698
J. Dahlstrom et al.
Fig. 2 Eh-pH diagram of
arsenic species [2]
accomplished with lower reagent concentrations compared with alternative hydroxide precipitation systems. Overall, reactor volumes can be greater than competing
technologies to enable longer residence times, ensuring metals can be reduced to
desired levels [3].
Sulfide Precipitation
Sulfide precipitation treatment technologies operate with a similar concept to hydroxide precipitation, in reducing metal solubility through the introduction of sulfides,
generally sodium sulfide, directly to the waste stream. An example of soluble lead
precipitation by sulfide is shown below:
Pb
2+
+ S
2−
→ PbS
(6)
For the majority of industrial applications, this is accomplished by a multi-stage
treatment process that begins with increasing the waste water pH, generally above
J. Dahlstrom et al.
Fig. 2 Eh-pH diagram of
arsenic species [2]
accomplished with lower reagent concentrations compared with alternative hydroxide precipitation systems. Overall, reactor volumes can be greater than competing
technologies to enable longer residence times, ensuring metals can be reduced to
desired levels [3].
Sulfide Precipitation
Sulfide precipitation treatment technologies operate with a similar concept to hydroxide precipitation, in reducing metal solubility through the introduction of sulfides,
generally sodium sulfide, directly to the waste stream. An example of soluble lead
precipitation by sulfide is shown below:
Pb
2+
+ S
2−
→ PbS
(6)
For the majority of industrial applications, this is accomplished by a multi-stage
treatment process that begins with increasing the waste water pH, generally above