Efficient Hydrolysis of Poly(lactic acid) at Room Temperature to Recycle Self-separated Calcium Lactate

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.