Table 2.

Results of various research regarding the effect of initial solution pH, where E is the efficiency of the adsorption process and E_max is the highest efficiency calculated in the specific article at a given condition.

Dyestuff	Adsorbent	Dyes Ionic Nature	pH	Observations: with the Increase (↑) of pH	Reference
Direct Red 5B	spent mushroom waste	anionic	2 to 10	E% ↓; Emax_pH=2 = 95%	[178]
Direct Black 22		anionic	2 to 10	E% ↓; Emax_pH=2 = 98%	[178]
Direct Black 71		anionic	2 to 10	E% ↓; Emax_pH=2 = 95%	[178]
Reactive Black 5		anionic	2 to 10	E% ↓; Emax_pH=2 = 96%	[178]
Congo Red	powdered activated carbon: rubber seed	anionic	4 to 11	E% ↓	[179]
	powdered activated carbon: rubber seed shells		4 to 11	E% ↓	[179]
Methylene Blue	powdered activated carbon: rubber seed	cationic	4 to 11	E% ↑	[179]
	powdered activated carbon: rubber seed shells		4 to 11	E% ↑	[179]
Eriochrome Black T	powdered vegetables wastes	anionic	2 to 10	E% ↓; 50.65 to 4.01%	[180]
	calcined vegetables wastes		2 to 10	E% ↓; 68.87 to 31.23%	[180]
Methyl Orange	natural olive stone	anionic	2 to 12	q (mg/g) ↓; 26.4 to 3.3 mg/g	[158]
	olive stone activated carbons		2 to 12	q (mg/g) ↓; 120 to 15 mg/g	[158]
Methylene Blue	natural olive stone	cationic	2 to 12	q (mg/g) ↑; 18 to 120 mg/g	[158]
	olive stone activated carbons		2 to 12	q (mg/g) ↑	[158]
Reactive Orange 16	carbon from Phyllanthus reticulatus	anionic	2 to 11	q (mg/g) ↓	[181]
Cationic Red X-5GN	ceramic	cationic	2 to 10	E% ↑	[182]
Cationic Blue X-GRRL		cationic	2 to 10	E% ↑	[182]
Methylene Blue	activated carbon/cellulose biocomposite films	cationic	3 to 11	q (mg/g) ↑; 50.54 to 60.48 mg/g	[183]
Eriochrome Black T	almond shell	anionic	2 to 11	q (mg/g) ↓	[184]
Malachite Green		cationic	2 to 11	q (mg/g) ↑	[184]
Basic Yellow 37	bast fibers: ramie	cationic	2 to 12	E% ↑; Emax_pH=12 = 91%	[185]
	bast fibers: flax	cationic	2 to 12	E% ↑; Emax_pH=12 = 88%	[185]
	bast fibers: kenaf	cationic	2 to 12	E% ↑; Emax_pH=12 = 78%	[185]
Remazol Brilliant Violet	Trichoderma viride	anionic	4 to 9	E% ↓; 79.05 to 50.25%	[186]
Congo Red	eggshell powder	anionic	2 to 10	E% ↓; 98.71 to 93.17%	[133]
Bromphenol Blue		anionic	2 to 10	E% ↓; 67.61 to 1.2%	[133]
Methylene Blue		cationic	2 to 10	E% ↑; 14.8 to 75.1%	[133]
Malachite Green		cationic	2 to 10	E% ↑; 89.95 to 97.92%	[133]