Different routes of MgAl–LDH synthesis for tailoring the adsorption of Pb(II) pollutant from water

In this study, new adsorbents based on MgAl–LDHs were synthesized using combined precipitation (co-precipitation) route by modifying temperature and ageing time synthesis parameters, thus tailoring the adsorption capacity of Pb(II) ions from water. The synthesized materials were characterized by SEM, FTIR, XRD and $\text{N}_2$ adsorption–desorption techniques, highlighting the specific lamellar structure of layered double hydroxides (LDHs), as well as the functional groups present on the adsorbent’s surface. The maximum adsorption capacity for Pb(II) ions was 1151.97 mg/g for the MgAl–LDH synthesized at 55 °C and aged for 24 h. Sorption of Pb(II) ions occurs not only through co-precipitation in the form of characteristic compounds, $\text{Pb(OH)}_2$, $\text{PbCO}_3$ or $\text{Pb}_3(\text{CO}_3)_2(\text{OH})_2$, but also by complexation with surface hydroxyl groups

Different routes of MgAl–LDH synthesis for tailoring the adsorption of Pb(II) pollutant from water

In this study, new adsorbents based on MgAl–LDHs were synthesized using combined precipitation (co-precipitation) route by modifying temperature and ageing time synthesis parameters, thus tailoring the adsorption capacity of Pb(II) ions from water. The synthesized materials were characterized by SEM, FTIR, XRD and $\text{N}_2$ adsorption–desorption techniques, highlighting the specific lamellar structure of layered double hydroxides (LDHs), as well as the functional groups present on the adsorbent’s surface. The maximum adsorption capacity for Pb(II) ions was 1151.97 mg/g for the MgAl–LDH synthesized at 55 °C and aged for 24 h. Sorption of Pb(II) ions occurs not only through co-precipitation in the form of characteristic compounds, $\text{Pb(OH)}_2$, $\text{PbCO}_3$ or $\text{Pb}_3(\text{CO}_3)_2(\text{OH})_2$, but also by complexation with surface hydroxyl groups

Efficient degradation and mineralization of diclofenac in water on ZnMe (Me: Al; Co; Ga) layered double hydroxides and derived mixed oxides as novel photocatalysts

The removal of diclofenac (DCF) from aqueous solutions was attempted using photocatalytic processes, involving a series of novel photocatalysts based on ZnMe (Me: Al; Co; Ga) layered double hydroxides (LDHs) and their derived mixed oxides. The catalysts were characterized using specific techniques. Under solar light, ZnCo and ZnGa catalysts degraded almost completely DCF from water, while the mineralization, expressed by total organic carbon removal, reached $\sim$85%. The degradation mechanisms of DCF photolysis and photocatalytic degradation under solar and UV irradiation were investigated

CpG-creating mutations are costly in many human viruses.

Mutations can occur throughout the virus genome and may be beneficial, neutral or deleterious. We are interested in mutations that yield a C next to a G, producing CpG sites. CpG sites are rare in eukaryotic and viral genomes. For the eukaryotes, it is thought that CpG sites are rare because they are prone to mutation when methylated. In viruses, we know less about why CpG sites are rare. A previous study in HIV suggested that CpG-creating transition mutations are more costly than similar non-CpG-creating mutations. To determine if this is the case in other viruses, we analyzed the allele frequencies of CpG-creating and non-CpG-creating mutations across various strains, subtypes, and genes of viruses using existing data obtained from Genbank, HIV Databases, and Virus Pathogen Resource. Our results suggest that CpG sites are indeed costly for most viruses. By understanding the cost of CpG sites, we can obtain further insights into the evolution and adaptation of viruses

Mesoporous mixed oxides derived from pillared oxovanadates layered double hydroxides as new catalysts for the selective catalytic reduction of NO by NH3

International audienceThe mixed oxides derived from pillared oxovanadates LDH and copper substitutes pillared oxovanadates LDH with mesoporous properties have been prepared, characterized and tested as new catalysts in the process of the selective catalytic reduction (SCR) of NO by NH3. The results show that these materials are efficient catalysts for reducing NO to N2. The NO conversions are about 70–80% for an GHSV value equal to 414,000 h?1. The selectivity towards N2O does not exceed 2% on the whole range of temperature studied, 200–500 ?C though on the new catalysts ammonia oxidation occurs for temperatures above 430 ?C. On comparison to a conventional industrial SCR catalyst used for the DeNOx treatment of nitric acid plant endpipe, the mixed oxides derived from pillared oxovanadates and copper substitutes pillared oxovanadates layered double hydroxides are much more selective towards N2 though exhibit a weaker activity in NO reduction

Equilibrium and thermodynamic studies for the removal of As(V) ions from aqueous solution using dried plants as adsorbents

This paper reports the feasibility of using dried plants to remove As(V) from aqueous solution under different experimental conditions. For this purpose, micro-particles of both Calami rhizoma and Withania frutescens plants, have been separately used without pre-treatment as natural adsorbents. Effect of various process parameters, namely adsorbent dose, contact time, initial As(V) concentration, temperature, and pH has been studied. The experimental data were analyzed using Freundlich, Langmuir, and Temkin isotherm models to determine the mechanistic parameters related to the adsorption process. It was found that the Langmuir and Freundlich models fitted well. Thermodynamic parameters, viz, free energy change (ΔG0), enthalpy change (ΔH0), and entropy change (ΔS0), were also determined. The negative values of free energy change indicated the spontaneous nature of the adsorption and the positive values of enthalpy change suggested the endothermic nature of the adsorption process. The presence of some competing ions like Cl−, NO3-, Mg2+, Cd2+, Cu2+, and Zn2+ did not affect the arsenate uptake or removal, whereas HPO42- strongly interfered negatively

Development of horseradish peroxidase/layered double hydroxide hybrid catalysis for phenol degradation

International audienceBoth photocatalytic and enzymatic degradation of phenol were studied in order to evaluate and to compare the catalytic potential of both methods. For this, solar-sensitive ZnMe (Me=Al, Cr) layered double hydroxides (LDHs) and their derived mixtures of mixed oxides (MMOs) were synthesized via co-precipitation and calcination at 750 degrees C, while the calcined LDH at 550 degrees C was used for horseradish peroxidase (HRP) immobilization through absorption. The structural, optical and thermal properties of catalysts were investigated by XRD, FTIR, TG/DTA, TEM and UV-Vis analyses. We approached here for the first time the use of LDH-HRP biohybrid for phenol degradation. Further, since HRP operates similarly as photocatalysts, we also investigated the ability of LDH-HRP to generate photo-enzymatic responses, when the biocatalyst is used under solar light. Both degradation methods are able to remove phenol from solution via different pathways, namely step-by-step phenol photodegradation and phenol enzymatic polymerization, when an insoluble product is obtained at the end of reaction. After 7h of reaction, 95% of phenol was removed by a MMOs, while ZnAlLDH+light, ZnAlLDH-HRP and ZnAlLDH-HRP+light removed 20, 25 and 35% of phenol via photo-, enzymatic and photo-enzymatic catalysis, respectively

Horseradish peroxidase-AuNP/LDH heterostructures: influence on nanogold release and enzyme activity

International audienceGold nanostructures (AuNP) are important as strong platforms for targeted therapeutic and diagnostic applications. Tireless effort has been devoted nowadays to explore the multifunctionality of AuNP in multicomponent biostructures. Herein, we report the fabrication of horseradish peroxidase enzyme (HRP)-AuNP/ZnAlLDH heterostructure by the facile synthesis of AuNP on the biocompatible matrices of layered double hydroxides (LDH) followed by the immobilization of the enzyme on AuNP/LDH assemblies. During this process, ZnAlLDH have a dual function of exploring its structural memory effect" for the synthesis of nanogold and acting as a support for the enzyme immobilization. X-ray diffraction (XRD), UV-Vis spectrometry, transmission electronic microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and infrared (FTIR) spectroscopy have been used to characterize the structural, chemical composition, optical, and morphology of the novel materials. We present here the release of AuNP from HRP-AuNP/ZnAlLDH by using as controlled variables HRP:LDHs ratio and the pH of the solution. Results show that AuNP established close interactions with HRP and formed an HRP-AuNP bioconjugate. Results reveal that HRP suffers a significant loss of the activity in the presence of nanoparticles of gold, such that, AuNP act to inhibit the activity of the enzyme. AuNP behavior in enzyme-bio-heterostructures should be inspiring for future applications of AuNP in nanomedicine