Methyldiethanolamine Solution Filtration Using Blended PVDF Membranes with Improved Antifouling Properties

Alkanolamine solutions are widely used to remove acid gases (primarily H2S and CO2) from natural gas and light hydrocarbon streams. Removal of impurities and entrained solids is crucial to the effective operation of gas-treating plants. In this work, flat sheet ultrafiltration membranes were prepared from a polyvinylidene fluoride (PVDF) backbone blended with polyethylene glycol (PEG) and polyacrylonitrile (PAN) using the phase inversion method. The influence of blending proportions on the morphology and antifouling properties of the membranes was investigated. The prepared membranes were characterized using scanning electron microscopy and contact angle measurements and their mechanical properties and porosity were also evaluated. Membrane performance tests were carried out using an unstirred laboratory scale dead-end filtration setup fed with deionized water and real industry lean methyldiethanolamine solution. It was found that applying the right amounts of PAN and PEG to the casting solution increases PVDF membrane water flux and enhances its mechanical and antifouling properties. The addition of 1 wt. % PAN and 2 wt. % PEG400 to the casting solution of PVDF membranes results in 18% increase in pure water flux and similar to 97% rejection of the solids in the amine solution. This accomplishment was ascribed to the increased porosity and surface hydrophilicity of the blended PVDF membranes. The membrane showed improved surface antifouling properties with a high flux recovery ratio of 85.6% and a low irreversible resistance of 0.14.