AOD渣中铬的连续淋溶特性及其动力学模型的构建

Sequential Leaching Characteristics of Chromium from AOD Slag and Its Kinetic Model

为评价AOD（氩氧脱碳炉）渣的淋溶毒性,采用连续20 d的静态淋溶试验,研究了中性和酸性淋溶液对AOD炉渣中Cr（铬）淋溶特性的影响,以累积溶出率构建了Cr淋溶动力学模型.结果表明：在连续淋溶过程中,淋溶液p H（9.6-11.5）始终保持碱性,DO（溶解氧）基本处于饱和状态,淋溶液还原性呈降低趋势;随着淋溶时间的延长,淋溶液中Cr^6＋、TCr和Cr^3＋的累积溶出率呈增加趋势,不同初始淋溶液p H（2.0、3.0、4.0、5.0、6.0、7.0）下,连续淋溶20 d时Cr^6＋、TCr和Cr^3＋的累积溶出率分别是淋溶2 d时的10.1-22.2、7.5-15.6、6.3-17.1倍;与中性和弱酸性淋溶液相比,连续淋溶20 d,酸性较强的淋溶液中Cr^6＋、TCr和Cr^3＋的累积溶出率分别为其3.1-6.6、1.6-3.2和1.8-2.1倍;与短期静态淋溶相比,连续淋溶增加了淋溶液总量,尽管ρ（Cr）变化较小,但TCr累积溶出率显著增加;双常数速率、抛物线和指数模型均可拟合淋溶液中Cr^6＋、TCr和Cr^3＋的累积溶出率,其中,抛物线模型的相关系数均在0.99以上,是最佳模型.AOD渣中Cr的连续淋溶动力学模型的构建可为不锈钢渣中Cr的淋溶毒性及其生态风险评价奠定试验和理论基础.

Twenty days sequential leaching experiments were carried out to investigate the leaching characteristics of chromium from AOD slag by neutral and acidic leachate. A kinetic model of chromium leaching was established based on the accumulated leaching ratio, which provides an experimental foundation for leaching toxicity assessment of AOD slag. It was shown that during the sequential leaching period, the leachates maintained strong basicity, with their pHs being 9.6-11.5, while the dissolved oxygen was saturated and the reducibility of leachate trend declined. The accumulated leaching ratio of Cr^6＋ , total chromium and Cr^3＋ increased rapidly with increasing leaching time. When the initial pHs of leachate were 2.0, 3.0, 4.0, 5.0, 6.0 and 7.0, the accumulated leaching ratios of Cr^6＋ , total chromium and Cr^3＋ in the leachates of 20 d sequential leaching were 10. 1-22.2, 7.5-15.6 and 6.3-17.1 times, respectively, than those in the leachates of 2 d sequential leaching. Compared with the neutral and weakly acidic leachate, the accumulated leaching ratio of Cr^6＋ , total chromium and Cr^3＋ in strong acidic leachate were 3. 1-6.6, 1.6-3.2 and 1.8-2. 1 times, respectively, when the sequential leaching time was 20 d. Different from the short-term static state leaching process, the leachate volume increased in the sequential leaching process. The total leaching chromium ratio significantly increased though the chromium concentration in the leachates of sequential leaching process was stable. The accumulated leaching ratios of Cr^6＋ , total chromium and Cr^3＋ in leachate could be fitted with double constant, parabolic and exponential models. Compared with the other two models, the parabolic model was more suitable to describe the accumulated leaching ratio of Cr^6＋ , total chromium and Cr^3＋ from AOD slag, which was the optimizing model for predicting the leaching quantity of chromium in sequential leaching tests, and provided an experimental and theoretical foundation for the leaching toxicity and eco-risk assessment.