Table 8.

Comparison of different adsorbents for OTC adsorption.

Adsorbents	Adsorption conditions	Adsorption capacity (mg/g)	References
Barley wastes activated carbon (BW-AC)	pH 8.25, adsorbent dosage 162.5 mg/L, initial concentration 62.5 mg/L, temperature 25°C	500	This study
Uncalcined nanohydroxyapatite (HA-uc)	pH 8, adsorbent dosage 2000 mg/L, initial concentration 50 mg/L, temperature 20°C	291	72
Multiwalled carbon nanotubes (MWNT10)	pH 7, adsorbent dosage 25,000 mg/L, initial concentration 2.5 mg/L, temperature 23°C	190	73
Surfactant-modified alumina (SMA)	pH 4, adsorbent dosage 25,000 mg/L, initial concentration 10−4 M, temperature 25°C	143	74
Magnetic microspheres with bimetal oxide shell (Mag@ZnO–Co3O4)	pH 7, adsorbent dosage 250 mg/L, initial concentration of 10 mg/L, temperature 25°C	128	75