The Preparation And Performance Study Of Polyaluminum Silicate Chloride (PASC) From Kaolinite Rock

This paper tends to design a process flow of preparing polyaluminum silicate chloride(PASC)from kaolin, study their flocculating settling characteristics and improve them through rearrangement of PASC, and study their application result on industrial water conditioning at the same time.Polyaluminum silicate chloride(PASC) were prepared in laboratory with kaolin and Na₂CO₃ under the process of high-temperature roasting, washing and acid dipping. During the preparing of PASC, we studied the effect of extraction ratio on different roasting temperature, roasting time, alkali grade, acid volume and particle size of kaolin, determined the optimal technological condition, and find some action mechanisms employing Zeta potential and XRD measurement.During the research of flocculation characteristics for PASC using kaolin as an object to be flocculated, the effect of different technological condition was studied systematically on the flocculation of kaolin suspending liquid, and defined the optimal use level of PASC was 8ml/L, roasting temperature was 900°C, roasting time was 40minute, the mass ratio of alkali and Na₂CO₃, acid volume was 60ml. It is found that PASC is a kind of flocculating agent with positive charge through Zeta potential measurements. The Zeta potential measurements showed that the addition of PASC can increase the zeta potential of kaolin.During the rearrangement of PASC, the chemical species distributions of PASC were determined by AL-Ferron complexation timed spectrophotometric. The experimental results show that it can enlarge the polymerization degree of PASC, improve their flocculation characteristics and prolong their period of storage through regulating pH of PASC. Otherwise, and it shows that SO₄^2- has great effect on flocculation characteristics of PASC, but Ca²⁺ not. Fe³⁺ can prolong period of storage of PASC.Otherwise, the technical process of preparing polymeric ferric sulfate(PFS) was proceed in laboratory, and studied the flocculation characteristic, determined that the volume of PFS was 4ml/L and optimal pH was 1.5,and explored preparing technology of polymeric ferric-aluminum silicate(PAFS)employing solid PASC and PFS.During water treatment experiment, PASC and PFS which prepared in laboratory were used in coal slurry, river sewage andcoke plant wastewater, and were compared with PAM and PAC. It was found that PAM and PAC was not as well as PASC and PFS for treating the same water, and dosing subsequence had effect on water treatment result. The flocculate agent should be used together comparison with be used individually. For coal slurry treatment, the volume of PFS was smaller and the transmittance of treated water was higher. But because of Fe3+ in PFS, the remove of colourity was lower for river sewage, and can not treat coke plant wastewater because Fe3+ was reacted with phenol. When using PASC, transmittance, the remove of colourity, the remove of COD and the remove of SS were all higher. Especially, while the volume of PASC was 2ml/L in river sewage, the sedimentation rate was fast and transmittance, the remove of COD and the remove of SS reached 94.3%, 93.06% and 89.05%. Comparison with other flocculate agent, PASC expresses its superiority.