Adsorption Behaviors Of Inorganic Anions In Water On Calcined LDH

As the economy develops, the water environment in China has been suffering from a growing problem of pollution. In most of areas the water pollution had exceeded the capacity of the water environment.Through the unremitting efforts of the scientists,the technology of water treatment had been greatly advanced in the devices,the technique and the methods.The pollutant components in the water become more and more complex,so the traditional method wouldn't be able to work efficiently.In recent years,with the rapid development of material science,the sorbing material become a new way to solve the problem. Inorganic anions, such as PO43-,Cl-and SO42-, are commonly-occurred aqueous pollutants, among which SO42-and Cl-are relatively more difficult to be tackled with. They are highly detrimental to both the environment and the human beings if they were emitted into the environment directly without being eliminated in advance. While adsorption has the advantages of simple technique,low cost,steady process,non-second-pollution,so it's effective on the removal of the pollution of inorganic anions in water.Granulated Mg-Al layered double hydroxides(Mg/Al-LDH) was prepared by commercial Mg/Al-LDH and the shaped binder.The granulated Mg-Al calcined layered double hydroxides(Mg/Al-CLDH) was obtained by calcined at500℃for2hours.The materials are characterized by X-ray diffraction.The static adsorption capacities of the granulated Mg/Al-CLDH were evaluated by adsorbing inorganic anions(PO43-,Cl-and SO42-)from aqueous solution.Furthermore,whetherthe presence of the organic pollutant affects the adsorption for inorganic anions was discussed.The optimum conditions for preparing granulated Mg/Al-LDH were:mass ratio of Mg/Al-LDH and Na2SiO3·9H2O was95:5,the pH value was10,reaction time was1hour,and solid-liquid ratio was1:20.The static adsorption of Mg/Al-CLDH for inorganic anions was studied.The influence factors on absorbent effect were studied,including reaction time,initial pH value and adsorbent dosage.The adsorption isotherm equations and the adsorption kinetics models were studied.The equilibrium times of Mg/Al-CLDH for PO43-,Cl-and SO42-were3hours,5hours and2hours.The best adsorbent dosages of Mg/Al-CLDH for PO43-,Cl-and SO42-were3g/L,4g/L and3g/L. Mg/Al-CLDH has a good adsorption capacity for inorganic anions in a wide pH value.According Langmuir adsorption isotherm equation, the maximum adsorption capacities of Mg/Al-CLDH for PO43-,Cl-and SO42-were120.4819mg/g,53.1915mg/g and67.1141mg/g.The adsorption of Mg/Al-CLDH for PO43-,Cl-and SO42-followed the pseudo-second order model. The adsorption of Mg/Al-CLDH for inorganic anions is still effective while the presence of the organic pollutant in the waste water. According to the experimental results of X-ray diffraction, the adsorption of inorganic anions of Mg/Al-CLDH was resulted from the memory effect of this material.