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 m 2 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 ( q max ) 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 ( R L ), 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.