Surface Fouling Research Articles

Boosting Demulsification and Antifouling Capacity of Membranes via an Enhanced Piezoelectric Effect for Sustaining Emulsion Separation.

Traditional superwettable membranes for demulsification of oil/water emulsions could not maintain their separation performance for long because of low demulsification capacity and surface fouling during practical applications. A charging membrane could repel the contaminants for a while, the charge of which would gradually be neutralized during the separation progress. Here, a superhydrophilic piezoelectric membrane (SPM) with sustained demulsification and antifouling capacity is proposed for achieving prolonged emulsion separation, which is capable of converting inherent pulse hydraulic filtration pressure into pulse voltage. A pulse voltage up to -7.6 V is generated to intercept the oil by expediting the deformation and coalescence of emulsified oil droplets, realizing the demulsification. Furthermore, it repels negatively charged oil droplets, avoiding membrane fouling. Additionally, any organic foulants adhering to the membrane undergo degradation facilitated by the generated reactive oxygen species. The separation data demonstrate a 98.85% efficiency with a flux decline ratio below 14% during a 2 h separation duration and a nearly 100% flux recovery of SPM. This research opens new avenues in membrane separation, environmental remediation, etc.

Non-destructive monitoring and prediction of fouling by organic matters and residual anionic coagulant during membrane process

Physical fouling characteristics on silicon carbide (SiC) membranes induced by various organic matter compounds vary depending on the presence of calcium ions (Ca2+). Both destructive techniques (morphological surface analysis) and non-destructive techniques (fouling properties monitoring) were used to determine the fouling mechanisms and behavior during the membrane filtration systems. Destructive analysis and a modified Hermia model were employed to assess the fouling mechanisms. Fouling behavior was also analyzed through non-destructive monitoring techniques including optical coherence tomography (OCT) and three-dimensional laser scanning confocal microscopy (3D-LSM). At concentrations of 10, 30, and 100 mg/L without Ca2+, the flux decreased by 57–95% for humic acid (HA) and anionic polyacrylamide (APAM). APAM exhibited a notable removal rate of up to 56% without Ca2+. At concentration of 10, 30, and 100 mg/L in the absence of Ca2+, the flux decreased by 6–8% for sodium alginate (SA). However, the addition of Ca2+ led to a reduction in the flux for SA by up to 91% and resulted in a removal rate of 40%. Furthermore, addition of Ca2+ led to an alteration of the fouling characteristics of HA and SA. In the case of HA, higher concentrations resulted in elevated thickness and roughness with correlation coefficients of 0.991 and 0.992, respectively. For SA, increased SA concentration led to a thicker (correlation coefficient of 0.999) but smoother surfaces (correlation coefficients of 0.502). Monitoring of these physical characteristics of the fouling layer through non-destructive analysis is crucial for effective fouling management, optimization of the system performance and extending the lifespan of the membrane. By continuously assessing the fouling layer thickness and surface roughness, we expect to be able to provide insights on the fouling behavior, identify trends, that can help scientists and engineers to make informed decisions regarding fouling control strategies in future.

Improved Photocatalytic Performance of TiO2-Nitrogen-Doped Graphene Quantum Dot Composites Mediated by Heterogeneous Interactions.

Photocatalysis is typically monitored via analysis of phases in isolation and focuses on the removal of a target analyte from the solution phase. Here we analyze the photocatalytic action of a TiO2-nitrogen-doped graphene quantum dot (NGQD) composite on a target analyte, phenol, using comprehensive multiphase NMR (CMP-NMR) which observes signals in solid, solution, and gel phases in situ. Phenol preferentially interacts with the composite photocatalyst compared to pure TiO2, increasing its effective concentration near the catalyst surface and its degradation rate. The presence of NGQDs in the composite reduced the fouling of the catalyst surface and caused a reduction of photogenerated intermediates. Increased heterogeneous interactions, likely mediated by π-π interactions, are hypothesized to cause each of these improvements in the observed photocatalytic performance by TiO2-NGQDs. CMP-NMR allows the elucidation of how the photocatalytic mechanism is enhanced via material design and provides a foundation for the development of efficient photocatalysts.

Photocatalytic Zinc Oxide Nanoparticles in Antibacterial Ultrafiltration Membranes for Biofouling Control.

Global water scarcity is a threat that can be alleviated through membrane filtration technologies. However, the widespread adoption of membranes faces significant challenges, primarily due to membrane biofouling. This is the reason why membrane modifications have been under increasing investigation to address the fouling issues. Antibacterial membranes, designed to combat biofouling by eliminating microorganisms, offer a promising solution. Within this study, flat sheet ultrafiltration (UF) membranes with integrated photocatalytic zinc oxide (ZnO) nanoparticles were developed, characterized, and assessed through filtration and fouling tests. The antibacterial properties of the membranes were conducted in static tests using Gram-negative bacteria-Escherichia coli-and natural tap water biofilm. The results demonstrated a notable enhancement in membrane surface wettability and fouling resistance. Furthermore, the incorporation of ZnO resulted in substantial photocatalytic antibacterial activity, inactivating over 99.9% of cultivable E. coli. The antibacterial activity persisted even in the absence of light. At the same time, the persistence of natural tap water organisms in biofilms of modified membranes necessitates further in-depth research on complex biofilm interactions with such membranes.

Synthesis of peripheral thiol functionalized (NiII) phthalocyanine and its attachment on Au electrode for electrochemical determination of L-DOPA

This paper presents the synthesis, characterization, and electrocatalytic behavior of peripheral thiol-functionalized nickel(II) phthalocyanine (4β-NiIITTPc). The complex was synthesized and characterized using MALDI-TOF mass spectra, UV–visible, and FT-IR spectroscopies. Upon self-assembly on the Au surface from dimethylformamide solution, 4β-NiIITTPc forms via the formation of an Au-S bond. The attachment onto the Au surface was verified through Raman spectroscopy and cyclic voltammetry, with characteristic bands at 2572 and 250 cm−1 corresponding to -SH and Au-S stretching vibrations, respectively. Notably, the -SH stretching indicates that not all four -SH groups of 4β-NiIITTPc are involved in chemisorption. The resulting self-assembled film on the Au electrode exhibits well-defined oxidation peaks at +0.34 V and +0.56 V, corresponding to NiIII/NiII and NiIIPc−1/NiIIPc−2, respectively. The surface coverage was estimated from the charge associated with NiII/NiIII oxidation, yielding 1.01 × 10−10 mol cm−2. Finally, the electrocatalytic activity of the self-assembled monolayer (SAM) of 4β-NiIITTPc on Au electrodes was assessed by studying the oxidation of 3,4-dihydroxy-1-phenylalanine (L-dopa) as a probe. The SAM-modified electrode not only shifts the oxidation potential of L-dopa to a less positive potential but also enhances the oxidation current and mitigates electrode surface fouling compared to the bare Au electrode.

Antifouling strategies for electrochemical sensing in complex biological media.

Surface fouling poses a significant challenge that restricts the analytical performance of electrochemical sensors in both in vitro and in vivo applications. Biofouling resistance is paramount to guarantee the reliable operation of electrochemical sensors in complex biofluids (e.g., blood, serum, and urine). Seeking efficient strategies for surface fouling and establishing highly sensitive sensing platforms for applications in complex media have received increasing attention in the past. In this review, we provide a comprehensive overview of recent research efforts focused on antifouling electrochemical sensors. Initially, we present a detailed illustration of the concept about biofouling along with an exploration of four key antifouling mechanisms. Subsequently, we delve into the commonly employed antifouling strategies in the fabrication of electrochemical sensors. These encompass physical surface topography (micro/nanostructure coatings and filtration membranes) and chemical surface modifications (PEG and its derivatives, zwitterionic polymers, peptides, proteins, and various other antifouling materials). The progress in antifouling electrochemical sensors is proposed concerning the antifouling mechanisms as well as sensing capability assessments (e.g., sensitivity, stability, and practical application ability). Finally, we summarize the evolving trends in the field and highlight some key remaining limitations.

A polymeric-ceramic hybrid membrane with a self-cleaning and super-wettable surface decorated with polypyrrole-G-C3N4 photocatalyst for oily wastewater treatment

Treating oily wastewater is an enormous challenge as it leads to excessive membrane fouling due to the deposition of components of oily feed onto the membrane surface. Hence, the current work has been focused on developing a polymeric-ceramic hybrid membrane with photocatalytic self-cleaning antifouling properties. To yield the desired membrane, a polypyrrole-graphitic carbon nitride (PPy-G-C3N4) photocatalyst was decorated in the polyamide (PA) active layer of the membrane by interfacial polymerization (IP) onto the surface of alumina support. The chemistry of the active layer of the PPy-G-C3N4/PA@Alumina ceramic membrane led to the special wettability feature of being underwater superoleophobic which is reflected by underwater oil contact angle of θO, W = 159.9°. Even though the membrane surface features do not allow the oil to wet the membrane surface during filtration, the membrane surface fouling was inevitable during filtration experiments. With distilled water as feed, the permeate flux of PPy-G-C3N4/PA@Alumina ceramic membrane reached 650 L m−2 h−1 (LMH) at a pressure of 8 bar. A separation efficiency of >99 % was observed by using a feed of 100 ppm oil-in-water (O/W) emulsion. However, the permeate flux declined while using O/W emulsion as feed, where a 92 LMH to 50 LMH was observed after 60 min of continuous filtration. The performance of the membrane was recovered after exposure to solar-simulated light owing to the presence of PPy-G-C3N4 photocatalyst in the active layer where a recovery of ∼90 % of permeate flux was recorded. Hence, the current approach of fabricating a hybrid membrane proved to be useful for efficiently treating a challenging feed consisting of a complex oily matrix.

Inducing Deep Sweeps and Vortex Ejections on Patterned Membrane Surfaces to Mitigate Surface Fouling.

Patterned membrane surfaces offer a hydrodynamic approach to mitigating concentration polarization and subsequent surface fouling. However, when subjected to steady crossflow conditions, surface patterns promote particle accumulation in the recirculation zones of cavity-like spaces. In order to resolve this issue, we numerically subject a two-dimensional, patterned membrane surface to a rapidly pulsed crossflow. When combined with cavity-like spaces, such as the valleys of membrane surface patterns, a rapidly pulsed flow generates mixing mechanisms (i.e., the deep sweep and the vortex ejection) and disrupts recirculation zones. In only four pulses, we demonstrate the ability of these mechanisms to remove over half of the particles trapped in recirculation zones via massless particle tracking studies (i.e., numerical integration of the simulated velocity field). The results of this work suggest that when combined with a rapidly pulsed inlet flow, patterned membrane surfaces can not only alleviate concentration polarization and the surface fouling that follows but also reduce the need for traditional cleaning methods that require operational downtime and often involve the use of abrasive chemical agents.

Parametric investigation of ultrashort pulsed laser surface texturing on aluminium alloy 7075 for hydrophobicity enhancement

Hydrophobicity plays a pivotal role in mitigating surface fouling, corrosion, and icing in critical marine and aerospace environments. By employing ultrafast laser texturing, the characteristic properties of a material’s surface can be modified. This work investigates the potential of an advanced ultrafast laser texturing manufacturing process to enhance the hydrophobicity of aluminium alloy 7075. The surface properties were characterized using goniometry, 3D profilometry, SEM, and XPS analysis. The findings from this study show that the laser process parameters play a crucial role in the manufacturing of the required surface structures. Numerical optimization with response surface optimization was conducted to maximize the contact angle on these surfaces. The maximum water contact angle achieved was 142º, with an average height roughness (Sa) of 0.87 ± 0.075 µm, maximum height roughness (Sz) of 19.4 ± 2.12 µm, and texture aspect ratio of 0.042. This sample was manufactured with the process parameters of 3W laser power, 0.08 mm hatch distance, and a 3 mm/s scan speed. This study highlights the importance of laser process parameters in the manufacturing of the required surface structures and presents a parametric modeling approach that can be used to optimize the laser process parameters to obtain a specific surface morphology and hydrophobicity.

A superior anti-fouling electrode sensing layer based on a tannic acid–polyethyleneimine–graphene oxide nanocomposite for thrombin detection in complex biological fluids

Affinity-peptide-based electrochemical sensors have emerged as promising alternatives to conventional methods because of their superior stability, chemical adaptability, and selectivity. However, their rapid loss of sensitivity caused by inactivation of the electrode surface and biological fouling has hindered their further development. To address this issue, we fabricated a sensitive and selective bifunctional peptide-based electrochemical sensor that enables thrombin detection in complex biological fluids. To achieve this, we incorporated a nanohybrid hydrogel composed of cross-linked polyphenol (tannic acid, TA) and polyamine (polyethyleneimine, PEI) co-deposition systems containing a nanomaterial (graphene oxide, GO) into the biosensor as an anti-fouling layer. The TA-PEI-GO nanohybrid hydrogel enhanced the electron transfer process and selectivity of the biosensor, while preventing the adsorption of non-specific biomolecules. As a result, the stability of the electrode surface was improved, and functionalization of the active sites for engineered peptides was achieved in a highly oriented manner. The stability, simplicity, and ease of preparation of this nanohybrid hydrogel render it a suitable candidate for the fabrication of electrochemical biosensors that can function in complex biological fluids. The developed biosensor has the potential to facilitate the diagnosis and prognosis of coagulation disorder-related diseases, which would have a positive effect on public health.

Surface-segregating zwitterionic copolymers to control poly(dimethylsiloxane) surface chemistry.

The use of microfluidic devices in biomedicine is growing rapidly in applications such as organs-on-chip and separations. Polydimethylsiloxane (PDMS) is the most popular material for microfluidics due to its ability to replicate features down to the nanoscale, flexibility, gas permeability, and low cost. However, the inherent hydrophobicity of PDMS leads to the adsorption of macromolecules and small molecules on device surfaces. This curtails its use in "organs-on-chip" and other applications. Current technologies to improve PDMS surface hydrophilicity and fouling resistance involve added processing steps or do not create surfaces that remain hydrophilic for long periods. This work describes a novel, simple, fast, and scalable method for improving surface hydrophilicity and preventing the nonspecific adsorption of proteins and small molecules on PDMS through the use of a surface-segregating zwitterionic copolymer as an additive that is blended in during manufacture. These highly branched copolymers spontaneously segregate to surfaces and rearrange in contact with aqueous solutions to resist nonspecific adsorption. We report that mixing a minute amount (0.025 wt%) of the zwitterionic copolymer in PDMS considerably reduces hydrophobicity and nonspecific adsorption of proteins (albumin and lysozyme) and small molecules (vitamin B12 and reactive red). PDMS blended with these zwitterionic copolymers retains its mechanical and physical properties for at least six months. Moreover, this approach is fully compatible with existing PDMS device manufacture protocols without additional processing steps and thus provides a low-cost and user-friendly approach to fabricating reliable biomicrofluidics.

Impact of gate electrode on free chlorine sensing performance in solution-gated graphene field-effect transistors.

Free chlorine is widely used to disinfect water used for drinking and food processing. This requires highly sensitive, simple, and capable continuous-measurement sensors to enable the concentration of free chlorine in water to be monitored and controlled. Free chlorine sensors based on solution-gated graphene field-effect transistors (GFETs) are a suitable platform for highly sensitive and continuous measurements. However, their sensing mechanisms require further elucidation to improve their performance. In this study, we focused on the gate electrode and investigated its influence on the sensing performance. Using the free chlorine sensor based on the solution-gate GFET, we showed that the Dirac point voltage in the transfer curve changed significantly as the free chlorine concentration changed, and the electric double-layer capacitance of the gate electrode decreased. Furthermore, we demonstrated that a solution-gated GFET using graphene or boron-doped diamond as the gate electrode could be used to detect changes in the free chlorine concentration in the concentration range of tap water. The sensing performance in the low concentration range benefits from the wide potential window of carbon-based electrodes, which do not have electrochemically active sites. Using these carbon-based materials as gate electrodes, GFETs have the potential to be used as durable sensors that are resistant to surface fouling and oxidation.

Novel protocol for fouling detection of reverse osmosis membrane based on methylene blue colorimetric method by image processing technique.

In the current study, a novel methylene blue (MB)-based colorimetric method for a quick, inexpensive, and facile approach for the determination of fouling intensity of reverse osmosis (RO) membrane has been reported. This technique is based on the interaction of MB with the organic foulants and shows the corresponding change in the colour intensity depending on the severity of fouling. The organic foulants, such as albumin, sodium alginate, and carboxymethyl cellulose (CMC), were chosen as model foulants, and the membranes were subjected to foul under extreme fouling conditions. The fouled membranes underwent an MB treatment followed by image-processing analyses. The severity of surface fouling of membranes was evaluated in terms of fouling intensity and correlated with the corresponding decline of permeate flux. The maximum fouling intensity of the albumin, sodium alginate, and CMC sodium were found to be 8.83, 23.38, and 9.19%, respectively, for the definite concentration of foulants. The physico-chemical interactions of the given foulants and MB were confirmed by changes in zeta potentials and increased sizes of the foulant by the dynamic light scattering technique. The surface fouling over the membrane surface was confirmed by the characterization of membranes.

A bubble energy generator featuring lubricant-impregnated surface with high durability and efficiency

Harvesting bubble energy emerges as a potential sustainable solution to harness tremendous marine energy sources. Yet, current bubble energy generators are susceptible to unstable performance owing to the degradation of the physiochemical properties of surface materials under the harsh underwater environment such as surface fouling and wetting transition. Here, we report the design of bubble energy generators featuring the cooperative integration of a slippery lubricant-impregnated porous surface and transistor-inspired architecture, referred to as SLIPS-TBG, that can generate electricity from moving bubbles with high stability in submerged conditions. In this design, the slippery and configurable lubricant layer serves as not only a smooth and mechanically stable surface for bubble transport but also a protective layer preventing the underlying solid materials from direct contact with the external harsh environment. Together with the transistor-inspired architecture, the SLIPS-TBG can deliver a stable electric output of 26.4 V, an instantaneous peak power density of 58.6 W m-3 from continuous bubble impingement in water media, even in extreme conditions involving mechanical abrasion and corrosion. We envision such a design represents a significant step toward real-life applications for bubble-based energy harvesting.

(Invited) Voltammetric Measurement of Neuropeptides and Neurohormones with Carbon-Fiber Microelectrode Biosensors

Carbon fiber microelectrodes (CFMEs) have been used to detect neurotransmitters and other biomolecules using fast-scan cyclic voltammetry (FSCV) for the past several years. 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, pleiotropic peptide hormones, that are physiologically important for adaptation, development, reproduction, and social behavior. These neuropeptides function as a stress-coping molecules, an anti-inflammatory agents, and serves as antioxidants with protective effects especially during adversity or trauma. Here, we measure tyrosine within these neuropeptides 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.Cortisol is also a vital steroid neurohormone that has been known as the “stress hormone,” which is elevated during times of high period of anxiety which is biologically critical. The enhanced detection of cortisol is fundamentally important as it will help further our understanding of stress during several physiological states. Several methods exist to detect cortisol, however, they suffer from low biocompatibility and spatiotemporal resolution and are relatively slow. In this study, we developed an assay to detect cortisol CFMEs and FSCV. FSCV is typically utilized to measure small molecule neurotransmitters by producing a readout cyclic voltammogram (CV) for the specific detection of biomolecules on a fast, sub second timescale with biocompatible CFMEs. It has seen enhanced utility in measuring peptides and other larger compounds. We developed a waveform that scanned from -0.5 V to -1.2 V at 400 V/sec to electro-reduce cortisol at the surface of CFMEs. The sensitivity of cortisol was found to be 0.87 +/- 0.05 nA/μM (n=5) and was found to be adsorption controlled on the surface of CFMEs and stable over several hours. Cortisol was able to be co-detected with several other biomolecules such as dopamine, and the waveform was fouling resistant to repeated injections of cortisol on the surface of the CFMEs. Furthermore, we also measured exogenously applied cortisol into simulated urine to demonstrate biocompatibility and potential use in vivo. The specific and biocompatible detection of cortisol with high spatiotemporal resolution will help further elucidate its biological significance and further understand its physiological importance.

Flow-Thermal-Strength Analysis of the Finned Tube Heat Exchanger Operation

Ensuring the safety and adequate service life of thermal power equipment, in addition to the need to maintain the required operating parameters, are among the most important issues related to the heat exchanger operation. This also applies to heat exchangers with extended surfaces, which are usually achieved by finned tubes. They are typically used where heat is exchanged between working fluids characterized by quite different properties, such as gas-water or air-coolant fluids. The high parameters of these fluids (temperature, pressure), occasionally their aggressiveness, and often the salts they contain, causing fouling of surfaces, can be the cause of failures. Among the most common are tube failures, which can lead to severe consequences. The developed methodology of coupled flow-thermal and strength analysis was used in exemplary calculations for a two-pass, two-row combustion gas - water heat exchanger with finned elliptical tubes. The reason for choosing such a design, was the fact of having failure data for two similar designs. This allowed verification of the correct operation of the developed methodology and redesign the heat exchanger manifold to ensure better flow distribution in a tubular space and better stress distribution.

4-Aminophenylboronic acid dimer sensitized carbon nanotubes for the construction of portable and disposable sulfide electrochemical sensors

Abnormal sulfide levels in serum can cause kidney failure, Alzheimer's, Parkinson's, stroke, diabetes, and even cancer. Therefore, maintaining proper sulfide balance is crucial for managing and preventing these conditions. Electrochemical approaches have emerged as potential alternatives for sulfide detection. However, the adsorption of elemental sulfur on the working electrode leads to surface fouling and passivation, posing a significant challenge in developing reliable electrochemical methods for sulfide detection. In this study, we present a portable and surface fouling-free electrochemical system that utilizes functionalized multi-walled carbon nanotubes and 4-aminophenylboronic acid dimers for accurate sulfide measurement. The sensor showed excellent electrocatalytic activity to sulfide and antifouling activity to possible interferences. The method had a linear range from 10 µM to 2 mM and a detection limit of 2.3 µM. The effectiveness and applicability of this method were evaluated by analyzing sulfide levels in different serum samples and comparing the results with their glucose levels. As both blood glucose and sulfide levels can serve as indicators of certain health conditions, such as diabetes or sulfur metabolism disorders, this comparison provides valuable insights. Importantly, no complicated sample pretreatment was involved, thus this method can be easily adopted as a point-of-care diagnostic device. Additionally, the study also revealed a higher concentration of sulfide in cancer cells than in normal cells, offering a new development direction for differentiating between cancer cells and normal cells.

Preparation of super hydrophilic-underwater super oleophobic photoinduced self-cleaning Al2O3 @TiO2 ceramic membrane and separation performance of oil-in-water emulsion

Membrane hydrodynamic irreversible oil fouling is a pressing issue. Here, an antifouling Al2O3 @TiO2 membrane with excellent wettability was created using the sol-gel method to create an anatase nano-TiO2 coating on the surface of an Al2O3 ceramic membrane. Analyzing the separation performance of an Al2O3 @TiO2 membrane on simulated oily emulsions determined the amount of TiO2 covered on the membrane surface (0.8 mol·L−1). Under the synergy of hydrophilic nano-TiO2 and ultraviolet (UV) light, the Al2O3 @TiO2 membrane demonstrated improved wettability and self-cleaning ability and maintained favorable separation performance (769.23 L·m−2·h−1, 97.75%, 1.23 mg·L−1) after 6 h of continuous separation of the actual oilfield produced water. After 30 min of UV illumination, the membrane flux recovered completely. This is due to the fact that the active substances (eg.,·OH,·O2, and 1O2) generated in situ on TiO2 on the membrane surface after UV illumination weakened the interaction of membrane surface fouling, resulting in less oil fouling. In addition, the Al2O3 @TiO2 membrane maintained extremely outstanding oil resistance stability and recoverability during high-intensity hydraulic flushing and 25 cycles of testing. This study provides a theoretical basis for the engineering application of ceramic membranes in oilfield-produced water treatment.

Hybrid-process including electrocoagulation for the real carwash wastewater treatment using a new continuous undivided tubular reactor

A coagulation-based continuous tubular electrochemical reactor has been designed to treat real carwash wastewater in a flow rate of 100 mL/min. This reactor made of an ordinary iron tube cathode with a commercial aluminum rod anode at the center. Equipment and chemicals needed for this method can be easily and cheaply obtained through non-scientific commercial sources. The one-factor at a time approach was used to investigate the effects of operating variables. Current density, flow rate, electrolysis time and electrode material were selected as independent variables while COD removal was considered as the response function. The experimental results showed that the proposed method can remove 89 % of COD from 10 liters of carwash wastewater in a "single-pass" and more than 99 % in a "double-pass" through the flow reactor. This reactor has short treatment time, low energy consumption, favorable mass transfer and low ohmic drop and does not need to adjust the pH or add electrolyte additionally to save costs. Also, this approach is resistant to undesirable phenomena such as passivation of the electrode surface, cell polarization, electrode surface fouling and reduction of electrical conductivity that may occur during electrolysis. The treated wastewater can be reused in the carwash industry as well as for irrigated agriculture.

Advances in laser-based surface texturing for developing antifouling surfaces: A comprehensive review

Surface fouling is a major challenge faced within various engineering applications, especially in marine, aerospace, water treatment, food and beverage, and the energy generation sectors. This can be prevented or reduced in various ways by creating artificial surface textures which have fouling resistance properties. Ultrafast laser texturing provides an efficient method for the texturing of surfaces of different materials with high accuracy, precision, and repeatability. Laser texturing methods can enhance the production of well-defined surface nano- and microscale patterns. These surfaces with nano- and micro-scale patterning can be tailored to have inherent properties such as hydrophobicity, hydrophilicity, and resistance to fouling. This review gives an overview of the various types of fouling that can occur, the properties affecting a surface's fouling resistance, as well as the latest physical and chemical strategies for the generation of antifouling surfaces. Surfaces architectures which have inherent antifouling capabilities are presented. This review focuses on the utilization of the higher precision laser-based texturing offered from femtosecond laser systems for enhance fouling resistance. The process parameters to fabricate these textures and the current state of art femtosecond laser sources are presented and discussed. The challenges and future research requirements in the field of laser-based methods to fabricate antifouling surfaces are presented.