Porous Poly(L-lactic acid) Nano Fibres Coated Chitosan and their Applications

Abstract

This thesis explain methods based on the coating of chitosan on porous poly(L-lactic acid) (PLLA) nanofibrous membrane for the production of high surface area adsorbents for the removal of toxic contaminants from aqueous solution. The surface modification of PLLA membrane by chitosan allowed heavy metals and dyes to attach on the adsorbent by electrostatic interactions. In order to achieve this, the chitosan was coated on porous nanofibrous support by three different methods: a) simple dip coating of pure chitosan porous membrane, b) chitosan grafted on polydopamine modified porous membrane and c) 3- aminopropyltriethoxysilane cross-linked chitosan coated on porous membrane. The prepared adsorbents in this work were designed to be used in the adsorption of impurities. Results showed that the use of such adsorbents can adsorb the large quantities of pollutants in less time reducing the costs and waste disposal. The chitosan used in this work was selected based on its biocompatibility, biodegradability, cost and availability from natural resources. Dopamine and 3-aminopropyltriethoxysilane were used to increase the adsorption sites and stability of chitosan in the aqueous solution. All materials were successfully immobilized on the porous support to produce large surface area adsorbent membrane. PLLA membrane was fabricated by electrospinning process and porosity was induced in the membrane via non solvent induced phase separation process and acetone treatment after electrospinning. This porous PLLA membrane was used as a support due to their high surface area, PLLA can be obtained from low cost renewable resources and it is biodegradable. The prepared adsorbent materials were tested in the removal of toxic ions and synthetic dyes from water solutions such as copper, methylene blue and rhodamine B. Batch experiments were carried out to determine the adsorption kinetics, equilibrium isotherm and thermodynamic parameters of adsorption copper ions, methylene blue and rhodamine B on prepared adsorbents. The experimental kinetic data were analysed using the pseudo first order, pseudo second order and inter particle diffusion models. The experimental isotherm data were analysed using Langmuir, Freundlich and Temkin isotherm models. Adsorption experiments showed that immobilization of chitosan on large surface area porous membrane improved their uptake efficiency and capacity. Finally, the regeneration of prepared adsorbent membranes was studied for five cycles. It was concluded that adsorbent was effective up to three regeneration cycles.

Date of Award	31 Dec 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Hugh Gong (Supervisor) & Jiashen Li (Supervisor)