Study On The Coagulation Property Of Humic Acid Removed From Water By Chlorinated Polyaluminum Prepared By Forced And Spontaneous Hydrolysis

Flocculants play a very important role in water treatment process.Inorganic polyaluminium chloride flocculant is widely used in water treatment.There are two types of hydrolysis menthods to prepare polyaluminium:one is forced hydrolysis method,another is spontaneous hydrolysis method.The products prepared by forced hydrolysis method are K-Al₁₃ and Al₃₀ with core structure of AlO₄,while the products of spontaneous hydrolysis are P-Al₁₃ and Al₄&Al₁ with core structure of AlO₆ without AlO₄.K-Al₁₃ has been widely used in the process of flocculation.The application of Al₃₀ solution is rarely due to the limitations of its preparation conditions.P-Al₁₃3 has no application in flocculation because of less study.The prepare method,stability and morphological transformation of P-Al₁₃ have been studied by our research group.In this paper,the comparison of flocculation between P-Al₁₃,K-Al₁₃ and Al₃₀ on humic acid water were studied.Two different simulated water samples were studied:One is humic acid simulates water sample,another is the kaolin-humic acid simulated water sample.Coagulation contrastive experiments of K-Al₁₃ solution,high Al₃₀ content solution,P-Al₁₃ solution?^{4 o}C?,P-Al₁₃ solid,forced hydrolysis solution with B=0.7 and spontaneous hydrolysis solution with B=0.7 were carried.The results indicated that flocculating performance of P-Al₁₃ solid was superior to P-Al₁₃ solution,spontaneous hydrolysis solution with B=0.7 was superior to forced hydrolysis solution with B=0.7,P-Al₁₃ was superior to K-Al₁₃ and Al₃₀.It is mainly manifested in the following aspects.?1?The effect of water p H on flocculation was explored with optimal dosage of flocculants.The removal rate of humic acid of spontaneous hydrolysis products was higher than that of forced hydrolysis products.Meanwhile,spontaneous hydrolysis products had more effective removal efficiency in a wide pH range.?2?The effect of agitation conditions on the dynamic characteristics of the flocs was explored.The aspect of the lag time,growth rate,strength factor and regrowth factor etc.were determined.The flocs formed by spontaneous hydrolysis products had significant advantages.The growth rate of P-Al₁₃ is seven times of K-Al₁₃.P-Al₁₃ was not affected by agitation rate when the crushing rate was 100rpm.The flocs formed by P-Al₁₃ had the characteristics of strong stability,large and dense flocs and not easily broken.?3?With the addition of Ca²⁺,the dosage of K-Al₁₃,P-Al₁₃ and Al₃₀ can be decreased to obatain the same removal rate,and the flocs became more compact.Its promoting effect of Ca²⁺on P-Al₁₃ coagulant is better than that of K-Al₁₃ and Al₃₀.?4?Flocculation mechanism of P-Al₁₃ was mostly owing to adsorption,bridging and sweep flocculation.Flocculation mechanism of K-Al₁₃ was mostly owing to adsorption,bridging and electric neutralization.Flocculation mechanism of Al₃₀ was mostly owing to adsorption,electrical neutralization and adsorption bridging.