Pollutant adsorption is a surface process that can be used to remove organic pollutants from water.

$($i$)$ Discuss the main adsorbate characteristics that affect adsorption equilibria from water $(6)$

$($ii$)$ Describe the steps that are involved in the adsorption of a pollutant from solution to the adsorbent surface. Which of these steps are regarded as the rate$-$limiting$?(8)$

$($iii$)$ Discuss the main differences between granular activated carbon adsorption $($GAC$)$ and powdered activated carbon adsorption $($PAC$)$ with respect to $($a$)$ reasons for selecting one or the other $($b$)$ method of application $($c$)$ advantages and limitations$,($d$)$ dosage determination.