Study on the fouling behavior of silica nanocomposite modified polypropylene membrane in purification of collagen protein

Surface modification of quartz sand: A review of its progress and its effect on heavy metal adsorption

Quartz sand (SiO₂) is a prevalent filtration medium, boasting wide accessibility, superior stability, and cost-effectiveness. However, its utility is often curtailed by its sleek surface, limited active sites, and swift saturation of adsorption sites. This review outlines the prevalent strategies and agents for quartz sand surface modification and provides a comprehensive analysis of the various modification reagents and their operative mechanisms. It delves into the mechanism and utility of surface-modified quartz sand for adsorbing heavy metal ions (HMIs). It is found that the reported modifiers usually form connections with the surface of quartz sand through electrostatic forces, van der Waals forces, pore filling, chemical bonding, and/or molecular entanglement. The literature suggests that these modifications effectively address issues inherent to natural quartz sand, such as its low superficial coarseness, rapid adsorption site saturation, and limited adsorption capacity. Regrettably, comprehensive investigations into the particle size, regenerative capabilities, and application costs of surface-modified quartz sand and the critical factors for its wider adoption are lacking in most reports. The adsorption mechanisms indicate that surface-modified quartz sand primarily removes HMIs from aqueous solutions through surface complexation, ion exchange, and electrostatic and gravitational forces. However, these findings were derived under controlled laboratory conditions, and practical applications for treating real wastewater necessitate overcoming further laboratory-scale obstacles. Finally, this review outlines the limitations of partially surface modified quartz sand and suggests potential venues for future developments, providing a valuable reference for the advancement of cost-effective, HMI-absorbing, surface-modified quartz sand filter media.

Development of a Disposable Polyacrylamide Hydrogel-Based Semipermeable Membrane for Micro Ag/AgCl Reference Electrode

Currently, Ag/AgCl-based reference electrodes are used in most electrochemical biosensors and other bioelectrochemical devices. However, standard reference electrodes are rather large and do not always fit within electrochemical cells designed for the determination of analytes in low-volume aliquots. Therefore, various designs and improvements in reference electrodes are critical for the future development of electrochemical biosensors and other bioelectrochemical devices. In this study, we explain a procedure to apply common laboratory polyacrylamide hydrogel in a semipermeable junction membrane between the Ag/AgCl reference electrode and the electrochemical cell. During this research, we have created disposable, easily scalable, and reproducible membranes suitable for the design of reference electrodes. Thus, we came up with castable semipermeable membranes for reference electrodes. Performed experiments highlighted the most suitable gel formation conditions to achieve optimal porosity. Here, Cl^- ion diffusion through the designed polymeric junctions was evaluated. The designed reference electrode was also tested in a three-electrode flow system. The results show that home-built electrodes can compete with commercial products due to low reference electrode potential deviation (~3 mV), long shelf-life (up to six months), good stability, low cost, and disposability. The results show a high response rate, which makes in-house formed polyacrylamide gel junctions good membrane alternatives in the design of reference electrodes, especially for these applications where high-intensity dyes or toxic compounds are used and therefore disposable electrodes are required.

Fouling mechanisms in anoxic-aerobic sequencing batch membrane bioreactor based on adapted Hermia models and main foulant characteristics

Various derivatives of Hermia models (complete pore blocking, intermediate pore blocking, cake layer formation, and standard pore blocking) and different assessments of foulant characteristics have long been used to determine the membrane fouling mechanisms. Accordingly, this study aims to adapt Hermia models and their combination according to the operating conditions of an anoxic-aerobic sequencing batch membrane bioreactor (A/O-SBMBR). In addition, fouling mechanisms of the A/O-SBMBR were assessed using these models along with the main foulant characteristics. Models fitting with the transmembrane pressure (TMP) data indicated that the intermediate-standard model was accounting for the increased fouling during the whole regular operating period, with the residual sum of squares (RSS) of 58.3. A more detailed study on the distinct stages of TMP curve showed that the intermediate-standard model had the best fit in stages of 2 and 3, with the RSS equal to 2.6 and 2.8, respectively. Also, the complete-standard model provided the best description of the fouling mechanism in stage 4, with the RSS of 12.5. Different analyzes revealed how the main foulant characteristics affect the occurrence of intermediate, complete and standard fouling mechanisms in the A/O-SBMBR, which is consistent with the fitting results of the adapted Hermia models. The modeling and experimental methods used in the presented study provided a valuable basis to prevent and control membrane fouling in membrane bioreactors.

Comparative Study of The Yield and Physicochemical Properties of Collagen from Sea Cucumber (Holothuria scabra), Obtained through Dialysis and the Ultrafiltration Membrane

Collagen was extracted from the body wall of sea cucumber (Holothuria scabra) using the pepsin-solubilized collagen method followed by isolation using dialysis and the ultrafiltration membrane. The yield and physicochemical properties of the collagen obtained from both isolation methods, denoted as D-PSC and UF-PSC, were compared. The ultrafiltration method affords a higher yield of collagen (11.39%) than that of the dialysis (5.15%). The isolated collagens have almost the same amino acid composition, while their functional groups, referred to as amide A, B, I, II, and III bands, were in accordance with commercial collagen, as verified by Fourier Transform Infrared (FT-IR) spectroscopy. The UV-Vis absorption peaks at 240 nm and 220 nm, respectively, indicated that the collagens produced are type-I collagen. The D-PSC showed interconnecting sheet-like fibrils, while the UF-PSC exhibited a flaky structure with flat-sheets arranged very close to each other. The higher yield and comparable physicochemical properties of the collagen obtained by ultrafiltration as compared with dialysis indicate that the membrane process has high potential to be used in large-scale collagen production for food and pharmaceutical applications.

Mechanical Performance of Fiber Reinforced Cement Composites Including Fully-Recycled Plastic Fibers

The use of virgin and recycled plastic macro fibers as reinforcing elements in construction materials has recently gained increasing attention from researchers. Specifically, recycled fibers have become more attractive owing to their large-scale availability, negligible cost, and low environmental footprint. In this work, we investigate the benefits related to the use of fully-recycled synthetic fibers as dispersed reinforcement in Fiber Reinforced Cement Composites (FRCCs). In light of the reference performance of FRCCs including virgin polypropylene (PP) fibers only, the mechanical response of composites reinforced with polyolefin filaments treated with a sol-gel silica coating and polyethylene terephthalate (PET)/polyethylene (PE) cylindrical draw-wire fibers is here assessed through three-point bending tests. Remarkably, recycled polyolefins lead to a notable enhancement in terms of peak strength and post-crack energy dissipation capability. This improvement is ascribed to both the flattened shape of fibers and the surface coating, which turns out to be very effective at strengthening the fiber-to-matrix bond. On the other hand, PET/PE fibrous reinforcement generally leads to a lower toughness, if compared to the virgin fibers. However, no reduction in terms of peak stress is evidenced. Balancing the significance of mechanical performance and environmental sustainability in the framework of a circular economy approach, both fully-recycled fibers at hand can be regarded as promising candidates for innovative structural applications.

Investigation of antifouling properties of polypropylene/TiO2 nanocomposite membrane under different aeration rate in membrane bioreactor system

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PP/TiO₂ membrane was fabricated via thermally induced phase separation (TIPS) method.

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Effect of aeration rate was investigated on antifouling properties of both membranes in MBR system.

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Fouling properties of membranes under different aeration rates were analyzed using Hermia’s models.

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Nanocomposite membrane showed high antifouling compared to neat membrane.

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Increasing in high aeration rate resulted in sludge floc breakage as well as pore blockage.

This paper presents the results of aeration rate effect on antifouling properties of polypropylene (PP)/TiO₂ nanocomposite membrane in membrane bioreactor (MBR) system in order to oil refinery wastewater treatment. For this purpose, three levels of aeration rate with specific aeration demand per membrane area (SADm) of 0.5, 1, and 1.5 m³/m²h was used. According to the obtained results, PP nanocomposite membrane showed high hydrophilicity, porosity, and high flux compared to neat PP membrane. Also, either low or high aeration rate had a negative influence on permeability and antifouling properties of neat PP and nanocomposite membranes. The analysis of fouling mechanism for both membranes based on Hermia’s model revealed that the cake formation is dominant mechanism for lower aeration rate while by increasing aeration rate, all models couldn’t predict experimental data. Meanwhile, by increasing aeration rate, chemical oxygen demand (COD) removal for activated sludge and both membranes decreased and increased, respectively.

Preparation and Anti-Fouling Property of Acryloylmorpholine-Grafted PVDF Membrane: The Effect of Cross-Linking Agent

Inspired by the hydration capability of hydrogel materials, cross-linked poly(N-acryloylmorpholine) (PACMO) chains were designed into poly(vinylidene fluoride) (PVDF) backbones to synthesize the copolymers (PVDF-g-PACMO) using the radical polymerization method. These copolymers were then cast into the porous membranes via immersion phase inversion. The effects of N,N′-methylenebisacrylamide (MBAA) in the reaction solution on the structure and performance of as-prepared copolymer membranes were evaluated by elemental analysis, X-ray photoelectronic spectroscopy, field emission scanning electron microscopy, water contact angle measurement, protein adsorption and filtration experiment. The grafting degree of PACMO increases with the increase of MBAA amount in the reaction solution, which endows the copolymer membrane with a good hydrophilicity. The protein adsorption and irreversible membrane fouling decrease and then further increase with the elevated grafting degree of PACMO. This result indicates that the anti-fouling property of membrane not only depends on the surface hydrophilicity and but also associates with the grafting structures of PACMO. This work provides a fundamental understanding of various grafting structures governing the performance of anti-fouling properties.