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A mild chelating agent treatment was performed on the residuals of the sorting processes of separately collected urban glass, which is currently landfilled. This fraction, that represents about the 10 wt% of the overall collected glass, has a very heterogeneous composition and contains relatively high amounts of lead and barium and consequently cannot be used to produce new glass containers. This contaminated material shows, when used as fine aggregate in Portland Cement based composites, an expansive behaviour due to the alkali silica reactions. The expansion can only be partially reduced by using finely ground soda lime glass, showing pozzolanic activity. However, after the chelating agent treatment, because of heavy atoms surface depletion, the synergic effect of pozzolan addition leads to a suppressed expansion, thus allowing the use of waste in the formulation of cement composites. Graphical Abstract: [Figure not available: see fulltext.].

Glass with different chemical compositions, deriving from separate collection, has been used as fine aggregate to formulate cementitious mortars, substituting natural sand. Glass coming from cathode-ray tube monitors, fluorescent lamps, and crystal glass (from production of home decor items) along with glass deriving from soda-lime glass containers, which has been taken as a reference, have been investigated. Glass solubility has been determined in alkaline environment similar to the one inside the cementitious composite. Alkali silica reaction has been tested on glass modified cement mortar in different accelerated conditions. Mortar samples containing glass with chemical composition different with respect to soda-lime glass are subjected to alkali silica reaction. This behaviour is largely dependent on the ratio among modifier and stabilizer oxides in the glass. The same ratio affects glass solubility and consequently composition of expanding gels when alkali silica reactions take place.

This work focuses on treatment of lead polluted waste glass from urban collection (Pb≈5% wt) for its valorization as support in the immobilization of lipase, because soda-lime glasses are used in enzymatic catalysis. First of all, an extraction process of surface Pb was performed. The process is based on nitrilotriacetic acid (NTA) chelating agent. The operating conditions are: T=80°C, t=1h, pH 10, solid/liquid weight ratio=1/10, reagent concentration=0.1 M. Leaching tests at controlled pH performed on treated glass confirmed the typical inert nature of the glass and the effectiveness of the NTA treatment. Afterwards lead polluted waste glasses, both untreated and treated with NTA, together with a commercial reference glass, were used as physical supports for the adsorption of Rhizopus oryzae lipase, in order to investigate their immobilization capability after specific washing/activation treatments to make functional their surface. The biocatalytic activity of the immobilized enzyme on the glasses was tested through the hydrolysis of para-nitrophenyl acetate to para-nitrophenol, quantifying the conversion percentage after 60 min of reaction by means of UV analyses at 410 nm. From the first results, lipase immobilization on waste glasses appears to be encouraging. In particular, lipase immobilized on lead polluted glass from urban collection showed an activity comparable to that of reference glass