Composite membranes based on chitosan coated with organosilane by sol–gel

Synthetic products are becoming more popular in daily life as economic development levels rise. However, to create appropriate materials that may satisfy this need, researchers have been forced to concentrate on sustainable raw materials [1]. Therefore, this study focuses on the use of renewable raw materials to create novel CMs (composite membranes) with tailored properties for water purification [2-3]. Thereby, we propose a method for the modification of chitosan scaffolds by sol–gel, which can improve the stability of membranes. This method creates a one-phase solution when metal alkoxides and water react with an acid or base [4-5]. For the preparation of the CM coated with sol–gel, commercial chitosan (CC), TEOS (tetraethylortosilicate), and MPTMS (mercaptopropyl trimethoxysilane) were used. For chitosan dissolution, acetic acid was used. The chitosan membrane was coagulated in a sodium hydroxide solution and lyophilized, after which it was immersed into the mixture of silanes; the sol–gel reaction was performed in basic catalysis. A swelling study was performed at four values of pH (10 until 13) to determine if the chitosan membranes can withstand the basic conditions employed for the secondary step of coating by sol–gel. With the aim of highlighting the improvement inproperties for the CM, several characterization techniques were emplyed. FTIR spectra of the CMs confirmed the characteristic bands for chitosan and silane network, while TGA indicated that the CMs acquired higher thermal stability. SEM images confirmed that the chitosan membranes were coated with a thin sol–gel layer, and BET results highlighted the increase in the specific surface area and pore surface area after sol–gel coating of chitosan scaffolds; this indicates a potentially higher capacity for pollutant retention. New CMs based on chitosan coated with an organosilane layer, deposited by sol-gel, were developed. These materials show promising properties in terms of stability and capacity for pollutant adsorption, making them potential candidates for water purification.