Monitor application of multi-electrochemical sensor in extracting bromine from seawater

In this paper, a set of online measurement devices of multi-electrochemical sensor was investigated. Combined with industrial distributed control system, it was first applied in extracting bromine from seawater to realize the real-time adjustment of production process parameters. In the process of extracting bromine from seawater, the pH value of acidified raw brine, the addition amount of Cl2 in the oxidation stage and the addition amount of SO2 in the absorption stage are key parameters to control the whole production process. The multi-electrochemical sensor realized a rapid and high-throughput detection of the above parameters by integrating an all-solid-stage bromide ion selective electrode (Br-ISE), Eh electrode and pH electrode. The Br-ISE and the pH electrode were self-developed electrodes and the Pt electrode was Eh electrode. The pH electrode was used to control the addition amount of H2SO4 during the acidification of the brine. The Eh electrode was used to control the addition amount of Cl2 during the oxidation stage and the addition amount of SO2 during the absorption stage. The Br-ISE was used to monitor the Br− concentration change in the raw brine. Results showed the optimum range of Eh in the oxidation stage and absorption stage of brine were 950–1000 mV and 580–610 mV, respectively. The application of multi-electrochemical sensor in industrial bromine production can realize real-time control of material addition and save the cost of production.


Recommendation?
Accept with minor revision (please list in comments)

Comments to the Author(s)
To begin with, the manuscript needs to be edited by a native English speaker, and Chinese characters removed from figures. I have followed the work of the group for years and I have no problem with the quality of the data. But, the presentation is another matter. For instance, the title may be confusing as it seems to suggest that the sensor is applied to extract Br but in fact the sensor is used to monitor the Br extraction system. Other minor problems: 1. DCS should be spelled out when first used; 2. ISE denotes ion selective electrode, not just ion electrode; Decision letter (RSOS-191138.R0)

12-Aug-2019
Dear Dr Wang: Title: Application of Multi-Electrochemical Sensor in Extracting Bromine from Seawater Manuscript ID: RSOS-191138 Thank you for your submission to Royal Society Open Science. The chemistry content of Royal Society Open Science is published in collaboration with the Royal Society of Chemistry.
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RSC Subject Editor:
Comments to the Author: (There are no comments.) ********************************************** Reviewers' Comments to Author: Reviewer: 1 Comments to the Author(s) The revision of the manuscript is required before acceptance and my comments are below 1. novelty be discussed 2. Have you checked selectivity of metal ions? How to find out quantitative analysis in the presence of metal ions. 3. How you explain mechanism without any supporting data?. Comments to the Author(s) To begin with, the manuscript needs to be edited by a native English speaker, and Chinese characters removed from figures. I have followed the work of the group for years and I have no problem with the quality of the data. But, the presentation is another matter. For instance, the title may be confusing as it seems to suggest that the sensor is applied to extract Br but in fact the sensor is used to monitor the Br extraction system. Other minor problems: 1. DCS should be spelled out when first used; 2. ISE denotes ion selective electrode, not just ion electrode (1) For the Eh electrode, the redox potential of the brine and waste liquor itself is measured, and the metal ion selectivity test of the Eh electrode is not necessary.
For all-solid bromine ion selective electrodes, as we investigated, the most serious interference is Cl -, not Mg 2+ , K + , Ga 2+ metal cations in brine. In our previous publication, we determined the selectivity of bromine ion electrodes by fixed interference ion method (FIM). [2] Please refer the details below.
Selectivity is one of the most important performance indicators of a sensor, and it usually determines whether the test is reliable. As the sensitive films, not only respond to the Br-, but have different degrees of response to other coexisting ion, therefore, the response of the film is only relatively selective, not absolutely specific. In this paper, the FIM (Fixed Interference

Method) recommended by the International Union of Theoretical and Applied Chemistry
(IUPAC) is used to determine the selectivity of interfering ions of bromide electrodes.
Where i is the ion to be measured, j is the interference ion, and a i , a j are the activity of the ion to be measured and the interference ion, respectively. n i , n j are the number of charges of the i and j respectively.  Table 1, the selectivity coefficients of the electrodes are listed to compare with previous reports. As can be seen table.1, the selectivity coefficients of Clis lowest of all, for others also keep in a low level, which means the as-prepared Br-ISE is generally superior to the best bromide ion-selective electrodes reported in literature. Comment 3: How you explain mechanism without any supporting data?
Response 3: Thanks for your comment. In fact, the explanation of mechanism was based on our previous published work. In this manuscript, we did not detailly study the mechanism since the mechanism was well established and suitable for the electrodes in the current study. The purpose to publish this study is to provide a strategy in sensor controlled automatic production process for but are not limited to the bromine factories.

Comment 4:
Did you the reversibility of sensor?
Response 4: Thanks. Because the emphasis of this paper is on the application of sensors in real production of bromine from seawater, the Eh electrode of pH electrode has shown good performance in the previous application, and the repeatability of the bromine ion electrode developed for the extraction of bromine from seawater has been discussed. [9][10] The Br-ISE is calibrated 9 times at different times, its Nernst slope remains basically unchanged, which also shows good repeatability.

Comment 5:
Following references must be included as literature is poor:

Response 5:
We have supplemented the relevant references in the manuscript.

Reviewer: 2
To begin with, the manuscript needs to be edited by a native English speaker, and Chinese characters removed from figures.
I have followed the work of the group for years and I have no problem with the quality of the data. But, the presentation is another matter. For instance, the title may be confusing as it seems to suggest that the sensor is applied to extract Br but in fact the sensor is used to monitor the Br extraction system. Other minor problems: Thanks for your suggestion. We carefully edited the manuscript again. The gramma errors have been revised and the presentation has been improved in order to enhance its readability. As for the title, the sensor is indeed used to monitor the Br extraction system. Therefore we changed the title of the manuscript as "Monitor Application of Multi-Electrochemical Sensor in Extracting Bromine from Seawater". has been revised as "bromide ion selective electrode (Br-ISE)". Many thanks.