Preparation of a novel inorganic polymer coagulant from oil shale ash

In this paper, a novel inorganic polymer coagulant was prepared from oil shale ash, and was adopted to treat municipal sewage. Effect of coagulants dosage on the turbidity and Chemical Oxygen Demand (COD) removal were examined. In addition, the structure and morphology of the prepared coagulants were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and infra-red spectra (FTIR), furthermore, the zeta potential of the sewage and the microscopic images of flocks were measured. The results indicate that the characterization and coagulation performance of the samples are affected by Al/Fe mole ratios and the type of lixiviant. The most of Fe3+ is not turned into the crystals, which means that the samples are not simple mixtures of raw materials but inorganic polymer compounds with iron, aluminum, silicon and other ions. When Al/Fe mole ratio is 0.71 or the 2HCl/H2SO4 mole ratio of the lixiviant is 1:1, the coagulation performance of the sample is better than that of the others. The integrated analysis suggests that the entrapment, adsorption and complexation abilities play important roles in coagulation process although the charge neutralization is weak. Also, the chain-net structure and the suitable size of polymer group are favorable for the entrapment, adsorption and complexation ability of the samples.