In the present study, Ag nanoparticles modified Fe3O4 anchored on roughened halloysite nanotubes nanocomposites (Ag@Fe3O4/RHNT) with high peroxidase-like activity and good magnetism was fabricated, ...and accordingly, an efficient and sensitive colorimetric sensing platform was established for the detection of H2O2. Firstly, halloysite nanotubes was pre-treated and then Fe3O4 nanoparticles were uniformly deposited on the external surface of RHNTs. Finally, Ag nanoparticles were grown onto Fe3O4/RHNT by in-situ reduction method. All characterization results confirmed the successful synthesis of Ag@Fe3O4/RHNT. The resultant Ag-Fe3O4 RNHTs exhibited satisfied catalytic activity to the oxidation of TMB (4,4’-Diamino-3,3′, 5,5′-tetramethylbiphenyl) in the presence of H2O2, and the catalytic process is accompanied with the color changed from colorless to bule. Thus, a sensitive colorimetric sensor for detection of H2O2 was developed based on Ag@Fe3O4/RHNT nanocomposites. And the optimal reaction temperature and pH were determined to be 55 °C and 4, respectively. H2O2 can be detected in the range of 10–100 μM with the detection limit of 0.7 μM. In conclusion, we established an efficient colorimetric sensing system for H2O2, and applied it to detect H2O2 in milk and serum.
A facile and efficient sensing platform for H2O2 in milk was established based on the peroxidase-like activity of magnetic halloysite nanotubes nanocomposite (Ag@Fe3O4/RHNT) originated from its catalytic decomposition of H2O2 into ·OH and ·O2−. Display omitted
•A magnetic halloysite nanotubes based nanocomposite (Ag@Fe3O4/RHNT) was fabricated.•Ag@Fe3O4/RHNT was demonstrated to possess an enhanced peroxidase-like activity.•Colorimetric sensing platform for H2O2 in milk was constructed.•Ag@Fe3O4/RHNT catalyzed the decomposition of H2O2 into ·OH and O2.
MoS2 and montmorillonite (MMT) nanosheets were hybridized through a simple in-situ hydrothermal synthesis in order to develop an efficient adsorbent, MoS2/MMT composite, for the removal of mercury ...from water. Raman, XRD, and FTIR results displayed the good hybridization of MMT and MoS2. HRTEM images indicated that the active edges of MoS2 were clearly exposed in the hybrid, demonstrating the vital role of MMT as eco-friendly, cheap and stable substrate for the growth of MoS2. The overall adsorption process of Hg2+ on MoS2/MMT proved that the composite is highly efficient for the removal of Hg2+ from water, adsorbing up to 1836 mg/g of Hg2+, which outperformed most literature reported adsorbents. The adsorption kinetic and isotherm models could be well described by pseudo-first-order and Langmuir models, respectively. Furthermore, the Langmuir dimensionless constant, RL show that Hg2+ adsorption on the composite was found favorable to occur at the temperature of 25 °C and 35 °C. The XPS analysis revealed that the S sites and slight O sites were main contributors for the remarkable adsorption performance of MoS2/MMT composite on Hg2+ removal. This work suggests that MoS2 supported on MMT substrate might be a promising adsorbent with high capacity and super efficiency for the removal of heavy metals from aqueous solution.
Display omitted
•Preparation of MoS2/MMT composite through a simple in-situ hydrothermal method.•Efficient adsorptive removal of Hg2+ from water.•Investigation of kinetics and isotherm model.•Montmorillonite as supporting material to improve the dispersibility of MoS2 in water.•Elucidating the underlaying adsorption mechanism.
This work aims to prepare and characterize novel organo-montmorillonites (OMts) using a nonionic surfactant - octylphenol polyoxyethylene ether (OP-10), and apply the materials for the removal of ...cationic organic dyes. The nonionic surfactant OP-10 can be successfully intercalated into the interlayer of montmorillonite and the obtained OMts still keep cation exchange capacity. The structural configuration of surfactant molecules between clay mineral layers varies from the surfactant loadings. Moreover, OMts with higher surfactant loadings have higher organic carbon content but lower specific surface area. The prepared OMts showed enhanced adsorption capacities towards cationic organic dye methylene blue (MB), and the adsorption amount increases with an increase of surfactant loading. The high adsorption capacity can be attributed to the fact that the novel OMts still keep cationic exchange capacity and OP-10 has plentiful polyoxyethylene ether chains in its molecule structure, which can capture MB molecules through hydrogen bonding. A probable mechanism for the removal of MB was proposed to be a synergistic effect of ion exchange, partition adsorption, hydrogen bonding and electrostatic interactions. Kinetic and isotherm data could be fitted with pseudo-second order model and Langmuir isotherm. The adsorption thermodynamics study has proved the spontaneous and endothermic nature of the adsorption process. The nonionic surfactant modified OMts could be promising candidate adsorbents for the removal of cationic organic dyes.
Nonionic surfactant modified montmorillonites were prepared and applied for the adsorption of cationic organic dye MB. The adsorption mechanism of MB on the prepared organoclay was proposed to be the synergistic effect of ion exchange, partition adsorption, hydrogen bonding and electrostatic interactions. Display omitted
•Nonionic surfactant modified montmorillonites were prepared.•Structural configuration of surfactant molecules between clay mineral layers was proposed.•The organo-montmorillonites showed good adsorption capacity for a cationic organic dye MB.•The adsorption conditions for MB were systematically studied.•The adsorption mechanism was ascribed to be the synergistic effect.
This study investigated the effect of various dispersing media on the silane functionalization of sodium montmorillonite nanoclay (NaMt) to evaluate each medium's effectiveness on the intercalation ...and chemical grafting of silane coupling agent. The amount of intercalation was estimated using the equation that was developed in our previous work based on thermogravimetric analysis. The results showed that the amount of silane intercalation was the greatest for water and glycerol media (≈1.582mmol/g clay and ≈1.480mmol/g clay, respectively), which was in agreement with the d001-values calculated by the XRD analysis (≈19.6Å and ≈14.4Å, respectively). 29Si NMR results showed a new T site in addition to Q peaks for all modified nanoclays in different dispersing media, indicating the occurrence of silane chemical grafting at the surface of the nanolayers. The AT3AQ3 in NMR spectra was used to compare the amount of chemically grafted silane in different dispersing media, a new approach for Mt material. Hydrogen-bonding solvents (water, glycerol and ethanol), and polar solvents (DMF and THF) showed greater T3 peak intensities compared to other dispersing media, indicating higher amounts of chemical grafting of silane molecules. This observation was in agreement with the broadening of FTIR peak at 1130–1000cm−1, which is explained by the formation of extra SiOSi bonds; that is, in turn, due to silane chemical grafting at the surfaces of the nanolayers. The silane-nanofiller interactions were correlated with the Hansen solubility parameters of different dispersing media used for the modification. This research has potential to help design and improve the nanoclay modification processes, which are used in the fabrication of clay-polymer nanocomposites.
•Silanization of nanoclay was performed using various dispersing media.•Silane intercalation amounts were measured and correlated with d001-values.•The amounts of chemical grafting were compared by 29Si NMR and FTIR for all media.•Media with H-bonding resulted in higher silane intercalation inside interlayer spaces.•The silane grafting was correlated with Hansen solubility parameters of various media.
A review was undertaken of the investigations carried out on peloids and pelotherapy considering only the publications in English. More than 300 publications including articles, books and chapters of ...the books related to this theme were reviewed. Of them, a total of 198 have been chosen to be cited in the two papers related with this review (Part I and Part II), and 164 published in the period between 1990–2019 have been considered in this paper. In this work the publications related to mineralogy, chemistry, physical and physiochemical properties are included. In addition, studies concerning the presence of radioactive isotopes, peloid interstitial liquid, cation release and toxicity are also included. A historical background about peloids and pelotherapy, its definition and classification, application methods and the process of maturation are also considered. The organic compounds, microbiology and medical applications of peloids are reviewed in the paper: Clays in pelotherapy. A review. Part II: Organic compounds, microbiology and medical applications (Carretero, 2020). The studies have been classified into two blocks: i) studies about peloids which are known for their use in therapeutic purposes; and ii) a study of clays and other materials for its possible use in pelotherapy. Within this last block, the papers have been classified into: i) a study of clays and other materials without maturation (raw materials). ii) Studies of materials with seawater and salt lake water natural maturation, but which are not used up to now for therapeutic purposes, iii) Studies of clays with minero-medicinal water or seawater maturation at different times, and iv) Studies of peloids from spas and their raw materials with medicinal mineral water maturation at different times. Peloids that are used for therapeutic purposes in 18 countries have been considered. Peloids are formed mainly by phyllosilicates, quartz and feldspars. Most of them have also calcite and in some cases dolomite. As minor phases, gypsum, halite, aragonite and zeolites mainly appear. Mineral phases such as pyrite, alunite, Fe-oxides, sulfur and opal are also detected in peloids that come from a volcanic environment. The principal phyllosilicates are smectites, kaolinite, illite, illite–smectite mixed layer and chlorite. It is not possible to make a variability range of the physical and physicochemical properties of the peloids used for therapeutic purposes because there are not enough publications in which they determine the properties of them. In addition, those publications only study some of the properties, and the same properties are not in every publication. The studies concerning the suitability of clays for their possible use for therapeutic purposes show that the smectites are more considered than other phyllosilicates for pelotherapic applications. The specific heat depends on the quantity of water that the mixture of clay and water has. The mineralogical modifications, crystal chemistry and properties with the maturation period depend on the type of minero-medicinal water employed and they depend on the phyllosilicates and the minority minerals or traces that make up the clays. The more common period of maturation is between 2 and 3 months (maximum 6 months), although this result must be checked with the studies of the therapeutic efficacy of these peloids.
•There does not exist a complete characterization of the peloids used for therapeutic purposes from a mineralogical, chemical, physical and physiochemical properties point of view.•It is not possible to have a range of variability of the different properties of the peloids used for therapeutic purposes.•The peloids are formed mainly by phyllosilicates, quartz and feldspars. Most of them have also calcite and in some cases dolomite. As minor phases gypsum, halite, aragonite and zeolites mainly appear.•The principal phyllosilicates present in the peloids that are used for therapeutic purposes are smectites, kaolinite, illite, illite–smectite mixed layer and chlorite.•The possible toxicity of the peloids is described.•The studies concerning the suitability of the clays for their possible use in pelotherapy show that the smectites are more considered than other phyllosilicates for pelotherapic applications.
This review highlights a comprehensive study of three different layer double hydroxide (LDH) nanoparticles, e.g., MgAl-LDH, ZnAl-LDH and CaAl-LDH, w.r.t their biological and physicochemical (in vitro ...and in vivo) properties to encapsulate and deliver drugs with known pharmacokinetic profile in a sustained/modified manner for better therapeutic efficacy compared to the corresponding conventional treatments using bare drugs. With variable chemical compositions and high positive charge density in the brucite layers, these layered materials are potent anion exchangers and can accommodate plethora of drugs in the reactive interlayer space through ex situ anion exchange process. The tunable surface chemistry and tailor made particle size of the drug-LDH nanohybrid as above, facilitates their easy internalization in the diseased cell through endocytosis/fluid phase pinocytosis and thereby, delivery of the payload at the target site. Further, the biocompatibility and pH dependent biodegradability of the MgAl-LDH, ZnAl-LDH and CaAl-LDH nanovehicles are added advantages for their application not only in nanodrug delivery/nanomedicine but also in much futuristic area of molecular medicine involving the delivery of oligonucleotides/gene for the possibility of recovery of some of the deadly diseases of the recent times, with a prospect of zero/near zero adverse effects.
This review highlights a comprehensive study of three different layered double hydroxide (LDH) nanoparticles, e.g., Mg-Al-LDH, Zn-Al-LDH and Ca-al-LDH, w.r.t their physicochemical and biological (in vitro and in vivo) properties to encapsulate and deliver drugs with known pharmacokinetic properties and their modification to allow for their therapeutic delivery. Display omitted
ZnS/Zn-Al layered double hydroxide (LDH) heterostructures were synthesized by a mechanochemical method and characterized by a set of analytical methods: X-ray diffraction, Raman spectroscopy, ...thermogravimetric analysis, X-ray photoelectron spectroscopy and scanning electron microscopy. The photocatalytic degradation activity for Rhodamine B (RHB) under ultraviolet light irradiation exhibited a large enhancement with the increasing ZnS content, with 94% RHB degraded in 180min by using 2ZnS/Zn-Al LDH heterostructured composite, but only 75% by the LDH sample without ZnS. A detailed discussion was performed to understand the reason for the enhanced photocatalytic activity based on the efficient separation of photoinduced electrons and holes. This work provides an effective way to fabricate a series of LDH-based and transition metal sulfide-containing heterostructured photocatalysts.
•ZnS/Zn-Al LDH composite photocatalyst was gained by dry-milling Zn4CO3(OH)6·H2O, Al(OH)3 and Na2S·9H2O.•This composite showed enhanced removal performance for RHB over ZnS and Zn-Al LDH.•Heterojunction structure and synergistic catalysis mechanism was studied.
High-efficiency extraction of Al from coal-series kaolinite and its kinetics by calcination and pressure acid leaching has been studied in detail. Calcination process promoted a phase transform from ...crystal kaolinite to amorphous compounds. Subsequently, Al occurred in the compounds was efficiently extracted by pressure acid leaching. At optimal conditions, the extraction rate of Al reaches 98.7%. Pressure leaching process of Al was successfully described by Avrami model, and mainly controlled by chemical reaction when apparent activation energy was 16.29 kJ/mol. The complex extraction process of Al in heated acid leaching (diffusion-reaction-diffusion) was transformed into a simple chemical reaction during pressure leaching so as to realize a high-efficiency extraction of Al from coal-series kaolinite.
Display omitted
•Pressure acid leaching realizes a high-efficiency extraction (98.7%) of Al from calcined coal-series kaolin.•Leaching kinetics of Al during pressure acid leaching is successfully described by Avrami model.•Pressure leaching of Al is mainly controlled by chemical reaction with apparent activation energy of 16.29 kJ/mol.
Montmorillonite (MMT) aerogels with many excellent physicochemical properties of low density, high surface area, thermal stability and adjustable surface chemistry have been found as a new class of ...functional aerogels. Recently, MMT aerogels have aroused wide attention as the adsorbent for the removal of various pollutants posing a hazard to the environment and human health. However, MMT aerogels got limited in environmental remediation due to their poor mechanical properties and limited adsorption capacity. Numerous efforts have been done in the past few years with the aim to improve the mechanical properties and adsorption capacity of MMT aerogels. Here, we initially summarized and discussed the preparation and properties of MMT-based aerogels, including MMT-cellulose hybrid aerogels, MMT-chitosan hybrid aerogels, MMT-synthetic polymers hybrid aerogels, as well as MMT-graphene hybrid aerogels. Particularly, the applications of MMT-based aerogels in environmental remediation including CO2 capture, adsorption of oil and toxic organic compounds, dyes and heavy metal ions are analyzed in detail. Finally, the existing and future challenges of such materials are described to guide researchers to catch up with new opportunities in this promising field.
This review summarized recent progresses in the preparation of montmorillonite (MMT)-based aerogels and their applications in environmental remediation. Display omitted
The modification of montmorillonite clay mineral (Mt) was performed using the 3-aminopropyltriethoxysilane (γ-APS) silylation agent in different synthesis solutions. The modified products (S-Mt) were ...characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The XRD demonstrated that silane was intercalated in the interlayer space of Mt due to the increase in basal spacing. The basal spacing shown by some S-Mts suggests the presence of a double layer of aminopropyl molecules in the interlayer space of the clay mineral modified in water and in a hydroalcoholic media at both synthesis temperatures (50°C and 80°C). The TGA revealed the presence of peaks in the range of 200°C to 600°C due to the presence of adsorbed silanes, intercalated silanes and silanes chemically bonded between the clay mineral layers and/or the edges. Evidence showed that the presence of water in dispersant is essential for intercalation of the silane in the interlayer space of the Mt such that the S-MMTwater, S-MtE/A(50) e S-MtE/A(80) showed higher amount of silane and higher basal spacing in its structure. Qualitative evidence of the presence of γ-APS in the modified clay minerals was obtained by FTIR spectroscopy.
Display omitted
•Modification of Mt using γ-APS as silylation agent•Confirmation of the modification of Mt by XRD, FTIR and TGA•Double layer of the γ-APS in the interlayers space of the Mt
PDF