Journal of Environmental Sciences - Volume 17, issue 2

Authors: WANG, Fang | YANG, Feng-lin | LIU, Yi-hui | ZHANG, Xing-wen

Article Type: Research Article

Abstract: Cultivation of aerobic granules for simultaneous nitrification and denitrification in two sequencing batch airlift bioreactors was studied. Conventional activated floc and anaerobic granules served as main two inoculated sludge in the systems. Morphological variations of sludge in the reactors were observed. It was found that the cultivation of aerobic granules was closely associated with the kind of inoculated sludge. Round and regular aerobic granules were prevailed in both reactors, and the physical …characteristics of the aerobic granules in terms of settling ability, specific gravity, and ratio of water containing were distinct when the inoculate sludge was different. Aerobic granules formed by seeding activated floc are more excellent in simultaneous nitrification and denitrification than that by aerobic granules formed from anaerobic granules. It was concluded that inoculated sludge plays a crucial role in the cultivation of aerobic granules for simultaneous nitrification and denitrification. Show more

Keywords: aerobic granulation, inoculated sludge, nitrification, denitrification, inner structure, sludge morphology

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 268-270, 2005

Authors: ZHANG, Ya-lei | FANG, Zhen-wei | XU, De-qiang | XIAO, Yi-ping | ZHAO, Jian-fu | QIANG, Zhi-min

Article Type: Research Article

Abstract: An aerobic bacterium strain, F-3-4, capable of effectively degrading 2,6-di-tert-butylphenol (2, 6-DTBP), was isolated and screened out from an acrylic fiber wastewater and the biofilm in the wastewater treatment facilities. This strain was identified as Alcaligenes sp. through morphological, physiological and biochemical examinations. After cultivation, the strain was enhanced by 26.3% in its degradation capacity for 2,6-DTBP. Results indicated that the strain was able to utilize 2,6-DTBP, lysine, lactamine, citrate, n-utenedioic acid …and maiic acid as the sole carbon and energy source, alkalinize acetamide, asparagine, L-histidine, acetate, citrate and propionate, but failed to utilize glucose, D-fructose, D-seminose, D-xylose, serine and phenylalanine as the sole carbon and energy source. The optimal growth conditions were determined to be: temperature 37°C, pH 7.0, inoculum size 0.1% and shaker rotary speed 250 r/min. Under the optimal conditions, the degradation kinetics of 2,6-DTBP with an initial concentration of 100 mg/L was studied. Results indicated that 62.4% of 2,6-DTBP was removed after 11 d. The degradation kinetics could be expressed by Eckenfelder equation with a half life of 9.38 d. In addition, the initial concentration of 2,6-DTBP played an important role on the degradation ability of the strain. The maximum initial concentration of 2,6-DTBP was determined to be 200 mg/L. Above this level, the strain was overloaded and exhibited significant inhibition. Show more

Keywords: 2,6-di-tert-butylphenol, bacterium strain, Alcaligenes sp., isolation

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 271-275, 2005

Authors: HUANG, Yi | TAO, Shu | CHEN, You-jian

Article Type: Research Article

Abstract: To understand the roles of mycorrhiza in metal speciation in the rhizosphere and the impact on increasing host plant tolerance against excessive heavy metals in soil, maize (Zea mays L.) inoculated with arbuscular mycorrhizal fungus (Glomus mosseae) was cultivated in heavy metal contaminated soil. Speciations of copper, zinc and lead in the soil were analyzed with the technique of sequential extraction. The results showed that, in comparison to the bolked soil, the exchangeable copper increased from …26% to 43% in non-infected and AM-infected rhizoshpere respectively; while other speciation (organic, carbonate and Fe-Mn oxide copper) remained constant and the organic bound zinc and lead also increased but the exchangeable zinc and lead were undetectable. The organic bound copper, zinc and lead were higher by 15%, 40% and 20%, respectively, in the rhizosphere of arbuscular mycorrhiza infected maize in comparison to the non-infected maize. The results might indicate that mycorrhiza could protect its host plants from the phytotoxicity of excessive copper, zinc and lead by changing the speciation from bio-available to the non-bio-available form. The fact that copper and zinc accumulation in the roots and shoots of mycorrhia infected plants were significantly lower than those in the non-infected plants might also suggest that mycorrhiza efficiently restricted excessive copper and zinc absorptions into the host plants. Compared to the non-infected seedlings, the lead content of infected seedlings was 60% higher in shoots. This might illustrate that mycorrhiza have a different mechanism for protecting its host from excessive lead phytotoxicity by chelating lead in the shoots. Show more

Keywords: heavy metal speciation, arbuscular mycorrhiza, Glomus mosseae, rhizosphere

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 276-280, 2005

Authors: HU, Yong-you | WANG, Li-li

Article Type: Research Article

Abstract: The optimum media height of carbon oxidation and nitrification in a down-flow biological aerated filter was determined, and the distribution of the heterotrophic and nitrifying populations through studying the changes of organic carbon contents and ammonia concentration at different media height was got. The results showed that as a down flow BAF with granular media, the active layer of nitrifiers was deeper than heterotrophs in BAF. And the optimum media height for the removal of SS, …COD_{Cr} and NH_4^+ -N was 40 cm, 60 cm and 80 cm respectively. The removal efficiency of SS, COD_{Cr} and NH_4^+ -N was 79.1%, 63.9% and 96.4% respectively under the influent COD_{Cr} and NH_4^+ -N of 122.1 mgCOD_{Cr} /L and 14.84 mgNH_4^+ -N/L, the influent flux of 15.8 L/h, air to liquid ratio of 3: 1. Show more

Keywords: biological aerated filter, bed material height, sewage treatment

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 281-284, 2005

Authors: LU, Zhi-qiang | ZHENG, Wen-jiao | MA, Li

Article Type: Research Article

Abstract: The polycyclic aromatic hydrocarbons (PAHs) concentrations were determined in the root of three mangrove species (Kandelia candel, Avicennia marina and Bruguiera gymnorrhiza) and their growing environment (sediment) in mangrove wetlands of Jiulong River Estuary, Fujian, China. The total PAHs (16 parent PAHs) in mangrove sediments ranged from 193.44 to 270.53 ng/g dw, with a mean value of 231.76 ± 31.78 ng/g dw. Compared with other mangrove and coastal marine sediments, the PAHs concentrations of all the …sampling areas in this study were at relatively lower level. The total PAHs (13 parent PAHs) values varied from 30.83 to 62.73 ng/g dw in mangrove roots. Benzo[a] pyrene (five-ring), fluoranthene (four-ring) and pyrene (four-ring) dominated in mangrove sediments. Based on ratios of phenathrene/anthracene, fluoranthene/pyrene and fluoranthene/pyrene + fluoranthene, the main possible sources of surface sediment PAHs were identified as grass, wood or coal combustion for mangrove wetlands of Jiulong River Estuary. Naphthalene (two-ring)and phenathrene (three-ring) were the most abundant compounds in mangrove roots. Sediment-to-vegetation bioconcentration factors (BCF_{sv} S) were calculated and their relationships with PAHs' physico-chemical properties were investigated. The average BCF_{sv} s of PAHs for three mangrove species roots were almost all under the level of 1 except for naphthalene. Good linear relationship between BCF_{sv} values for mangrove roots and PAHs water solubility, octanol-water partitioning coefficients was derived in present study. The solubility and the octanol-water partition coefficient were proved to be good predictors for the accumulation of PAHs in mangrove roots, respectively. Show more

Keywords: mangrove, PAHs, Jiulong River Estuary, bioconcentration factors

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 285-289, 2005

Authors: YANG, Shao-gui | QUAN, Xie | LI, Xin-yong | FANG, Ning | ZHANG, Ning | ZHAO, Hui-min

Article Type: Research Article

Abstract: The TiO_2 nanotube sample was prepared via a NaOH solution in a Teflon vessel at 150°C. The as-prepared nanotubes were then treated with H_2 SO_4 solutions. The TiO_2 nanotube has a crystalline structure with open-ended and multiwall morphologies. The TiO_2 nanotubes before and after surface acid treatment were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-VIS …dispersive energy spectrophotometry (DRS). The photocatalytic activity of the samples was evaluated by photocatalytic degradation of acid orange II in aqueous solutions. It was found that the order of photocatalytic activity was as follows: TiO_2 nanotubes treated with 1.0 mol/L H_2 SO_4 solution (TiO_{2 (1.0M H_2SO_4)} nanotubes) > TiO_2 nanotubes treated with 0.2 mol/L H_2 SO_4<FORMULA> solution (TiO<FORMULA>_{2(0.2MH_2SO_4)} nanotubes) > TiO_2 nanotubes > TiO_2 powder. This was attributed to the fact that TiO_2 nanotubes treated with H_2 SO_4 was composed of smaller particles and had higher specific surface areas. Furthermore, the smaller TiO_2 particles were beneficial to the transfer and separation of photo-generated electrons and holes in the inner of and on the surface of TiO_2 particles and reduced the recombination of photo-generated electrons and holes. Acid treatment was particularly effective for TiO_2 nanotubes, this increase in activity was correlated with the concentration of H_2 O_4 solution. Show more

Keywords: titania nanotube, photocatalytic activity, acid orange II, H_2SO_4 solutions

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 290-293, 2005

Authors: LIU, Yan-ju | DING, Hui | ZHU, Yong-guan

Article Type: Research Article

Abstract: The concentrations of Fe, Mn, Al, Zn, Pb, Ni, Cr, and As were measured in soils and leaves from 21 plant species growing on hills near the Beijing Steel Factory (BSF) and 17 plant species in the Beijing Botanical Garden (BBG). The results showed that soils from BSF were Zn contaminated according to the threshold of natural background of China. There was a metal contamination of the soils by Ni, and Cr in BSF comparing with those in BBG. The …comparison between concentrations of metals in leaves from both sites indicated that, in general, accumulation of metals in the leaves of the same species was significantly different between the two sites. Even within the same locality each species accumulation of metals was significantly variable. The study aimed to screen landscape plants for the capacity to clean-up toxic metals in soils, and developed an overall metal accumulation index (MAI) for leaves and then categorized the MAI that can be applied broadly in the selection of species in polluted areas. To do this, the spectrum of MAI values were divided into four classes: strongly accumulated (SA or grade I), moderately accumulated (MA or grade II), intermediately accumulated (IA or grade III), and weakly accumulated (WA or grade IV). The results showed that elemental association between Fe, Al, Ni, and As was generally highly correlated with each other in the sampling sites. This may suggest their common biochemical characteristics. Generally, those species containing strong and moderate accumulation in both sites are considered including Vitex negundo, Broussonetia papyrifera, Ulmus pumila, and Rubia cordifolia. At BSF and other industrial sites with a similar ecosystem, strong and moderate accumulation species include Sophora japonica, Ampelopsis aconitifolia var. glabra, Platycladus orientalis, Wikstroemia chamaedaphne, Cleistogenes squarro sa, Grewia biloba, and in BBG, in addition Setaria viridis, Cotinus coggygria, Lespedeza floribunda, Rhamnus parvifolia, Lespedeza tomentosa. Show more

Keywords: Fe, Mn, Al, Zn, Pb, Ni, As, metal accumulation index (MAI)

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 294-300, 2005

Authors: ADELEKE, Olukunle Francis | ZHOU, Rui-min | Zu, Jian-hua | Ekoko, Bakambo Gracien

Article Type: Research Article

Abstract: Electron beam was successfully used for the degradation of 2-chlorophenol (2-CP) and 4-chlorophenol (4-CP) in aqueous solutions in this research. The effect of radiation dose on substrate degradation and dechlorination of solutions with concentration of 50 mg/L was investigated. The effect of initial concentration, pH and presence of oxygen was also investigated. The concentration of 2-CP and 4-CP remaining in solution after irradiation were measured by HPLC. The results showed that increased radiation …dose led to increased degradation of the chlorophenols and increased Cl^- yield. Deaeration was also found to significantly increase the rate of degradation of chlorophenols in water while degradation and dechlorination under alkaline condition was lower than at low to neutral pH. Show more

Keywords: electron beam, monochlorophenols, degradation, deaeration

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 301-304, 2005

Authors: WANG, Xi-fen | ZHOU, Huai-chun

Article Type: Research Article

Abstract: The control of 3-D temperature distribution in a utility boiler furnace is essential for the safe, economic and clean operation of pcfired furnace with multi-burner system. The development of the visualization of 3-D temperature distributions in pc-fired furnaces makes it possible for a new combustion control strategy directly with the fumacs temperature as its goal to improve the control quality for the combustion processes. Studied in this paper is such a new strategy that the whole …furnace is divided into several parts in the vertical direction, and the average temperature and its bias from the center in every cross section can be extracted from the visualization results of the 3-D temperature distributions. In the simulation stage, a computational fluid dynamics (CFD) code served to calculate the 3-D temperature distributions in a furnace, then a linear model was set up to relate the features of the temperature distributions with the input of the combustion processes, such as the flow rates of fuel and air fed into the furnaces through all the burners. The adaptive genetic algorithm was adopted to find the optimal combination of the whole input parameters which ensure to form an optimal 3-D temperature field in the furnace desired for the operation of boiler. Simulation results showed that the strategy could soon find the factors making the temperature distribution apart from the optimal state and give correct adjusting suggestions. Show more

Keywords: tangentially-fired boilers, combustion control, three-dimensional temperature distributions, adaptive genetic algorithm

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 305-308, 2005

Authors: SHI, Ya-juan | LU, Yong-long | ZHANG, Hong | WANG, Tie-yu | XING, Ying

Article Type: Research Article

Abstract: The development of Persistent Organic Pollutants (POPs) control policy in China in the context of international concerns on POPs was reviewed. The aspects of the Chinese POPs control strategies were analyzed, and compared with those of developed counterparts (e.g. US, EU, Japan). Currently, while the legal framework on POPs management, which complies with international guidelines has been established, it should be improved in the areas of special POPs management, risk assessment, the precautionary principle, lifecycle …management and technical support capacity. The analysis of Chinese POPs policy and suggestions for strengthening the sciencebased decision making capacity are not only useful for Chinese decision-makers, but also a case study for developing world and make a great contribution for the global elimination of POPs to make a toxic-free future. Show more

Keywords: Persistent Organic Pollutants (POPs), POPs policy, dangerous chemicals management, pesticides management, Persistent Bioaccumulative Toxic Chemicals (PBTs)

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 309-314, 2005

Authors: AN, Dong | LI, Wei-guang | CUI, Fu-yi | HE, Xin | ZHANG, Jin-song

Article Type: Research Article

Abstract: The removal of disinfection by-products formation potential (DBPFP) in artificially intensified biological activated carbon (IBAC) process which is developed on the basis of traditional ozone granular activated carbon was evaluated. By IBAC removals of 31% and 68% for THMFP and HAAFP were obtained respectively. Under identical conditions, the removals of the same substances were 4% and 32% respectively only by the granular activated carbon (GAC) process. Compared with GAC, the high removal rates of the two …formed potential substances were due to the increasing of bioactivity of the media and the synergistic capabilities of biological degradation cooperating with activated carbon adsorption of organic compounds. A clear linear correlation (R^2 = 0.9562 and R^2 = 0.9007) between DOC HAAFP removal rate and Empty Bed Contact Time(EBCT) of IBAC process was observed, while that between THMFP removal rate and EBCT of GAC was R^2 = 0.9782. In addition certain linear correlations between THMFP, HAAFP and UV_{254} (R^2 = 0.855 and R^2 = 0.7702) were found for the treated water. For IBAC process there are also more advantages such as long backwashing cycle time, low backwashing intensity and prolonging activated carbon lifetime and so on. Show more

Keywords: intensified biological activated carbon (IBAC), by-products formation potential (DBPFP), empty bed contact time, water treatment

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 315-318, 2005

Authors: WANG, Qi-dong | HE, Ke-bin | HUO, Hong | Lents, James

Article Type: Research Article

Abstract: The dynamometer tests with different driving cycles and the real-world tests are presented. Results indicated the pollutants emission factors and fuel consumption factor with ECE15 + EUDC driving cycle usually take the lowest value and with real world driving cycle occur the highest value, and different driving cycles will lead to significantly different vehicle emission factors with the same vehicle. Relative to the ECE15 + EUDC driving cycle, the increasing rate of pollutant emission factors of …CO, NOx and HC are −0.42–2.99, −0.32–0.81 and −0.11–11 with FTP75 testing, 0.11–1.29, − 0.77–0.64 and 0.47–10.50 with Beijing 1997 testing and 0.25–1.83, 0.09–0.75 and − 0.58–1.50 with real world testing. Compared to the carburetor vehicles, the retrofit and MPI + TWC vehicles' pollution emission factors decrease with different degree. The retrofit vehicle (Santana) will reduce 4.44%–58.44% CO, − 4.95%–36.79% NOx, − 32.32%–33.89% HC, and − 9.39%–14.29% fuel consumption, and especially that the MPI + TWC vehicle will decrease CO by 82.48%–91.76%, NOx by 44.87%–92.79%, HC by 90.00%–93.89% and fuel consumption by 5.44%–0.55%. Vehicles can cause pollution at a very high rate when operated in high power modes; however, they may not often operate in these high power modes. In analyzing vehicle emissions, it describes the fraction of time that vehicles operate in various power modes. In Beijing, vehicles spend 90% of their operation in low power modes or decelerating. Show more

Keywords: real-world testing, vehicle emission factors, driving cycle, power modes

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 319-326, 2005

Authors: REN, Hong-chang | LU, Yong-long | LIU, Can | MENG, Qing-hua | SHI, Ya-juan

Article Type: Research Article

Abstract: For improving the environmental quality and ensuring supply of wood and non-timber forest products, many forests have been planted in plain areas of China. Scientists have studied their benefits, almost all of the approaches were based on fixed-point data, and few was considered on the non-efficient factors and temporal scale effects. This paper studies the positive and negative benefits at a large temporal scale, and the effects of plain afforestation on stockbreeding and rural economy. The …benefits of plain afforestation, correlation coefficiency of agroforestry and production factors are analyzed via stochastic frontier modeling in Huanghuaihai Plain Area of China; elastic coefficient of agroforestry, husbandry, farming, and total output of agricultural sector are calculated through adopting partial differential equation. Some conclusions can be drawn that, plain forests have an important effect on the development of plain agriculture. But shelterbelts and small-scale forests have different effect on the development of agricultural economy. Shelterbelts have negative effect on the industries, but small-scale forest has positive effect. On the whole, contribution of forest resource to value of animal husbandry and gross production value of agriculture is positive, and to the value of farming is negative. Show more

Keywords: plain afforestation, agricultural development, agroforestry, plain area of China

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 327-331, 2005

Authors: GUO, Zhao-hui | LIAO, Bo-han | HUANG, Chang-yong

Article Type: Research Article

Abstract: Through a batch experiment, the mobility and speciation of heavy metals (Cd, Cu, Zn) in two acidic forest soils from Hunan Province were studied. The results showed that the release and potential active speciation of Cd, Cu, and Zn in the tested contaminated red soil (CRS) and yellow red soil (CYRS) increased significantly with pH decreasing and ion concentrations increasing of simulated acid rain, and these effects were mainly decided by the pH value of simulated …acid rain. Cd had the highest potential risk on the environment compared with Cu and Zn. Cd existed mainly in exchangeable form in residual CRS and CYRS, Cu in organically bound and Mn-oxide occluded forms, and Zn in mineral forms due to the high background values. Show more

Keywords: batch experiment, heavy metals, mobility, speciation, acid rain

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 332-334, 2005

Authors: WEI, Feng | ZHANG, Jun-ying | ZHENG, Chu-guang

Article Type: Research Article

Abstract: In order to remove efficiently haled-particles emissions from coal combustions, a new way was used to put forward the process of agglomeration and the atomization was produced by the nozzle and then sprayed into the flue before precipitation devices of power station boiler in order to make inhaled-particles agglomerate into bigger particles, which can be easily removed but not change existing running conditions of boiler. According to this idea, a model is set up to study …agglomeration rate and effect forces between fly ash inhaled-particles and atomized agglomerator particles. The developed agglomeration rate was expressed by relative particle number decreasing speed per unit volume. The result showed that viscosity force and flow resistance force give main influences on agglomeration effect of inhaled-particles, while springiness force and gravity have little effect on agglomeration effect of theirs. Factors influencing the agglomeration rate and effect forces are studied, including agglomerator concentration, agglomerator flux and agglomerator density, atomized-particles diameters and inhaled-particles diameter and so on. Show more

Keywords: inhaled particles, agglomerator, effect forces, agglomeration rate

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 335-339, 2005

Authors: DONG, Yu-hong | OUYANG, Zhu | LIU, Shi-liang

Article Type: Research Article

Abstract: The nitrogen transformation in maize soil after application of different organic manure was studied. The nitrogen mineralization in surface soil, NO_3^- -N dynamics and distribution in soil profile, and N_2 O emission were investigated. Eight treatments were laid out randomizing with three replications in 24 plots: maize plantation without fertilizer (CK1), bare soil without maize plantation and fertilization (CK2), swine manure (S1, S2), poultry manure (P1, P2), and cattle manure (C1, …C2). Three manures were applied at two application levels (15 t/hm^2 and 30 t/hm^2 ). The results indicated that NH_4^+ -N in surface soil showed the same temporal pattern without much variation among different treatments. But NO_3^- -N in the same layer exhibited large temporal pattern in all treatments, which was mainly due to its easy eluviations of NO_3^- -N in soil, its transformation to N_2 O and the influence of precipitation. The distribution of NO_3^- -N in the soil profile during maize growing season showed the leaching tendency from surface soil to subsoil, which was different among the treatments. The poultry treatments showed the largest leaching tendency. The study also revealed that the emissions of N_2 O were affected by the application of organic manures in the order of P2 > S2 > C2 > P1 > S1 > C1 > CK1 > CK2. All these results showed that organic manure applications significantly affect nitrogen transformation and distribution in maize soil. Considering N_2 O emission and NO_3^- -N leaching, the management of organic manure in the agriculture needs further studies. Show more

Keywords: organic manure, maize, NH_4^+-N, NO_3^--N, N_2O

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 340-343, 2005

Authors: KANG, Xiao-guang | MA, Qing-bin

Article Type: Research Article

Abstract: Within the global urban system, the statistical relationship between urban eco-environment (UE) and urban competitiveness (UC) (RUEC) is researched. Data showed that there is a statistically inverted-U relationship between UE and UC. Eco-environmental factor is put into the classification of industries, and gets six industrial types by two indexes viz. industries' eco-environmental demand and pressure. The statistical results showed that there is a strong relationship, for new industrial classification, between the changes of …industrial structure and evolvement of UE. The drive mechanism of the evolvement of urban eco-environment, with human demand and global work division was analyzed. The conclusion is that the development stratege, industrial policies of cities, and environmental policies fo cities must be fit with their ranks among the global urban system. At the era of globalization, so far as the environmental policies, their rationality could not be assessed with the level of strictness, but it can enhance cities' competitiveness when they are fit with cities' capabilities to attract and control some sections of the industry's value-chain. None but these kinds of environmental policies can probably enhance the UC. Show more

Keywords: global urban system, urban competitiveness, urban eco-environment, industry structure

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 344-349, 2005

Authors: ZHANG, Jing-chang | LI, Qing | CAO, Wei-liang

Article Type: Research Article

Abstract: A series of TiO_2<FORMULA>-MoO<FORMULA>_3<FORMULA> nano-composite photocatalysts were prepared by supercritical fluid dry method (SCFD) and an impregnation technique with TiCl<FORMULA>_4 and (NH_4)_6 Mo_7 O_{24} ˙4H_2 O as the starting materials. The catalysts were characterized by the means of XRD, TEM and UV-Vis. Methyl orange was used as model compound for the evaluation of their catalytic activities. The results indicated that the photo-catalyst prepared by SCFD had …the advantages of small size (12.84 nm), narrow distribution and good dispersivity. The presence of small amount of Mo in composite catalyst gives rise to the red shift of its absorbance wavelength, decrease of its energy gap and increase of the utility of visible light. Furthermore, higher surface acidity of the photo-catalyst was obtained as the result of the addition of MoO_3 . Compared with pure TiO_2 , the catalytic activity of the TiO_2 -MoO_3 nano-composite photo-catalyst was improved significantly. As the doping concentration of the composite catalysts was controlled at 0.6% (molar percentage), 100% degradation of methyl orange was achieved with in 1.2 h irradiation time. Show more

Keywords: TiO_2, MoO_3, photocatalytic, supercritical fluid dry method

Citation: Journal of Environmental Sciences, vol. 17, no. 2, pp. 350-352, 2005