Effective and Selective Adsorption of Zn²⁺ from Seawater on a Layered Silicate

Abstract

Concentration of ions and molecular species from water on solid surfaces is a topic covering a wide range of scientific and practical applications for such purposes as the removal of toxic compounds and the collection of noble elements and molecules. The adsorption-based process is one of the most promising strategies; therefore, searching for and designing adsorbents for target ions and molecules have been actively conducted. Layered inorganic solids and their derivatives are promising adsorbents with the following advantages: a) large surface area derived from well-defined nanostructures composed of an ultrathin layer (a so-called "nanosheet"), b) chemical and thermal stabilities when compared with their organic counterparts, and c) material diversity. [1] As for the ion-exchange selectivity on layered inorganic solids, it has been recognized that anions with higher charge and smaller size are preferred on layered double hydroxides.[2]Concentration of cationic species, especially heavy metals and radioactive ions, on ion-exchangeable layered materials, such as smectite clays, [3] synthetic micas, [4] layered metal phosphates, [5] and layered titanates, [6] has been studied so far. A wide variety of materials are available; [1,7] therefore, it is worth investigating the concentration of various cations on layered inorganic solids. To concentrate heavy-metal ions, the organic modification of layered [8] and mesoporous materials [9] has been conducted, and it was found that thiol groups attached on the solid surface played a role in the adsorption of Hg 2+ . Because of the demands for the environmental purification and collection of noble-metal ions, there is a need for selective ion-exchange processes for a wide variety of target elements using environmentally friendly materials.[10]Herein, we report the selective and effective adsorption of Zn 2+ on a layered silicate, magadiite. [11] Zinc is an element essential for life; it exists in seawater (at the concentration of 0.4 ppb) [12] and has been shown to be harmful to human and aquatic animal health. [13,14] Magadiite is a naturally occurring layered alkali silicate [11d] that can be readily synthesized by a simple hydrothermal reaction between silica, sodium hydroxide, and water. [11a,b] Therefore, the successful procedure reported herein opens up a new opportunity for collecting Zn 2+ from seawater. In addition, we found that the concentration of Zn 2+ can be achieved even in the presence of Cd 2+ , which often competes and disturbs the concentration and detection of Zn 2+ . [15,16] The characteristics of magadiite and other adsorbents examined in this study (another kind of Na + -type layered alkali silicate, octosilicate, [17] a naturally occurring Na +

Two‐Dimensional Layered Zinc Silicate Nanosheets with Excellent Photocatalytic Performance for Organic Pollutant Degradation and CO2 Conversion

“…Layered silicates as typical 2D inorganic materials have been widely used as catalyst supports as well as adsorbents, owing to their low cost and abundant reserves. [7] So far, however, the photocatalytic properties of these materials have been mostly ignored due to their photoinertness in nature.T he crystal structure of natural layered silicates,such as clay minerals (e.g., vermiculite,montmorillonite), consists of layers made up of two silicon-oxygen tetrahedral sheets fused to an edge-shared octahedral sheet of either aluminum or magnesium hydroxide. [8] Indeed, they have no photocatalytic activity under UV/Vis light irradiation.…”

Photochromic Intercalation Compounds

“…Nanoporous pillared smectites have been obtained using inorganic particles and small organic cations as pillars [68,69] Besides smectites, a large variety of layered solids with the ability to accommodate guest species in the interlayer space are available [7,15,17,21,22]. Layered alkali silicates are capable of incorporating guest species (organoammonium ions and polar molecules) in the interlayer space to form intercalation compounds [72,[76][77][78][79]. Organosilane grafted derivatives have been obtained previously [80][81][82][83][84][85][86][87][88][89][90][91].…”

Chemically stable magnetic nanoparticles for metal adsorption and solid acid catalysis in aqueous media

“…We consider that the majority of the incorporated divalent cations are occupying two exchange sites as reported in a sulfonic acid functionalized silica system. 54 For comparison, the adsorption capacity of some adsorbents (layered silicates, 55,56 an activated carbon, 57 a cellulose ber,…”