorbent compared to FB with a maximum As(V) adsorption capacity of 1.49 mg As(V)/g compared to 1.26 mg As(V)/g of FB. Both the adsorbents showed similar type of behavior with varying magnitude. As(V) adsorption was independent of the ionic strength suggesting an inner-sphere surface complexion mechanism. The kinetics of the As(V) adsorption could be best explained by pseudo-second-order rate equation. The adsorption was found strongly pH dependent, with maximum adsorption over a wide range of pH ∼ 4.0 to 7.5. The column study results showed that at a adsorbent bed depth of 30 cm and feed flow rate of 50 ml/h, the RB was capable of treating 256 bed volumes of As(V) contaminated water (C_o = 1.79 mg/L) before breakthrough (C_e = 0.01 mg/L).

Keywords:

• Adsorption
• bauxite
• adsorption isotherm
• intra particle diffusion
• column study.

Acknowledgments

The work was carried out as a part of AusAID Arsenic Mitigation Project funded by Murdoch University, Australia (Contract No 9779). The first author thankfully acknowledges the award of a Post Doctoral Fellowship from KIGAM.