Comparison of methods for evaluation of activity of photocatalytic films

Objective

This work aims to investigate the correlation between the photocatalytic activity determined by methylene blue bleaching (DIN 52980), stearic acid degradation, and degradation of acetone in gas phase.

Method

The photocatalytic TiO₂ coatings included in this investigation ranged from thin commercially available coatings (Activ^TM and BioClean^TM) and ready to use suspensions (Nano-X PK1245) to lab-produced PVD and sol?Cgel coatings. XRD analysis of the photocatalytic coatings showed that all the coatings consisted of nanocrystalline anatase, although the thickness and porosity varied considerably.

Results

The study showed that the reproducibility of the activity measurements was good. However, more importantly, the investigation showed that there is a good correlation between the activities determined by the different methods even though the characteristics of the photocatalytic coatings and the organic probe molecules varied considerably.

Conclusion

The overall findings of this work suggest that there is a good correlation between the investigated methods. These results are promising for the future work concerning standardization of methods for determination of the activity of photocatalytic films.     

Transformation and biodegradation of 1,2,3-trichloropropane (TCP)

PURPOSE: 1,2,3-Trichloropropane (TCP) is a persistent groundwater pollutant and a suspected human carcinogen. It is also is an industrial chemical waste that has been formed in large amounts during epichlorohydrin manufacture. In view of the spread of TCP via groundwater and its toxicity, there is a need for cheap and efficient technologies for the cleanup of TCP-contaminated sites. In situ or on-site bioremediation of TCP is an option if biodegradation can be achieved and stimulated. This paper presents an overview of methods for the remediation of TCP-contaminated water with an emphasis on the possibilities of biodegradation. CONCLUSIONS: Although TCP is a xenobiotic chlorinated compound of high chemical stability, a number of abiotic and biotic conversions have been demonstrated, including abiotic oxidative conversion in the presence of a strong oxidant and reductive conversion by zero-valent zinc. Biotransformations that have been observed include reductive dechlorination, monooxygenase-mediated cometabolism, and enzymatic hydrolysis. No natural organisms are known that can use TCP as a carbon source for growth under aerobic conditions, but anaerobically TCP may serve as electron acceptor. The application of biodegradation is hindered by low degradation rates and incomplete mineralization. Protein engineering and genetic modification can be used to obtain microorganisms with enhanced TCP degradation potential.     

Particulate matter emission rates from beef cattle feedlots in Kansas-reverse dispersion modeling

Open beef cattle feedlots emit various air pollutants, including particulate matter (PM) with equivalent aerodynamic diameter of 10 microm or less (PM10); however limited research has quantified PM10 emission rates from feedlots. This research was conducted to determine emission rates of PM10 from large cattle feedlots in Kansas. Concentrations of PM10 at the downwind and upwind edges of two large cattle feedlots (KS1 and KS2) in Kansas were measured with tapered element oscillating microbalance (TEOM) PM10 monitors from January 2007 to December 2008. Weather conditions at the feedlots were also monitored. From measured PM10 concentrations and weather conditions, PM10 emission rates were determined using reverse modeling with the American Meteorological Society/U.S. Environmental Protection Agency Regulatory Model (AERMOD). The two feedlots differed significantly in median PM10 emission flux (1.60 g/m2-day for KS1 vs. 1.10 g/m2-day for KS2) but not in PM10 emission factor (27 kg/1000 head-day for KS1 and 30 kg/1000 head-day KS2). These emission factors were smaller than published U.S. Environmental Protection Agency (EPA) emission factor for cattle feedlots.     

纳米生态基对水产养殖污水的处理效果

采用三因子四水平的正交设计,实验研究了纳米生态基在不同温度、溶解氧和水力停留时间下对水产养殖污水的处理效果,确定了纳米生态基处理养殖污水的最佳条件。结果表明,含氨氮和亚硝氮浓度较高的模拟养殖污水用纳米生态基挂膜,所需时间约为22 d。纳米生态基对氨氮的去除效果明显,平均去除率达到93.5%。对氨氮去除率的影响程度,水力停留时间>温度>溶解氧。当温度为30℃,DO为5.43 mg/L,HRT为0.33 h时,纳米生态基对氨氮的处理能力最佳,去除率达到94.6%。纳米生态基对亚硝氮的平均去除率为69.3%。对亚硝氮去除率的影响程度,水力停留时间>溶解氧>温度。当温度为21℃,DO为6.40 mg/L,HRT为0.33 h时,纳米生态基对亚硝氮的处理能力最佳,去除率为71.5%。纳米生态基处理养殖污水的最佳条件:温度为30℃,DO为6.40 mg/L,HRT为0.33 h。     

Fe2O3-Cr2O3/TiO2系列催化剂的结构和脱硝性能

研究以纳米TiO2为载体,浸渍负载过渡金属氧化物,以CO为还原剂的脱硝催化剂的脱硝性能。实验中以计算量的Ni(NO3)2和Fe(NO3)3混合溶液浸渍纳米TiO2粉末,室温下搅拌30 min至混合均匀,放入旋转蒸发器中,70℃下至水分蒸干为止;所得粉末在550℃下、空气气氛中焙烧4 h即得所需催化剂。用以上方法分别制备2%Fe2O3-10%Cr2O3/TiO2、4%Fe2O3-8%Cr2O3/TiO2、6%Fe2O3-6%Cr2O3/TiO2、8%Fe2O3-4%Cr2O3/TiO2与10%Fe2O3-2%Cr2O3/TiO2等5种催化剂样品。实验结果表明,制备的催化剂具有较好的结构,分散较为均匀。对于CO+NO反应,Fe2O3-Cr2O3/TiO2系列催化剂具有较好的催化活性,NO的转化率都达到了100%。其中,10%Fe2O3-2%Cr2O3/TiO2样品具有最好的低温活性,H2-TPR结果表明,这是由于10%Fe2O3-2%Cr2O3/TiO2催化剂更易于被CO预还原。     

光催化过程中羟基自由基的产生与效能

采用异丙醇淬灭的方法考察了羟基自由基在光催化氧化酸性橙II过程中的产生和效能,研究了TiO2(P-25)的浓度、异丙醇的用量、酸性橙II的初始浓度、初始pH条件和天然共存离子对羟基自由基贡献率的影响。结果表明,在TiO2(P-25)浓度提高时羟基自由基的贡献率逐步提高并稳定在77.6%,异丙醇的投加量对羟基自由基的贡献率影响不大,酸性橙II初始浓度的提高则使羟基自由基的贡献率降低。在中性pH条件下羟基自由基的贡献率最高,酸性或碱性条件下较低。天然共存离子中HCO3-对羟基自由基的淬灭效应最强,F-的淬灭效应最弱。     

某钢厂烧结烟气脱硫系统滤袋失效原因分析

分析了聚苯硫醚自身特性,从而了解目前烧结烟气脱硫系统袋式除尘器中选择其作为滤料的原因。并就目前某钢厂烧结烟气脱硫系统实际发生的滤袋失效问题,通过扫描电镜、EDS能谱分析及烧失量实验对滤袋进行分析,发现材料中混入的玻璃纤维是造成其失效的主要原因,为今后实际工程中滤袋的选择提供依据,从而尽量减少不必要的损失,确保烟气脱硫项目的正常运行。     

生物膜填料塔净化模拟烟气和电厂烟气中SO2和NOx的对比实验

对生物膜填料塔对模拟烟气和电厂烟气的净化效果进行了实验研究。实验对比分析了在相同的实验条件下生物膜填料塔对不同烟气中SO2和NOx的净化效率。实验结果表明,在循环液温度在24～35℃、空床停留时间（EBRT）为60s、喷淋量为8～10L／h、脱硫塔的pH为0．8～1．5、脱氮塔的pH为7．5～8．0的条件下,生物膜填料塔对模拟烟气和电厂烟气中SO2的净化效率都很高,但模拟烟气条件下的总脱氮率的平均值为80％,而在电厂烟气条件下只有35％。经分析认为,脱氮率产生差异的主要原因是电厂烟气中杂质的影响,以及烟气中氧气含量的不同,同时因为生长条件不同从而驯化出的微生物群体组成也不同。     

Degradation of Phenolic Resin by Tremetes versicolor

A phenolic resin that is used as syntan in leather manufacturing was degraded using Tremetes versicolor. On degradation of this resin for eight days, the reduction in biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total organic carbon (TOC) were 65.11, 76.66 and 72.94% respectively. It was found from the infra red (IR) spectra of the samples that up to seven days the aromaticity was not perturbed however there were reductions in BOD and COD. Addition of co-substrate starch, brought about reduction in BOD, COD and TOC by 85.36, 91.93 and 89.98% respectively. After eight days, there observed a disturbance in the aromatic ring. The enzyme was extracted and assayed for polyphenol oxidase and laccase. Polyphenol oxidase activity and laccase activity of the crude enzyme were found to be 31.4 and 1.67 U/mL. On ammonium sulfate precipitation and dialysis, the polyphenol oxidase activity and laccase activity were enhanced by 1.5- and 3.2-folds respectively.