Chemical Recycling of Expanded Polystyrene Waste: Synthesis of Novel Functional Polystyrene-Hydrazone Surface for Phenol Removal

Table 1

Levels of factors used in experimental design for the removal of phenol on PSH surface.

Factors	Coded levels
	−1	0	+1
Amount (mg), A (𝑋1)	10	55	100
Concentration (mgL^−1), 𝐵 (𝑋2)	5	30	55
pH, 𝐶 (𝑋3)	2	5.5	9
Time (min), 𝐷 (𝑋4)	10	95	180