Preparation of Fe(Ⅱ)-H₂O₂-impregnated granular activated carbon at different temperatures for arsenate removal from water

Granular activated carbon (GAC) modified by Fe(Ⅱ)-H₂O₂ incipient wetness impregnation at different temperatures are prepared by FeSO₄·7H₂0 and hydrogen peroxide (H₂O₂) via the incipient wetness for 24 h at 100 ℃ (Fe(Ⅱ)-24 h ) and the high temperature evaporation for 15 min (Fe(Ⅱ)-15 min).Fe(Ⅱ)-24 h and Fe(Ⅱ)-15 min are characterized by SEM and are compared for the adsorption behavior of the arsenate (1.1 mg/L).The SEM has shown that nano-iron hydroxides are formed on the surface of Fe (Ⅱ)(0.485 %)-24 h (0.485 % is the iron content of Fe (Ⅱ)-24 h，the same below) and that sintering distorted hydroxides are formed on the surface of Fe (Ⅱ)(1.35 %)-15 min.The high temperature evaporation for 15 min is favorable for iron to load on GAC.The iron use efficiency of Fe(Ⅱ)-24 h(108-142 mg/gFe) is two fold of that of Fe(Ⅱ)-15 min(57-63 mg/gFe).The arsenate equilibrium adsorption capacity of Fe(Ⅱ) (0.485 %)-24 h is better than the Fe(Ⅱ)(1.35 %)-15 min at pH 2-3.5 or 9-12，at the same time，the soluble iron at any particular pH released from the Fe(Ⅱ)(0.485 %)-24 h is less than that released from the Fe (Ⅱ)(1.35 %)-15 min.The presence of SO₄^2-，NO₃^-，ClO₄^-，or PO₄^3- inhibit the adsorption of arsenate， especially for phosphate，while the existence of Cl-(100 mg/L)and BrO₃^- promote the adsorption of arsenate.