Xiao Zhengyuan¹， Lyu Chaojie¹， Wang。Zhonghui¹， Wu Junshu¹， Wang Jinshu¹， Lyu Pai²

1.State Key Laboratory of Materials Low⁃Carbon Recycling， College of Materials Science & Engineering， Beijing University of Technology， Beijing 100124， China； 2.Department of Microsystems， University of South-Eastern Norway， Campus Vestfold， Raveien 215， 3184， Horten， Norway

Abstract

Objective A large amount of steel slag （SS） is generated annually. This type of solid waste is rich in metallic components， yet its resource utilization efficiency remains to be improved. In addition， after the reductive detoxification of highly toxic Cr（VI）， the slow re-oxidation of the resulting Cr（III） products often leads to pollution rebound—commonly known as “yellowing back.” Therefore， the simultaneous removal of Cr（III） products is one of the key challenges in the deep treatment of Cr-containing wastewater.

Methods A two-step “acetic acid activation-Na₂S treatment” method was employed to sulfurize the SS surface.Pre-treatment of the raw steel slag （RSS） material began with mechanical ballmilling at a ball-to-slag mass ratio of 7：3， followed by sieving through a 300-mesh sieve to eliminate oversized particles. The obtained slag underwent three cycles of cleaning with deionized water to remove surface impurities， and was then dried at 60 ℃ for 12 h to obtain the RSS powder. Subsequently， 3 g of RSS powder was dispersed in 60 mL of aqueous solution containing 30 mL of acetic acid. The homogeneous suspension was transferred to a thermostatic water bath shaker maintained at 60 ℃ for continuous reaction over 5 h. The resultant brown suspension was filtered without any post-washing treatment and dried at 60 ℃ for 12 h， ultimately yielding the acetic acid-activated SS designated as 30HRSS（where “30” indicates the volume of acetic acid used）. Finally， 2.2 g of Na₂S was dissolved in 5 mL water， and then 55 mL ethanol was mixed with the Na₂S aqueous solution. 0.3 g of 30HRSS was added to the prepared Na₂S solution， and the mixture was reacted in a thermostatic water bath shaker maintained at 60 ℃ for 5 h， yielding the NaFeS₂-modified SS product designated as 30HRSS_s.

Results and Discussion The pristine RSS displayed irregular bulk granular morphology with coarse particles. After sulfuration， 30HRSS_s exhibited a denser internal structure and consolidated solid particles. This process resulted in the enhancement of specific surface area （22.4 m²/g， 30HRSS_s）， which was nearly 10 times higher than that of RSS.30HRSS_S had both Cr（VI） reduction and Cr（III） adsorption capabilities.Under the optimal conditions （30HRSS_S dosage： 30 mg； initial Cr（VI） mass concentration： 10 mg/L in 60 mL； time： 60 min； temperature： room temperature）， when the initial solution pH was 3~5， the residual Cr（VI） mass concentration was below the detection limit （0.01 mg/L）， and the removal efficiency of totalchromium （Cr（T）） reached 100% within 60 min. Under neutral to alkaline conditions （pH=7~10）， the Cr（T） removal efficiency remained above 82% after 90 min of reaction.30HRSS_S also exhibited good anti-interference ability against common coexisting ions（NO₃⁻， SO₄²⁻，CO₃²⁻， Ca²⁺， and Mg²⁺）in polluted water.

Conclusion This study realizes the efficient resource reuse of the endogenous residual iron components in SS，and the developed material for SS-based Cr（T） removal provides an effective technical scheme for the deep and long-term treatment of Cr-containing wastewater.Stability assessments under simulated natural oxidative conditions（e.g.，δ-MnO₂， light irradiation）confirm that the Cr removal product exhibits high environmental stability，effectively avoiding the risk of secondary pollution caused by the re-oxidation of Cr（III） products.Therefore，the obtained material has good environmental benefits and application potential.

Keywords： steel slag； surface activation； total chromium removal

Get Citation:Xiao Zhengyuan， Lyu Chaojie， Wang Zhonghui， et al. Preparation of sodium iron thiosulfate-modified steel slag and its total chromium removal performance［J］. China Powder Science and Technology， 2026， 32（6）： 1-12.

Received：2026-05-18， Revised： 2026-07-13， Online： 2026-09-09。

Funding： The research was supported by Jing-Jin-Ji Regional Integrated Environmental Improvement-National Science and Technology Major Project（Grant No.2026ZD1212800).

CLC No.：X756；TB4

Type Code：A

Serial No.：1008-5548（2026）06-0001-12