Gizem Tuncay’s research while affiliated with Istanbul Technical University and other places

Hollow fiber membranes have higher surface area and are easy to be applied in systems. Because of theirs self‐supporting construction, they have limited mechanical durability. By reinforcing these membranes with a braid, the mechanical strength can be improved. In this study, the impact of polyvinyl pyrrolidone (PVP) as a pore‐forming additive with different contents on the fabrication of polysulfone braid reinforced hollow fiber membranes was investigated both as a ultrafiltration membrane and as a support for the fabrication of thin film composite (TFC) nanofiltration membranes. Characterization and filtration studies of all membranes were performed to examine membrane performance. It was discovered that the porosity and hydrophilicity of the ultrafiltration membranes were enhanced by enhancing PVP concentration, thus increasing the pure water flux in the membranes. As regards to results of fabricated TFC membranes, salt rejections were increased with increasing PVP ratios. The rejection efficiency of magnesium sulfate and sodium chloride was found to be approximately 80% and 49%, respectively, when a PVP ratio of 8% was used.

In the current study, braid reinforced membranes were fabricated from polyvinylidene fluoride (PVDF) polymers with two different molecular weights, and the blending of the polymers in a 1:1 ratio to upgrade the performance of the membrane. Characterization, filtration studies, and membrane bioreactor (MBR) application were done to evaluate membrane performance by applying the same operation conditions on each membrane. Characterization studies indicated that the fabricated membrane from blending polymers was a hydrophilic structure with a contact angle of 50.78° and smoother surface properties compared to the other fabricated membranes. According to the MBR results, at the end of the operation process, TMP levels of the membrane from the blending method are found 150 mbar, membrane from high molecular weight PVDF polymer had 250 mbar, and membrane from low molecular weight PVDF polymer had 800 mbar. As a consequence of the investigation, it is seen that the hydrophilic structure of the membrane allows the pollutant to adsorb less to the blend membrane surface, and the lower roughness is also a factor in reducing fouling.

This study describes the synthesis and characterization of Fe3O4@Xanthan gum (XG) nanocomposite with increased hydrophilicity and anti-bacterial properties, and its application in the fabrication of nanocomposite-based mixed matrix polyvinylidene fluoride (PVDF) membrane using the phase inversion method. The Fe3O4@XG was synthesized by the in-situ co-precipitation technique. The characteristics of the membranes were investigated in terms of morphology, dye and BSA removal performance, anti-fouling behavior, and anti-bacterial properties. The incorporation of very small amounts of Fe3O4@XG NPs, i.e. 0.1 and 0.2 wt%, improved 5% and 17% water flux of the PVDF nanocomposite membranes due to the increased membrane hydrophilicity. Most particular, 0.5 wt% Fe3O4@XG/PVDF membrane was revealed a maximum water flux of 167.2 L·m⁻²·h⁻¹ at 3 bar, which was 52% greater performance than the pure PVDF membrane. Reactive Black 5 and Reactive Red 120 dye rejections were enhanced from 77.6 to 84.8% and 66.6 to 73.8% respectively in 0.2 wt% Fe3O4@XG/PVDF membrane compared to the pure PVDF membrane. The best anti-fouling performance was also exhibited by 0.2 wt% Fe3O4@XG/PVDF membrane with an increased FRR value (66.5%) compared with the pure one. In addition, the results of the anti-bacterial test with E. coli showed that the anti-bacterial capabilities of the Fe3O4@XG/PVDF membranes were remarkable and have resisted contamination.

Rare earth elements or REEs are a vital and irreplaceable part of our modern technological and digital industries. Among the REEs that are the most critical to be recovered are Ce, La, and particularly, Nd, and Y, due to high demand and at a potential future supply risk. Innovative techniques must be considered to recover REEs from secondary resources. In this study, REEs are extracted from iron mining sludge from Central Anatolia in Turkey. Two different acid solutions were compared, one with a higher acid content (120 ml HCl and 80 ml HNO3 per liter) and one with lower acid content (20 ml HNO3 per liter). Nanofiltration, as a process to concentrate the acidic leachate and increase the REE concentration, was carried out at pH levels of 1.5, 2.5, and 3.5 and under 12, 18, and 24 bar operating pressures. SLM studies had been carried out using a PVDF membrane with a pore diameter of 0.45 μm, with three different carriers to separate the REEs from other major elements in the concentrated leachate. Through this analysis, the optimum operating conditions for nanofiltration are at pH 3.5 at 12 bar, using the leach with low acidity, achieving about 90% recovery efficiency of the REEs. SLM studies using 0.3M D2EHPA, with a 3-h reaction time, showed the highest mass flux values for the REEs. Nanofiltration and SLM represent novel methods of REE concentration and extraction from iron mining sludge.