Recycling of High-Purity Strontianite and Hematite from Strontium-Bearing Sludge

Abstract

Sr-bearing sludge is a hazardous waste that is commonly generated by nuclear power plants and mineral refining operations. In this work, Sr-bearing sludge was simulated and then cleanly recycled into high-purity strontianite with hematite nanoparticles as a byproduct via a novel hematite precipitation route. The sludge contained 26.1% Fe, 3.5% Sr, and Si impurities. After dissolution in 1.2 M nitric acid, the sludge was treated hydrothermally with the addition of glycol to precipitate Fe effectively. Without the addition of glycol, only 52% Fe was hydrothermally precipitated in the form of hematite aggregates. With the addition of glycol at the optimal M glycol/M nitrate molar ratio of 0.4, nearly 100% Fe was removed in the form of hematite nanoparticles with an average diameter of 50 nm, whereas over 98% of Sr was retained in the leachate. The generated hematite was highly purified with an Fe2O3 content of 95.23%. Sr was present at a high concentration of 3.9 g/L in the treated leachate and further precipitated in the form of strontianite with a purity of 96.8% through Na2CO3 addition. Tertiary butanol (TeB) exhibited a similar Fe removal rate as glycol even though its optimal M TeB/M nitrate molar ratio was 0.1, which was approximately one-fourth the optimal M glycol/M nitrate molar ratio. Fe removal involved spontaneous Fe3+ hydrolysis under hydrothermal conditions and was promoted by increasing the pH of the redox reaction between nitrate and glycol and/or TeB. The method reported here successfully enabled the resource recycling of Sr-bearing sludge to generate high-purity strontianite and hematite products without producing any secondary waste.

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

“…Given that the wastewater contained 171.6 mg/L TOC, the redox reaction between nitrates and organics also took place (Eq. 3) (Bian et al, 2020;Su et al, 2020), which accelerated the nitrate removal. By adding 0.5 g limestone, the precipitation reaction of sulfates to Ca 2+ was spontaneous and accelerated at high temperatures (Fu et al, 2018), leading to increased sulfate removal.…”