Senegalese laterites for the treatment of arsenic-contaminated mining waters

Arsenic contamination of water is a global issue with significant health consequences in many countries. Several treatment solutions exist, but they are often costly. In this study, the adsorption of arsenic was tested using two natural laterites from Eastern Senegal (Massawa (MASS) and Sabodala (SAB) locations). Their mineralogy consists of kaolinite (23-40%), quartz (23-39%), hematite (23-16%), and goethite (5-8%). Several conditions of arsenic adsorption by these two laterites were tested using batch experiments, including contact time, pH, and the ratio between the mass of laterite and the volume of arsenic-contaminated solution. Results indicate high removal rates of arsenic over a wide range of pH conditions (2-7, 8) for both laterites. For a laterite mass/water volume ratio of 0.1 g/50 ml, arsenic sorption reaches equilibrium within 60 minutes of contact time for MASS, whereas this time is between 60 and 120 minutes for SAB. A volume of 50 ml of arsenic-contaminated solution containing 5.69 mg/l of arsenic (V) is treated in 60 minutes with 1.5 g of both laterites. This short equilibrium time, compared to many studies reported on laterites worldwide, allows for higher water throughput, making the treatment of arsenic-contaminated water more efficient. The adsorption kinetics are slow and follow the pseudo-second-order model, suggesting the presence of chemisorption (inner-sphere adsorption) for both laterites. These results provide valuable insights into the practical suitability of Senegalese laterites for treating mine waters, particularly in the context of Senegal.