5, amount of adsorbate
per unit mass of adsorbent at time t (mg/g), removal percent was decreased for Hg(II) ions from 20 to 60AoC indicating exothermic nature of adsorption process.
Adsorption capacity of methylene blue (dye) and 4-chlorophenol were determined as function of adsorbate
initial concentration and adsorbent dosage.
0 g of the adsorbate
with deionized water in 1000 mL capacity standard volumetric flask and serial dilution was made to obtain other lower concentrations required .
The adsorption rate is known to be controlled by several factors corresponding to different processes including: (1) diffusion of the solute from the solution to the film surrounding the absorbent particle, (2) diffusion from the film toward the particle surface (external diffusion), (3) diffusion from the surface to the internal sites (surface or pore diffusion) and (4) uptake of the adsorbate
which can involve several reaction steps.
In the first step, adsorbate
moves through the solution to reach external surface of adsorbent by molecular diffusion (film or external diffusion).
The decrease in adsorption density with increasing temperature is likely due to the weakening of attractive forces between adsorbate
and the adsorbent.
In an ideal breakthrough curve it is assumed that removal of adsorbate
is complete in the early stages of operation.
After a certain period of time, the rate of adsorption decreases due to accumulation of adsorbate
in the vacant sites.
Langmuir adsorption equation refer q as the adsorption capacity of adsorbate
adsorbed onto activated carbon to form monolayer and b is the empirical constant related to the affinity of the binding site.
Certain factors alter adsorption capacity, such as: temperature, adsorbate
and adsorbant concentration, pH, contact surface, among others.
pH has been termed as the master variable controlling the surface charge of the adsorbent as well as degree of ionization and speciation of aqueous adsorbates
This was done to minimize photochemical reactions in the carbon columns once the adsorbates
were fed into it.
However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates
They reported that the ratio of these two species depended on adsorbates
, and that thiols were coordinately bound to the cations through the lone pair of sulphur atoms in both cases.
They combine the surface physical and chemical structure of activated carbons, the surface phenomenon at solid-gas and solid-liquid interfaces, and the activated carbon adsorption of organic and inorganic gaseous adsorbates
and solutes from solutions.