PAC with the traditional inorganic polymer flocculant coagulant aluminum and iron salts can control the formation of the active ingredient, thereby controlling its flocculation performance compared with high efficiency and low toxicity, adaptable, low cost advantages.
The degree of polymerization PAC are influenced by many factors, but the most direct, is one of its greatest impact hydroxide content, so people typically Al and Cl ratio or alkalinity (also known as basicity) as its parameters to describe the degree of polymerization, but especially the latter more widely used basicity PAC is defined by the following formula: basicity B OH- / 3 Al3 * 100 where, OH- and Al3 respectively represents the molar concentration of aluminum hydroxide ions, not difficult to find, alkalinity also be expressed as: basicity B () m / 3 n * 100 there are also accustomed to aluminum ratio of hydroxyl (OH- / Al3) expressed , but substantially the same.
PAC is a mixture of a complex series of polymer aluminum, the most simple form of a dimer poly aluminum, which is generated by the hydrated aluminum ion was two octahedron, two of the original share of the hydroxyl-substituted the four water molecules linked together the two aluminum ions, which can be expressed as the formula:. Al2OH2H2O84 Since flocculating ability of the polymer with the charge brought is increased exponentially, and therefore, is a tetravalent polymerization flocculation of aluminum ions equivalent to ten times the trivalent aluminum ion monomer.
With the increase of alkalinity, aluminum and its degree of polymerization of polymeric cationic charge also brought a further increase. For example, the hexamer Al6OH12H2O126 with six positive charge, the average aluminum monomer carried a positive charge , but its aluminum monomer flocculation anionic species than with three positively charged aluminum monomers and dimers average with two positive charges are much stronger.
After the PAC coagulant treated leachate COD, turbidity, color and total suspended and polyacrylamide composite flocculant papermaking wastewater treatment, results showed that the addition of coagulant, stirring speed, stirring time, settling time best PAC dosage of 2 g / L, pH value of 7.5, the effect of aluminum on the CODCr removal rate. the results showed that the waste is adjusted 9.5 g / L, pH value of 7, when treated with PAC , COD, turbidity, pH value between 3 and 4, most of the waste liquid can be settling suspended solids.