Structure-Activity Relationships between the State of Silver on Different Supports and Their I2 and CH3I Adsorption Properties.

In this study, the performances of silver-impregnated adsorbents prepared from different host supports (SBA-15, alumina, ceria, and faujasite Y zeolite) and calcined or not at 500 °C (1 h) were compared for the capture of I2 and CH3I. By keeping the silver content rather similar (about 15-17 wt %) among the sorbents, it was possible to assess the effect of silver dispersion and speciation on the adsorption capacities measured for both adsorbates. In a first part, several characterization techniques (XRD, DRS-UV-Vis, TEM, etc.) were used to probe the state of silver in the calcined and non-calcined materials. It was found that the characteristics of silver species are strongly influenced by the thermal treatment, the presence or absence of exchange sites, and the stability of the supports. Silver agglomeration was enhanced after calcination at 500 °C especially for supports bearing no exchange sites (SBA-15) or no ordered pores (alumina and ceria). Then, the adsorption performances of the studied silver sorbents were discussed in relation with their physicochemical characteristics. After-test characterizations were useful to assess the proportion of silver species that have reacted with CH3I and I2 to yield AgI precipitates. Depending on the adsorbate, different trends were obtained. I2 adsorption/reaction with silver sites was found to be quantitative (I/Ag ≈1), whatever the silver speciation and dispersion on the support. By contrast, a high proportion of cationic silver species was found essential to increase CH3I adsorption (I/Ag about 0.6-0.7 against 0.2-0.3 for Ag agglomerated species).

Photocatalytic oxidation of cationic dyes in single and binary solutions in presence of Zn-Cd oxides obtained from calcined LDH.

In the present paper, zinc and cadmium layered double hydroxides (ZnCd-LDH) have been prepared through co-precipitation route then calcined at different temperatures. Their photocatalytic activity was determined by photodegradation of industriel toxic dyes (rhodamine B (RB) and crystal violet (CV)) in single and binary solutions illuminated with UVA or sunlight irradiation. It was found that the highest photodiscoloration efficiency was obtained for the nanomaterial heated at 700 °C (ZnCd-700). The physicochemical properties of ZnCd-LDH and ZnCd-700 were determined by PXRD, FTIR, DSC, TG/DTG, and DRS-UV-Vis. By heating the ZnCd-LDH material, some demixtion to ZnO and CdO phases occurred, corresponding to a band gap energy value of 2.93 eV for the formed zinc oxide nanoparticles. The results revealed that with 1 g·L-1 of ZnCd-700 dose, the photodiscoloration of dyes was enhanced significantly where in single solution, it was > 83.9% and ≥ 98.0% in 90 min of UVA ilumination and sunlight, respectively. Whereas, the removal of CV and RB was > 89.7% and ≥ 98.7% in binary solution under UVA and solar irradiations, respectively. The superoxide anion radical (O2•-) was identified as the most influential reactive species for dyes degradation. In binary solution, the CV dye was photodiscolored faster than RB while in single solution, the result was the opposite. The re-use study of ZnCd-700 as photocatalyst showed a slight decrease of dyes discoloration varying between 1.4 and 7.1% from the second to the fourth use.

Zeolite in tissue engineering: Opportunities and challenges.

Tissue engineering and regenerative medicine follow a multidisciplinary attitude to the expansion and application of new materials for the treatment of different tissue defects. Typically, proper tissue regeneration is accomplished through concurrent biocompatibility and positive cellular activity. This can be resulted by the smart selection of platforms among bewildering arrays of structural possibilities with various porosity properties (ie, pore size, pore connectivity, etc). Among diverse porous structures, zeolite is known as a microporous tectosilicate that can potentially provide a biological microenvironment in tissue engineering applications. In addition, zeolite has been particularly appeared promising in wound dressing and bone- and tooth-oriented scaffolds. The wide range of composition and hierarchical pore structure renders the zeolitic materials a unique character, particularly, for tissue engineering purposes. Despite such unique features, research on zeolitic platforms for tissue engineering has not been classically presented. In this review, we overview, classify, and categorize zeolitic platforms employed in biological and tissue engineering applications.

Evaluation of Silver Zeolites Sorbents Toward Their Ability to Promote Stable CH3I Storage as AgI Precipitates.

In this study, up to 13 different silver zeolites sorbents were prepared by repeated ion exchange from their parent structures (FAU X and Y, MOR, *BEA, MFI, FER), characterized, and evaluated for their ability to capture methyl iodide in the context of a nuclear severe accident. A novel methodology was implemented to establish structure-activity relationships between sorbent properties and iodine trapping stability. After saturation of the zeolite bed with CH3I during a dynamic breakthrough experiment at 100 °C, a two-step quantitative desorption method was elaborated with the aim to quantify separately the CH3I fractions trapped by physisorption, chemisorption, or reacted as AgI precipitates. Besides, an analysis of the mechanisms involved in CH3I sorption and decomposition processes was also carried out. Overall, Ag/Y zeolites displayed the highest fractions trapped as stable AgI precipitates, thanks to the presence of high amounts of dispersed silver species at accessible locations in the large supercages, and their low sodium content.

Removal of binary dyes mixtures with opposite and similar charges by adsorption, coagulation/flocculation and catalytic oxidation in the presence of CeO2/H2O2 Fenton-like system.

In this study, the removal of binary mixtures of dyes with similar (Orange II/Acid Green 25) or opposite charges (Orange II/Malachite Green) was investigated either by simple adsorption on ceria or by the heterogeneous Fenton reaction in presence of H2O2. First, the CeO2 nanocatalyst with high specific surface area (269 m2/g) and small crystal size (5 nm) was characterized using XRD, Raman spectroscopy and N2 physisorption at 77 K. The adsorption of single dyes was studied either from thermodynamic and kinetic viewpoints. It is shown that the adsorption of dyes on ceria surface is highly pH-dependent and followed a pseudo-second order kinetic model. Adsorption isotherms fit well the Langmuir model with a complete monolayer coverage and higher affinity towards Orange II at pH 3, compared to other dyes. For the (Orange II/Acid Green 25) mixture, both the amounts of dyes adsorbed on ceria surface and discoloration rates measured from Fenton experiments were decreased by comparison with single dyes. This is due to the adsorption competition existing onto the same surface Cex+ sites and the reaction competition with hydroxyl radicals, respectively. The behavior of the (Orange II/Malachite Green) mixture is markedly different. Dyes with opposite charges undergo paired adsorption on ceria as well as homogeneous and heterogeneous coagulation/flocculation processes, but can also be removed by heterogeneous Fenton process.

Contributions of surface and bulk heterogeneities to the NO oxidation activities of ceria-zirconia catalysts with composition Ce(0.76)Zr(0.24)O(2) prepared by different methods.

The study of the catalytic activity towards NO oxidation to NO(2) was approached by using ceria-zirconia mixed oxides with the same nominal composition (Ce(0.76)Zr(0.24)O(2)) but prepared by different routes of synthesis: coprecipitation, solid combustion synthesis with urea, citrate complexation route, reversed microemulsion and template synthesis. The characterisation of the catalysts was performed by N(2) adsorption at -196 °C, XRD, Raman Spectroscopy, H(2)-TPR and XPS in order to ascertain the relationships between their catalytic activities and their bulk and surface properties. The results showed that the preparation method is critical for the physico-chemical properties of the mixed oxides, exhibiting very different BET surface areas, crystalline phase/s contributions and bulk oxygen mobility. The distribution of Ce and Zr on the surface with regard to the bulk is very much influenced by the preparation method as well. The NO(2) production from NO oxidation was shown to be mostly correlated with the Ce/Zr surface atomic ratio and the proportion of Ce(4+) (presumably in a doped cubic phase) in the uppermost layers.