Environmental Engineering Reference
In-Depth Information
adsorbent dosage decreases, the uptake capacity is enhanced [65].
Accordingly, an enhanced methylene blue uptake of 281 mg.g -1 for date pit
with a surface area of 80.5 m 2 .g -1 was obtained when the adsorbent dosage,
pH and particle size were 1 g.L -1 , 4 and 125-300 μm. Under the same
experimental conditions, when the adsorbent particle size increased to
500-710 μm, the uptake capacity was dramatically reduced to 131 mg.g -1
(see Figure  5.11). They proposed the hydrogen bonding mechanism
between the hydroxyl groups of the adsorbent and nitrogen and sulfur
atoms of adsorbate, as illustrated in Figure 5.12, which was verified by the
shift of relevant FTIR peaks. Furthermore, lack of desorption of methylene
blue molecules from the surface of the adsorbent confirmed the strong
hydrogen bonds between the dye molecules and the adsorbent. Banat et al.
[83] studied the adsorption of methylene blue by raw and modified date
pit. When the particle size was 125-212 μm, the adsorption capacity of raw
date pit was determined to be 80.3 mg.g -1 . Different adsorption capacities
from the abovementioned literature could be because of the different
adsorbent dosage (5 g.L -1 ) used in this work. The decrease in the adsorp-
tion capacity by increasing the particle size was attributed to the lower sur-
face area of the adsorbent at larger particle size. Raising the solution
temperature resulted in a decrease in the adsorption capacity due to the
tendency of the dye molecules to escape from the adsorbent pores and sur-
face with an increase in the solution. They also converted the date pits to
Figure 5.11 Effect of particle size on the methylene blue adsorption capacity of date
pit-based activated carbon [82].
Search WWH ::




Custom Search