SEM EDS Research Articles

Mineralization of clofibric acid by persulfate-promoted catalytic subcritical water oxidation process using CoFe2O4@SiO2 catalyst

The design and use of innovative treatment processes are very important in preventing the possible toxic effects of organic pollutants in aquatic environments. One of these methods is the subcritical water oxidation method, which has been used recently. In the current study, the mineralization of clofibric acid (CFA) was carried out under more effective and mild conditions using persulfate (PS) as an oxidant and CoFe2O4@SiO2 catalyst by the subcritical water oxidation (sub-CWO) process. Characterization of the synthesized catalyst was performed through XRD, FTIR, TEM and SEM–EDS analyses. In the CFA oxidation with persulfate-promoted catalytic Sub-CWO process, optimum working conditions was determined as 15 mM PS, 40 min, 383 K, and 0.3 g L−1 catalyst dosage using the response surface method and Box–Behnken design. The catalyst's efficiency remained relatively stable after three cycles under optimal conditions, resulting in a 97% total organic carbon (TOC) removal. Decomposition products were determined and a degradation mechanism was proposed.

Influence of Mineralogical Characteristics on Mechanical Properties of Montney Tight Formations Using Instrumented Indentation Test and SEM–EDS Analysis

Influence of Mineralogical Characteristics on Mechanical Properties of Montney Tight Formations Using Instrumented Indentation Test and SEM–EDS Analysis

Production, Characterization and Mechanical Behaviors of Electrolytic Metal-Coated Light Polymeric Cylinders for Photogravure Press Applications

Since precision engraving is essential for almost any product or application, it is important that the printing system produces smooth and clear prints. In this regard, the rollers are made of steel and polymeric materials. However, light cylinder production is economical, transportation costs are very low, and it provides ease of transportation and distribution for printing houses. However, regional chain orientations and cracks occur in the polymeric material on the conical surfaces of the cylinders with shafts longer than 1 m. Therefore, it is necessary to improve the surface properties of polymeric cylinder. In this study, electrolytic hard chromium (Cr) and soft copper (Cu) metal layers, conductive (Ni and Ag) paint and polyester coating were successfully fabricated on polymeric lightweight cylinders via electroplating, spraying and hand brushing techniques for photogravure press application. At the fabrication stage on the steel base cylinders, polyurethane has been molded by using an injection molding machine. In order to eliminate the porosities, where polyurethane takes place, polyester has been coated on the polymeric cylinder and consequently polyester has been painted with conductive dye to obtain the conductivity. Then Cu and Cr have been coated by using the electroplating method and gravured. At the end of final stage, the process has been completed with coating of Cr on the Cu layer/conductive paint/polyester coating/polyurethane substrate. Phase analysis, microstructures and mechanical properties of the obtained samples have been examined through XRD, SEM–EDS, surface roughness, microhardness, tensile, three-point bending, scratch and wear machines. As a remarkable result of these studies, correlations were established between the quality of the layers and the mechanical properties as innovative scientific approaches, and between the layers produced on an experimental basis and the samples produced on a fabrication basis, they were produced and used in high-quality multilayered architecture to engraving technology and then to the society because of its effectiveness.

Investigation of the effect of metal powder and metal-supported MCM-41 catalysts on the pyrolysis of horse chestnut fruits and shells (Aesculus hippocastanum L.)

AbstractHorse chestnut fruit and horse chestnut shell are derived from the same biomass but exhibit distinct structural characteristics. Different compounds can be produced through the pyrolysis of these materials. The pyrolysis process was conducted on horse chestnut fruit and shell at temperatures of 300, 400, and 500 °C, both with and without various catalysts (Al, Fe, MCM-41/Al, MCM-41/Fe). The synthesis of MCM-41 catalysts utilized a hydrothermal method, and their properties were assessed through XRD, SEM–EDX, and SEM–EDS analyses. The resulting products from the pyrolysis were analyzed using GC–MS and elemental analysis techniques. Optimal efficiency was achieved at 400 °C, with the highest HHV value recorded at 34.38 MJ/kg when Al powder catalyst was present.

Experimental investigation on the high-temperature corrosion of 12Cr1MoVG boiler steel in waste-to-energy plants: Effects of superheater operating temperature and moisture

Waste-to-energy (WTE) technology via municipal solid waste incineration (MSWI) have developed very rapidly with the advantages of achievement on waste disposal and energy conversion. This technology is developing towards higher capacity and efficiency. Therefore, the operation parameters of WTE boilers must be improved. However, higher steam parameters means higher surface temperature of exchange tube in superheaters and reheaters in WTE boilers, resulting higher risk of engineering failure due to high-temperature corrosion. Additionally, the incineration of MSW releases flue gas with a high content of corrosive species and water vapor, which can cause severe high-temperature corrosion. This experimental investigation details the effect of surface temperature and water vapor concentration on the high-temperature corrosion behavior of 12Cr1MoVG boiler steel under an atmosphere mimicking MSWI. The corrosion test environment consists of high temperature, ash deposit and simulated flue gas of waste incineration according to a real WTE boiler. The experiment was conducted using a two-zone bench-scale tube furnace with a gas temperature of 600℃ and the sample temperatures of 380℃, 430℃, and 480℃. For the investigation of water vapor concentration effect, 18 % vol and 23 % vol were set up in this study. After 240 hours of exposure, the corrosion weight curves illustrated that the corrosion kinetics was highly dependent on the surface temperature of corrosion samples. Furthermore, an increase in water vapor concentration exacerbated the high-temperature corrosion. XRD analysis identified the corrosion products as metal chlorides and metal oxides. Cross-sectional SEM images and EDS analysis revealed that an increase in water vapor accelerated the corrosion rate of the steel samples due to chromium dilution behavior.

Grafting-from Synthesis of Plant-Polynorbornene Biohybrid Materials.

Plants, essential for food, oxygen, and economic stability, are under threat from human activities, biotic threats, and climate change, requiring rapid technological advancements for protection. Biohybrid systems, merging synthetic macromolecules with biological components, have provided improvement to biological systems in the past, namely, in the biomedical arena, motivating an opportunity to enhance plant well-being. Nevertheless, strategies for plant biohybrid systems remain limited. In this study, we present a method using grafting-from ring-opening metathesis polymerization (ROMP) under physiological conditions to integrate norbornene-derived polymers into live plants by spray coating. The approach involves creating biological macroinitiators on leaf surfaces, which enable subsequent polymerization of norbornene-derived monomers. Characterization techniques, including FTIR spectroscopy, SEM EDS imaging, ICP-MS, nanoindentation, and XPS, confirmed the presence and characterized the properties of the polymeric layers on leaves. The demonstrated modifiability and biocompatibility could offer the potential to maintain plant health in various applications, including the development of thermal barriers, biosensors, and crop protection layers.

Oxidation Behaviour of Fe-28Al-5Si at.% Alloyed with Ti and Mo

AbstractThe high-temperature oxidation behaviour of Fe-28Al-5Si, Fe-28Al-5Si-2Mo and Fe-28Al-5Si-2Ti (in at.%) was investigated. Cyclic oxidation tests of iron aluminides were performed at 900°C and 1100°C. The oxidation kinetics and oxidation behaviour (by measuring of total weight gain, etc.) were described. The structure of the alloys’ surfaces after oxidation, as well as the composition and morphology of oxide layers, was analysed by optical microscopy, scanning electron microscopy, SEM–EDS and X-ray diffraction. The beneficial effect of alloying with titanium or molybdenum on the oxidation resistance of Fe-Al-Si-based alloys was observed at temperatures of 900°C and 1100°C. Titanium and molybdenum suppress the formation of eutectic regions of the secondary phase in the structure, which preferentially oxidize. Therefore, a thin and compact alumina layer (only minor amounts of iron oxides and ZrO2) formed on the surface of Fe-28Al-5Si-2Mo and Fe-28Al-5Si-2Ti at 900°C. These alloys maintain low weight gains even at a temperature of 1100°C. On the other hand, alloy Fe-28Al-5Si contains a high number of eutectics-like areas, which causes ingress of the oxidation (selective oxidation of eutectic areas) and breakaway oxidation is observed at 900°C and 1100°C, respectively.

Investigation of tribological performance of hydrothermal carbon by pin-on-disc test and warm deep drawing process

In this study, the synthesis of hydrothermal carbon (HTC) lubricant and its usability as a lubricant under hot industrial conditions were investigated. In this context, the characterization of HTC produced from organic sources at low cost and in a short time was performed, and its tribological performance was analysed in detail. HTC produced by the hydrothermal carbonization method was characterized through SEM images and EDS analysis. To determine the effect of HTC on friction at different temperatures, HTC was subjected to a pin-on-disc wear test with AA5754 material. The effect of various lubricants, temperatures, blank holder pressure, and forming speed parameters on the forming force for the analysis of the tribological effect of HTC on deep drawing processes were statistically analysed. The performance of HTC was compared with Teflon, fullerenes, graphene, and carbon nanotube (CNT) materials. According to the results obtained from wear tests, the lowest friction coefficient value was achieved in the presence of fullerenes as the lubricant, and as the temperature increased, the friction coefficient decreased. It was observed that HTC exhibited lower performance in the wear test compared to fullerenes due to oxidation. When the effect of deep drawing parameters on the forming force was analysed, it was concluded that the most effective parameters were temperature (72.32%) and lubricant (20.89%). According to the S/N analysis results, the minimum forming force was obtained under the conditions of solid Teflon lubricant, 250 °C temperature, 15-bar blank holder pressure, and 2 mm/s forming speed. The tribological performance difference between HTC and Teflon is at the 1% level. The results demonstrate the potential industrial usability of HTC as a lubricant.

Green synthesis of silver chloride nanoparticles derived from Artemisia sieberi extract (AgClNPs-ASE) induces cell cycle arrest and triggers apoptosis in human breast (MDA-MB-231) cancer cells

In recent years, metallic nanoparticles have attracted tremendous attention in nanomedicine. Here, we report green synthesis and determination of silver chloride nanoparticles synthesized using Artemisia sieberi extract (AgClNPs-ASE) and its anticancer properties against human breast cancer cells. Numerous techniques, such as X-ray diffraction (XRD), UV-visible spectra, transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive spectra (SEM–EDS), and dynamic light scattering (DLS) analysis determined the morphology characteristics and size of the obtained nanoparticles. Cytotoxic properties of AgClNPs-ASE were carried out toward human breast cancer MDA-MB-231 cells and nontumorigenic HEK293 cells. AgClNPs-ASE revealed better efficacy toward breast cancer cells and was relatively less cytotoxic to nontumorigenic cells. Induction of apoptosis was further revealed by Hoechst 33258 dye and dual acridine orange and ethidium bromide (AO/EB) staining and in cells along with upregulation of caspase-8 and 9 proteins. AgClNPs-ASE could trigger the apoptosis by upregulation of early (1.93%) and late (58.86%) apoptosis followed by fluorescein isothiocyanate (FITC)‐Annexin‐V/PI staining and enhanced cell cycle population (sub-G1). AgClNPs-ASE significantly increased NO production in cancer cells. Moreover, qRT-PCR study showed that AgClNPs-ASE treated cells induce increased expression of the LncRNA GAS5 gene. These findings suggest the remarkable apoptosis in cancer cells triggered by AgClNPs-ASE in vitro.

Characterization and identification of an archaeological “lacquer” pipe

A pipe with red coating on the surface was excavated from an archaeological site in Sweden, which is supposed to be a lacquer ware imported from China due to the admiration and pursue of lacquer wares from Asia by Europeans during sixteenth to eighteenth centuries. However, materials such as shellac and resins were often used to imitate lacquer during that time in Europe. To determine whether the pipe was Chinese lacquer ware or not, attenuated total reflection of fourier transform infrared spectroscopy (ATR-FTIR), thermally-assisted hydrolysis and methylation pyrolysis gas chromatography-mass spectrometry (THM-Py-GC/MS) were conducted. The detection of significant amount of aleuritic acid, laccijalaric acid, laccishellolic acid, shellolic acid and jalaric acid represents that shellac is the main material used for the pipe coating rather than Chinese lacquer. Long chain fatty alcohols were found in the sample, indicating that the shellac is un-dewaxed. In addition, pine resin and turpentine were also found as additives in the pipe coating. Furthermore, pigments in the coating were determined as cinnabar and carbon black by scanning electron microscopy with element energy dispersive spectroscopy (SEM–EDS) and Raman spectroscopy. The results could definitely support the conservation of the pipe, and also provide the evidence of the cultural exchange between Europe and Asia.

New insights on the analysis of the causes of glossy lustre on the surface of ancient Chinese bronze mirrors

Ancient Chinese bronzes, particularly bronze mirrors, often develop a fatty, oily, or greasy film on their surface, known as patina. This film can appear silvery, green, or black. Bronze mirror samples from the Spring and Autumn Period (770–476/403 BCE) to the Ming Dynasty (1368–1644 CE) were analyzed using a systematic approach that included super depth of field three-dimensional microscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM–EDS), Raman spectroscopy, and THM-Py-GC/MS. The analysis indicates the presence of advanced organic acid lead in the matrix of ancient bronze mirrors. The ancient existence of the lost wax method combined with the mould method of bronze casting technology is verified through simulation experiments and ancient literature. Ancient bronze mirrors may have utilized this technique, with advanced organic acid lead remaining in the mirror mould that entered the bronze mirror matrix during pouring. The Lead organic acids in bronze mirrors readily precipitate on the surface and cover the mirror. The change in the greasy sheen on the surface of the bronze mirror may be related to the degree of corrosion. If the mirror's corrosion level is low, the organic acid lead film remains transparent. If the level of corrosion is significant, the organic acid lead film may darken in color due to oxidation, aging, hydrolysis, or microbial activity.

Nanoarchitectonics of catalytic tubular nanomotors based on Cu/Fe@SBA-15 for lung cancer treatment

Fabrications of nanomotors (NMs) are at the forefront of exploring the true potential of nanotechnology. Tubular nanomotors (TNMs) have been attracting huge interest recently. NMs based on 2D-hexagonal mesoporous silica (SBA-15) have been prepared through the surfactant-assisted sol–gel method. Copper and/or iron oxide nanoparticles have been impregnated in SBA-15 to form catalytic tubular nanomotors. Characterization has been investigated by XPS, XRD, HR-TEM, SEM–EDS, and BET. The electrochemical measurements were used to confirm the motion of the nanomotors. By increasing the loading of metal oxide nanoparticles, the motion decreases; this could be observed from the current loss. The anti-cancer potential of synthesized nanomotors against two cell lines (A549 and H460) of human lung carcinoma has been tested. Among all tested NMs, high-metal oxide-loaded materials containing CuO only as well as CuO and Fe2O3 are potent and significant in apoptotic cell death for lung cancer treatment.Graphical abstract

Exploring the provenance of a Byzantine excavated assemblage of textile and leather finds by the application of instrumental analysis

Stereomicroscopy, Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM–EDS), Fourier Transform Infrared spectroscopy with Attenuated Total Reflectance probe (FTIR-ATR), High Performance Liquid Chromatography with a Photodiode Array system (HPLC–PDA), X-ray Fluorescence spectroscopy (XRF), Zooarchaeology by Mass Spectrometry (ZooMS), and 14C dating were applied to an assemblage of textile and leather fragments that belong to the collection of the Byzantine & Christian Museum of Athens in Greece and lacked inventory information.The analyses applied, along with bibliographical research, yielded information on the materials, techniques and provenance of the find. The assemblage of finds consists of a gold thread embroidered silk satin, dyed with shellfish-purple; a gold strip-drawn wire embroidered silk tabby; a gold strip-drawn wire and red silk thread tapestry; a gold-thread embroidery on a tabby background; fragments of braided cord; and leather fragments. The material components could have been produced locally, in the area of the Byzantine Empire, though some of them indicate connections with India and/or China. The assemblage, dated between the mid AD 10th and mid eleventh century, was probably found in 1924 by Andreas Xygopoulos during the excavation of a tomb inside the church of Agia Sophia in Thessaloniki, Greece.

Modeling and experimental analysis of CO2 methanation reaction using Ni/CeO2 monolithic catalyst

In this study, the effect of the cell density of monolithic catalysts was investigated and further mathematically modeled on cordierite supports used in CO2 methanation. Commercial cordierite monoliths with 200, 400, and 500 cpsi cell densities were coated by immersion into an ethanolic suspension of Ni/CeO2 active phase. SEM–EDS analysis confirmed that, owing to the low porosity of cordierite (surface area < 1 m2 g−1), the Ni/CeO2 diffusion into the walls was limited, especially in the case of low and intermediate cell density monoliths; thus, active phase was predominantly loaded onto the channels’ external surface. Nevertheless, despite the larger exposed surface area in the monolith with high cell density, which would allow for better distribution and accessibility of Ni/CeO2, its higher macro-pore volume resulted in some introduction of the active phase into the walls. As a result, the catalytic evaluation showed that it was more influenced by increments in volumetric flow rates. The low cell density monolith displayed diffusional control at flow rates below 500 mL min−1. In contrast, intermediate and high cell density monoliths presented this behavior up to 300 mL min−1. These findings suggest that the interaction reactants-catalyst is considerably more affected by a forced non-uniform flow when increasing the injection rate. This condition reduced the transport of reactants and products within the catalyst channels and, in turn, increased the minimum temperature required for the reaction. Moreover, a slight diminution of selectivity to CH4 was observed and ascribed to the possible formation of hot spots that activate the reverse water–gas shift reaction. Finally, a mathematical model based on fundamental momentum and mass transfer equations coupled with the kinetics of CO2 methanation was successfully derived and solved to analyze the fluid dynamics of the monolithic support. The results showed a radial profile with maximum fluid velocity located at the center of the channel. A reactive zone close to the inlet was obtained, and maximum methane production (4.5 mol m−3) throughout the monolith was attained at 350 °C. Then, linear streamlines of the chemical species were developed along the channel.

Oxide Reduction Treatment with a Thermal Plasma Torch: A Case Study

This article presents the findings of a study on oxide reduction utilizing a novel reducing plasma torch, employing greenhouse gases such as CO2 and CH4 as plasma gases. The primary aim of this investigation is to establish the viability of this approach. The innovative plasma torch was employed to reduce various oxides, including aluminum oxide, iron oxide, and titanium oxide, as well as a mixed oxide composition, employing a CO2/CH4 molar ratio of 1:1 within a spouted bed reactor. Following plasma treatment, X-ray diffraction (XRD) analysis was conducted to examine the metallic phases, notably titanium, iron, and aluminum. SEM–EDS observations were carried out to assess microstructural changes and identify elemental compositions pre- and post-plasma treatment. The results demonstrate that within the conical section of the reactor, titanium oxide experiences partial reduction, resulting in limited titanium production, while aluminum oxide and iron oxides (magnetite and hematite) undergo reduction to yield aluminum and iron, respectively. Thermodynamic calculations, performed using Factsage software version 8.3, were utilized to predict stable-phase formations following plasma treatment for each material.

Hf-W dating of zircon in mesosiderite with high-pressure sintered standard

New standard zircons applicable to in situ analysis of Hf/W ratio by Nanoscale secondary ion mass spectrometer (NanoSIMS) were prepared and applied to Hf-W dating of a differentiated meteorite classified as mesosiderite. The standard zircons were synthesized by high-pressure experiment from starting materials which were mixture of hafnium oxide, tungsten oxide and high-purity zircon powder. The mixed powders were stirred and pulverized by a high-energy ball mill. They were then sintered at 1000 °C and 6 GPa using multi-anvil apparatus. Homogeneity of Hf/W ratios of synthesized zircons was examined by SEM–EDS, EPMA, and Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICPMS). Hf/W ratios of the same zircons were measured by a NanoSIMS with 2 nA oxygen primary beam and mass resolving power of 10,000. The relative sensitivity factor (RSF) of Hf/W ratio was determined by comparing zircon data measured by LA-ICPMS and NanoSIMS. Observed RSF (Hf/W) of zircon is 0.585 ± 0.180 (hereafter all error 2σ) consistent with 0.855 ± 0.468 of previous work within experimental error margin. The value is higher than observed RSF of glass matrix, 0.301 ± 0.062, and significantly higher than glass data of 0.21–0.22 in references. Based on the RSF, the Hf/W ratios of zircons extracted from mesosiderite “Asuka 882,023” were measured together with W isotopic compositions by NanoSIMS. Observed data in 180Hf/186W–182W/186W diagram are fitted by a straight line, yielding a slope (182Hf/180Hf) of 8.19 ± 3.50 × 10–6. This slope is converted into an absolute zircon Hf-W age of 4536.5+4.6–7.2 Ma using the age anchor of CV3 chondrite. This age agrees well with a reference value of 4532.0+11.4–20.8 Ma.

Biodiesel Production via Transesterification Reaction over Mono- and Bimetallic Copper-Noble Metal (Pt, Ru) Catalysts Supported on BEA Zeolite

This work focuses on the study of biodiesel production from commercial rapeseed oil and methanol via transesterification reactions on monometallic copper and bimetallic copper–noble metal (platinum, ruthenium) catalysts supported on BEA zeolite. The catalysts were prepared by wet impregnation method on the hydrogen form of BEA zeolite. As part of the study, the physicochemical and catalytic properties of the prepared catalytic materials were determined. The catalytic activity tests were carried out in the transesterification reaction over prepared catalysts at 220 °C for 2 h in an autoclave. The physicochemical properties of the obtained catalysts were investigated by X-ray diffraction (XRD), specific surface area and porosity (BET), a scanning electron microscope equipped with an energy dispersive spectrometer (SEM–EDS) and temperature-programmed desorption of ammonia (TPD-NH3) method. The results of the catalytic activity showed the promotional effect of the noble metal on the TG conversion and FAME efficiency of copper catalysts in the biodiesel production process. The most active catalyst turned out to be the calcined 5%Cu–1%Ru/BEA catalyst, which showed the highest TG conversion of 85.7% and the second highest FAME efficiency of 58.4%. The high activity of this system is explained by its surface acidity and large specific surface area.

Synthesis, Characterization, and Antibacterial Activity of Silver Nanoparticles Supported on Bovine Bone Powder Using Heterotheca inuloides: An In Vitro Study

This paper reports on the biosynthesis, characterization, as well as the bactericide and cytotoxic properties of silver nanoparticles supported on bovine bone powder (Ag-NPs/BBP). The silver nanoparticles were obtained through the bioreduction of AgNO3, using an infusion of Heterotheca inuloides leaves and flowers as a reducing agent and bovine bone powder as a support. The ratio of Ag-NPs/bovine bone powder was set as 1:10. The characterization was performed with SEM–EDS, XRD, UV–Vis, and TEM, which showed the formation of nanoparticles with an average size of 22.6 ± 10.8 nm and a quasi-spherical Ag-NPs morphology supported on the BBP surface. The nanocomposite exhibited a band gap of 2.19 eV. The minimal inhibitory concentration and the minimal bactericidal concentration against S. aureus, E. coli, and S. epidermidis were determined for each strain. In addition, the cytotoxic evaluation of the Ag-NPs/BBP on J774.2 mouse macrophage cells was performed. The Ag-NPs/BBP exhibited a bactericide effect on the strains studied, and the cytotoxicity had a dose-dependent behavior on the cells studied. Therefore, it was found that the ecofriendly synthesized Ag-NPs supported on bovine bone powder resulted in an effective bactericidal system against the strains studied, without significant cytotoxicity.

Characterization, surface preparation, conservation, and corrosion protection of bronze arrow heads from Cairo military museum using nanocomposite coating

The study focused on examining approximately 32 arrowheads from Cairo’s Qala Salah al-Din military museum, which showed significant signs of deterioration. The main objectives were to investigate the bronze alloy composition of these arrowheads and analyze the physical and chemical characteristics of their patinas. Understanding the causes and mechanisms of corrosion was crucial for developing effective conservation strategies to halt further degradation and identifying the corrosion products and metals involved. To achieve these goals, extensive examinations and analyses were conducted, including metallographic microscopy, SEM–EDS, and X-ray diffraction analysis to scrutinize the chemical composition, metallurgical features, and corrosion products of the bronze samples. Additionally, experimental studies were carried out to determine the most suitable protective coating for preventing future corrosion. Various combinations of ZnO nanoparticles with Paraloid® 48 or Paraloid® 66 coatings were tested on simulated arrowheads, and electrochemical techniques such as EIS and RP were employed for measurement. The results indicated that combining ZnO nanoparticles with either Paraloid® 48 or Paraloid® 66 coatings resulted in lower corrosion rates compared to using each coating alone. Based on these findings, chemical cleaning with ZnO nanoparticles and Paraloid® 48 was selected for treatment to protect the arrowheads' surfaces. Overall, this study provides valuable insights into preservation techniques for these historically significant artifacts.

In situ arsenic immobilization by natural iron (oxyhydr)oxide precipitates in As–contaminated groundwater irrigation canals

Arsenic-contaminated groundwater is widely used in agriculture. To meet the increasing demand for safe water in agriculture, an efficient and cost-effective method for As removal from groundwater is urgently needed. We hypothesized that Fe (oxyhydr)oxide (FeOOH) minerals precipitated in situ from indigenous Fe in groundwater may immobilize As, providing a solution for safely using As-contaminated groundwater in irrigation. To confirm this hypothesis and identify the controlling mechanisms, we comprehensively evaluated the transport, speciation changes, and immobilization of As and Fe in agricultural canals irrigated using As-contaminated groundwater. The efficiently removed As and Fe in the canals accumulated in shallow sediment rather than subsurface sediment. Linear combination fitting (LCF) analysis of X–ray absorption near edge spectroscopy (XANES) indicated that As(V) was the dominant As species, followed by As(III), and there was no FeAsO4 precipitate. Sequential extraction revealed higher contents of amorphous FeOOH and associated As in shallower sediment than in the subsurface layer. Stoichiometric molar ratio calculations, SEM‒EDS, FTIR, and fluorescence spectroscopy collectively demonstrated that the microbial reductive dissolution of amorphous FeOOH proceeded via reactive dissolved organic matter (DOM) consumption in subsurface anoxic porewater environment facilitating high labile As, whereas in surface sediment, the in situ-generated amorphous FeOOH was stable and strongly inhibited As release via adsorption. In summary, groundwater Fe2+ can efficiently precipitate in benthic surface sediment as abundant amorphous FeOOH, which immobilizes most of the dissolved As, protecting agricultural soil from contamination. This field research supports the critical roles of the phase and reactivity of in situ-generated FeOOH in As immobilization and provides new insight into the sustainable use of contaminated water.