Mechanisms Of Lead-Zinc-Copper Co-Stabilization In Glass-Ceramics From Sewage Sludge Incineration Residues

Due to the acceleration of urbanization processes,the disposal of sewage sludge with huge amount has become one of the most critical environmental concerns.Although incineration could reduce the sludge volume and make it more harmless,the sewage sludge incineration residues can also accumulate gradually and cause potential damage to environment.In addition.various industrial activities have produced a large number of industrial sludge containing heavy metals such as lead,copper and zinc,which has attracted extensive attention.The glass-ceramics have excellent performance in chemical resistance and loading capacity,and can effectively immobilize the leachable metals by incorporating them in both crystal structure and glass matrix.Three types of heavy metals?lead,zinc,copper?common in industrial production are selected to simulate the industrial sludge in the form of oxides.The sewage sludge incineration residue is adopted as the ceramic matrix for the simultaneous stabilization of sewage sludge and industrial sludge.This work studied the mechanisms of transformation,incorporation and competition of various heavy metals under different conditions,through the identification of phase compositions,investigation on microstructure,and test the leaching behavior of sintered products.And the effect of co-stabilization was evaluated by the amount of heavy metals in leachate.It is found that lead,zinc,and copper could achieve co-stabilization in the systems with different amounts of sewage sludge incineration residues.Lead is mainly transformed to PbAl₂Si₂O₈ and Pb₃?PO₄?₂,while copper and zinc are incorporated into the spinel phases within a certain temperature range.Moreover,zinc and copper are mainly distributed in crystal grains in the system with relatively higher content of matrix materials,but they are found to be mainly contained in the“matrix”of the system with lower content.However,lead is not affected by the content of matrix materials and is always distributed in the amorphous phases.In addition,the types and contents of the heavy metals also affect the phase composition of the reaction systems.Lead tends to combine with aluminum,silicon,and phosphorus,while zinc reacts easily with silicon and aluminum and copper is more likely to combine with iron.In both lead-zinc systems and lead-copper systems,the zinc and copper are always distributed in the crystal grains,and lead is in the region around the grains.The three types of heavy metals show different leaching behaviors.The increase in sintering temperature is beneficial to reduce the leaching ratio of lead and zinc,however,the ratio of copper is always maintained at a very low level for all samples.The increase in lead or zinc content in the sintered system significantly affect their corresponding peaks in the XRD pattern,and also affect their concentration in the leachates.Moreover,the increased concentration of zinc in leachate may due to the decrease in lead leachability,while the leaching behavior of copper is less affected by the content of heavy metals in the system.