Adsorption kinetics, thermodynamic studies, and high performance of CdO cauliflower-like nanostructure on the removal of Congo red from aqueous solution

In this work, CdO cauliflower-like nanostructure synthesized by mechanochemical method was employed to evaluate the adsorption ability of Congo red (CR) from the aqueous solution for the first time. UV-visible absorption spectroscopy was used to record the adsorption behavior. This special structure composed of nanorods and tubes with the high contact sites and surface area of 104 m2 g−1 can be operated as a capable adsorbent to absorb the dye molecules via adsorption process. The adsorption capacity of this material (0.01 g) was studied in high concentrations of CR (50 to 300 mg L−1) and represented an excellent efficiency to eliminate this toxic dye. Maximum adsorption capacity (qmax) calculated using Langmuir isotherm model, at room temperature and neutral pH, was found to be 588.24 mg g−1. Electrostatic interactions were conceived as the main adsorption mechanism, and the calculated dimensionless separation factor (RL), 0.023, indicated a favorable adsorption process. The kinetic and thermodynamic parameters for this proceeding were evaluated and confirmed the high performance of the synthesized adsorbent.