3.1. Effect of contact time
the amount of the adsorbed dye onto cotton fiber increases with time and, at some point in time, reaches a constant value beyond which no more is adsorbed from solution. At this point, the amount of dye being adsorbed onto cotton fiber is in a state of dynamic equilibrium with the amount of the dye desorbing from the fiber. The time required to attain this state of equilibrium is termed the equilibrium time, and the amount of dye adsorbed at the equilibrium time reflects the maximum adsorption capacity of the cotton fiber under those operating conditions
3.2. Effect of temperature
results in decrease in the adsorption, which may be attributed to decrease in dye molecule stability at higher temperatures. The increase in temperature would increase the mobility of the large dye ions as well as produce
a swelling effect with the internal structure of the fiber, thus enabling the large dye molecules to penetrate further. This may also be a result of an increase in the mobility of the dye molecule with an increase in their kinetic energy, and the enhanced rate of intraparticle diffusion of sorbate with the rise of temperature.
3.3 Effect of initial dyes concentrations
It can be proposed that an increase in the initial dye concentration leads to an increase in mass gradient between the solution and adsorbent (cotton fiber), and thus acts as a driving force for the transfer of dye molecules from bulk solution to the fiber surface. The increase in the proportional dye adsorption is attributed to the equilibrium shift during the adsorption process It is obvious that the dye fixation is related to dye molecule structure. Larger molecule usually means more intermolecular interaction due to van der Waals force between the dye and cotton fabric, contributed a great part in the dye fixation
Effect of Adsorbent Dosage
The variation in the adsorption capacity between the various concentrations of adsorbent is depending on surface area required for adsorption. With increasing adsorbent concentration more surface area is available for the adsorption due to increasing the active site of adsorbent. After some time the adsorption was affected due to equilibrium. The adsorption of dyes increased with the sorbent dosage and reached an equilibrium value after 10 g of sorbent dosage. When the biosolid was increased from 10 to 12 g, the ratio of dye sorbed to biomass (mg g-1) showed no significant change.