Pd/activated carbon sorbents for mid-temperature capture of mercury from coal-derived fuel gas

Higher concentrations of Hg can be emitted from coal pyrolysis or gasification than from coal combustion, especially elemental Hg. Highly efficient Hg removal technology from coal-derived fuel gas is thus of great importance. Based on the very excellent Hg removal ability of Pd and the high adsorption abilities of activated carbon（AC） for H2 S and Hg, a series of Pd/AC sorbents was prepared by using pore volume impregnation, and their performance in capturing Hg and H2 S from coal-derived fuel gas was investigated using a laboratory-scale fixed-bed reactor. The effects of loading amount, reaction temperature and reaction atmosphere on Hg removal from coal-derived fuel gas were studied. The sorbents were characterized by N2 adsorption, X-ray diffraction（XRD） and X-ray photoelectron spectroscopy（XPS）. The results indicated that the efficiency of Hg removal increased with the increasing of Pd loading amount, but the effective utilization rate of the active component Pd decreased significantly at the same time. High temperature had a negative influence on the Hg removal. The efficiency of Hg removal in the N2-H2S-H2-CO-Hg atmosphere（simulated coal gas） was higher than that in N2-H2S-Hg and N2-Hg atmospheres, which showed that H2 and CO, with their reducing capacity, could benefit promote the removal of Hg. The XPS results suggested that there were two different ways of capturing Hg over sorbents in N2-H2S-Hg and N2-Hg atmospheres.     

Effect of a high strength chemical industry wastewater on microbial community dynamics and mesophilic methane generation

A high strength chemical industry wastewater was assessed for its impact on anaerobic microbial com- munity dynamics and consequently mesophilic methane generation. Cumulative methane production was 251 mL/g total chemical oxygen demand removed at standard temperature and pressure at the end of 30 days experimental period with a highest recorded methane percentage of 80.6% of total biogas volume. Volatile fatty acids （VFAs） analysis revealed that acetic acid was the major intermediate VFAs produced with propionic acid accumulating over the experimental period. Quantitative analysis of microbial communities in the test and control groups with quantitative real time polymerase chain reaction highlighted that in the test group, Eubacteria （96.3%） was dominant in comparison with methanogens （3.7%）. The latter were dominated by Methanomicrobiales and Methanobacteriales while in test groups increased over the experimental period, reaching a maximum on day 30. Denaturing gradient gel electrophoresis profile was performed, targeting the 16S rRNA gene of Eubacteria and Archaea, with the DNA samples extracted at 3 different time points from the test groups. A phylogenetic tree was constructed for the sequences using the neighborhood joining method. The analysis revealed that the presence of organisms resembling Syntrophomonadaceae could have contributed to increased production of acetic and propionic acid intermediates while decrease of organisms resembling Pelotomaculum sp. could have most likely contributed to accumulation of propionic acid. This study suggested that the degradation of organic components within the high strength industrial wastewater is closely linked with the activity of certain niche microbial communities within eubacteria and methanogens.     

Characteristics of atmospheric particles and heavy metals in winter in Chang-Zhu-Tan city clusters, China

To understand the pollution characteristics of atmospheric particles and heavy metals in winter in Chang-Zhu-Tan city clusters, China, total suspended particulate(TSP) and PM10samples were collected in cities of Changsha, Zhuzhou and Xiangtan from December 2011 to January 2012, and heavy metals of Cd, Pb, Cr, and As were analyzed. It shows that the average TSP concentration in Changsha, Zhuzhou and Xiangtan were(183 ± 73),(201 ± 84) and(190 ± 66) μg/m3respectively, and the average PM10 were(171 ± 82),(178 ± 65) and(179 ± 55) μg/m3respectively. The lowest TSP and PM10concentrations occurred at the background Shaping site of Changsha. The average ratio of ρ(PM10)/ρ(TSP) was 91.9%, ranging from 81.3% to 98.9%. Concerning heavy metals, in TSP samples, the concentration of Cr, As, Cd and Pb were 28.8–56.5, 18.1–76.3, 3.9–26.1 and 148.0–460.9 ng/m3, respectively, while in PM10samples, were 16.4–42.1, 15.5–67.9, 3.3–22.2 and 127.9–389.3 ng/m3, respectively. The enrichment factor of Cd was the highest, followed by Pb and As, while that of Cr was the lowest.     

Community structure and elevational diversity patterns of soil Acidobacteria

Acidobacteria is one of the most dominant and abundant phyla in soil,and was believed to have a wide range of metabolic and genetic functions. Relatively little is known about its community structure and elevational diversity patterns. We selected four elevation gradients from 1000 to 2800 m with typical vegetation types of the northern slope of Shennongjia Mountain in central China. The vegetation types were evergreen broadleaved forest,deciduous broadleaved forest,coniferous forest and sub-alpine shrubs. We analyzed the soil acidobacterial community composition,elevational patterns and the relationship between Acidobacteria subdivisions and soil enzyme activities by using the 16 S rRNA meta-sequencing technique and multivariate statistical analysis. The result found that 19 known subdivisions as well as an unclassified phylotype were presented in these forest sites,and Subdivision 6 has the highest number of detectable operational taxonomic units(OTUs). A significant single peak distribution pattern(P 0.05) between the OTU number and the elevation was observed. The Jaccard and Bray–Curtis index analysis showed that the soil Acidobacteria compositional similarity significantly decreased(P 0.01) with the increase in elevation distance. Mantel test analysis showed the most of the soil Acidobacteria subdivisions had the significant relationship(P 0.01) with different soil enzymes. Therefore,soil Acidobacteria may be involved in different ecosystem functions in global elemental cycles. Partial Mantel tests and CCA analysis showed that soil pH,soil temperature and plant diversity may be the key factors in shaping the soil Acidobacterial community structure.     

Phytoremediation of levonorgestrel in aquatic environment by hydrophytes

Adsorption and degradation of levonorgestrel （LNG） by two hydrophytes, Cyperus alternfolius （CA） and Eichhornia crassipes （EC）, were investigated under light-shielding conditions in the water column. Variations of LNG concentrations in water, plant root epidermis, root, stem and leaf of the plants were analyzed. The results indicated that the removal efficiency of LNG by hydrophytes over the period of 50 days was significantly greater than the blank control （p 〈 0.05）, with the removal rates of 79.80%± 3.10% and 78.86% ± 2.55% for CA and EC, respectively. Compared with bio-adsorption, bio-conversion of LNG was found to be the dominant elimination pathway, evidenced by relatively high conversion rates （77.31% ±2.68% for CA and 77.82% ± 2.95% for EC）, while the adsorption rates were lower （1.77% ± 0.90% for CA and 1.05% ± 0.40% for EC）. The bio-adsorption and conversion of LNG showed no significant differences between the two hydrophytes. Additionally, the mineralization on root epidermis played an important role in the reduction of LNG in water.     

汞污染农田土壤低温热解处理性能研究

选取贵州清镇地区汞污染农田土壤作为低温热解修复试验对象,研究处理温度、处理时间以及土壤含水率对低温热解法去除土壤汞效率的影响。同时采用连续浸提法对土样中7种形态的汞进行提取,分析热解升温过程中各形态汞的变化状况。结果表明:(1)处理温度越高,汞去除效率越大。当温度为350℃时,去除率达到90%以上。(2)处理时间越长,汞的去除率越高。处理持续时间为90min时,去除率达到90%。(3)土壤含水率越高,汞去除率越低。当风干时间10 d,土壤含水率13.8%时为处理土壤最佳条件。(4)7种形态的汞随温度升高均下降显著,当温度达到350℃时,处理后土样中水溶态和交换态已完全去除,其他形态的去除率也均达到90%以上,土样中最终以残渣态汞为主,环境风险小。     

黄石市典型农业土壤中重金属污染水平及评价

以黄石市阳新县某大型农场作为研究区,于2012年2月采集8个代表性表层(0~20 cm)土壤样品,采用火焰-原子吸收分光光度法分析了各重金属元素(Cu、Pb、Zn、Cd、Mn、Co)的总量及BCR连续提取法提取土壤中重金属的弱酸态、可还原态、可氧化态和残渣态含量。结果显示,Cu、Pb、Zn、Cd、Mn和Co总量的平均值分别为122.10、141.29、335.53、2.18、2 606.58和128.27 mg/kg,其中Cd超过了土壤环境三级标准限值,Mn具有最强的变异系数,受到外来污染因素的影响最大。通过地积累指数法和潜在生态危害法表明,6种重金属累积程度由高到低依次为CdCoCuPbZnMn,且Cd、Mn为主要生态风险因子。同时由形态分析可知,Cu、Pb、Cd、Zn、Mn和Co的化学形态分布均以残渣态为主,说明该农场土壤中重金属元素比较稳定,不易迁移转化,对生物的毒性较小。     

水库水氯化消毒副产物毒性研究

为了证实水库出水的氯化消毒副产物CHClBr2和CHBr3具有一定的遗传毒性,将水库出水进行浓缩富集研究其对小鼠脾脏淋巴细胞DNA的影响。同时分别与水库枯水期和丰水期出水的小鼠彗星实验结果进行了对比,发现氯化消毒副产物CHClBr2和CHBr3的DNA损伤效应同时高于两个水期的出厂水。     

剩余污泥对柠檬黄-85的吸附行为

以城市污水厂中的剩余污泥为主要原料制备污泥吸附剂(SA),并用于柠檬黄-85(Tt-85)脱色的实验研究。静态实验主要考察了pH值、投加量、反应时间、反应温度和Tt-85初始浓度对吸附的影响。结果表明:在投加质量浓度为6 g/L,pH值=2.0,温度为25℃的条件下,反应90 min后,SS对水中初始质量浓度为65 mg/L和221 mg/L的Tt-85去除率分别达到了97%和75%。对动力学实验数据进行拟合,发现准二级动力学模型能较好地描述SA对Tt-85的吸附行为。动态吸附柱实验表明,污泥凝胶球对水中Tt-85的去除率为64%。Langmuir等温吸附模型符合SA对Tt-85的吸附过程,其最大吸附质量比为27.78 mg/g,由SEM,FTIR和XRD的分析可得,SA对柠檬黄-85的化学吸附主要发生在表面,其中SA表面羟基官能团起到关键性作用。     

可再生胺类脱硫剂的选择研究

采用哌嗪等二元胺和二乙醇胺为吸收剂,对模拟烟气进行SO2的吸收解吸实验研究,筛选出性能优异的吸收剂,并考察添加剂H2 S O 4对其性能的影响。实验表明:可再生胺类吸收剂脱硫率可接近100%,二元胺吸收剂较醇胺的SO 2吸收量大、pH值随时间变化慢、首次解吸率高;羟乙基支链对胺类吸收剂的抗氧化能力、SO2吸收量和首次解吸率均有影响,环状二元胺比链状二元胺的抗氧化能力好、首次解吸率高;在N-(2-羟乙基)哌嗪溶液中添加硫酸构成N-(2-羟乙基)哌嗪/H 2S O 4脱硫体系后,脱硫率未受影响、SO2吸收量变小、首次解吸率显著提高,具有更好的循环使用性能。