MCM-41 “LUS”: Alumina Tubular Membranes for Metal Separation in Aqueous Solution

Abstract

Heavy metals are discharged to the environment through industrial effluents in which certain amounts of valuable metal ions such as gold and silver are present. Current technologies remove metal ions nonspecifically, which constitutes a serious difficulty for metal recovery and reuse. The present article describes the synthesis of MCM-41 (LUS-type) membranes and their further surface functionalization with aminopropyl and sulfonate groups to separate valuable and/or toxic metal ions species in aqueous medium. A feasibility test for metal-ion separation is demonstrated using two model systems: (1) toxic metal removal by separating anionic chromate from cationic copper ions and (2) precious metal recovery by separating gold from copper ions. The results reveal that aminopropyl functionalized LUS membranes might show high selectivity to Cu(II) for the Cu(II)/Au(III) system, approaching virtually infinite selectivity depending on the pH values of both the feed and stripping solutions and the concentration of chloride counteranions. We provide a critical discussion about the relative role of cation diffusion and migration to gain insight into the metal-ion separation mechanisms.

Crystallization and fusion behaviors, observed by adiabatic calorimetry, of benzene confined in silica mesopores with uniform diameters

“…We synthesized two species of mesoporous silica MCM-41 and one species of SBA-15 according to the procedures described in the literature [19,20]. The two species of MCM-41 were abbreviated as MCM-41 (16) and MCM-41(16/18), respectively, with carbon numbers of the surfactants used. In addition, we utilized mesoporous silica TMPS-4 provided by Taiyo Kagaku Co. Ltd. All mesoporous silica materials were washed with distilled water repeatedly and calcined at 873 K for 5 h to remove the surfactants and any other residues.…”

“…Figure 1 shows nitrogen adsorption/desorption isotherms of MCM-41 (16), MCM-41(16/18), TMPS-4 and SBA-15. All the isotherms are classified categorically as of type IV according to the IUPAC classification [31].…”

“…Now there are many experimental results on phase behaviors in liquid or solid states and on dynamic properties in the liquid states of the systems confined within silica-gel nanopores [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. These works cover not only basic scientific issues but also practical ones such as catalytic chemistry [15], separation chemistry [16] and soil 3 Author to whom any correspondence should be addressed.…”

Preparation of core (Ni base)–shell (Silicalite-1) catalysts and their application for alkali resistance in direct internal reforming molten carbonate fuel cell

“…However, the zeolite shell also increased transport resistant for the reactant resulting in lower conversion and thus requires more catalysts. It would be of interest to explore the possibility of mesoporous shells [52,53] to alleviate this shortcoming and the use of similar approach in other fuel cell systems [54,55].…”

Recovering Rare Earth Elements from Aqueous Solution with Porous Amine–Epoxy Networks

“…Currently, three primary strategies are employed for preconcentrating, recovering, or separating aqueous REEs and heavy metals, and these involve (i) liquid–liquid extraction; − (ii) membrane separation; − and (iii) adsorption via ion exchange resins, − functionalized organic/inorganic sorbents, − ,− and polymeric sorbents. − Liquid–liquid extraction typically utilizes expensive ionic liquids for REE capture and a batch centrifugation process for separating off the REE-absorbed extractant, while a mixed system of cationic/anionic ion exchange resins also generally suffers from complicated regeneration schemes. One promising group of porous polymer sorbents are those derived from amine–epoxide reactions conducted in a porogen, where a strong and chemically resistant polymer network is precipitated out via C–N bond formation.…”