Poly(Vinylidene Fluoride) (PVDF) Based Hydrophilic Hollow Fibre Membranes - Prospects for Wastewater Treatment

摘要

The growing need for suitable water resources has attracted attention to new water and wastewater treatment processes, such as membrane filtration. Due to the excellent properties of poly(vinylidene fluoride) (PVDF) polymer and membranes, such as excellent chemical and thermal resistance along with great mechanical strength, the PVDF membrane is a suitable candidate for the water and wastewater industry. As a result, there have been many attempts to improve the performance of PVDF membranes, particularly in terms of water flux and fouling resistance, in order to increase the membrane’s lifespan and reduce operating costs. This thesis explores such PVDF membrane performance improvements through hydrophilic modification of the bulk membrane. In this study, the recently developed process of atom transfer radical polymerisation (ATRP) was used to graft hydrophilic chains of poly(ethylene glycol) methyl ether methacrylate (POEM) onto the backbone of the PVDF polymer to synthesise an amphiphilic copolymer (PVDF-g-POEM). A new, environmentally-friendly and cost-effective method was introduced to purify the synthesised amphiphilic copolymer by using water instead of volatile solvents. The amphiphilic copolymer was used as a blend in the spinning dope and the effect of blending this amphiphilic copolymer on the prepared hollow fibres was studied in detail. A wide range of hydrophilic PVDF based hollow fibres was achieved by changing the spinning parameters and dope compositions. Moreover, nano-sized γ-Al2O3 particles were used as an additive to improve PVDF flat sheet membranes. By using alumina particles, the filtration performance, surface hydrophilicity and fouling resistance of membranes improved significantly. In addition, by using triethyl phosphate (TEP) as the solvent, PVDF hollow fibre membranes with interconnected pore structures were produced via a single step immersion precipitation technique. The resultant PVDF hollow fibre membranes displayed excellent mechanical properties because of their macro-void free structures. Polyethylene glycol (PEG) was used as an additive to improve the water flux of the produced membranes and PVDF hollow-fibre membranes suitable for water and wastewater treatments in the range of ultrafiltration were obtained.