臭氧氧化结合三价铁沉淀法除砷新技术研究

发布时间：2021-08-31 16:43

　　砷是一种剧毒元素,长期接触无机砷会导致癌症等严重疾病。砷天然存在于贱金属和贵金属矿物中,并且经常出现在固体或液体冶金工业废物中。由于砷的提取缺乏经济效益,将其转化为体量较小且性质稳定的固体废弃物进行填埋被认为是一个比较理想的处理方式。只有当砷以五价,砷才能被最有效地去除并形成稳定产物。因此需要将砷（Ⅲ）氧化成砷（V）。由于铁对砷有很高的亲和力,所以通常用于除砷和固定。但在大多数情况下,砷铁共沉淀与石灰中和同时发生,形成的无定形氢氧化物污泥体积大、含水量高,不适于填埋。本博士研究的总体目标是设计一种去除和固定砷的工艺,形成一种容易处理的晶体沉淀产物。此方法包括在酸性溶液中使用臭氧将三价砷氧化为五价砷和一个两段提升pH形成沉淀的过程。首先是在0.5-2的pH范围内,用臭氧将三价砷氧化成五价砷。间歇实验结果表明,在酸性溶液中,臭氧氧化可使三价砷迅速转化为五价砷。在pH为0.5和20° C条件下,溶液中的三价砷浓度在120分钟内从5000 mg/L降至0.1 mg/L以下。研究发现,臭氧活性在高温下被抑制,但会被Fe3+催化。在90℃时,在没有Fe3+的情况下,几乎没有三价砷As被氧化成五价。... 

【文章来源】：中国科学院大学(中国科学院过程工程研究所)北京市

【文章页数】：130 页

【学位级别】：博士

【文章目录】：
摘要
Abstract
Chapter 1 Introduction
    1.1 Arsenic element in Nature
        1.1.1 Arsenic emission
        1.1.2     Pyrometallurgical operation
        1.1.3     Hydrometallurgical operations
        1.1.4 Main arsenic species
        1.1.5 Arsenic toxicity
        1.1.6 Fixation of arsenic
        1.1.7 Arsenic removal processes with iron precipitation
        1.1.8 Arsenical ferrihydrite
    1.2 Oxidation from As (Ⅲ) to As (Ⅴ)
        1.2.1 Ozone oxidation
        1.2.2 Ozone reaction
        1.2.3 Effect of pH on ozonation
        1.2.4 Effect of temperature on ozonation
        1.2.5 Catalysts for decomposition of ozone
    1.3 Crystallization and precipitation
        1.3.1 Supersaturation
        1.3.2 Nucleation
        1.3.3 Crystal growth or secondary nucleation
        1.3.4 Two-step mechanism of nucleation of crystals in solution
        1.3.5 LaMer Mechanism
        1.3.6 Ostwald's rule of stages
    1.4 Research aim and objectives
Chapter 2 Arsenic (Ⅲ) Oxidation by Ozone and Ferric Ion
    2.1 Introduction
    2.2 Experimental
        2.2.1 Chemicals
        2.2.2 Oxidation of As (Ⅲ) by ozone
        2.2.3 Experimental procedure
        2.2.4 Separation of As (Ⅲ) and As (Ⅴ)
        2.2.5 Determination of arsenic concentration
        2.2.6 Precipitation process
    2.3 Results and Discussion
        2.3.1 Effect of reaction time
        2.3.2 Effect of temperature and Fe~(3+)
        2.3.3 Oxidation of As(Ⅲ) to As(Ⅴ) by air
        2.3.4 The temperature of 70 ℃ versus 90 ℃ for precipitation of ferric arsenate
    2.4 Summary
Chapter 3 Fixation of Arsenic by Complex Precipitate of Scorodite andFerrihydrite
    3.1 Introduction
    3.2 Experimental
        3.2.1 Materials
        3.2.2 Experimental apparatus
        3.2.3 Experimental procedure
        3.2.4 Leaching test
        3.2.5 Analysis
    3.3 Results and discussion
        3.3.1 Precipitation of ferric arsenate at pH 2
        3.3.2 Formation of crystalline scorodite in a two-stage precipitation (pH 2-3)
        3.3.3 Fixation of arsenic via improving pH of solution from 2 to 4
        3.3.4 Leaching test of produced solids
        3.3.5 Behavior of iron during precipitation process for arsenic removal
    3.4 Summary
Chapter 4 Two-Stage Precipitation/Coprecipitation Process for ArsenicRemoval
    4.1 Introduction
    4.2 Experimental
        4.2.1 Material
        4.2.2 Experimental procedure
    4.3 Result and discussion
        4.3.1 Two-stage precipitation of ferric arsenate in wastewater
        4.3.2 Precipitation of As from waste water by adding Fe~(2+) (Fe (Ⅱ)/As (Ⅴ)) withozone oxidation
    4.4 Summary
Chapter 5 Conclusions and Recommendations
    5.1 Overview
    5.2 Conclusions
        5.2.1 Arsenic (Ⅲ) oxidation by ozone and effect of ferric ion on ozonation
        5.2.2 Complex precipitate containing scorodite and ferrihydrite
        5.2.3 Two-stage precipitation/ coprecipitation process for arsenic removal
    5.3 Perspectives
References
Acknowledgement
Curriculum Vitae (With Publications)



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