Liu Xue,Li Hang,Dai Jun-Xiang,Tian Guo-Qiang,Chen Si-Chong,Wu Gang,Wang Yu-Zhong
Poly(lactic acid) (PLA), a bio-based polymer, is considered to be a sustainable alternative to conventional petroleum-based plastics. However, owing to its widespread use and relatively slow degradation rate in water, PLA still poses potential environmental pollution risks after being discarded. The efficient chemical recycling of PLA represents an attractive approach to addressing both resource reuse and environmental pollution challenges caused by its waste. Hydrolysis is the predominant method of industrial recycling. However, because PLA is insoluble in water, efficient heterogeneous hydrolysis requires high-temperature and high-pressure conditions. In this study, an efficient homogenous hydrolysis method capable of simultaneously dissolving PLA and calcium hydroxide (Ca(OH) 2 ) was developed. Suitable solvents for this method were screened, and it was found that PLA hydrolysis using dioxane and 1,4,7,10,13-Pen-taoxacyclopentadecane as solvents achieved conversion rates of 93% and 90%, respectively, within 2 h at room temperature. Notably, the hydrolysis product, calcium lactate, precipitated as a solid from the solvent and therefore self-separated from the reaction solution. The solvent, acid/base conditions, water content, and depolymerization kinetics were investigated. Compared with previously reported hydrolysis methods, the enhanced efficiency observed in this study can be attributed to the concurrent solvation of PLA and Ca(OH) 2 , which maintains homogeneity throughout the reaction process. Additionally, this method facilitates closed-loop recycling of PLA and is compatible with the highly selective recovery of PLA from various types of PLA products.
Chao Han,Shibin Nie,Zegong Liu,Song Liu,Hong Zhang,Jiayi Li,Haoran Zhang,Zihan Wang
In order to address the environmentally friendly issue of fire prevention and extinguishing materials in coal mines, A new biomass sodium alginate gel foam (SC-GF) was prepared by using sodium alginate (SA), calcium L-lactate (CL), alkyl glycoside (APG) and tea saponin (TS). The effect of different concentrations of CL on the properties of SC-GF was analyzed by studying the gelation time, foaming volume and half-life of the SC-GF. The results show that the gelation time of SC-GF is successfully controlled by using the weak electrolyte CL as the cross-linking agent. When SA: CL: APG: TS = 4 : 1 : 2 : 1, the gelation time of SC-GF is 10 min with half-life of 16 days. Furthermore, A metal coordination bond favorable to the stability of SC-GF is formed by the carboxylate ion of α-L-gulonic acid in SA and Ca 2+ ionized by CL. SC-GF exhibits excellent fire prevention and extinguishing properties. The CO concentration of the coal sample treated with SC-GF decreases from 7556.8 to 34.92 ppm in the process of oxidation at room temperature for 48 h. The temperature-programmed oxidation test shows that SC-GF can delay the accelerated oxidation temperature from 120 to 160 °C, and the CO inhibition rate is as high as 60.5 % at 200 °C. The fire extinguishing test indicates that SC-GF can significantly reduce the temperature of the coal sample and extinguish the coal fire quickly. The study is useful to develop efficient and environmentally friendly coal mine fire prevention and extinguishing materials.
危险品化学品经营许可证（带存储）