Catalytic destruction of dichloromethane using perovskite-type oxide catalysts

Dichloromethane (DCM, also known as methylene chloride [CH2Cl2]) is often present in industrial waste gas and is a valuable chemical product in the chemical industry. This study addresses the oxidation of airstreams that contain CH2Cl2 by catalytic oxidation in a tubular fixed-bed reactor over perovskite-type oxide catalysts. This work also considers how the concentration of influent CH2Cl2 (Co = 500-1000 ppm), the space velocity (GHSV = 5000-48,000 1/hr), the relative humidity (RH = 10-70%) and the concentration of oxygen (O2 = 5-21%) influence the operational stability and capacity for the removal of CH2Cl2. The surface area of lanthanum (La)-cobalt (Co) composite catalyst was the greatest of the five perovskite-type catalysts prepared in various composites of La, strontium, and Co metal oxides. Approximately 99.5% CH2Cl2 reduction was achieved by the catalytic oxidation over LaCoO3-based perovskite catalyst at 600 degrees C. Furthermore, the effect of the initial concentration and reaction temperature on the removal of CH2Cl2 in the gaseous phase was also monitored. This study also provides information that a higher humidity corresponds to a lower conversion. Carbon dioxide and hydrogen chloride were the two main products of the oxidation process at a relative humidity of 70%.     

氧化铁光催化降解活性染料的研究

用NaOH和Fe(NO3)3·9H2O共沉淀法制备Fe2O3的前驱体,分别在350℃,550℃,700℃烧结得到α-Fe2O3催化剂.通过对3种活性染料的降解实验,探讨了光照和光照时间的影响,比较了不同烧结温度下所得催化剂光催化活性的大小,得出350℃烧结的催化剂光催化活性最好.     

亚铁催化声化学降解罗丹明B

比较了不同金属离子对罗丹明B的声化学降解作用,发现超声时加入Fe2 反应速率常数为单独超声波降解时的1.6倍,反应在前5 h内符合假一级动力学.研究了亚铁离子强化声化学对罗丹明B的降解作用,考察了Fe2 用量,溶液初始pH值,曝气,反应温度和超声功率等因素对脱色速率的影响.研究表明,酸性条件有利于染料的脱色;有曝气时的声化学脱色速率常数是单独超声时的6倍;声化学反应的活化能较低,反应在低温就可以进行;超声功率的改变对脱色速率的影响不大.UV-VIS扫描图谱显示,染料在225 nm和256 nm处的紫外吸收明显降低,初步探讨了罗丹明B的降解机理.     

生物炭耦合菌剂去除污染水体中的苯胺

为了更有效地去除突发性污染水体中的致毒有机化合物,采用生物炭耦合微生物技术对污染水体中的苯胺进行了去除研究。首先,以柚皮为原料,利用高温裂解制备法,通过优化裂解温度和裂解时间,制备得到生物炭;进而,探明生物炭对苯胺的吸附特性与机制;最后,以体积比1:1制得Comamonas sp.TZ1和Pseudomonas sp.JH1混合菌剂,接种至生物炭反应器(R1)中构建生物炭耦合微生物反应器(R2),考察其对苯胺的处理效果。结果表明:生物炭较适宜的制备条件为裂解温度600 ℃和裂解时间2 h;对苯胺的吸附过程符合Freundlich等温方程,属于多分子层吸附;在连续动态运行18 d过程中,当水体中苯胺初始浓度分别由50 mg/L降至10 mg/L和10 mg/L降至5 mg/L时,R1中所吸附的苯胺因浓度差驱动作用重新进入水体,去除率分别为-194%和-21.19%,而R2则能一直呈现较好的去除效果。     

Effect of rice-straw biochar on selective biodegradation of nonylphenols in isomer specificity

In a previous study, we found that rice-straw biochar degraded and removed hydrophobic organic contaminants (HOCs) through coupled adsorption-biodegradation. However, few studies have determined whether biochar affects HOC isomer degradation and isomer-selective biodegradation or whether biochar can alter HOC isomer features, resulting in changes to HOC isomer residues in water environments. In this study, the effects of biochar at two dosages (0.001 and 0.01 g) on the biodegradation of ten isomers of a typical xenoestrogen of nonylphenol (NP) were evaluated. The results revealed that there were no effects of biochar on the adsorption of NP isomers. However, biochar addition affected the biodegradation of a specific isomer without altering the features of the NP isomers. The treatment of NP isomers with Pseudoxanthomonas sp. yielded degradation ratios ranging from 60.7 to 100%. At 0.001 g biochar treatment, the degradation of eight NP isomers was enhanced (except for NP₁₉₄ and NP_193a+b) due to their bulky structures. The degradation of the ten NP isomers was inhibited when 0.01 g biochar was added. These findings characterized the effects of biochar on NP isomer contaminants and provided basic information for the application of biochar for the remediation of NP isomer contaminants.

     

Aeolian flux of metals in Taiwan in the past 2600 years

To identify anthropogenic sources of pollution, it is useful to compare recent and historical data, yet unfortunately such data are lacking in Taiwan. Thus, we studied the sediments deposited in the remote anoxic, subalpine Great Ghost Lake over a time span of 2600 yrs. Not only could a baseline be established, but also natural variations could be identified. Aeolian Asian dust particles seem to have played a significant role in the flux of 26 elements (Al, As, Ba, Br, Ca, Cd, Ce, Cl, Cr, Cs, Cu, Fe, Ga, K, Mg, Mn, Na, Ni, Pb, Rb, Si, Sr, Ti, V, Zn and Zr) in Great Ghost Lake. The fluxes have generally been higher during dry periods, especially since 1350 AD. On the other hand, local pollution from lead seems to have gained importance since 1945 AD. Recent aeolian fluxes were also calculated based on sediment data, and those results agree with direct measurements obtained in the region.     

EPA develops process to destroy Kepone

Environmental Management -     

绿色食品在可持续发展战略中的地位和作用

本文以一系列详实的数据,介绍了当今世界遭受环境灾难的事实,从环境保护的角度阐明了发展绿色食品、实施绿色食品工程在可持续发展战略中的重要地位和作用     

超滤法处理含乳化油废液

采用板框式超滤装置对钢管玫冷却用乳化油废液进行处理试验,结果表明,板框式超滤器在压力低于０．４０ＭＰａ,运行温度４０－４５℃条件下,配用ＰＳＦ超滤膜,可将乳化油废液一次连续浓缩,含油量由２％增至４０－５０％,体积２０倍,超滤平均通量５－２０Ｌ（ｍ＾２．ｈ）＾－１,渗透液中含油量降至１００ｍｇ．ｌ＾－１以下,油分截留率大于９９％,ＣＯＤ截留率大于９０％     

青霉菌P－93对偶氮染料的降解特性研究

采用富集培养的方法，从土壤中分离得到一株对偶氮染料酸性大红（ＧＲ）和酸性黑（ＡＴＴ）有较强脱色能力的青霉菌Ｐ－９３（Ｐｅｎｉｃｉｌｌｉｕｍｓｐ．Ｐ－９３）。该菌以ＧＲ和ＡＴＴ作为唯一Ｃ源和唯一Ｎ源均能生长。Ｐ－９３在ｐＨ４．０─８．０的范围内对ＡＴＴ的脱色率都在８０％以上，在２８－３７℃的温度范围内对ＧＲ和ＡＴＴ的脱色率也都超过８０％。对降解产物的紫外─可见光光谱分析表明，对ＧＲ和ＡＴＴ在可见光区的吸收峰（４８７．１ｎｍ，４８６．２ｎｍ和５９６．５ｎｍ）明显消失，而在紫外区的光吸收有所加强。Ｐ－９３中降解ＧＲ和ＡＴＴ的酶主要存在于细胞内，其生物合成不受染料的诱导。