Appendix1,2,3
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2022-10-05
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Appendix 1
COD was determined using potassium dichromate method
：
1.Chemical Reagents
1.1. Ammonium ferrous sulfate standard solution: dissolve 39.2g
(NH
4
)
2
Fe (SO
4
)
2
•6H
2
O in 20mL deionized water, add 20mL sulfuric acid,
and then transfer it into a 100mL volumetric flask and dilute them with
deionized water to the mark.
1.2 Digestion solution: weight 9.8g potassium dichromate, 25g
potassium aluminum sulfate and 5.0g ammonium molybdate and dissolve
them in 500mL deionized water. Add 200mL sulfuric acid and transfer
them to a 1000mL volumetric flask and dilute them with deionized water
to the mark.
1.3 Ag
2
SO
4
-H2 SO
4
catalyst: weight 8.8g Ag
2
SO
4
and dissolve it in
1000mL sulfuric acid
1.4 O-phenanthroline indicator: weight 0.695g FesO
4
• 7H
2
O and
1.4850g o-phenanthroline, dissolve them in 100mL deionized water, and
store in a brown bottle.
1.5 Masking agent: weight 10.0g HgS0
4
and dissolve it in 100mL
10% sulfuric acid.
2. Measurement
Put 3 mL of deionized water sample into 12 mL heating tube, add 1 mL of
masking agent, and then add 3 mL of digestion solution and 5 mL of
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