Immobilization of Chromium in Stainless Steel Slag Using Low Zinc Electric Arc Furnace Dusts

Abstract

A new synergistic treatment of stainless steel slag and low zinc content electric arc furnace (EAF) dusts is proposed to immobilize harmful chromium in stainless steel slag. The effects of ZnFe 2 O 4 addition on the mineralogic phase and chromium leachability of CaO-SiO 2-MgO-Al 2 O 3-Cr 2 O 3 synthetic slag were investigated to explore the feasibility of this method. The mineralogic phases in stainless steel slag were investigated by scanning microscopy equipped with energy-dispersive spectroscopy and X-ray diffraction. The leaching concentration values of chromium and zinc were evaluated according to an alkaline digestion for the hexavalent chromium (US-EPA-3060A) and toxicity characteristic leaching procedure (TCLP, US-EPA-1311) method, respectively. It was found that all synthetic slags mainly contain a-Ca 2 SiO 4 , merwinite and spinel phase, in line with the calculation results by FactSage. The crystallization of spinel and merwinite phases was enhanced by the addition of ZnFe 2 O 4 but suppressed the precipitation of a-Ca 2 SiO 4. It was revealed that the leaching concentration of chromium was depressed by adding ZnFe 2 O 4 and was far below the chemical limits defined in the French proposal for a criterion and evaluation methods for waste ecotoxicity (0.1 mg L À1). In addition, the zinc leaching concentration meets the sanitary landfill standard. The proposed synergistic treatment method was further validated on industrial stainless steel slags and EAF dusts. Experimental results indicated that the synergistic treatment method can immobilize chromium effectively and the final slags can be disposed of by sanitary landfilling or recycling as constructional materials. A schematic technologic route diagram of the synergistic treatment was also proposed.

Carbothermal Reduction of Stainless Steel Dust and Laterite Nickel Ore: Slag Phase Behavior Regulation and Self-pulverization Control Mechanism

“…31) In general, the current treatment processes have the problems of high energy consumption and low metal recovery ratio. [32][33][34][35] Laterite nickel ore, as a kind of low basicity, low grade and refractory ore, also has the problems of low metal yield and high energy consumption in the smelting process. [36][37][38][39] In this study, stainless steel dust was used as the raw material and laterite nickel ore was used as an additive to adjust the basicity of the slag component in the reduction process, and a composite carbon containing compact was prepared.…”

Recycled Steel Slag as a Porous Adsorbent to Filter Phosphorus-Rich Water with 8 Filtration Circles

“…The affinity of steel slag for phosphorus (P) ion binding has been studied to use by-products of the steel industry as a filter matrix to treat wastewater. Steel slag is obtained by the oxidation of steel pellets in an EAF [6]; it accounts for 15~20% of iron production. For example, the USA produces about 5.1 million tons of steel slag in a year [7]; in Europe every year nearly 12 million tons of steel slags are produced [8].…”

“…In fact, in some countries in the world, such as India [9] or Brazil [10], the utilization rate of this by-product is relatively low. Most of them are deposited in the slag storage field, thus causing much serious environmental trouble [6,11], e.g., soil and groundwater pollution. Steel slag is a by-product of the process of converting iron into steel, and it varies according to the raw material and process.…”

Immobilizing chromium in stainless steel slags with MnO addition

“…As the main by-product during stainless steel smelting, the global generation of stainless steel slags is approximately 15 million tons per year. [1][2][3][4][5] Since Cr-containing stainless steel slags are potentially hazardous Cr-containing materials, its recycling has been severely restricted. 6 Most stainless steel slags worldwide are landfilled, 7 where the Cr 3+ can potentially oxidize to Cr 6+ under long-term environmental exposures.…”

“…As the main by‐product during stainless steel smelting, the global generation of stainless steel slags is approximately 15 million tons per year 1‐5 . Since Cr‐containing stainless steel slags are potentially hazardous Cr‐containing materials, its recycling has been severely restricted 6 .…”