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so basically I did my experiment which is the title. This is my procedure and results:

  1. Make 0.05M CuSO4
  2. pipette 50ml CuSO4
  3. change to respective pH values using HCl
  4. Add 2g of oven-dried banana peels
  5. wait for half an hour
  6. Filter the solution into 100ml volumetric flask
  7. add 5ml of 2M HCl to change all replicates to approx. pH 1
  8. top up to 100ml mark using deionized water
  9. mix well
  10. put solutions into cuvettes and place the into the UV-vis spectrometer to measure absorbance
  11. compare it with the calibration curve to determine concentration

my 入max was 811. For those wondering why I made all the replicate the same pH after filtration, it was so that the pH at the end would not affect the absorption value, because I found out that pH changes the colour of the solution.

results: enter image description here edit: so the first reading is a blank, the 2nd reading is the absorbance of the pH 2 solution after it has been made to pH 1, the 3rd reading is the absorbance of the pH 2.5 solution after it has been made to pH 1, the other readings are for pH 3,3.5 and 4 (in order). The K*abs value doesn't matter.

enter image description here calibration curve:

enter image description here enter image description here

Does this look right? Cus I can't find any research papers that do this. The ones that I found do pH 2,3,4,5,6 and use extremely small concentrations of CuSO4, something like 0.0002M. Even if u assume the trend will be the same, my results don't follow the same trend, which is that the concentration of CuSO4 left in the solution after the experiment decreases as pH increases. Basically it means that at a higher pH, the banana peels can adsorb more Cu2+ ions.

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    $\begingroup$ You do not give us enough information. For example, the first image reports 6 absorbance measurements, 1 to 6. But are they related to the same sample ? Are they related to different samples ? What are their meanings ? What should we do with theses values ? What is the meaning of K*Abs being always zero in this image ? Why is there no information about pH ? $\endgroup$
    – Maurice
    Sep 3 '20 at 14:02
  • $\begingroup$ ahh ok. I'll put more info $\endgroup$
    – prata
    Sep 3 '20 at 14:53
  • $\begingroup$ @Maurice I added some explanation below the first picture. To ans ur qn about what to do with those values, it is in steps 10 and 11 $\endgroup$
    – prata
    Sep 3 '20 at 15:01
  • $\begingroup$ I would say that the absorbance does not depend on the pH value, and that the unknown sample has a concentration of 0.02 (unit unknown) $\endgroup$
    – Maurice
    Sep 3 '20 at 15:22
  • $\begingroup$ @Maurice that's not really what I'm asking. I want to know if the results look ok? cus i found this journal that says my trend (in the excel table) should continue going down. geomatejournal.com/sites/default/files/articles/… $\endgroup$
    – prata
    Sep 4 '20 at 2:36

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