Surface Fouling Research Articles

Orthogonal Agent Comprising a Nitrile N-Oxide and a Phenylcarbamate for Facile Molecular Integration on Styrne-Butadiene Resin.

The covalent attachment of poly(ethylene glycol) (PEGylation) to materials minimizes non-specific fouling of the material surface with biocomponents. While the PEGylation reaction on polar surfaces is widely used and regarded as a common technique, the PEGylation on less polar polymers and elastomers is extremely difficult due to the absence of reactive points with PEG terminus. Herein, the design and synthesis of an orthogonal agent with a nitrile N-oxide and a phenyl carbamate that can mediate between an alkene and an amine are reported. The ligation capacity of the orthogonal agent is demonstrated through the model reaction to connect between 1-hexene and 4-methoxybenzylamine and the grafting reaction of PEG onto poly(styrene-co-butadiene) (SB) resin. The surface characteristics of PEGylated SB film are evaluated by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Because SB resin is frequently used as a 3D-printing polymer, the present study indicates that the orthogonal agent can be applicable to the surface modification of 3D-printed objects precisely manufactured by using a computer-aided design (CAD) file in the future.

Enhanced heavy oil fouling resistance of cobalt-based spray-deposited coatings by alloy design and heat treatment

Heavy oil hydrocracking fouls critical reactor components, causing premature turnarounds. Developing materials with superior resistance to coking, sulfidation, and wear proves crucial. High-velocity oxy-fuel (HVOF) coating improves materials' properties as an industrial-ready solution. This study explores the effect of alloying elements on the HVOF-sprayed CoCrMoSi coating model and their role in protecting against heavy oil fouling. Heat treatment reduced the coatings' inhomogeneity and microstructural defects, substantially improving their protection against fouling. A novel optical image treatment has been developed to semi-quantitatively assess the surface fouling intensity. The study provides insights into the complex interplay between alloy composition, microstructure, heat treatment, and surface energy in optimizing coating protection against heavy oil fouling.

Zwitterion Modification in Desalination Membrane for Rejecting Salt and Salt Ions in Brackish Water – A Mini Review

ABSTRACTDesalination membrane using zwitterion modification provides a significant opportunity to enhance excellent properties for rejecting salt and salt ions. The outstanding properties are designed by positive and negative charges attached to the membrane surface, including water permeability, salt permeability, fouling, and hydrophilicity of the membrane surface. The hydrophilic membrane, which is mentioned as one of the types of desalination membrane, presents the ability to repel salt and salt ions and pass the water. The modification of hydrophilic membranes is also affected by several factors, including water permeability, salt permeability, fouling of membrane surfaces, crossflow velocity, transmembrane pressure, and temperature. Regarding membrane modification, zwitterion has been applied for several ranges, such as the hemodialysis process, live cell imaging, antibacterial surfaces, and wound dressing. However, using a zwitterion modification membrane for desalinating water containing salt content, including brackish water, has yet to be developed. In addition, literature reviews related to polymer membranes for brackish water desalination have never been comprehensively documented. Thus, this review article addresses the zwitterion modification for desalination membranes, which can reject salt and salt ions in brackish water. Furthermore, the mechanism of zwitterion modification for desalination membranes has been presented. Finally, the challenge of zwitterion modification for desalination membranes has been evaluated to inspire insight for future studies.

Copper-Based Electrochemical Sensor Derived from Thiosemicarbazide for Selective Detection of Neurotransmitter Dopamine.

This paper presents the synthesis of the ligand 1-picolinoyl-4-cyclohexyl-3-thiosemicarbazide (H2pctc) and new metal complexes [Ni(Hpctc)2] (1), [Cu(Hpctc)Cl] (2), and [Cd(Hpctc)2] (3). The synthesized metal complexes were precisely characterized using single crystal X-ray diffraction (SC-XRD). In addition, complexes 1-3 were also characterized by UV-vis, fluorescence, and infrared spectroscopy. SC-XRD data confirmed the distorted octahedral geometry around the Ni(II) and Cd(II) centers and the distorted square planar geometry around the Cu(II) center. Data derived from the emission spectra depict that higher fluorescence intensity was exhibited by complexes 1, 2, and 3 in comparison to that of the free ligand H2pctc, and complex 3 showed the maximum intensity. Further, these metal complex-modified GCEs (glassy carbon electrodes) were utilized for electrochemical sensing of dopamine (DPM). The electrochemical studies of these complexes were performed using modified glassy carbon electrodes supported by electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. In contrast to complexes 1 and 3, complex 2 is a superior electrode material with a high effective surface area for the electrochemical oxidation of DPM, according to the electrochemical response results. The derived sensor had a wide linear detection range of 1 to 1400 μM, an acceptable sensitivity of 0.01531 μA cm-2 μM-1, and a low LOD of 0.38 μM. The proposed approach was free of the interfering effects of ascorbic acid, uric acid, aminophenol, and other substances. During the successive scans, no fouling of the electrode surface was observed. The proposed electrochemical sensor had excellent stability, sensitivity, and a low detection limit making it suitable for the analysis of a variety of real samples. Additionally, it was proven to be useful for analyzing biological fluids.

Fouling of Reverse Osmosis (RO) and Nanofiltration (NF) Membranes by Low Molecular Weight Organic Compounds (LMWOCs), Part 1: Fundamentals and Mechanism.

Reverse osmosis (RO) and nanofiltration (NF) are ubiquitous technologies in modern water treatment, finding applications across various sectors. However, the availability of high-quality water suitable for RO/NF feed is diminishing due to droughts caused by global warming, increasing demand, and water pollution. As concerns grow over the depletion of precious freshwater resources, a global movement is gaining momentum to utilize previously overlooked or challenging water sources, collectively known as "marginal water". Fouling is a serious concern when treating marginal water. In RO/NF, biofouling, organic and colloidal fouling, and scaling are particularly problematic. Of these, organic fouling, along with biofouling, has been considered difficult to manage. The major organic foulants studied are natural organic matter (NOM) for surface water and groundwater and effluent organic matter (EfOM) for municipal wastewater reuse. Polymeric substances such as sodium alginate, humic acid, and proteins have been used as model substances of EfOM. Fouling by low molecular weight organic compounds (LMWOCs) such as surfactants, phenolics, and plasticizers is known, but there have been few comprehensive reports. This review aims to shed light on fouling behavior by LMWOCs and its mechanism. LMWOC foulants reported so far are summarized, and the role of LMWOCs is also outlined for other polymeric membranes, e.g., UF, gas separation membranes, etc. Regarding the mechanism of fouling, it is explained that the fouling is caused by the strong interaction between LMWOC and the membrane, which causes the water permeation to be hindered by LMWOCs adsorbed on the membrane surface (surface fouling) and sorbed inside the membrane pores (internal fouling). Adsorption amounts and flow loss caused by the LMWOC fouling were well correlated with the octanol-water partition coefficient (log P). In part 2, countermeasures to solve this problem and applications using the LMWOCs will be outlined.

Biomass as a Renewable Energy Source for Power Boilers

The development of photovoltaic systems and wind turbines reduces the carbon footprint (CFP) of energy generation. However, these systems deteriorate the stability of the national power system (NPS). The important stabilizing element of the Polish NPS are coal-fired power plants. Since the cold startup of these units takes several hours, the stability of the NPS forces the boilers to operate so that the power can be increased quickly. Therefore, it will be impossible to abandon coal-fired units in the next years, and the boilers will be modernized to reduce their CFP. An important option is to replace coal with a fuel with a lower CFP, e.g. biomass. This paper deals with the CFP for different types of biomass. It also considers methane emissions from coal mines. The CFP for coal and biomass was compared with the CFP for green ammonia. Using 0-dimensional calculations of the boiler, the need to modernize the heating surfaces was assessed when replacing 50% and more of coal with biomass. The changed fouling of heating surfaces was taken into account. The problem of reducing harmful phenomena such as corrosion, erosion and slagging associated with such a change of fuel is also discussed.

Inhibition of bacteria adhesion and biofilm formation using a precisely structured nitric oxide-releasing coating with repeatedly renewing antimicrobial and antifouling ability

Bacterial adhesion and colonization usually causes the formation of biofilm that cannot be easily eradicated by common antibiotics and disinfectants. Surface covalent immobilization of nitric oxide (NO)-releasing polymer is an effective surface modification strategy to combat the threat from bacteria. Although surface covalent strategy avoided the leaching of toxic NO donors, the existence of hydrophobic NO donors on topsurface could inevitably accelerate the microorganism adhesion and accumulation, and the NO-releasing period of time was still very limited. In this work, we prepared an antimicrobial and antibiofilm surface via tethering a precision-structured NO-releasing copolymer brush to an organic-inorganic hybrid hard coating (> 5H pencil hardness) on one end. The precision-structured diblock copolymer brush was composed of a surface antifouling block and a subsurface antimicrobial block of NO-releasing units. A typical effect of “kill two birds with one stone” was observed, the NO releasing subsurface segment within a polymeric matrix prolongs NO release while also preventing surface fouling caused by hydrophobic NO donors on top surface. The impacts of polymer architecture on bioactivity was detailed investigated, and the block copolymer brush exhibited the optimal inhibitory effects against bacteria colonization and biofilm formation. The developed bioactive diblock copolymer brush was grafted from a hard hybrid persistent coating that embeds considerable initiation sites for surface modification. Thanks to the presence of initiator throughout the hybrid network, the initiation layer could initiate polymerization repeatedly after the polymer brushes are worn off at high pressure. Thus, the coating exhibited repeatedly renewing antimicrobial and antifouling ability after multiple abrasion cycles. This work not only developed a novel strategy for regulating NO releasing via modulating the polymer architecture, but provided a feasible route for obtaining a robust initiator layer for synthesizing polymer brush for antimicrobial and antifouling applications.

Heavy Metal Rejection Performance and Mechanical Performance of Cellulose-Nanofibril-Reinforced Cellulose Acetate Membranes.

In this research, cellulose acetate (CA) and CA nanocomposite membranes, reinforced with mass fractions of cellulose nanofibrils (CNF), are prepared using the phase separation technique. The membranes are extensively characterized using several techniques: Fourier Transform Infrared (FTIR) spectroscopy confirms the chemical structures, while Scanning Electron Microscopy (SEM) reveals their surface morphology. Mechanical characterization is conducted to explore the mechanical behavior of the membranes under wet and dry conditions through tensile testing. The mechanical properties of CA and CA-CNF membranes are also estimated using the Mori-Tanaka mean-field homogenization method and compared to experimental findings. The flux performance for pure and dam water, assessed at 3 bar, demonstrates that CNF reinforcement notably enhances the CA membrane's performance, particularly in flux rate and fouling resistance. The CA membrane shows high efficiency in removing Fe2+, Ba2+, and Al3+ from dam water, while CA-CNF membranes exhibit a varied range of removal efficiencies for the same ions, with the 0.5 wt % CNF variant showing superior resistance to surface fouling. Additionally, while CNF increases tensile strength and stiffness, it leads to earlier failure under smaller deformations, especially at higher concentrations. This research provides a detailed assessment of CA and CA-CNF membranes, examining their chemical, structural, and mechanical properties alongside their effectiveness in water treatment applications.

Modified PVDF ultrafiltration membrane with host–guest supramolecular trapping for efficient separation of multiple organic contaminants

In our modern lifestyle, the cocktail of organic pollutants from everyday items, such as hair dyes, cloth dyes, food colours, hair oils, cooking oils, and agricultural proteins, enters water streams through household pipelines. This unnoticed contamination, growing alarmingly, poses a serious challenge beyond the scope of conventional separation techniques, calling for a comprehensive solution. While membrane technology offers a promising solution, it grapples with persistent surface fouling issues. This study introduces a novel approach through the development of extraordinary Polyvinylidene fluoride-Montmorillonite-Cucurbit[6]uril (PVDF-M-CB[6]) mixed matrix membranes, presenting a potential breakthrough in overcoming surface fouling challenges and offering a versatile solution for the separation of an array of organic contaminants. Powered by the synergistic host–guest supramolecular complexation of CB[6] onto montmorillonite (M) clay support, these membranes demonstrate swift and selective encapsulation, leading to superior cationic dye rejection. Adding to the allure, CB[6]’s structure encourages favorable carbonyl interactions with bovine serum albumin (BSA), effectively repelling the protein away from the membrane, while also promoting seamless oil–water emulsion separation with an underwater oil contact angle of 150 ± 3°, displaying its superoleophobic nature and enhancing remarkable antifouling properties. The PV-M-CB[6] membranes showcased 2x removal of cationic dyes, 1.3x removal of anionic dyes, 1.4x oil–water emulsion separation, and 2x BSA separation compared to the pristine polyvinylidene fluoride (PVDF) membrane. These membranes displayed 98.3 % efficiency in oil–water emulsion separation and sustained a flux recovery ratio of over >75% after seven cycles. Overall, PV-M-CB[6] membranes represent an innovative solution with heightened hydrophilicity, remarkable antifouling performance, and exceptional proficiency in delivering one-stop organic foulant separation.

Patterns of dermal denticle loss in sharks.

As they grow, sharks both replace lost denticles and proliferate the number of denticles by developing new (de novo) denticles without prior denticle shedding. The loss and replacement of denticles has potential impacts on the energetic cost of maintaining the skin surface, the biomechanical functions of shark skin, as well as our ability to predict shark abundance from fossil denticle occurrence in sediment cores. Here, we seek to better understand patterns of denticle loss and to show how denticles are being replaced in mature sharks. We illustrate shark skin surfaces with missing denticles and quantify both within-species and between-species patterns of missing denticles using images from across regions of the body for two species and images at similar body regions for 16 species of sharks. Generally, sharks are missing similar numbers of denticles (0%-6%) between species and regions. However, there are exceptions: in the smooth dogfish, the nose region is missing significantly more denticles than most posterior-body and fin regions, and the common thresher shark is missing significantly more denticles than the smooth dogfish, leopard shark, angel shark, bonnethead, and gulper shark. Denticle regrowth starts with crown development and mineralization beneath the epidermis, followed by eruption of the crown, and finally the mineralization of the root. The pulp cavity of replacement denticles is initially large and surrounded by a thin shell of enameloid upon eruption of the denticle. After eruption of the denticle, the deposition of dentine continues internally after the denticle reaches its final position. Replacement of missing denticles, representing less than 6% of the skin surface at any one time, may not compromise hydrodynamic function, but by constantly updating the skin surface throughout life, sharks may reduce surface fouling and maintain a functional complex skin surface by repairing local damage to individual denticles.

Electrocatalytic Anaerobic Oxidation of Benzylic Amines Enabled by Ferrocene-Based Redox Mediators.

The generation and functionalization of carbon- or nitrogen-centered radicals are of great interest for their potential synthetic utility. Here, we report the anaerobic electrocatalytic oxidation of two primary benzylic amines, benzylamine and 2-picolylamine, in the presence of a catalytic quantity of an electron deficient ferrocene derivative as a single-electron redox mediator. The use of the appropriate redox mediator prevented fouling of the electrode surface and significantly decreased the potential at which the catalytic oxidation reaction occurred. Simulation of the electrochemical results revealed an ErCi' catalytic process between the redox mediator and both substrates and significant difference in the electron transfer rate between the two substrates and electrochemically oxidized mediator. Through anaerobic controlled-potential electrolysis, we demonstrated a method with a Faradaic efficiency of 90% forming the desired coupled imine product of benzylamine oxidation while avoiding an excess of problematic overoxidation, hydrolysis, and other side reactions. Based on the electrochemical data along with the product analyses using IR and 1H and 13C NMR spectroscopies, the proposed mechanistic steps for the redox mediated electrocatalytic process were laid out.

The Differential Impact of Resorcinarenes on Ferrocene Redox Couple: Towards Electroactive Host-Guest Systems

Alternative to complex labelling of resorcinarene hosts with redox-active probes, non-covalent complex formation offers a unique avenue towards the design of dynamic electro-active host-guest systems towards application in sensors and functional materials. Here, resorcinarene hosts were evaluated with a well-known redox probe, ferrocene (Fc). Specifically, hosts were designed based on tuning the resorcinarene rim with functional groups to allow for hydrogen bonding, pi-pi stacking, hydrophobic and electrostatic interactions. Cyclic voltammetry was used with glassy carbon electrode as a working electrode in organic solvent to evaluate interactions between hosts and Fc. Specifically, the electrochemical properties of Fc, hosts, and host-Fc mixtures were evaluated with respect to the ferrocene/ferrocenium redox couple (reversibility, current and potential). Depending on the host structure, all hosts induced a potential shift of ferrocene/ferrocenium redox couple. The reversibility of the redox couple was maintained with certain hosts, while others resulted in surface fouling. The electrochemical studies were further supplemented by non-electrochemical methods, such as nuclear magnetic resonance, spectroscopy, mass spectrometry as well as theoretical calculations using density functional theory. Data show that controlled and tunable redox host-guest systems with well-defined redox properties may be achieved through chemical modifications of hosts, which may be used to inform functional sensors and devices with a wide range of applications such as phosphate analogue detection.

Measurement of Neuropeptides and Amino Acids with Carbon-Fiber Multielectrode Array Enzyme-Modified Biosensors

Carbon fiber microelectrodes (CFMEs) have been used to detect neurotransmitters and other biomolecules using fast-scan cyclic voltammetry (FSCV) for the past few decades. These assays typically measure small molecule neurotransmitters such as dopamine and serotonin. The carbon fiber is relatively small, biocompatible, and makes minimally invasive measurements at high spatial and temporal resolution. Carbon Fiber Multielectrode arrays have been utilized to measure multiple neurotransmitters in several brain regions simultaneously with multi-waveform application on each electrode. We have extended this work to measure larger molecule neuropeptides such as Neuropeptide Y and Oxytocin, a pleiotropic peptide hormone, is physiologically important for adaptation, development, reproduction, and social behavior. This neuropeptide functions as a stress-coping molecule, an anti-inflammatory agent, and serves as an antioxidant with protective effects especially during adversity or trauma. Here, we measure tyrosine using the Modified Sawhorse Waveform (MSW), enabling enhanced electrode sensitivity for the amino acid and peptide, decreased surface fouling, and codetection with other catecholamines. As both oxytocin and Neuropeptide Y contain tyrosine, the MSW was also used to detect these neuropeptides. Additionally, we demonstrate that applying the MSW on CFMEs allows for real time measurements of exogenously applied neuropeptides on rat brain slices. These results may serve as novel assays for neuropeptide detection in a fast, sub-second timescale with possible implications for in vivo measurements and further understanding of the physiological role of neuropeptides such as Neuropeptide Y and oxytocin.Moreover, we have also developed enzyme modified microelectrodes for the measurement of glutamate (L-glutamic acid), which is an important excitatory amino acid and biomarker for epilepsy along with the inhibitory GABA. Since glutamate is not redox active at carbon electrodes, we modified CFMEs with glutamate oxidase enzyme to metabolize glutamate to hydrogen peroxide, which was then oxidized at carbon electrodes to produce readout cyclic voltammograms (CVs). The enzyme coating was optimized by varying the concentration of enzyme, chitosan binder, solvent, and deposition time. The coating was further analyzed electrochemically and imaged with scanning electron microscopy (SEM) for thickness and uniformity of surface coverages. Energy-Dispersive Spectroscopy (EDS/EDX) was utilized for chemical surface functionalization analysis. Glutamate oxidation was found to be adsorption controlled to CFMEs and characterized at various scan rates, concentrations, and stability times as well with an approximate 100 nM limit of detection. Glutamate was co-detected in complex mixtures with several monoamines such as dopamine, serotonin, norepinephrine, and others. Glutamate will furthermore be measured in several food samples and ex vivo in rat coronal brain slices and in vivo in anesthetized and freely behaving animals.

Antimicrobial Peptide-Based Sensor for the Electrochemical Detection of Methicillin-Resistant Staphylococcus Aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a gram-positive bacterium that colonizes on the skin and nasal track of humans, which can lead to serious illnesses such as skin and soft tissue infections, pneumonia, and septicemia.MRSA is resistant to an entire class of antibiotics called beta-lactams, including penicillin, amoxicillin, and oxacillin, making it more difficult to treat. Culture based methods and molecular based methods like PCR are currently being used for the detection of MRSA, but these methods possess the drawbacks of being slow and expensive, respectively. Thus, we focused on developing a reagentless, cost-effective, near real-time detection method for intact MRSA cells.Antimicrobial peptides (AMPs) possess the ability to interact with bacterial cells by inhibiting their growth or by lysing them.However, this initial interaction between the cationic AMPs and the negatively charged bacterial cells can be used for the detection of pathogens like MRSA. Here, we used a MRSA-specific antimicrobial peptide, DP7, to fabricate an electrochemical peptide-based (E-PB) sensor. The DP7 probe was further modified with a methylene blue redox label and an alkanethiol chain which allows for the formation of a thiol-gold self-assembled monolayer. The sensor surface was passivated with both 6-mercapto-1-hexanol and a thiolated tetra-thymine sequence to prevent surface fouling. Electrochemical detection of MRSA was accomplished using alternating current voltammetry. Control experiments were performed using two gram-positive bacteria, Bacillus subtilis and Staphylococcus epidermidis, and two gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa. The DP7 sensor responded to MRSA in a concentration-dependent manner and was proven to be selective for MRSA over the other four microbes. Specifically, the % signal suppression obtained for MRSA was much larger when compared to those obtained for the other microbes. The same behavior was observed in pure buffer and 5% synthetic wound fluid. In addition, the detection time was relatively short, with signal saturation in less than 60 min. Overall, the DP7 sensor has demonstrated to possess attributes similar to other E-PB sensors. It has the potential to be developed as a rapid, reliable, and cost-effective diagnostic tool for MRSA, which will be useful in preventing the spread of the pathogen in the community. Furthermore, this sensing platform is versatile and can be redesigned for detection of other pathogenic bacteria.

Analysis of carbon and nitrogen from atmospheric sources by bulk deposition sampling at various locations in Germany

Atmospheric deposition of particulate matter is an important indicator of air pollution and a significant factor in material surface fouling. The elemental composition of this nutrient-containing dust depends largely on the exposure region and time as well as on climate. Therefore, in this paper we report an analysis of atmospheric pollutions with a self-made low-cost bulk deposition sampler directed at sampling deposition via air transport and rainfall. We used the device in diverse environments - thus comparing an urban region, an area surrounded by forest and an area mainly dominated by agriculture. The total organic carbon (TOC) and total nitrogen (TN) amounts were selected as indicator parameters and analyzed in a biweekly rhythm for three and a half and two years, respectively. The TOC value responded to particulate matter in the urban area, especially significant were the influences of the New Year's firework in urban and pollen in the rural forest area. In contrast, the TN value was more under the influence of the nitrogen emissions in the agriculture-dominated area. However, the TN value did not correlate with the NOx values in the urban area because the atmospheric nitrogen emissions in the city might originate from various emission sources. Summarizing, the TOC and TN values of the self-made low-cost bulk deposition sampler were in good agreement with environmental events of their immediate surrounding. Moreover, the selected containers and sampling procedures are universally applicable to monitor and analyze organic as well as inorganic parameters (e.g. metal ions) of atmospheric deposition.

Surface Fouling Characterization Methods for Polymeric Membranes Using a Short Experimental Study.

Membrane surface fouling has always been a critical issue for the long-term operation of polymeric membranes. Therefore, it is crucial to develop new approaches to prevent fouling. While developing new approaches, characterization methods are greatly important for understanding the distribution of fouling on the membrane surface. In this work, a cellulose acetate membrane was fouled by the filtration of artificial wastewater based on alginate. The surfaces of fouled membranes were characterized through scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), atomic force microscopy (AFM), and white light interferometry (WLI). The results were then compared in terms of the resolution, accuracy, feasibility, and cost-efficiency.

AFM Analysis of Polymeric Membranes Fouling

This work represents a part of a larger work, aimed at evaluating the fouling behavior of different flat polymeric membranes for low-pressure applications when placed in contact with industrial wastewater (IWW). To design and understand the operation of a membrane process it is essential to know the fouling mechanisms. Commercial PVDF and PS membranes were tested under static conditions. The reduction in membrane flux was calculated, before and after the fouling tests. Parameters such as membrane material, pore size, solids concentration, particle size, pH, temperature, flow rate, and pressure were studied to identify the fouling behavior of the membrane. The strong adhesion of organic molecules on the membrane surface develops a resistance to pore blockage which allows a significant decrease in the flow of clean water. It is important to note that membranes of the same material, PVDF, but with different pore size (0.2 and 0.5 mm), and membranes of different materials, PVDF and PS, but with the same pore size (0.2 mm) were tested to study the trend of surface fouling to predict it and/or design surface modifications of the membranes employed. A morphological analysis of the membranes was carried out to understand the fouling mechanism, the fouling times, and the nature of the block that determines the reduction of flow through the membrane itself. Roughness measurements reveal that roughness goes up to 120 minutes of immersing time in wastewater, but after 4 hours it returns to initial value but with a significant decrease of flux to water. Understanding the relationship between flux decline, morphology, and roughness role is key to preventing fouling and studying a valid method to clean the membrane.

Application of hollow fiber membranes for producing an ultrafiltration permeate from colostrum whey enriched in bioactive compounds

Bovine colostrum whey, despite being a source of bioactive peptides and prebiotic oligosaccharides with dietary and nutraceutical applications, presents significant processing challenges due to its high viscosity, making hollow fiber membranes, with their superior ability to control membrane fouling, well-suited for handling such fluids. The objective of this work was to determine optimal ultrafiltration conditions of a 10 kDa hollow fiber membrane to increase efficiency (i.e., permeate flux), selectively retain whey proteins, and facilitate the permeation of peptides (< 10,000 Da) and oligosaccharides (∼600 Da) from bovine colostrum whey. The impact of feed flow rate (3, 6, 9 L min-1) and transmembrane pressure (1, 2, 3 bar) were evaluated on permeate flux, protein retention, and non-protein nitrogen permeation. Higher permeate fluxes were observed at higher feed flows and moderate transmembrane pressure, demonstrating the ability of turbulence to disrupt the concentration polarization layer at the membrane surface and decrease fouling, as exhibited in the resistance analyses. Higher feed flow significantly increased the cumulative permeate flux during colostrum whey concentration (64.6 ± 0.1 L h-1m-2 at 9 L min-1 vs. 12.5 ± 5.9 L h-1m-2 at 3 L min-1, at continuous diafiltration mode and 2 bar), with continuous diafiltration experiments yielding similar permeate fluxes to the ones achieved in discontinuous mode. Processing scale at 12.7 L (2 bar, 9 L min-1, and continuous diafiltration) enabled 97% protein retention and 95% peptide and oligosaccharide permeation, producing a permeate with 1.3 g L-1 peptide and 0.42 g L-1 oligosaccharide. The results of this study highlight the impact of key ultrafiltration conditions of bovine colostrum whey using a hollow fiber membrane for the effective recovery of peptides and oligosaccharides for subsequent evaluation of their biological properties and commercial applications.

Performance Restoration of Iron Electrodes by Polarity Reversal after Long-Term Surface Fouling in Wastewater Electrocoagulation

Performance Restoration of Iron Electrodes by Polarity Reversal after Long-Term Surface Fouling in Wastewater Electrocoagulation

THE IMPACT OF HEAT-EXCHANGERS SURFACE FOULING AND THE POSSIBILITIES OF THEIR CLEANING

Introduction: This study investigates the real-world effects of pollutants on ship heat exchangers in the marine sector, focusing on the complex issues influencing maintenance expenses, environmental sustainability, and operational effectiveness. The core of the issue is figuring out a long-term, practical way to lessen the damage that heat-exchangers surface heat-exchangers surface fouling causes to ship heat exchangers. Purpose. The article aims to investigate and evaluate how pollutants affect ship heat exchangers in the marine sector from a practical standpoint. It seeks to shed light on how pollutants, such as chemicals, debris, and oil residues, impact a vessel’s environmental sustainability, maintenance costs, and operational effectiveness. The essay analyzes the complex issues caused by surface fouling-induced damage, highlighting the dangers of decreased thermal conductivity, greater overheating, higher maintenance costs, longer downtime, and possible environmental effects. Result. One practical consequence of pollutant-induced damage is that it calls for substantial and frequent cleaning, repairs, and maybe replacements of the heat exchanger components, which raises maintenance costs. Traditional cleaning procedures involve prolonged downtime for manual intervention, which worsens the economic effects on shipping businesses and trade routes. Furthermore, the study highlights the negative effects uncontrolled pollutants have on the environment, highlighting how crucial regulatory compliance is to avoiding legal ramifications and preserving the good name of the sector. Conclusion. In conclusion, preserving marine operational effectiveness and environmental sustainability requires reducing the impact of pollutants on ship heat exchangers. The selection of particular heat exchanger types requires customized cleaning techniques. Advanced solutions are provided by ecologically safe chemical agents, high-pressure water jets, and automated robotic systems. To avoid losing efficiency, regular cleaning must be done under the direction of real-time monitoring. Maintaining heat exchanger performance and guaranteeing the lifespan of ship power plants in the face of changing surface fouling concerns requires striking a compromise between operational needs, environmental responsibility, and proactive maintenance.