期刊
CHEMICAL PAPERS
卷 75, 期 5, 页码 2225-2231出版社
SPRINGER INTERNATIONAL PUBLISHING AG
DOI: 10.1007/s11696-020-01446-1
关键词
Cr3+ removal; Typical tannery wastewater; Alkali doses; Nonlinear responses
资金
- SIP-IPN [20150006, 20201565]
The experiments showed that a stoichiometric or higher dose of alkali was needed to remove almost 100% of Cr3+; there was a nonlinear relationship between excess alkali and pH; the excess of Cr in the initial solution did not directly correlate to the remaining chromium in the supernatant; additionally, some excess of alkali contributed to increased sludge due to its inability to be dissolved under operational conditions.
We conducted a series of experiments to determine the effect of doses of CaO and Ca(OH)(2) added to a synthetic solution, prepared with the same salt of Cr as that found in Mexican tanneries, to precipitate the chromium and determine the amount of sludge. The stirring was kept at 150 rpm during 10 min of time of contact between reagents, followed by measurements of Cr in the supernatant and determination of the amount of sludge. The study was carried out in a wide range of dose of alkalis, including the stoichiometric value, and also we vary the initial concentration of Cr at fixed alkali doses, and duplicate both the concentration and alkali dose maintaining the stoichiometric ratio. To remove almost 100% of Cr3+, a stoichiometric or higher dose of alkali was necessary; nonlinear behavior was found between the excess of alkali and pH. Also, the addition of an excess of Cr in the initial solution was not reflected directly in remaining chromium in the supernatant. Finally, it was found that some excess of alkali contribute to increase the sludge because the impossibility to be dissolved at operation conditions.
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