Table 8.

The concentration of Zn in treated wastewater after RSM application in optimal conditions (pH = 10.75 ± 0.10, V Na₂CS₃ dose = 0.043 mL/L and time = 5, 10, 15 and 20 min—experimental model verification).

Parameter	Zn, mg/L after 5 Min	Zn, mg/L after 10 Min	Zn, mg/L after 15 Min	Zn, mg/L after 20 Min
Concentration of Zn, predicted	0.20	0.15	0.17	0.25
Concentration of Zn, experimental	0.15 ± 0.03	0.21 ± 0.03	0.20 ± 0.02	0.20 ± 0.02