Coagulation performance and microstructural morphology of a novel magnetic composite coagulant for pre-treating landfill leachate

Abstract

A novel magnetic composite coagulant, prepared from nano-Fe3O4 and poly-aluminum chloride, was introduced to pre-treat mature landfill leachate. The coagulation performance of the coagulant as well as its microstructural morphology was discussed. Coagulation experimental results revealed that the coagulation performance of the landfill leachate using the new coagulant was better than that using poly-aluminum chloride alone, with COD and color removals above 60 and 68%, respectively. Based on the analysis of three-dimensional excitation–emission matrix spectrum, the fluorescence signals of treated leachate are totally reduced by the magnetic composite coagulant. The components of dissolved organic matters in the wastewater are removed in different degrees. Fourier transform infrared spectra analysis shows that the magnetic composite coagulant, which is a multi-core polymer with hydroxyl ligands and nano-Fe3O4, has a complex valence and crystal structure. Besides, X-ray diffraction pattern analysis indicates that the chemical composition of the magnetic composite coagulant is not changed significantly, which has comprehensively combined the chemical characteristics of both nano-Fe3O4 and poly-aluminum chloride, whereas the specific surface area of the novel magnetic composite coagulant effectively increased by nano-Fe3O4 particles under the analysis of scanning electron microscope spectral. The specific surface area analysis indicates that the magnetic composite coagulant is interconnected by narrow cracks and holes and has a high specific surface area and developed pore structure, which is also similar to the typical porous-type materials. Therefore, the nano-Fe3O4 compounded with poly-aluminum chloride leads to a larger specific surface, smaller average pore diameter, and more pore volume of the novel coagulant.