Table 1 Levels of selected factors in experimental design.

From: Bacterial acidic agents-assisted multi-elemental (Ni, Co, and Li) leaching of used lithium-ion batteries at high pulp densities

Factor

Unit

Low axial

Low factorial

Center point

High factorial

High axial

A: Sulfur dosage (SD)

(g/l)

5

7.5

10

12.5

15

B: Inoculum size

(v/v)

2

4

6

8

10

C: Initial pH

–

1

1.5

2

2.5

3

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