A novel method to synthesize polyaluminum chloride with a membrane reactor

Article type: Research Article

Authors: HE, Fei | JIA, Zhi-qian | PENG, Yue-lian | WANG, Pei-jing | LIU, Zhong-zhou

Affiliations: Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China

Note: [] Corresponding author. E-mail: zzliu01@yahoo.com

Abstract: Al_{13} or Al_b 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 little 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=305K 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 show that the Al_{13} content is equal to Al_b content. And our PAC product has shown better flocculation effects than the commercial product.

Keywords: membrane reactor, polyaluminum chloride

Journal: Journal of Environmental Sciences, vol. 16, no. 3, pp. 482-486, 2004