External Surface Research Articles

Investigation of the Affinity of Aptamers for Bacteria by Surface Plasmon Resonance Imaging Using Nanosomes.

The cell-SELEX method enables efficient selection of aptamers that bind whole bacterial cells. However, after selection, it is difficult to determine their binding affinities using common screening methods because of the large size of the bacteria. Here we propose a simple surface plasmon resonance imaging method (SPRi) for aptamer characterization using bacterial membrane vesicles, called nanosomes, instead of whole cells. Nanosomes were obtained from membrane fragments after mechanical cell disruption in order to preserve the external surface epitopes of the bacterium used for their production. The study was conducted on Bacillus cereus (B. cereus), a Gram-positive bacterium commonly found in soil, rice, vegetables, and dairy products. Four aptamers and one negative control were initially grafted onto a biochip. The binding of B. cereus cells and nanosomes to immobilized aptamers was then compared. The use of nanosomes instead of cells provided a 30-fold amplification of the SPRi signal, thus allowing the selection of aptamers with higher affinities. Aptamer SP15 was found to be the most sensitive and selective for B. cereus ATCC14579 nanosomes. It was then truncated into three new sequences (SP15M, SP15S1, and SP15S2) to reduce its size while preserving the binding site. Fitting the results of the SPRi signal for B. cereus nanosomes showed a similar trend for SP15 and SP15M, and a slightly higher apparent association rate constant kon for SP15S2, which is the truncation with a high probability of a G-quadruplex structure. These observations were confirmed on nanosomes from B. cereus ATCC14579 grown in milk and from the clinical strain B. cereus J066. The developed method was validated using fluorescence microscopy on whole B. cereus cells and the SP15M aptamer labeled with a rhodamine. This study showed that nanosomes can successfully mimic the bacterial membrane with great potential for facilitating the screening of specific ligands for bacteria.

Correction for geometric distortion in the flattened representation of pipeline external surface

Conventional cameras often produce external pipeline surface images with significant perspective-projection distortions, making determining the type and size of defects on the pipeline surface difficult. To address this issue, we present a novel approach for correcting the geometric distortion of a constant diameter pipeline (CDP) external surface image based on apparent contour pairs (ACPs). First, the camera is calibrated and the real projection position of ACPs accurately extracted. Second, a single-view perspective projection model of the CDP is adopted to realize a three-dimensional reconstruction of the pipeline. Subsequently, the flattened image of the CDP’s outer surface is obtained by performing equidistant sampling of cross sections, determining the visibility of discrete points, and mapping projection points onto a flat surface. Simulations and real experiments demonstrated the high accurate method in the correction of CDP images. Experiments conducted under different outdoor scenarios confirmed the robustness of the proposed method.

Comparison of Novel 3D-printed Stepped Porous Metal Cones and Metaphyseal Sleeves for Reconstruction of Severe Knee Bone Defects: Short-term Clinical Outcomes.

Both porous metal cones and metaphyseal sleeves are excellent implants for reconstructing severe bone defects in the knee joint, but they both exhibit design limitations. The porous metal cone, especially, has significant room for improvement in its shape design. The existing porous metal cones often feature a conical external surface with a relatively small taper, potentially compromising both rotational and axial stability. To improve both axial and rotational stability in porous metal cones, we developed a 3D-printed stepped porous metal cone. This study aimed to assess the short-term clinical outcome of the 3D-printed stepped porous metal cone and to compare it with the clinical outcome of patients who underwent revision total knee arthroplasty (rTKA) with the metaphyseal sleeves during the same period. Patients who underwent total knee arthroplasty revision with metaphyseal bone defect reconstruction from 2019 to 2021 were retrospectively analyzed. A total of 61 patients were enrolled in the study, including 15 patients using 3D-printed stepped porous metal cones and 46 patients using metaphyseal metal sleeves. Thirty patients using metaphyseal sleeves were screened by propensity score matching method and compared with those using stepped cones. Analysis included the American Knee Society Score, the Hospital for Special Surgery knee score, the Western Ontario and McMaster Universities Arthritis index, the Short Form 12 (SF-12) health survey, and radiographic assessment with a mean follow-up of 28.5 ± 8.3 months. To conduct comparative analyses, unpaired Student's t-tests were employed for continuous variables, while categorical variables were analyzed using the appropriate Fisher exact or chi-squared test. In this study, the survival rates of both the stepped cone and metaphyseal sleeve were 100%. There was no statistically significant difference in postoperative knee function scores between the two groups (p > 0.05). However, patients in the cone group had significantly higher mental component summary scores on the SF-12 scale (p < 0.05) and higher increases in mean postoperative physical component summary scores than patients in the sleeve group (p < 0.05). In addition, patients in the cone group experienced fewer intraoperative and postoperative complications compared to the sleeve group. The 3D-printed stepped porous metal cone can effectively reconstruct bone defects in complex rTKA and provide satisfactory early clinical and radiographic results. The 3D-printed stepped cone provides a more stable structure similar to the sleeve while maintaining the original benefits of the cone making it a promising choice for rTKA.

Thermally Powered Soft Gripper Covered with Silver Coated Nylon Fabric Heater Reinforced with Stainless Steel Yarn

Soft grippers, generating movement immediately, are generally based on flexible materials actuated by air pressure and comprised of bulky parts, including valves, compressors/pumps, motors, and tubes. In this work, a compact soft gripper with the ability to actuate with a low boiling point liquid (acetone) is presented. SolidWorks 2021 software and 3D printing technology are used to design and manufacture the gripper molds, respectively. The constitutive material of the soft gripper body is highly flexible Ecoflex. A silver‐coated nylon fabric (SCNF) heater reinforced with stainless steel yarn (SSY) covering the external surface of the gripper was designed and manufactured using Autocad 2021 and a laser cutting machine, respectively. The idea is inspired by floating the gripper in warm water to provide smooth heat over a large surface area. The available commercial software Abaqus2021 is used to simulate the mechanical deformation of the gripper, and its results are verified with experimental results. The parameter’s effect including the voltage and low boiling liquid volume on achievable force and actuating time are investigated. The relation between the electrical, thermal, and mechanical properties of the presented gripper is discussed in detail.This article is protected by copyright. All rights reserved.

The Complete Mitochondrial Genome of the Chemosymbiotic Lucinid Bivalve Pillucina pisidium (Dunker, 1860) Occurring in Seagrass Zostera marina Bed in a Lagoon in Jeju Island, Korea

Commonly found in tropic and subtropic seagrass beds, lucinid clams host sulfur-oxidizing bacteria within their gills. These symbionts are crucial in converting phytotoxic sulfide in the sediment into less harmful sulfate, thus enhancing the environment for seagrasses and associated biota. We recently uncovered small clams within a Zostera marina seagrass bed situated in a lagoon on Jeju Island, off the south coast of Korea. These bivalves, with shell lengths of up to 7 mm, exhibited distinct features, including thick and hypertrophied gills, inflated and ovoid shells with a shell height/shell length ratio of 0.99, and the absence of a sulcus on the external shell surface. These characteristics align closely with those of Pillucina pisidium, a lucinid clam species originally reported in Japan. Analysis of the cytochrome b gene partial sequences of the clams from Jeju Island revealed a 100% match with P. pisidium reported in Japan, confirming their identity. Moreover, we successfully assembled the complete mitochondrial genome of P. pisidium for the first time, revealing a circular genome spanning 21,059 bp. Additionally, we constructed a phylogenetic tree using 13 protein-coding genes (PCGs) extracted from the mitochondrial genome of P. pisidium. Notably, P. pisidium formed a distinct clade within the subclass Autobranchia alongside other lucinid clams in the phylogenetic tree. However, within the family Lucinidae, synteny analysis of the 13 PCGs revealed diverse gene arrangement patterns, indicating considerable divergence. This divergence underscores the need for an extensive examination of Lucinidae mitochondrial genomes to elucidate the phylogenetic ties more precisely within the family, highlighting P. pisidium’s distinct evolutionary path within the family Lucinidae.

Influence of the rehydration period on yield quality and harvest performance in Manzanilla de Sevilla super high-density olive orchards

AbstractSuper-high density olive orchards may increase profitability for table olive producers. However, water needs and fruit damage could limit their viability. Deficit irrigation scheduling would reduce the amount of water required, but rehydration before harvest is extremely important. The aim of this work was to compare a typical deficit farm management model with a regulated deficit irrigation one based on the plant water status. The experiment was carried out during three seasons in a three years-old (4 × 1.5 m) commercial table olive orchard. In both irrigation scheduling plots, seasonal amount of applied water was similar. Irrigation treatments were: common farm management (CFM), an almost constant rate of irrigation, and Regulated deficit (RDI) based on midday shaded water potential. Vegetative measurements suggested that RDI increased the external surface of the hedge, and this was related with greater yield in this treatment. Significant differences were found in of fruit size at harvest in some seasons, with larger fruits in RDI compared to CFM. However, fruit damage occurred during mechanical harvest in both irrigation managements, despite the higher skin firmness in RDI, and shows the need to carry out postharvest treatments to improve the quality of the final product. Accurate control of the tree water status would allow optimizing the amount of water available for table olive orchards.

Potential non-invasive detection of lesions in broiler femur heads: application of the DXA imaging system

Leg health is a significant economic and welfare concern for the poultry industry. Current methods of detection rely on visual assessment of the legs and gait scores and bone scoring during necropsy for full characterization. Additionally, the current scoring of femurs only examines the external surface of the femoral head. Through the use of the dual-energy X-ray absorptiometry (DXA) imaging system, we show the presence of a necrotic region in the femurs that would otherwise be considered healthy based on the current evaluation procedures. Importantly, these lesions were present in almost 60% (22 of 37) of femurs that scored normal for femoral head necrosis (FHN). Additionally, these femurs showed greater bone mineral content (BMC) relative to weight compared to their counterparts with no lucent lesions (6.95% ± 0.20% vs. 6.26% ± 0.25; p = 0.038). Identification of these lesions presents both a challenge and an opportunity. These subclinical lesions are likely to be missed in routine scoring procedures for FHN and can inadvertently impact the characterization of the disease and genetic selection programs. Furthermore, this imaging system can be used for in vivo, ex vivo, and embryonic (egg) studies and, therefore, constitutes a potential non-invasive method for early detection of bone lesions in chickens and other avian species.

Measuring the Transmembrane Registration of Lipid Domains in Droplet Interface Bilayers through Tensiometry.

Diverse collections of lipids self-assemble into domains within biological membranes, and these domains are typically organized in both the transverse and lateral directions of the membrane. The ability of the membrane to link these domains across the membrane's interior grants cells control over features on the external cellular surface. Numerous hypothesized factors drive the cross-membrane (or transverse) coupling of lipid domains. In this work we seek to isolate these transverse lipid-lipid influences in a simple model system using droplet interface bilayers (DIBs) to better understand the associated mechanics. DIBs enable symmetric and asymmetric combinations of domain-forming lipid mixtures within a model bilayer, and the evolving energetics of the membrane may be tracked using drop-shape analysis. We find that symmetric distributions of domain-forming lipids produce long-lasting, gradual shifts in the DIB membrane energetics that are not observed in asymmetric distributions of the lipids where the domain-forming lipids are only within one leaflet. The approach selected for this work provides experimental measurement of the mismatch penalty associated with antiregistered lipid domains as well as measurements of the influence of rafts on DIB behaviors with suggestions for their future use as a model platform.

Case report: Findings in ovaries development from an aborted equine fetus

An aborted female foal was submitted for necropsy. During the gross examination, the ovaries were pale, grayish, and enlarged (6 × 5 cm), with a well-developed vascular structure surrounding the external surface; the cut surface of the ovaries showed a brownish parenchyma with white follicular areas mainly localized in the peripheral region. The ovaries were fixed for histological investigations. The histological evaluation of the ovaries showed polygonal-shaped cells with abundant cytoplasm and round or oval nuclei, arranged in cords of single cells. The tissue architecture was characterized by the presence of lobular-like tissues with a central vein. The tissue mimicking hepatocytes was delimited by a mature fibrous tissue and was surrounded by the normal ovarian tissue characterized by germinal epithelium and primordial follicular structures. Based on the histological findings, a diagnosis of bilateral ovarian hamartoma was carried out initially. For a better characterization of the ovarian tissue, the expression of tissue-specific (liver and ovary) markers was investigated using immunohistochemistry. Following the immunohistochemical analysis, the hamartoma diagnosis was excluded. The ovaries exhibited unique characteristics different from those of adult horse ovaries as well as unique morphological features different from other mammalian species. This case report enhances our understanding of ovaries at a later stage of pregnancy and unveils unique characteristics of horse ovaries development, avoiding misdiagnosis with pathological findings, hamartomas, or neoplasia.

Sulfonated Azocalix[4]arene-Modified Metal-Organic Framework Nanosheets for Doxorubicin Removal from Serum.

Chemotherapy is one of the most commonly used methods for treating cancer, but its side effects severely limit its application and impair treatment effectiveness. Removing off-target chemotherapy drugs from the serum promptly through adsorption is the most direct approach to minimize their side effects. In this study, we synthesized a series of adsorption materials to remove the chemotherapy drug doxorubicin by modifying MOF nanosheets with sulfonated azocalix[4]arenes. The strong affinity of sulfonated azocalix[4]arenes for doxorubicin results in high adsorption strength (Langmuir adsorption constant = 2.45-5.73 L mg-1) and more complete removal of the drug. The extensive external surface area of the 2D nanosheets facilitates the exposure of a large number of accessible adsorption sites, which capture DOX molecules without internal diffusion, leading to a high adsorption rate (pseudo-second-order rate constant = 0.0058-0.0065 g mg-1 min-1). These adsorbents perform effectively in physiological environments and exhibit low cytotoxicity and good hemocompatibility. These features make them suitable for removing doxorubicin from serum during "drug capture" procedures. The optimal adsorbent can remove 91% of the clinical concentration of doxorubicin within 5 min.

The microbiome of the pregnant uterus in Holstein dairy heifers and cows assessed by bacterial culture and 16S ribosomal RNA gene sequencing

IntroductionThe possibility that there is a resident and stable commensal microbiome within the pregnant uterus has been supported and refuted by a series of recent studies. One element of most of the initial studies was that they were based primarily on 16S rRNA gene sequencing from bacteria. To account for this limitation, the current study performed both bacterial culture and 16S rRNA gene sequencing in a side-by-side manner (e.g., same tissues isolated from the same animal).MethodsThe uteruses of 10 mid-pregnant (156 ± 5 d of gestation) Holstein heifers and cows were collected following slaughter. The external surface of the reproductive tract (positive control for contamination during tissue collection) as well as tissues within the pregnant uterus (placentome, inter-cotyledonary placenta, inter-caruncular endometrium, amnionic fluid, allantoic fluid, fetal abomasum content, and fetal meconium) were sampled for bacterial culture and 16S rRNA gene sequencing.ResultsThere were 87 unique bacterial species cultured from the external surface of the pregnant reproductive tract (contamination control) and 12 bacterial species cultured from pregnancy tissues. Six out of 10 cattle (60%) exhibited bacterial growth in at least one location within the pregnant uterus. For the metataxonomic results (16S rRNA gene sequencing), a low targeted microbial biomass was identified. Analyses of the detected amplicon sequence variants (ASV) revealed that there were: (1) genera that were prevalent on both the external surface and within the pregnant uterus; (2) genera that were prevalent on the external surface but either not detected or had very low prevalence within the pregnant uterus; and (3) genera that were either not detected or had low prevalence on the external surface but found with relatively high prevalence within the pregnant uterus.ConclusionThere are a small number of viable bacteria in the pregnant uterus. The 16S rRNA gene sequencing detected a microbial community within the pregnant uterus but with a low biomass. These results are consistent with recent studies of the pregnant bovine uterus and leave open the question of whether there is adequate microbial mass to significantly affect the biology of the normal healthy bovine pregnancy.

Enhanced activity of Ru-based catalysts for ammonia decomposition through nitrogen doping of hierarchical porous carbon carriers

Activated carbon (AC) materials, renowned for their high specific surface area, excellent conductivity, and customizable functional groups, are widely employed as catalyst carriers. However, enhancing the activity of Ru-based catalysts supported on AC (Ru/AC) for ammonia decomposition remains a challenge. In this study, commercial AC was utilized as a substrate, with glucose and urea employed as modifiers. Specifically, the surface of the AC was modified via a hydrothermal pyrolysis method, resulting in the successful post-treatment in situ co-doping of nitrogen (AC-GN). Experimental results revealed that Ru/AC-GN exhibited a hydrogen production rate 46% higher than that of Ru/AC at 475 °C, indicating improved activity and stability. The characterization of AC-GN demonstrated that nitrogen doping primarily occurred on the external surface and macropores of the AC, increasing the nitrogen content in the carrier, particularly pyrrolic nitrogen content, while preserving the original structural and morphological integrity of the AC. The enhanced dispersion of Ru, combined with the improved electronic transmission capabilities and strengthened interactions between the metal and the modified carrier, were identified as pivotal factors contributing to the enhanced low-temperature efficacy of Ru/AC-GN. This paper presents a novel direction for the large-scale preparation of efficient catalysts for ammonia decomposition.

Preparation and in Vitro Evaluation of Solid-Lipid Nanoparticles (from Dika Wax) for Enhanced Delivery of Nevirapine in HIV/Aids Management

The preparation and assessment of solid lipid nanoparticles (SLNs) of nevirapine with improved oral delivery for better management of HIV/AIDS was the aim of this research. Eight batches of SLNs of nevirapine were produced from Dika wax and evaluated for particle charges and distribution of the sizes of particles using Zeta sizer, surface shape with Cryo-Transmission Electron Microspcope (Cryo-TEM), chemical interaction between drug and excipients with Fourier Transform Infrared Spectroscope (FTIR). Loading capacity, encapsulation efficiency and in vitro drug release properties were determined. Release profiles were compared with ƒ2 statistic, one-way ANOVA and students’t-test. From the results obtained, Cryo-TEM revealed that the SLNs were round to oval in shape with smooth external surface. Zeta sizer particle sizes and distribution analysis indicated quality results for Nevirapine SLN Batches 15 and 18. The zeta potential results were: -16.83 ± 0.404 mV for Batch 1, -44.30 ± 0.624 mV for Batch 15 and -40.03 ± 2.65 mV for Batch 18. Batches 15 and 18 SLNs had loading capacities of 6.71% and 9.82% respectively and encapsulation efficiencies of 49.35% and 70.19% respectively. In vitro dissolution showed 102% release for batch 18 and 87.5% release for Batch 15 with a dissolution efficiency of 65% for Batch 15 and 83% for Batch 18 SLNs. ƒ2 statistic, ANOVA and students’ t-test revealed Batch 15 SLNs are similar to Batch 18 SLN. In conclusion, Batches 15 and 18 SLNs have good properties for enhancing the delivery of nevirapine as extended release dosage forms for better management of HIV/AIDS.

The Unprecedented Biodegradable Polyzwitterion: A Removal-Free Patch for Accelerating Infected Diabetic Wound Healing.

Zwitterionic polymers have emerged as an important class of biomaterials to construct wound dressings and antifouling coatings over the past decade due to their excellent hydrophilicity. However, all the reported zwitterionic polymers are non-degradable because of non-cleavable carbon-carbon bonding backbones, and must be removed periodically after treatment to avoid hypoxia in the wound, thus leading to potential secondary injury. In this work, we fabricate a biodegradable polyzwitterion patch for the first time by ring-opening polymerization of carboxybetaine dithiolane (CBDS), which is self-crosslinked via inter-amide hydrogen bonds and zwitterionic dipole-dipole interactions on the side chains. The unprecedented polyCBDS (PCBDS) patch demonstrates enough ductility owing to the intermolecular physical interactions to fully cover irregular wounds, also showing excellent biodegradability and antifouling performance resulted from the existence of disulfide bonds and carboxybetaine groups. Besides, the PCBDS degradation-induced released CBDS owns potent antioxidant and antibacterial activities. This PCBDS patch is used as a diabetic wound dressing, inhibiting bacterial adhesion on the external surface, and its degradation products can exactly kill bacteria and scavenge reactive oxygen species at the wound site to regulate local microenvironment, including regulation of cytokine express and macrophage polarization, accelerating infected diabetic wound repair and also avoiding the potential secondary injury. This article is protected by copyright. All rights reserved.

Experimental study on water replenishment holes in offshore monopiles

Adequate replenishment of water within the monopile foundations of offshore wind turbines is essential to ensure the effective performance of cathodic protection measures applied inside the monopile to combat internal corrosion. This study presents experimental results for the process of replenishing water within a monopile with one opening below the still water level. The results are presented as (1) the relative wave height and set-down inside the monopile under various regular wave conditions and (2) head loss coefficient for the flow in and out of the water replenishment opening in the monopile. The study demonstrates a clear link between the ratio of the wave height of the internal and external surface elevations, the relative wave height, and the dimensions of the opening in the monopile as well as the wave period. Furthermore, a simple predictive model is proposed based on linear wave theory and static energy loss considerations. The orientation of the opening with respect to the wave direction has limited effect on the relative wave height, however it has a distinct effect on the mean surface level (MSL) inside the monopile. The lowest MSL occurred when the opening hole was positioned perpendicular (at a 90-degree angle) to the direction of wave propagation. Geometric considerations suggest that the flow in and out of the cylinder is slightly asymmetric and the results also show a small difference in the head loss coefficient for the flow in and out of the monopile, respectively. On average, however, the head loss coefficient was found to be ζ=2.0.

Selective aromatization of 1-hexene to BTX over core-shell structured Silicalite-1@ZSM-5 catalyst

The strong acidity on the external surface of ZSM-5 is a primary factor resulting in the low BTX selectivity and catalyst deactivation during the olefin aromatization. In this study, a membrane-restricted Silicalite-1@ZSM-5 core–shell structured catalytic catalyst was designed and constructed for 1-hexene aromatization using a hydrothermal coating method. TEM and NMR results confirmed the complete coverage of Silicalite-1 on the surface of ZSM-5, with a shell thickness of 50 nm. The further reaction of the TIPB (1,3,5-triisopropylbenzene) molecular probe reactions demonstrated the passivation of the acid sites on ZSM-5 external surface. The inert shell layer passivated the acid sites on the external surface, thereby suppressing the isomerization of PX and the side-chain alkylation reaction of light aromatics. Compared to ZSM-5, the Silicalite-1@ZSM-5 catalyst exhibited a 37.15 % increase in BTX selectivity, a 58.65 % increase in PX selectivity, significantly reduced coke deposition, and demonstrated better stability. This strategy of in-situ epitaxial growth of inert shell layers holds significant promise for enhancing the selectivity of shape-selective catalysts and extending catalyst lifetime.

Selective Covalent Basal Plane Modification as a Probe of Hydroxide Ion Conduction Pathways in Magnesium Aluminum Layered Double Hydroxides.

Understanding ionic conduction in layered double hydroxides (LDHs) is a crucial step towards utilizing them as solid, hydroxide ion-conducting electrolytes in energy conversion applications. We selectively modified the interlayer and external surfaces of MgAl LDHs with tris(hydroxymethyl)aminomethane (TRIS) ligands. By adjusting the concentration of the TRIS surface modifier, the LDH basal plane surfaces could be functionalized everywhere (internally and externally) or only externally. External modification resulted in loss of OH-conductivity compared to pristine LDHs, confirming that external platelet surfaces are the primary ion conduction pathway.

Two-heads brick masonry walls strengthened by basalt and glass chopped fiber mortar: Effect of bed joints and coating reinforcements

It is urgent finding strengthening systems for masonry structures located in seismic areas. This paper studies the effect of chopped fibers embedded in a cementitious mortar to be used as a strengthening system for two-heads brick masonry panels subjected to diagonal compressive forces. The strengthening system provides the use of two types of chopped fibers dispersed in the mortar matrix, i.e. a glass fiber reinforced mortar (GFRM) and a basalt fiber reinforced mortar (BFRM). The retrofitting composite material is disposed in three different ways: (i) the reinforced mortar is placed within the mortar joints of masonry panel; (ii) the reinforced mortar is disposed on both external surfaces of the masonry panel, but the mortar joints are in plain mortar; (iii) the reinforced mortar is placed both within the mortar joints and as a double reinforcing system on the external surfaces of each masonry panel. Experimental results show that in all the three cases the use of fiber reinforced mortar enhances both the shear strength and the post-peak capacity of the two-heads brick masonry panel. The most suitable behavior is related to panels reinforced with mortar both within the joints and as external reinforcing system. From the comparison between GFRM and BFRM it is shown that the best performance is related to basalt fibers mortar, that is also the most sustainable one. Authors always recommend the use of dispersed fibers within the mortar matrix, as it stands as effective strengthening system for new and existing masonry structures, above all when they are located in areas characterized by seismic hazard.

The effectiveness and feasibility of ball-milled powdered activated carbon (BPAC) for removal of organic pesticides in conventional drinking water treatment process

In the conventional drinking water treatment process (CDWTP), powdered activated carbon (PAC) is commonly used for removing organic pesticides, or other organic contaminants. However, the hydraulic retention time (HRT) in CDWTP is insufficient for fulfilling PAC adsorption equilibrium to realize its full capacity. This study examined the adsorption kinetics, adsorption thermal dynamics, and removal efficiency for six organic pesticides using the ball-milled PAC (BPAC) with varying particle sizes in CDWTP. Based on the experiments with the pesticides of atrazine, diazinon, dimethoate, fenitrothion, isoproturon and thiometon, the results indicated that as the particle size reduced from around 38 μm for the commercial PAC to 1 μm for the BPAC, the adsorption rates for hydrophobic pesticides increased up to twentyfold. Diffusional adsorption from the bulk solution to the external PAC surface is the most likely predominant mechanism. This could allow a sufficient pesticides’ adsorption within the limited HRT and to achieve a great depth removal of these toxic compounds. However, the addition of BPAC with a diameter of 1 μm was observed to significantly increase residual particles in treated water after the conventional treatment process. With a further systematic evaluation of both adsorption rate and particle penetration, a particle size of around 6 μm BPAC was considered a practical compromise between the adsorption rate and particle penetration for real application. Results from five surface waters of different water quality indicated that, compared to commercial PAC, application of 6 μm BPAC could achieve up to a 75% reduction in adsorbent dosage while maintaining around the same pesticide removal efficiencies. Additionally, thermodynamic analyses suggest that adsorption of these pesticides could be enthalpically or entropically driven depending on the degree of pesticide hydrophobicity.

Hydrophobicity of montmorillonite synergistically controlled by silanization and aliphatic amine modification

The hydrophobic modification of montmorillonite significantly extends its potential applications across various industrial sectors. In this study, montmorillonite with controlled hydrophobicity was prepared based on Cu2+-exchanged montmorillonite by synergistic modification with perfluorodecyltrimethoxysilane and aliphatic amines. Our findings indicate that copper ion-exchange process not only increases the interlayer spacing of montmorillonite but also promotes the formation of antlerite crystals on its surface. The presence of interlayer water impedes the silanization process with perfluorodecyltrimethoxysilane, confining the grafting to the external surface of the clay. Consequently, this method can only increase the water contact angle (WCA) from 0° to 54.4°. Conversely, treatment with aliphatic amines removes interlayer water and establishes a hydrophobic structure on the internal surface, raising the WCA to 47.0°. Remarkably, the synergistic modification of perfluorodecyltrimethoxysilane and aliphatic amine resulted in a WCA of 157.3°. Further investigations demonstrated that adjusting the type and concentration of the aliphatic amines allows for precise control of WCA, enabling adjustments within the range of 54.4° to 157.3°. This study offers a viable approach for the controllable hydrophobic modification of montmorillonite.