EAF渣矿相组成及其短期淋溶特性

Mineralogical Composition of EAF Slag and its Short-term Leaching Characteristics

采用XRD方法研究了EAF渣矿相组成,采用静态淋溶实验方法,研究了液固比、淋溶液初始p H值和淋溶温度对EAF渣短期淋溶特性的影响。结果表明,EAF渣中存在的主要矿物为镁硅钙石、硅酸二钙、钙铝黄长石、磁铁矿、尖晶石、绿铬矿和钙钛矿。短期淋溶条件下,EAF渣淋溶液呈现强碱性和一定的还原性,EAF渣淋溶液中铬质量浓度随着液固比的升高而有所降低,强酸或强碱性淋溶液会在一定程度上提高淋溶液中铬质量浓度,温度对淋溶液中铬质量浓度影响较小;淋溶液铬质量浓度不仅受铬富集相溶解反应平衡控制,也受到淋溶液酸性影响,酸性较强时利于渣中碱性氧化物Cr(OH)3的分解,碱性较强时利于Cr(OH)4-离子的生成;EAF渣淋溶液中的铬主要以三价态存在,六价铬和总铬质量浓度均低于《危险废物鉴别标准浸出毒性鉴别》(GB 5085.3—2007)限值,在一定程度上说明EAF渣的短期淋溶毒性风险较低。

The mineralogical composition of the EAF slag was analyzed by X - Ray method. Static leaching tests were performed to explore the influence of liquid - to - solid ratio, initial pH and temperature on the shor - term leaching characteristics of the EAF slag. The experimental results indicated that EAF slag mainly contained merwinite, magne- tite, larnite, gehlenite, eskolaite, spinel, eskolaite and perovskite. During the short -term leaching process, the leachates of EAF slag were alkaline and reductive, the chromium leaching concentration decreased slightly with the increase of liquid - to - solid ratio, the leaching concentration of chromium would be enhanced under the condition of strong acidic and alkaline leachant to some extent and slight evolution of chromium concentration as a function of tem- perature was observed in the batch leaching test. The Cr concentration in the leachate was controlled by the reaction equilibrium of Cr- enriched phases dissolution/precipitation. Moreover, Cr leaching was also significantly impacted by the acidic eharacteristics of the initial leachant. Stronger acid is favorable for the decomposition of Cr （ OH ） 3, while the formation of Cr（ OH）4- is easy in the stronger alkaline atmosphere. Trivalent chromium was the predomi- nant speciation of chromium in the EAF leachates. The concentrations of hexavalent chromium and total chromium were far lower than the limit values of Identification Standards for Hazardous Wastes - Identification for extraction toxicity （ GB 5085.3--2007 ）. It can be concluded that the leaching risk of EAF slag during the short - term leaching process was slight.