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

Description

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.