Intensification of Azo Dye Removal Rate in the Presence of Immobilized TiO_𝟐 Nanoparticles and Inorganic Anions under UV-C Irradiation: Optimization by Response Surface Methodology

Table 2

Experimental ranges and levels of the independent test variables.

Variables	Ranges and levels
	−2	−1	0	+1	+2
NO3^− concentration (mM)	0	30	60	90	120
HCO3^− concentration (mM)	0	30	60	90	120
H2PO4^− concentration (mM)	0	30	60	90	120
Cl^− concentration (mM)	0	30	60	90	120