The Preparation Of Poly-aluminum Chloride With Membrane Reactor And Its Application

The content of Al_b in poly-aluminum chloride (PAC) is the most important index which decides the flocculation capacity of PAC. Therefore, researches have focused on how to prepare the PAC with high quantity of Alb. By far, the methods of PAC preparation, such as instantaneous-injection of base and micro-injection of base and so on, have many disadvantages involving the prepare process lack of continuous operation, uncontrollability and weak continuity of the addition of lye and then lead to low quantity of Al_b of PAC.In this paper, we use hollow fiber membrane reactor to prepare PAC owing to the large numbers of tiny pores on the membrane. This preparation method can operate continuously and add lye slightly and equably. Furthermore, it has a little cost without pollution.In the research, the double circulation is adopted, the lye flows in the monitor and the AlCl₃ solution flows in the lamella. The lye is added into aluminum chloride solution in a slight, well-proportioned and controllable way under the pressure difference, and then takes neutral reaction with aluminum chloride solution to prepare PAC. The final content of Al_b in PAC products is measured by Al-Ferron timed colorimetric method. The effects of various factors on the content of Alb in PAC products are studied thoroughly, such as B, the flow path of material solution, the flow velocity and concentration of AlCl₃ solution, the concentration of NaOH solution, the alkalescence of alkali material solution, the MWCO and the valid length of membrane reactor and so on. Furthermore, the micro-configuration of PAC is observed by STM and the conditions of preparing PAC are optimized. Finally, the PAC prepared by hollow fiber membrane is used to treat the model dye waste waters.By the experiment, we have obtained the optimal conditions of preparing PAC: the B is 2.0, the concentrations of NaOH solution and AlCl₃ solution are 0.2mol·L^-1 and 0.5mol·L^-1 respectively, and NaOH solution flows inside the membrane and the flow rate of AlCl₃ solution is 28.58ml·s^-1. In addition, the low MWCO of membrane reactor and short valid length of membrane reactor benefit to increase the quality of Alb. For the 100ppm dye solution, the flocculation effect reaches the best when the pH of the dye solution is 4.1. The result of experiment shows that the content of Al_b in PAC prepared by hollow fiber membrane reactor, which determines the flocculation of PAC, can reach as high as 90.18%. It is much higher than that prepared by other methods.