【作者】 丁春生；

【导师】 宁平；

【作者基本信息】 昆明理工大学 ， 环境工程， 2012， 博士

【摘要】 饮用水安全问题是人类最关注的问题之一,饮用水消毒副产物具有致癌作用、细胞遗传毒性和致突变性,对人们的身体健康产生极大的危害,因此对饮用水消毒副产物的研究具有重要的现实意义。本论文采用气相色谱/质谱法,选择甲基叔丁基醚为萃取剂,1,2.二溴丙烷为内标物,建立了含氮消毒副产物三氯硝基甲烷(TCNM)的测定方法。以甲胺为前体物,考察了消毒副产物TCNM的生成过程及影响因素。以三氯硝基甲烷为研究对象,分别采用活性炭吸附、铁还原和高级氧化技术,系统研究了TCNM的控制技术,分析了其降解机理及动力学规律。根据加标回收率和精密度试验结果,本研究建立的三氯硝基甲烷的测定方法,具有较高的准确度,其回收率为97.3%.106%,相对标准偏差为1.43%-2.25%,最小检测限(MDL)小于1μg/L。以甲胺为前体物,考察了消毒副产物TCNM的生成过程、影响因素。结果表明：pH在碱性条件下TCNM的生成量比中性和酸性条件下高,TCNM的生成量随着pH的增大而逐渐提高。在投氯量2-8mmol/L的范围内,TCNM的生成量随着投氯量的增加而提高,当投氯量由8mmol/L增加到12mmol/L时,因自由氯的浓度较高,甲胺还通过其它路径发生反应生成了腈类和醛类,从而使TCNM的生成量降低。在10.30℃范围内,温度对甲胺生成TCNM的影响较明显,温度越高,TCNM的生成量越高。甲胺氯化形成TCNM的过程符合亲电反应的机理,HCl0和C10-可以作为亲电试剂进攻甲胺最终形成TCNM。为了提高活性炭对TCNM的去除效率,采用NaOH (30%, w/v)对颗粒活性炭进行改性,以提高其吸附容量。分别采用比表面孔径分布测定仪、扫描电镜、傅立叶红外变换光谱等先进仪器及Boehm官能团滴定法,对改性前后活性炭的表面理化性质进行表征。结果表明：NaOH-GAC的比表面积比GAC增加了9.47%,NaOH-GAC的表面的酸性基团(羧基、内酯基、酚羟基)比GAC减少了29.6%,改性活性炭对三氯硝基甲烷的吸附容量大大增加。吸附试验结果表明：对于浓度为10μg/L的三氯硝基甲烷溶液,吸附剂投加量为0.3g/L时,NaOH-GAC的吸附去除率为87%,是GAC的1.71倍。吸附剂对三氯硝基甲烷的吸附过程大致分3个阶段：快速阶段、慢速阶段和动态平衡阶段。GAC吸附三氯硝基甲烷溶液的吸附平衡时间为36h,30%NaOH-GAC吸附三氯硝基甲烷溶液的吸附平衡时间为6h。铁刨花对低浓度的三氯硝基甲烷有较好的去除效果,对于100ml浓度为5μtg/L的三氯硝基甲烷溶液,当铁刨花的投加量为4g时,反应180min后,去除率达到90.15%。铁刨花投加量对三氯硝基甲烷的去除效果影响较大,随着铁刨花投加量的增加,三氯硝基甲烷的去除率增加。在低浓度三氯硝基甲烷浓度条件下,三氯硝基甲烷初始浓度的变化对去除三氯硝基甲烷的去除效果影响不大。铁刨花还原去除三氯硝基甲烷的反应符合一级反应动力学规律。当三氯硝基甲烷初始浓度为20μg/L时,反应150min后,单独H202降解时,随着反应时间和H2O2投加量的增加,三氯硝基甲烷去除率逐渐提高,H2O2投加量为15mg/L,去除率达到39.54%；单独03降解三氯硝基甲烷,随着臭氧的投加浓度增加,三氯硝基甲烷去除率提高,臭氧浓度控制为10.06mg/L,去除率为35.30%；单独UV降解,随着紫外光强的增加,紫外光对三氯硝基甲烷的去除率明显提高,紫外光强为31μw/cm2时,去除率为43.53%。联合工艺对三氯硝基甲烷有更好的去除效果。在UV-H2O2工艺中,控制紫外光强为31μw/cm2,当H202投加量在15-45mg/L范围内时,随着H202投加量的增加,三氯硝基甲烷去除率有较为明显的提高。当H202投加量从15mg/L增加到45mg/L时,初始浓度为20μg/L的三氯硝基甲烷在反应150min后,去除率从82.26%提高到95.61%。而且随着紫外光强的增加,UV-H2O2联合工艺对三氯硝基甲烷的去除率,也有较为明显的提高。在UV-H2O2-O3联合工艺中,在紫外光强为31μw/cm2,H202投加量为15mg/L,臭氧投加量为10.06mg/L的条件下,初始浓度为20μg/L的三氯硝基甲烷在反应150min后,去除率达到了97.28%的最高值。UV-H2O2-O3联合工艺降解三氯硝基甲烷符合一级反应动力学。更多还原

【Abstract】 The safety of drinking water has become one of the most serious concerns and it is well known that the disinfection by-products in drinking water cause great harm to human health due to the carcinogenesis, genetic toxicity and mutagenicity. Therefore, it is of great practical significance to probe and research on the disinfection by-products in drinking water.In this study, the quantitative analysis of trichloronitromethane (TCNM), one kind of nitrogen disinfection by-product in drinking water by gas chromatography/mass spectrometry (GC/MS) on the extracting agent of methyl tertiary butyl ether (MTBE) and using1,2-dibromopropane as internal standard, was introduced. Based on this analytical method, the formation process of TCNM and its influencing factors were evaluated with methylamine as the precursor. In addition, the technologies, such as activated carbon adsorption, iron reduction and advanced oxidation technologies were applies to control the TCNM, and then its degradation mechanism and dynamic behaviors were also discussed.According to the spiked recovery and accuracy, the measurement method for TCNM was highly accurate and the recovery rate was between97.3%and106%with relative standard deviation of1.43%-2.25%and limit of detection less than1μg/L.It was indicated from the formation process of TCNM that the TCNM amount produced under alkali condition was higher than those produced under the neutral and acid conditions, and the TCNM amount increased with the increase of pH value. It was also found that the TCNM amount increased with the increase of chlorine addition when the chlorine dosage was in the range of2-8mmol/L. However, TCNM amount reduced when the chlorine dosage was enhanced from8mmol/L to12mmol/L, in which the concentration of free chlorine was higher and methylamine turned into nitriles and aldehydes through other reactions. Temperature is another important factor to affect the TCNM formation from methylamine especially in the range of10-30℃and the higher temperature was, the more TCNM amount was produced. The formation process of TCNM from methylamine by chlorination corresponded with the mechanism of electrophilic reaction, in which HClO and ClO-could be used as electrophilic reagent to attack methylamine and then to form TCNM. In order to enhance the removal efficiency of TCNM by activated carbon, the modification of granule activated carbon by sodium hydroxide was applied with the higher adsorption capacity. The surface physical and chemical properties of activated carbon before and after modification were investigated separately by surface porosity detector, scanning electron microscope (SEM), fourier transform infrared spectrometry (FTIR) and Boehm functional group titration method. The results showed that the specific surface area of NaOH(30%, w/v)-GAC increased by9.47%compared to that of GAC, while the acidic groups (mainly carboxyl group, lactone group and phenolic hydroxyl group) on the surface of NaOH-GAC reduced by29.6%, which revealed that the adsorption capacity of TCNM by modified GAC was enhanced greatly.The results of adsorption tests also showed that when the initial concentration of TCNM solution was10μ/L,87%removal was achieved using NaOH-GAC with the addition of0.3g/L, which was1.71times higher than that by GAC. The adsorption process of TCNM by the modified GAC could be divided into three phases, which are rapid phase, slow phase and dynamic equilibrium phase. The time of equilibrium adsorption of TCNM by GAC was36h, while the time by NaOH (30%, w/v)-GAC was reduced to6h.Meanwhile, the addition of iron scraps enhanced the removal efficiency of TCNM in low concentration, and when the initial concentration of TCNM was5μg/L, TCNM removal was90.15%with the addition and reaction time of40g/L and180min, respectively. The concentration of iron scraps was of great impact on TCNM removal and the removal increased with the increase of iron scraps addition. However, TCNM removal did not change a lot with the variation of initial concentration of TCNM when it was in a low level. The TCNM reduction by iron scraps followed the first-order kinetic model.In the experiments of advanced oxidation processes, when the initial TCNM concentration of was20μg/L, after150min, we found that TCNM removal was enhanced by using hydrogen peroxide (H2O2) and it increased with the increase of reaction time and H2O2addition; the removal was39.54%when H2O2concentration were15mg/L; ozone (O3) has a great effect on TCNM removal and the removal was obviously improved with the increased ozone concentration, the removal reached35.30%when the ozone concentration were10.06mg/L, the application of UV light was also helpful to increase TCNM removal, the removal were43.53%when the UV light intensity were31μw/cm2. Furthermore, the research on TCNM removal by the UV-H2O2process and UV-H2O2-O3process was conducted, which performed better with higher TCNM removal than the individual process shown above. In the UV-H2O2process, when the UV light intensity was set at31μw/cm2, after reaction time of150min, removal of TCNM with the initial concentration of20ug/L was improved from82.26%to95.61%with the increase of H2O2addition from15mg/L to45mg/L. The enhancement of UV light intensity also contributed to the TCNM removal. In the UV-H2O2-O3process, the highest TCNM removal of97.28%with the initial TCNM concentration of20μg/L was obtained when the UV light intensity, H2O2addition and O3addition were only31μw/cm2,15mg/L and10.06mg/L, respectively due to the more hydroxyl radical generated in this process. The TCNM degradation by UV-H2O2-O3process accorded with the first-order kinetics model.更多还原