Role of co-solvent concentration and stirring temperature in the preparation of native PVDF membrane for water purification

Abstract

Polyvinylidene fluoride (PVDF) membrane was considered economical for water purification due to its outstanding chemical resistance, good thermal stability, and high mechanical. The aim of this research is to fabricate PVDF membrane by incorporating varying the co-solvent concentration and investigated the stirring temperature during the preparation of the casting solution. Different solvents that included N-methyl-2-pyrrolidone (NMP) and Tetrahydrofuran (THF) were used to analyse their effect on the performance and morphology of the prepared membranes. A volatile co-solvent, THF was introduced into the casting solution by various loading in a range 5 % to 15 % in order to observe its effects on the formation of the top layer of the membrane to produce an integrally skinned asymmetric membra ne. Different stirring temperature in a range between 50 °C to 70 °C were used to investigate the membrane performance for water purification as the temperature can distributed the pores formation on the membrane. The membranes were prepared via non-solvent induced phase separation (NIPS) method. The fabricated membranes were tested for their permeability and rejection. The membranes were characterised by measuring its porosity, contact angle and membrane surface by using Scanning Electron Microscopy (SEM). The experimental results demonstrated that the PVDF membranes with permeability tests with 5 % and 10 % THF concentration at lowest stirring temperature, 50 ° C was the most permeable with 0.93 © L/m2.h.bar and 0.61 L/m2.h.bar, respectively while the rejection rate of methylene blue dye with 73 % and 61 % respectively. The membrane porosity was increased with increasing of stirring temperature and all the membranes have the contact angle below 90 ° which indicates the hydrophilic membrane. It can be deduced that 5 % and 10 % concentration of THF was the ideal loading to PVDF and 50 ° C stirring temperature was the best temperature in order to synthesis PVDF membrane to be used in water purification.