Tamisolve® NxG as an Alternative Non-Toxic Solvent for the Preparation of Porous Poly (Vinylidene Fluoride) Membranes

Abstract

Tamisolve® NxG, a well-known non-toxic solvent, was used for poly(vinylidene fluoride) (PVDF) membranes preparation via a non-solvent-induced phase separation (NIPS) procedure with water as a coagulation bath. Preliminary investigations, related to the study of the physical/chemical properties of the solvent, the solubility parameters, the gel transition temperature and the viscosity of the polymer–solvent system, confirmed the power of the solvent to solubilize PVDF polymer for membranes preparation. The role of polyvinylpyrrolidone (PVP) and/or poly(ethylene glycol) (PEG), as pore former agents in the dope solution, was studied along with different polymer concentrations (10 wt%, 15 wt% and 18 wt%). The produced membranes were then characterized in terms of morphology, thickness, porosity, contact angle, atomic force microscopy (AFM) and infrared spectroscopy (ATR-FTIR). Pore size measurements, pore size distribution and water permeability (PWP) tests placed the developed membranes in the ultrafiltration (UF) and microfiltration (MF) range. Finally, PVDF membrane performances were investigated in terms of rejection (%) and permeability recovery ratio (PRR) using methylene blue (MB) in water solution to assess their potential application in separation and purification processes.

Advancements in Sustainable PVDF Copolymer Membrane Preparation Using Rhodiasolv® PolarClean As an Alternative Eco-Friendly Solvent

“…The additives employed are generally represented by PVP and PEG, even if some authors explored the use of Pluronic (PMMA) [18] and TiO 2 [52]. Other green or more sustainable solvents, such as triethyl phosphate (TEP) [54], Tamisolve NxG [4], γ-Butyrolactone [55] and propylene carbonate [55] have been used for the preparation of PVDF membranes by NIPS and TIPS. Besides the greener alternatives, traditional harmful solvents, such as DMF and NMP, have been widely investigated for the fabrication of PVDF membranes [56,57].…”

“…The performance of the membranes prepared with PolarClean in this work are comparable, or even better, with those of PVDF membranes prepared with other green or traditional solvents reported in the literature. Russo et al [4], for instance, prepared PVDF membranes (10 wt% of polymer) using Tamisolve ® NxG as a more sustainable solvent. The obtained UF membranes (pore size 0.06 µm) showed a water permeability of 88 L/m 2 h bar and an MB rejection of 79%.…”

“…Additionally, in this case, the link between the surface pore size and the membrane roughness is evident. Membranes with larger pores possessed higher roughness [4]. M11, in fact, presented the highest pore size (0.65 µm) and also the highest values of surface roughness (Sq: 152 nm, Sa: 120 nm, Sz: 936 nm).…”

“…Solvents are the major constituents of a polymer dope solution accounting for up to 80-90% of the whole solution. N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and N-methyl-2-pyrrolidone (NMP) are dipolar aprotic solvents, which are very effective in dissolving most of the polymers employed for the fabrication of polymeric membranes [4]. However, in view of the tighter environmental regulations adopted at national and international levels, the use of these solvents is becoming more and more restricted [5].…”

“…These solvents, in fact, can pose severe threats for human health and for the environment. NMP, for instance, is reprotoxic and irritating for the skin and eyes; DMF is hepatotoxic and reprotoxic [6], while DMA has also been categorized as a substance of very high concern due to its reproductive toxicity [4]. The use of these solvents, most of the times, is not merely confined to the preparation of the dope solution since their initial amount is completely found in wastewater after the coagulation and rinsing of the membrane [7].…”