Characterization of flocs generated by preformed and in situ formed Al₁₃ polymer

详细信息    查看全文

• 作者：Chengzhi Hu ; Guixia Chen ; Huijuan Liu ; He Zhao ; Jiuhui Qu
• 关键词：Coagulation ; Al13 polymer ; Flocs ; Surface structure ; Polyaluminum chloride ; Al coagulant
• 刊名：Chemical Engineering Journal
• 出版年：2012
• 出版时间：15 July, 2012
• 年：2012
• 卷：197
• 期：Complete
• 页码：10-15
• 全文大小：566 K

文摘

During coagulation process, preformed and in situ formed Al₁₃ polymer are the predominant aluminum hydrolysis species at the optimal pH condition for polyaluminum chloride (PACl) containing high content of Al₁₃ and AlCl₃ (AC), respectively. The structure and morphology of the flocs generated by preformed and in situ formed Al₁₃ polymer were investigated from the viewpoint of the relationship between Al speciation and flocs surface structure. The results showed that at pH 6 the predominant composition of PACl and AC flocs were Al₁₃ polymer aggregate and amorphous Al hydroxide, respectively. The flocs generated by preformed Al₁₃ polymer had a better crystalline structure than those from in situ formed one, while they had smaller size and smoother surface structure than those formed by in situ formed Al₁₃ polymer. During weak acidic pH condition and at high dosage of Al coagulant adsorption onto precipitated Al hydroxides was the main pathway for kaolin particle removal. Preformed Al₁₃ polymer showed a stronger charge neutralization ability, while the flocs generated from in situ formed Al₁₃ polymer exhibited a higher adsorption capacity for kaolin particles. Al species distribution during coagulation process governs the floc character and coagulation efficiency of Al coagulant. The present study further conduces to the understanding of coagulation mechanism and puts forward a basis for coagulant selection during water treatment process.