Sustainable, biodegradable, and recyclable bioplastics derived from renewable carboxymethyl cellulose and waste walnut shell
Yangyang Qian, Changpei Qin, Jianqiang Zhang, Bingfei Shi, Yuan Wei, Chunyu Wang, Jingchao Niu, Shimin Kang, Gang Chen, Yijun Liu
Abstract
Manufacturing water-stable carboxymethyl cellulose (CMC) films as an alternative to commercial plastics is a promising solution to address plastic pollution. In this study, waste walnut shell (WS) was used as a natural lignocellulosic filler, glycerol as a plasticizer, and citric acid (CA) as a crosslinking agent for preparing high-performance CMC-based bioplastics through a one-pot casting method. When WS content was 12 wt%, the obtained CWGA-12 after optimization exhibited excellent mechanical properties (tensile strength ≈18.53 MPa, fracture strain ≈78.11 %), low surface roughness (< 16 nm), high optical transmittance (82.23 %), and superior thermal stability. Moreover, CWGA-12 could not decompose within 7 days of immersion in water, or even after 5 h of continuous stirring at 60 °C, while it could be reused after crushing, dissolving, and re-pouring under alkaline conditions. The alkali-recycled CWGA-12 exhibited a better UV-blocking capacity than before (99.22 % for UVA and 99.95 % for UVB). In addition, our bioplastic also had excellent biodegradability and disappeared completely after 2 days in rainy weather. Thus, our work not only offers an innovative approach to producing petroleum-based plastic substitutes with outstanding water resistance and UV-blocking properties but also paves the way for WS waste's broader applications.