With rapidly growing industrial development worldwide, the need for a new class of nanoparticles and techniques for treating wastewater remains a major concern to protect the environment. Layered ...double hydroxides and particularly LDH-containing hybrids are emerging as potential nano-sized adsorbents for water treatment. Recent studies have demonstrated LDH-containing hybrids as promising multifunctional materials for potential utilization in various applications such as, photo-catalysis, energy storage, nanocomposites and water purification. This article reviews the recent applications of LDH-containing hybrids as adsorbents for water remediation. The maximum adsorption capacities of various toxic heavy metals and dyes on different LDH hybrids were reported as 483mg/g for Pb2+, 95mg/g for Cd2+, 181mg/g for Cu2+, 649mg/g for Cr6+, 180mg/g As5+, 813mg/g for Hg2+, 450 for Ag+, 277mg/g for U6+, 1062mg/g for methyl orange, 185mg/g for methylene blue, and 1250mg/g for Congo red, which is comparatively higher than other commercial adsorbents. This review discusses the adsorption performance of manifold LDH-containing hybrids for treating various pollutants such as heavy metals and dyes. The mechanisms of interaction of LDH-containing hybrids with pollutants and the influence of key adsorption parameters such as pH, contact time, adsorbent dose and temperature have been comprehensively discussed. Moreover, the regeneration potential and reuse of spent LDH-containing hybrids and its toxicity effects have also been reviewed.
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•Recent studies about the potential of LDH-containing hybrids as adsorbents for water remediation are reviewed.•Mechanisms of adsorption and key influencing factors such as pH, temperature, dosage, and contact time are explained.•The regeneration of spent LDH-containing hybrids, its toxicity and challenges in its applications are discussed.
A specific oedometer cell has been set up to measure the swelling pressure of compacted montmorillonites at constant volume and to concomitantly visualise the evolution, upon wetting, of how the ...microstructure is organised through X-ray microtomography. The swelling pressure experiments were conducted with solvents of various natures. In addition to conventionally used water and saline solutions, we used an organic solvent (methyl methacrylate – MMA). We chose this to explore the effect of its different physical and chemical properties, and to differentiate the respective roles of crystalline and osmotic pressures on macroscopic swelling behaviour.
The results, which combined both swelling pressure measurements and quantification of microstructure evolution upon hydration for the two different solutes, give sound understanding on the development of osmotic and/or crystalline swelling and their relative impact both on the microstructure and on the magnitude of the macroscopic swelling pressure of compacted montmorillonites.
•A new oedometer is designed to follow swelling pressure and macropore evolution at the same time by X-ray tomography.•Hydration solutions' features (solute, MMA) influence the macroporosity decrease and swelling behaviour.•Swelling pressure evolution is correlated with macroporosity investigated on the X-ray tomography scale.•Crystalline and osmotic components impact aggregate fabric and modify the mechanical properties of a part of the sample.
Beads are versatile spherical drug delivery units that can be coated, filled into capsules or compressed as tablets to be orally administered. Crosslinking of chitosan (CS) and polyanions such as ...tripolyphosphate (TPP) results in beads with mechanical properties that could be improved by the addition of clay mineral particles to the bead network. Hybrid systems of palygorskite and chitosan have been shown to have advanced properties in biomedical applications as a result of the synergic effects of their combination. In this paper chitosan was intercalated with palygorskite (Pal) and the resultant hybrid was loaded with diclofenac, an anti-inflammatory drug. Chitosan (CS) beads crosslinked with sodium tripolyphosphate (TPP) were prepared and their properties compared to palygorskite/Chitosan (Pal/CS) beads. The synergic effects resulting from the clay/polymer hybrids were evaluated by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning transmission electron microscopy (SEM) and thermal analysis (thermogravimetric analysis, TGA, and differential scanning calorimetry, DSC). The results showed that chitosan and palygorskite interaction took place. Diclofenac sodium (DFNa) was used as model drug to reveal the effects of Pal within the bead structure. DFNa was successfully loaded into beads and FTIR analyses confirmed its presence. A drug release test was carried out in phosphate buffer medium (pH. 6.8). The results indicated that only 33% (w/w) of total drug was released from DFNa-Pal/CS compared to 66% (w/w) from DFNa-CS. The total amount of drug released fell significantly with the addition of palygorskite to the chitosan matrix. Pal/CS beads crosslinked with TPP were shown to be able of carrying diclofenac sodium, meaning they could possibly be used as drug carriers.
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•TPP crosslinked Palygorskite/Chitosan and Chitosan beads were synthesized.•Diclofenac sodium was successfully loaded into Pal/CS and CS beads.•Pal/CS is a promising material as carrier for drug delivery.
Clay-modified electrodes (CLMEs) have received attention in the development of electrochemical sensors and biosensors. This article reviews the use of CLME for these electroanalytical purposes. It ...includes an introduction to the structure of cationic and anionic clays, an overview of electron transfer occurring at CLME, and of the different modes of preparation of CLME. The analytical applications reported for CLME range from the preconcentration method applied to the detection of cationic species (i.e., metal cations) or organic molecules (i.e., water pollutants and drugs), to electrocatalytic sensors involving intercalated redox mediators in the electrochemical detection process, and finally to amperometric and potentiometric biosensors. Several enzymes have been immobilized within clay matrices and amperometric biosensors based on CLME are presented following the three modes of detection referred to as first, second, and third generation of biosensors, depending on the nature of the enzymes.
The complexation of allophane nanoparticles with cisplatin, cis-dichlorodiammineplatinum (II) (CDDP) to deliver platinum prodrug into cancer cells was investigated. Using human lung carcinoma (A549) ...cells, profound studies including cellular uptake (endocytosis) analysis of allophane nanoparticle, cell cycle arrest abilities and apoptosis induction profiles were discussed in detail. As well as the features against A549 cells to emerge a promising strategy to enhance their anti-cancer activity and to mitigate side-effects were discussed.
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•The complexation of allophane nanoparticles and CDDP platinum prodrug was examined.•Cellular uptake (endocytosis) analysis of AK70 particles was demonstrated.•Incubation with complex at same CDDP concentration led to moderate apoptosis of A549 cells.
Layered double hydroxides (LDHs), or so-called anionic clays, consist of cationic brucite-like layers and exchangeable interlayer anions. Because of their biocompatibility, some LDHs, such as Mg/Al, ...Zn/Al, Fe/Al and Li/Al-LDH, can be used as host materials for drug-LDH host–guest supramolecular structures. The anti-inflammatory drug fenbufen has been intercalated into layered double hydroxides for the first time by co-precipitation under a nitrogen atmosphere. The product has been characterized by powder X-ray diffraction (XRD), FT-IR spectroscopy, elemental analysis and thermogravimetry (TG) and shows an expanded LDH structure, indicating that the drug has been successfully intercalated into LDH. In addition, the dependence of the nature of the fenbufen intercalation process on conditions such as pH value and chemical composition of the host has been systematically investigated. The interlayer distance in the intercalated materials increases with increasing pH value, resulting from a change in the arrangement of interlayer anions from monolayer to interdigitated bilayer. Drug release characteristics of the pillared LDH materials were investigated by a dissolution test in a simulated intestinal fluid (buffer at pH 7.8). The results show that the drug release of supramolecular LDH materials was a slow process, especially in the case of Mg/Al intercalated materials, suggesting that these drug-inorganic hybrid materials can be used as an effective drug delivery system.
Surface ion-imprinting technique combined with a sacrificial-support process was established to synthesize Sr(II) ion imprinted polymer (S-IIP) palygorskite which acted as the sacrificial support. ...FT-IR, TEM, nitrogen gas adsorption and laser particle size measurements were employed for the characterization of S-IIP and non-imprinted polymer (NIP). Factors for the adsorption of Sr(II) ions were investigated. Under the optimum condition, adsorption and selective recognition of Sr(II) ions followed the order S-IIP
>
NIP. The adsorption equilibrium data were fitted by the Langmuir isotherm model and the monolayer adsorption capacity of S-IIP was 45.0
mg g
−
1
at 298
K, 53.5
mg g
−
1
at 308
K and 58.5
mg g
−
1
at 318
K. Adsorption was described by the pseudo-second-order kinetics, and the thermodynamic parameters also indicated that the adsorption process was spontaneous but endothermic. S-IIP was a promising adsorbent for the selective removal of traces of Sr(II) ions. It could be reused four times with only about 5% loss for adsorption and 17% loss for desorption.
► Attapulgite is a hydrated octahedral layered magnesium aluminum silicate mineral which have siloxane groups in the bulk and silanol groups on its surface. It is available to be a support in surface-imprinting technique because of its particular intensity, special structure, stable chemical property and abundant raw materials. ► Then a new approach was used to synthesize a novel ion-imprinted polymer (IIP) based on surface ion-imprinting technique with attapulgite as a sacrificial-support material and chitosan incorporated sol–gel process. During this process, attapulgite as a support material was coated with a pre-polymerization ion-imprinting mixture. In a following step, the attapulgite was dissolved and removed, resulting in hollow spherical beads (S-IIP) with greater surface area and pore volume. Subsequently, the adsorption behaviors of S-IIP and non-imprinted polymer (NIP) for Sr
2+ (containing adsorption parameters, isotherms, kinetics, thermodynamics, and selective recognition) were investigated, the structural characteristics and imprinting mechanism of S-IIP were discussed in detail. ► A model for selective removal of target radioelements could be set up according to the results.
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