Sustainable Process for Separating Chitin and Simultaneous Synthesis of Carbon Nanodots from Shellfish Waste Using 2% Aqueous Urea Solution

Abstract

This report describes a facile process for separating chitin and simultaneous synthesis of carbon nanodots (CNDs) from shellfish waste using 333.3 mol/m 3 (2 wt %) aqueous urea solution under hydrothermal conditions (at 150 °C for 1 h). In this process, urea functions as a denaturant and base precursor for the hydrolysis of proteins that are linked with chitin by the glycosidic ester bond. The hydrolyzed proteins in turn were used as a nitrogen-rich carbon source for synthesis of CNDs in the same pot. Additionally, this report describes a method for recovery of minerals from crab shell waste by gradient separation. The recovery of calcium carbonate in addition to chitin results in the reduction of acid consumption in the demineralization of crab shell and reduction in the evolution of carbon dioxide, a greenhouse gas. Transmission electron microscopy analysis on CNDs demonstrates the formation of quasi-spherical nanodots of size 7 to 15 nm. Solid-state NMR, Fourier transform infrared, inductively coupled plasma optical emission, and solid-state UV−visible absorption spectroscopic analyses, powder X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis studies as well as CHNS elemental analysis, confirm that better quality chitin is separated by this method in comparison to the chemical method that is widely used.

From Blue Bioeconomy toward Circular Economy through High-Sensitivity Analytical Research on Waste Blue Crab Shells

“…Furthermore, the CaCO 3 mineral obtained after all of the organic matter burning, but before calcium carbonate decarboxylation (at around 450 °C), could be of interest in pharmaceutical, paper, cement, and artificial stone industries. 17,44 From the blue bioeconomy perspective, modern global overview defines circular economy as an intentional reduction of aquatic waste to a minimum possible as well as reusing, repairing, refurbishing, and recycling existing materials and products. Moving toward a more circular economy, particularly in the seafood industry sector, it will reduce pressure on the environment; enhance security of supply of raw materials; increase competitiveness, innovation, and growth; and create new and more jobs.…”

“…After burning of the organic material, but before the start of chitin degradation (at around 220 °C), a bulk biomineral with a chitin network can be obtained, which could be potentially used as a nanofiber filter composite. Furthermore, the CaCO 3 mineral obtained after all of the organic matter burning, but before calcium carbonate decarboxylation (at around 450 °C), could be of interest in pharmaceutical, paper, cement, and artificial stone industries. , …”

The Food–Materials Nexus: Next Generation Bioplastics and Advanced Materials from Agri‐Food Residues

“…Deproteination takes place at very high pH, whereas demineralization is carried out in very acidic conditions. A typical chitin yield is 15-20 wt%, [250][251][252] or as low as 3 wt% in the case of cuttlefish bones. [253] Thus, many efforts are being directed to optimize the reaction conditions for chitin extraction and to match high-valued applications.…”

“…[261] However, the yield drops significantly if FLW are used as starting material (5-25% for ChNF and 10% for ChNC from shellfish-based FLW). [250][251][252] For instance, one kilogram of wet prawn residues yields only 90 g of dry matter after removal of meat tissue. Therefore, highly efficient and green isolation processes (e.g., urea-based hydrothermal treatment and others) still yield a low total ChNF < 5%.…”

“…Therefore, highly efficient and green isolation processes (e.g., urea-based hydrothermal treatment and others) still yield a low total ChNF < 5%. [252] Considering the low yield and harsh conditions often applied for isolation, efforts are in development to isolate biocolloids, including enzymatic routes to modify (deacetylate) chitin, [262,263] fractionation with acidic deep eutectic solvents, [260] and ball-milling pretreatments. [264] Process engineering simulation has been used to assess the techno-economic feasibility of ChNF and ChNC isolation from purified chitin.…”