Figure 9: The fluctuation diagram of single factor.
3.3.4 Analysis of Interaction among Factors
The reaction surface analysis diagram is a three-
dimensional diagram composed of reaction values
and any experimental factors, showing the influence
of the other two variables on the test efficiency when
two of the factors A, B, C and D are at the
intermediate level. However, when the two factors
interact, the influence of one factor on the other
factor is different at different levels. The response
surface of this study basically presents an open form,
that is, with the increase of factor level, the removal
efficiency shows a trend from high to low. The
contour map is a curve formed on the lower surface
with the same factor value on the surface. The closer
the contour is to the circle, the smaller the
interaction between them. The closer the contour of
the ellipse is, the greater the interaction between the
two. The density of the contour line reflects the
factors affecting the removal efficiency. The denser
the contour, the greater the effect on the removal
efficiency.
The pairwise interaction between the factors is
shown in Figure10. The contour map of the
interaction between A and B is shown in
Figure10(a). The oval contour indicates that there is
interaction between A and B. The contour density of
A is higher than that of B, indicating that A has a
greater impact on the removal efficiency than B. The
response surface showed that the removal efficiency
increased rapidly with the increase of A, and then
begins to decline slowly when the dosage exceeds a
certain value (5-6g/L). With the increase of B, the
removal efficiency increases slowly and then
decreases slowly, and reaches the maximum when
the time during 56-72 min. The contour map of the
interaction between A and C is shown in
Figure10(b). The oval contour lines indicate that
there is interaction between A and C. The contour
density of A is higher than that of C, indicating that
the impact on removal efficiency of A is greater than
that of C. The response surface diagram shows that
the removal efficiency increases slowly with the
increase of A, and then decreases slowly when the
dosage exceeds a certain value (5-6g/L). With the
increase of C, the removal efficiency first increases
slowly and then decreases slowly, and reaches the
maximum when the temperature reaches 22-27℃.
The contour map of the interaction between A and D
is shown in Figure10(c). The oval contour line
indicates that there is interaction between A and D.
The contour density of A is greater than D,
indicating that A has a greater impact on the removal
efficiency than D. The response surface showed that
the removal efficiency increased slowly with the
increase of A level, and then begins to decline
slowly when the dosage exceeds a certain value (5-6
g/L). The removal efficiency increases slowly with
the increase of D, and begins to decline slowly when
pH exceeds a certain value (6.5-7.5). The contour
map of the interaction between B and C is shown in
Figure10(d). The contours of B and C are close to
circular, indicating that the interaction between B
and C is not obvious. The density of B is greater
than C, indicating that the effect of B on adsorption
is greater than C. The response surface showed that
the removal efficiency increased slowly with the
increase of B, and then begins to decrease slowly
when the time exceeds a certain value (60-70min).
With the increase of C, the removal efficiency
increases slowly and then decreases gradually, and it
reaches the maximum when the temperature reaches
22-27℃. The contour map of the interaction
between B and C is shown in Figure10(e). The oval
contour indicates that there is interaction between B
and D. The contour thickness of B is greater than D,
indicating that B has a greater impact on the removal
efficiency than D. The reaction surface showed that
the removal efficiency increased rapidly with the
increase of B, and then decreased slowly after the
time exceeding a certain value (60-70min). The
removal efficiency increased rapidly with the
increase of D, and then begins to decline slowly
when pH exceeds a certain value (6.5-7.5). The
contour map of the interaction between C and D is
shown in Figure10(f). The contour lines of C and D
are close to circular, indicating that the interaction
between C and D is not obvious. The contour line
thickness of D is greater than C, indicating that D
has a greater impact on the removal efficiency than