Uptake of Hg2+ from aqueous solutions by microporous titano- and zircono-silicates

Abstract

Recebido em 7/3/07; aceito em 27/7/07; publicado na web em 26/2/08Being mercury one of the most toxic heavy metals present in the environment, it is of major concern to develop cleanup technologies to remove it from wastewater and recover mercury polluted ecosystems. In this context, we study the potential of some microporous titanosilicates and zirconosilicates for taking up Hg 2+ from aqueous solutions. These materials have unique chemical and physical properties, and here we are able to confirm that they readily remove Hg 2+ from aqueous solutions. Moreover, the presence of the competitive Mg 2+ and Na + , which are some of the dominant cations in natural waters, does not reduce the uptake capacity of some of these materials. Thus, several inorganic materials reported here may have important environmental applications, efficiently removing Hg 2+ from aqueous solutions.

Removal of Hg2+ ions from aqueous solution by ETS-4 microporous titanosilicate—Kinetic and equilibrium studies

“…Main relevant properties of ETS-4 related to its sorption capacity have been shown elsewhere [12]. [13]. The centres of black octahedra and grey tetrahedra are occupied by Ti and Si atoms, respectively.…”

“…Some studies have demonstrated that titanosilicates are excellent materials to remove Hg 2+ from aqueous solutions [12][13][14][15]. Because of their unique structure, these materials display important chemical and physical properties, such as selective sorption, ion exchange and catalytic activity.…”

Effect of pH and temperature on Hg2+ water decontamination using ETS-4 titanosilicate

“…However, the speciation diagram of Hg (II) species in aqueous solution (Fig. 4) indicates that the dominant Hg(II) species at pH > 4 is Hg(OH) 2 , it has been proved for an initial Hg(II) concentration ≤120 mg dm −3 in solution that Hg(OH) 2 dissolves [10]. Thus, since the Hg(II) concentration used was 50 g dm −3 (<120 mg dm −3 ), the cation exchange process proceed and it was favoured by the lower H + competition.…”

“…It has been shown that the application of microporous titanosilicates for removing priority pollutants such as Hg 2+ and Cd 2+ ions from water may lead to the development of efficient cleanup technologies [1][2][3][4]. Among these microporous materials, the most promising for Hg 2+ ions removal is titanosilicate ETS-4 (Na 9 Ti 5 Si 12 O 38 (OH)·12H 2 O) a prominent member of the class of microporous heteropolyhedra transition-metal silicates.…”

Thermal stability of barrerite and Na-exchanged barrerite: An in situ single crystal X-ray diffraction study under dry conditions

“…Microporous zirconosilicates constitute an interesting class of materials owing to their potential applications such as catalysts, sorbents, and ion-exchangers [1,2,3,4]. They are usually referred as heteropolyhedral framework silicates with a "zeolite-like" structure made up of cornershared SiO4 tetrahedra and ZrO6 octahedra.…”