Preparation And Application Of Titanium-containing Polysilicate-aluminium-iron Coagulant From Red Mud

Coagulation method is one of the most effective methods for the pretreatment ofprinting and dyeing wastewater, but less for water-soluble dye molecules. The red mud is akind of strong alkaline harmful waste residue with valuable metallic elements. Thus, it is auseful resource. The aim of the study was to produce an effective cougulant for treating themethylene blue simulated wastewater. The results of the study were as follows:The liquid titanium-containing polysilicate-aluminium-iron coagulant was preparedby copolymerization of TiOSO4,poly-silicate and pickle liquor of red mud. Theexperimental results show that: Under the optimized acid leaching conditions of sulfuricacid concentration8mol/L, liquid-solid ratio14mL/g, temperature80℃, time80minand NaCl dosage0.10g/g (dried red mud), the leaching rates of Fe and Al were88.25%and73.21%respectively. Comparison of several commonly used acid leaching kineticsmodel concluded that red mud acid leaching reaction accorded with unreacted shrinkingcore model. Accord with the leaching of iron ion diffusion control of the chemical reaction,reaction apparent activation energy of46.98kJ/mol. And, aluminum ion reaction belongedto the product layer diffusion control and response of the apparent activation energy of27.68kJ/mol.The study on preparation and application of T-PSAF showed that the optimiumconditions of the concentration of SiO2was2%, the silicic acid activation pH was5,n(Fe+Al)/n(Si), n(Fe+Al)/n(Ti) was0.3as the same, curing pH was4, curing time of8h.The homemade coagulant was used to treat the methylene blue simulated wastewater.when coagulant dosage of25mL/L and decolourization rate could reached89.89%. Withthe increasing concentration of methylene blue from150mg/L to200mg/L, the decolori-zation rate can reach more than99%. Under the70℃low temperature drying, we couldget the solid T-PSAF coagulant. Compared with the homemade coagulant, heavy metalcontent in the polymeric ferric sulfate was as the standard values, the result had not beenfound in excessive amounts of heavy metal ions. Several common dye wastewater with coagulant in adding the same amount of cases for methylene blue simulated wastewater of10mg/L, the T-PSAF was the best.The coagulation performance of T-PSAF was analyzed by FTIR (fourier transforminfrared spectrometer) and SEM (scanning electron microscope) and reagent method, inwhich the reagent method showed that iron, aluminum and silicon had formed in theprocess of hydrolysis of complicated hydroxyl polymer. Compared with homemade PSAFand T-PSAF coagulant infrared spectrum, we could found that the T-PSAF spectrum peakshad formed the Fe/Al-O-Si and Ti-O-Si. It indicated that the Ti ion not only existed in theform of monomer but also participated in the polymerization of coagulant. The SEMshowed that T-PSAF had more specific surface area and obvious layered structure.