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Hypochlorite Generation from a Water Softener Spent Brine

1
Centro de Desarrollo e Innovación Tecnológica, Industrializadora de Cárnicos Strattega S.A. de C.V. Km. 7.5 Carretera a Cuauhtémoc, Colonia Las Ánimas, Chihuahua 31450, Mexico
2
Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Chihuahua 31124, Mexico
3
Festa-Hidrogel S. A. de C.V. República de Colombia No. 219 Col Panamericana, Chihuahua, Chihuahua C.P. 31107, Mexico
4
Centro de Investigación en Materiales Avanzados, S.C. Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua 31136, Mexico
*
Authors to whom correspondence should be addressed.
Water 2018, 10(12), 1733; https://doi.org/10.3390/w10121733
Received: 13 September 2018 / Revised: 27 October 2018 / Accepted: 1 November 2018 / Published: 26 November 2018
(This article belongs to the Section Water and Wastewater Treatment)
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PDF [4812 KB, uploaded 26 November 2018]
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Abstract

Industries that require water with low hardness consume large amounts of NaCl for water softening. In this work, water softener spent brines were recovered and used as raw material in an electrolysis cell with cationic exchange membrane (CEM) to yield both sodium hypochlorite and sodium hydroxide amounts, which are the most common disinfectants used to sanitize production areas. Spent brines contained mainly an average of 4.5% NaCl, 650 mg L−1 Ca2+, and 110 mg L−1 Mg2+, the last two cations adversely affect the CEM and must be treated prior to the electrolytic process. Two hardness removal methods were evaluated separately—lime-soda ash and sodium hydroxide-soda ash softening—the last one being the most effective as total hardness was decreased by 99.98%. This pretreated spent brine was then introduced into the electrolysis cell. Experimental design comprised five level variations for current intensity, % NaCl, and time. The best operation conditions yielded 2800 mg L−1 NaOCl for a 5% NaCl solution. By incorporating chlorine gas trap to increase OCl concentration a maximum of 7400 mg L−1 NaOCl was achieved. Finally, biocidal activity was tested following sanitation protocols (NaOCl dilution level) on workbenches and a decrease in bacterial count of at least 5 logs under laboratory-controlled conditions. View Full-Text
Keywords: water re-use; spent brine; membrane processes water re-use; spent brine; membrane processes
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Sánchez-Aldana, D.; Ortega-Corral, N.; Rocha-Gutiérrez, B.A.; Ballinas-Casarrubias, L.; Pérez-Domínguez, E.J.; Nevárez-Moorillon, G.V.; Soto-Salcido, L.A.; Ortega-Hernández, S.; Cardenas-Félix, G.; González-Sánchez, G. Hypochlorite Generation from a Water Softener Spent Brine. Water 2018, 10, 1733.

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