Treatment Methods

Chemical methods of treatment include batch, continuous flow, or integrated with the production process. Table 8.3.4 lists several insoluble lead compounds and their corresponding solubilities at room temperature. The anions in these compounds and their sources are listed in Table 8.3.5.

Aluminum hydroxide from alum use aids in settling the lead sulfate formed. A combination of hydroxide, carbonate, and sulfide results in a buffered treatment solution, allowing a check on the effectiveness of clarification due to the formation of black lead sulfide. Hypochlorite can also be used to prepare the insoluble quadrivalent oxide:

Pb(OH)2 + ClO" ® PbO2 + H2O + Cl" 8.3(21)

At high pH, lead exists as the plumbate ion, PbOf" which can also be oxidized by hypochlorite.

PbOf" + ClO" + H2O ® PbO2 + Cl" + 2OH" 8.3(22)

In reality, wastewaters contain other substances that also

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