Hen Feather: A Remarkable Adsorbent for Dye Removal - Green Chemistry for Dyes Removal from Wastewater - page 421

It is a well-known fact that the adsorption of any chemical substance
depends upon its protonation ability in the working solution, hence the
adsorption is always dependent upon the pH of the dye solution. The
effect of the concentration of the dye solution and contact time of adsor-
bate and adsorbent alter the rate of transference of the adsorbate to the
exterior of the adsorbent; therefore concentration and contact time studies
are helpful in observing the dynamics of the adsorbate material. Moreover,
study of the amount of adsorbent is also of utmost importance as adsorp-
tion depends upon the amount of the adsorbent material in the solution.
During the present study, adsorption of the dyes over Hen Feather is car-
ried out under different conditions and a comparative analysis supported
by figures and tables has been made. The entire test performed during the
course of the studies is helpful in evaluating and designing isothermal and
kinetic aspects of the adsorption process and in understanding the basic
adsorption characteristics.

11.4.1 Experimental Methodology

During the preliminary investigations, batch technique, i.e., finite bath
systems, has been employed. The batch technique involves a continuous
interaction between the dye particles with adsorbent particles at predeter-
mined conditions in the reaction vessel [72]. Experimentation has been
carried out by taking 25 mL of the dye solution of a particular concentra-
tion in a series of 100 mL volumetric flasks. An appropriate amount of the
adsorbent was then added to these flasks and intermittent uniform shak-
ing was carried out by a mechanical shaker for a homogeneous mixing.
Throughout the studies, the temperature was kept constant at 30, 40 or
50 C using a water bath. After a fixed period of time these solutions were
filtered using Whatman filter paper (No. 41) and analyzed spectrophotom-
eterically for measuring the dye uptake. All the analytical grade reagents
and chemicals (hydrogen peroxide, sodium hydroxide, hydrochloric acid,
etc.) used in these studies were procured from M/s Merck.

11.4.1.1 Effect of pH

The pH of the dye solution plays an important role in the adsorption of any
adsorbate. Batch studies have been carried out for the adsorption of all the
eight dyes over the adsorbents by varying the pH over a wide pH range from
acidic to alkaline region. The pH of each test solution was adjusted using
NaOH and HCl solutions. Each solution was homogeneously mixed for about
24 hours and then the uptake of the dye was measured. All pH measurements