Removal of chromate from tannery wastewater: the applicability of sulfate-green rust in real coprecipitation processes

Abstract

Ferrihydrite and green rust (GR) have been identified as promising removing agents for chromate. However, while ferrihydrite efficiency is the still too low for practical applications, it is not known whether GR is stable in real wastewater systems. In this work, we investigated the removal of chromate from a real tannery wastewater by using sulfate-GR and ferrihydrite. We studied the effect of pH and Cr/Fe molar ratios on removal performances and elucidated the removal mechanism by XRD analysis. We performed removal experiments from simple chromate-bearing solutions under non-oxidizing Ar atmosphere, and from complex solution under open air atmosphere.

Characteristics of the Properties of Absodan Plus Sorbent and Its Ability to Remove Phosphates and Chromates from Aqueous Solutions

“…The production is multistage, and the averaged wastewater has a neutral pH and contains up to several dozen ppm, however, at the pickling and chrome tanning step the acidic wastewater can contain even 2000–3800 ppm of chromium [ 6 , 7 ]. Tannery wastewater can also be slightly alkaline (pH 8) and contain smaller amounts of chromium (several ppm) [ 8 ]. Another example of a chromate-contaminated environment is an area of Hanford Site in Washington Stated (USA) [ 9 ].…”

“…The same effect was obtained by adjusting acidic tannery effluent to neutral pH using NaOH [ 23 ]. Chromates from tannery effluent also can be very effectively coprecipitated with mixed Fe(II) and Fe(III) cations at slightly acidic to neutral conditions (pH 5–7) [ 8 ]. However, precipitation technologies can only be beneficial when the resulting sediments are intermediates for further use, even more so when it requires the use of a large dose of reagents in the case of wastewater with extreme pH and high salinity.…”