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A new pH sensor for water resource – SApHIRE

A new pH sensor for natural waters

Water quality is appreciated by many physico-chemical parameters including pH which is one of the most used. Technical innovations to reduce the cost and maintenance of these measurement systems are expected to improve the monitoring of water quality from procurement to the release into aquatic ecosystems.

Improving the quality of drinking water and aquatic environment

The European Directive of 2000 and the French Water Act of 2006 established a framework for the protection of water resources. They include the need for self-monitoring and regular checks on natural water, drinking water and waste water to assess the impact of human activities and to protect aquatic environments.<br />This objective can only be achieved through the deployment of numerous, inexpensive, reliable and low maintenance sensors. The water quality key indicators the more often measured are pH and conductivity. The main issue in Saphire project is to develop a new sensor combining conductivity and pH measurement to meet these expectations. The objective focuses on a technology and a method that increases durability while reducing the cost of the sensor itself and the human interventions (calibration, maintenance). The ultimate goal is to increase sensors density on particularly sensitive sites in order to ensure better water resource monitoring and early diagnosis of pollutions.

pH analysis concerns waters that can greatly vary in their composition. The measurements involve the purest water as well as drinking water or industrial waste water. The two issues addressed in the project, namely the method of measurement and electrode technology, will allow reaching a sensor that covers all of these applications.
Here, the concept is completely different from the traditional method of pH measurement which uses potentiometry and H+ ions sensitive membranes. It is based on a model describing the physical properties of water-electrodes interface. It will become possible to use simple conductive electrodes instead of sensitive membranes that require repetitive maintenance and calibration. In order to cover the measurement range of pH and conductivity of natural waters, new conductive materials will also be explored.

A new material from the family of Conductive Organic Polymers was created. Resulting from the electrochemical synthesis of polypyrrole (PPy), the new material called «micro-snails« presents a micrometer structure which was characterized with a scanning electron microscope. The synthesis of polypyrrole is easy to achieve and leads to highly ion-sensitive materials. This new material targets low cost pH measurements. Moreover, a new approach based on the physics of water-electrode interface has been developed. This approach allows the simultaneous calculation of the concentration of H+ ions and of the conductivity. It has been tested on different electrode geometries with various coatings (carbon, gold, platinum, steel), including planar electrodes as screen printed electrodes (SPE) or thin-film electrodes.

We have shown that the electrochemical synthesis of conductive organic polymer materials could lead to the development of new inexpensive and highly sensitive sensors for measuring pH. The new method for the simultaneous measurement of conductivity and pH of water which has been developed, allows the use of low cost sensors that can be used both as sensors for pH and conductivity. It is a step towards large-scale deployment of sensors to monitor the environment.

S. Chebil, M. O. Monod, P. Fisicaro, Direct electrochemical synthesis and characterization of polypyrrole nano- and micro-snails, (2014), Electrochimica Acta, Vol.123, pp.527-534.

S. Chebil, M. O. Monod, P. Fisicaro, R. Champion, Nouveau capteur de pH à base de micro-snails de polypyrrole pour l’analyse de l’eau, (2014), Instrumentation, Mesure, Métrologie, vol. 14, N°1-2, pp. 69-83.

S. Chebil, M. O. Monod, P. Fisicaro, Nouveau capteur de pH pour l’analyse de l’eau, Revue « Instrumentation & Interdisciplinarité – Capteurs Chimiques & Physiques », éditions EDP Sciences, 2014, pp. 381-386 (ISBN 978-2-7598-1116-8)

S. Chebil, M. O. Monod, P. Fisicaro, R. Champion, P. Faure, Nouveau capteur de pH pour l’analyse de l’eau, 6ème Colloque Interdisciplinaire en Instrumentation (C2i 2013), Lyon, France, 29-30 janv. 2013

S. Chebil, M. O. Monod, P. Fisicaro, R. Champion, P. Faure, Nouveau capteur de pH pour l’analyse de l’eau, Journées d’Electrochimie 2013 (JE 2013), Paris, France, 8-11 juil. 2013

M.O. Monod, « Procédé de calcul de l’acidité des eaux naturelles » logiciel déposé à l’APP (Agence pour la Protection des Programmes) le 13/07/2012

Many parameters are needed for monitoring quality of water resource. The most used are conductivity, temperature and pH. The aim of SApHIRE project is to show the industrial potential of a new water pH sensor based upon the concentration measurement of the H3O+ ions. The concept totally differs from the common method which consists in measuring the activity of the H3O+ ions. The device which does not contain any sensitive membrane and does not require any calibration, offers decisive advantages over the existing supply.
The first objective of the project is to validate the concentration measurement provided by the sensor versus the referenced measurement given in activity. The second objective is the electronic and mechanical integration of the sensor and its validation.
The valorisation structure involved in the project, will supervise the market study. The findings will enable us to consider, as appropriate, either assignments of patent licenses to companies in water analysis sector, or the creation of a start up.

Project coordinator

Madame Marie-Odile MONOD (CENTRE NATIONAL DU MACHINISME AGRICOLE, DU GENIE RURAL, DES EAUX ET DES FORETS - CEMAGREF ANTONY) – marie-odile.monod@cemagref.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Cemagref DVT CEMAGREF ANTONY
LNE LABORATOIRE NATIONAL DE METROLOGIE ET D'ESSAIS
Cemagref UR-TSCF CENTRE NATIONAL DU MACHINISME AGRICOLE, DU GENIE RURAL, DES EAUX ET DES FORETS - CEMAGREF ANTONY

Help of the ANR 262,734 euros
Beginning and duration of the scientific project: January 2012 - 24 Months

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