REV. CHIM. (Bucharest) ♦ 62♦ No. 8 ♦ 2011 http://www.revistadechimie.ro 782 Removal of Mn(II), Ni(II) and Cu(II) Ions from White Wine through Ion Exchange in Microporous Mordenite and Mesoporous Al-MCM-41 CAMELIA ELENA LUCHIAN 1 , VALERIU V. COTEA 2 , ION SANDU 3 *, VIOLETA ELENA COPCIA 1 , NICOLAE BILBA 1 1 ”Al. I. Cuza” University, Faculty of Chemistry, Laboratory of Materials Chemistry, 11 Carol I Bd., 700506 Iasi, Romania 2 University of Agricultural Sciences and Veterinary Medicine 3, Mihail Sadoveanu Alley, Iaºi, 700490, Romania 3 ”Al. I. Cuza” University, Scientific Platform ARHEOINVEST, 11 Carol I Bd., 700506 Iasi, Romania The application of ion exchange microporous (mordenite) and mesoporous Al-MCM-41 molecular sieve to the metal ions K(I), Fe(II), Mn(II), Ni(II) and Cu(II) removal, of white wine has been studied. The experimental results demonstrate that ion exchange is effective for metal ions removal and the materials used do not modify the qualities of the wine. The ion exchange capacity of these materials is not entirely available for metal ions retaining and on the negatively charged surface the policondensation of small proteins takes place. Keywards: wine, Al-MCM-41, mordenite, ion-exchange Browning and lack of color quality are the main problems occurring during wine storage and greatly affect wine quality. It has been known [1, 2] for many years that the phenomenon of browning is due to the oxidation of the polyphenolic compounds present in the wine. The first step of this process is the oxidation of phenols to quinones by a nonenzymatic chemical reaction catalyzed by metals like copper(II) and iron(II, III) [2] or an enzymatic reaction with the intervention of polyphenol oxidase [3]. The nonenzymatic chemical reaction is predominant in wines because the polyphenol oxidase activity, initially present in the must, diminishes during fermentation [4]. Besides, the polyphenol oxidase enzyme is able to catalyze the oxidation of phenols to quinones but polymerization reactions are nonenzymatic. These alterations in the organoleptic properties lead to the rejection of the wine affected, which causes not only ûnancial loss but also loss of consumer confidence in wine. The metallic content of a white wine appears to play an important role in its browning [5]. Iron is very widespread in the earth’s crust (O, Si, Al, Fe etc.), representing a little over 5% of total mass. It is soluble in the form of ferrous and ferric salts. Both forms occur in wine, maintaining an oxidation–reduction balance according to the electro-active redox system below: The iron(II) content in commercial wine has to be in the range of 0.5-5 mg/L, in accordance with European Union Legislation, but for the house wine it could reach 20mg/L [6]. Producing wineries have for many years been trying to reduce metallic content by adding various substances to the wine. Notable among these is the use of potassium hexacyanoferrate (II) which causes the elimination of part of the iron content, together with significant reductions in the content of other metals that also participate in the browning and are highly contaminating (Mn, Cu, Zn etc.) * email: sandu_i03@yahoo.com [7]. The use of this complexing agent carries with it the risk of the possible transformation of the excess quantity into hydrocyanic, a highly toxic compound [8] as well as the production of residuals without utility. In recent years, the search has begun for alternative methods that enable the metallic content of the wine to be reduced without altering its composition [9-13]. Ordered mesoporous silica and aluminosilica of the M41S family, first synthesized 1992 [14] have important technological applications as size selective adsorbents sieves, ion exchange, supports for catalysts or as nanoscale reactors [15]. Among the members of M41S family of materials, the so-called MCM-41 have been most widely studied, mainly because of its pseudo-crystalline and textural properties, such as the hexagonal arrangement of one-dimensional channels [14] with a sharp pore –size distribution and large specific surface area [16]. Introduction of foreign ions, for instance, aluminum ions, into the silicate framework has been proved to be an efficient route for modifying the surface acidity of Si-MCM- 41 [17]. Bronsted acidity of Si-MCM-41 could be enhanced significantly after modification with aluminum ions [17]. The Bronsted acidity of aluminosilicates generally arises from the presence of accessible hydroxyl groups or in the form of ‘‘bridging’’ Si-(OH)-Al hydroxyl groups (structural hydroxyls) associated with 4-coordination framework aluminum. Mesoporous material Al-MCM-41 can be used as acid catalyst and as ionic exchanger [18]. Mordenite is a mineral or synthetic zeolite with the chemical formula: Natural mordenite has the Si / Al ratio ranging between 4.2 - 5.9. This ratio leads to a high thermal and chemical stability. The structure after dehydration is stable up to 900 o C [19].