Removal of Cr(VI) from water by modified attapulgite adsorbent

Ethylenediamine modified attapulgite(EDA/ATP) adsorbent was synthesized by using clay-based adsorbent ATP as carrier. The EDA/ATP composite adsorbent was characterized by FTIR and TGA. The adsorbent was applied to the adsorption of Cr(VI) in aqueous. The effects of initial concentration of Cr(VI) solution, adsorption time, solution pH and the anion concentration Cl⁻ and PO₄³⁻ on the adsorption of Cr(VI) were studied. The FTIR and TGA results show that EDA has been successfully grafted onto the surface of ATP. The adsorption experimental results show that at 25℃ the maximum adsorption capacity of EDA/ATP composite for Cr(VI) is 153.78 mg·g⁻¹, and the adsorption reaches equilibrium within 800~900 min. The adsorption experimental data conform to Freundlich adsorption isotherm model and the pseudo-second-order kinetics. The initial pH of solution is ranging from 2 to 10. With the increase of pH, the adsorption capacity first increases and then decreases. When the pH is 3, the adsorption capacity reaches the maximum adsorption amount. PO₄³⁻ has greater effect on the adsorption than Cl⁻, and the maximum adsorption capacity decreases by 83 mg·g⁻¹ when the concentration of PO₄³⁻ is 20 mmol·L⁻¹. The experimental results show that EDA/ATP composite can be used as a potential adsorbent for Cr(VI) in water treatment.