Journal of Environmental Sciences - Volume 18, issue 1

Authors: JIANG, Yan-li | LIU, Hui-ling | WANG, Qun-hui | JIANG, Zhao-hua

Article Type: Research Article

Abstract: A new method of determining the cumulate concentration of hydroxyl radicals in the TiO_2 /Ti photoelectrocatalytic (PEC) oxidation system was established by o-phenanthroline-Fe(II)(Fe(phen)_3^{2+} ) spectrophotometry and using anion exchange membrane. Fe (phen)_3^{2+} can be oxidized to o-phenanthroline-Fe(III)(Fe(phen)_3^{3+} ) by strong oxidization of hydroxyl radicals (·OH). Then the cumulate concentration of hydroxyl radicals can be calculated through determining the change of the Fe(phen)_3^{3+} …absorbency at 509 nm. In addition, the research results showed the production rate of hydroxyl radicals was affected obviously by pH of solution, the cumulate concentration of hydroxyl radicals was the largest at nearby the initial pH 6.3 (isoelectric point), and the change direction of pH after illumination tended to nearby isoelectric point. Show more

Keywords: TiO_2/Ti catalyst, photoelectrocatalysis, o-phenanthroline-Fe, hydroxyl radical, anion exchange membrane

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 158-161, 2006

Authors: WANG, Ying-hong | WANG, Yue-si | SUN, Yang | XU, Zhong-jun | LIU, Guang-ren

Article Type: Research Article

Abstract: Combining improved injector, gas line and valve-driving modules, a GC equipped with FID and ECD, could simultaneously measure CH_4 , CO_2 and N_2 O in an air sample within 4 min. Test results showed that the system has high sensitivity, resolution and precision; the linear response range of the system meets the requirement of in situ flux measurements. Thus, the system is suitable for monitoring fluxes of main greenhouse gases in terrestrial …ecosystem since it is easy to use, efficacious, stable and reliable to collect data. Show more

Keywords: GC, valve, emission of greenhouse gases, ecosystem

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 162-169, 2006

Authors: WU, Xiao-qin | WU, Zhong-biao

Article Type: Research Article

Abstract: A novel utilization way of the sludge from wet calcium-based flue gas desulfurization (FGD) processes has been developed in this paper. This study focused on the conversion of the FGD gypsum into α-hemihydrate calcium sulfate by a hydrothermal salt solution method at atmospheric pressure. Experimental study has been carried out in a batch reactor. Qualitative and quantitative analyses were made by DSC/TG thermal analysis, SEM, XRD, metalloscope and chemical analysis. The experimental …results showed that the modification of FGD gypsum was controlled by the dissolution and recrystallization mechanisms. With the introduction of FGD gypsum the salt solution was supersaturated, then crystal nucleus of α-hemihydrate calcium sulfate were produced in the solution. With the submicroscopic structure of FGD gypsum crystal changed, the crystal nucleus grew up into α-hemihydrate calcium sulfate crystals. Thus, the modification of FGD gypsum was fulfilled. Show more

Keywords: FGD gypsum, modification, hydrothermal mixed salt solution, atmospheric pressure

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 170-175, 2006

Authors: HE, Pin-jing | QU, Xian | SHAO, Li-ming | LEE, Duu-jong

Article Type: Research Article

Abstract: Landfill is the major disposal route of municipal solid waste (MSW) in most Asian countries. Leachate from landfill presents a strong wastewater that needs intensive treatment before discharge. Direct recycling was proposed as an effective alternative for leachate treatment by taking the landfill as a bioreactor. This process was proved not only considerably reducing the pollution potential of leachate, but also enhancing organic degradation in the landfill. However, as this paper shows, although direct leachate recycling …was effective in landfilled MSW with low food waste fraction (3.5%, w/w), it failed in MSW containing 54% food waste, as normally noted in Asian countries. The initial acid stuck would inhibit methanogenesis to build up, hence strong leachate was yielded from landfill to threaten the quality of receiving water body. We demonstrated the feasibility to use an assisted bioreactor landfill, with a well-decomposed refuse layer as ex-situ anaerobic digester to reducing COD loading in leachate. By doing so, the refuse in simulated landfill column (2.3 m high) could be stabilized in 30 weeks while the COD in leachate reduced by 95% (61000 mg/L to 3000 mg/L). Meanwhile, the biogas production was considerably enhanced, signaling by the much greater amount and much higher methane content in the biogas. Show more

Keywords: bioreactor, landfill, leachate recycling, organics, enhancement, leachate, pretreatment

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 176-179, 2006

Authors: YANG, Shi-ying | LOU, Li-ping | WU, Xiao-na | CHEN, Ying-xu

Article Type: Research Article

Abstract: For TiO_2 heterogeneous reaction, the reaction site and the detailed mechanism are interesting and controversy topics. In this paper, effects of surface fluorination of TiO_2 on the photocatalytic degradation of an azo dye, Orange G(OG) under UV or visible light irradiation were investigated, and the possible reaction site and mechanism were elucidated. The adsorption of OG on TiO_2 was nearly inhibited by fluoride but its UV light induced photodegradation rate …was greatly increased by a factor of about 2.7, which was due to the more generated free hydroxyl radicals. It supported the views that fluoride could desorb the oxidant species from surface and that the reaction sites could move to the bulk solution. In TiO_2 /Vis system, the observed inhibition effects of fluorination could be interpreted by the competitive adsorption, which provided additional evidences that the visible light sensitized photodegradation of dye pollutants on the catalyst surface. Show more

Keywords: photocatalytic degradation, mechanism, adsorption, fluorination, dye pollutants

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 180-183, 2006

Authors: SULTAN, Khawar | DOWLING, Kim

Article Type: Research Article

Abstract: This paper reports on the major cations (Ca, Mg, Na and K) and arsenic (As) compositions of surface waters collected from major creeks, rivers and lakes in Central Victoria (Australia). The surface waters were found to be neutral to alkaline (pH 6.7–9.4), oxidised (average redox potential (Eh) about 130 mV) and showed variable concentrations of dissolved ions (EC, about 51–4386μS/cm). The concen- trations of dissolved major cations in surface waters were found to be in the …order of Na>>Mg>Ca>K and in soils the contents of metals followed an order of abundance as: Ca>Mg>>K>Na. While Na was the least abundant in soils, it registered the highest dissolved cation in surface waters. Of the four major cations, the average concentration ofNa (98.7 mg/L) was attributed to the weathering of feldspars and atmospheric input. Relatively highly dissolved concentrations of Na and Mg compared with the world average values of rivers reflected the weathering of rock and soil minerals within the catchments. The As soil level is naturally high(linked to lithology) as reflected by high background soil values and mining operations are also considered to be a contributory factor. Under relatively alkaline-oxidative conditions low mobility of dissolved As (average about 7.9μg/L) was observed in most of the surface waters with a few higher values (>15 μg/L) around a sewage disposal site and mine tailings. Arsenic in soils is slowly released into water under alkaline and/or lower Eh conditions. The efficient sink of Fe, Al and Mn oxides acts as a barrier against the As release under near neutral-oxidising conditions. High As content (average about 28.3 mg/kg) in soils was found to be associated with Fe-hydroxides as revealed by XRD and SEM analysis. The dissolved As concentration was found to be below the recommended maximum levels for recreational water in all surface waters (lakes and rivers) in the study area. Catchment lithology exerted the fundamental control on surface water chemistry. Sites impacted by mining waste dumps showed a decline in water quality. Show more

Keywords: surface water, major cations, arsenic, soil, Australia

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 184-192, 2006

Authors: Lee, Jae-Wook | Kwon, Tae-Ouk | Thiruvenkatachari, Ramesh | Moon, Il-Shik

Article Type: Research Article

Abstract: This study evaluates the adsorption ability of bisphenol A (BPA) on titanium dioxide (TiO_2 ) and its effect on the photocatalysis by advanced oxidation process using UV radiation and TiO_2 photocatalyst. Degradation of BPA was also evaluated for the system without adsorption prior to photocatalytic reaction. The separation of TiO_2 from BPA solution treated by pilot-scale photocatalytic reactor (capacity 0.16 m^3 ) was studied using submerged …ultrafiltration (UF) membrane. It was found that although adsorption capacity of BPA was not high, adsorption played an important role in improving the efficiency ofphotocatalysis. On the other hand, during the separation of TiO_2 particles from aqueous suspension, the permeate flux of the membrane was strongly affected by transmembrane pressure and TiO_2 dose. The permeate turbidity was decreased below 1 NTU. Show more

Keywords: bisphenol A, TiO_2, adsorption, membrane, photocatalysis

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 193-200, 2006

Authors: HUANG, Can | LI, Ji | KANG, Wen-li | TANG, Xin-yan

Article Type: Research Article

Abstract: Manure odor, which results in the increasing complaints and lawsuits, has increased the tension among swine producers and surrounding residents. The effects of Lactobacillus plantarum and different rates of soluble carbohydrates additions to swine manure on odorous compounds, chemical compounds and indigenous flora were evaluated. Additions were calculated on dried manure weight basis. Variables monitored included ammonia (NH_3 ), hydrogen sulfide (H_2 S), odor offensiveness, pH, ammonium nitrogen(NH_4^+ -N), …volatile fatty acids (VFAs), urease and indigenous flora. The results indicated that the combination of L. plantarum and soluble carbohydrates dramatically reduced manure pH. Lower pH resulted in the reduction of NH_3 volatilization (34.6%–92.4%, P<0.01), the increases of H_2 S (P< 0.05) and NH_4^+ -N (5.3%–17.5%, P<0.05). In addition, L. plantarum and soluble carbohydrates additions significantly reduced odor offensiveness, those VFAs related to malodor indicators(valeric acids, 12.3%–47.7%, P<0.05; iso-valeric, 3.5%–23.8%) and the main microorganisms responsible for odor production, with the number of Eubacteria in swine manure reducing by 4.9%, 11.6%, 17.4%, 34.1% and 32.2% respectively. Show more

Keywords: Lactobacillus plantarum, soluble carbohydrates, swine manure, odorous compounds, indigenous flora

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 201-206, 2006

Article Type: Other

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 207-207, 2006