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含铬、砷重金属危废的无毒化处理与资源回收研究
Alternative TitleStudy on Harmless Treatment and Resource Recovery of Chromium or Arsenic-containing Residue
张伟芳
Subtype博士
Thesis Advisor张静
2019-12
Degree Grantor中国科学院生态环境研究中心
Place of Conferral北京
Degree Name工学博士
Degree Discipline环境工程
Keyword铬渣 硫化砷渣 铬和砷复合废水 水热 处理 光催化 chromite Ore ProcessIng Residue, Arsenic Sulfide Residue, Co Exist Ing Chromium ( And Arsenic (As) wAstewater h Ydrothermal Treatment p Hotocatalysis
Abstract

      铬(Cr )和砷 As )作为常见的重金属污染物,主要来源于采矿和冶炼等工业产生的废渣 和 废水。含铬、砷等工业废水经过处理,也可能形成和转化成含铬、砷的固废。典型的铬盐生产和使用行业产生的铬渣由于固相多、组分复杂,高 毒性的 六价铬( Cr(VI) VI))与 废渣 组分形成固溶体或者包覆在废渣物相的晶格中,传统的提取方法往往不能有效的提取包覆的 Cr(VI) VI),高效提取 Cr(VI)是彻底解毒铬渣的难题之一。另外,硫化法处理酸性污水产生的大量硫化砷渣,由于颗粒小,含水率高, 给 堆存和处理带来极大的挑战。 因此,未妥善处理的废渣,释放 高迁移性的 Cr(VI) 和剧毒的 As(III) 进入自然环境 对水环境、土壤等造成严重的危害,威胁人体健康。本文采用水热法分别对铬渣和硫化砷渣进行脱毒处理,探究废渣在水热处理过程中的物相转变和转化固定的机制,实现废渣的无害化和资源回收。在此基础上,固废处理可能会产生低浓度重金属废水,需进行深度处理,以 Cr(VI) 和 As(III) 共存的复合 废水为例,采用光催化技术,海藻酸铁 为光催化剂,将 Cr(VI) 和 As(III) 转化为毒性较低的易沉淀和吸附
去除的 Cr(III) 和 As(V) 最终 实现 Cr 和 As 的去除。
主要研究结果及结论如下:
      (1) 硅酸钠 协助 水热 处理( HT Na 2 SiO 3 )铬渣,提取铬渣中的 Cr(VI)采用水热法对铬渣进行脱毒,实现Cr(VI) 的高效提取。实验 结果表明, 在水热过程中,添加 Na 2 SiO 3 可以显著促进 铬渣 中 Cr(VI) 的提取效果。通过毒性浸出法 TCLP 进行评价 ,经 HT Na 2 SiO 3 法处理后 的 废渣样品 浸出液中 Cr(VI)浓度明显降低至 1.1 mg L 1 低于 1.5 mg L 1 的 排放 限值 GB 16889 2008 EPA中国 。 XPS 和 EDS 分析 证实,经处理后的 废 渣 表面未检测到 Cr(VI) 和 Cr(III) 。进一步 分析铬渣中的物相组成,进行固相模拟实验,得出 HT Na 2 SiO 3 法处理铬渣的主要反应机理为: 在水热条件下 SiO 32 离子不仅 可以 作为阴离子交换剂对铬渣中的层状水滑石进行 分 层 释放层间 的 Cr ( 。 而且 ,作为碱性试剂 有助于 三氧化二铬氧化, 释放 可溶性 Cr ( 。层间的 Cr ( 的释放和 Cr(III) 的氧化, 均 提高铬渣中 Cr 的 提取效果 。本 研究 为铬渣的解毒和 Cr(VI) 的回收提供 方法和策略。
      (2) 硝酸铁协助 水热 处理 HT Fe(NO 3 3 )硫化砷渣,转化和固定硫化砷渣采用水热法,实现硫化砷渣一步转化和固定,形成稳定的臭葱石和回收硫磺。实验结果表明在 pH 1.0 、硝酸铁用量为 10 mmol g 1 (硫化砷渣)、 150水热 20 h ,硫化砷被溶解、氧化和固定,形成粒径约为 15 μ m 的臭葱石晶体,固砷率达到 99% 以上。 在臭葱石的水热生长过程中,早期为无定形 的砷酸铁,
可能 由于硫化砷中的硫 溶解 和 氧化 的影响 ,使得无定型的砷酸铁纳米颗粒 结晶形成 片层 结构 后不会进一步生长,而是通过片层结构定向组装过程形成 介晶,随着水热的进行, 最终 生长成表面为多面体椎状的 大颗粒 臭葱石。 本方法 生成的臭葱石 颗粒大 ,稳定性好 ,浸出达标 。同时,生成的单质硫可以进一步 分离回收。 本研究为硫化砷渣的固定稳定化提供一种简单高效的方法和策略。
      (3 )海藻酸铁小球的光催化处理 Cr(VI)/As(III) 废水的机理研究
在酸性废水中常含有共存 多金属离子的 Cr(VI) 和 As(III) III),使废水处理变得困难。因此,在光照下,采用三价铁离子 Fe ( 和海藻酸交联形成的海藻酸铁小球( Fe SA )可以有效实现 Cr(VI) 和 As(III) 的同时转化和去除。实验结果表明,在 pH = 3.0 ,光照 150 min ,不仅可以促进 5 mg L 1 的 Cr(VI) 和 5 mg L 1的 As(III) 完全的还原和氧化。而且,在较宽的 pH 范围( 3 7 ),反应生成的产物Cr(III) 和 As(V) 能被有效的去除,去除率高达 80% 以上。主要反应机理为:在光照激发下, Fe SA 小球发生金属与配体的电子转移( LMCT ),从而 生成 碳中心自由基 CO 2 --)和二价铁离子 Fe(II) Cr(VI) 主要被 Fe(II) 还原。然而, CO 2在 O 2 和 Fe (II 的参与下,发生一系列的自由基反应,生成活性氧物种。其中,证实 自由基反应的存在。最后, Fe SA 小球被多次重复利用处理 Cr(VI) 和 As(III)表现 高效的可利用性, 并 在实际水体中也展现良好的性能。

Other Abstract

      As common heavy metal pollutants, chromium (Cr) and arsenic (As) mainly come from the industrial waste residues and wastewater from mining and smelting industries. Industrial wastewater containing Cr and As may also be transferred into solid wastes after treatment. Cr waste residue (COPR) derived from production and use of chromate consists of many complex solid pha ses. The highly toxic hexavalent chromium (Cr (VI)) often forms solid solution with components and is encapsulated in the lattice of the phase of residue. In addition, the large amount of arsenic sulfide residue, produced in the treatment of acid sewage by sulfurization method, brings great challenges to storage and treatment because of its small particles and high water content. Therefore, t he highly mobile Cr (VI) and highly toxic As (III) from waste residues without appropriate treatment cause serious ha rm to water environment and soil, and finally threaten human health. In this paper, COPR and arsenic sulfide residue were treated by hydrothermal method respectively to realize the non toxic discharge of residue and resources recovery, and the mechanisms o f
the phase transformation in COPR and the phase transformation and fixation in arsenic sulfide residue were explore respectively in the proc ess of hydrothermal treatment. On this basis, low concentration heavy metal wastewater from waste residue treatment needs to be further treated. Taking the composite wastewater containing Cr(VI) and As(III) as the example, the photocatalytic technology by ferric alginate (Fe SA) as photocatalyst was used to convert Cr(VI) and As(III) into Cr(III) and As(V) with lower t oxicity, which are easy to precipitate and adsorb, and can realize the u ltimate removal of Cr and As.
The main findings and conclusions are as follows:
      (1) Extraction of Cr(VI) from COPR by hydrothermal treatment assisted with sodium silicate (HT Na 2 SiO 3
      In order to achieve highly efficient extraction of Cr(VI), HT Na 2 SiO 3 method was used to detoxify COPR, and the results reveal that Na 2 SiO 3 greatly promotes the extraction of Cr(VI) in COPR. After the treatment, the Cr(VI) concentration in the leachate by toxicity characteristic leaching procedure (TCLP) markedly decreased to 1.1 mg L 1 , well below the regulatory limit of 1.5 mg L 1 (GB 16889 2008, China EPA). X ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) mapping confirm t hat neither Cr(VI) nor Cr(III) were detected on the surface of COPR after treatment. The main mechanism of extracting Cr(VI) from COPR by HT Na 2 SiO 3 method was obtained, through the analysis of phase composition in COPR and further the results of the solid phase simulation experiments. In the hydrothermal conditions, SiO 32 ions not only act as the anion exchange agent to delaminate layered phases in COPR like hydrotalcites to release the encapsulated Cr(VI), but also as an alkaline reagent to help the oxidation of Cr(III) in COPR to soluble Cr(VI) both of which distinctively increased the leaching of chromium from COPR. This study provides a novel st rategy for both COPR detoxification and recovery of Cr(VI) for resource recycling.
      (2) Conversion and stabilization of arsenic sulfide residue by hydrothermal treatment assisted with ferric nitrate (HT-Fe(NO3)3)By HT-Fe(NO3)3 method, arsenic sulfide resid ue can be transformed and stabilized in one step to form stable scorodite and recover sulfur. The results show that under the conditions of pH 1.0, Fe(NO3)3 dosage of 10 mmol g 1 (arsenic sulfide residue) and 150 o C , arsenic sulfide is dissolved, oxidized and stabilized by HT Fe(NO3)3 for 20 h. The arsenic capturing rate reaches over 99% because of the formation of the scorodite with a ~15 µm particle size. During the process of hydro thermal growth , the amorphous iron arsenate was formed in the early stage . It is possible that due to the dissolution and oxidation of sulfur in arsenic sulfide,amorphous iron arsenate nanoparticles would not grow further after crystallizing into lamellar structure, but form mesocrystals through the directional assembly proces s of lamellar structure and then grow into spherical large particles with polyhedral surface. S corodite with large particle size has a good stability and t he As concentration in the leachate from scorodite by TCLP is well below the regulatory limit and the produced elemental sulfur can be recycled. This study pr ovides a
simple and efficient strategy for the stabilization of arsenic sulfide residue.
      (3) Study on the mechanism of photocatalytic redox and removal of Cr(VI)/As(III)wastewater by Fe SA Multiple heavy metal ions (e.g. Cr(VI) and As(III)) normally co exist in acid wastewater, making the wastewater treatment complicated. Herein, the synergistic redox conversion and removal of Cr(VI)/As(III) were effectively achieved by applying iron(III) cr oss linking alginate hydrogel beads (Fe SA) as photocatalyst under simulated sunlight. Results show that not only the complete redox conversion of 5 mg L 1 Cr(VI) and 5 mg L 1 As(III) was obtained in 150 min at pH 3.0 3.0, but also the removal efficiency of th e transformed products (Cr(III) and As(V)) was greatly enhanced to above 80% in a wide pH range of 3 7. The ∙CO 2 rradicals, produced by the ligand to metal charge transfer (LMCT) excitations on Fe-SA, together with the phtocatalysis generated Fe(II), was r esponsible for the Cr(VI) reduction. Meanwhile, a series of free radical reactions occur to form reactive oxygen species with the participation of O 2 and Fe (II) and CO 2 rradicals. Finally, OH mainly contributed to the As(III) oxidationoxidation, as confirmed by electron paramagnetic resonance (EPREPR) and the by-product of CO 22. Moreover, Fe-SA composite presented excellent reusability and performance in treatment of Cr(VI)/As(III) in real waters.

Pages160
Language中文
Document Type学位论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/42352
Collection环境纳米技术与健康效应重点实验室
Recommended Citation
GB/T 7714
张伟芳. 含铬、砷重金属危废的无毒化处理与资源回收研究[D]. 北京. 中国科学院生态环境研究中心,2019.
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