A novel method to synthesize polyaluminum chloride with a membrane reactor

Al 13 or Alb is usually regarded as the most efficient species of polyaluminum chloride(PAC), the performance flocculant for water treatment. This paper was intended to report a new method to synthesize PAC with high content Al b, by using the membrane reactor. NaOH solutions were managed to permeate slowly through the micropores of ultrafiltration membrane into AlCl 3 solutions under the suitable transmembrane pressure(TMP). Meanwhile NaOH drops size was limited to nano scale, resulting in dramatical reduction of the characteristic diffusion time and great increment of contact interface between the strong base and Al ions in solution to favor the formation of Al(OH) - 4, the precursor of Al 13 , so few precipitates and much Al b are produced. When the initial concentration of AlCl 3/NaOH is 0 40/2 0 (mol/L), MWCO =10000, TMP =0 0085 MPa, T =305 K and B (molar ratio of OH -/Al 3+ )=2 25, the quantity of Al b attains about 80%. The results of 27 Al NMR determination showed that the Al 13 content is equal to Al b content. And our PAC product has shown better flocculation effects than the commercial product.