The Study Of Adsorption Of Arsenate And Arsenite By Hydrous Ceric Oxide In Aquatic Conditions

In view of taking full advantage of rare earth materials and development and utilization of high effective arsenic adsorption material,this research had studied the adsorption/desorption of arsenate and arsenite onto hydrous ceric oxide(HCO).And the adsorption mechanisms were also investigated.It was found that the adsorption capacity of HCO absorbent was constant around a value of 110mg/L over a wide pH range(4.0～9.0).The arsenite was better adsorbed in slight basic medium while arsenate was favorably adsorbed in an acidic pH range. The kinetics of arsenic adsorption by HCO involved an initial fast adsorption process followed by a slower uptake process as time progresses.The adsorption data fit the Langmuir isotherm and its linearized form well.The thermodynamic data revealed that the adsorption was a spontaneous,endothermic and entropy increasing process. The standard enthalpy changes(△H~0) for arsenate and arsenite were 22.02 and 20.42kJ/mol,respectively.The adsorption capacity of arsenate and arsenite did not increase much along with the minishing particle diameter of HCO.And the effect of coexist ions in water were tiny to the adsorption capacity.The TCLP results showed that the spent material was suitable for discharge in landfill deposits.We chose NaOH solution to desorption the arsenic and the best qualification was 50mL 2mol/L of NaOH solution.Both the arsenate and arsenite had their maximum desorption capacity in one hour.Regeneration experiment of HCO powder indicated that the HCO adsorbent was feasible for using repeatedly.The breakthrough volumes for As(Ⅲ) and As(Ⅴ) are 180BV and 140BV.The FTIR analysis demonstrated that the characteristic adsorption made a very important effect during the adsorption of As(Ⅲ) and As(Ⅴ) by HCO,and the substitution of Ce-OH groups made a very important effect during the adsorption of As(Ⅲ) and As(Ⅴ) by HCO.