Trona, Na(2)CO(3)center dot NaHCO(3)center dot 2H(2)O, is mined as the primary source for sodium carbonate production in the United States. Recent studies have shown that the flotation method can be used for pre-processing of trona ore to remove insoluble mineral contaminants for the production of soda ash (sodium carbonate). Studies with carbonate salts suggest that certain important factors can affect their flotation response, including viscosity of the brine and interfacial water structure. Flotation studies showed that contrary to the strong flotation of NaHCO(3) with both anionic and cationic collectors, Na(2)CO(3) does not float at all. Based on the analysis of interfacial water structure in saturated brines, Na(2)CO(3) was found to act as a strong water structure maker, whereas NaHCO(3) acts as a weak water structure maker. Bubble attachment time measurements suggest that collector adsorption at the surface of NaHCO(3) induces flotation; this is not the case for Na(2)CO(3). Contact angle measurements indicated that the surface of Na(2)CO(3) is hydrated to a great extent, whereas the NaHCO(3) Salt surface is less hydrated. These results reveal that there is a strong relationship between the interfacial water structure and the contact angle of these salts. The less stable NaHCO(3) surface is ascribed to the inter-facial water structure which allows for NaHCO(3) flotation with both anionic and cationic collectors. (C) 2008 Elsevier Ltd. All rights reserved.