Characterizing the optimal operation of photocatalytic degradation of BDE-209 by nano-sized TiO2

Brominated flame retardants have been widely used in industry. There is a rapid growing public concern for their availabilities in the environment. Advanced oxidation process (AOP) is a promising and efficient technology which may be used to remove emerging chemicals such as brominated flame retardants. This project aims at investigating optimal operational conditions for the removal of BDE-209 using nano-scaled titanium(IV) oxide. The residual PBDE congeners after photocatalytical degradation of BDE-209 by TiO₂ were analysed by gas chromatography-mass spectrometry (GC-MS). It was found that the degradability of BDE-209 by TiO₂ was attributed to its photocatalytic activity but not the small size of the particles. The half-life of removing BDE-209 by TiO₂ was 3.05 days under visible light. Tetra- and penta-BDEs were the major degraded products of BDE-209. Optimum conditions for photocatalytical degradation of BDE-209 was found to be at pH 12 (93% ± 1%), 5, 10, 20 mg/L (93.0% ± 1.70%, 91.6% ± 3.21%, 91.9% ± 0.952%, respectively), respectively of humic acid and in the form of anatase/rutile TiO₂ (82% ± 3%). Hence, the efficiency of removing BDE-209 can be maximized while being cost effective at the said operating conditions.     

Fatty acids and algal lipids as precursors of chlorination by-products

Six common algal fatty acids (FAs) with different numbers of double bonds, lipophilic fractions and proteins extracted from the diatom Navicula pelliculosa and algal cells were chlorinated to evaluate their potential in generating disinfection by-products (DBPs). The result showed that the more double bonds in the FAs, the higher the amounts of chloroform and dichloroacetic acid (DCAA) produced, but such a pattern was not observed for trichloroacetic acid (TCAA). Based on the previously reported composition of fatty acids in algal lipids, the DBP generation potentials of algal lipids were calculated. These predicted values were much lower than those measured in the chlorinated algal lipophilic fraction, suggesting unknown lipophilic fraction(s) served as potent DBPs precursors. Another calculation attempted to predict DBP production in algal cells based on algal lipid and protein composition, given quantified measured DBP production per unit algal lipid and proteins. The analysis showed that the observed DBP production was similar to that predicted (< 35% difference), suggesting that algal biochemical compositions may serve as a bioindicator for preliminary estimation of chloroform, DCAA and TCAA formation upon chlorinating algae.     

袋式除尘器进气均布板结构参数对气流分布的影响分析

针对袋式除尘器的进气均布板主要结构参数对气流分布影响的问题,采用正交试验方法进行CFD模拟试验设计,并以气流速度相对均方根σ值作为气流均匀性的评价指标。研究结果给出了σ与板数n、板长L、挡板上端距灰斗顶部截面高度ΔH、挡板前后偏角θ及过滤风速v之间的函数关系式。表明适当增加n、增大ΔH和θ、减小L、降低v,可以提高进气流分布均匀程度,影响进气均匀分布程度的排序为L>θ>n>ΔH>ΔL。     

河流水环境容量安全边际研究

水环境容量安全边际是污染物总量控制的关键。运用河流二维稳态水质模型,计算大宁河回水区内COD环境容量,并采用一阶误差分析法分析模型关键参数对大宁河COD环境容量影响程度,科学计算大宁河水环境容量安全边际值。结果表明,三峡库区坝前水位175 m时,大宁河回水区内COD环境容量为729.06 t/a;模型参数对环境容量影响顺序为:背景浓度(C0)>混合区长度(x)=水深(h)>流速(u)=扩散系数(E)y>降解系数(K);大宁河回水区内安全边际值为84.06 t/a,占环境容量的11.53%。文章科学地计算大宁河回水区内COD环境容量安全边际,而非人为定性提出,为三峡库区河流水环境容量安全边际确定提供理论依据。     

大气细颗粒物(PM_(2.5))在环境科学中的研究简述

细颗粒物作为一种重要的大气污染物,其形态与组成非常复杂,本身所具有的毒性和对环境的有害性已日益受到重视。文章对细颗粒物PM2.5在环境科学中的研究进行了概括,提出了自己的一些见解。     

氨法烟气脱硫循环液沉降试验研究

通过湿法烟气脱硫副产硫酸铵生产工艺中的循环母液混凝试验,讨论母液的沉降性能,初步探讨母液被循环浓缩的程度对混凝处理效果的影响。     

苯酚对厌氧氨氧化污泥脱氮效能长短期影响

通过接种厌氧氨氧化(ANAMMOX)污泥,研究了苯酚浓度对ANAMMOX污泥脱氮效能长短期影响.短期结果表明,随着苯酚浓度的增大,氮去除率快速下降.当苯酚浓度大于600 mg·L-1时,NH+4-N的去除率降低到6%以下,TN的去除率只有10%左右.长期实验结果表明,当苯酚浓度小于100 mg·L-1时,NH+4-N的去除率都能达到99%以上,说明低浓度苯酚对ANAMMOX菌有一个驯化的过程.当苯酚浓度高于400 mg·L-1时,NH+4-N的去除率只有23.59%,TN去除率只有50.3%,ANAMMOX污泥抑制明显,与短期结果相同.此时反硝化菌活性明显高于ANAMMOX菌,说明苯酚可作为有机碳源诱发体系中发生反硝化反应,最终导致反硝化菌在体系中占据主导地位.但高浓度(1 000 mg·L-1)苯酚对反硝化菌也具有抑制作用.通过拟合得到苯酚对ANAMMOX半抑制有效浓度(IC50)为71.57 mg·L-1.经过18 d的恢复后,NH+4-N去除率基本恢复,但氮素之间的转化计量式发生了改变,ρ(NH+4-N)去除/ρ(NO-2-N)去除/ρ(NO-3-N)生成为1∶0.86∶0.2.研究结果表明,将苯酚控制在合理范围内可以使反应器达到同步脱氮除酚的效果.     

不同制备温度的水稻生物炭电子交换能力研究

为探究不同热解温度下生物炭的电子交换能力,通过限氧升温炭化法,利用水稻秸秆在不同热解温度条件下制备生物炭,与氧气、铁氰化钾氧化剂和柠檬酸钛还原剂进行氧化还原反应,对生物炭的得电子能力（EAC）和失电子能力（EDC）进行定量分析.结果显示,热解温度对生物炭的电子交换能力有较大影响,随热解温度升高至500℃时,生物炭的EAC和EDC达到最大,分别为3.86,1.72mmol/g高于500℃后,随着温度的增加,EAC和EDC逐渐减小,这是由于生物炭的醌类和酚类官能团的结构改变以及持久性自由基强度变化的联合作用.此外,柠檬酸钛和连二硫酸钠两种氧化还原电位不同的还原剂进一步证实了还原剂电位对生物炭EAC的影响.且生物炭具有氧化还原的可逆性,可逆的EAC与EDC之和近似等于生物炭的电子储存能力.     

耦合发酵产氢尾液处理的微生物电化学系统研究

区别于传统的稀释或加缓冲剂调节pH值的方法,本文提出采用微生物电解池（MEC）电调控暗发酵尾液pH值,并进一步采用微生物电合成系统（MES）降解废液产甲烷.结果表明,在MEC处理产氢暗发酵尾液过程中,伴随着阴极侧氢气的产生,暗发酵尾液中大量H⁺被消耗,溶液pH值从4.5升高到8.7;随后在MES中,产氢发酵尾液中有机物被进一步降解产生甲烷,其平均产甲烷速率达到4.5mmol/（L·d）,且在21d内化学需氧量（COD）去除率达到89%,远优于没有经过pH调控的产氢发酵尾液MES中的产甲烷性能.     

Morphology, composition, and sources of individual aerosol particles at a regional background site of the YRD, China

Aerosol samples were collected at Lin'an, a background site of Yangtze River Delta(YRD).Morphology, size, composition, and mixing state of individual aerosol particles were characterized by transmission electron microscopy(TEM) coupled with energy dispersive X-ray spectroscopy(EDS), and the soluble ions of PM_(1.0) were studied by aerosol mass spectrometer(AMS). The daily average AMS mass concentrations of sulfate, nitrate, and ammonium were about 5.8, 8.6, and 5.6 μg/m~3, respectively. Individual aerosol particles were classified into seven types: S-rich, K-rich, organic matter(OM), soot, fly ash, metal, and mineral. S-rich particles were dominant in all size bins, and 51%(by number) of S-rich particles were internally mixed with other particles. The fraction of organic coating particles was 13.7% in morning, 25.2% in afternoon, and 11% in evening, suggesting that the strong photochemical process during afternoon produced more secondary organic aerosols(SOA) on the surface of inorganic particles. Fly ash and metal particles were abundant during the day, suggesting the influence of emissions from coal-fired power plants and steel plants. The results indicate that the intense industrial emissions in the YRD significantly transported to the background areas. PM_(2.5) concentration may be lower in background air than in urban air but complex mixing state of aerosol particles indicates that the long-range transported particles substantially influenced the background air quality.