砷是一種劇毒元素,長期接觸無機(jī)砷會(huì)導(dǎo)致癌癥等嚴(yán)重疾病。砷天然存在于賤金屬和貴金屬礦物中,并且經(jīng)常出現(xiàn)在固體或液體冶金工業(yè)廢物中。由于砷的提取缺乏經(jīng)濟(jì)效益,將其轉(zhuǎn)化為體量較小且性質(zhì)穩(wěn)定的固體廢棄物進(jìn)行填埋被認(rèn)為是一個(gè)比較理想的處理方式。只有當(dāng)砷以五價(jià),砷才能被最有效地去除并形成穩(wěn)定產(chǎn)物。因此需要將砷（Ⅲ）氧化成砷（V）。由于鐵對(duì)砷有很高的親和力,所以通常用于除砷和固定。但在大多數(shù)情況下,砷鐵共沉淀與石灰中和同時(shí)發(fā)生,形成的無定形氫氧化物污泥體積大、含水量高,不適于填埋。本博士研究的總體目標(biāo)是設(shè)計(jì)一種去除和固定砷的工藝,形成一種容易處理的晶體沉淀產(chǎn)物。此方法包括在酸性溶液中使用臭氧將三價(jià)砷氧化為五價(jià)砷和一個(gè)兩段提升pH形成沉淀的過程。首先是在0.5-2的pH范圍內(nèi),用臭氧將三價(jià)砷氧化成五價(jià)砷。間歇實(shí)驗(yàn)結(jié)果表明,在酸性溶液中,臭氧氧化可使三價(jià)砷迅速轉(zhuǎn)化為五價(jià)砷。在pH為0.5和20° C條件下,溶液中的三價(jià)砷濃度在120分鐘內(nèi)從5000 mg/L降至0.1 mg/L以下。研究發(fā)現(xiàn),臭氧活性在高溫下被抑制,但會(huì)被Fe3+催化。在90℃時(shí),在沒有Fe3+的情況下,幾乎沒有三價(jià)砷As被氧化成五價(jià)。... 

【文章來源】：中國科學(xué)院大學(xué)(中國科學(xué)院過程工程研究所)北京市

【文章頁數(shù)】：130 頁

【學(xué)位級(jí)別】：博士

【文章目錄】：
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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