Alfred Oloo OchiengTamer F. MegahedShinichi Ookawara
21页
查看更多>>摘要： This paper presents a comprehensive review of recent studies in electrical power generation from various thermal-consuming processes. In particular, the paper concentrates on TEG technology in recovering waste heat from industrial applications such as chimneys and automotive engines. Studies conclude that TEGs have a lower conversion efficiency (ranging between 5% and 10%), leading to low power output. Also, they state that most of the available TEGs have low operating temperatures limiting their commercial use. Therefore, an effort is taken to understand the key parameters that influence the performance of a thermoelectric generator. It is shown that a large temperature difference across the module, high heat dissipation from the cold side of the TEG and using thermoelectric materials with a high figure of merit generally improve the performance of the thermoelectric generator system. TEG module's cold-side temperature has a large effect on the power output than the hot-side temperature. Several geometric optimization methods, such as flaps and heat spreaders under natural convection resulted in a 129% and 42% increase in TEG power output, respectively. The survey also shows that forced cooling using side-mounted fans produces 58.6% more power compared to the top-mounted fan on the heat sink. However, optimization in fan selection is required to ensure that the power produced by forced cooling is sufficient to run the fans and output higher than the natural convection cooling case. Several studies also show that most of the commercially available TEG modules made from Bismuth telluride suffer from low operating temperature (maximum of 260℃) and have figure of merit of 1.2 maximum and low conversion efficiency (up to 5%). Recommendations are made to further research alternatives like SiGe alloys, clathrates, skutterudites, and complementary metal-oxide semiconductors with better temperature ranges and figures of merit.
查看更多>>摘要： Shenzhen River (SZR) is a boundary river of two super-large modern cities and has important wetland ecological functions in the estuary, while it suffered unprecedented pollution during the past decades due to the rapid urbanizing of the catchment area. Twelve parameters of heavy metals (HMs), nutrients (N, P, TOC), and physicochemical indexes (pH, EC) of the SZR sediment from 8 typical sites were analyzed to explore their distribution, risk, and sources. The distribution of sediment parameters was closely related to the urban functional structure, basin topography, and anthropogenic control. Heavy metals (HMs) of SZR sediment were in a contamination degree order of Cd > > Cu > Zn > Pb > Ni > Cr, a combined risk of HMs and tremendous organic threat concentrated at the upper and middle reaches in the lower layer. HMs and nutrients in SZR sediments showed strong inner correlations but were limited influenced by physicochemical properties. Factor, clustering, and multiple linear regression analysis were comprehensively applied for the quantitative source apportionment. Industry-related sources and domestic wastewater were the major contamination sources, while the non-point sources like urban surface runoff, natural sources, and solid waste carrying should be paid special attention to considering their maintained increasing risk.
查看更多>>摘要： Treatment of industrial wastewaters with current technologies can be very challenging, due to the presence of toxic and persistent compounds and to unfavorable pH conditions, which exert toxic/inhibitory effects on the biomass. Extractive membrane bioreactor (EMB) is a promising technology capable to overcome these difficulties. The system ensures separation between 'hostile' wastewater and the biomass, allowing the gradual release of contaminants in the bioreactor under a concentration gradient, through an absorptive/diffusive membrane. Depending on thermodynamic affinity, the membrane is permeable only to target compounds, thus ensuring a 'selective' extraction. In this review, earlier PDMS and newest polymeric membrane reactors have been analyzed, highlighting their potentialities and the still open research issues. The effects of biofilm formation, reactor configuration and operative parameters, such as Hydraulic Retention Time and geometric configuration, have been discussed. Despite good results in terms of contaminants removal, these parameters strongly affect reactor performance and further investigations are necessary. Furthermore, data analysis showed that this technology is ready for upscaling and this step is crucial for a full evaluation of the feasibility of a technology that could bring a remarkable improvement for industrial wastewater treatment.
查看更多>>摘要： Reliability of feedstock supply is an important consideration for enhancing the safety and continuous operation of chemical plants. A critical component of the chemical and refining sectors is the extensive pipeline network which transports natural gas and hydrocarbon liquids from producing areas to refineries and chemical plants. Incidents involving spills or releases and shutdowns of those pipeline can occur due to a number of causes including corrosion, equipment malfunction, and excavation damage. These incidents involve economic, environmental, and safety consequences such as the cost of asset damage, lost commodities, cleanup requirement, and operational disruption. In this work, an appropriately developed stochastic framework is presented to determine the disruption impact of pipeline incidents on downstream chemical production. Incident data are statistically analyzed to determine meaningful distributions for incident rates, spill/release quantities, and pipeline shutdown durations. A case study on the production of propylene via three different pathways (crude oil, propane, and natural gas) is presented to illustrate the methodology and underline the variability of the process production impact due to variations in risk occurrence characteristics. Using specific process chemistry and mass balances, more precise risk profiles for the product shortfall and cost of lost sales can be generated.
查看更多>>摘要： Understanding the characteristics of domestic sewage discharge in different rural areas is an important prerequisite for effective sewage treatment. Here, we revealed the spatial variation in the water quantity and quality of rural domestic sewage and its influencing factors in 31 provinces and cities of China, based on a multi-factorial analysis. The results showed that the water quantity of rural domestic sewage discharge generally increased from Northwest to Southeast in China and the water quality had opposite pattern. The water quantity was positively correlated with water resources, gross domestic product, rainfall, and temperature, but negatively correlated with altitude. Water resources, with an influence weight of 25.04% by principal component analysis, had the greatest impact on the spatial variation in water quantity. Differently, gross domestic product, which was directly negatively correlated with ammonium-nitrogen and total phosphorus in structural equation model, was a dominant factor influencing water quality. These findings will help us to better understand the factors of controlling rural domestic sewage discharge at a national scale and to optimize the treatment technology of rural domestic sewage.
查看更多>>摘要： Complex metal contaminated sites are generally more harmful than single metal contaminated sites. Therefore, this study combined experiment and mathematical model to investigate the migration of Pb(II), Ni(II) and Cd(II) in single and multi-metal systems. The data from batch and column experiments were fitted well by Langmuir and nonequilibrium convection-dispersion equation. In the single metal system, the adsorption capacity of metals in soil was Pb> >Cd>Ni. In multi-metal systems, Pb(II), Ni(II) and Cd(II) retention in column decreased by 42.8%, 56.2% and 92.8% respectively due to the competition effect. The competitive effect enhanced the migration of three metals in the column. Ni(II) and Cd(II) showed irregular breakthrough curves, called 'overshooting', under the effect of Pb(II). The phenomenon of overshooting made the outlet concentration C of the column greater than the inlet concentration C0 > (C/C0 > 1), leading to serious potential risks to groundwater. In addition, results from speciation of metals showed that the competition effect and overshooting mainly occurred in exchangeable and carbonate fractions. Understanding the transport of metals in complex contaminated sites is important for risk assessment.
查看更多>>摘要： Carbon black wastewater is a by-product of partial oxidation of natural gas to acetylene and can cause serious pollution to the environment. In this study, the effect of deep bed filtration (microchannel filtration) in the synergistic separation of particulate pollutants and organic pollutants in carbon black wastewater were investigated. The results indicated that the separation efficiency of carbon black particles with a mean diameter of 6.88 urn was 95%- 98%, 95-97%, and 95%- 96% when the filter material was quartz sand + quartz sand, quartz sand + activated, and quartz sand + anthracite, respectively. The solid content of inlet was 300 mg/L and 145 NTU, respectively, and those of the purified effluent were below 15 mg/L and 14 NTU, which meet the first-class B standard of China sewage discharge. The total kinds of organics were reduced from 29 to 2. The separation efficiency of C6-C_(24) all higher than 97%. A 150 m~3/h full-closed treatment process for carbon black wastewater was designed to replace the original open sedimentation tank. The carbon black wastewater could be efficiently purified by this method, the purified carbon black wastewater could be reused, and the carbon black was used to make a filter cake for recycling in rubber without discharge. Finally, the possibility of achieving zero discharge of carbon black wastewater is shown.
查看更多>>摘要： Electronic waste (e-waste) is generated from the discarded electronic products. The generation of e-waste has increased significantly in the recent decades. Globally, the increased rate of e-waste generation is almost 2 metric tonnes (Mt) per year. It is estimated that about 74 Mt of e-waste will be produced in 2030. Therefore, e-waste can be a significant threat to the environment. Toxic metals (e.g., lead, mercury, nickel, and cadmium) are released to the environment from the e-waste and eventually enter into soil, sediment, groundwater, and surface water. The release of toxic metals in the environment causes adverse effects on human health, aquatic animals, and plants. Therefore, the proper management of e-waste is essential and becomes a major concern in the world. In this regard, this review provides a comprehensive summary of the occurrence, fate, and remediation of metals generated from e-waste. The literature survey revealed that household electrical appliances are the primary source of e-waste, comprising approximately 50% of the overall production of e-waste. Among different remediation technologies, the combination of biological, physical, and chemical processes shows relatively high removal efficiency; and they possess multiple advantages over other remediation technologies. Finally, this review also includes future outlook on e-waste management and remediation technologies.
查看更多>>摘要： Natural ligands are the naturally existing chemicals that are extracted from plants and animals without further modification. For the reason that of their biotic and natural invention, these supplies can be treated as green and sustainable replacements for traditional ligands as they are fairly harmless, non-bioaccumulative and biodegradable. Currently, the growing demands of green chemistry and sustainable development inspire the growth and use of these materials and their chemically modified derivatives. Literature search advises that these materials possess widespread of biological and industrial applications. In the present review, coordination bonding ability of some main series of natural ligands including amino acids, proteins, carbohydrates, polyphenols, flavonoids, fatty acids, oleochemicals, purines and pyrimidines, drugs and phytochemicals in correlation with their corrosion protection effectiveness and with possibility of other uses is reviewed, described and proposed. Herein, the advantages of natural ligands and disadvantages of traditional ligands along with future perspective and research gap is described. Obviously, natural ligands contain many electron rich sites in their molecular structure that help them in binding with metal surface effectively. The natural ligands generally form chelating complexes with the metal atoms or ions. Because of their complex formation ability, these ecofriendly ligands can also be used to replaced traditional toxic ligands being used for other applications such as metal decontamination, ion exchange, wastewater and industrial influents treatments.
查看更多>>摘要： Phthalates have been frequently used in various clothing as plasticizers. However, little information is available on phthalates in the environmental matrices in clothing processing sites. This study investigated the phthalates in the soil and road dust in a large processing trade center of children's clothing in China based on the characteristics of human activities and regional environment. The total concentrations of 13 phthalates were in the range of 219-15,952 and 1104-18,628 ng/g, respectively. We did not find extremely high concentrations of phthalates, and our reported concentrations were moderate in comparison with those reported in other areas. Bis(2-ethylhexyl)phthalate was the dominant congener, representing medians of 64.3% and 77.4% of the total phthalate concentrations in the soils and road dust, respectively. Source assessment suggested that the phthalates were likely mainly from the processing process of clothing, and some may have been originated from the use of family products. The health risk assessment results showed that the risks from phthalates in the soils and road dust were generally low. However, more research is required to investigate the phthalate contaminations and the associated risks due to the lack of relevant information in textile industrial areas.
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