Where: [q.sub.eq] = adsorbed quantity (mg.[g.sup.-1]) for a given adsorbate
concentration (MB and phenol); [q.sub.m] = maximum adsorption capacity (mg.[g.sup.-1]); [C.sub.eq] = adsorbate
concentration after the equilibrium to be achieved (mg.[L.sup.-1]); and [K.sub.L] = Langmuir constant.
This reduction may also be because of variation in concentration gradient of adsorbate
and adsorbent .
Various parameters that influence adsorption including the effect of pH (pH 1 to pH 12), contact time (20-180 min), initial adsorbate
concentration (25 to 150 mg/L), and adsorbent dosage (0.63 to 10.63 g/L) were studied.
This meant that phenol interacted with itself and the adsorbates
, thus being a multilayer adsorption process, as was the case for the adsorption of lead ions .
AC was tested to determine its capacity for removal of adsorbate
from aqueous solution.
The adsorption entropy changes (DS) of both adsorbents are negative, which is an indication of the fact that the mobility of adsorbate
on the surface of adsorbents is being more restricted in comparison with those in solution.
At low adsorbate
concentration, it turns into Freundlich isotherm, while at high adsorbate
concentration, it reduces a monolayer adsorption capacity characteristic of Langmuir isotherm .
Furthermore, negative [DELTA]S[degrees] of the adsorption process shows that the organization of the adsorbate
at the solid/solution interface becomes less random.
Once the adsorbate
is attached on the site, no more adsorption takes place, showing that it is monolayer type of adsorption.
Adsorption capacities (g/g) First cycle Second cycle Third cycle 1 Chlorobenzene 10.12 10.06 10.01 2 DMSO 9.60 9.51 9.44 3 Xylene 8.92 8.89 8.82 4 Methanol 724 7.19 711 5 Toluene 700 6.94 6.95 TABLE 2: Contact angle measurements for silica aerogel with different solvents in water.
Based on the above analysis, the intensity ratio of the [v.sub.8a] aromatic-ring vibration modes in Figure 5 is 382 : 1, and the EF of the hollow silver spheres, estimated by using 4-MBA as the probing adsorbate
, reaches ~1.5 x [10.sup.6].
The methylene blue (MB) dye supplied by Sigma-Aldrich (M) Malaysia was used as an adsorbate
. The MB has a chemical formula of [C.sub.16][H.sub.18]Cl[N.sub.3]S x 3[H.sub.2]O with molecular weight of 373.9 g/mol.