Study on catalytic degradation of methylene blue by biochar supported nano zero-valent iron and its mechanism analysis(生物炭负载纳米零价铁催化降解亚甲基蓝性能研究及机理分析)

To improve the catalytic ability of nano zero-valent iron in a Fenton like reaction system and reduce the agglomeration of nano zero-valent iron materials, the liquid phase reduction method was used to prepare biochar loaded nano zero valent iron materials (nZVI@BC). The material was characterized and the methylene blue was degraded to explore the material properties, the optimal degradation conditions and the action mechanism. The results showed that nano zero-valent iron had been successfully and evenly distributed on the surface of biochar. The prepared material was of high purity and good stability. In the degradation optimization experiment, the optimal reaction condition for degradation of 100 mg·L-1 methylene blue solution was 25 ℃, the initial pH=3, the dosage of nZVI@BC is 30 mg·L-1 and the dosage of H2O2 is 4 mmol·L-1. Under this condition, methylene blue solution can be almost completely degraded in 10 minutes. It had found that hydroxyl radicals played a major role in the degradation process. The chromogenic functional groups first broke, followed by the destruction of the aromatic ring structure, and ultimately completed degradation. And the material had a good recycling performance. After three cycles, the removal rate of methylene blue was still above 85%. In actual printing and dyeing wastewater treatment experiments, nZVI@BC had a good wastewater treatment effect. When the dosage of H2O2 was 0.9 mmol·L-1, the dosage of nZVI@BC was 60 mg·L-1 and the pH≤ 4.5, the CODcr decreased to below 50 mg·L-1, up to the standards for reuse water.(为提升纳米零价铁在类芬顿反应体系中的催化能力，减少团聚现象，采用液相还原法制备了生物炭负载纳米零价铁材料（nZVI@BC）。通过表征、亚甲基蓝降解实验，探究材料性能、降解最佳条件及作用机理。结果表明，纳米零价铁（nZVI)均匀分布于生物炭表面，且材料纯度较高、稳定性较好。在降解实验中，降解100 mg·L-1亚甲基蓝溶液的最佳反应条件为25 ℃、初始pH=3、nZVI@BC投加量30 mg·L-1、H2O2投加浓度4 mmol·L-1，10 min内几乎完全降解。在降解过程中，·OH起主要作用，发色官能团首先断裂，随后芳环结构被破坏，最终彻底降解。且nZVI@BC循环使用性能较好，3次循环后亚甲基蓝去除率仍达85%以上。在印染废水处理实验中，nZVI@BC处理效果良好，当H2O2投加浓度为0.9 mmol·L-1、nZVI@BC投加量为60 mg·L-1、pH≤4.5时，出水化学需氧量（CODcr）可降至50 mg·L-1以下，达到回用水标准。)