Controllable conversion of shrimp shells into chitin or derived carbon material using acidic deep eutectic solvent

It is important to convert waste shrimp shells into chitin and its derivatives, but it still faces disadvantages of pollution and long process. In this research, deep eutectic solvents made from choline chloride (ChCl) and p-toluenesulfonic acid monohydrate (TsOH) were used to convert shrimp shells into chitin or carbon materials through adjustment of temperature with a dissolution-regeneration method in one step. Obtained precipitates and regenerated products gradually changed from chitin to carbon materials with the temperature adjusted to 130 °C and 110 °C, respectively. The α-chitin with the highest purity of 97.9 ± 0.1 wt% was prepared using 15 wt% ChCl/TsOH (1:2, n:n) aqueous solution at 70 °C, and the yield was 59.4 ± 1.9 wt%. Moreover, the carbon materials prepared by ChCl/TsOH (1:4) treatment with water and ethanol as anti-solvent were S/N/O-doped carbon materials, which exhibited potential in the supercapacitor with a specific capacitance of 24.8 and 19.3 F/g at 1 A/g, respectively.