T108 Arsenic Occurrence and Fate in Hydrogeologic Systems II

Monday, 17 October 2005
1:30 PM - 5:30 PM

ARSENIC SORPTION ONTO LATERITE IRON CONCRETIONS FROM PRESTEA, GHANA

Paper number: T108-12
Program: Technical Sessions
Time: 4:15 PM – 4:30 PM

Authors

Abstract

We investigated the sorption capacity of arsenic onto Prestea Ghana laterite iron concretions through column and batch experiments. Laterite iron concretions, which form by deep tropical weathering consist of 63.8% Fe2O3, 11.75% Al2O3, 9.46% silica, 1.21% TiO2 and clay minerals.

Adsorption capacity for 1.18mm laterite grains was calculated to be 2.19mg/g for As V and 2.56mg/g for As III. Adsorption of both As III and As V was found to be pH dependant and the maximum arsenic removal for both species was achieved at neutral pH range. Characteristic adsorption isotherms were determined and found to fit sufficiently the typical Langmuir equation. Arsenic sorption by laterite must be due to the high percentage of iron and aluminum oxides that it contains. Oxides and oxyhydroxides of iron and aluminum are known to be strong arsenic adsorbents. The combined effect of these oxides in the laterite explains the high sorption capacities of the laterite for arsenic.

The results of this study show that Prestea laterite removes arsenic and is currently being used to develop an inexpensive water purification system for rural communities in tropical Ghana.