| dc.description.abstract | This research aims to develop hierarchical nanoporous tin-based metal-organic frameworks (HP-Sn-MOFs) using a linker derived from polyethylene terephthalate (PET) waste. These HP-Sn-MOFs exhibited a unique hierarchical structure with high stability and multiple active sites, enhancing their wide range of applicability, particularly for the adsorption of Cu and Zn in aqueous media. Response Surface Methodology (RSM) was employed to analyze the influence of critical parameters on the optimal extraction of terephthalic acid (H2BDC) from PET waste and the synthesis optimization of HP-Sn-MOFs under defect engineering, as well as optimal conditions for adsorption of Cu and Zn. Various monocarboxylic acids as modulators, including trifluoroacetic acid (TFA), formic acid (FA), and acetic acid (AA), were investigated to determine their effects on the characteristics of HP-Sn-MOFs. The study also evaluated the adsorption capacity, removal efficiency, and regeneration of HP-Sn-MOFs for Cu and Zn.
The H2BDC extraction from PET waste data showed that NaOH concentration had a more significant effect on H2BDC yield and recovery ratio than hydrolysis temperature and time. The optimal conditions were reached after 12 hours at 200°C and 5% NaOH. The combination of DMSO and citric acid (C6H8O7) was more effective at increasing particle size than H2SO4. Throughout eight consecutive cycles of the DMSO and C6H8O7 mixture, the H2BDC yield maintained a high purity level, ranging from 96% to 98%. These findings underscore the effectiveness of using a combination of DMSO and C6H8O7 to enhance the quality of H2BDC, achieving maximum particle sizes (57.4 μm) and high purity that meet commercial product criteria. This method presents a promising solution for extracting H2BDC from white PET bottle waste, with potential implications for the recycling industry and a positive environmental impact.
These results highlight the critical role of TFA in forming hierarchical nanoporous and architectural HP-Sn-MOF structures with multiple active sites, enhancing crystallinity index (CI), yield, surface area, pore volume, and stability through defect engineering. Optimal conditions for HP-Sn-MOFs using DI water as a solvent included a temperature of 148℃ for 24 h and a molar ratio of H2BDC/TFA of 1.7, resulting in a yield of 98.51 ± 1.47% and a CI of 80.21 ± 1.32%, with no detectable residual H2BDC. Conversely, for HP-Sn-MOFs using ethanol as a solvent, optimal conditions were a temperature of 156℃ for 36 h, a molar ratio of H2BDC/TFA of 1.2, achieving a surface area of 255.8 m2/g, and a pore volume of 0.53 cm3/g. These findings underscore the effectiveness of the synthesis method for HP-Sn-MOF achieved through optimizing critical parameters and defect engineering techniques by modulators. Combining ethanol with water as a mixed solvent and adding TFA and AA in Sn-MOF synthesis significantly enhanced the surface area and pore volume. Under optimal conditions, including a metal concentration of 150 mg/L, a pH of 6.0 for Cu and 7.0 for Zn, and an adsorbent dose of 0.2g per 1L metal solution, HP-Sn-MOF achieved a maximum adsorption capacity (qmax) of 375.94 mg/g for Cu after around 40 min and 279.33 mg/g for Zn after approximately 50 min. Through the high desorption capacity of Cu and Zn by ethylenediaminetetraacetic acid (EDTA), HP-Sn-MOF demonstrated excellent recyclability, maintaining a high removal efficiency of 89.83 % for Cu and 82.74 % for Zn over ten cycles. Coordination and electrostatic interactions were the primary mechanisms for Cu and Zn adsorption by the HP-Sn-MOF. These findings reveal the HP-Sn-MOF as a potential adsorbent for removing Cu and Zn from aqueous media. | en_US |