响应面优化制备粉煤灰基PASC混凝剂性能与表征

研究了以粉煤灰为原料制备聚硅氯化铝（PASC）混凝剂的影响因素、产品性能和微观结构.选取A（碱化度）、B（n（Si）：n（Al））、C（聚合温度）和D（反应时间）对混凝高岭土模拟废水后透光率进行四因素三水平响应面实验.最终优化方案为：A为1.18，B为5.64，C为47.40℃，D为2.48h，透光率预测值达86.58%，验证试验均值相对误差仅为0.18%，模型相关系数为0.9984，表明RSM优化模型可靠.混凝剂性能随投加量增加而不断增加，最终趋于稳定；随废水pH值增大呈现先增大后减小的趋势.XRD分析PASC主要物相为氯化钠，非晶态衍射峰形成预示着浸出液和聚硅酸加碱聚合形成了新的无定形物；FT-IR测试表明聚硅酸与Al³⁺及其水解产物间络合形成了金属-OH等非离子键；SEM显示产品为高聚集度和枝化度的空间网状结构.

Response surface method optimization of preparation fly ash based polysilicate aluminum chloride coagulant: performance and microstructure characterization

This paper investigates the factors that influence the preparation of polysilicate aluminum chloride coagulant using coal fly ash and their performance and microstructure. Four factors(basicity, n(Si):n(Al), polymerization temperature and reaction time) and three levels of response surface experiments were carried out, which regarded the transmittance of Kaolin simulated wastewater as the evaluation index. Results show that the optimum scheme when the basicity was 1.18, the n(Si):n(Al) was 5.64, the polymerization temperature was 47.40℃, and the reaction time was 2.48 hours. At the optimum theme, the predicted value of transmittance reaches 86.58%, the relative error of all the verification experiments was 0.18%, and the correlation coefficient of the model is 0.9984, which indicated the RSM optimization model is reliable. The performance of coagulant increases continuously with the increase of dosage, and tends to be stable eventually. With the increase of pH of wastewater, it increases first and then decreases. X-ray diffraction test indicates the formation of sodium chloride and new amorphous polymers which through the polymerization reaction of fly ash leachate and polysilicic acid. The infrared tests illustrates that a large amount of nonionic complex state (such as metal-hydroxyl groups) occurs between polysilicate acid and Al³⁺ and it's hydrolysate. The SEM micrograph shows that the product presents a three-dimensional reticular structure, with high level of aggregation and branches.