Preparation and Preliminary Evaluation of Chitosan–Tripolyphosphate–ZnO Bionanocomposite Membranes for Methylene Blue Removal

Abstract

Chitosan-based films provide a biodegradable polymeric platform for the preparation of composite membranes through ionic crosslinking and the incorporation of inorganic materials. In this study, a chitosan–tripolyphosphate–zinc oxide (CTPP-ZnO) bionanocomposite film was prepared using chitosan dissolved in 2% acetic acid, followed by mixing with zinc oxide and crosslinking with sodium tripolyphosphate at approximately pH 5.0. The resulting mixture was cast and oven-dried to obtain a CTPP-ZnO membrane. The crosslinking mechanism is based on electrostatic interactions between protonated amino groups of chitosan and negatively charged phosphate groups of tripolyphosphate, while the β-1,4-glycosidic backbone of chitosan remains the principal structural framework of the polymer. Morphological characteristics of the prepared material were examined using scanning electron microscopy. A preliminary membrane-performance test was also conducted by passing a 4 ppm methylene blue solution through the membrane under a pressure of 10 bar. The observations support the formation of a cross-linked chitosan-based matrix containing zinc oxide and indicate morphological differences between chitosan and the composite film. However, the available measurements do not quantitatively distinguish dye adsorption, pressure-driven separation and photocatalytic degradation. Additional physicochemical, structural and membrane-performance characterisation is therefore required to establish the contribution of zinc oxide and tripolyphosphate to the functional properties of the composite. The study demonstrates a simple preparation approach for a chitosan-based composite film intended for further investigation as a functional membrane material.