Factors Influencing CO2 and Energy Penalties of CO2 Mineralization Processes.

Carbon mineralization is one of the carbon capture utilization, and storage (CCUS) technologies that can be used to capture large quantities of CO2 and convert it into stable carbonate products that can be stored easily. Several CO2 mineralization processes have been proposed; however, there are no commercial-scale projects because there are still significant issues that need to be improved before commercialization can take place. In this work, we evaluate the CO2 and energy penalties related to the most well-known types of mineralization processes developed to date, in which the mineralization reaction takes place directly under aqueous conditions, high pressures and temperatures, and compared these with newer T-P swing processes and ball-mill reactor processes, which are under development. The data used in the evaluation are taken from published literature. By comparing the three processes, we identify important variables that contribute to high CO2 and energy penalties so that future research can focus on optimization of these variables. It is observed that slurry concentration (heating) and particle size (grinding) are critical factors, with mineral calcination and operating pressure constituting other important factors.

In vitro and in vivo release of gentamicin from biodegradable discs.

Osteomyelitis is an infection of the bone and successful treatment involves the removal of the affected bone and the tissue by a surgical procedure following prolonged systemic and local antibiotic therapy for 4 to 6 weeks. The current local treatment is done by poly methyl methacrylate (PMMA) beads loaded with gentamicin and PMMA, being nondegradable, is to be removed by a second surgical procedure. The current study aims to develop a biodegradable composition that gives sustained release and hence reducing the need for a second surgery. Gentamicin-loaded discs were produced by compressing microparticle-gentamicin mixture obtained by spray drying a mixture of gentamicin in a solution of a biodegradable polymer. Different copolymers of poly (DL-lactic-co-glycolic acid) (PLGA) were used to study the effect of copolymer ratio and the hydrophilic-hydrophobic nature of the polymer. Theoretical drug loading up to 25% were studied and it was observed that 10% drug loading was optimum for gentamicin to be used as solid in spray drying. The results showed that about 60% of the drug is released in about 5 to 6 days and the remaining drug is released in about 30 days in total. An in vivo study was carried on rabbit femur and the local area and systemic concentration of gentamicin was monitored. It was observed that the local area concentration of gentamicin was above minimum inhibitory concentration for more than 20 days and this was also validated by computer simulations.

Gentamicin-loaded discs and microspheres and their modifications: characterization and in vitro release.

Osteomyelitis is an infection of the bone, and successful treatment involves local administration for about 6 weeks. Gentamicin is a very hydrophilic drug and tends to come out into the water phase when microspheres are fabricated using solvent evaporation method. Hence, spray drying is an option, and it was observed that the release rate tends to be fast when the particle size is small and large particles cannot be prepared by spray drying. In an effort to get better encapsulation efficiency and release rate, we have worked on the possibility of compressing the microspheres into discs and modifying the porosity of the discs by using biocompatible materials like polyethylene glycol (PEG) and calcium phosphates and also on the fabrication of double-walled and composite microspheres. In the case of microspheres, two methods of fabrication both based on solvent evaporation method were employed. The two polymers used are poly-L-lactide (PLLA) and copolymers of poly-DL-lactic-co-glycolic acid (PLGA). One method is based on the spreading coefficient theory for the formation of double-walled microspheres by using single solvent, while the other is based on the property of PLLA not being soluble in ethyl acetate (EA). Characterization to check if the microspheres formed are double-walled was performed. The fabrication method where two solvents, dichloromethane (DCM) and ethyl acetate, were used gave double-walled microspheres, while the other where only dichloromethane was used gave composites. The double-walled microspheres were smaller in size compared to the composites, which were in the range of 100-600 microm. This can be attributed to the difference in the fabrication procedure. We were able to achieve better encapsulation efficiencies of more than 50% and slower release rates, which lasted for about 15 days. It was observed that size played a major role in the encapsulation efficiency and release rates. The possibility of achieving better results by studying the effect of concentration of polymer in solvent and the effect of using different polymers was investigated.