Using chemically modified Ocimum tenuiflorum as an efficient and low-cost biosorbent for removing Congo red from aqueous solutions

Abstract

The powder of Ocimum tenuiflorum leaves (OtLP) was modified by ZnCl2, H2C2O4, or CuS. The modified powders were characterized and applied as adsorbents for the first time to adsorb Congo red (CR). The effects of the most potent experimental variables on the CR adsorption by the chosen adsorbent were examined. Kinetic, isotherm, and thermodynamic constants were investigated. The best adsorbent was discovered to be the powder modified by ZnCl2 and CuS, which removed 97.82% of the CR and had a pore size of 1349.0 Å, pore volume of 2.1211 cm³.g−1, and a 281.16 m2.g−1 surface area. This adsorption followed models of second order and Langmuir for its kinetics and isotherms, respectively. Thermodynamic analyses proved that this adsorption is both heat-absorbing and spontaneous. The high uptake capacities (625.000, 714.286, and 769.231 mg.g−1) obtained in this study prove that this adsorbent will gain a significant attention in the field of water decontamination.