Journal of Environmental Sciences - Volume 15, issue 1

Authors: Etuk, Sunday E. | Akpabio, Idara O. | Udoh, E.M.

Article Type: Research Article

Abstract: The thermal properties of different clay samples obtained from locations in Akwa Ibom State, Nigeria were investigated and compared, and in order to establish their suitability as building material from energy conservation point of view. The results showed that stoneware clay has the highest solar radiation absorptivity of 22.32 m-1 while kaolin clay has the lowest radiation absoptivity of 14.46 m-1. A model for the prediction of temperature variation with thickness of the samples was developed. Results showed that kaolin would make the best choice for the design of a naturally cooled building.

Keywords: thermal properties, clay, walling material, naturally cooled building

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 65-68, 2003

Authors: Yue, Qin-yan | Gao, Bao-yu | Wang, Bing-jian

Article Type: Research Article

Abstract: The electrokinetic characteristics and coagulation behaviors of polyaluminum silicate chloride (PASiC) and polyaluminum chloride (PAC) were studied and compared by streaming current (SC) measurement and jar test method. The experimental results showed that the interaction between polysilicic acid characterized negative charge and hydrolyzed aluminum species result in a decrease of the charge-neutralizing ability of PAiSC, compared to PAC. The decrease has a close relationship with the basicity (B) and Al/Si molar ratio in PASiC. The less the B value and the Al/Si molar ratio, the lower the charge-neutralizing ability of PASiC is. In contrast, the preparation technique for PASiC affects …the charge-neutralization of PASiC to a smaller extent. In addition, compared with PAC, PASiC may enhance aggregating efficiency and give better coagulating effects. Show more

Keywords: flocculant polyaluminum chloride (PASiC), streaming current (SC), electrokinetic characteristics, coagulation effect

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 69-74, 2003

Authors: Cui, Li-hua | Luo, Shi-ming | Zhu, Xi-zhen | Liu, Ying-hu

Article Type: Research Article

Abstract: Vertical flow constructed wetlands is a typical ecological sanitation system for sewage treatment. The removal rates for COD, BOD5, SS, TN, and TP were 60%, 80%, 74%, 49% and 79%, respectively, when septic tank effluent was treated by vertical flow filter. So the concentration of COD and BOD5 in the treated effluent could meet the quality standard for irrigation water. After that the treated effluent was used for hydroponic cultivation of water spinach and romaine lettuce, the removal efficiencies of the whole system for COD, BOD5, SS, TN and TP were 71.4%, 97.5%, 96.9%, 86.3%, and 87.4%, respectively. And it …could meet the integrated wastewater discharge standard for secondary biological treatment plant. It was found that using treated effluent for hydroponic cultivation of vegetables could reduce the nitrate content in vegetables. The removal rates for total bacteria and coliform index by using vertical flow bed system with cinder substrate were 80%-90% and 85%-96%, respectively. Show more

Keywords: septic tank effluent, vertical-flow, constructed wetlands, vegetable hydroponic

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 75-82, 2003

Authors: Chen, Shi-fu | Cao, Geng-yu

Article Type: Research Article

Abstract: The feasibility of photocatalytic degradation of X3B azo dye by TiO2/beads photocatalyst was studied. The effects of parameters such as the amount of TiO2/beads, airflow, as well as the concentrations of H2O2, Fe3+, Mg2+ and Na+ on the photocatalytic degradation of X3B azo dye were also studied. The results showed that 25 mg/dm3 X3B azo dye can be photocatalytically degraded completely by 30 min illumination with a 375W medium pressure mercury lamp. Adding a small amount of H2O2 or Fe3+, the efficiencies of photocatalytic degradation of X3B azo dye were increased rapidly. The mechanisms of the reaction and the role …of the additives were also investigated. After 120 hours TiO2/beads showed no significant loss of the photocatalytic activity. Show more

Keywords: X3B azo dye, photocatalytic degradation, titanium dioxide, hollow glass microbeads

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 83-87, 2003

Authors: Lu, Guang-hua | Wang, Chao | Yuan, Xing | Zhao, Yuan-hui

Article Type: Research Article

Abstract: The biodegradability of 30 substituted phenols and benzoic acids was determined by BOD technique. The molecular weight (MW), heat of formation (Hf) and the energy of the highest occupied molecular orbital (EHOMO) of the studied compounds were calculated by the quantum chemical method MOPAC6.0-AM1. The quantitative structure-biodegradability relationships (QSBRs) were developed by the linear regression method and neural network approach, respectively. It has been shown that the neural network method is able to provide a superior fit to the training set data and test set data and produce a lower prediction error than the linear regression method.

Keywords: BOD, regression, artificial neural network, prediction

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 88-91, 2003

Authors: Li, Hua | Chen, Wan-ren | Liu, Da-zhuang

Article Type: Research Article

Abstract: A new desulfurizing absorbent for flue gas, i.e., anorganic physical solvent of DMSO (dimethyl sulfoxide) mixed with a relatively small amount of chemical solvent (Mn2+) was studied. Compared with pure physical solvent of DMSO, the purification efficiency of the new absorbent has been much improved. And its absorption and reaction mechanism are discussed.

Keywords: liquid absorption, desulfurization, flue gas

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 92-96, 2003

Authors: Yu, Li-jun | Cao, Guang-yi | Zhu, Xin-jian | Jiang, An-zhong | Tian, Zi-ping

Article Type: Research Article

Abstract: The kinds and the distribution of the coal in China are investigated in this paper. The results indicated that the 80% coalin China is used by the method of the coal gasification. The possibility of utilization and development of the fuel cell powerplant in China is analyzed. A combined cycle generation system is designed. Its net electrical efficiency is about 55%(LHV), which is higher than that of the fire power plant. So it is environmental-friendly and high-efficient generation mode.

Keywords: energy conservation, pollution control, fuel cell, power plant, coal gasification

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 97-101, 2003

Authors: Zhan, Xin-min | Zhao, Xuan | Miyazaki, Akane | Nakano, Yoshio

Article Type: Research Article

Abstract: Lead has caused serious environmental pollution due toits toxicity, accumulation in food chains and persistence innature. In this paper, lead removal from aqueous solutions was investigated using condensed tannin gel adsorbent synthesized froma natural tannin compound. It is found that the adsorption is strongly affected by pH values of aqueous solutions. Within pH range of 3.5-6, when initial lead concentration is 100 mg/L, removal efficiency is more than 90%. Adsorption equilibrium is reached within 150 minutes. The adsorption isotherm fits well with the Langmuir equation, by which the saturated adsorption uptake of 190 mg Pb2+/g dry tannin gel adsorbent is …obtained. By means of thermodynamics analysis, it is revealed that the process is exothermic and the adsorption heat is up to 38.4 kJ/mol. With respect to high efficiency, moderate pH requirement and minimized second pollution, the tannin gel adsorbent exhibits a promising potential in the removal of lead from wastewater. Show more

Keywords: lead removal, Mimosa tannin, synthesis, tannin gel adsorbent

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 102-106, 2003

Authors: Weng, Huan-xin | Weng, Jing-ke | Yong, Wen-bin | Sun, Xiang-wu | Zhong, Hang

Article Type: Research Article

Abstract: To understand the biogeochemical transfer of iodine, the absorbability and bioaccumulation of iodine in tested vegetables (radish, spinach and Chinese cabbage) are examined by applying iodic fertilizer composed of kelp and diatomaceous earth. The experimental results show that when iodine in soil is not excessive, the concentrations of iodine in tested vegetables increase as the content of iodine in soil increases. The absorbability and enrichment degree of iodine in various vegetable and in various parts of the same vegetable are different, which explains that the concentration of iodine in plant is determined by the plant type and by the physiological …action of plant. The patience order of tested vegetables to excessive iodine is Chinese cabbage > spinach > radish. These results have theoretical and practical significance in opening up a new way for ameliorating poor iodine environment with artificial means. Show more

Keywords: iodine, biogeochemical transfer, absorbability, vegetable, IDD

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 107-111, 2003

Authors: Sheng, Xue-bing | Liu, Yun-xia | Sun, Jian-zhong

Article Type: Research Article

Abstract: The studied agriculture-pasture interlacing zone has its specific natural conditions, at which the natural systems areunstable, their self-regulation capability is low and the equilibrium is easily broken, and hence the habitat is fairly vulnerable. During last 20 years the increasing population and livestock, over-reclamation, over-pasturing, over-deforesting, andother intensified negative human activities in the zone resulted in coarsening of surface soil, decrease of organic mater content insoil, reduction of vegetation coverage, variation and degradation of flora structure, and hence in desertization of the land, although average of gales and sandstorms some decreased and the climate tended to be better in the …region. However, the frequent sandstorms occurring in the springs of last and present years has attracted much attention. Investigations confirmed that the main cause for the phenomena is the unreasonable human activities rather than the natural factors. Show more

Keywords: agriculture-pasture interlacing zone, soil, sandstorm, desertization

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 112-115, 2003

Authors: Hong, Li-yu | Hong, Hua-sheng | Chen, Wei-qi | Wang, Xin-hong | Zhang, Luo-ping

Article Type: Research Article

Abstract: The concentrations of Cu, Pb, Zn and Cd in surface sediments from Minjiang Estuary-Mazu and Xiamen-Jinmen sea areas of China were investigated during 1995-1996. The concentration ranges of Cu, Pb, Zn and Cd in the Minjiang Estuary-Mazu sea area were 16.4-37.2, 33.4-69.6, 92.1-128, 0.087-0.336 mg/kg (dry wt.), respectively; those for Xiamen-Jinmen sea area were 11.0-24.5, 36.0-80.3, 77.5-161, 0.135-0.285 mg/kg (dry wt.), respectively. The concentrations and distributions of Cu, Pb, Zn and Cd in surface sediments of Minjiang Estuary-Mazu and Xiamen-Jinmen sea areas were analyzed and evaluated. The results showed that the values of Zn and Pb exceeded those of sediment …quality criteria. The average concentration of Cu in Minjiang Estuary-Mazu sea area was higher than that in Xiamen-Jinmen sea area. The obviously higher concentrations of Cu, Pb, Zn and Cd were found at outlets of Minjiang and Jiulong River. From the estuaries to open sea, the concentrations of Cu, Pb, Zn and Cd had a decreasing trend, and then elevated in the sea areas near Mazu and Jinmen, suggesting that Cu, Pb, Zn, Cd in Minjiang Estuary-Mazu and Xiamen-Jinmen sea areas may come from both the mainland and Taiwan of China. Show more

Keywords: heavy metal, sediment, concentration, distribution, Minjiang Estuary-Mazu and Xiamen-Jinmen sea areas

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 116-122, 2003

Authors: Zhao, Yi | Ma, Shuang-chen | Wang, Xiao-ming | Zhang, Qing

Article Type: Research Article

Abstract: Seawater flue gas desulfurization (Seawater FGD) process has a number of advantages, but the study on mechanism of seawater FGD is little. The effects of absorbing efficiency of SO2 by the constant component and part of trace transition elements in seawater are studied by the experiment. The results indicate that the effect factors of absorption of SO2 by seawater are alkaline, ion intensity, catalysis of Cl- and transition metal ions Fe, Mn. The degree of effect is alkaline > the catalysis of Cl-, Fe2+ and Mn > ion intensity. The mechanisms of catalysis oxidation for S(IV) by Cl, Feand Mnare …discussed. According to the results, some measures can be used to improved the capability of desulfurization. Show more

Keywords: seawater, flue gas desulfurization, catalysis

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 123-128, 2003

Authors: Jin, Fu-jiang | Wang, Hui | Li, Ping

Article Type: Research Article

Abstract: Pulping production process produce large amount of wastewater and pollutant emitted, which has become one of the main pollution sources in pulp and paper industry. To solve this problem, it is necessary to implement cleaner production by using modeling and optimization technology. This paper studies the model and multi-objective genetic algorithms for continuous digester process. A model is established, in which environmental pollution and saving energy factors are considered. A hybrid genetic algorithm based on Pareto stratum-niche count is designed for finding near-Pareto or Pareto optimal solutions in the problem. A new genetic evaluation and selection mechanism is proposed. Using …the real data from a pulp mill shows the results of computer simulation. Through comparing with the practical curve of digester, this method can reduce the pollutant effectively and increase the profit while keeping the pulp quality constant. Show more

Keywords: cleaner production, multi-objective optimization, genetic algorithm, Pareto stratum, concentration of residual alkali, Kamyr continuous digester

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 129-135, 2003

Authors: Li, Xin | Gu, Da-ming | Qi, Jing-yao | Ukita, M. | Zhao, Hong-bin

Article Type: Research Article

Abstract: Water quality within water distribution system may vary with both location and time. Water quality models are used to predict the spatial and temporal variation of water quality throughout water system. A model of residual chlorine decay in water pipe has been developed, given the consumption of chlorine in reactions with chemicals in bulk water, bio-films on pipe wall, in corrosion process, and the mass transport of chlorine from bulk water to pipe wall. Analytical methods of the flow path from water sources to the observed point and the water age of every observed node were proposed. Model is used …to predict the decay of residual chlorine in an actual distribution system. Good agreement between calculated and measured values was obtained. Show more

Keywords: residual chlorine, bulk water, corrosion, bio-film, water quality, water distribution system, flow path, water age

Citation: Journal of Environmental Sciences, vol. 15, no. 1, pp. 136-144, 2003