Mechanism Analysis of Cr(Ⅵ) Reduction by Coal Gangue in Acidic Wastewater
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摘要:
通过试验探讨了煤矸石与Cr(Ⅵ)反应的动力学行为以及作用机制。研究表明，煤矸石还原Cr(Ⅵ)的过程分为两个阶段：第一阶段为煤矸石中的菱铁矿和黄铁矿与氢离子作用生成Fe(Ⅱ)、S、H2S，由于该阶段为固—液反应，反应速率与传质速率密切相关，在搅拌条件下反应速率常数为0.169 mg/(L·min)，远大于静态条件下的反应速率常数0.048 mg/(L·min)；第二阶段为Cr(Ⅵ)的还原，通过元素分析，结合红外和XRD表征，说明菱铁矿和黄铁矿中的铁和硫元素最终被Cr(Ⅵ)氧化成Fe（Ⅲ）和硫酸根，而Cr(Ⅵ)被还原成低毒性的Cr(Ⅲ)。菱铁矿和黄铁矿均是煤矸石常见成分，根据上述研究和分析，将煤矸石用于含Cr(Ⅵ)废水的处理，不仅提高了煤矸石的综合利用效率，同时为处理含Cr(Ⅵ)废水提供了低廉高效的方法。
Abstract:The kinetic behavior and mechanism of the reaction between coal gangue and Cr(Ⅵ) were investigated. The study showed that the reduction process of Cr(Ⅵ) by coal gangue could be divided into two stages. During the initial stage, siderite and pyrite in coal gangue reacted with hydrogen ions to generate Fe(Ⅱ), S and H2S. Since it was a solid-liquid reaction, the reaction rate was closely related to the mass transfer rate. The reaction rate constant obtained under stirring condition was 0.169 mg/(L·min), much higher than 0.048 mg/(L·min) got under static conditions. The second stage was the reduction of Cr(Ⅵ). The results got from elemental analysis, infrared and XRD characterization showed that the iron and sulfur elements in siderite and pyrite were oxidized to Fe(Ⅲ) and SO42−, and Cr(Ⅵ) was reduced to Cr(Ⅲ) which is low toxicity . Siderite and pyrite are common components in coal gangue. According to the above research and analysis, the use of coal gangue for treating wastewater containing Cr(Ⅵ) not only improves the utilization efficiency of coal gangue, but also provides a cost-effective and efficient method for the treatment of wastewater containing Cr(Ⅵ).
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Key words:
- coal gangue /
- Cr(Ⅵ) /
- mechanism analysis
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图 1 动力学试验拟合曲线（A-E浓度依次为40、60、80、100、100 mg/L，A：始终搅拌，B-D：0-210 min搅拌后静置， E：始终静置）
Figure 1.
表 1 煤矸石主要成分及含量
Table 1. Main composition and content of coal gangue
/% 成分 SiO2 Al2O3 Fe2O3 MgO CaO SO3 TiO2 烧失量 含量 47.40 13.25 9.91 1.63 1.79 2.07 1.65 21.93 
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表 2 动力学试验拟合参数
Table 2. Kinetic experiment fitting parameters
分组 k/ (mg·L−1·min−1) c0/(mg·L−1) 拟合方程 R2 搅拌 静置 搅拌 静置 搅拌 静置 A −0.169 − 38.58 c=38.58−0.169t − 0.990 − B −0.176 − 56.00 c=56.00−0.176t − 0.939 − C −0.168 −0.033 78.71 c=78.71−0.168t c=78.71−0.033t 0.984 0.997 D −0.163 −0.042 98.34 c=98.34−0.163t c=98.34−0.042t 0.956 0.997 E − −0.048 95.86 − c=95.86−0.048t − 0.989
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表 3 不同条件下金属离子的浓度
Table 3. Concentration of metal ions under different conditions
/( mg·L−1) 元素 Cr(Ⅵ) Fe(Ⅱ) Cr Fe Ca Mg NC − 38.82 0.07 168.38 98.26 54.08 AC 0.67 4.33 40.14 168.79 97.94 54.62
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