Total removal of Chromium (VI) from wastewater by anionic clays

Calcined anionic clay (CAC) called layered double hydroxide (LDH) was used to remove the potential pollutant chromium (VI) from wastewater; CAC was chosen for its higher adsorption capacity, its affinity for most pollutants, its non-toxicity and its non-regeneration of sludge. Kinetic study shows a rapid adsorption process, suggesting a high affinity between the pollutant and CAC. Isotherms shows that agree well with the Freundlich model, suggesting that the pollutant is retained in multilayer. The thermodynamic study indicates a physical interaction. The results of different techniques confirms the retention of Cr(VI) by intercalation between the sheets of reconstructed LDH phase. The elimination reaches 100% for an optimal mass ratio Cr(VI)/CAC of 8 with 2500 mg/g of the retention capacity. After six regeneration cycles, CAC has proven its recycling performance and efficiency for the total removal of chromate anions (CrO42-). Comparison with other adsorbents shows that CAC is promising for environmental protection.