Layered double hydroxides and related hybrid materials for removal of pharmaceutical pollutants from water

Pharmaceuticals and their by-products are recalcitrant contaminants in water. Moreover, the high consumption of these drugs has many detrimental effects on body waters and ecosystems. In this timely review, the advances in molecular engineering of layered double hydroxides (LDH) that have been used for the removal of pharmaceutical pollutants are discussed. The approach starts from the strategies to obtain homogeneous synthesis of LDH that allow the doping and/or surface functionalization of different metals and oxides, producing heterojunction systems as well as composites with carbon and silica-based materials with high surface area. Adsorption is considered as a traditional removal of pharmaceutical pollutants, so the kinetic and mechanism of this phenomenon are analyzed based on pH, temperature, ionic strength, in order to obtain new insights for the formation of multifunctional LDH. Advanced oxidation methodologies, mainly heterogeneous photocatalysis and Fenton-like processes, stand out as the more efficient even to obtain the mineralization of the drugs. The LDH have the advantage of structural memory that favors regeneration processes. The reconstruction of calcined LDH can be used to improve drug removal, through a combination of adsorption capacity/catalytic activity. A meticulous analysis of the persistence, toxicity and bioaccumulation of the most common pharmaceuticals has allowed us to highlight the ability of the LDH to remove recalcitrant drugs at relatively low concentrations (ppm, ppb), in contrast to other mixed oxide nanostructures and homogeneous oxidation processes. In this sense, the mechanism of drug removal by LDH is discussed based on the importance of the use of composites, scavenger agents, Fenton and electro-Fenton processes, membranes, thin films and coatings, among others. In addition, the ecotoxicity of LDH is also reviewed to indicate that these layered structures can exhibit biocompatibility or high toxicity depending on the adsorbed drug and ions/metals that compose them. Undoubtedly, the LDH have a unique flexible structure with adsorption capacity and catalytic activity, facts that explain the important reasons for their extensive use in the environmental remediation of pharmaceutical pollutants from water.

The role of silver nanoparticles functionalized on TiO2for photocatalytic disinfection of harmful algae

Silver loaded TiO₂samples were prepared by photodeposition of different amounts of Ag⁺ions over commercial titanium dioxide (Evonik TiO₂P25) in aqueous media without the presence of sacrificial agents.

Effective photoreduction of a nitroaromatic environmental endocrine disruptor by AgNPs functionalized on nanocrystalline TiO2

Unprecedented photoactivity of silver nanoparticles photodeposited on nanocrystalline TiO₂ for the efficient reduction of 4-nitrophenol at room temperature is reported.

Improved O2 evolution from a water splitting reaction over Er3+ and Y3+ co-doped tetragonal BiVO4

Erbium–yttrium co-doped BiVO₄ with a tetragonal structure is synthesized by means of a surfactant free hydrothermal method.

Glucosinolate variation in leaves of Brassica rapa crops

Total and individual glucosinolate (GSL) content of leaves of vegetable turnip rape (Brassica rapa L. var. rapa) was determined in a set of 45 varieties consisting in early, medium and late types grown at two locations in northwestern Spain. The objectives were to determine the diversity among varieties in GSL content and to relate that variation with earliness and plant habit. Eight GSL were identified, being two aliphatic GSL, gluconapin (84.4 % of the total GSL) and glucobrassicanapin (7.2 % of the total GSL) the most abundant. Indolic and aromatic GSL content were low but also showed significant differences among varieties. Differences in total and individual GSL content were found among varieties, plant habit groups, and earliness groups. Total GSL content ranged from 19 to 37.3 μmol g(-1) dw in early and extra-late groups, respectively, and from 19.5 to 36.3 μmol g(-1) dw for turnips and turnip greens groups, respectively. These differences were consistent to values found for gluconapin content where the turnip group had the highest values (31.8 μmol g(-1) dw) and the turnip top group had the lowest (15.7 μmol g(-1) dw). Two varieties, MBG-BRS0429 and MBG-BRS0550 (from turnip greens and extra-late groups) and MBG-BRS0438 (from turnips and late groups), stood out as they had the highest total GSL content and could be used as a good source of these beneficial bioactive compounds. Elucidation of genetic diversity among crops can provide useful information to assist plant breeders to design improved breeding strategies in order to obtain varieties rich on GSL.

Seasonal variation in glucosinolate content in Brassica oleracea crops grown in northwestern Spain

Brassica oleracea L. crops including kales, cabbages, and Tronchuda cabbages are widely grown in northwestern Spain and Portugal but little information is available on leaf glucosinolate content of these crops. The objectives were to determine the diversity for the total glucosinolate content and profile on leaves in a collection of 153 kales, 26 cabbages, and three Tronchuda cabbages varieties grown at two growing seasons and to determine the seasonal variation of glucosinolates in cabbages and Tronchuda cabbage varieties. Sinigrin, glucoiberin, and glucobrassicin were the major glucosinolates found in kales. Glucoiberin was the most common glucosinolate in Tronchuda cabbages in both planting seasons and in cabbages sown in fall season whereas glucobrassicin and glucoiberin were the most common glucosinolates in cabbages in spring season. In kales the total glucosinolate content ranged from 11.0 to 53 micromol g(-1) dw, with a mean value of 26.3 micromol g(-1) dw. Four kale varieties (MBG-BRS0468, MBG-BRS0476, MBG-BRS0060 and MBG-BRS0223) showed the highest total sinigrin or glucobrassicin contents. So, they could be good candidates for future breeding programs. In cabbages, the total glucosinolate content ranged from 10.9 to 27 g(-1) dw. Total glucosinolate concentration during spring sowing (22 micro mg(-1) dw) was higher than those in fall sowing (13 micro mg(-1) dw). Regarding both high glucosinolate content and the agronomic value, MBG-BRS0057 and MBG-BRS0074 could be good sources of beneficial glucosinolates. The presence of high concentrations of sinigrin, glucoiberin, and glucobrassicin warrant further search into their potential use to enhance the level of these important phytochemicals in these edible crops.