Abstract:

In order to prepare polyaluminum chloride（PAC） with high effective content and stable performance，and effectively shorten the preparation time，a new gel method was used to prepare PAC.The preparation conditions of polyaluminium chloride by the new gel method were optimized as follows：aluminum hydroxide was reacted with slightly excessive sodium hydroxide under slightly boiling conditions to obtain a clear sodium metaaluminate solution.Hydrochloric acid was dropped into sodium metaaluminate solution to neutralize excess alkali.Then，under the conditions of heating and stirring，a quantitative amount of hydrochloric acid was added to the solution for reaction to obtain PAC products with a certain basicity.The results showed that when n（NaOH）/n［Al（OH）₃］ was 1.50，sodium meta-aluminate solution could be prepared in only 15 minutes.When the concentration of hydrochloric acid solution was 6.19 mol/L，the dropping speed was 15.00 mL/min，the heating temperature was 80 ℃，and the heating time was 0.5~1.0 h，the effective content of Alb in polyaluminum chloride was more than 80%.The prepared polyaluminum chloride was used for coagulation treatment of algae containing water samples.The results showed that when the dosage of n（OH^-）/n（Al³⁺）=2.0 homemade polyaluminum chloride was 6.6 mg/L，the turbidity removal rate of algae containing water samples with initial turbidity of 10~40 NTU was more than 90%，and the residual aluminum concentration was less than 0.20 mg/L.The new gel method could effectively shorten the preparation time，and the product had high effective content and good coagulation effect.

Key words: new gel method, polyaluminum chloride, alkalinity, algae containing water, coagulation