Ammonia removal properties of lightweight aggregates from Si-Al-Fe and Si-Ca rocks

Lightweight aggregates commonly used as construction materials contain high percentages of metal oxides and thus are potential sorbents in aqueous systems. Here, ammonia is used as the model compound to be removed by aggregates since it is toxic for the aquatic life and is regulated in physical systems. The point of zero charge of aggregates is determined at pH values higher than 9. The aggregates made with raw materials from Larisa, Milos, and Samos presented ammonia sorptive capacities of 210, 220 and 400 mu mol/kg, respectively. However, the LWA made from wollastonite (Samos) resulted in high pH (10.6) solutions and thus, production of toxic unionized ammonia. Thus, a combination of high sorptive uptake and neutral pH in solution is desired and can be achieved in future studies by selecting the appropriate raw materials for the preparation of aggregates.