Due to the biotoxicity and ecological hazards of 2,4-toluene diamine (TDA) and 4,4′-methylene dianiline (MDA), it is the key process for upcycling polyurethane (PU) waste to remove them from the PU bio-hydrolysate with high selectivity and efficiency. Herein, MIL-53 series metal–organic frameworks (MOFs) were prepared and applied to remove aromatic diamines. Besides, the effects of their different structural units on the adsorption performance were investigated. Among the three metal nodes (Cr 3+ , Al 3+ , Fe 3+ ) of MIL-53, MIL-53(Al) demonstrated the highest adsorption capacities upon TDA (4.17 mmol/g) and MDA (2.00 mmol/g) due to its more μ 2 -OH sites and higher porosity. Compared with MIL-53(Al), DUT-4 and DUT-5 owned longer linkers but exhibited inferior aromatic diamine adsorption performance, which was ascribed to the more appropriate pore size and more μ 2 -OH sites of MIL-53(Al). Notably, MIL-53(Al) exhibited excellent selectivity towards aromatic diamines, while the removal efficiency reached over 90 %. In addition, spectral analysis before and after adsorption revealed the mechanism, which involved host–guest interactions, H-bonding interactions, and π-π stacking. The results indicate the great potential of applying the optimal MIL-53(Al) as an alternative adsorbent for removing hazardous aromatic diamines from the PU bio-hydrolysate.
Excessive use of polyurethane (PU) polymers has led contributed to serious environmental pollution. The plastic recycling technology using microorganisms and enzymes as catalysts offers a promising green and low-carbon approach for managing plastic waste. However, current methods for screening PU-degrading strains suffer from drawbacks such as being time-consuming and inefficient. Herein, we present a novel approach for screening PU-degrading microorganisms using a quenching fluorescent probe along with the fluorescence-activated droplet sorting (FADS). The FPAP could specifically recognize the 4,4′-methylenedianiline (MDA) derivates released from PU degradation, with fluorescence quenching as a response. Based on the approach, we successfully screen two PU-degrading strains ( Burkholderia sp. W38 and Bacillus sp. C1). After 20 d of cultivation, strain W38 and C1 could degrade 41.58% and 31.45% of polyester-PU film, respectively. Additionally, three metabolites were identified during the degradation of PU monomer (2,4-toluene diamine, 2,4-TDA) and a proposed degradation pathway was established. Consequently, the fluorescence probe integrated with microfluidic droplet systems, demonstrates potential for the development of innovative PU-biocatalysts. Furthermore, the identification of the 2,4-TDA degradation pathway provides valuable insights that can propel advancements in the field of PU biodegradation.
危险品化学品经营许可证（带存储）