A sustainable and low pollutive strategy for the recycling of waste hot-gas filter bags: The development of filter reinforced epoxy composites.

The fast accumulation of waste hot-gas filter bags has become a growing public concern considering its difficulty in degradation, severe pollution elicited by landfill and incineration, high energy consumption during burning or complicated recycling and low margin of regenerative products. Herein, we provide a new feasible recycling strategy by directly employing the cleaned polyphenylene sulfide (PPS) /polytetrafluoroethylene (PTFE) waste filters in their fabric state as the reinforcement of epoxy composites. Merely two layers of filters could produce composites with flexural strength and modulus sufficient for many applications and the additional carbon fiber fabric (CFF) covering could further strengthen the composites (295 to 1010 % increments). The filters also showed a bonding promotion function between CFF and polymethacrylimide foam in lightweight composites. After hydrothermal treatment, the composites reinforced by the recycled filters displayed 97.2 % and 90.9 % retention rate for flexural strength and modulus, respectively. Compared to the pure epoxy, the composites could achieve a limiting oxygen index of 27.6 %, and display 24 % decline in thermal energy release and 20.0 to 31.0 % reduction in the generation rate of combustion products, indicating strengthened flame-retardancy. With shortened processes and elevated properties of composites, the approach established for recycling waste filters in this work showed far-reaching implications in carbon emission reduction, environmental pollution diminishing and commercialization potential.

Insight into the role of pre-assembly and desolvation in crystal nucleation: a case of p-nitrobenzoic acid.

As one of the most important phenomena in crystallization, the crystal nucleation process has always been the focus of research. In this work, influences of pre-assembly species and the desolvation process on the crystal nucleation process were studied. p-Nitrobenzoic acid (PNBA) was taken as a model compound to investigate the relationship between solution chemistry and nucleation kinetics in seven different solvents. One unsolvated form and four solvates of PNBA were obtained and one of the solvates was newly discovered. The nucleation behaviours and nucleation kinetics of PNBA in the seven solvents were studied and analyzed. Density functional theory (DFT) and solvation energy calculation were adopted to evaluate the strength of solute-solvent interactions. Vibrational spectroscopy combined with molecular simulation was applied to reveal the pre-assembly species in the solution. Based on these results, a comprehensive understanding of the relationship between molecular structure, crystal structure, solution chemistry and nucleation dynamics was proposed and discussed. It was found that the structural similarity between solution chemistry and crystal structure, the interaction between specific sites and the overall strength of solvation will jointly affect the nucleation process.