Can I use AgNO3 or HgSO4 in COD analyses for eliminating of chloride interference for samples containing high chloride in range of 3000-12000 mg/L, so that a 10/1 weight ratio of HgSO4/Cl- is maintained.
HgSO4 is mainly used for the removal of chloride interference in water/wastewater samples.
Thanks a lot Ashutosh. yes of coarse, but It is used when amount of Cl be less than 2000mg/L. I used HgSO4, but I couldn't determined COD, because HgSO4 didn't eliminate interference of Cl.
The 2000 mg/L of chloride is the limit within which the HgSO4 in the reagent solution can remove the chloride interference - as per the test procedure. Instead of adding more HgSO4, which is also not ecofriendly, why don't you dilute the sample solution? This strategy applies only when you have COD within the limit of detection after dilution. If you think that, that may introducce errors in your measurement, you may have to run duplicate samples. Serial dilution shall reduce errors if you have to dilute more.
Hi Sellappan. Thanks very much for your guidance, Your solution can be a good method. because HgSO4 is really hazardous for environment.
If wastewater is more concentrated than dilute it and estimate the COD. This is the only simple method
This might help
http://apps.webofknowledge.com/full_record.do?product=WOS&search_mode=OneClickSearch&qid=15&SID=4EF98OGFiVVhAuwyT8Z&page=1&doc=9
Hi Patrica
This website was inaccessible. Anyway, thank you so much.
A study shows that initial chlorides can be removed by PbNO3 then followed by a final dose of AgSO4 to completely remove chlrides. No need to filter, but centrifuge and get supernatant for final COD determination.
Hello Ioannis. I read your paper. I have one comments.
1. The precipitation of mercuric chloride by adding mercuric sulfate.
Mercuric chloride is soluble in water. Then how can you precipitate it. I tried in my lab and found no precipitate in the solution. Can you please explain more about this more.
You can precipitate chloride ion by silver nitrate as silver chloride then separate it but AgNO3 has another interference (NO3) for COD Test. Therefore, another suggestion is using resin for chloride removal. it is called (styrene base cation exchange ion in silver) .
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