Optimization of the aluminum based compound flocculant preparation conditions and fluorine removal performance validation by response surface method

Abstract

The aluminum based compound flocculant was prepared with components such as polyaluminum chloride (PAC), calcium oxide (CaO) and polyaluminosilicate ferric oxide (PSAF) by adopting mixed and compound method. On the basis of single factor experiment, the main factors affecting the preparation of aluminum based compound flocculant were selected, and the preparation conditions were optimized through Box-Behnken design experiment and response surface analysis. The results showed that the quadratic polynomial model had significant regression, but the loss of fit term was not noticeable. The determination coefficient R2 is 0.9603, which indicated that the model had good fit. The optimum preparation condition of the aluminum based compound flocculant was as follows: the mass ratio of PAC:CaO:PSAF was 8:4:5. When the influent initial fluorine content was 4.0∼6.0mg/L, the dosage of the flocculant was 0.85mg/L, and the initial pH value was 7.5, the removal rate of fluoride ion (F−) reached 92.95%, the fluoride ion content in the supernatant was less than 1.0mg/L, and the relative error with the predicted value of the model was 2.31%. The response surface curve optimization model was reliable.