Coagulation Performance And Mechanism Of Poly-Al-Zn-Fe From Galvanized Aluminum-zinc Slag

In this work, a poly-Al-Zn-Fe (PAZF) coagulant was prepared by usingaluminum-zinc-slag as the main material, and its microscopic characteristics,coagulation performance and coagulation mechanism were investigated. This researchmainly conducted the following studies.The influences of polymerization temperature, time and pH on the preparationprocess of PAZF were studied by orthogonal experiments. The PAZF structure andsurface morphology were analyzed by some modern analytical technology, such asinfra-red spectrum, X-ray diffraction and scanning electron microscope. Thecoagulation performance of PAZF was investigated in treating a simulated dyeingwastewater and landscape water by Jar tests, in which the influence of dosage, pHvalue and settlement time were analyzed and the coagulation mechanism was alsoprobed.The results showed that pH was the greatest parameter for PAZF coagulationperformance, and was followed by polymerization time, and the influence ofpolymerization temperature was the smallest. The optimal preparation conditions forPAZF were as follows: mixed acid concentration was10%, dissolving temperaturewas90℃, dissolving time was3h, pH value was3and polymerization time was0,5h.The micro analysis results showed that PAZF was a kind of containing hydroxylwhich gathered with the new iron and aluminum inorganic polymer coagulant.Amorphous state and amorphous polymer was the co-existence of the body. PAZFstructure was compact. The mutual combination between the molecules formed along chain, and formed high degree of polymerization of interlaced with solublematerials or mesh structure together form surface shape structure. Around thenetwork structures, there was little small scattered polymer. So its adsorption andstrong ability were strong, and the subsiding speed was quick and effect offlocculation is good.When PAZF coagulant was used for the treatments of the dyeing and printing waste water, the formation of large flowers was rich and settlement speed is quick.The pH value range was wide. And chromaticity, turbidity, and COD can be removedeffectively. Turbidity, chromaticity and COD removal rate were respectively93.8%,83.32%and62.19%when dealing the deep blue acidic waste water, which were97.84%,84.44%and66.01%respectively when dealing the palm scattered processingwaste water. And when dealing the landscape water, turbidity, chromaticity and CODremoval rate were86.98%,82.39%and86.82%, respectively.Compared to the aluminum polymerization (PAC), PAZF gave a betterperformance than PAC at low dosage in treating the deep blue acidic waste water, inwhich PAZF gave a high removal of turbidity, color and CODCrwith low cost. For thescattered light brown waste water, the optimal dosage of PAZF was70mg/l andalmost gave the same removal rate for pollutants at this dosage to that by PAC atdosage of140mg/l. Therefore, the cost with PAZF was lower than that with PAC intreating the same wastewater. When the turbidity and COD removal rate was sameusing PAZF and PAC as coagulants, the dosage of PAZF was lower than that of PACin treating the landscape water. But the phosphorus removal by PAZF was lower thanthat by PAC.