Novel method of synthesizing poly(ether sulfone) membranes containing two solvents and a lithium chloride additive and their performance

Abstract

The influence of a lithium chloride (LiCl) additive on poly(ether sulfone) (PES) membranes was investigated. A microwave technique was used to prepare membrane dope solutions, and two different types of solvent systems were used: single-solvent (SS) and double-solvent (DS) systems. In the SS system, PES was dissolved in N,N-dimethylformamide (DMF), and In the DS system, PES was dissolved in DMF and acetone. In the DS system, the control ratio of DMF to acetone was kept at 3.47, and the concentration of LiCl in both solvent systems was varied from 1 to 4 wt %. We observed that the microwave technique was able to dissolve the polymer rapidly, in less than 1 h. The performance of the PES membrane was evaluated in terms of poly(ethylene glycol) separation and molecular weight cutoff (MWCO). The results reveal that the presence of LiCl improved both the flux and rejection rates, and its concentration was best kept at 3 wt % for the tested conditions. In addition, we found that the mean pore size of the membranes produced from the DS system was smaller and the MWCO was lower as compared to the SS system.

Influence of sodium bromide additive on polyethersulfone ultrafiltration membranes

“…However, higher amount of NaBr does not promote the hydrophilic properties as exhibited by its low flux rates probably owing to the formation of salt–solvent complexes which diffused out during the phase inversion process. Similar findings38 were also reported that LiCl and DMF formed salt–solvent complexes which resulted in hydration effect and caused swelling in the polymer gel 41…”

“…The permeation rates of commercially available spiral wound membranes can range from as low as 4.5L/m 2 h to as high as 53 L/m 2 h as listed in Table II. N‐1 membrane also exhibited higher PWP compared to membrane with highest PWP in the dual solvent system as reported in our previous study, which used LiCl as salt additives 38…”

“…These lyotropic salts are known to form complexes with the carbonyl group in polar aprotic solvents such as with acetone, dimethylacetamide, N, N ‐dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and N ‐methylpyrrolidinone through ion–dipole interaction. Low‐molecular‐weight inorganic salts such as lithium chloride (LiCl),37–40 lithium fluoride (LiF),40 lithium bromide (LiBr),3,40 zinc chloride (ZnCl 2 ),33 magnesium chloride (MgCl 2 ), calcium chloride (CaCl 2 ), magnesium perchlorate (MgClCO 4 ), and calcium perchlorate (CaClCO 4 )41 are some of the other less common additives used.…”

“…However, the use of halogenated‐based additives in membrane production has not been widely explored and reported compared to additives such as PEG and PVP. Nevertheless, extensive studies on the effect of LiCl additive on the membrane were reported37–40 and the addition of LiCl as additive was found to effectively enhance the vapor permeability of the membrane 38. The rheological behavior of polyether sulfone polymer solution which consisted of LiBr additives,40 as well as the performances of membranes containing various amounts of LiBr, LiCl, and LiF additives were systematically studied 40.…”

Novel dual-layer hollow fiber membranes applied for forward osmosis process

“…5. These observations were believed to be associated with the change in the thermodynamic properties and phase inversion kinetics of the PES systems without and with the addition of an additive [20,31]. Hansen solubility parameter for each component in PES system is summarized in Table 3, from which the total solubility parameter difference can be derived (Table 4).…”