The study on the dechlorination of OCDD with Pd/C catalyst in ethanol-water solution under mild conditions

Dechlorination of octachlorodibenzo-p-dioxin (OCDD) was carried out in ethanol-water (v/v=1:1) solution of NaOH in the presence of Pd/C catalysts with the use of H(2). The substrate was dechlorinated with Pd/C under mild conditions (atmospheric pressure and <100 degrees C) to give a chlorine-free product, dibenzo-p-dioxin (DD), in high yields. After reaction of 3h at 50 degrees C, 95.9% OCDD was degraded to low dechlorinated congeners and the yield of DD was 77.4%. We have also studied the dechlorination selectivity of chlorine atoms on the different substituted positions and postulated the dechlorination pathway of OCDD. For OCDD, the 2-position has higher reactivity than 1-position, but the difference is very small. From the distribution statistics of the intermediates during the reaction, we postulate that the steric effect plays an important role during the reaction and affect the dechlorination pathway of OCDD.     

Decomposition pathways and reaction intermediate formation of the purified, hydrolyzed azo reactive dye C.I. Reactive Red 120 during ozonation

In this study, an aqueous solution of purified, hydrolyzed C.I. Reactive Red 120 (RR 120, Color Index), was selected as a model to investigate the degradation pathways and to obtain additional information on the reaction intermediate formation. The dye was purified to avoid the influence of the impurities on the ozonation process and on the formation of oxidation by-products. To simulate the dye-bath effluents from dyeing processes with azo reactive dyes, a hydrolyzed form of the dye was chosen as a representative compound. High performance liquid chromatography/mass spectrometry and its tandem mass spectrometry was chosen to identify the decomposition pathways and reaction intermediate formation during the ozonation process. In addition total organic carbon and high performance ion chromatography analysis were employed to obtain further information on the reaction processes during ozonation. Purified, hydrolyzed RR 120 was decomposed under the direct nucleophilic attack by ozone resulting in oxidation and cleavage of azo group and aromatic ring, while the triazine group still remained in the solution even after prolonged oxidation time (120 min) due to its high resistance to ozonation. Phenol, 1,2-dihydroxysulfobezene, 1-hydroxysulfonbezene were detected as the degradation intermediates, which were further oxidized by O(3) and *OH to other open-ring products and then eventually led to simple oxalic and formic acid identified by HPIC.     

Determination of Nitrobenzene in Wastewater Using a Hanging Mercury Drop Electrode

The determination of trace amount nitrobenzene in wastewater on a hanging mercury drop electrode was studied. The determination conditions of pH, supporting electrolyte, accumulation potential, accumulation time, and voltammetric response were optimized. The sharp peak of the nitrobenzene was appeared at 0.05 V. The peak electric current was proportional to the concentration of nitrobenzene in the range of 1.47 × 10⁻⁵ ∼ 1.0 × 10⁻³ mol/l with relative standard deviations of 3.99 ∼ 8.94%. The detection limit of the nitrobenzene in water was 5 × 10⁻⁶ mol/l. The proposed method offered low limit of determination, easy operation, the use of simple instrumentation, high sensitivity and good reproducibility. It was applied to the determination of nitrobenzene in wastewater with an average recovery of 94.0% ∼ 105%. The proposed method provided fast, sensitive and sometimes real time detection of nitrobenzene.     

氟里昂12(CCl2F2)燃烧分解催化剂性能的研究

本文对贵金属、氧化物和复合氧化物体系催化剂上氟里昂_(12)(F_(12))燃烧分解反应进行了活性评价和稳定性研究.结果表明:TiO_2,ZrO_2/TiO_2催化剂对氟里昂_(12)燃烧分解反应具有良好的低温催化活性和较好的稳定性,ZrO_2/TiO_2催化剂具有一定的臭氧-催化氧化活性     

河流型饮用水水源保护区划分比较

比较分析了国内外河流型水源保护区划分的原则、方法和标准,例证了我国不同省份的划分实践。指出,我国各省多采用经验值划分水源保护区范围,部分省份划分方案久未更新,没有充分发挥保护区的作用。提出,应进一步细化水源保护区划分规范指导要求,及时修订省级水源保护区划分方案,并借鉴国外水源保护区划分经验,通过调整水质标准、重视公众参与、利用地理信息系统等方式划分水源保护区,从源头上预防水源污染,降低饮用水公共风险,保障饮用水安全。     

MoS_2/Bi_2S_3异质结光催化剂的制备及其光催化性能

以五水硝酸铋为铋源、钼酸钠为钼源、硫脲为硫源,采用简单的一步水热法合成了MoS_2/Bi_2S_3异质结光催化剂,采用XRD,SEM,TEM,BET,UV-Vis DRS技术对其进行了表征。表征结果显示,MoS_2纳米片在Bi_2S_3微棒表面生长,增加了比表面积和活性位点,并形成异质结构,促进了光生载流子的迁移,抑制了电子-空穴对的再复合。实验结果表明:钼酸钠与五水硝酸铋的质量比为1∶2时制备的复合光催化剂性能最好,反应180min时对亚甲基蓝的去除率可达96.4%,明显高于MoS_2和Bi_2S_3,且具有较高的稳定性;该催化剂对罗丹明B、甲基橙和4-硝基苯酚的去除率分别为97.1%、93.1%和90.5%,表明其对污染物具有普适性。     

以聚己内酯作为生物反硝化固体碳源的研究

为解决水体因低碳氮比而导致脱氮效率差的问题,将颗粒聚己内酯(PCL)重新塑形为阶梯环状,研究其作为反硝化过程的生物膜载体与固相碳源的反硝化性能。结果表明,在静态实验中,平均反硝化速率为8.57 mg NO3-N/(L·h);反硝化过程为零级反应。连续填充床实验中,超过90%的硝酸盐可被去除,出水NO2-N质量浓度低于0.20 mg/L;出水NH3-N质量浓度略有上升;出水溶解性有机碳(DOC)先上升后降低至1 mg/L左右。电子扫描显微镜扫描显示,PCL阶梯环反应表面空隙率较高,表面生物膜以杆菌为主,反应后被明显腐蚀;液相色谱检测显示PCL阶梯环分子量反应前后略有下降,其结构未受到破坏;表明该材料适合作为反硝化反应的碳源的同时,又可以作为载体供微生物附着生长。     

铁阳极电凝聚处理活性黑KN-B染料废水

对铁阳极电凝聚处理活性黑KN-B染料废水过程进行了实验研究.考察了电流密度、染料溶液初始pH值、电介质浓度及种类、温度、染料浓度等因素对脱色效率的影响.结果表明,在一定实验条件下,活性黑KN-B模拟废水的脱色效率达93%;电流强度、染料浓度、电解液初始pH值及电解质的种类对染料溶液脱色效率影响显著,电解液温度、电解质的浓度对脱色效率的影响不明显;以铁为阳极的原位电凝聚处理活性黑KN-B模拟废水混凝过程中主要作用机理以吸附电性中和为主;电凝聚过程中活性黑KN-B在阴极上发生了还原反应.     

滦河水体溶解性有机物的综合分级表征及其混凝去除过程

天然水体溶解性有机物(DOM)是微污染物的潜在载体,是消毒副产物的主要前驱物,自身又可能成为微污染物,因此研究其内在特性和去除机理有着重要的基础性科学意义.本研究综合利用化学、物理分级方法(即树脂和超滤分级法),对中国北方典型饮用水源--滦河水体的DOM进行全面分级表征.此水体DOM基本化学分级特征是憎水酸(HoA)、亲水性物质(HiM)含量较高,且具有季节稳定性;其物理分级特征是分子量＜1 kDa及3 kDa～10 kDa的组分含量较高,也表现出一定的时间稳定性.选用工业聚合铝(PAC)研究此DOM的基本混凝特征和内在混凝机理,结果表明,强憎水部分HoA及3 kDa～10 kDa间的有机物较易被去除,而较大分子量范围10 kDa～30 kDa间的有机物去除率较低,说明混凝过程中此DOM的物理性质不起主要作用,而化学性质更为重要.特别对DOM各组分作进一步(结合)分级研究,发现HoA主要在＞10 kDa范围.＜1 kDa的有机物中主要为HiM,但其中还含有HoA和弱憎水酸(WHoA),这使特定条件下部分＜1 kDa有机物被混凝去除成为可能.另外,HoA中按分子量大小仍可分为易去除和难去除部分,但分布不连续,易去除部分在3 kDa～10 kDa和＞30 kDa区间,而其10 kDa～30 kDa部分较难去除,说明可能存在其他结构性影响因素,值得深入研究.     

用水解酸化池-膜生物反应器处理活性艳红X-3B废水

采用水解酸化池-膜生物反应器处理含活性艳红X-3B的模拟废水,研究了水力停留时间（HRT）对水解酸化池废水处理效果的影响,考察了水解酸化池-膜生物反应器对废水的处理效果及膜生物反应器中污泥沉降性能对膜污染的影响。实验结果表明：水解酸化池HRT为16h时,废水的可生化性最好,挥发性脂肪酸质量浓度与COD比值为0．5;HRT为17h时,废水脱色率达69％,而COD的去除率受HRT影响较小;膜生物反应器主要起去除废水中COD的作用;水解酸化池-膜生物反应器处理后废水的脱色率和COD去除率分别为83％和97％;膜生物反应器中活性污泥沉降性能的变化直接影响膜污染的速率。