Table 1 Coded and actual levels for indpendent variable and levels.

From: Optimization of biochar preparation from the stem of Eichhornia crassipes using response surface methodology on adsorption of Cd2+

Variables

Symbol

Coded levels

−1

0

1

Heating time (h)

X1

1

2

3

Heating temperature( °C)

X2

300

400

500

Heating rate (°C/min)

X3

10

15

20

Back to article page