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An innovative method for synergistic stabilization/solidification of Mn2+, NH4+-N, PO43− and F− in electrolytic manganese residue and phosphogypsum

Shu, Jiancheng, Chen, Mengjun, Wu, Haiping, Li, Bobo, Wang, Bin, Li, Bing, Liu, Renlong, Liu, Zuohua
Journal of hazardous materials 2019 v.376 pp. 212-222
ammonium nitrogen, calcium, fluorine, heavy metals, leaching, magnesium, magnesium ammonium phosphate, magnesium oxide, manganese, pH, phosphogypsum, solidification, temperature
Electrolytic manganese residue (EMR) contains large quantities of manganese (Mn2+) and ammonia nitrogen (NH4+-N). Phosphogypsum (PG) contains plenty of phosphate (PO43−), fluorine (F−) and some heavy metals. Separate storage of EMR and PG could seriously damage the ecological environment. In this study, synergistic stabilization/solidification (S/S) of EMR and PG was studied. The effects of EMR:PG mass ratio, S/S pH, solid-liquid ratio and temperature on the concentrations of NH4+-N, PO43−, Mn2+ and F− in the leaching solution, and the characteristics of EMR and PG were studied. Meanwhile, the synergistic S/S mechanisms of EMR and PG, and leaching test were investigated. The results showed that the concentrations of F−, PO43−, NH4+-N and Mn2+ in the leaching solution were 4.5 mg/L, 13.6 mg/L, 55.5 mg/L and 0.8 mg/L, respectively, when the mass ratio of EMR to PG was 1:2 and the pH was 9.0 adjusted by MgO after 20 days S/S. Manganese was mainly solidified as Mn3(PO4)2·7H2O and Mn(OH)2, and ammonia nitrogen was mainly stabilized as struvite; fluorine was mainly stabilized as (Mn, Ca, Mg)F2, and phosphate was mainly solidified as (Mn, Ca, Mg)3(PO4)2 and (Mn, Ca, Mg)HPO4. The leaching test results showed that PO43− and NH4+-N were reduced to 13.6 mg/L and 55.5 mg/L, respectively, and the concentrations of all the measured heavy metals and F− were within the permitted level for the GB8978-1996 after 20 days S/S.