In order to develop an adsorption process, a number of factors
influencing the process such as pH, Cr(VI) concentration, adsorbent
dose and temperature are to be studied. But the studying of the each
and every factor is quite tedious and time consuming. Thus, a factorial
design can minimize the above difficulties by optimizing all
the affecting parameters collectively at a time [25]. Factorial design
is employed to reduce the total number of experiments in order
to achieve the best overall optimization of the process [26–28].
The design determines the effect of each factor on response as
well as how the effect of each factor varies with the change in
level of the other factors [29]. Interaction effects of different factors
could be attained using design of experiments only [26,28].
Factorial design comprises the greater precision in estimating the
overall main factor effects and interactions of different factors. In
full factorial design every setting of every factor appears with every
setting of every other factor. Factorial designs are strong candidates
in examining treatment variations. Instead of conducting a series
of independent studies we can combine these studies into one. A
common experimental design is one with all input factors set at
two-levels each. These levels are called ‘high’ and ‘low’ or ‘+1’ and
‘−1’ respectively. If there are k factors each at two-levels, a full
factorial design has 2k runs.
In the present study, four-factor two-level full factorial design
(24 runs) was used for the modeling of adsorption process.