Studies On Removal Of Calcium And Magnesium From Aquous Solution Using A Novel Silica Mateial From Kaolin

White carbon black is a kind of white appearance, qualitative light, fluffy, and porous amorphous silica materials. Its composition can be expressed as Si O2·n H2 O, wherein the n H2 O exist in the form of surface hydroxylgroups. There were three processes for preparation of white carbon black, normally includinggas-phase process, precipitation process and dissociation process. The raw materials of the fist two methods are more expensive, and the non-metallic mineral as an ideal raw material is cheaper. Kaolin,which contains a large amount of silica, was used as a silica source for the synthesis of a novel silica material.In this paper, the calcined kaolin was then treated with sodium hydroxide solution. The vast majority of amorphous silica reaction with alkali went into the solution. The effect of the calcination temperature of kaolin, alkali concentration, reaction temperature and reaction time on the silicon dissolution rate was discussed. The optimum synthetic condition is confirmed by orthogonal experiments and the optimum were as follows:calcination temperature of 960 ℃, alkali concentration of 20 %, reaction temperature of90 ℃ and reaction time 90 min. Under the optimum condition, the dissolution rate could arrive at 60.50 %. Then the desilication solution was used as raw material to synthetic silica material by the method of precipitation. The impact of solution concentration,reaction temperature and time, aging time on the preparation of amorphous silica was studied. The optimum synthetic condition were as follows: the concentration of silica in solution of 12 g/L, reaction temperature of 90 ℃, reaction time of 90 min and aging time of 2 h. Silica synthesized under these conditions can conform to the state standards. The oil absorption value and surface area of white carbon black, respectively, reached of over2.8 m L/g and 127.4 m2/g. The characteristics of the white carbon black material was analyzed by Fourier transform infrared(FTIR), X-ray diffraction(XRD) and Field emission scanning electron microscope(FESEM). The spectral results indicated that the particle size of white carbon black materials was 40-50 nm.The study of performance of the white carbon black material in removing calcium and magnesium ions from aqueous solutions showed that the silica material synthesized from kaolin have potential capability to soften the hard water. The mass of adsorbent, the contact time and initial ions concentration have a great effect on calcium and magnesium ions removal, Meanwhile, the reaction temperature and rotate speed have impact oncalcium and magnesium ions removal either. The removal rate of the white carbon black(4 g/L and 8 g/L) in the solution of calcium ions(200 mg/L) and magnesium ions(100mg/L) arrived at 94.99 % and 62.32 %, respectively. The studied white carbon black adsorbents showed a higher selectivity for calcium adsorption compared with magnesium.