Study of the Efficiency of Two Clays Soils for Cyanide Removal in Water: Kinetic and Equilibrium Modelling

In Burkina Faso, water resources in mining area are sometime polluted by cyanide. To mitigate this pollution, clays have been collected in Kaya and Koro and used as adsorbents to remove cyanide in waters. Experiments have been carried out using batch adsorption with synthetic cyanide solutions. The influence of operating conditions has been evaluated on adsorption capacity. From experimental results, the particle size did not have a great impact on the cyanide removal rate up to 150 µm in diameter. The increase of initial pH from 6.5 to 11 led to a decrease in the cyanide removal capacity adsorption from 9.5 to 7.6 and the volatility rate of cyanide from 6 to 2%. When the initial concentration was increased between 5.5 and 224 mg/L, this resulted an increase in adsorption capacity from 0.8 to 23.5 mg/g and a decrease in the removal rate from 95 to 47%. The contact time increased with the temperature, it was respectively 3; 4 and 8 H for Koro and 4; 6 and 12 H for Kaya respectively at 20; 30 and 40°C. The adsorption of cyanide was described by an exothermic and spontaneous process occurred on monolayer through a chemisorption following a pseudo-second order kinetic.