Synthesis of feldspathoids and zeolite K–F from waste amber container glass

The hydrothermal formation of mineral products from a mixture of amber container glass and aluminium waste (Al:Si = 1) in 4 M NaOH(aq) or 4 M KOH(aq) at 100 °C was monitored at 1, 3 and 10 days by X-ray diffraction analysis with Rietveld refinement, Fourier transform infrared spectroscopy and scanning electron microscopy with energy dispersive X-ray analysis. In NaOH(aq), at 1, 3 and 10 days, respectively, 48%, 55% and 63% of the glass crystallised to form hydroxysodalite (HS) and hydroxycancrinite (HC) with minor proportions of katoite and tobermorite. The partial successive transformation of HS to HC was also observed with time. The initial rates of dissolution of the glass and formation of the principal zeolite K-F and secondary katoite phases were considerably slower in KOH(aq); although, the subsequent development of the products was greater than that in NaOH(aq). The zeolite K-F product achieved only 5% crystallinity within the first day which then increased markedly to 60% and 78% at 3 and 10 days, respectively. Despite the incomplete conversion of amber glass into crystalline zeolitic phases, the uptake capacities of the 10-day feldspathoid and zeolite K-F products for Pb2+ (4.3 and 4.5 meq g-1, respectively) and Zn2+ (3.9 and 4.1 meq g-1, respectively) ions compared favourably with those of many other zeolites and waste-derived inorganic sorbents reported in the literature.