Removal of toxic metals from petroleum produced water by dolomite filtration

We conducted experiments and reactive transport simulations to assess the removal of high concentrations of toxic metals (100 mg/L) commonly found in produced water from high saline waters (45,000-115,000 mg/L) using dolomite filters made of compressed powdered dolomite. The focus was on Ba, Sr, Cd, Pb, and As, as well as on guar gum as a metal complexing additive. We found that salinity has a significant impact on the removal of Sr and Ba but a mild impact on the removal of Cd. An increase of pH due the dissolution of dolomite increases the removal of Cd more significantly than the removal of Ba and Sr. The formation of guar-gum complexes of metals in the aqueous phase attenuates the removal of Sr, Ba, and Cd by dolomite filtration, this attenuation process is more significant for Cd than for Sr and Ba. The affinity sequence for the sorption of toxic metals at salinity levels of PW is Pb > Cd > As > Ba > Sr. Higher removal levels predicted for Sr than for Ba and over predictions of Cd removal using previously proposed surface complexation models for dolomite highlights the necessity of further experimental research to incorporate molecular scale surface crystal structure parameters into surface complexation models.

Automated summary

In this study, we evaluated the removal of toxic metals from high saline waters using dolomite filters. The results showed that the salinity had a significant impact on the removal of Sr and Ba, but a mild impact on the removal of Cd. The increase of pH due to dolomite dissolution enhanced the removal of Cd more significantly. The formation of guar-gum complexes attenuated the removal of Sr, Ba, and Cd by dolomite filtration, with a greater effect on Cd. The affinity sequence for the sorption of toxic metals was Pb > Cd > As > Ba > Sr at the salinity levels studied.