Enhancing the performance of polybenzimidazole membranes for organic solvent nanofiltration

Abstract

Organic solvent nanofiltration is a thriving alternative liquid-liquid membrane separation method. However, the process faces different challenges and one of them is the weak solvent resistance of the membranes and the low permeance of the crosslinked membranes. The aim of this work to enhance the permeance of OSN membranes in dipolar aprotic solvent. To overcome this problem, chemical stabilisation of membranes has been carried out on a PBI-PIM type polymer-blend membrane. The high internal volume of the PIM polymer increased the originally low permeance of the PBI. The permeance results range between 0.5–2.5 L m-2 h-1 bar-1 and the MWCO results range between 190–600 g mol-1. In terms of permeance and MWCO, the PIM-amine containing PBI polymer blends show superior performance over the PIM-COOH containing ones. The 12% PIM-amine containing membrane has an outstanding permeance value with 2.0 L m-2 h-1 bar-1 in DMF, which is slightly higher than the previously reported crosslinked PBI membranes. Using a model reaction and IR spectroscopy, the chemical crosslinking has been rejected and the stability of the membrane assigned to salt formation. AFM-IR, SEM and contact angle measurement have been used to characterise the imperfect membranes. On top of this, they have been used to characterise the morphology of the membranes and provided further evidence to explain the improved properties. In terms of the increased permeance and stability result can offer alternative solutions for industrial separation processes.

Date of Award	31 Dec 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Krishna Persaud (Supervisor) & Gyorgy Szekely (Supervisor)