Surface Fouling Research Articles

Interplay of organic components in membrane fouling evolution: Statistical evidence from multiple spectroscopic analyses

Membrane fouling is a complex process that can be caused by multiple organic foulants such as polysaccharides, proteins and humic substances. The key mechanisms, especially interactions between coexisting foulant components, have yet to be well understood. This study proposes a combination of spectral and statistical methods to unravel the interactive role of typical organic foulants during microfiltration, taking bovine serum albumin (BSA), humic acid (HA) and sodium alginate (SA) as examples. Results show that the membrane effluent spectra (ultraviolet absorption, fluorescence and circular dichroism) can differentiate the state of foulant interception at the pore adsorption/blocking stage (BSA and HA actively involved) and gel/cake layer stage (SA dominant). Multivariate redundancy analysis revealed interrelations between the spectral characteristics of the effluent and surface fouling layer. Accumulation of proteins and polysaccharides in the fouling layer was detected by infrared spectroscopy while that of humics was more sensitively reflected by Raman spectroscopy, as confirmed by nonnegative linear least square fitting of time-series spectral data during fouling evolution. A variance partitioning analysis nested in multiple linear regression of the infrared or Raman signals offered further statistical evidence for the interplay of organic components by quantifying the single/double/triple-component contributions to the total fouling response. It revealed that ternary BSA × HA × SA interplay is prominent at the initial pore adsorption/blocking stage whereas binary HA × SA interplay prevails at the later gel/cake layer stage. Such role shifting of foulant interactions during the fouling process might provide useful information for a more accurate understanding and control of fouling. The combined spectral and statistical methods, which can effectively trace inter-component relations and link molecular fingerprints to fouling behavior, are particularly promising for exploring fouling mechanisms in complex systems.

Membrane fouling behaviors and evolution during food waste digestate treatment

Membrane technology has been used in the treatment of digestate from food waste (DFW), but membrane fouling has limited its industrial applications. In particular, the complexities of DFW lead to complicated fouling mechanisms. In this study, DFW was separated into three fractions including supernatant substances (SS), bound substances (BS), and the Pellet. The physicochemical characteristics of each fraction were analyzed systematically. Dead-end filtration was conducted and a combined fouling model was employed to quantitatively describe the fouling evolution. The fouling of the membrane surface and the pores was analyzed separately. The results indicated that the SS fraction accounted for more than 60% of the total solids in the DFW. During the dead-end filtration, the SS solution quickly formed a denser cake on the membrane surface, leading to a rapid decay in the flux. The interaction between Ca2+ and polysaccharides in the BS fraction resulted in colloids with a broader particle size distribution between 120 and 6400 nm. These colloids can block the membrane pores and were difficult to remove. Membrane fouling caused by the Pellet solution was not serious because of its high ash content and hydrophobicity. Ca2+ removal via a pretreatment process could prevent pore blocking and thus prevent irreversible membrane fouling.

Fouling studies on hydrophobic PVDF-bentonite hollow fiber membrane during membrane distillation of palm oil mill effluent

Membrane distillation (MD) is one of the emerging methods that can be adopted for oily wastewater treatment. However, the problems associated with membrane surface fouling may impede its separation efficiency. In this work, we performed a fouling study using self-synthesized polyvinylidene difluoride (PVDF)-bentonite hollow fiber membrane (HFM) to treat palm oil mill effluent (POME) via direct contact membrane distillation (DCMD). To date, there is no report on POME treatment using MD technology based on PVDF-bentonite HFM. The fouling tendency was identified based on the membrane's permeate flux and pollutant rejection. The fouled membranes after POME treatment were characterized based on its morphology, functional group, water contact angle, surface roughness and mechanical strength. The results showed that the average permeate flux of MD was 3.34 kg/m2·h over 72-h operation. The membrane showed good performance in separating pollutants with >95 % removal rate recorded for chemical oxygen demand, nitrate nitrogen, total suspended solid, total dissolved solid, color and turbidity. However, based on the post-characterization analysis, the used membranes still suffered from fouling after 72-h DCMD test. Thus, an in-depth investigation into the prevention and control of membrane fouling is still necessary for the POME treatment using DCMD.

A phenomenological study and comparison of the characteristics of droplet impact liquid film dynamics on randomly rough surfaces

The fouling of aero-engine blades is the main cause of degradation of engine performance and online washing is one of the most effective methods for restoring engine performance. The flow characteristics of the washing fluid after it impinges on the blade surface are critical to the process. The liquid film flow becomes complicated after being impacted by a droplet, because the fouling blade is a random rough surface. The purpose of this study is to evaluate the dynamical characteristics of droplets after they impact the liquid film, focusing on the diameter, the height of the coronal water bloom, and the near-wall flow. We establish a random rough surface to simulate the droplet impacting the liquid film on the fouling surface and analyze the morphological evolution of the corona during the droplet impact process. The results show that an increase in the particle size has a greater impact on the coronal diameter than the coronal height. In addition, a higher droplet impact velocity and thicker liquid film are conducive to the secondary atomization of droplets and improve the transport rate of the cleaning solution. However, the flowability of the liquid film at the impact point is best when the droplet impacts the thin liquid film. Increasing the thickness of the liquid film gradually helps to improve its overall fluidity and results in a better cleaning effect.

General mechanism and mitigation for strong adhesion of frozen oil sands on solid substrates

Oil sands adhered on truck bed reduce transport capacity of the truck, require manual cleaning, and create hurdles for automated surface mining. Study on the adhesion properties of oil sands to solid substrates is important to minimize the fouling of substrates during mining operation. In this work, we study the influence of hydrophobicity and mechanical properties of the substrates on the adhesion strength of frozen oil sands. By using an adhesion force apparatus with temperature control, we measure the adhesion strength of both ice and frozen oil sands on six types of substrates with water contact angle from ∼20° to ∼130° and Young’s modulus from a few MPa to 300 GPa. A clear linear correlation between the adhesion strength of pure ice and that of frozen oil sands is observed. Furthermore, the adhesion strength increases with the load on the oil sands sample, and reaches a plateau at ∼450 kPa. The maximum adhesion strength may be due to the limit of particle packing of oil sands. We also demonstrate that spray coating of anti-freezing liquids is effective for the mitigation of the adhesion of frozen oil sands. Substrates coated with various anti-freezing liquids showed undetectable oil sands adhesion strength at -20 °C with 0.06 MPa of load. The study on oil sands adhesion and potential fouling mitigation method may provide a potential solution to industries looking to reduce fouling of surfaces by frozen granular matter.

Investigation of rough-wall turbulence over barnacle roughness with increasing solidity using direct numerical simulations

Surface fouling by marine organisms such as barnacles has a major impact on the shipping sector. We use direct numerical simulations to investigate how the fluid dynamical properties of a surface change as it is gradually covered by barnacle colonies. The roughness effect peaks at intermediate coverage when approximately half of the surface is covered by barnacles. We further investigate how the roughness is perceived by the outer part of the flow using the blanketing layer concept and find a linear relationship between the roughness function and the effective slope of the blanketing layer.

Confining Nano-Fe3O4 in the Superhydrophilic Membrane Skin Layer to Minimize Internal Fouling.

Membrane surface fouling is often reversible as it can be mitigated by enhancing the crossflow shear force. However, membrane internal fouling is often irreversible and thus more challenging. In this study, we developed a new superhydrophilic poly(vinylidene fluoride) (P-PVDF) membrane confined with nano-Fe3O4 in the top skin layer via reverse filtration to reduce internal fouling. The surface of the P-PVDF membrane confined with nano-Fe3O4 had superwetting properties (water contact angle reaching 0° within 1 s), increased roughness (from 182 to 239 nm), and enhanced water affinity. The Fe3O4@P-PVDF membrane surface showed a thicker and enhanced hydration layer, which prevented foulants from approaching membrane surfaces and pores, thereby improving the rejection. For example, when 50 ppm humic acid (HA) solution was used as the feed, the removal efficiency of the Fe3O4@P-PVDF membrane was ∼67%, while the HA removal of the P-PVDF membrane was only ∼20%. The results from the resistance-in-series model showed that nanoconfinement of Fe3O4 in the top skin layer of the membrane allowed foulants to accumulate on the membrane surface (i.e., surface fouling) rather than within the internal pores (i.e., internal fouling). The filtration results under crossflow fouling and cleaning confirmed that the Fe3O4@P-PVDF membrane had higher surface fouling but it was much more reversible and much lower internal fouling compared with the control membrane. Our fouling analysis offers new insights into mass transfer mechanisms of the membrane with a nanoconfinement-enhanced hydration layer. This study provides an effective strategy to develop membranes with low internal fouling propensities.

Scaling control by using ultrasonic guided waves

Fouling of heat exchanger surfaces is a major concern in the industry, resulting in performance losses through a decrease in the overall heat exchange coefficient. Control methods exist but are costly and have a strong environmental impact. Thus, the use of physical treatments is very promising, because the action is done on the clogged surface, in the bulk or in the solution. The present study shows the influence of ultrasonic guide waves on the crystallization of calcium carbonate inside a plate heat exchanger from scaled water. An experimental pilot was set up to study the scaling phenomenon. Several operating parameters such as flow rate, duration, and temperature were experimentally varied in order to identify their influence on the scale deposition in the heat exchanger. Subsequently, a thermodynamic prediction was performed by geochemical modeling using the Phreeqc software in order to get an idea of the nature of the deposit formed after the heating of scaled water. The main objective of this work was the determination of the impact of ultrasonic treatment on the mineral deposit, qualitatively and quantitatively. Therefore, four types of experiments lasting three days are presented in this paper to experimentally show the influence of ultrasound generated by a 35–50 kHz transducer on scale formation. The amount of solid deposited in grams/per day/area, the polymorphism of the formed crystals, and the number, size and size distribution of the particles were analyzed. Disassembly of the exchanger allowed access to the distribution of scale on the plates, and thus justified the choice of location for the 35–50 kHz transducer. It was also possible to estimate the thickness of the scale experimentally by 3D digital microscopy and to ensure the absence of microcrystals in the pores of the plate by analyzing the surface roughness. The results obtained were compared to the experimental measurements with and without the presence of the 35–50 kHz transducer. This allowed the evaluation of the effect of guided ultrasonic waves for the prevention of scale deposits. The presence of a single medium power transducer reduced mineral scale deposition in a plate and gasket heat exchanger by 76%.

Reduction and Elimination of Humic Acid Fouling in Air Sparged Membrane Distillation Using Nanocarbon Immobilized Membrane.

In this paper, we present the treatment of humic acid solution via carbon nanotube immobilized membrane (CNIM) distillation assisted by air sparging (AS). Carbon nanotubes offer excellent hydrophobicity to the modified membrane surface and actively transport water vapor molecules through the membrane to generate higher vapor flux and better rejection of humic acid. The introduction of air sparging in the membrane distillation (MD) system has changed the humic substance fouling by changing the colloidal behavior of the deposits. This modified MD system can sustain a higher run time of separation and has enhanced the evaporation efficiency by 20% more than the regular membrane distillation. The air sparging has reduced the deposition by 30% in weight and offered lesser fouling of membrane surface even after a longer operating cycle. The water vapor flux increased with temperature and decreased as the volumetric concentrating factor (VCF) increased. The mass transfer coefficient was found to be the highest for the air sparged—carbon nanotube immobilized membrane (AS-CNIM) integrated membrane distillation. While the highest change in mass transfer coefficient (MTC) was found for polytetrafluoroethylene (PTFE) membrane with air sparging at 70 °C.

Surface and pore co-functionalized ceramic membrane with nitrogen doped carbon for enhanced water treatment through coupling peroxymonosulfate activation

Endowing membrane with peroxymonosulfate (PMS) activation function is valid for enhancing membrane selectivity and mitigating membrane fouling. However, the current catalytic membranes with only surface-modification suffer from limited catalytic performance and poor pore blocking inhibition. In this work, a ceramic membrane with surface and pore co-functionalized by nitrogen doped carbon (CM@NC) displaying PMS activation capability was firstly fabricated for enhanced water treatment. The pore-functionalization degree was tuned through changing the coating times or precursor concentration to study its effect on membrane performance. Results showed boosting the coating times or precursor concentration improved the membrane performance. Under optimal condition, the CM@NC filtration combined with PMS activation (MFPA) could achieve 100% phenol removal within a short retention time of 14.5 s, whose performance was 8.0 or 1.4 times higher than that of filtration alone or only surface-functionalized CM@NC MFPA. The CM@NC MFPA also effectively resisted both surface and pore fouling caused by humic acid, whose permeate flux was 5.0 times higher than that of filtration alone. The pore-functionalization in CM@NC provided more exposed active sites, extended reaction time and accelerated mass transfer under the confinement effect in modified pores, which promoted reactive species (mainly 1O2) production for pollutant removal and fouling resistance.

Fouling of mammalian hair fibres exposed to a titanium dioxide colloidal suspension.

Fouling of surfaces in prolonged contact with liquid often leads to detrimental alteration of material properties and performance. A wide range of factors which include mass transport, surface properties and surface interactions dictate whether foulants are able to adhere to a surface. Passive means of foulant rejection, such as the microscopic patterns, have been known to develop in nature. In this work, we investigate the anti-fouling behaviour of animal fur and its apparent passive resistance to fouling. We compare the fouling performance of several categories of natural and manufactured fibres, and present correlations between contamination susceptibility and physio-mechanical properties of the fibre and its environment. Lastly, we present a correlation between the fouling intensity of a fibre and the cumulative impact of multiple interacting factors declared in the form of a dimensionless group. Artificial and natural hair strands exhibit comparable anti-fouling behaviour in flow, however, the absence of flow improves the performance of some artificial fibres. Among the plethora of factors affecting the fouling of fur hair, the dimensionless groups we present herein provide the best demarcation between fibres of different origin.

Experimental study on fouling inhibition characteristics of a variable frequency electromagnetic field on the CaCO3 fouling of a heat transfer surface

Forced convective heat transfer and CaCO3 deposition experiments were performed to investigate fouling inhibition characteristics of a variable frequency electromagnetic field on the CaCO3 fouling of a heat transfer surface and three indicators, namely, fouling resistance, conductivity, and scanning electron microscope (SEM), were analyzed. Experimental results indicated that the variable frequency electromagnetic field could effectively inhibit the CaCO3 fouling deposition on the heat transfer surface and slow down the growth rate of CaCO3 fouling by influencing aqueous solution and fouling forming ions. Moreover, the variable frequency electromagnetic field could reduce the conductivity of the test fluid, increase both the total precipitation and the bulk precipitation, and promote the CaCO3 crystallization in aragonite rather than calcite to form muddy soft fouling that was readily washed off by the fluid flow. An evaluation model was proposed to better define the fouling inhibition effect of the variable frequency electromagnetic field in the whole period of CaCO3 deposition. The fouling inhibition characteristics of the variable frequency electromagnetic field presented an extremum feature. The minimum fouling resistance was 1.1 × 10−4 m2⋅K/W obtained at 1 kHz, during which the fouling inhibition rate was 64.7% and the average growth rate of CaCO3 fouling dramatically decreased by 61.0% compared with that of the blank test. This work can provide sound theoretical guidance for future application of electromagnetic fouling inhibition technology in the heat transfer enhancement.

Antifouling superhydrophobic surfaces with bactericidal and SERS activity

• A multifunctional superhydrophobic surface is fabricated using fluorine-free eco-friendly materials. • The superhydrophobic surface is extremely repellent to liquids, including most liquid food. • Deposition of Ag imparted SERS and antibacterial activity. • The superhydrophobic surface reduces residual food waste. • The superhydrophobic surface showed excellent chemical stability. Fouling and contamination of surfaces are prevailing challenges humanities facing today in fields such as healthcare, hospitality, and food manufacturing. These challenges strongly motivate the development of multifunctional surfaces with antifouling and antimicrobial properties that are coupled with sensing capabilities. To address this challenge, we prepared a multifunctional superhydrophobic surface using eco-friendly materials: polydimethylsiloxane (PDMS) and carnauba wax. After deposition of a thin film of Ag, the surface gained surface-enhanced Raman scattering (SERS) activity and bactericidal property. The multifunctional superhydrophobic surface showed extreme liquid repellency towards water and common liquid food. The strong SERS activity enabled the detection of adulterant rhodamine B in a sausage down to a nanomolar level. Notably, the surface showed excellent bactericidal activity towards two common bacteria, E. coli, and S. aureus, significantly reducing their adhesion and killing. Additionally, the surface showed anti-fouling behavior against common liquid food, and even towards sticky foods such as yogurt, honey, and pomegranate sauce, reducing residual food by >97 %. Furthermore, the superhydrophobic surface showed excellent chemical stability in dynamic and static flow conditions and leaching of Ag in neutral and basic solutions was minimal.

Temperature-dependent dynamic fouling on superhydrophobic and slippery nonwetting copper surfaces

• Presents, for the first time, temperature-dependent dynamic fouling on nonwetting surfaces. • Elucidates, for the first time, effects of texturing method and surface type on fouling behavior. • Nonwetting surfaces show up to 75% less scaling compared to regular surfaces. • Electrodeposited surfaces offer better scaling resistance compared to etched surfaces. • Presents Hill-Langmuir model, for the first time, to describe the time evolution of scaling. Bioinspired, superhydrophobic and slippery liquid infused surfaces that offer nonwetting characteristics have been explored in recent years for fouling mitigation. However, most of the studies are in the context of biofouling or under static immersion at ambient temperature conditions that are not reflective of the dynamic flow environment in practice. This article presents, for the first time, a systematic study of dynamic fouling of superhydrophobic (SHS) and slippery lubricant-infused surfaces (LIS) over a range of flow and temperature conditions. Copper metallic surfaces were textured via electrodeposition or etching and further functionalized to achieve SHS and, additionally, infiltrated with a lubricant to fabricate LIS. The nonwetting surfaces were studied for their fouling behavior in a rotating Couette flow of a supersaturated calcium sulfate solution at different rotational speed and temperature. Fouling mineral mass accumulation on the different surfaces was measured as a function of time over a period of days using inductively coupled plasma mass spectroscopy and the fouled surfaces were investigated using scanning electron microscopy. Both SHS and LIS showed superior anti-scaling performance at all ranges of variables. An analytical Hill-Langmuir model is presented, for the first time, to describe the time evolution of scaling within 20% accuracy over the range of parameters studied. The study is the first to juxtapose two surface texturing methods, electrodeposition and etching, and two nonwetting surface types, SHS and LIS, subject to a common suite of experiments to elucidate fundamental understanding of mineral fouling on nonwetting surfaces.

Electrochemically Assaying Dopamine with p-Doped Silicon Nanowires

Neuroblastoma, a pediatric cancer, is characterized by high urinary excretion of dopamine (DA). Silicon nanowires (SiNWs), which are nontoxic and known to resist surface fouling in biological samples, were investigated for practical use as working electrode materials to assay dopamine. Undoped, p-doped, and n-doped SiNWs were deposited onto glassy carbon electrodes (GCEs) and used to measure dopamine in aqueous solution. Within this series, p-doped SiNWs had the highest sensitivity in the series and are the focus of this study. Optimum measurements were obtained at pH 5.0. Cyclic voltammetry (CV) determination of dopamine showed that oxidation at +0.4801 V versus Ag/AgCl provided the highest sensitivity and also for chronoamperometric (CA) analysis. A calibration curve using chronoamperometry showed a linear (R2 = 0.9896) range from 50 to 900 µM. Randles-Sevçik analysis showed that the interaction of dopamine with the electrode surface was diffusion controlled reversibly with coefficients (D) equal to 2.77 × 10−5 and 2.01 × 10−5 cm2·s−1 for the oxidation and reduction potentials, respectively. The sensor was demonstrated to be selective in the presence of uric acid, acetaminophen, H2O2, folic acid, and glucose.

Transparent and Highly Flexible Hierarchically Structured Polydimethylsiloxane Surfaces Suppress Bacterial Attachment and Thrombosis Under Static and Dynamic Conditions.

The surface fouling of biomedical devices has been an ongoing issue in healthcare. Bacterial and blood adhesion in particular, severely impede the performance of such tools, leading to poor patient outcomes. Various structural and chemical modifications have been shown to reduce fouling, but all existing strategies lack the combination of physical, chemical, and economic traits necessary for widespread use. Herein, a lubricant infused, hierarchically micro- and nanostructured polydimethylsiloxane surface is presented. The surface is easy to produce and exhibits the high flexibility and optical transparency necessary for incorporation into various biomedical tools. Tests involving two clinically relevant, priority pathogens show up to a 98.5% reduction in the biofilm formation of methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa. With blood, the surface reduces staining by 95% and suppresses thrombin generation to background levels. Furthermore, the surface shows applicability within applications such as catheters, extracorporeal circuits, and microfluidic devices, through its effectiveness in dynamic conditions. The perfusion of bacterial media shows up to 96.5% reduction in bacterial adhesion. Similarly, a 95.8% reduction in fibrin networks is observed following whole blood perfusion. This substrate stands to hold high applicability within biomedical systems as a means to prevent fouling, thus improving performance.

Accessible, fast and easy fabrication of hydrophilic-in-hydrophobic microdroplet arrays

Microdroplet arrays (MDAs) are powerful tools for digital immunoassays, high-throughput screening and single cell analysis. However, MDAs are usually produced with cleanroom processes, which are associated with high costs and low availability. Furthermore, in order to obtain robust and stable MDAs based on hydrophilic spots surrounded by a hydrophobic background, the chemistry must be strictly controlled, which is challenging using shared equipment. Here, we developed a new method to fabricate MDA substrates independently from the cleanroom. A small and low-cost in-house built system to collimate the light source was assembled for photopatterning a negative resist, and spots with diameters down to 4 μm were obtained, with only 3% to 5% spot-to-spot variation across the same sample and high batch-to-batch reproducibility. The use of a negative photoresist enabled the formation of a hydrophobic coating in solution which yielded high-quality MDAs. The feasibility for carrying out digital assays was demonstrated by measuring anti-Tau antibody in sample buffers containing bovine serum albumin, with no noticeable surface fouling. The reported, robust, cost-effective, and fast process could hence lower the threshold to fabricate and use MDAs for digital immunoassays and other microcompartmentalization-based applications.

A NEW SPECIES OF THE AMPHIPOD <i>MELITA</i> LEACH, 1814 (CRUSTACEA: AMPHIPODA: MELITIDAE) FOR THE AZOV-BLACK SEA BASIN

Amphipods of the genus (Melitidae, Amphipoda) were found in the Kerch Strait (Black Sea) in September 2019 and March, July, November 2020. The material was collected in the formations formed by the polychaete (Fauvel, 1923). The depth ranged from 0.1 to 0.2 m. The individuals found in this site do not belong to the species (Montagu, 1804) known in the Black Sea, but they correspond to the morphological characters of the genus Melita . The species discovered is as close as possible to the species Melita setiflagella Yamato, 1988, whose natural range is located in the estuaries of rivers in Japan. Invasive range covers coastal waters of the Atlantic coast of Europe, the Pacific and Atlantic coasts of the United States and the Atlantic coast of Argentina. Presumably, this invader was accidentally introduced into the Black Sea with ballast waters or by transfer with fouling of ship surfaces. M. cf . setiflagella formed a stable self-reproducing population in the Kerch Strait. Therefore, it is important to monitor the distribution of this amphipod in order to predict the consequences for endemic species and local ecosystems.

Generalized Analysis of Dynamic Flow Fouling on Heat Transfer Surfaces

Several energy applications involve flow of untreated heat transfer fluids that contain trace amounts of mineral salts, such as calcium carbonate and calcium sulfate, which show reverse solubility with temperature. The gradual accretion of these salts onto the heat transfer surfaces causes fouling that degrades thermal performance over time. While fouling of bare surfaces has been extensively studied, fouling of nonwetting superhydrophobic or liquid-infused surfaces is less understood, especially under dynamic flow conditions. This study presents a systematic experimental analysis to elucidate dynamic flow fouling of calcium carbonate and calcium sulfate on smooth, superhydrophobic and liquid-infused surfaces in a generalized manner. Copper tubes with modified inner surface wettability are fabricated and subjected to forced convection at different flow rates and fouling salt concentrations. Fouling characteristics of the two salts on the different surfaces are examined through microstructural analysis, and quantified in terms of asymptotic fouling resistance that measures the total extent of fouling, and a threshold time, which correlates to the onset of significant fouling. Using Taguchi design of experiments, the study reports, for the first time, closed-form analytical relationships for the asymptotic fouling thermal resistance and threshold time on the Reynolds number, dimensionless concentration of fouling agent and dimensionless infused liquid viscosity that represents the different surface types in a unified manner. It is shown that the analytical model accurately predicts the fouling characteristics in up to about 97% of the data, based on which contour maps of optimum surface designs for minimizing fouling resistance are presented. The results provide information on designing surfaces for reduced fouling or for estimating the fouling characteristics for a given surface in applications.

Electrochemical, theoretical, and analytical investigation of the phenylurea herbicide fluometuron at a glassy carbon electrode

For the first time, both theoretical and electrochemical behavior of the phenylurea herbicide fluometuron (FTN) were investigated using the glassy carbon electrode (GCE). The cyclic voltammetry (CV) performed in the presence of FTN showed an irreversible profile for the analyte with one well-defined anodic peak at ca. +1.2 V (vs. Ag/AgCl). The linear dependence of pH and peak potential was evaluated using the Nernst equation through CV measurements. The slope of 46 mV s−1 suggests an oxidation mechanism involving an equal number of protons and electrons. High-level quantum-mechanical calculations based on the density functional theory showed that the presence of defects on the GCE surface induces strong interaction leading to FTN dissociation and/or its adsorption with orientation parallel to the substrate which compromises the electroanalysis. Raman spectroscopy confirmed the surface fouling. Differential pulse voltammetry (DPV) was used for the electroanalytical determination of FTN under optimized conditions. The oxidation peak increased with increasing concentrations of FTN in the range of 207–3846 µg L−1; the theoretical detection limit was estimated as 63 µg L−1. To avoid surface fouling, the calibration curve was applied for the determination of FTN. The unmodified electrode offered proper selectivity in the presence of other pesticides and potential interfering species. Intra and inter-day precision was established. Recoveries were obtained in the range of 81.8–98.9% (n = 3) with the absence of matrix effects. The results showed that electroanalysis through the bare GCE might be used as a novel strategy to determine the persistent organic compound FTN in spiked river water and simulated serum samples and preliminary evaluations such as screening purposes.