Supercritical carbon dioxide (SC-CO₂) dyeing of cellulose acetate: An opportunity for a “greener” circular textile economy

This article compares the dyeing of cellulose diacetate (cellulose-based) and polyester fabrics using supercritical carbon dioxide (SC-CO₂) and aqueous media. The benefits of dyeing in SC-CO₂ were clearly demonstrated in laboratory-based and pilot-scale studies in terms of increased colour strength, uniformity, fastness and the absence of auxiliaries such as dispersing agents or surfactants. In addition, the “super-levelling” nature of the SC-CO₂ medium was demonstrated in the reprocessing of polyester “waste textile” and the re-use of the “locked-in waste” colourant. The SC-CO₂ processing medium can be utilised to accurately colour “multiple life” polyester and cellulose acetate uniformly and to creatively tie-dye polyester and cellulose acetate fabrics. Through SC-CO₂ fluid technology, we can envisage a viable waterless circular manufacturing and recycling/remanufacturing framework for the predominantly polyester global fibre market coupled to the sustainably sourced, biodegradable cellulose diacetate as a replacement for cotton. The key technical and commercial advantages being the use of a single solvent dye class for both polyester and the cellulose diacetate, saving on energy costs, integrated simpler processing, reduced water usage and associated efficient recycling. Further, repositioning the cellulosic fibre industry towards using sustainable forests is attractive in terms of improved land, water and environmental management

CO2-wettability of low to high rank coal seams: Implications for carbon sequestration and enhanced methane recovery

Coal seams offer tremendous potential for carbon geo-sequestration with the dual benefit of enhanced methane recovery. In this context, it is essential to characterize the wettability of the coal–CO2–water system as it significantly impacts CO2 storage capacity and methane recovery efficiency. Technically, wettability is influenced by reservoir pressure, coal seam temperature, water salinity and coal rank. Thus a comprehensive investigation of the impact of the aforementioned parameters on CO2-wettability is crucial in terms of storage site selection and predicting the injectivity behaviour and associated fluid dynamics. To accomplish this, we measured advancing and receding water contact angles using the pendent drop tilted plate technique for coals of low, medium and high ranks as a function of pressure, temperature and salinity and systematically investigated the associated trends. We found that high rank coals are strongly CO2-wet, medium rank coals are weakly CO2-wet, and low rank coals are intermediate-wet at typical storage conditions. Further, we found that CO2-wettability of coal increased with pressure and salinity and decreased with temperature irrespective of coal rank. We conclude that at a given reservoir pressure, high rank coal seams existing at low temperature are potentially more efficient with respect to CO2-storage and enhanced methane recovery due to increased CO2-wettability and thus increased adsorption trapping

Experimental analysis and mathematical prediction of Cd(II) removal by biosorption using support vector machines and genetic algorithms

We investigated the bioremoval of Cd(II) in batch mode, using dead and living biomass of Trichoderma viride. Kinetic studies revealed three distinct stages of the biosorption process. The pseudo-second order model and the Langmuir model described well the kinetics and equilibrium of the biosorption process, with a determination coefficient, R2 > 0.99. The value of the mean free energy of adsorption, E, is less than 16 kJ/mol at 25°C, suggesting that, at low temperature, the dominant process involved in Cd(II) biosorption by dead T. viride is the chemical ion-exchange. With the temperature increasing to 4050°C, E values are above 16 kJ/mol, showing that the particle diffusion mechanism could play an important role in Cd(II) biosorption. The studies on T. viride growth in Cd(II) solutions and its bioaccumulation performance showed that the living biomass was able to bioaccumulate 100% Cd(II) from a 50 mg/L solution at pH 6.0. The influence of pH, biomass dosage, metal concentration, contact time and temperature on the bioremoval efficiency was evaluated to further assess the biosorption capability of the dead biosorbent. These complex influences were correlated by means of a modeling procedure consisting in data driven approach in which the principles of artificial intelligence were applied with the help of support vector machines (SVM), combined with genetic algorithms (GA). According to our data, the optimal working conditions for the removal of 98.91% Cd(II) by T. viride were found for an aqueous solution containing 26.11 mg/L Cd(II) as follows: pH 6.0, contact time of 3833 min, 8 g/L biosorbent, temperature 46.5°C. The complete characterization of bioremoval parameters indicates that T. viride is an excellent material to treat wastewater containing low concentrations of metal

Interfacial Interactions and Wettability Evaluation of Rock Surfaces for CO2 Storage

To reduce CO2 emissions into the atmosphere, different scenarios are proposed to capture and store carbon dioxide (CO2) in geological formations (CCS). Storage strategies include CO2 injection into deep saline aquifers, depleted gas and oil reservoirs, and unmineable coal seams. To identify a secure and proper strategy for CO2 injection, the fluid displacement at reservoir conditions and thus the wettability of the geological formation need to be understood. Wettability has a strong effect on multiphase rock-fluid interactions and influences the efficiency of an immiscible displacement in the porous medium, the magnitude of irreducible water and residual oil saturations, the microscopic fluid distribution at pore scale in the porous medium, the capillary pressure and relative permeability curves and the electrical properties of the porous medium. Only a limited amount of literature refers to wetting properties of sedimentary rocks and minerals at high pressures and elevated temperatures. Hence, a reliable experimental method to determine the wettability is an important step towards understanding the physics of this phenomenon. This thesis is a collection of experimental work on rock-fluid interactions and wettability behavior of the rock surface related to CO2 storage. The captive-bubble technique is used to evaluate the wetting properties of different rock surfaces in the presence of CO2 and/or synthetic flue gas. To mimic the in-situ conditions, experiments are performed at high pressures and elevated temperature (up to 16 MPa and at 318 K).Geoscience and EngineeringCivil Engineering and Geoscience

Investigation on Mechanical Behaviour of Coal and Overburden Rock for UCG

In recent years, the coupled UCG-CCS process has been considered as another potential CCS option, which can offer integrated energy recovery from coal and storage of CO2. However, existing potential problems may counteract its potential benefits. To develop a generic UCG-CCS site characterisation workflow, different aspects of this complex process, such as cavity progression and geomechanics, contamination of groundwater and subsidence impacts, need to be re-considered and understood. In this process, the thermo-mechanical behaviour of the roof rock and coal are the initial parameters to predict the stability and the development of the production cavity. These parameters affect heat conduction and the stability and caving of roof materials, especially under conditions of high stress and temperature. In this study, several experimental setups have been designed and built to study the thermo-mechanical properties of coal and overburden rock for UCG process. These experimental data can get an idea of elastic constants of rocks, the fracture growth mechanisms, the fracture orientations the maximum/yield stresses that the sample withstands, the conditions under which spalling occurs in overburden rock, as well as the rate which this take place. These results will be used as input for the modelling of the cavity growth of UCG.Geoscience & EngineeringCivil Engineering and Geoscience

Novel application of PEG/SDS interaction as a wettability modifier of hydrophobic carbonate surfaces

Wettability alteration of carbonate reservoirs from oil-wet to water-wet is an important method to increase the efficiency of oil recovery. Interaction between surfactants and polymers can enhance the effectiveness of surfactants in EOR applications. In this study, the interaction of polyethylene glycol (PEG) with an ionic surfactant, sodium dodecyl sulphate (SDS), is evaluated on an oil-wet carbonate rock surface by using contact angle measurements. The results reveal that wettability alteration of carbonate rocks is achieved through PEG/SDS interaction on the rock surface above a critical aggregation concentration (CAC). The behaviour of PEG/SDS aqueous solutions is evaluated using surface and interfacial tension measurements. Furthermore, the effect of PEG and SDS concentrations and impact of electrolyte addition on PEG/SDS interaction are investigated. It is shown that electrolyte (NaCl) can effectively decrease the CAC values and accordingly initiate the wettability alteration of rocks. Moreover, in a constant SDS concentration, the addition of NaCl leads to a reduction in the contact angle, which can also be obtained by increasing the aging time, temperature and pre-adsorption of PEG on the rock surface.Applied Geophysics and Petrophysic

Study of shale wettability for CO2 storage

For a water-saturated cap-rock, which consists of a low-permeability porous material, the wettability of the reservoir rock-connate water- CO2 system and the interfacial tension (IFT) between CO2 and connate water are the significant parameters for the evaluation of the capillary sealing. Also, the amount of capillary-trapped CO2 depends on the wettability of reservoir rocks. The wettability of the rock matrix has a strong effect on the distribution of phases within the pore space and thus on the entire displacement mechanism and storage capacity. In this work, the equilibrium contact angles of water/shale system were determined with CO2 for a wide range of pressures at a constant temperature of 318 K by using the dynamic captive bubble method. The results reveal that intermediate-wet conditions and hence possible leakage of CO2 must to be considered at relatively high pressures, however, the salt concentration of the water in the shales plays an important role too. The results show that this estimate is highly dependent on the pore structure, fluid composition and pressure/temperature conditions of the reservoirs. These properties need to be first evaluated before estimates for shale capillarity is used.Geoscience & EngineeringCivil Engineering and Geoscience

Effect of matrix wettability CO2 assisted gas-oil garvity drainage in naturally fractured reservoirs

The wettability behavior of the matrix block is one of the major factors controlling the effectiveness of the employed EOR methods in NFRs. Water injection in NFRs with mixed-wet or effectively oil-wet matrix blocks usually results in low oil recoveries. In this case, gas injection is considered to be an alternative process, where the process benefits from the gravity forces and the process is called gas-oil gravity drainage. In this study, the effect of matrix wettability on the efficiency of gravity drainage by CO2 injection is addressed. Laboratory experiments and numerical simulation were performed to analyze the process under different wettability conditions of the matrix. It is concluded that for a system with an effectively oil-wet matrix, water is the most non-wetting phase while CO2 is the intermediate-wetting phase. In the three phase setting, which includes carbon dioxide, this is considered favorable for oil production. However, with a strongly water-wet matrix, CO2 is always the least wetting phase. For this condition, it turns out that when water is displaced by the gravity drainage process part of the oil is also produced. It is observed that higher oil recoveries are achieved by CO2 injection in an oil-wet matrix block.Geoscience & EngineeringCivil Engineering and Geoscience

Wettability Evaluation of a CO₂/Water/Bentheimer Sandstone System: Contact Angle, Dissolution, and Bubble Size

The success of CO₂ storage in deep saline aquifers and depleted oil and gas reservoirs is largely controlled by interfacial phenomena among fluid phases and rock pore spaces. Particularly, the wettability of the rock matrix has a strong effect on capillary pressure, relative permeability, and the distribution of phases within the pore space and thus on the entire displacement mechanism and storage capacity. Precise understanding of wettability behavior is therefore fundamental when injecting CO₂ into geological formations to sequestrate CO₂ and/or to enhance gas/oil production. In this study, the contact angles of Bentheimer sandstone/water/CO₂ or flue gas have been evaluated experimentally using the captive-bubble technique in the pressure range from 0.2 to 15 MPa. The experiments were conducted using different compositions of aqueous phase with respect to CO₂, i.e., unsaturated and fully saturated. It has been shown that a reliable contact-angle determination needs to be conducted using a pre-equilibrated aqueous phase to eliminate dissolution effects. In the fully saturated aqueous phase, the Bentheimer sandstone/water system is (and remains) water-wet even at high pressures against CO₂ and/or flue gas. In these systems, the data of the stable contact angle demonstrate a strong dependence on the bubble size, which can be mainly explained by the gravity (buoyancy) effect on bubble shape. However, the surface nonideality and roughness have significant influence on the reliability of the contact-angle determination. The results of this study prove that in order to avoid the dependency of the contact angle on the bubble size in these systems, the effect of gravity (buoyancy) on bubble shape has to be considered by calculation of the Bond number; for systems characterized by Bond numbers less than 0.9, the influence of the bubble radius on the contact angle becomes insignificant. The experimental results show that, in contrast to quartz, the phase transition of CO₂ from subcritical to supercritical has no effect on the wettability of the Bentheimer sandstone/water system, which originates from differences in the surface charges of quartz and Bentheimer sandstone. In an unsaturated system, two dissolution regimes are observed, which may be explained by density-driven natural convection and molecular diffusion