[ADSORPTION]

Hello,
I'm currently studing the adsorption of pesticide Carbaryl on a support and i have difficulty interpret my result "effect of pH"
That's why I need your help.
Results:
- When the pH of the solution passe from 2 to 12 the percentage removal of the pesticide Carbaryl has increased from 62.6% to 87.8%.
- We determined the pHpzc of our adsorbent and it is 8.4 (meaning that the surface of the adsorbing member was positively charged at pH below 8.4 and negatively charged at a pH greater than 8.4).

Therefore the adsorption at a pH below 8.4 is considered to take place through the aromatic ring of the pesticide and also by means of electrostatic attraction phenomenon between the high negative charge associated with the carboxyl group of the pesticide and the surface positive charge of ABM.

My concern is to interpret the part or pH is above 8.4 and also why adsrption increases at pH between 2 and 8.4

You will find enclosed the results I found
Thank you and have good day.