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Environmental concerns from global warming and climate change demand carbon dioxide separation from post-combustion gases. Important parameters are involved in choosing the suitable solvent for carbon dioxide separation, including the reaction rate of carbon dioxide and the solvent. In this paper, the kinetics of carbon dioxide (CO2) absorption in aqueous solutions of Monoethanolamine (MEA) + 1,3-Diaminopropane (DAP), a diamine containing two primary amino group, was developed. The measurements were performed in a stirred cell with a horizontal gas-liquid interface in the temperature range of 313.15–333.15 K and aqueous solutions of 10 wt% MEA + 5 wt% DAP and 12.5 wt% MEA + 2.5 wt% DAP. Experiments were conducted in an isothermal batch reactor with a horizontal gas-liquid interface under pseudo-first-order conditions, enabling the determination of the overall kinetic rate constant from the pressure drop method. Second-order reaction rate constants of CO2 absorption in amine solutions were estimated using the calculated initial absorption rate. It was found that the rate constants in MEA+ DAP solutions were greater than in MEA solutions which means that DAP increases the reaction rate. [ABSTRACT FROM AUTHOR]

Abstract Many cities are moving towards increased use of recycled water to meet water demand due to freshwater scarcity, population growth, urbanisation and climate change. Water recycling requires substantial energy. Water utilities are facing serious challenges providing cost-effective and reliable water services under rising energy cost. Energy is further linked with global climate change through carbon intensive Greenhouse Gases (GHGs) emissions. However, few studies have attempted to understand the energy use of water recycling systems and how energy intensity of those systems varies with scale and technology. In this paper, we undertook a comprehensive and systematic literature and data review to understand the energy intensity of water recycling systems. We used four "cases": (1) Centralised Potable (2) Centralised Non-Potable, (3) Decentralised Potable and (4) Decentralised Non-Potable systems to structure our work. Our analysis demonstrates how energy intensity of water recycling systems decreases with increasing size for a wide range of scale and for different treatment technologies. The treatment energy intensity for centralised systems having capacity less than 5 MLD varies from 0.48 to 2.0 kWh/kL for non-potable and 0.75 to 2.0 kWh/k for potable; for capacities between 5 and 200 MLD varies from 0.2 to 0.9 kWh/kL for potable and from 0.25 to 0.75 kWh/kL for non-potable; and for any capacity greater than 200 MLD, the treatment energy intensity is less than 0.8 kWh/kL for potable and 0.55 kWh/kL for non-potable systems. But current centralised water recycling systems have a treatment energy intensity from 0.65 to 1.4 kWh/kL for Potable for capacity from 21 to 378 MLD and from 0.6 to 1.0 kWh/kL for non-potable systems for 6 to 350 MLD. In the case of decentralised systems, smaller systems consume higher energy than centralised systems but larger decentralised Systems (mid-size) have lower energy intensity. Though the treatment energy intensity of a centralised system is low, the reuse of treated water for non-potable water requires a dual pipe system which involves a good amount of pumping energy due to the long distance between the treatment plant and the users. Pumping energy, in this case, can vary from 0.19 to 1.43 kWh/kL. The selected treatment technology and train have also influence on the energy use. The present trend of water recycling is to produce high-quality recycled water for all non-potable reuse using Advanced Water Treatment but all non-potable water uses do not necessarily require such high quality water. Little attention has been given to introducing 'fit for purpose' water reuse using appropriate technologies and larger decentralised (distributed) water recycling systems that have the potential to reduce energy intensity for cost-effective urban water services. [ABSTRACT FROM AUTHOR]

A flow duration curve (FDC) is widely used for predicting water supply, hydropower, environmental flow, sediment load, and pollutant load. Among different methods of constructing an FDC, the entropy-based method, developed recently, is appealing because of its several desirable characteristics, such as simplicity, flexibility, and statistical basis. This method contains a parameter, called entropy parameter M, which constitutes the basis for constructing the FDC. Since M is related to the ratio of the average streamflow to the maximum streamflow which, in turn, is related to the drainage area, it may be possible to determine M a priori and construct an FDC for ungauged basins. This paper, therefore, analyzed the characteristics of M in both space and time using streamflow data from 73 gauging stations in the Brazos River basin, Texas, USA. Results showed that the M values were impacted by reservoir operation and possibly climate change. The values were fluctuating, but relatively stable, after the operation of the reservoirs. Parameter M was found to change inversely with the ratio of average streamflow to the maximum streamflow. When there was an extreme event, there occurred a jump in the M value. Further, spatially, M had a larger value if the drainage area was small. [ABSTRACT FROM AUTHOR]

Abstract: Increased emission of green house gases to the atmosphere due to rapid revolution of industry is potential threat for climate change. Gas scrubbing using aqueous amine solutions is one of the most promising retrofit options for post combustion carbon dioxide capture today. This is conventionally done in spray tower, bubble column and packed column. In the invited paper, a novel contacting device has been proposed for improved chemisorption of CO2. It is based on the absorption of CO2 during its rise as axisymmetric bullet shaped Taylor bubbles through millichannel. Investigations have been made to understand the influence of DEA concentration, inlet gas composition and pipe diameter on percent absorption of CO2 and CO2 loading. The experimental results have shown that percent CO2 removal and CO2 loading increases while absorption rate decreases with decrease of pipe diameter. This information can be exploited for optimizing the input parameters to maximize efficiency of carbon dioxide removal. The present device is expected to be a starting point for the development of slug flow millireactors capable of continuous and enhanced CO2 absorption. [Copyright &y& Elsevier]

A gas chromatography-mass spectrometry method has been proposed for the determination of low-level mutagenic and carcinogenic nitrosamines in particulate matter. The method includes the collection of particulate matters (PM and PM) using a dichotomous Partisol 2025 sampler and extraction of the compounds from aqueous solution with dichloromethane/2-propanol after sonication with a slightly basic water solution prior to their GC-MS analysis in electron impact mode. The obtained recoveries of nitrosamines ranged from 92.4 to 99.2 %, and the precision of this method, as indicated by the relative standard deviations, was within the range of 0.95-2.46 %. The detection limits obtained from calculations using the GC-MS results based on S/N = 3 were found within the range from 4 to 22 pg/m. The predominant nitrosamines determined in particulate matter were N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodibutylamine and N-nitrosomorpholine. Furthermore, N-mono- and dinitrosopiperazine and N-nitrosoethylbutylamine were also determined. N-dinitrosopiperazine was detected in PM samples at the highest concentrations of up to 22.85 ng/m and in PM samples at concentrations up to 7.60 ng/m in winter, whereas it was found in PM samples up to 5.15 ng/m and in PM samples up to 3.12 ng/m in summer. The total concentrations of nitrosamines were up to 161.4 ng/m in fine and 53.90 ng/m in coarse fractions in winter, whereas in summer were up to 35.24 and 12.60 ng/m, respectively. The concentration levels of nitrosamines fluctuated significantly within a year, with higher means and peak concentrations in the winter compared to that in the summertime. The seasonal variations of particle-associated nitrosamine concentrations were investigated together with their relationships with meteorological parameters using Pearson's correlation analysis in the winter and summer periods. Analysis of variance was used to determine which concentrations of nitrosamines were statistically different from one another and, together with meteorological parameters and discriminant analysis, was used to classify the particle samples by particle size according to seasons. The classification results of the particle samples in different seasons were very satisfactory, allowing 99.5 % of cases to be correctly grouped. [ABSTRACT FROM AUTHOR]

Due to its significant ecological and climate consequences, atmospheric nitrogen (N) deposition is a growing global concern, especially in the severely N-polluted regions such as the Pearl River Delta (PRD) region of southern China. One-year measurements of reactive N species, including ammonium nitrogen (NH4+ -N), nitrate nitrogen (NO3--N) and total organic nitrogen (ON) in dry and wet deposition, were conducted using an automated wet-dry sampler incorporated with a DDAS (dry deposition on aqueous surface) sampling device at Dinghushan (DHS), a natural forest site in the northwest of PRD and at Hengmen (HM), an estuary site in the south of PRD during 2006-2007. Total deposition fluxes of N at DHS and HM were up to 48.2 and 37.8 kg ha-1 yr-1, respectively, with most of the deposition occurring in the rainy season. Wet deposition was the dominant form, contributing 65-70% to the total deposition. NH4+-N was the largest contributor to the total N deposition at DHS (47%) due to significant influence of agriculture emissions. ON was the most important N component at HM (41%), which is probably attributed to the marine sources. However, NO3--N deposition is increasing rapidly recently and is expected to be more important in the near future. The current N deposition level in PRD is much higher than those in Europe and North America. Great challenges exist in reducing reactive N emission in this region. Thus, a scenario of rising N deposition in PRD in the near future cannot be ruled out. The environmental consequences due to elevated N deposition should therefore be paid more attention in the future. [ABSTRACT FROM AUTHOR]