High-purity recycling of hematite and Zn/Cu mixture from waste smelting slag

Abstract

in this study, Zn/cu-bearing smelting slag was recycled via an integrated acid dissolution and hematite precipitation method. the slag was dissolved in nitric acid to generate an acid solution containing 23.5 g/L Fe, 4.45 g/L Zn and 2.81 g/L Cu, which was subjected to hydrothermal treatment with the addition of levulinic acid (LA). More than 99.95% of the initial Fe content was removed as hematite particles with diameters of approximately 200 nm, and the residual Fe concentration in the acid was 0.43 mg/L. The generated hematite contained 97.3% Fe 2 o 3 , 0.64% ZnO and 0.58% CuO. Greater than 99% of the initial Zn and Cu was retained in the acid and further precipitated as Zn/Cu-bearing solids by adjusting the solution pH to 9. The precipitated Zn/Cu-bearing solids contained 33.6% Zn and 21.7% Cu, whereas the Fe content was less than 0.2%. This paper is the first report of an environmentally friendly approach for recycling smelting slag without generating any hazardous waste.

Resource Recycling of Mn-Rich Sludge: Effective Separation of Impure Fe/Al and Recovery of High-Purity Hausmannite

“…When supernatant 1 was hydrothermally treated, Fe/Al removal occurred, where 1.4% Fe and 67.3% Al were removed from the solution (Figure a), demonstrating that Al removal took precedence over Fe due to the high concentration of Al. With Fe/Al removal, the pH of the solution also decreased from 0.5 to 0.3 due to the generation of H + in Al hydrolysis, and the nitrate concentration decreased from 70 to 32.2 g/L, which is consistent with the decomposition of nitrate at 220 °C …”

“…With Fe/Al removal, the pH of the solution also decreased from 0.5 to 0.3 due to the generation of H + in Al hydrolysis, and the nitrate concentration decreased from 70 to 32.2 g/L, which is consistent with the decomposition of nitrate at 220 °C. 30 When glucose was introduced in the hydrothermal system, the Fe removal efficiency was 2.6% with 0.3 g of glucose and considerably increased to 97.1% with 0.7 g of glucose. However, it gradually dropped to 40.6% with 1 g of glucose and 30.9% with 1.5 g of glucose.…”

“…Hence, Mn was extensively residual in the solution. In addition, the decomposition of nitrate also occurred at high temperature, with the generation of NO 2 and O 2 via eq , which led to the decrease in nitrate concentration. …”

“…Thus, fine boehmite rods disappeared, and the replacement of hematite by maghemite occurred at a glucose dosage of >1 g. Consequently, overdosed glucose had two effects: one was curbing reduction from Fe 3+ to Fe 2+ ; the other was restraining the generation of well-crystallized boehmite and hematite. Besides glucose, other organics, for example, methanol, ethanol, levulinic acid, and ascorbic acid, , also reacted with nitrate. Such a reaction also accelerated in the presence of enough H + and became slow with the increase in solution pH, , where the solution pH was controlled and the hydrolysis of Fe was effective.…”

High Performance of Commercial PAC on the Simultaneous Desulfurization and Denitrification of Wastewater From a Coal-Fired Heating Plant

“…It is reported that nitrates and sulfates cannot be decomposed at room temperature, and can be reduced to nitrogen gas and elemental sulfur by microbes via the biological denitrification route [xx], for example, in municipal wastewater treatment plants. However, the flue gas wastewater has high salinity and lacks organics, and it cannot be treated via the biological method because the high salinity raises the osmotic pressure of microbes, inhibiting their growth and the organics are important electron donors to biologically reduce sulfates and nitrates (Huo et al, 2020). Thus, the thermal treatment of flue gas wastewater was noteworthy.…”