Journals Proceedings

Abstract

The main aim of this study was the synthesis and characterization of alternative composite inorganic coagulants, resulted from the incorporation of polysilicates and ferric salts in the structure of commonly applied polyaluminum chloride (PACl) in the coagulation–flocculation (C/F) process, in order to increase its efficiency for water and wastewater treatment. The new product is called polyaluminum ferric silicate chloride (PSiFAC) and is synthesized under various experimental conditions and two different preparation methods (copolymerization, or composite polymerization). The major typical properties of the prepared coagulants were examined, i.e. pH, turbidity, conductivity and Al species distribution (e.g. Keggin- Al13), employing the ferron technique. The composition, structure and morphology of the composite coagulants were studied in detail using (among others) the application of FT-IR and SEM techniques. The results show that the new composite materials have high Al13 content (51%). The study of FT-IR spectra exhibit intensive peaks, among others, at around 1098– 1100 and 831–833 cm−1, which can be attributed to the stretching and bending vibration of Fe–OH–Fe and Al–OH–Al bonds, respectively in the coagulant, indicating the existence of the polymerization. SEM micrographs showed amorphous structures on the surface of composite coagulant, as well as the clinging block-shaped crystals, probably because of the formed NaCl. Overall, the FTIR and SEM analysis of the different PSiFAC samples indicate that the preparation method has no effect on the structure and morphology of the samples, but indicate certain differences in their physic-chemical properties. The most effective coagulants obtained were also used for the treatment of tannery wastewater to evaluate their performance