Characteristics of nanosized polyaluminum chloride coagulant prepared by electrolysis process

Polyaluminum chloride (PAC) has become a focus of many studies involving coagulation because of its advantages over traditional coagulants. In this study, a novel method involving an electrolysis process for preparing of PAC was developed. The products were characterized using 27Al NMR spectroscopy, dynamic light scattering (DLS) and transmission electron micrograph (TEM). Results indicated that the electrolysis process provided favorable conditions for the formation of significant quantities of active species (Al13 polymer) at relatively high concentrations of total Al (AlT) (0.2–2.0 mol l−1). For each concentration of AlT, there was an optimum molar ratio of OH/Al (n) for formation of Al13. The Al13 species was stable for more than 6 months in solution when the n value was <2.0. However, in solutions with n values above 2.2, the Al13 species gradually converted to other polynuclear forms that were not detectable by 27Al NMR spectroscopy. The results of DLS and TEM showed that the particles existing in PAC prepared by the electrolysis process were in the nanometer size range.