Ultrasonic irradiation as a mild and efficient protocol for the demineralization of chitin from shrimp shell wastes

Chitin is conventionally isolated under harsh reaction conditions through two constitutive steps deproteinization and demineralization. This paper considers a protocol for chitin's isolation from shrimp shell waste. Ultrasonic irradiation was employed as an effective technique for the isolation process at a mild reaction condition with dilute solvents, a lower temperature and shorter reaction times compared to the conventional one. Shrimp shells wastes were pretreated by washing, grinding and sieving. The grounded shells were deproteinized with 2 M sodium hydroxide solution and followed by demineralization using 1 M hydrochloric acid. The mechanisms by which the demineralization occurs in the deproteinized shells were described using a simple decomposition model. Quantitative mineral analysis was performed by titrimetric at different temperatures 40, 50, 60, and 70 °C under constant ultrasound power and frequency. The results indicated that the protein content significantly reduced to 0.87% w/w when the highest NaOH concentrations were reached. At the same time, the ultrasound assists demineralization, resulting in the lowest mineral content of 1.29% w/w. This work also effectively demonstrates the kinetic model that occurs through the demineralization, in which reaction rate,dCaCO3dt=−k2K1CCaCO3(1+2K1CCaCO3) and k2=Ae−EaRT are an excellent model to describe the process. In this work, the physicochemical characterization showed that the properties of isolated chitin were not much influenced by the ultrasonic treatment, which has the same characteristics as the commercial product.