Pilot scale nanofiltration membrane fabrication containing ionic co-monomers and halloysite nanotubes for textile dye filtration.

Wastewater from the textile industry contains high concentrations of pollutants, so the wastewater must be treated before it is discharged. In addition, the reuse of treated wastewater should be considered from an environmental point of view, as large volumes of wastewater are produced. Since textile wastewater mainly contains dyestuffs, it must be treated effectively using environmentally friendly technologies. Membrane processes are widely used in textile wastewater treatment as they have distinct advantages over conventional wastewater treatment methods. This study reports the pilot-scale manufacturing and characterization of three different NF membranes. Three different types of membranes were fabricated. The fabricated membranes were compared through characterization by surface properties, chemical structure and morphology. Membranes were tested for pure water flux. Then the synthetic wastewater (SWW) was tested for flux and rejection. Lastly, the textile wastewater was tested. The textile wastewater flux of pure piperazine (PIP), 60% S-DADPS and 0.04% halloysite nanotubes (HNTs) were 22.42, 79.58 and 40.06 L m-2 h-1. It has been proven that the 60% s-DADPS membrane provides up to four times improvement in wastewater flux and simultaneously. In addition, NF membranes produced using HNT and sDADPS on a pilot scale have brought innovation to the literature with the good results obtained.

Investigation of different molecular weight Polyvinylidene Fluoride (PVDF) polymer for the fabrication and performance of braid hollow fiber membranes.

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.

Polysaccharides in fabrication of membranes: A review.

Sustainability concerns have motivated and directed a great deal of interest over the past decade towards the development of green technologies. Polysaccharides are green polymers, which experienced growing demand to substitute chemically synthetic polymers. Different types of polysaccharides i.e. cellulose-, starch-, chitin- alginate-, and chitosan-based carbohydrate polymers have been applied in the fabrication of separation membranes. The purpose of the current review was to summarize, classify, and discuss the state-of-the-art the fabrication of membranes with carbohydrate polymers. Specific attention was paid to highlight the strategies used in the successful development of such membranes. First, a brief review of different types of polysaccharides was performed. Next, the application of these polysaccharides in the fabrication of liquid filtration, gas separation, adsorption, pervaporation and proton exchange membranes were comprehensively reviewed. Computational evaluations were also reviewed. Eventually, concluding remarks together with challenging aspects of the future perspective over application of polysaccharide membranes were discussed.

Nanofiltration membranes for salt and dye filtration: effect of membrane properties on performances.

In this study, commercial nanofiltration membranes (Toray, NF 270, Desal 5 L) were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, optical profilometry, contact angle, mechanical strength and zeta potential measurements. Filtration performance tests were conducted with distilled water, MgSO4 solution and synthetic dye solutions, respectively. Among three commercial membranes, the Toray membrane was thought to be better choice. Additional experiments were carried out for a more detailed characterization of the selected membrane. Therefore, firstly, flux and removal efficiency was monitored by using dye solutions at different pH values, and then experiments were carried out to observe the effect of different temperatures. Also, another filtration test with NaCl solution was performed for the Toray membrane. As the main purpose of this study, we aimed to establish a significant correlation between the structural properties of membranes and their performances. In light of the results obtained, it was observed that the contact angle, mechanical strength and surface roughness values of the membrane significantly affected the membrane performance. It was concluded that the most important parameter in dye removal was the zeta potential. As a result of this work, a data set of commercial membranes was created and is available to all membrane users.

Halloysite nanotube blended nanocomposite ultrafiltration membranes for reactive dye removal.

In this paper, ultrafiltration (UF) flat sheet membranes were manufactured by introducing two diverse halloysite nanotubes (HNT) size (5 µm and 63 µm) and five different (0, 0.63, 1.88, 3.13, 6.30 wt %) ratios by wet phase inversion. Some characterization methods which are contact angle, zeta potential, viscosity, scanning electron microscopy (SEM) and Young's modulus measurements were used for ultrafiltration membranes. Synthetic dye waters which were Setazol Red and Reactive Orange were used for filtration performance tests. These dye solutions were filtered in three different pH conditions and three different temperature conditions for pH and temperature resistance to understand how flux and removal efficiency change. The best water permeability results were obtained as 190.5 LMH and 192 LMH, for halloysite nanotubes (HNT) sizes of 5 µm and 63 µm respectively. The best water and dye performance of UF membrane contains 1.88% w/w ratio of HNT, which showed increased water flux and dye flux of membranes according to different HNT concentrations including ultrafiltration membranes.

Fabrication and characterization of polysulfone reinforced hollow fibre membrane.

In this study, reinforced hollow fibre membranes were fabricated using different molecular weights of polyvinylidene prolidone (PVP Mw: 10, 40 and 360 kDa) and different take-up speeds (1, 2, 2.6 and 3.5 m/min). Prepared reinforced hollow fibre membranes were characterized in terms of permeability; surface morphology and hydrophilicity; pore size distribution; bovine serum albumin (BSA) rejection and flux recovery ratio. Optimum permeability and BSA rejection were obtained when PVP molecular weight was 40 kDa. After PVP molecular weight determination, advancing speed was changed and it was seen that increasing advancing speed ended up with decreased membrane wall thickness; however, decreased wall thickness increased the probability of irreversible fouling.

Effect of wetting agent on the dye filtration performance of ultrafiltration membrane.

In this study, the wet phase inversion method was used for fabrication of the flat sheet ultrafiltration (UF) membranes. Three different polymer types and two different wetting agents were used for the fabrication. The effect of polymer types and wetting agents were investigated on the structural and dye performance of casted membranes. Two different synthetic dyes, 100 ppm Setazol Red and 100 ppm Setazol Blue, were used for the performance test. Viscosity, contact angle, and molecular weight cut off (MWCO) of casted membranes were measured and an electro kinetic analyzer, dynamic mechanical analyzer (DMA) and scanning electron microscope (SEM) were used to determine the structural properties. While the highest water and dye permeability were obtained with PES-PEG membrane, PSf-plain membrane gave the highest removal efficiency for Setazol Red and Setazol Blue dyes, which was found to be 78.33% and 82.52%, respectively, in the conditions of neutral pH and ambient temperature. Addition of PVP and PEG wetting agents improved the structural properties and permeability of membranes, but the dye removal was decreased as against plain ones. As the retention of PEG and PVP-based PSf and PES membrane was calculated at an average of 50%, they could be used for dye retention separately or could be a candidate as a pretreatment membrane prior to nanofiltration or reverse osmosis to make their lifetime longer.

Long-term MBR performance of polymeric membrane modified with Bismuth-BAL chelate (BisBAL).

An ultrafiltration membrane prepared by polyethersulfone (PES) was modified with Bismuth-BAL chelate (BisBAL) and was used in submerged membrane bioreactor system. Moreover, a control membrane reactor was also tasked to evaluate the effect of BisBAL on the membrane performance. The flux profile, transmembrane pressure, the effect of chemical treatment, cake layer formation, anti-fouling properties against extracellular polymeric substances (EPS) and soluble microbial products (SMP) were studied. The UF modified membrane demonstrated a sustained permeability, low cleaning frequency, and longer filtration time. In terms of anti-EPS and SMP accumulation, the modified membrane showed a lower membrane resistance. It can be illustrated from scanning electron microscopy and confocal laser scanning microscope images that the modified membrane had presented better properties than bare PES membrane, as it was looser and thinner. Thus, the UF membrane proved to be more efficient in terms of permeability and lifetime.

An Autopsy of Nanofiltration Membrane Used for Landfill Leachate Treatment.

Komurcuoda leachate treatment plant, Istanbul, which consists of membrane bioreactor (MBR) and nanofiltration (NF) system, faced rapid flux decline in membranes after 3-year successful operation. To compensate rapid flux decline in membranes, the fouled membranes were renewed but replacement of the membranes did not solve the problem. To find the reasons and make a comprehensive analysis, membrane autopsy was performed. Visual and physical inspection of the modules and some instrumental analysis were conducted for membrane autopsy. Membranes were found severely fouled with organic and inorganic foulants. Main foulant was iron which was deposited on surface. The main reason was found to be the changing of aerator type of MBR. When surface aerators were exchanged with bottom diffusers which led to increasing of dissolved oxygen (DO) level of the basin, iron particles were oxidized and they converted into particulate insoluble form. It was thought that probably this insoluble form of the iron particles was the main cause of decreased membrane performance. After the diagnosis, a new pretreatment alternative including a new iron antiscalant was suggested and system performance has been recovered.