Mesoporous Carbon from Optimized Date Stone Hydrochar by Catalytic Hydrothermal Carbonization Using Response Surface Methodology: Application to Dyes Adsorption

Table 1

Factors and their levels of the central composite design (CCD).

Variable name	Code	−1.68 (−α)	+1.68 (+α)	Coded low	Coded high	Mean	Std. deviation
A = temperature (°C)	X1	166.36	233	−1 ↔ 180.00	+1 ↔ 220.00	200.00	16.96
B = reaction time (min)	X2	40	140	−1 ↔ 60.00	+1 ↔ 120.00	90.00	25.43
C = catalyst dose (mg)	X3	13.30	21.70	−1 ↔ 15.00	+1 ↔ 20.00	17.50	2.12