Physicochemical and Colligative Investigation of α (Shrimp Shell)- and β (Squid Pen)-Chitosan Membranes: Concentration-Gradient-Driven Water Flux and Ion Transport for Salinity Gradient Power and Separation Process Operations.

Abstract

Chitin, and its derivative chitosan, is a naturally occurring biopolymer and an abundant polysaccharide containing acetylated units of N-acetyl-d-glucosamine. Chitosan membranes produced from shrimp shell (α) and squid pen (β) biowaste were prepared by solvent-casting, after which water flux and ionic transport diffusion experiments were conducted using a side-by-side concentration test cell under differing salinity concentration gradients. Physicochemical and experimental investigations were conducted, which confirmed that β-chitin possesses differing and enhanced performance characteristics than α-chitin with respect to diffusive water flux and ionic transport capabilities. In addition, novel colligative investigations through osmotic equilibrium were conducted to determine electrochemical characteristics for the evaluation of salinity gradient power generation suitability. Electrochemical test results under a salinity gradient revealed extremely low energy density values, thereby limiting consideration for commercial utility-scale salinity gradient power renewable energy operations. However, the tested membranes possessed high water and ion flux permeability characteristics that could find use in industrial separation process operations such as those used in the extraction of economically valuable materials from seawater or highly saline industrial fluids, or reduction in the saline content of mining fluids during dewatering and hazardous waste treatment and disposal operations, thereby potentially fostering new market developments, which will drive continued improvements in the responsible biowaste management of this valuable marine bioresource.