3.2. Effect of contact time and particle size
Three different particle sizes of untreated activated carbon,
i.e., 0.250, 0.149 and 0.074mm are utilized. It is presented in
Fig. 2 that sorption increases with contact time from the solution
under prescribed conditions (pH 5.8±0.5, temperature 30 ◦C,
shaking speed 160 rpm and initial metal concentration 30 mg/L)
and becomes nearly constant after 120 min. Sorption capacity of
untreated activated carbon is found to be maximum, 79.43, 76.8
and 70.19% for particle size 0.074, 0.149 and 0.250 mm, respectively,
as shown in Fig. 1. It is well established that the sorption is
related to available surface area and contact time hence the sample
with particle size 0.074mm has depicted maximum uptake
capacity towards lead.