Study on the preparation of polysilicate ferric flocculant and its treatment of high turbidity tailings water

In this study, an inorganic flocculant polysilicate ferric (PSF) was prepared with steel pickling waste liquid and industrial sodium silicate. The morphology and structure of PSF were analyzed by FTIR, XRD, and metalloscope. Results indicated that PSF is a polysilicic acid composite flocculant, and presented a network of cross-linked branches structure. The effect of Fe/Si molar ratios, flocculant dosage, different coagulants, and the initial pH on the coagulation behaviors of PSF were investigated by flocculation experiment. In addition, the formation of particle flocs in the water treatment process was observed with aid of PVM instrument. The results showed that the flocculation effect of PSF with the Fe/Si molar ratio of 1.5 was better than that of other coagulants, and the formed flocs under the same conditions were larger and compact. With a settling time of 10 min, the supernatant transmittance of kaolin suspension can reach 94.4% at a dosage of 0.8 g/L. Compared with natural sedimentation, the sedimentation rate of tail mud increased by 63.0%. From the results of flocculant characterization, zeta potential and PVM images, it can be inferred that Fe ions formed hydroxyl iron ions with positively charged by oxidative hydrolysis complexation. The charge neutralization by positively charged iron polymer has a significant effect, especially under acidic conditions. Furthermore, adsorption bridging of high molecular iron silicon polymers with branchlike structures is considered to play a vital role in high turbidity tailings water treatment. [Display omitted] •An inorganic flocculant polysilicate ferric (PSF) is prepared from pickling waste liquid.•The morphology of PSF shows a cross-linked branching structure.•In comparison, PSF has a more efficient flocculation effect.•Charge neutralization and adsorption bridging play the vital role in tailings water treatment.