Abstract
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•Leaching and dissolution treatment were used to recover cellulose form Banknotes.•Hydrolysis was used to reprocess the recovered cellulose into cellulose nanocrystals.•Structural and chemical analysis of cellulose nanocrystals was performed.•Cellulose nanocrystals with average size 75 nm and yield >97% were prepared.•The carbon footprint has been reduced by −7060 kg CO2-eq/ton.
Banknote printing is the industry that has a deep influence on financial operations on market, reflecting the economic performance of governments. Therefore, it is surrounded by a great secrecy even when dealing with production waste and end-of-life products, which are utilized very carefully by controlled combustion or incineration after crushing using special techniques designed to ensure that the waste does not come into possession by third parties. This waste contains significant amounts of cotton, percentage of which sometimes can reach up to 100% of the weight of banknote paper. It is clear that disposal of such waste by simply incinerating it is contrary to the principles of sustainability and preservation of resources. In order to achieve these principles, this research aims to develop a new strategy called “Banknote for Banknote (BFB)” to recover and refine cotton from Banknote waste and later reuse it in the production of banknote paper or reprocess it into cellulose nanocrystals suitable for use in many advanced applications through a sustainable technology. The experiments were performed only on the Banknote Production Waste (BPW) (which is estimated as ˜3% of the total volume of Banknote production) because the end-of-life banknotes are usually contaminated with many substances during the circulation. Some of them can become hazardous to the extent of being contaminated with drugs (e.g. cocaine, etc.); that requires many additional analyses and special treatment. In the developed technology BPW was treated by using five sequential processes that were selected based on the banknote design, structure, need to reach minimum gas emissions and high recovery rate. The technology began from crushing treatment at the Central Bank for safety reasons, then leaching process was used to dissolve the heavy metals from the ink layer (Al, Fe, Ni, etc.) and separate other pigment metal elements (Si, Ti, etc.) in the form of suspended particles, while the dissolution and bleaching stages were employed to dissolve the remaining organic components and purify the cotton substrate. Finally, acid hydrolysis was used to prepare Cellulose nanocrystals with average size 75 nm from the purified cotton. Although the experiments were conducted on Egyptian Banknote, the advanced technology is applicable to all types of cotton based-banknotes with high profitability.