Solvent Degradation Research Articles

Core–shell structured electrospun biomimetic composite nanofibers of calcium lactate/nylon-6 for tissue engineering

In this work, core-shell structured nylon-6/lactic acid (LA) nanofibers have been produced via single-spinneret electrospinning from the simple blending of LA and nylon-6 solution. The low evaporation rate and plasticizer property of LA was found to be responsible for the formation of point-bonded morphology whereas solvent degradation of nylon-6 with complex phase separation mechanism could give spider-wave-like architecture of the mat and core–shell structure of the composite fibers. The core–shell nanostructure and existence of LA on the shell layer of the fiber were confirmed by TEM and XPS analysis. These fibers were further treated with calcium base to convert surface LA into calcium lactate (CL) which could increase the biocompatibility of composite mat. The SBF incubation test not only confirmed the nucleation capacity of CL to accelerate the deposition of calcium compound on the surface of nanofibers but also facileated the formation of hollow calcium phosphate particles at biomimetic conditions. The adhesion, viability and proliferation properties of osteoblast cells on the composite nanofibers were analyzed by in vitro cell compatibility test. This study demonstrated the non-cytotoxic behavior and good proliferation capacity of calcium lactate/nylon-6 (CL/nylon-6) composite mat. Therefore, the novel nanofibrous composite mat may become a potential candidate for bone tissue engineering.

Biodegradation of Dichloromethane Along with Other VOCs from Pharmaceutical Wastewater

The present study dealt with the interaction of dichloromethane (DCM) with other non-chlorinated organic solvents such as methanol, acetone, toluene, and benzene, which are commonly present in the pharmaceutical wastewater, during biodegradation by mixed bacterial consortium. Non-chlorinated solvents were easily degradable even at an initial concentration of 1,000mg/L, whereas only 20mg/L of DCM was degraded when used as sole carbon source. The Monod Inhibition model appears to simulate the single pollutant biodegradation kinetics satisfactorily. In dual substrate systems, low concentrations (100mg/L) of non-chlorinated solvents did not interfere with the DCM degradation. Non-interaction sum kinetics model was able to simulate the experimental results well in this case. However, high concentrations of non-chlorinated solvents (1,000mg/L) affected the DCM degradation significantly. There was severe competition between the chlorinated and the non-chlorinated solvents. In this case, competitive inhibition model predicted the experimental results better compared to co-metabolism model. In multiple substrate system also, presence of DCM prolonged the degradation of the other non-chlorinated solvents. However, the presence of non-chlorinated compounds accelerated the degradation of DCM. The results of the present study may be helpful in optimal design of biological systems treating mixed pollutants.

Spectral and photophysical properties of zinc(II) complexes with alkylsubstituted derivatives of dipyrrolylmethene and their resistance to protolytic dissociation and photochemical destruction

The spectral and photophysical properties of zinc(II) complexes with alkylsubstituted derivatives of dipyrrolylmethene, along with the kinetics of their protolytic dissociation and photochemical degradation in organic solvents of different natures, are studied by means of electronic absorption and fluorescence spec� troscopy. It is found that protic solvents have the strongest effect on absorption spectra, while electron donors affect fluorescence spectra due to differences in the mechanisms of solvation for the ground and excited states of molecules. It is shown that the reaction product of the protolytic dissociation of complexes in benzene solutions of acetic acid is a protonated form of ligand. The observable and genuine rate constants of dissoci� ation reactions are determined and activation parameters are calculated. A kinetic model of the process is proposed, and the regularities of the effect the nature of ligand has on the kinetics of dissociation are estab� lished. The photochemical degradation of compounds proceeds on monopyrrole products, the photolysis rate falls as the a degree of alkylation increases, and the nature of the substituent in the β�position of the ligand's pyrrole ring has a greater effect on the stability of a compound.

A new test rig for studies of degradation of CO2 absorption solvents at process conditions; comparison of test rig results and pilot plant data for degradation of MEA

SINTEF Materials and Chemistry has recently designed an advanced laboratory test rig for studies of solvent degradation. This solvent degradation test rig (SDR) emulates the process conditions observed in an absorber/stripper configuration designed for CO2 capture. Aqueous solvent is degraded by cycling in a combined absorber and stripper setup with realistic temperatures and CO2 loadings of the solvent in addition to a defined synthetic flue gas mixture. A 14 week test campaign with degradation of 30wt.% 2-ethanolamine (MEA) was performed in the rig. Comparison between group methodology and specific nitrosamine analysis of the solvent showed that 42% of the nitrosamines were unidentified species. This indicates that many of the MEA degradation products are likely precursors for nitrosamine formation. Two nitrosamines were identified in the solvent; nitrosodiethanolamine (NDELA) and the nitrosamine of the degradation product N-(2-hydroxyethyl)-glycine (HEGly): nitroso-(2-hydroxyethyl)-glycine (NHEGly). 56% of the total nitrosamine was identified as NHEGly, while 2% was NDELA. Nitrosodimethylamine (NDMA) was detected in the absorber gas emission, but was below the quantification limit in the solvent. Results indicate that the degradation of nitrosamines and nitramine in the solvent is highly temperature dependent, and that the levels of total nitrosamines and MEA-nitramine are significantly reduced by elevated stripper temperature. The results show that the SDR results give a realistic picture on the solvent degradation to be expected in a real CO2 capture plant; degradation products formed in the SDR MEA solvent reflects those previously found in pilot plant studies. This demonstrates how the SDR enables bench-scale studies of solvent process degradation previously only available from pilot plant studies. SDR results should provide valuable input to health and environmental risk evaluations for different solvent systems for CO2 capture.

Application of Free Piston Stirling Cooler (SC) on CO2 Capture Process

CO2 emission from large point sources (such as coal-fired power plant, cement and steel industry) has attracted a wide attention. During the mature available capture techniques, amine scrubbing approach has been utilized as the most successful one. Nevertheless, the energy penalty of regeneration and degradation of solvents are the main bottlenecks that limit the improvement of the capture efficiency. In this study, a novel application of free piston Stirling cooler (SC) on cryogenic CO2 capture process has been described. In the developed system, the CO2 in the gas stream can be captured in solid form under the cryogenic condition, and frosted on the cold head of SC. In order to avoid the adverse influence of frost layer, a scrapper is added beside the cold head of SC to scrap the deposited CO2 timely. Furthermore, the fallen CO2 crystals is gathered and preserved for further utilization. Compared to other cryogenic sources, the advantage of SC are high efficiency, environmental friendly, safe and convenient. The aim of this paper is to evaluate the properties of the novel system and implement a brief comparison of performance with other cryogenic method.

Oxidative Degradation of Aqueous Amine Solutions of MEA, AMP, MDEA, Pz: A Review

Alkanolamine based post-combustion capture processes (PCC) are currently the most attractive tech- nologies for CO2 capture. Solvents are degraded in this service by flue gas components, for example oxygen. Solvent degradation can be classified into two reaction types: 1) amine oxidative degradation through a) autoxidation pathways, b) oxidation in the presence of metal ions and 2) thermal degradation including reactions in the presence of CO2. This study represents a literature survey of oxidative degradation (reaction type 1a) of 2-Amino-1-ethanol (MEA), 2-Amino-2-methyl-1-propanol (AMP), N,N-Bis(2-hydroxyethyl)methyl-amine (MDEA), and Piperazine (Pz). Thermal degradation products (reaction type 2) are included where appropriate in order to contribute to a more complete degradation overview of these compounds.

Chemical Characterization of MEA Degradation in PCC pilot plants operating in Australia

An important step towards commercial scale post-combustion CO2 capture from coal-fired power stations is understanding solvent degradation. Laboratory scale trials have identified three main solvent degradation pathways for 30% MEA: oxidative degradation, carbamate polymerization and formation of heat stable salts. This paper probes the semi-volatile organic compounds produced from a single batch of 30% MEA which was used to capture CO2 from a black coal-fired power station (Tarong, Queensland, Australia) for approximately 700hours, followed by 500hours at the brown coal-fired power station (Loy Yang, Victoria, Australia). Comparisons are made between the compounds identified in this aged solvent system with MEA degradation reactions described in literature.Most of semi-volatile compounds tentatively identified by GC/MS have previously been reported in laboratory scale degradation trials. Our preliminary results show low levels of degradation products were present in samples after its use in the pilot plant at Tarong (black coal) and consequent 13 months storage, but much higher concentrations were later found in the same solvent during its at use in the pilot plant at Loy Yang Power (brown coal). Further work includes identifying the cause of poor GC/MS repeatability and investigating the relative rates of reactions described in literature. The impact of inorganic anions and dissolved metals on MEA degradation will also be explored.

Babcock & Wilcox Power Generation Group, Inc.’s RSAT™ Process and Field Demonstration of the OptiCap™ Advanced Solvent at the US-DOE's National Carbon Capture Center

Southern Company manages and operates the U.S. Department of Energy's National Carbon Capture Center (NCCC), a focal point of national efforts to develop advanced technologies to reduce greenhouse gas emissions from coal-based power generation. The center, located in Alabama, works with scientists and technology developers from government, industry and universities who are creating the next generation of carbon capture technologies.In the fall of 2011, Babcock & Wilcox Power Generation Group, Inc. (B&W PGG) conducted a three-month test campaign at the NCCC to develop further commercially viable methods of reducing carbon dioxide (CO2) emissions from coal-fired power plants. The company tested its regenerable solvent absorption technology (RSAT™) process using its OptiCap™ advanced solvent.This paper will provide general descriptions of results in the areas of regeneration energy, solvent degradation and corrosion, as well as non-quantitative results such as lessons learned and operating experience for a post-combustion carbon capture (PCC) pilot plant in a coal-fired utility power plant.

CCPilot100+ Operating Experience and Test Results

Doosan Power Systems are developing competitive Post Combustion CO2 Capture (PCC) technologies for application on coal- and natural gas-fired power plants for commercialisation by 2020.The paper presents an overview of the UK's largest post combustion CO2 capture plant on a coal fired power station, the CCPilot100+, giving an insight into the design and construction processes, operating experience gained during commissioning and a presentation of preliminary results from the first period of testing.Doosan Power Systems completed commissioning the CCPilot100+ plant at SSE's Ferrybridge Power Station in West Yorkshire in March 2012. The 100 t CO2/day (15MWt, 5MWe equivalent) CCPilot100+ PCC pilot plant is the first of its size to be integrated into a live power plant in the UK and uses Doosan Power Systems’ technology. It is designed to demonstrate scale-up of the PCC process and provides a stepping stone from process characterisation on Doosan Power Systems’ 1 t CO2/day (160kWt) Emissions Reduction Test Facility (ERTF) to commercial-scale (150MWe plus) plant. The experience gained during the development and operation of the ERTF PCC pilot plant has been used in both the CCPilot100+ plant design and test programme development.The project is co-funded by the project partners: SSE, Vattenfall AB, the Technology Strategy Board (TSB), the Department of Energy and Climate Change (DECC), The Northern Way and Doosan Power Systems, who were also responsible for the design and EPC project. In addition to the partners, four universities are undertaking associated research as part of the project and there is a training programme for future CCS engineers on a ‘live’ plant, creating a valuable resource for future developments.A two year test programme started in the first quarter of 2012. The test programme and long-term operation of the CCPilot100+ aim to optimise the PCC process and provide the data to develop and validate performance models. The test programme will demonstrate the capability of the process over the range of operating conditions that exist in power plant resulting from modern day electrical demand. The test programme will also assess and optimise, where possible, the performance of solvents for regeneration steam consumption, solvent degradation and materials compatibility.Auxiliary power requirements, which add to power plant parasitic losses, will be assessed and, by working with the supply chain, more efficient methods of operation can be considered and developed.Benchmark performance on 30% w/w monoethanolamine (MEA) solvent is being established first and will be followed by extensive parametric and long-term performance testing using the RS2TM designer solvent. Optimisation and long-term testing of a next generation advanced solvent will also be conducted following the RS2 TM testing phase. The testing and verification programmes at both the CCPilot100+ and the ERTF will be used to substantiate the scalability of Doosan Power Systems’ PCC technology under real operating conditions.

EnBW's Post-Combustion Capture Pilot Plant at Heilbronn–Results of the First Year's Testing Programme

The EnBW post-combustion capture pilot plant at Heilbronn in Germany was built in 2010 and commissioned in March 2011. The pilot plant is designed to capture 7.2 tons of CO2 per day from a flue gas slipstream taken downstream the FGD of the power plant. For the construction of the pilot plant a partitioned material concept has been realized applying both stainless steel and plastics. During a benchmark campaign with 30wt. % MEA it was found that the minimum specific reboiler duty is less than 3.4 GJ/t CO2 at a liquid-to-gas ratio of 2.7kg/kg and a capture rate of 90%. Solvent samples were analysed by titration and CO2 solvent loadings well above 0.5mol CO2/mol MEA were determined. This high CO2 loading is possibly due to good absorptions properties, such as the absorption height of 23.9 m, a low gas velocity of approx. 1 m/s in the absorber and low lean solvent and flue gas temperatures of 32 and 35°C. Solvent degradation in the pilot plant is clearly dominated by oxidative degradation forming formate and oxalate as major degradation products. Due to the application of the pre-scrubber the increase of inorganic salts is more or less continuous at a moderate level. Finally, a system for managing and maintaining solvent properties over long operational periods is developed and discussed.

Ultra-violet Treatment as a Strategy for Destruction of Degradation Products from Amine Based Post Combustion CO2 Capture

The amine-based post-combustion capture (PCC) of CO2 is an option being considered for the reduction of anthropogenic CO2 emissions. PCC plants will be attached or retro-fitted to fossil-fuel fired power generating infrastructure (i.e. large stationary point sources) during the transition to renewable energy, which is expected to take place over several decades. Despite being an established technology widely used to remove CO2 from small scale-commercial process such as natural gas sweetening, there are many challenges that must be overcome before large scale implementation of the process can be realised. Some of these challenges include:•Reducing plant capital costs•Reducing the energy required for solvent regeneration/release of captured CO•Reducing solvent degradation in the presence of O2 and other flue gas contaminants, such as NOx and SOx,and•Reducing and understanding the environmental impact i.e. the potential of solvents and solvent degradation products to be released into the environment through off-gases, leaks or spills, and any associated impact this might have.Several recent research articles1-3 have highlighted the propensity of amine-based solvents to undergo certain chemical transformations, both in the condensed and aqueous phases, which produce harmful materials such as nitrosamines and nitramines. The formation and emission of nitrosated amines from the PCC process has not been fully investigated, although it is now the focus of some research agencies in Europe and Australasia. Nitrosamine formation mechanisms are presented in relation to the post- combustion capture of CO2 with aqueous amine solvents. The relative merits of nitrosamine mitigation strategies are also discussed. In particular the susceptibility of several nitrosamines to UV destruction is explored; the results are compared with TD-DFT results which predict excitation energies with good accuracy. The rate of destruction versus UV wavelength is also discussed, with a view to understanding which electronic transition facilitates decomposition

Piperazine Degradation in Pilot Plants

Concentrated, aqueous piperazine (PZ) has shown promise as a solvent for use in amine scrubbing of post - combustion flue gas to reduce CO2 emissions. Compared with 1-ethanolamine (MEA), PZ has a greater CO2 absorption rate, capacity, and thermal stability. These properties should reduce the overall energy requirements of a CO2 capture facility operating with PZ solvent compared to one operating with MEA.Between 2009 and 2011, 4 campaigns were run at the pilot plant at the Separations Research Program (SRP) of the University of Texas using an inventory of 8 m PZ. Synthetic flue gas consisting of CO2 mixed with air was used at a flow rate equivalent to a 0.1 MW coal-fired power plant. Due to the high oxygen content of the synthetic flue gas, substantial oxidative degradation was anticipated in this campaign. Another campaign was run at “Pilot Plant 2” (PP2) using PZ. This pilot plant used a slipstream of real flue gas drawn from a coal-fired power plant. Solvent samples were collected during campaigns at both SRP and PP2.The operating CO2 capacity of the SRP PZ solvent decreased approximately 10% compared to fresh, undegraded 8 m PZ. The heat of CO2 absorption and the CO2 absorption rate at 40°C (absorber operating conditions) did not change significantly, but greater temperature dependence was observed at higher temperature. These property changes indicate that changes in the solvent have occurred, but that the resulting solvent is not significantly worse than clean piperazine.It is known from bench-scale studies that PZ can degrade into a variety of products, including ethylenediamine (EDA), formate, N-formylpiperazine (FPZ), acetate, and 1-(2-aminoethyl)-piperazine (AEP). These products were observed in the degraded solvents of both pilot plants, in small concentrations compared to bench-scale results.As a secondary amine, PZ could potentially react with nitrite to form the known carcinogens N-nitrosopiperazine (MNPZ). Nitrite could accumulate in the solvent either through absorption of NO2 from the flue gas or degradation of the amine solvent. The synthetic SRP flue gas contained only ambient atmospheric levels of NOx. MNPZ was observed in the SRP solvent at a low concentration of 0.09 mmol/kg. The flue gas used in PP2 was drawn from a coal boiler and was treated by selective catalytic reduction to reduce NOx concentration. Samples collected at regular intervals from PP2 show that after an initial spike up to 2.87 mmol/kg early in the campaign, MNPZ settled at a steady state concentration of around 0.9 1.2 mmol/kg. It is hypothesized that thermal degradation of the MNPZ in the stripper prevented further accumulation beyond these levels.

Nitrosamine degradation by UV light in post-combustion CO2 capture: Effect of solvent matrix

Potential production and emission of nitrosamines during post-combustion CO2 capture has drawn some attention due to their toxicity and potential carcinogenicity. One of the possible ways to reduce the concentration of nitrosamines is irradiation of the liquid streams of the capture plant with UV light. This paper shows experimental results of the degradation of nitrosamines such as N-nitroso-diethanolamine (NDELA) and N-mononitroso-piperazine (MNPZ) in different solvent matrices. These solvent matrices include water and laboratory grade monoethanolamine (MEA) aqueous solutions, as well as aqueous MEA solution and wash water that had been used in a CO2 capture pilot plant connected to a coal-fired power plant. Experiments were conducted in dedicated batch set-ups and in a continuous mini CO2 capture plant. Results show that the UV absorbance of impurities (degradation products and/or dissolved metals) present in MEA solvent that had been used in a pilot plant significantly reduces the UV degradation rate of nitrosamines. Furthermore, UV light seems to accelerate the degradation of the capture solvent itself. For these reasons, if UV light treatment is to be used in full-scale post-combustion CO2 capture plants, suitable locations would be the absorber's washing section or the stripper's condensate. At these locations, less interference of degradation products can occur and there is less solvent to be degraded.

Do we underestimate the impact of particles in coal-derived flue gas on amine-based CO2 capture processes?

The effect of particulate matter on the amine-based capture process has, up till now, not been considered in much detail due to the relatively low concentration of particulate entering the capture plant. In this study we present results of leaching tests with 30 wt% MEA utilising real fly ash samples from a range of European coal-fired power plants. The effect of a number of parameters including CO2 loading, temperature, pH, leaching time, solid/liquid ratio & organic heat stable salts have been investigated. These experiments show that the behaviour of the various compounds and elements is not uniform with different conditions. A strong correlation between reducing pH/increasing CO2 loading and Fe, Cr & V levels is observed, but is not seen for other heavy metals. This impact of pH on metal solubility is striking and suggests that Fe, in particular, may be transported by the liquid system and stored as deposits in the stripper where increased pH reduces the solubility of Fe compounds. The presence of oxalate as a heat stable salt leads to the precipitation of calcium oxalate when calcium phosphate is leached out of the ash. This could result in deposits in areas such as the reboiler that may lead to plugging, reduced heat transfer efficiency and even corrosion issues. Solid/liquid ratio was also found to have some effect with lower solid/liquid ratios showing higher relative solubility for heavy metals. Temperature and leaching time were also investigated but only minor increases in metals content were observed by increasing either of these parameters. The results observed strongly suggest that the effects of particulate matter on the post-combustion capture process should not be ignored, particularly if levels are sufficient to lead to significant build up of ash in the solvent. Ash captured in the liquid has the potential to release significant amounts of Fe, Mg, Ca and PO4 being a concern for the enhancement of solvent degradation processes.

Corrosion Investigations In 2-ethanolamine Based Post- Combustion CO2 Capture Pilot Plants

Corrosion is an essential operational factor to characterize for future demonstration and commercial carbon capture plants. In this paper, three approaches have been used to investigate corrosion in CO2 capture pilot plants: corrosion coupons, on-line monitoring and pilot plant inspection. These tests were realized in two pilot plants: Esbjerg, Dong Energy and Maasvlakte, TNO. Consistent results were obtained. In general, carbon steel and austenitic stainless steel behave well in most of the zones. Several more critical zones have been identified: stripper sump, high temperature lean solvent pipe, reboiler and reclaimer. Some corrosion mechanisms such as flow induced degradation, corrosion due to CO2 or the corrosive effect of the solvent degradation have been evidenced.

Location-Specific Technoeconomic Evaluation of a Novel Amine Technology

A novel amine capture technology for CO2 emissions has been developed by Huaneng/Xi’an Thermal Power Research Institute. Lawrence Livermore National Laboratory (LLNL), on behalf of the U.S.-China Clean Energy Research Center, has evaluated the technology using location-specific economic parameters to reflect power generation loss from a coal-fired power generation plant due to amine regeneration, the necessary utility constraints and investment, and the constraints of the location.The conceptual design used for cost estimates consists of a pre-absorption cooler (cooling by injection of water directly into the flue gas was not feasible because of 100% flue gas humidity post-flue gas desulfurizer), an absorber with a spray stage to minimize evaporative amine losses; an economizing heat exchanger and trim heaters and coolers: a stripper with a reboiler and condenser to recover absorbed CO2; a five-stage CO2 compression train with intercooling and water removal; and an ion exchange process to control build-up of heat-stable salts by treating a bleed stream from the lean amine stream.We conclude that Huaneng's novel amine composition, because of the use of hindered and tertiary amines, has a lower heat of regeneration and hence reduces the power generation penalty. Further, we assess that the hindered and tertiary amines are less susceptible to thermal and oxidative degradation, although they are still susceptible to degradation by reaction with CO2. We estimate the reduced power generation penalty and reduced solvent degradation gives a modest but tangible cost advantage relative to 30% MEA.Among the location-specific constraints we have identified are: limited ability to cool incoming flue gas by water injection because of high humidity; and poor soil conditions that would require extensive civil engineering prior to plant construction. These differences we assess will increase the cost of implementing an amine-based capture technology over costs based on assumed greenfield construction.

Accelerated Aging and Qualitative Degradation Pathway Analysis of CO2 Capture Solvents Containing Ionic Liquids

A qualitative study was conducted to analyze degradation of CO2 capture solvents containing ionic liquids by GC/MS under a variety of conditions representative of the carbon capture process. Aqueous monoethanolamine (MEA) was used as a benchmark for solvent degradation and compared to two advanced CO2 capture solvents containing ionic liquids. Accelerated aging experiments were conducted in the laboratory by exposing solvents to various gases (N2, air, CO2, or SO2) at elevated temperature in sealed cylinders. Degradation products were analyzed by GC/MS and key pathways leading to their formation were elucidated. For all solvents, degradation was most rapid and lead to a wider array of products in the presence of CO2 compared to the other studied gases. The ionic liquid solvents showed enhanced degradation and a different set of degradation products than those observed for MEA. In one case, the anion of the ionic liquid was found to be reactive and led to a unique primary degradation mechanism not seen in ...

Studies on the changes in the composition of solvent during photochemical generation of uranous ions in uranium loaded 30 % TBP-n-dodecane-HNO3 system

Present investigation describes our study on photochemical generation of uranous ions and consequent degradation of solvent in the uranium loaded 30 % Tributyl phosphate-n-dodecane-nitric acid system. Samples of 30 % TBP-n-dodecane loaded with uranium were subjected to UV photolysis at 254, 300 and 350 nm respectively. Wavelength dependent formation of U(IV) has been determined spectrophotometrically by measuring absorbance at 656 nm. Additionally, photochemical yield of U(IV) has also been estimated semi quantitatively as a function of time of photolysis. The changes in the solvent composition under different photochemical conditions have been studied by examination of comparative gas chromatographic profiles of the solvent before and after photolysis. Among the wavelength of photo irradiation studied, the yield of U(IV) was found to be optimum at 300 nm with least degradation of PUREX solvent.

Towards Commercial Scale Postcombustion Capture of CO2 with Monoethanolamine Solvent: Key Considerations for Solvent Management and Environmental Impacts

Chemical absorption with aqueous amine solvents is the most advanced technology for postcombustion capture (PCC) of CO(2) from coal-fired power stations and a number of pilot scale programs are evaluating novel solvents, optimizing energy efficiency, and validating engineering models. This review demonstrates that the development of commercial scale PCC also requires effective solvent management guidelines to ensure minimization of potential technical and environmental risks. Furthermore, the review reveals that while solvent degradation has been identified as a key source of solvent consumption in laboratory scale studies, it has not been validated at pilot scale. Yet this is crucial as solvent degradation products, such as organic acids, can increase corrosivity and reduce the CO(2) absorption capacity of the solvent. It also highlights the need for the development of corrosion and solvent reclamation technologies, as well as strategies to minimize emissions of solvent and degradation products, such as ammonia, aldehydes, nitrosamines and nitramines, to the atmosphere from commercial scale PCC. Inevitably, responsible management of aqueous and solid waste will require more serious consideration. This will ultimately require effective waste management practices validated at pilot scale to minimize the likelihood of adverse human and environmental impacts from commercial scale PCC.

Influence of Phase Modifiers on the Degradation of Tri-n-octylamine/dodecane Extracting Mixture by an Acidic Solution of Vanadium (V)

The kinetics of degradation of a mixture of tri-n-octylamine (extractant) and various alcoholic phase modifiers in n-dodecane in contact with acidic aqueous sulfate solutions containing vanadium (V) has been investigated. The nature of the modifier influences the kinetics of degradation and an improvement of the resistance against the chemical degradation is obtained when secondary alcohol (2-nonanol) or tertiary alcohols such as 9-octyl-9-heptadecanol are used as phase modifiers instead of 1-tridecanol. For instance, the kinetic constant of degradation is divided by one half when 9-octyl-9-heptadecanol is used as phase modifier instead of 1-tridecanol. On the contrary, the alcohols containing aromatic substituents or fluorine atoms are responsible for an increase of the chemical degradation of the extraction solvent.