Sodium tripolyphosphate (TPP) crosslinked chitosan membranes and application in humic acid removal

Abstract

Macro- or micro-porous chitosan membranes have been utilized as adsorptive membrane for the removal of metal ions, organic macromolecules or bioseparation of protein mixtures. The removal or separation mechanism is not based on physical size retention but based on the high adsorption capability of chitosan to the target solutes. For this purpose, it is important that large macro or micro pores and high porosity are achieved for the membrane. However, the study on chitosan membrane for this purpose is very limited due to the difficulty in forming macro/micro pores and also the poor mechanical and chemical properties of chitosan. In order to form desired pores, we utilized polyethylene glycol (PEG) as porogen in the study. Coarse filter paper was employed to provide support. In order to improve the chemical stability of the resultant membranes, crosslinking reactions of chitosan with sodium tripolyphosphate (TPP) was carried out. The surface morphology, Dl water flux, and anti-acid ability of the resultant membrane was investigated. The results showed chitosan membrane prepared in the study can achieve the goal of adsorptive membrane as microporous surface and high porosity were successfully achieved. The crosslinking reaction successfully improved the anti-acid ability of chitosan membrane to pH 2. The application of chitosan adsorptive membrane in water treatment was carried out through removal of humic acid from water. The results showed efficient removal of humic acid was obtained. The effect of humic acid solution pH on removal efficiency and desorption of humic acid were also investigated.