Investigating the Usability of Alkali Lignin as an Additive in Polysulfone Ultrafiltration Membranes

Abstract

The effects of natural and synthetic polymer additives on the properties of ultrafiltration membranes were studied. The use of NaOH to remove the residual additive remaining in the membranes during coagulation was also investigated, as was the effect of NaOH post-treatment relative to membrane performance. To evaluate the residual additives present, ATR-FTIR was used. Contact-angle analysis and water-absorption experiments were used to examine the hydrophilic properties of the prepared membranes. Membranes modified with lignin (Lig) were found to absorb more water (94% water uptake) than other membranes. In general, the contact angles were found to be low for membranes treated with NaOH. Membrane permeability was greatest in lignin_polysulfone (Lig_PSf), followed by polyvinylpyrrolidone_polysulfone (PVP_PSf), and with polyethylene glycol_polysulfone (PEG_PSf) the least permeable, similar to the trend observed in water uptake. A 'Robeson plot' analogue showed that Lig_PSf membranes had high separation factors regardless of the size of the solute being rejected. This study indicates the feasibility of using cheap, readily available additives to increase the performance of membranes.

Utilization of DES-Lignin as a Bio-Based Hydrophilicity Promoter in the Fabrication of Antioxidant Polyethersulfone Membranes

“…Ameliorating the performance of a membrane by using natural additives, such as lignin, which offers renewability, availability, and low cost advantages, is attentive due to environmental aspects in terms of biodegradability and of the reduction of membrane fabrication costs compared to synthetic additives [ 20 ]. In addition, it has been highlighted that polymeric hydrophilic additives like PEG might leach out from the membrane structure during membrane formation and filtration processes due to their affinity to water [ 20 , 21 , 22 ]. Leaching from the membrane structure can have detrimental health effects especially in the food separation industry, as it may interact with food materials.…”

“…Leaching from the membrane structure can have detrimental health effects especially in the food separation industry, as it may interact with food materials. Moreover, such additives are not the ideal ones in the modification of thin-film composite membranes, as a remarkable part of the weight of the thin film can be removed, which in turn reduces the half-life of the membrane [ 20 ].…”

“…In general, they report that both wettability and flux were reduced as the propionation of lignin increased in the fabricated nanocomposites [ 31 ]. Alkali lignin (28 kDa; 0.125 and 0.5 wt %) has also been used as an additive in the synthesis of an ultrafiltration polysulfone membrane [ 20 ], and the membrane morphology and performance, as well as the tensile strength, porosity, glass transition temperature, thermal properties, and other mechanical properties of the fabricated membrane [ 16 , 32 ], were studied and compared with PEG (10 kDa) and PVP (29 kDa) as the most two common additives used in membrane modification. It was found that alkali lignin improved the thermal stability and increased the bulk porosity and permeability of the prepared membranes.…”

“…It was found that alkali lignin improved the thermal stability and increased the bulk porosity and permeability of the prepared membranes. However, the alkali lignin-modified membranes revealed a high molecular cut-off value as the best separation factor (actual rejection of ∼ 93%) was obtained when PVP-360 kDa was utilized as a model compound [ 20 ]. Moreover, in another studies, alkali lignin (28 kDa) [ 33 ] and sodium lignin sulfonate [ 34 ] were utilized as additives in a polysulfone substrate layer of reverse osmosis membrane for forward osmosis (FO) applications.…”

Recycling Cellulase from Enzymatic Hydrolyzate of Laser-Pretreated Corn Stover by UF Membrane

“…The constituents included EG Ⅰ, EGⅡ, EGⅢ, CBHⅠ, CBHⅡ, and GB, which have molecular weights of 50, 46, 25, 65, 58, and 75 kDa, respectively . The hollow fibers were made of polysulfone with a molecular-weight cutoff (MWCO) of 30,000 Da (PS30) (Vilakati et al 2015).…”