Development of Antifouling Polysulfone Membranes by Synergistic Modification with Two Different Additives in Casting Solution and Coagulation Bath: Synperonic F108 and Polyacrylic Acid

This study deals with the development of antifouling ultrafiltration membranes based on polysulfone (PSF) for wastewater treatment and the concentration and purification of hemicellulose and lignin in the pulp and paper industry. The efficient simple and reproducible technique of PSF membrane modification to increase antifouling performance by simultaneous addition of triblock copolymer polyethylene glycol-polypropylene glycol-polyethylene glycol (Synperonic F108, Mn =14 × 103 g mol−1) to the casting solution and addition of polyacrylic acid (PAA, Mn = 250 × 103 g mol−1) to the coagulation bath is proposed for the first time. The effect of the PAA concentration in the aqueous solution on the PSF/Synperonic F108 membrane structure, surface characteristics, performance, and antifouling stability was investigated. PAA concentrations were varied from 0.35 to 2.0 wt.%. Membrane composition, structure, and topology were investigated by Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The addition of PAA into the coagulation bath was revealed to cause the formation of a thicker and denser selective layer with decreasing its pore size and porosity; according to the structural characterization, an interpolymer complex of the two additives was formed on the surface of the PSF membrane. Hydrophilicity of the membrane selective layer surface was shown to increase significantly. The selective layer surface charge was found to become more negative in comparison to the reference membrane. It was shown that PSF/Synperonic F108/PAA membranes are characterized by better antifouling performance in ultrafiltration of humic acid solution and thermomechanical pulp mill (ThMP) process water. Membrane modification with PAA results in higher ThMP process water flux, fouling recovery ratio, and hemicellulose and total lignin rejection compared to the reference PSF/Synperonic F108 membrane. This suggests the possibility of applying the developed membranes for hemicellulose concentration and purification.

Aqueous Lithium Carboxymethyl Cellulose and Polyacrylic Acid/Acrylate Copolymer Composite Binder for the LiNi0.5Mn0.3Co0.2O2 Cathode of Lithium-Ion Batteries

Water-soluble green cathode binders are developed to increase the performance of 18650 type LiNi0.5Mn0.3Co0.2O2 (NMC532) lithium-ion batteries (LIBs). Using four basal substances to prepare the composite binders, it is indicated that the cathode with lithium carboxymethyl cellulose (CMCLi)-polyacrylic acid/acrylate copolymer (type 306F) composite binder (Marked as Binder C) avoids the corrosion of aluminum substrate, and exhibits stronger adhesive force and better electrolyte adsorption capacity compared to other cathodes with PVDF binder and single aqueous binders. In particular, the electrochemical performance of the batteries with Binder C is also improved, initial specific capacity of 161.5 mAh g-1 at 0.2 C and retention capacity of 88.9% at 1 C after 1200 cycles are obtained. The batteries with Binder C also exhibit enhanced high-temperature storage performance, there is 97.9% residual capacity when the fully charged batteries are stored in 60 °C for 14 days. The enhanced performance is mainly attributed to the chemical stability and bonding ability of polyacrylic acid/acrylate copolymer and better conduction at the liquid-solid interface caused by CMCLi. These results indicate that Binder C has promising application prospects in the NMC532 cathode, and also provide a reference for the green production of NMC-based LIBs.