Recovery of triglycerides from used frying oil by extraction with liquid and supercritical ethane

Advances and challenges in the fractionation of edible oils and fats through supercritical fluid processing

Petrochemical solvents are widely used for the extraction and fractionation of biomolecules from edible oils and fats at an industrial scale. However, owing to its safety concerns, toxicity, price fluctuations, and sustainability, alternative solvents and technologies have been actively explored in recent years. Technologies, such as ultrasound and microwave-assisted extraction, supercritical carbon dioxide extraction, supercritical fluid fractionation, and sub-critical water extraction, and solvents, like ionic liquids and deep eutectic solvents, are reported for extraction and fractionation of biomolecules. Among them, supercritical carbon dioxide extraction and fractionation are some of the most promising green technologies with the potential to replace petrochemical-based conventional techniques. The addition of cosolvents, such as water, ethanol, and acetone, improves the extraction of amphiphilic and polar compounds from edible oils and fats. Supercritical fluid processing has diverse applications, including concentration of solutes, selective separation of desired molecules, and separation of undesirable compounds from the feed material. Temperature, pressure, particle size, porosity, flow rate, solvent-to-feed ratio, density, viscosity, diffusivity, solubility, partition coefficient, and separation factor are the fundamental factors governing the extraction and fractionation of desired biomolecules from lipids. Supercritical fluids stand alone compared to conventional fluids, because of their tunable solvent properties. Overall, it is to be noted that supercritical fluid-based methods have lots of scope to replace conventional solvent-based methods and progress toward the creation of sustainable food-processing techniques. This review critically evaluates the parameters responsible for the extraction and fractionation of biomolecules from edible oils and fats under supercritical conditions.

Photocatalytic Reduction of CO2 with N-Doped TiO2-Based Photocatalysts Obtained in One-Pot Supercritical Synthesis

The objective of this work was to analyze the effect of carbon support on the activity and selectivity of N-doped TiO₂ nanoparticles. Thus, N-doped TiO₂ and two types of composites, N-doped TiO₂/CNT and N-doped TiO₂/rGO, were prepared by a new environmentally friendly one-pot method. CNT and rGO were used as supports, triethylamine and urea as N doping agents, and titanium (IV) tetraisopropoxide and ethanol as Ti precursor and hydrolysis agent, respectively. The as-prepared photocatalysts exhibited enhanced photocatalytic performance compared to TiO₂ P25 commercial catalyst during the photoreduction of CO₂ with water vapor. It was imputed to the synergistic effect of N doping (reduction of semiconductor band gap energy) and carbon support (enlarging e⁻-h⁺ recombination time). The activity and selectivity of catalysts varied depending on the investigated material. Thus, whereas N-doped TiO₂ nanoparticles led to a gaseous mixture, where CH₄ formed the majority compared to CO, N-doped TiO₂/CNT and N-doped TiO₂/rGO composites almost exclusively generated CO. Regarding the activity of the catalysts, the highest production rates of CO (8 µmol/gTiO₂/h) and CH₄ (4 µmol/gTiO₂/h) were achieved with composite N¹/TiO₂/rGO and N¹/TiO₂ nanoparticles, respectively, where superscript represents the ratio mg N/g TiO₂. These rates are four times and almost forty times higher than the CO and CH₄ production rates observed with commercial TiO₂ P25.

Removal of emerging pollutant dibutylhydroxytoluene from water with CNT/TiO2 catalysts in a visible LED photoreactor

For the photocatalytic degradation of antioxidant 2,6-di-tert-butyl-hydroxytoluene (BHT), several TiO₂-based composites have been prepared in MWCNT from titanium isopropoxide and ethanol via supercritical CO₂ synthesis followed by calcination at 400 °C. TEM and XRD showed uniform coverage of CNT by 10 nm TiO₂ particles in the anatase form, and spectral analyses revealed the formation of CNT/TiO₂ structure. Further, synthesized material displayed significant visible light absorption and absorption edge shifted to longer wavelengths. Once the material was characterized, the effect of adsorption and photochemical degradation of BHT was investigated in the wavelength range from 400 to 700 nm, in batch mode, by monitoring the concentrations of BHT as a function of time. CNT/TiO₂ composites were more efficient than commercial TiO₂ P25 in the photodegradation of the antioxidant. In particular, CNT⁵⁰/TiO₂⁵⁰, a composite with 50% by weight of CNT, was the best catalyst, stable, and completely degrading BHT within 30 min of exposure to visible light. The role played by different reactive oxidative species (h⁺, OH ^·, ¹O₂, and [Formula: see text]) in the photocatalytic reaction was also studied by using appropriate radical scavengers that inhibited the corresponding active species. Superoxide radical was found the main oxidizing agent.