Experimental study on the removal of Cr(Ⅵ) from water by biochar-based sulfide modification loaded with nano-zero valent iron
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摘要:
为研发治理地下水Cr(Ⅵ)污染的可行除铬材料,以碳热法制得生物炭负载纳米零价铁(BC-nZVI),并通过对BC-nZVI硫化改性制备得到改性材料(M-BC-nZVI),采用除铬容量、铬铁比(Cr/Fe)、反应活性分析M-BC-nZVI的除铬优势,通过模拟柱试验建立失效速率模型,从而推算M-BC-nZVI完全失效的除铬容量,最后与相关文献数据进行对比,分析M-BC-nZVI除Cr(Ⅵ)的应用可行性。结果表明:M-BC-nZVI材料的除铬容量、Cr/Fe、拟一级反应速率常数(kobs)分别是BC-nZVI的1.86倍、1.95倍和3.00倍,因此相对于BC-nZVI来说M-BC-nZVI更具除铬优势;各模拟柱在运行过程中无明显堵塞情况,且随着进水浓度的升高,M-BC-nZVI的失效速率常数变大。当失效除铬速率为初始除铬速率的1.0%、进水Cr(Ⅵ)浓度为5 mg/L时,除铬容量最高,可以达到12.70 mg/g;对比M-BC-nZVI与其他文献报道的铁基材料及铁基改性材料的Cr/Fe可知,M-BC-nZVI的Cr/Fe为其他文献的1.06~42.06倍,故从材料的除铬性能来看,M-BC-nZVI应用于可渗透反应墙处理地下水Cr(Ⅵ)污染可行。
Abstract:In order to treat Cr(Ⅵ) pollution in groundwater, biochar-supported nano-zero valent iron (BC-nZVI) was prepared by the carbothermal method, and the modified material (M-BC-nZVI) was prepared by vulcanization modification of BC-nZVI. The chromium removal capacity, Cr to Fe ratio (Cr/Fe) and the reactivity of M-BC-nZVI were used to analyze the superiority of M-BC-nZVI for chromium removal. A failure rate model was established through the simulated column test to calculate the chromium removal capacity of M-BC-nZVI that completely failed. Finally, the application feasibility of M-BC-nZVI in removing Cr(Ⅵ) was analyzed by comparing it with the relevant studies. The results showed that the removal capacity, Cr/Fe and pseudo-first-order reaction rate constant (kobs) of M-BC-nZVI were 1.86, 1.95 and 3.00 times higher than those of BC-nZVI, respectively. Therefore, compared with BC-nZVI, M-BC-nZVI had certain advantages in various aspects. Each simulated column had no obvious blockage during operation, and the failure rate constant of M-BC-nZVI increased with the increase of influent concentration. The highest chromium removal capacity (12.70 mg/g) reached when the failure chromium removal rate was 1.0% of the initial chromium removal rate and the influent Cr(Ⅵ) concentration was 5 mg/L. By comparing Cr/Fe of M-BC-nZVI with iron-based materials and iron-based modified materials reported in other studies, Cr/Fe of M-BC-nZVI was 1.06 to 42.06 times that of other studies. Therefore, based on the chromic removal performance of the material, it was feasible to apply M-BC-nZVI to permeable reactive barrier to treat Cr(Ⅵ) pollution in groundwater.
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Key words:
- biochar /
- nano-zero-valent iron /
- vulcanization modification /
- hexavalent chromium /
- simulated column
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表 1 模拟柱除铬速率拟合参数
Table 1. Fitting parameters of simulated column chromium removal rate
反应模型 模拟柱 k1/h−1 k2/mg−1 R2 拟一级反应 1号 0.011 6 0.800 6 2号 0.010 9 0.960 6 3号 0.009 0 0.949 0 拟二级反应 1号 0.048 2 0.952 3 2号 0.042 2 0.972 7 3号 0.035 4 0.962 2 表 2 除铬总量与除铬容量计算结果
Table 2. Calculation results of total amount and capacity of chromium removal
(失效除铬速率/初始
除铬速率)/%进水Cr(Ⅵ)浓
度/(mg/L)质量/g 除铬总
量/mg除铬容量/
(mg/g)1.0 15 11.9 135.27 11.37 10 11.0 132.06 12.01 5 11.1 141.02 12.70 2.5 15 11.9 109.42 9.20 10 11.0 111.25 10.11 5 11.1 121.76 10.97 5.0 15 11.9 89.91 7.56 10 11.0 95.44 8.68 5 11.1 106.96 9.64 -
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