Optimization Of Preparation And Application Of B And Mg Based Poly-silicate Flocculants

Flocculation process has the advantage of simple technology, high efficiency, lower cost and wide application, is widely used in water treatment technology one of the technologies. To further enhance the performance of the flocculation and flocculent, this paper proposes the introduction of boron and magnesium in the traditional poly aluminum silicate iron on the basis of existing research.Single factor experiments were executed to study the main factors affecting the poly-silicate preparation process, silicon concentration, activation pH and activation time, and the flocculants preparation process, n(Fe+Al):nSi, n(B+Mg):nSi and ripening time. Then, the center value of each factor was obtained, according to which response surface methodology was used to the preparation conditions of the poly-silicate and flocculants and the flocculation conditions of the novel flocculants. Printing and dyeing wastewater treatment results showed that the combination of optimum preparation conditions and flocculation conditions was achieved. Details are as follows.In the poly-silicate preparation process, the Box-Behnken central composite (BBD) experimental design method was used to design the experiments by the factor of Si concentration, activation pH and activation time, and the COD removal efficiency and chroma removal rate results were obtained based on the experimental program which was carry out. Then, it using response surface methodology (RSM) to analyze the various response values, according to a quadratic polynomial regression model fitting the experimental data. The optimal conditions was achieved by optimizing the model, in which the Si concentration is0.52-0.55mol/L, the activation pH value is3.2-3.3, and the activation time100-105min. The validation experiments showed that the flocculants by adding this poly-silicate has a good behavior to the wastewater treatment.After the determinates of the poly-silicate preparation conditions, BBD methods was also used to design the experiments of flocculants preparation by the factor of n(Fe+Al):nSi, n(B+Mg):nSi, and the ripening time. According to the BBD plan, each experiment was carried out, and the response results of the removal of COD and chroma was obtained to run the RSM method. The optimal preparation conditions was determined that n(Fe+Al):nSi is5.06, n(B+Mg):nSi0.48, ripening time2.08d. Using this new flocculants to the treatment of dyeing wastewater, the best results showed that the COD removal efficiency of87.08%, the color removal rate of95.36%.In order to determine the dosing volume of the new type flocculants, the Central Composite Designs was used to design the experiment of the dosage and the wastewater pH. The RSM method results that the optimal dosage is0.63mg/L, and the wastewater pH is6.1. The validation experimental results show that the flocculants can obtain the best flocculation effect under this optimal condition, and the wastewater treatment operating costs is reduced because of the less using of flocculants.The stability of the new flocculants was studied by observing the flocculants changes over time, and the results show that the new flocculants performance is less affected by time, and it has a better stability. To further determine the boron and magnesium on the flocculants performance improvement, the boron and magnesium results show that these improved the stability and flocculation performance of the flocculants to some extent. Compared to three commonly used flocculants polymeric ferric sulfate, poly aluminum chloride and poly-silicate aluminum ferric, the experimental results show that novel flocculants is better than other three to deal with a different dye wastewater and coking wastewater respectively.The use of RSM method to the poly-silicate flocculants preparation factors and to determine the optimum flocculants dosage, take full account of the interaction between the various influencing factors. The experimental results show that the introduction of elements such as B, Mg has a more significant role for improving the flocculants performance, and it has some reference value to guide the reuse of wastewater and water resources utilization and protection works.