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Chemical Stabilization of Contaminated Soils
Published in David J. Wilson, Ann N. Clarke, Hazardous Waste Site Soil Remediation, 2017
The literature contains a great many data on the precipitation or stabilization of lead. As with the other metals, most of this comes from the water treatment area, but an increasing body of information is specific to stabilization of lead in S/S systems. The standard methods of lead removal from wastewater are to precipitate it as the hydroxide, carbonate, or basic carbonate, all of which are relatively insoluble at alkaline pH. Lead in wastewater has been precipitated out with lime and ferrous sulfate [71] and with dolomite (CaCO3 ⋅ MgCO3) to yield lead carbonate [72]. Organic lead compounds in wastewaters can be oxidized to yield inorganic lead, which is precipitated at pH 8 to 9.5 in the presence of carbonates. Sulfides have also been used for this purpose, as has ferrous sulfate at pH 10.4 to 10.8. However, as we have seen, wastewater data are often not very useful in S/S work. The complex matrices and high ionic strengths create a very different environment for precipitation, and equilibrium concepts have limited applicability. We do know that pH control is important. Minimum lead leaching in nearly all S/S systems occurs when the pH is maintained between about 8 and 10 in the leachate [3]. A summary of the various processes that have been reported for lead in residues is given in the following list. Portland cementPortland cement + aluminum sulfateCement/soluble silicatePotassium silicateCement/soluble silicate + sodium sulfideCement/soluble silicate + ammonium phosphateLimeSulfideLime/fly ashKiln dustProprietary
Mechanism of incipient annular corrosion of high-tin bronze in simulated soil solution
Published in Corrosion Engineering, Science and Technology, 2023
Tingyan Gao, Yuqing Wu, Julin Wang
After 24 h of corrosion, EDS test findings showed that the lead, carbon and oxygen contents reached 69.5, 10.4 and 12.3 wt-%, respectively, indicating that lead carbonate was produced in situ (Figure 4a). Secondary electron images revealed the surface morphology of the bronze samples corroded for 56 days in the chloride-free solution (Figure 4(b)). The aggregate white corrosion substance, which contained 46.8 wt-% lead and 18.8 wt-% oxygen, is a type of corrosion product formed in situ by lead particles, and it may either be lead oxide or lead carbonate. The local area of depression in centre of the α-phase sample was enlarged (Figure 4(c)). The surface of sample was dispersed with granular corrosion, similar to the corrosion generated in the depression at the centre of the α phase (as point 1 or 5), based on its elemental composition, we hypothesised that it may be a copper oxide, tin oxide or a mixture of the two. The matrix preserved the dendritic segregation morphology after 56 days of corrosion.