【作者】 张洁；

【导师】 张增强；

【作者基本信息】 西北农林科技大学 ， 环境工程， 2013， 硕士

【摘要】 砷及含砷化合物都有较大毒性，且均具有致癌作用。自然界中的砷多数与有色金属伴生，在有色金属的提取过程中，砷以硫化物或盐的状态不同程度地进入烟气、废水和废渣中，其中，大部分砷以含砷废渣方式堆存，成为我国最主要的含砷废物。国内对于污泥、焚烧飞灰等的烧结技术处理处置研究较多，但对含砷废渣烧结方面的研究相对欠缺。本文研究添加SiO₂、Al₂O₃、MgO和CaO的含砷废渣在高温烧结过程中砷的环境释放行为，为含砷废渣的高温处理提供参考。试验中，称取一定量含砷废渣，分别加入质量分数30%的SiO₂、Al₂O₃、MgO和CaO，采用翻滚振荡仪使物料完全混合，将混合物料在10MPa下加压成型，于400¹100℃烧结1h，冷却后取烧结体，研究烧结体中砷的固化特性和浸出特性，并采用X射线衍射（XRD）和扫描电子显微镜（SEM）方法分析高温烧结体中砷的矿物赋存形态和烧结体的微观形貌，探讨添加剂对含砷废渣烧结体中砷的固定、浸出及烧结体的矿物相和形貌的影响。得出下列结论：1300℃烧结处理后，经三种浸出方法，含砷废渣中砷的浸出质量浓度均显著下降。通过对比原样和1300℃的烧结体的微观形貌，发现1300℃时，烧结体中晶粒更加致密化，形成砷酸钙结晶体。烧结体中的砷被固定在稳定的砷酸钙结晶体中，有效降低了砷的浸出。SiO₂对砷的固化作用不明显，1300℃烧结处理时，SiO₂对砷的浸出抑制作用最强。可能在1300℃时，烧结体中发生熔融包裹现象，生成了具有网络结构的硅酸盐晶体，砷被包裹在玻璃质硅酸盐晶格当中，从而导致砷的浸出质量浓度显著降低。Al₂O₃对砷的固定和浸出没有显著的抑制作用。CaO对含砷废渣烧结体中砷的挥发和浸出有极大的抑制作用，1000℃高温烧结条件下，砷的固化率达最大值95.14%，CaO对含砷废渣中砷的挥发抑制作用最强。可能的原因是砷以砷酸钙（Ca₃（AsO₄）₂）的形式被固定在稳定结晶相中而导致砷的固化率显著提高。经水平振荡法、硫酸硝酸法和TCLP法三种浸出方法处理后，在400¹000℃，添加CaO的烧结体中砷的浸出质量浓度均远远小于原样，在1000℃时，砷的浸出量均达到最小值，分别为1.33μg/L，0.13mg/L和0.85μg/L，表明烧结温度为1000℃时，CaO对砷的浸出抑制作用最强。1100℃以上，砷的浸出量明显增长，用热力学角度分析：在1100℃以上，As₂O₃生成As₂O₅的反应其吉布斯自由能大于0，反应不能够自发进行，则导致As₂O₃→As₂O₅→Ca₃（AsO₄）₂这一系列反应不能完成。造成砷不能被稳定固化，致使砷的浸出量显著增加。通过X射线衍射图谱发现，1000℃时，添加CaO的含砷废渣烧结体中砷酸钙（CaAs₂O₆）衍射特征峰出现，可以说明砷被固化在稳定的砷酸钙中，因此CaO在此温度下对砷的挥发及浸出有最强的抑制能力。扫描电子显微镜图像显示添加CaO的含砷废渣原样与1100℃烧结体的微观形貌没有明显差异。MgO对砷的挥发有一定的抑制作用。400¹100℃内进行烧结处理，MgO对烧结体中砷浸出的抑制作用较大。X射线衍射图谱显示，1100℃时，砷以砷酸钙和砷酸镁的形式存在，砷酸钙和砷酸镁都为具有很小的溶解度的稳定矿物，砷被固化于稳定结晶相中，降低了砷的挥发和浸出。1300℃时，MgO对砷的浸出没有明显的抑制能力。最后研究了不同添加量的CaO的含砷废渣烧结体的性能，CaO作为含砷废渣添加剂，其质量分数在8¹0%时，其烧结之后的产物具备作为轻骨料建材产品使用的潜能。更多还原

【Abstract】 Arsenic and arsenic compounds had a greater toxicity and both had a carcinogeniceffect.The majority of arsenic were associated with non-ferrous metals in nature, state of thearsenic sulfide or salt got into the flue gas, waste water and sludge in the process ofnon-ferrous metal extraction, among them, most of the arsenic were stockpiling in the way ofarsenic-containing waste which had led to the most important arsenic-containing waste inChina. More research of the disposal of sludge, fly ash sintering technology in our nation, butrelative lack of the research of arsenic residue sintering. An experimental work was carriedout to investigate the effect of environmental release behavior of arsenic during sintering ofarsenic-containing waste with different additional contents like SiO₂, Al₂O₃, MgO and CaO,and provide reference for arsenic-containing waste in high temperature processing. The rawmaterials were certain amount of arsenic-containing waste added with the mass fraction of30%SiO₂, Al₂O₃, MgO, CaO, mixed the raw materials by flip vibration instrument, shapedunder the pressure of10MPa and exposed at400¹100℃for1h, made the sinteredproducts after cooling, studied the arsenic solidified characteristics and leachingcharacteristics, analysied mineral occurrence form and microstructures in high temperaturesintered products by XRD and SEM, discussed the effect of arsenic solidified characteristics,leaching characteristics, mineral occurrence form and microstructures in sintered products byadditional contents. Results showed that:The arsenic leaching mass concentration decreased greatly in arsenic-containing wasteafter three methods of leaching tests at1300℃. Compared the microstructures of the originalsample and sintered products at1300℃found that particle became more densification insintered products and created the crystalline arsenate calcium. The arsenic was fixed in thestable crystalline arsenate calcium, which decreased the arsenic leaching characteristics.The fixed effects of arsenic by SiO₂was not obvious. SiO₂had the most inhibitory effectof arsenic leaching at1300℃, maybe because the melt inclusions phenomenon in thesintering body would occur and grew to the silicate crystals which had the grid structure, soarsenic was wrapped in the glassy silicate lattice which led to the lower arsenic leaching ratesignificantly.The inhibitory effect of arsenic solidified and leaching characteristics by Al₂O₃was not obvious.CaO had great inhibitory effect of arsenic solidified and leaching characteristics insintered products. The maximum arsenic curing rate was95.14%at1000℃, CaO had thestrongest inhibitory effect of arsenic evaporation characteristics. The possible reason was thatarsenic was wrapped in the crystalline arsenate calcium which enhanced the curing rate ofarsenic greatly.By horizontal vibration method, sulphuric acid&nitric acid method and TCLP method,the arsenic leaching mass concentration in sintered products added with CaO was far less thanthe original sample in400to1000℃, arsenic leaching mass concentration reached aminimum of1.33μg/L,0.13mg/L and0.85μg/L at1000℃, which indicated that CaOhad the strongest inhibitory effect of arsenic leaching characteristics.The arsenic leaching mass concentration had the significant growth above1100℃,thermodynamics analysis was: the gibbs free energy of the reaction by As₂O₃generated toAs₂O₅was greater than0, therefore the reaction can`t occur spontaneously which led to thereaction by As<sub>2</sub>O<sub>3</sub>→As<sub>2</sub>O<sub>5</sub>→Ca<sub>3</sub>（AsO<sub>4</sub>）<sub>2</sub>can`t complete. Thus, arsenic can`t be stable curingwhich led to a significant increase in the amount of arsenic leaching.X-ray diffraction patterns found that, the diffraction peaks of the calcium arsenate insintered products added with CaO appeared at1000℃, which indicated that arsenic was curedin a stable calcium arsenate so CaO had the strongest ability to inhibit the arsenicvolatilization and leaching.The scanning electron microscope image showed that there was no significant differencein morphology between the original sample added with CaO and sintered products at1100℃.MgO had a certain inhibitory effect to arsenic volatilization. MgO had greater inhibitoryeffect to arsenic leaching in400to1000℃. X-ray diffraction patterns illustrated that, arsenicwas existed in the form of calcium arsenate and magnesium arsenate at1100℃, calciumarsenate and magnesium arsenate were stable minerals which had small solubility. In this case,arsenic was cured in a stable crystalline phase which reduced the arsenic volatilization andleaching. The inhibitory effect of arsenic leaching characteristics by MgO was not obvious at1300℃.At last, this paper studied performance of arsenic-containing waste sintered productsadded with CaO in different added amount. CaO as an arsenic-containing waste additive,when the mass fraction was8%to10%, the sintered products had the potential for the use as alightweight aggregate building materials.更多还原