The range analysis was used to clarify the
significance levels of different influencing factors on the adsorption
capacity of Cr(VI) on LSAC. The K value for each level of a
parameter was the average of three values shown in Table 2, the
range value, R, for each factor was the difference between the
maximum and minimum value of the three levels, and the square of deviation (S) of three levels for each factor was also calculated.
[53,54] According to the results of range analysis and the square of
deviation, the significance sequence of the four investigated
influencing factors was obtained and the order was as follows: the
mass ratio of carbonized material to NaOH, carbonization
temperature, activation temperature and activation time. It can
be concluded that the mass ratio of carbonized material to NaOH
has significant influences on the adsorption capacity of Cr(VI) on
LSAC and the optimal condition is A2B3C1D2 (Exp. no. 6). Moreover,
two experiments were carried out at the optimal condition to
validate the results of the range analysis, and the equilibrium
adsorption capacity of Cr(VI) were 28.46 and 28.93 mg/g,
respectively, which meaning the range analysis is reliable.
Therefore, LSAC, prepared by Exp. no. 6 at a carbonized
material/NaOH ratio of 50%, carbonization temperature of
350 8C, activation time and activation temperature of 1.5 h and
600 8C, respectively, was chosen as the suitable for adsorbing
Cr(VI) throughout all the remaining adsorption experiments