Lead glass-ceramics produced from the beneficial use of waterworks sludge

This study quantified the effects of lead stabilization by blending lead-containing sludge into glass-ceramics through sintering with aluminum- and silica-rich precursors. Using lead oxide (PbO) to simulate lead-laden sludge under thermal conditions, the predominant PbAl(2)O(4) phase was found at temperatures of 900-1000 °C while sintering with γ-Al(2)O(3) for 3 h. To analyze the influence of silica, amorphous SiO(2) and quartz were blended with γ-Al(2)O(3) for lead stabilization. The results revealed both silica precursors could crystallochemically incorporate lead into the PbAl(2)Si(2)O(8) structure, and the weight percentage of the PbAl(2)Si(2)O(8) phase ranged from 30% to 40% in the product after 3 h of sintering at 1000 °C. Furthermore, the calcined waterworks sludge was applied as a sintering precursor and found to result in 46 wt.% of PbAl(2)Si(2)O(8) in the sintered product, suggesting an effective and feasible waste-to-resource strategy for the beneficial use of waterworks sludge. Finally, a prolonged acid leaching experiment (lasting 23 d) evaluated the stability of lead in the PbAl(2)O(4) and PbAl(2)Si(2)O(8) phases. The concentration of lead in the PbAl(2)O(4) leachate was 30-times higher than that in the PbAl(2)Si(2)O(8) leachate at the end of the experiment, suggesting a preferred lead stabilization strategy of forming the PbAl(2)Si(2)O(8) phase.