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Coal is a major resource in China both for chemicals production and power generation, but its impact on the environment demands attention. Solvent pretreatment is an effective method to realize cleaner utilization of coal. Shendong sub-bituminous coal was treated with three different deep eutectic solvents (DESs) – choline chloride (ChCl)-urea, ChCl-glycerol, and ChCl- ethylene glycol – at temperature as low as 120°C. Proximate/ultimate analyses, scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy were used to examine the physicochemical changes that occurred in coal after DESs treatment. Results showed that DES treatment led to coal fragmentation and decreased average particle size. Compared with raw coal (33.1%), DES-treated coal showed greater mass loss (35.2 − 37.7%), showing that the amount of low molecular mass species increased after treatment. This was confirmed by the observation that DES-treated coal had more volatile components and less minerals and functional groups that contained oxygen (especially C−O). The content of elemental sulfur also decreased from 0.26% to 0.10 − 0.15% after DES treatment, along with a reduction in aliphatic chain length and aromatic substitution degree, which were from 10.73 to 9.33−10.08 and 16.70% to 10.73−15.36%, respectively. The macromolecular structure of the coal was destroyed as a result of DES’s interactions with the weak covalent bonds and hydrogen bonds in the coal. These results suggest that DES has the potential to be used as a pretreatment solvent for coal conversion.

The application of nanoparticle coating in a collector could resolve the issues of lesser heat transfer rate and lower thermal efficiency associated with the flat plate collector (FPC). In this study, carbon nanodots (CNDs) synthesized from fish scales wwere coated over the black paint coating to enhance the thermal efficiency of FPC. The effect of various concentrations (0, 0.1, 0.2, and 0.5%w/v) of CND coatings and mass flow rates of air (0.011 kg/s (natural convection) and 0.015, 0.029, and 0.044 kg/s (forced convection)) on the collector outlet air temperature and efficiency of the FPC were evaluated with a control (black paint). Solar radiation ranged from 382 to 913 W/m2 on the experimental days, and the atmospheric temperature and relative humidity values varied from 26.2 to 34.8°C and 50–72%, respectively. Fourier transform infrared spectroscopic studies of absorber plate coating revealed that the CNDs interacted with the black paint surface through phenolic OH, C=O, and NH mainly by hydrogen bonding. It was observed that the exit air temperature of the collector varied from 55 to 65°C. The thermal efficiency of 59.97%, 62.72%, 71.87%, and 67.75% was obtained for control (black-paint), 0.1%, 0.2%, and 0.5% CNDs coating, respectively, at the airflow rate of 0.044 kg/s. The coating of 0.2% CNDs recorded a maximum thermal efficiency of 71.87% at 0.044 kg/s. Overall, the CNDs coating on the absorber surface enhanced the thermal efficiency of the collector by 19.84% over the black paint-coated surface (control). It can be concluded from the study that CNDs coating resulted in enhanced outlet air temperature and improved thermal efficiency, which can be utilized for low-temperature applications like the drying of food materials.

The remarkable properties of polysulfone (PSF) membranes have contributed to their use in many ultrafiltration applications. Meanwhile, this huge usage of PSF films and its short service life have generated a huge amount of waste PSF films that need to be managed carefully. Within this framework, this is the first research specifically developed to valorize the end-of-life of PSF membranes and convert them into high-value chemical and energy products using pyrolysis treatment. The treatment was performed using a thermogravimetric analyzer (TGA), while the structure and abundance of the phenol and benzoic acid compounds in the generated vapor were determined using Fourier-transform infrared (FTIR) spectroscopy and Gas chromatography-mass spectrometry (GC-MS). Thermogravimetric recorded data at different conditions (5–30°C/min) was subjected to linear and nonlinear models including KAS, FWO, Friedman, Vyazovkin, and Cai to assess the pyrolytic kinetic behavior of PSF films. The films showed higher content of volatile matter (57%), lower NOx emissions (0.321%), and a little bit more SOX emission (6.909%). The GC-MS showed that the pyrolytic gaseous products are rich in phenol (24.3%) and benzoic acid (52.4%) compounds and the highest abundance was achieved at 30°C/min. Whereas activation energies were estimated in the range of 193–240 kJ/mol based on linear kinetic criteria versus 161–163 kJ/mol in the case of nonlinear models, where R2 values (>0.91) indicated perfection. Also, distributed activation energy and independent parallel reaction kinetic models showed a good fit with the TGA-DTG experimental data with the minimum deviation. The study confirmed the potential of pyrolysis treatment in converting wasted PSF films into a new source for the recovery of phenolic and benzoic acid.