Influence of hydrolysis conditions and membrane casting on quality of regenerated cellulose membrane

Cellulose microfiltration membranes are widely used in various applications such as wastewater treatment, protein and enzyme filtration. Unfortunately, the poor solubility of cellulose makes it challenging to control membrane manufacturing. To overcome this limitation, in this study, Cellulose derivative membranes were cast and later on deacetylated via hydrolysis with alkali solutions. To achieve the desired macrostructure, different compositions of the casting solution were investigated. Sample membranes were prepared using a semi-automatic casting method on nonwoven support using the Non-solvent Induced Phase Separation (NIPS) method. The coagulation bath was consisting of weak non solvent with the addition of low percentage of solvent and strong non-solvent. Hydrolysis was performed in different stages of the membrane preparation. The best results were obtained when deacetylation was performed on the completely formed membrane. Accelerated regeneration of membranes could be obtained by increase of solution alkalinity. However it can cause irreversible damage to the membrane structure. To maintain the membrane's macrostructure, regeneration at higher temperatures was found to be highly effective, especially when combined with high concentrations of the alkali solution. Since hydrolysis impacts the porosity of the base membrane, adjustments such as decreasing the polymer concentration and employing a mixture of medium and high molecular weight polymer were made in the casting solution to enhance the final structure. The resulting membranes were characterized in terms of their morphology (SEM); physical (air flow, thickness, etc.), and chemical properties (contact angle, FT-IR; etc.). Obtained regenerated cellulose membrane showed 98% deacetylation (FT-IR analysis) with adequate morphology, high hydrophilicity and low protein binding.