Banana Pseudo-Stems save the World with help of Ionic Liquid
Shogo IWATA1, Romain MILOTSKYI1, Tetsuo FUJIE1, Naoki WADA1, Kenji TAKAHASHI1
1Kanazawa University, Kanazawa, Japan
The cellulose source should be sustainable, in particular to the upgrading of agricultural waste into value-added materials toward a circular economy. An excellent example of agri-food waste that would be employed for this purpose is banana pseudo-stems. Banana trees exhibit rapid growth compared to woods, and once become fruit-yielding, the stalk is cut back and the pseudo-stem is discarded, representing an untapped source of cellulosic materials. Importantly, banana fiber can be obtained from banana pseudo-stems, which could provide a steady income for workers in countries such as Zambia, Africa.
Following the discovery of ionic liquids (ILs) as novel, green solvents 20 years ago, shaping of cellulose into functional materials has entered a new era of development. More specifically, over the past few decades, numerous efforts have been devoted to the development of renewable materials and energies based on IL/cellulose processing systems. We focuses on the development of sustainable polymeric materials based on green chemistry, and summarizes our recent progress in the use of properly designed ILs as organic catalysts and solvents for homogeneous reactions of cellulose, and also advanced technologies with exploiting the unique properties of ILs for the scalable production of lignocellulosic materials.
In 2015, our group demonstrated a facile homogeneous transesterification reaction of cellulose with isopropenyl acetate in 1-ethyl-3-methyl-imidazolium acetate (EmimOAc) to yield cellulose triacetate without any additional catalyst or corrosive chemicals. This synthetic strategy was found to be applicable to various polysaccharides, and it was verified that the EmimOAc could be easily recycled at least four times with a good recovery ratio (≥96 wt.%) and without any obvious decrease in its catalytic activity.
We have applied those catalytic activities of EmimOAc to synthesis of Banana ester materials. The Banana fibers are consisted from 40% cellulose, 12% hemicellulose and 6% lignin. The Banana pseudo-stems are kindly donated from One Planet Café. It was found that the polysaccharide derivative from the Banana fibers, which constituted a mixture of cellulose and hemicellulose propionate, exhibited comparably better mechanical properties and a superior thermal processability for injection molding than those obtained from similar cellulose ester originating from wood pulps.
This work is funded by the Japan Science and Technology Agency (JST) (grant number JPMJPF2102) and the Japan Society for the Promotion of Science (JSPS) KAKENHI (grant numbers 18H02253 and 22H02404)