Fouling Film Research Articles

Inhibition characteristics of pollution accumulation in high-voltage direct current conductors with XLPE and PVC film

Abstract The inhibition of pollution accumulation on the ground equipment by cross-linked polyethylene (XLPE) and polyvinyl chloride (PVC) as coating materials was investigated, and the effects of discharge voltage, power supply polarity, and the material properties of ground equipment on the characteristics of dirt accumulation were discussed. When the voltage was greater than 40 kV, the pollution accumulation of the sampling plate of the PVC-coated conductor was higher than that of the XLPE-coated conductor. Whether it was PVC or XLPE coated wire, the amount of pollution accumulation under negative polarity power was greater than that under positive polarity power. When the ground equipment was made of aluminum sheets, the amount of pollution accumulated was greater than that of the PTFE. As the film thickness increased, the amount of pollution on the aluminum fouling film decreased continuously.

Characterization of organic fouling on thermal bubble-driven micro-pumps

Thermal bubble-driven micro-pumps are an upcoming micro-actuator technology that can be directly integrated into micro/mesofluidic channels, have no moving parts, and leverage existing mass production fabrication approaches. These micro-pumps consist of a high-power micro-resistor that boils fluid in microseconds to create a high-pressure vapor bubble which performs mechanical work. As such, these micro-pumps hold great promise for micro/mesofluidic systems such as lab-on-a-chip technologies. However, to date, no current work has studied the interaction of these micro-pumps with biofluids such as blood and protein-rich fluids. In this study, the effects of organic fouling due to egg albumin and bovine whole blood are characterized using stroboscopic high-speed imaging and a custom deep learning neural network based on transfer learning of RESNET-18. It was found that the growth of a fouling film inhibited vapor bubble formation. A new metric to quantify the extent of fouling was proposed using the decrease in vapor bubble area as a function of the number of micro-pump firing events. Fouling due to egg albumin and bovine whole blood was found to significantly degrade pump performance as well as the lifetime of thermal bubble-driven micro-pumps to less than 104 firings, which may necessitate the use of protective thin film coatings to prevent the buildup of a fouling layer.

Numerical Investigation of the Effect of the Wall Properties on Downward Mercury Flow and Temperature Fluctuations in a Vertical Heated Pipe under a Transverse Magnetic Field

The work is motivated by the need to study the effect of abnormal quasi-periodic high-amplitude temperature fluctuations in a liquid metal flow in pipes and channels, which arise under conditions close to those specific for liquid metal (PbLi alloy, etc.) hydrodynamics and heat transfer in blankets of tokamak fusion reactors. Such temperature fluctuations in the cooling channels of the fusion reactor blanket pose a threat to the strength of the channel walls. The influence of the physical properties of the channel walls and potential fouling of their inner surface on the generation of these fluctuations has not been studied as yet. Therefore, this problem has been numerically investigated for a MHD mixed convection of a liquid metal in a round tube for a downward flow of mercury with the one-side heating condition under a strong transverse magnetic field using conjugate problem statement by the LES (Large Eddy Simulation) method. Numerical simulation was performed for four cases: (i) the effect of thermophysical and electrophysical properties of the steel pipe wall is neglected, (ii) the effect of wall material properties is included, (iii) the effect of the moderate contact electrical resistance caused by a layer of fouling deposits or oxides on the inner surface of the pipe is accounted for, and (iv) the resistance of the thin fouling layer is assumed to be very high. The predictions for the cases (i) and (iv) are in good agreement with the experimental data and the results of the direct numerical simulation. They demonstrate the existence of quasi-periodic abnormal high-amplitude temperature fluctuations in the fluid with a frequency of approximately 0.14 Hz. With a relatively low electrical resistance of the fouling film (case iii), the frequency of high-amplitude temperature fluctuations was considerably lower (0.07 Hz). In the absence of electrical contact resistance on the inner surface of the steel pipe (case ii), high-amplitude velocity and temperature fluctuations were not revealed in the fluid. Thus, it was shown for the first time that the physical properties of a wall and the electrical resistance between the fluid and the electrically conducting wall were responsible for the development of abnormal temperature fluctuations in the liquid and the wall and control of their amplitude and frequency. The causes of the revealed effects are discussed.

Investigation of the Chemical Durability and Thermal Impact on Functional Coated Surfaces

Heat exchangers can be coated with functional layers to reduce the negative effects of established fouling films. In the process, long-term layer stability is a requirement for the fouling-inhibiting properties of the surface coatings. Various atomic layer deposition (ALD), with layer thicknesses between 10 and 50 nm, and Parylene (polymeric) coatings, with layer thicknesses < 50 µm, are applied to stainless steel (1.4571) and structural steel (1.0038) substrates. The stability against critical thermal process conditions and cleaning media (acids, alkalis, solvents) is examined. The surface free energy of the substrates is determined before and after durability tests using a contact angle measuring device. In this study the targeted water contact angle was between 80° and 110° and the related surface free energy < 45 mN/m. The change in the surface free energy is a measure of the coating durability. The tested Parylene-coated substrates show no significant changes and no layer defects. In the case of the ALD-coated substrates, only the coating with TiO2 deposition using a chlorine-free precursor shows promising results. Non-systematical layer defects and corrosion can sometimes be optically observed on the TiO2 and Al2O3 ALD-coated substrates. A strong increase in the polar part of the surface free energy is observed. This may be due to the physisorption and chemisorption of water with the coating, increasing polar interactions. In further research, fouling experiments must be performed to investigate the influence of the coatings on the induction time.

Performance Analysis of New Continue FCC Bench Scale: Modified HS-FCC Integrated with Riser in Producing Bio-Hydrocarbon

This research analyzes the performance of the High Severity Fluidized Catalytic Cracking (HS-FCC) bench-scale system which is modified by adding a riser. The riser is installed after the downer, so the cracking process occurs in the downer and riser. The purpose of the downer and riser integration is to extend the cracking time in a limited space.This system consists of a catalyst preheater, a regenerator, feedstock evaporator, a downer, a riser, 2 separators, a condenser, 1 blower, and a control system that regulates the rate of oil and air. The innovation of this FCC bench-scale system is 1) used heat from the combustion reaction in regenerator as the only heat source 2) applied fouling film principal to evaporate the feedstock by using the threaded rod. The reaction time was carried out for 45 minutes with palm oil of 1.7 l/hour and cto 0.3. The average temperature in the riser is of 400 o C. The gasoline composition in the liquid product is 7.88 % wt, lower than other research. Interestingly, the gasoline composition has lower aromatic content (32.25 % wt) and a high RON number of 174 compared to other research.Keywords: FCC, cracking, downer, bio-hydrocarbon, RONThis research analyzes the performance of the High Severity Fluidized Catalytic Cracking (HS-FCC) bench-scale system which is modified by adding a riser. The riser is installed after the downer, so the cracking process occurs in the downer and riser. The purpose of the downer and riser integration is to extend the cracking time in a limited space.This system consists of a catalyst preheater, a regenerator, feedstock evaporator, a downer, a riser, 2 separators, a condenser, 1 blower, and a control system that regulates the rate of oil and air. The innovation of this FCC bench-scale system is 1) used heat from the combustion reaction in regenerator as the only heat source 2) applied fouling film principal to evaporate the feedstock by using the threaded rod. The reaction time was carried out for 45 minutes with palm oil of 1.7 l/hour and cto 0.3. The average temperature in the riser is of 400 o C. The gasoline composition in the liquid product is 7.88 % wt, lower than other research. Interestingly, the gasoline composition has lower aromatic content (32.25 % wt) and a high RON number of 174 compared to other research.

Differential ATR FTIR spectroscopy of membrane fouling: Contributions of the substrate/fouling films and correlations with transmembrane pressure

This study examined the formation of fouling films deposited on the surface of a polyethersulfone (PES) membrane during the filtration of alginate solutions with various ionic strengths. Membrane fouling was characterized by changes of the transmembrane pressure (TMP) and ex situ measured attenuated total reflectance (ATR) Fourier-transform IR (FTIR) spectra at varying stages of filtration runs. The ATR spectra that comprise the vibration bands characteristic of the PES substrate and the deposited film were processed taking into the gradual weakening of the PES substrate-specific bands, whose intensity was shown to depend on the wavenumber of IR radiation and the thickness of the deposited layer. Strongly linear correlations between ratios of first derivatives intensity and wavenumbers of the PES reference lines were established. Calculations of the PES bands’ attenuation coefficients allowed determining the apparent thickness and ATR FTIR vibrations of the fouling films per se. Strong correlations between TMP development and ATR-determined apparent thickness of the fouling layers were observed. The intensity of ATR absorbance at 3200 cm−1 was linearly correlated with TMP development for small TMP values before the point of rapidly developing failure of the hydraulic permeability of the system was reached.

Photocatalytic nanofiber-coated alumina hollow fiber membranes for highly efficient oilfield produced water treatment

Cost-effective purification technology of oilfield produced water (OPW) is becoming a global challenge for future petroleum exploration and production industry. Energy-efficient operation of membrane separation is potentially promising. However, severe fouling problem of oil droplets demands new robust and fouling-resistant membranes with high permeability and rejection efficiency. Here, we propose a photocatalytic nanofiber-coated inorganic hollow fiber membrane suitable for OPW treatment. The membrane was fabricated by coating polyacrylonitrile (PAN) nanofiber incorporated with graphitic carbon nitride (GCN) photocatalyst on an alumina (Al2O3) hollow fiber membrane. While the highly porous coating made of smooth hydrophilic nanofibers facilitated water permeation, the coating effectively captured oil droplets in its opening, resulting in a better rejection efficiency of oil contaminants. Its sparse mesh morphology prevented oil contaminants to form dense fouling film on the membrane surface and maintained high permeate flux even after 180 min filtration. The best permeate flux of 640 L·m−2·h−1 and oil rejection percentage of 99% were recorded for 180 min crossflow filtration of OPW at 2 bar along with the highest pure water flux of 816 L·m−2·h−1. The photocatalytic activity of GCN enabled the coating to degrade the captured oil contaminants under UV irradiation, demonstrating permeate flux of 577 L·m−2·h−1 and oil rejection of 97% after three cycles of 180 min filtration. The excellent fouling resistance and cleaning performances of the membrane are considerably beneficial for a long-term repeated filtration operation. This work will motivate researchers to develop nanofiber-coated hollow fiber membranes for future membrane separation technology.

Electrochemical Behavior and Determination of Salicylic Acid at Carbon-fiber Electrodes

The loss of electrode activity (referred to as electrode fouling) caused by an electropolymerized passive film of salicylic acid (SA), a major hydrolysis product of aspirin, significantly decreases the accuracy and the precision of indirect electrochemical detection of aspirin. However, the electrode fouling problem for electrochemical determination of SA and ways to remove the fouling film have been sparsely discussed. In addition, the electrochemical behavior of SA on a carbon-fiber electrode (CFE), widely used for the study of neurochemicals in vivo and in vitro, has not yet been studied. Herein, we report the electrochemical behavior of SA at CFEs using cyclic voltammetry and differential pulse voltammetry. The irreversible and pH dependent electrochemical oxidation of SA produced dihydroxybenzoic acids, SA dimeric products and poly-SA films that strongly adhered to the electrode surface and passivated further reactions. The electrode fouling caused by the SA films on a CFE decreased electrode sensitivity and reproducibility for the indirect determination of aspirin. In this study, the fouling effects were characterized with Fe(CN)64−/3−. Interestingly, we found that the poly-SA films on CFE can be removed by a strong base, undergoing the intramolecular base catalyzed hydrolysis of salicylate esters. This non-destructive cleaning method of poly-SA films on the electrode improved the linear dynamic range of SA as well as the accuracy and precision of SA measurements. This new cleaning method of CFEs was further applied to the indirect determination of aspirin in commercially available pharmaceutical tablets.

Cross-linked polystyrene sulfonic acid and polyethylene glycol as a low-fouling material

A negatively charged hydrophilic low fouling film was prepared by thermally cross-linking a blend consisting of polystyrene sulfonic acid (PSS) and polyethylene glycol (PEG). The film was found to be stable by dip-washing. The fouling resistance of this material toward bacterial (Escherichia coli) and colloidal (polystyrene particles) attachment, non-specific protein (fibronectin) adsorption and cell (3T3 NIH) adhesion was evaluated and was compared with glass slides modified with polyethylene glycol (PEG) brushes, oxidized 3-mercaptopropyltrimethoxysilane (sulfonic acid, SA), and n-octadecyltrichlorosilane (OTS). The extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory and thermodynamic models based on surface energy were used to explain the interaction behaviors of E. coli/polystyrene particles–substrate and protein–substrate interactions, respectively. The cross-linked PSS-PEG film was found to be slightly better than SA and PEG toward resisting non-specific protein adsorption, and showed comparable low attachment results as those of PEG toward particle, bacterial and NIH-3T3 cells adhesion. The low-fouling performance of PSS-PEG, a cross-linked film by a simple thermal curing process, could allow this material to be used for applications in aqueous environments, where most low fouling hydrophilic polymers, such as PSS or PEG, could not be easily retained.

Fouling diatoms of Andaman waters and their inhibition by spinal extracts of the sea urchin Diadema setosum (Leske, 1778)

Diatoms play a central role in biofouling by attracting microscopic reproductive propagules of macroorganisms. This study reports on the seasonal variation of fouling diatoms in waters of the South Andaman Sea and evaluation of their inhibition by spinal extracts of the sea urchin Diadema setosum on glass slides. Pennate diatoms were more abundant than centric diatoms in the fouling film. The genera Navicula and Amphora were dominant throughout the study. Apart from that, an abundance of the genera Cocconeis and Thalassiosira was observed during the pre-monsoon period; Nitzschia was abundant during the monsoon period and Achnanthes and Thalassiosira during the post-monsoon period. Two separate fractions were extracted from the spines using ethanol and distilled water as solvents. The ethanol extract fraction showed inhibition against eight major fouling diatoms. The ethanol extract exhibited a higher inhibitory effect than the aqueous extract against biofilm formation, confirming that the organic fraction has microfouling inhibitory compounds.

Electro-oxidation of chlorophenols at glassy carbon electrodes modified with polyNi(II)complexes

Abstract The effect of the ligand macrocycle (phenylporphyrin (PP) or phthalocyanine (Pc)) and of the ligand substituent ( NH2 or SO3−) on the catalytic activity for the electro-oxidation in a pH 11 buffer electrolyte of 2- and 4-chlorophenol (2-CP and 4-CP), 2,4- and 2,6-dichlorophenol (2,4-DCP and 2,6-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP) at glassy carbon electrodes modified with electropolymerized Ni(II) macrocycles was studied. The polyphenolic residue deposited at the electrode surface was characterized by cyclic voltammetry, impedance measurements, ex situ Fourier transform infrared spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). A band of aliphatic C O stretching in the IR spectrum of the fouling film produced by potential cycling in 2,4,6-TCP indicated that the aromatic ring had been broken, yielding ketones, aldehydes and/or carboxylic acids. The sulphonated Ni(II) polymers, which showed the Ni(III)/Ni(II) process in the CV, had XP spectra typical of paramagnetic Ni(II), indicating that they contained Ni(OH)2 clusters. On the contrary, the CVs of the amino Ni(II) did not show the Ni(III)/Ni(II) process at all, this process appearing only after previous activation by potential cycling, and only to a small extent. As was to be expected, the XP spectra of activated amino films corresponded to diamagnetic Ni(II), showing that the concentration of Ni(OH)2 clusters was very small. The amino films were less active than the sulpho films for the oxidation of chlorophenols, in agreement with the lower concentration of Ni(OH)2 clusters in the former films. For all electrodes the highest activity was observed for 2,4,6-TCP, since its oxidation yields a phenolic residue which is much more porous than those produced by the other CPs.

Investigation of Electro-Oxidation of Methanol and Benzyl Alcohol at Boron-Doped Diamond Electrode: Evidence for the Mechanism for Fouling Film Formation

Boron-doped diamond (BDD) and glassy carbon (GC) electrodes are compared for electrochemical oxidation of methanol and benzyl alcohol. Cyclic voltammograms reveal that BDD electrode produces good oxidation signals for both methanol and benzyl alcohol, while GC produces no significant oxidation signal for either methanol or benzyl alcohol. Amperometric measurement of oxidation of methanol and benzyl alcohol on BDD shows development of a fouling film for benzyl alcohol but not for methanol. Prolonged (24 h) polarization of the BDD electrode at +2.0 V in benzyl alcohol generated enough fouling film for investigation by AFM, SEM, Raman, and FTIR techniques. AFM and SEM microscopy images confirm a fouling film confined to the low-lying regions of the polycrystallite BDD surface, indicating that the active sites of benzyl alcohol oxidation are located within these low-lying regions. The fouling material generated in the process of benzyl alcohol oxidation was identified from Raman and FTIR spectroscopy as polyester. Experiments confirm the fouling film can be removed and the electrode surface reactivated by brief polarization at +3.0 V. Amperometric results of concentration dependence confirm the BDD electrode is well suited for quantitative analysis applications of methanol and benzyl alcohol, with recognizable oxidation currents at micromolar concentration levels.

Nanoparticle aggregation influenced by magnetic fields

Colloidally stable nanoparticle suspensions of iron hydroxide FeO(OH) at pH 2 have been prepared and shown to be non-magnetic. However, when the pH of the dispersion was raised to destabilise the suspension, aggregates near 200 nm diameter were detected by Photon Correlation Spectroscopy (PCS), and these were influenced by magnetic fields in the 50 kA m −1 range. These aggregates were unusual in that they were colloidally stable and did not behave as flocs. Consequently they were called nucleags to distinguish them from conventional flocculated agglomerates. As the pH was raised further towards the isoelectric point, flocculation of the nanoparticles was observed and brown sludge deposited on the base of the container. This material was not influenced by magnetic fields. A preliminary theory has been proposed to account for the observations. The experimental results fitted the curve with a one parameter adjustment. The conclusion was that magnetic fields can influence the behaviour of metastable aggregates in nanoparticle dispersions under certain colloidal conditions. The results may be relevant to deposition of scaling or fouling films in pipes carrying fluids.

Adhesion of Nanoparticles Fouling Glass Surfaces

ABSTRACT The fouling of glass surfaces by nanoparticles formed from corroding iron was studied. Simple experiments demonstrated that adherent films of nanoparticles were deposited by corrosion of iron particles on a glass surface and by flowing water past corroding particles and then onto a glass surface. The water collected from this experiment was found to contain about 2 parts per million (ppm) of particles 500 nm in diameter when tested by photon correlation spectroscopy. However, electron micrographs showed that the primary particles in the fouling film were 20 nm in diameter. This discrepancy was explained by a new theory of nucleation of the fouling films. The theory was confirmed by measuring the particle size of ferric hydroxide dispersions as a function of concentration and pH. It was shown that the 20 nm primary nanoparticles nucleated much larger stable aggregates (defined as nucleags), which were sensitive both to pH and to magnetic fields. In particular, as the pH rose above 6, flocculation occurred, and large unstable agglomerates were observed. The conclusion was that three types of particle could exist in the corrosion product of iron and water: nanoparticles, nucleags, and flocs.

Microbial community structure of membrane fouling film in an intermittently and continuously aerated submerged membrane bioreactor treating domestic wastewater

There was an observable difference in microbial community structure between suspended microorganisms and membrane biofouling film in intermittently and continuously aerated SMBRs. The dominant quinone type of membrane biofouling film in an intermittently aerated SMBR was ubiquinone (UQs)-8, -10 followed by menaquinone (MKs)-8(H4) and -8(H2). But that of the continuously aerated SMBR was UQs-10, -8 followed by MKs-6 and -8(H4). The experimental results also showed that the conditions of an intermittently aerated SMBR may contribute to biofouling by Pseudomonas, Moraxella, Vibrio (quinone type UQ-8), Staphylococcus warneri (quinone type MK-7), Micrococcus sp. (quinone type MK-8(H2)) and Nocardia sp. (quinone type MK-8(H4)), but biofouling in a continuously aerated SMBR may be due to Paracoccus sp. (quinone type: UQ-10) and Flavobacterium species (quinone type: MK-6). The microbial diversities in the intermittently aerated SMBR were 10.9 and 9.4 for biofouling film and suspended microorganisms, respectively. For the continuously aerated SMBR, the results were 10.4 and 10.5 for biofouling film and suspended microorganisms, respectively.

An Electrochemical and Fourier Transform Infrared Spectroscopic Study of the Aqueous Oxidation of Quadricyclane and Nortricyclanol

The aqueous redox chemistry of heptane, commonly known as quadricyclane, and its environmentally important hydrolysis product, nortricyclanol, was investigated through the use of cyclic voltammetry, chronocoulometry, and rotating disk electrochemical methods. Oxidation of both compounds in aqueous environments yields polymeric films that rapidly foul the working electrode. A novel experimental approach was developed to circumvent the problems associated with the formation of the fouling films, which were further characterized using attenuated total reflectance infrared spectroscopy. © 2000 The Electrochemical Society. All rights reserved.

A case study of RO plant failure due to membrane fouling, analysis and diagnosis

Progressive decline in performance of an RO plant, after a period of smooth operation, is described. Research for the reasons and remedy included: 1. Correlation of the recorded decline in performance to problems in feed pretreatment. 2. Selection of elements for individual testing. 3. Elements' performance together with their outer features suggested the conduction of element autopsy. 4. Chemical analysis of the fouling film, Cell Test of the sheet membrane, as well as surface analysis by SEM and X-ray. Results revealed that the membranes suffered from accumulation of an iron-based fouling film. Scale deposition took place due to exceeding the system design parameters together with defective pretreatment. Instead of cleaning, the system was forced by increase of pressure so as to maintain the original product rate. This led to element telescoping and localized damage of the thin film surface. Brief discussion of the adequacy of the techniques used is given in view of the characteristics of membrane fouling films.

Mechanistic interpretation of solute permeation through a fully aromatic polyamide reverse osmosis membrane

The objective of this study was to assess the contribution of various mass transfer steps (concentration polarization, partitioning, and diffusive and convective transport) toward overall permeation of major solute sodium chloride (NaCl), and trace component nitrobenzene across the fully aromatic polyamide FT-30 ® membrane. Experiments were performed with a closed-loop flat-leaf reverse osmosis apparatus. Feed solutions tested contained 2000, 4000 or 6000 mg/l NaCl, and 10 mg/l nitrobenzene at pH 6 and 25°C. Solute rejection ranged from 95 to 99.2% for NaCl and from 20 to 60% for nitrobenzene. The overall permeation of both NaCl and nitrobenzene appeared to be primarily by partitioning at water/membrane interfaces and diffusion across the membrane phase. Convection accounting for less than 25 and 0.4% of the overall NaCl and nitrobenzene permeation, respectively, appeared to be the result of a small leakage of feed solution through membrane imperfections estimated at 0.14% of the overall product water flux. Solute permeation was affected by concentration polarization taking place primarily within a fouling film of corrosion products. Concentration polarization levels corresponded to solute concentrations next to the feed water/membrane interface ranging from 5 to 70% (NaCl), and from 8 to 140% (nitrobenzene) higher than bulk feed concentrations.

Fouling and corrosion in an open recirculating cooling system

The paper discusses the problem of fouling and corrosion in the Service Water System of a nuclear reactor employing an open recirculating cooling system. Field and laboratory experiments were carried out using carbon steel as test material. The studies included corrosion rate measurements, corrosion product characterisation (using XRD, EDAX and IRAS), and the effects of addition of biocide (chlorine) and corrosion inhibitor (polyphosphates) on the bacterial population of the cooling water. The fouling films which developed on metal and glass coupons as well as debris collected from within the cooling system were chemically characterised. The results indicated the prevalence of microbiologically induced corrosion (MIC) within the system. The findings are discussed in the light of the information available on MIC of cooling water systems.

Effects of temperature and ion transport on water splitting in bipolar membranes

We have considered the effects of temperature and ion transport on water splitting in bipolar membranes. The Nernst-Planck equations are employed for the ion fluxes, and the water splitting phenomenon is accounted for by means of either the Onsager theory of the Second Wien Effect or the Chemical Reaction model. Comparison between theory and experiment can be done on the basis of the experimental data by Zabolotskii et al. [Soviet Electrochem., 20 (1985) 1238] . Special attention is paid to the form of the current-voltage curves as well as to the variation of the current carried by the H + and OH − ions with the total electric current. It is found that the predictions derived from the Chemical Reaction model are generally in better agreement with experimental results than those obtained from the Second Wien Effect theory. Finally, we have applied the transport model to a fouled anion exchange membrane exhibiting a bipolar-like structure in order to study the influence of the fixed charge concentration in the fouling film on water splitting.