A study on the interaction of marine diesel and beta-chitin and chitosan biopolymers

Abstract

Chitosan is a biopolymer obtained from chitin, a polysaccharide found in several organisms, including the endoskeleton of cephalopods. Among the cephalopods, individuals of Loliginidae family have a well-known economic importance and its collection and processing produces waste, such as its gladius, material rich in protein and beta-chitin. The amino groups present in chitosan confer binding capacity to metallic ions, proteins and lipids, and other analytes, such that is already being explored for treatment of industrial effluents and waters, and also studied for oil removal from water. It is noticed a relative lack of studies on chitosan obtained from beta-chitin, although it is known that the mild reaction conditions in its conversion result in higher molecular weight samples. Furthermore, due to the higher reactivity of beta-chitin compared to alfa-chitin, the most common form, it is possible prepare extensively deacetylated chitosans, which, together with its high molar mass, increases its binding capacity to different analytes. In this study, different potential sorbents - e.g. squid gladius (Doryteuthis plei and D. sanpaulensis), ²-chitin extracted from gladius and chitosan prepared from ²-chitin by deacetylation assisted by application of high intensity ultrasound irradiation - will be assessed for their ability to remove marine diesel from artificial salt water in simulated laboratory tests. Samples of gladius, ²-chitin and chitosan will be triturated into powder using a micro crusher. So, the powders will be sieved to determine the average grain size. The porosity, specific surface and morphology of all samples will be evaluated by mercury porosimetry, BET (N2 adsorption and desorption) and scanning electron microscopy, respectively. ²-chitin and chitosan will be also identified according to the mean degree of acetylation, molecular weight and viscosimetric properties. Then, a mixture of 40 mL of Milli-Q water, 3 mL of marine diesel oil and 3 g of sorbent will be prepared in triplicate and stirred for 15 min in 360 rpm. The suspension will be filtered off, the amounts of the remaining diesel in the solutions will be measured by the use of graduated cylinder and the capacity of oil removal will be calculated. In order to identify changes in the rates of oil removal due to salinity, the described procedures will be performed again (in triplicate), but using artificial salt water (approximate salinity = 30). The results will be described in relation to measures of central tendency and dispersion of data (minimum and maximum values, mean and standard deviation), and compared by factorial analysis of variance (ANOVA) in order to determine significant differences between the removal rates.