【作者】 杨洁；

【导师】 徐炎华；

【作者基本信息】 南京工业大学 ， 生物化工， 2004， 硕士

【摘要】 砷(As)是一种对人体及其它生物体有毒害作用的致癌物质。由于自然释放和人为的大量开采、生产和使用,砷污染的现象愈来愈严重,含砷废水的治理刻不容缓。水体中的砷,通常以无机态存在,有三价砷 As(Ⅲ)和五价砷 As(Ⅴ)两种化学价态。As(Ⅲ)的毒性是 As(Ⅴ)的六十多倍。絮凝、沉淀、吸附等常用方法能有效脱除As(Ⅴ),但对As(Ⅲ)的处理却收效甚微。因此,将As(Ⅲ)氧化为As(Ⅴ)既能提高脱除砷的效果,又有利于降低含砷废水的毒性。基于用添加化学氧化剂方法在成本及二次污染方面的问题,以及砷的生物毒理学特性(有机砷的毒性小于无机砷)的考虑,本论文选用生物氧化法和 TiO2光催化法对 As(Ⅲ)氧化进行了探讨。准确测定总砷和三价砷浓度的检测方法的建立,是深入开展本课题研究工作的重要基础。作者利用流动注射氢化物发生器与原子吸收光谱仪联用技术,建立了在不同酸度条件下分别检测总砷和三价砷浓度的方法。该方法对 As(Ⅲ)浓度测定的相对标准偏差为 5.2%,加标回收率在 89.4～105.6%之间;对总砷浓度测定的相对标准偏差为 2.0%,回收率在 96～100%之间。本论文从活性污泥中筛选了四株具有 As(Ⅲ)氧化能力的菌株,并对生物氧化脱除 As(Ⅲ)进行了初步的研究。筛得的菌株对五价砷的耐受性高于三价砷,菌株对 As(Ⅲ)的耐受浓度达到 500mg/L,对五价砷的耐受浓度达到 1500mg/L。利用筛得的菌氧化 As(Ⅲ),菌株对温度的适应范围较宽,在 20-30℃均有较好的脱除效果。菌株在 pH 值为 6.0 的情况下,其氧化酶的活性较高,氧化率为 30.2%。本文还探讨了 TiO2光催化氧化三价砷的技术,考察了以汞灯为光源时,TiO2投加量、As(Ⅲ)初始浓度、光照强度、体系初始 pH 值以及氧化剂加入量等因素对 TiO2光催化氧化三价砷效果的影响。得到在 500W 汞灯照射下,对 As(Ⅲ)初始浓度为 10 mg /L,TiO2投加量为 1g/L,H2O2浓度 0.03% , pH 为 8 的反应体系进行光催化反应 6 小时后,检测得 As(Ⅲ)氧化率为 66.1%。在实验基础上本论文对 TiO2 光催化氧化 As(Ⅲ)的机理进行了初步探索。在以汞灯为光源的研究基础上,本文还考察了自然光照下 TiO2参与的 As(Ⅲ)光催化氧化效果。反应 8 小时 I<WP=5>后测得 As(Ⅲ)氧化率为 40.7%。更多还原

【Abstract】 Arsenic is a carcinogen and toxic to man and other living organisms, whichwidely distributed in water, soils and anthropogenic sources. The contamination ofdrinking-water supplies with inorganic arsenic is commonly reported and has beenidentified as a major risk for human health. Arsenic is present in natural water in twooxidation states, +3(As(Ⅲ)) and +5(As(Ⅴ)), which are charaterised by differentchemical behaviour, bioavailability, and toxicity. As(Ⅲ) is much more toxic thanAs(Ⅴ). Various treating methods such as ion exchange, adsorption and coagulationhave been proved to be feasible to As(Ⅴ) but ineffective to the removal of As(Ⅲ).Therefore, oxidation of As(Ⅲ) to As(Ⅴ) could not only enhance As(Ⅲ) removal butalso reduce its toxicity. This paper investigated two methods for oxidation of As(Ⅲ)including bio-oxidation and TiO2 photo-oxidation.Hydride generation-atomic absorption spectrometer is used in this study toquantify total arsenic and arsenite respectively at different pH conditions. The optimaloperation conditions were studied and established. The relative standard deviationsare 5.2% and 2.0%, while the reclaim rates are 89.4～105.6% and 96～100% forAs(Ⅲ) and total arsenic, respectively.Four strains were isolated from active sludge which could catalyze arsenicoxidation. The tolerance of strains to As(Ⅴ) is higher than that of As(Ⅲ). They cangrow in 1500 arsenate-contained or 500 mg/L arsenite-contained medium. Theoxidation of As(Ⅲ) by the stains can effectively conduct at 20~30℃ and 30.2%oxidation rate is reached at pH 6.Photocatalytic oxidation of arsenite by use of TiO2 was studied. The effect ofsome important parameters was investigated. A quite high oxidation rate 66.1% wasobtained under the conditions of 500W Hg lamp irradiation, 6 hours, TiO2 dosage1g/L,addition of 0.03% H2O2 , pH 8. A tentative study on photocatalytic oxidation ofarsenite mechanism was conducted. Furthermore, 40.7% photocatalytic oxidation rate i<WP=7>of arsenite using TiO2 was observed under the irradiation of sunlight.更多还原