Sepiolite Surface Research Articles

Facilitating interface tuning of metal-support interaction on the sepiolite surface for the enhancement of metronidazole removal

To achieve efficient catalytic activity for emerging contaminants degradation in water environment, this work creatively prepared a silicon-based catalyst (Co/ASepx), which built a metal-silicon framework in-situ growing on sepiolite (Sep) through hydrothermal synthesis, and further obtained via high-temperature pyrolysis. Then the Co/ASepx was used to activate peroxymonosulfate (PMS) to remove metronidazole (MNZ) from water environment. The results showed that the Co/ASepx presented a substantial number of Co/MgSiO3-Co interfacial structures, the introducing of interface engineering triggered the strong metal-support interaction between Co and Sep, then altered the surface electron distribution and regulated the coordination environment of the metal Co. The Co/ASep1-PMS system not only exhibited the significant MNZ removal performance, and the MNZ degradation rate in the Co/ASep1-PMS system was 5.4 times than that of the Co2+-PMS homogeneous catalytic system with the same Co dosage, but also presented low Co leaching and high cycling stability. Moreover, the quadruple mechanism of MNZ degradation were comprehensively revealed, in which was dominated by the singlet oxygen of the non-radical pathway. Lastly, this work provides a novel feasible way to build high-performance catalysts with low Co leaching and low cost for the outstanding removal efficiency of MNZ.

Facile hydrothermal synthesis of a multifunctional copper zinc tin sulfide (CZTS) nanoparticle-coated sepiolite fiber composite: structural characterization and photocatalytic properties

This work presents a facile hydrothermal synthesis method for fabricating a multifunctional composite of copper zinc tin sulfide (CZTS) nanoparticles coated onto sepiolite fibers. Morphological analysis confirms the firm attachment of approximately 10 nm CZTS nanoparticles onto the sepiolite surface. Elemental analysis verifies the presence of constituent elements from both CZTS and sepiolite, with a slight deficiency in Cu and an abundance of Zn observed. The compositional formula of CZTS in the composite is estimated as Cu1.93Zn1.05Sn0.98S4.04. Notably, the material exhibits a narrow band gap of 1.5 eV, enabling effective utilization of the entire visible light spectrum, making it promising for photocatalytic applications. BET nitrogen adsorption/desorption measurements reveal a substantial surface area of approximately 85.720 m2 /g, confirming the composite’s versatility and applicability, particularly in photocatalysis and adsorption processes. Additionally, X-ray diffraction analysis indicates reflections consistent with the crystal structures of kasterite CZTS and sepiolite, further confirming the composite’s composition. The multifunctional CZTS/Sepiolite composite demonstrates exceptional potential for simultaneous photocatalytic degradation and adsorption of organic pollutants, presenting a promising avenue for sustainable water treatment applications.

Facile synthesis of nano CeO2/sepiolite composite as visible-light-driven photocatalyst for rapid tetracycline removal

A novel CeO2/sepiolite (CeO2/SEP) composite with sepiolite as the support of CeO2 was successfully prepared using a simple ammonia precipitation method for the photocatalytic degradation of tetracycline (TC) by loading CeO2 nanoparticles on sepiolite. The analytical results showed that CeO2/SEP had good crystallization, and CeO2 nanoparticles were deposited on the surface of fibrous sepiolite. The composite photocatalyst with 50 % CeO2 loading presented the highest tetracycline degradation efficiency (92.7 %), and the reaction rate constant was 4.88 times greater than that of pure CeO2. In addition, quenching experiments showed that the main reactive active species included photogenerated holes (h+) and superoxide radical anions(O2·-).Furthermore, the enhanced photodegradation mechanisms and the possible degradation pathways of TC were also systematically discussed. The investigating results show that the enhanced photocatalytic performance was mainly due to the uniform attachment of CeO2 with smaller particle size on the surface of sepiolite, which increased the specific surface area of the photocatalyst and promoted the redox cycle of Ce3+/Ce4+ to generate more reactive free radicals. It can be concluded that this study offers a new potential option for efficient photodegradation of antibiotics in wastewater based on the visible-light-driven mineral based photocatalyst.

A mechanically durable slippery liquid-infused porous surface based on distinctive ‘jaboticaba-like’ TiO2/sepiolite nanocomposites with superior hot water repellency and anti-corrosion for protecting various substrates

Slippery liquid infused porous surfaces (SLIPS) are widely utilized due to their omniphobicity and distinctive slippery properties. Fragile mechanical properties and unstable lubricant layer of SLIPS have a substantial impact on its long-term application performance. Herein, a pre-oil-infused mechanically robust organic/inorganic composite superhydrophobic surface (SC) for SLIPS with hierarchical roughness was obtained by in-situ growing a significant amount TiO2 nanospheres on the surface of sepiolite (SEP) fiber structures via hydrogen bonding, Ti-O-Si covalent bonding, and electrostatic power, resulting in a unique bionic “jaboticaba-like” structure on SC. Through hydrogen bonding, the hydroxyl groups on the TiO2 surface can also interact with the cross-linked polymer PVDF-HFP (polyethylene fluoride hexafluoropropylene). In the presence of multiple interactions, SC could resist 300 cycles of a rigorous Taber rubbing test with a 500 g weight and yet retain superhydrophobicity. The prepared SLIPS have exceptional hot water (boiling water) resistance, strong shear stability (8000 rpm/min), and water jetting resistance (40 kPa). Corrosion current density of SLIPS and SC was decreased by roughly 4 orders of magnitude and 3 orders of magnitude, respectively, after exposure to 3.5 wt% NaCl solution as compared to bare aluminum substrate. SLIPS have higher long-term corrosion resistance compared to SC. Owing to the “jaboticaba-like” hierarchical structure, SLIPS have great oil-locking capabilities, as well as good mechanical stability and long-term corrosion resistance. This article offers recommendations for developing tough SLIPS for future engineering applications.

Magnetic sepiolite/iron(III) oxide composite for the adsorption of lead(II) ions from aqueous solutions

AbstractClay minerals are effective adsorbents used for the remediation of toxic heavy metals from wastewater due to their large surface areas and great cation-exchange capacities. In this study, the removal of lead ions from aqueous solutions via adsorption was investigated using raw and iron-modified Turkish sepiolite. The aim of this study was to examine the effects of modification and environmental conditions on the sorptive properties of sepiolite samples. Initially, the raw sepiolite (Sep) and magnetic sepiolite/Fe2O3 composite (MagSep) prepared using the co-precipitation method were characterized via mineralogical and petrographical means and the physicochemical properties were determined. Then, the batch adsorption of lead (Pb2+) ions on the sepiolite samples was examined under various conditions (solution pH, adsorbent dosage, contact time, initial Pb2+ ion concentration, temperature, shaking rate). The adsorption capacity of MagSep was found to be greater than that of Sep under all experimental conditions. The results showed that the adsorption process followed a pseudo-second-order kinetic model, and the Langmuir isotherm best correlated with the experimental data. The maximum adsorption capacities were found to be 60.6 and 90.1 mg g–1 for Sep and MagSep, respectively. The characterization of the Pb-adsorbed sepiolite samples showed that lead formed covalent bonds with the sepiolite samples and attached to the sepiolite surface mainly through ion exchange. MagSep can be used efficiently in the field of wastewater treatment for the removal of Pb2+ ions as it does not release any toxic pollutants and can be separated easily with the use of a magnetic field.

Desorption behaviour of polymers on sepiolite surfaces under high-temperature and high-salinity conditions

AbstractPolymers maintain colloidal stability by adsorbing onto the surface of sepiolite particles, and changes in temperature and salinity can affect this process. We chose three typical polymers to investigate their interactions with sepiolite under high-salinity (15 wt.% NaCl) conditions at >180°C. Sepiolite samples were characterized using infrared testing, X-ray diffraction testing, contact angle testing, thermogravimetric testing, filtration loss testing and rheological testing. The experimental results showed that the desorption of the polymers under high-temperature and high-salinity conditions reduces the stability and filtration control of the suspension significantly. Adding polymers to sepiolite suspensions can maintain good stability even after thermal ageing at 240°C. In terms of drilling fluid regulation, sepiolite can play a role in regulating rheological properties, and the interactions between various polymers and sepiolite can be utilized to maintain the stable colloidal state of the drilling fluid. Studying the adsorption behaviour of various types of polymers on the surface of sepiolite under high-temperature and high-salinity conditions has important implications for the design and selection of sepiolite drilling fluid treatment agents.

Temperature controlled adsorption of polyethyleneimine on the sepiolite surface

The effects of temperature (15, 25 and 35 °C) on the adsorption properties of polyethyleneimine (PEI) on the sepiolite (Sep) surface and some properties of the Sep/PEI suspensions including their stability were studied. It was shown that the increase in temperature caused larger adsorption of PEI macromolecules on the Sep surface, which was the effect of the spacious PEI conformation at higher temperatures. Stability of the Sep/PEI suspension was also better when temperature was higher due to effective electrosteric stabilization. The obtained results indicate how the temperature influences the textural and electrokinetic properties of the Sep/PEI systems. The following analytical methods: UV–Vis spectrophotometry, XRD, nitrogen adsorption-desorption method, elemental analysis, SEM-EDX, FT-IR, TG-DSC, viscometry and zeta potential measurements were used in the performed research. The presented findings can be successfully used to create hybrid materials dedicated to water and wastewater treatment as well as in the gas capture processes.

Co3O4 anchored on sepiolite surface grooves for superior adsorption of tetracycline from wastewater

Due to the low valence band maximum value, Co3O4 is an outstanding catalyst, but its utilization in adsorption needs to be addressed. In this study, we proposed a novel method for loading aggregation-prone Co3O4 onto sepiolite (Sep) to facilitate tetracycline (TC) adsorption. The XRD, TEM, and FTIR analyses demonstrated that the highly dispersed Co3O4 was successfully anchored on the sepiolite grooves via the Si-OH on the sepiolite surface’s grooves to the cobalt site in Co3O4. We firstly proposed a view of how metal oxide aggregates are confined to the grooves on the surface of sepiolite (via Si-OH at the edges of the grooves on the sepiolite surface). The ultra-high sorption capacity of Co3O4-Sep is 219.53 mg/g for TC, which is three times that of Sep (70.75 mg/g) and Co3O4 (85.29 mg/g). The kinetic and isotherm results fitting suggested that the adsorption of TC on Co3O4-Sep mainly contributed to the multilayer chemisorption adsorption process. Thermodynamic investigations revealed the spontaneous endothermic reaction of TC adsorption on Co3O4-Sep. Co3O4 strengthened the complexation between the composite and functional groups of TC, significantly increasing TC adsorption capacity. In addition, the Co3O4-Sep retained an extraordinary adsorption capacity with the presence of competing ions, at strongly acidic and alkaline pH values and after three cycles. Therefore, this study offers new perspectives on applying cobalt-based materials and demonstrates the potential for antibiotic adsorption in the prepared composites.

Enhanced PMS activation by MOF-derived Co3O4/sepiolite composite for norfloxacin degradation: Performance, mechanism and degradation pathway

In this study, cobalt metal-organic framework (Co-MOF) derived Co3O4/sepiolite hybrid catalyst was prepared by a facile wet chemical method followed by the calcination crystallization process. In Co3O4/sepiolite composite, Co3O4 nanoparticles with smaller grain size were well dispersed on sepiolite surface. The larger reaction rate constant was obtained in Co3O4/sepiolite/PMS system for norfloxacin (NFX) degradation (0.2588 min−1), which was almost 3.44 times that in Co3O4/PMS. The greatly enhanced NFX degradation performance was mainly ascribed to the combination of Co-MOF precursor and sepiolite support resulting in higher adsorption capacity, more exposed reaction active sites and overspreading surface hydroxyl groups. The electron paramagnetic resonance (EPR) and quenching experimental results indicated that the radical and non-radical pathway were responsible for the NFX degradation, and the SO4•- and 1O2 were the major contributors. Moreover, the continuous redox cycle of Co(III)/Co(II) and the surface -OH on catalyst played the important roles in the continuous production of the reaction active species thereby achieving the efficient degradation for NFX. In addition, the enhanced catalytic mechanisms and NFX degradation pathways were proposed. Overall, our study provides new insights for designing and developing efficient and environmentally friendly catalysts for practical wastewater treatment via activating PMS.

In-situ synthesis of sepiolite-supported ceria nanocrystal composites for efficient removal of aflatoxin B1: Enhanced degradation of mycotoxins in the environment by sepiolite nanofibers

Aflatoxin B1 (AFB1) is one of the most toxic mycotoxins, which has a serious effect on animals and human health and causes secondary pollution in the environment. Herein, the in-situ synthesis of ceria nanocrystals on sepiolite nanofibers successfully improved photocatalytic efficiency for the removal of AFB1 in aqueous solution under visible light. The optimum removal efficiency of the CeO2/sepiolite (Ce/Sep) composites was up to 93.3% within 3 h and was nearly 2.7 times higher than that of nano ceria. After a series of characterization, it was indicated that the significantly enhanced removal performance of Ce/Sep composites can be attributed to the large specific surface of sepiolite, leading to the homogeneous distribution of ceria and reducing their particle sizes to 5–20 nm, which increased the reaction active sites. Besides, sepiolite as an electron acceptor also inhibited the photogenerated electron-hole pairs recombine, while the interface effect and function group reaction between sepiolite and ceria extended absorption in the visible light region and effectively improved the separation efficiency of photogenerated electron-hole pairs, which produced more reactive oxygen species to destroy the structure of AFB1. This work demonstrates that the Ce/Sep composites possess excellent photocatalytic activity and have great application prospects in the treatment of AFB1 environmental pollution.

Z-Scheme g-C3N4/Fe3O4/Ag3PO4 @Sep magnetic nanocomposites as heterojunction photocatalysts for green malachite degradation and dynamic molecular studies

In this study, we successfully prepared a Z-scheme heterostructures’ nanocomposite using a co-precipitation method. The nanocomposite was characterized using several techniques, and the results showed that the surface of sepiolite was occupied by Fe3O4, Ag3PO4, and g-C3N4 nanoparticles. The photocatalytic performance of the g-C3N4/Fe3O4/Ag3PO4 @Sep nanocomposite was found to be significantly better than that of pure g-C3N4, g-C3N4 @Sep, and g-C3N4/Ag3PO4 @Sep. The enhancement in photocatalytic activity was attributed to the synergistic effects of the Z-scheme heterojunction construction, which improved light usage and charge carrier migration rate. The nanocomposite also exhibited good stability and reusability even after four cycles, as it was confirmed by MD calculations. Additionally, the DFT-D correction was used to optimize all the structures, and the MG adsorption was investigated using the adsorption locator module, suggesting the thermodynamic stability of the system. Overall, this study provides important insights into the design and synthesis of Z-scheme nanocomposite heterojunctions for efficient photocatalytic applications.

Enhanced photocatalytic degradation of indoor formaldehyde by sepiolite decorated with TiO2 nanoparticles: Effects of key preparation parameters

In this study, natural sepiolite was employed as the support of TiO2 for improving the photocatalytic degradation activity for indoor formaldehyde (HCHO) under solar light. The various TiO2/sepiolite composites were prepared to investigate the effect of TiO2 loading amount and crystallization temperature on HCHO degradation performance. The composite with TiO2 loading amount of 50% and 500 °C exhibited the optimal performance, whose mineralization rate was up to around 2.63 times higher than that of pure TiO2. The performance enhancement mainly resulted from the uniform deposition of TiO2 with smaller grain size on sepiolite surface, leading to more exposed active sites, higher quantum efficiency and faster carrier separation efficiency. As a result, more active radicals were generated in composite thereby boosting the HCHO degradation performance. Overall, our study improve the understanding on the photocatalytic oxidation of HCHO by mineral-based photocatalyst, thereby promoting the practical application in indoor air purification.

Hydrophobic modification of sepiolite by fatty acids for efficient oil removal: Influence of the alkyl chain length

Oil pollution has seriously affected the ecological balance, and the development of an efficient and low-cost sorbent material to treat oil pollution is work with practical applications. In this work, a novel hydrophobic sorbent based on natural sepiolite was obtained by modifying with four saturated fatty acids with different carbon chain length and used for oil removal from water. The original and modified samples were tested for SEM, XRD, FTIR, CA, XPS and BET analysis. The results showed that the functional groups of the modifier were successfully grafted onto the sepiolite surface. The sepiolite fibers changed from the original agglomerative morphology to more dispersed with a coarser surface. The contact angle of modified sepiolite was improved greatly compared with the original sepiolite. Among them, octadecanoic acid modified sepiolite (O-SEP), with a lower water contact angle showed the best diesel removal efficiency, indicating that there was no significant positive correlation between the oil sorption efficiency and the value of the contact angle. This study presented a simple and feasible method to produce hydrophobic-based sorbents with good performance based on clay minerals that could be used for oil spill cleaning up.

Robust cellulose fiber/fibrous sepiolite coated RuO2-CoP aerogel as monolithic catalyst for hydrogen generation via NaBH4 hydrolysis

Commercial carriers have been used to prepare monolithic NaBH4 hydrolytic catalysts, but the fixed structure and material limit the application scope and design freedom. Herein, the RuO2-CoP catalyst is coated on the surface of fibrous sepiolite (RuO2-CoP@aSep) by in-situ deposition, annealing in air and phosphating, which is constructed into the aerogel with cellulose nanofiber (CNF) and polyvinyl alcohol (PVA) by freeze drying process. The hydrogen generation rate (HGR) of RuO2-CoP@aSep increases from 3655 to 10713mLmin-1gcatalyst-1 by adjusting the mass ratio of cobalt to ruthenium in RuO2-CoP. Moreover, the optimized composite aerogel can get HGR (5268mLmin-1gcatalyst-1) by regulating its formulation, and the catalytic activity and mass loss rate of the aerogel maintains 76.6 and 0.92 % after five cycles of testing. The synergistic interaction between Ru and Co species, micro-nano porous structure, and structural coupling provide good catalytic activity and cycling performance, and show great potential in the design of controllable NaBH4 hydrolyzed monolithic catalysts.

Theoretical studies on the degradation mechanism of organochlorine pesticides in the presence of Si-OH in sepiolite

Nanofibers of sepiolite, a natural silicate belonging to the clay mineral family, are widely used in degrading toxic organic pollutants, air purification, and water pollutant adsorption. The role of Si-OH application in the degradation of organic pollutants, however, remains unclear. We performed density functional theory (DFT) calculations on organochlorine pesticides to gain insight into their degradation mechanism on the sepiolite surface. The results showed that organochlorine pesticides were preferentially adsorbed on Si and Si-OH sites. Meanwhile, the CCl bond could be effectively activated on the Si metal center. The search for the transition state showed that the reaction energy barrier of organochlorine pesticides at the Si-OH site was significantly lower than that at the Si site. In other words, the presence of hydroxyl effectively reduced the activation energy barrier, indicating that Si-OH was the main active site. This had a synergistic effect: the interaction between Si and the surface hydroxyl led to the degradation of organochlorine pesticides. We proposed a possible reaction mechanism that included adsorption, the forming and breaking of chemical bonds, and desorption.

Investigation of support effects during ethanol steam reforming over a Ni/sepiolite catalyst

Bifunctional mechanism proposed for the steam reforming of ethanol over Ni supported on natural sepiolite. The availability of silanols determines the activation of reactants on sepiolite's surface and their migration to the metal–support interface.

Ag/Ag3PO4 nanoparticles assembled on sepiolite nanofibers: Enhanced visible-light-driven photocatalysis and the important role of Ag decoration

A novel visible-light-driven Ag/Ag3PO4/sepiolite ternary heterostructure photocatalysts were successfully prepared via a facile precipitation method. The presence of Si–OH on the surface of sepiolite converted the part of Ag + to Ag0 through the in-situ reduction. the visible light degradation rate constant of Rhodamine B by Ag/Ag3PO4/sepiolite was about 3.68 times higher than that of bare Ag3PO4. The superior photocatalytic performance of Ag/Ag3PO4/sepiolite was attributed to the formation of Ag3PO4 particles with smaller grain size and Ag0 nanoparticles due to the introduction of sepiolite, resulting in the enhanced adsorption capacity, improved light response ability and accelerated photogenerated electron transfer rate. In particular, the generated Ag0 played a very important role in improving the electron-hole separation efficiency through acting as the electron acceptor and regulating the carriers’ separation path. On the other hand, the SPR effect of Ag0 can improve the light absorption ability of the photocatalys. The radical trapping experiment showed that holes (h+) and superoxide radical (•O2−) were the main reactive species, where the formation of •O2− was closely related to the presence of Ag0. This work provides new insights for the application of hybrid photocatalysts combined with mineral materials in wastewater treatment.

A simple fabrication of mineral supported Ni-NiAl2O4 nanocomposites with a novel transition layer

In recent years, Ni-based catalysts have attracted widespread attention in many fields due to their low price and high catalytic activity. However, the low dispersion of active components has significantly restricted their large-scale application. In this work, we prepared a new type of sepiolite nanofibers loaded Ni-NiAl 2 O 4 composite by coupling the sol-gel and reduction methods, using nickel nitrate, aluminum nitrate and sepiolite nanofibers as the raw materials. To determine the optimal conditions for preparing the composite material, the effects of complexing agent, additives, sepiolite addition content, calcination temperature and time, and reduction temperature and time on the microstructure of the composite were systematically studied. With comprehensive characterizations, the optimal preparation conditions of the composite were determined. In the optimal composite, the NiAl 2 O 4 nanoparticles with a particle size of ~25 nm were uniformly dispersed on the sepiolite surface, and nickel nanoparticles with a size of 5 nm and well dispersion were rooting in the NiAl 2 O 4 particles. The NiAl 2 O 4 in the composite was acted as the nickel source and transition layer for the growth and dispersion of nickel particles, respectively. This work is expected to provide an effective strategy for the low-cost preparation of Ni-based catalysts, in which the novel transition layer can provide stable nickel particles with good dispersion. • A novel mineral supported nickel-based catalyst was prepared via a sol-gel reduction method. • Comprehensive characterizations were performed on the prepared materials. • The dispersion of NiAl 2 O 4 nanoparticles can be improved by sepiolite. • The NiAl 2 O 4 as a transition layer can provide nickel source for the subsequent reduction process.

Development of a TiO2/Sepiolite Photocatalyst for the Degradation of a Persistent Organic Pollutant in Aqueous Solution.

A clay-based TiO2 nanocomposite material was synthesized by a facile method, to investigate its structure and photocatalytic efficiency. The supported TiO2 nanoparticles were generated using a sol-gel method, and subsequently, mixed with a suspension of sepiolite. The material was recovered in powder form (Mc-80) and then calcined to properly arrange the crystal lattice of the TiO2 particles for use in heterogeneous photocatalysis (Mc-80-500). A powder X-ray diffractogram of Mc-80-500 revealed a dispersion of anatase and rutile phase TiO2 particles on the clay surface, exhibiting a size in the order of 4–8 nm. TEM images of Mc-80-500 confirmed the presence of isolated TiO2 beads on the surface of the fibrous sepiolite. The specific surface area of Mc-80-500 was larger than that of raw sepiolite and that of free TiO2 nanoparticles. Mc-80-500 was found to be more efficient in heterogeneous photocatalysis compared to other TiO2 materials based on sepiolite. Total depollution of a reactive dye (Orange G) was achieved after 1 h irradiation time, which is relatively quick compared to previous reports. The photocatalyst material can be washed with distilled water without chemical additives or calcination, and can be reused several times for photocatalysis, without loss of efficiency.

An experimental and theoretical investigation of cationic azine dye adsorption on natural sepiolite in single and multi-component systems

Adsorption kinetics and equilibria of the azine dyes onto natural sepiolite are investigated using Methylene Blue, Thionin and Safranin O. Experimental equilibrium results for three azine dyes are well predicted by the Freundlich, Langmuir and Redlich-Peterson isotherm models. The model parameters obtained for single solute systems at 298 K are used for the calculation of adsorption isotherms in binary and ternary dye solutions using multi-component isotherm models. Modified extended Langmuir model is satisfactorily fit to the adsorption in binary and ternary solutions. The diffuse-reflectance-infrared-Fourier-transforms technique was used to characterize the bare and dye loaded sepiolite surface. The kinetic results for single, binary and ternary dye systems have been analyzed according to the pseudo-first-order and Elovich models. Vermeulen approximation was also applied to the data for prediction of the diffusion behavior of the dyes. The molecular chemical reactivity of the dye molecules estimated based on the Density Functional Theory was well correlated to the sorption results. The energy gap between the highest-occupied molecular-orbital and lowest-unoccupied-molecular-orbital energies, chemical potential, chemical hardness, softness, global electrophilicity and global nucleophilicity values prove that Methylene Blue is more reactive than Thionine and Safranine O cationic dyes.