Optimum pH for Cr6+ Co-removal with Mixed Cu2+, Zn2+, and Ni2+ Precipitation

It is advisable to co-remove Cr(VI) with available Cu(II), Zn(II), and Ni(II) since they coexist in most plating wastewater. Previous studies showed that coprecipitation and adsorption are the main mechanisms contributable to Cr(VI) co-removal with Cu(II) precipitation, and both are highly pH depend...

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Bibliographic Details
Published in:Industrial & engineering chemistry research 2006-03, Vol.45 (5), p.1557-1562
Main Authors: Sun, Jing-Mei, Li, Feng, Huang, Ju-Chang
Format: Article
Language:English
Subjects:
Applied sciences
Chemical engineering
Exact sciences and technology
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Summary:It is advisable to co-remove Cr(VI) with available Cu(II), Zn(II), and Ni(II) since they coexist in most plating wastewater. Previous studies showed that coprecipitation and adsorption are the main mechanisms contributable to Cr(VI) co-removal with Cu(II) precipitation, and both are highly pH dependent. This study presents the effect of pH on Cr(VI) co-removal with mixed metal precipitation in batch tests and also in a continuous compact system. Batch tests indicate that a maximum of 46.8 mg L-1 Cr(VI) was co-removed with the precipitation of Cu(II), Zn(II), and Ni(II), each 150 mg L-1, at pH of 7.0−7.3. However, co-removal of Cr(VI) decreased significantly with further pH increasing. Therefore in the continuous system, a two-stage nucleated precipitation technology was designed with the first stage being operated at around pH 7.2 to obtain maximum Cr(VI) co-removal and the second stage at around pH 9.2 to achieve further Cr(VI) co-removal with Zn(II) and Ni(II) precipitation.
ISSN:0888-5885
1520-5045
DOI:10.1021/ie050956o