HIGH ADDED VALUE PRODUCTS FROM OFF-QUALITY WASTE GLASS

摘要

The upgrading of the waste glass amounts, such as multicolour and/or anyway surplus cullet, unused in the current recycling, has been investigated. The promotion of the waste to raw material is proposed by recovering a valuable part of its silica and alkali content by an extractive treatment in an alkaline aqueous medium where the waste glass in a powdered form and under moderate temperature and pressure conditions may give in short times two marketable products. By employing a sodium hydroxide solution as the extractant phase, the extracted products are sodium silicate and/or silica while the unextracted phase contains monosilicates of calcium and sodium and unreacted glass particles. Applications of the first product may be those for alkaline silicates. One of them (i.e., as silica source in the syntheses of zeolites) is particularly interesting, in our opinion, because, when used in combination with the silicate extraction from glass powder, the alkali employed may be recycled and that extracted from glass may represent a further valuable co-product. As regards the unextracted phase, uses alternative to disposal are being studied in order to support the economy of this treatment.