Nonlinear kinetics, isotherms, and thermodynamic approach in the carcinogenic ions elimination by Mn2.7Al0.3O4 sorbent

Alundum was integrated into hausmannite to synthesize a nano bimetallic oxide adsorbent Mn_2.7Al_0.3O_4, for exploring its synergistic effect on the adsorption of carcinogenic ions. The characterization of Mn_2.7Al_0.3O₄ revealed that the powder X-ray diffractogram confirmed the tetragonal structure corresponding to JCPDS No. 24-0734, and a platelet shape from the scanning electron microscopy (SEM) images. The Brunauer-Emmett-Teller (BET) studies disclosed a Type-IV isotherm with a H₃ hysteresis loop, indicating a mesoporous structure of 1.968 m²/g surface area and 35.8 nm average pore diameter. The uptake mechanism of the carcinogenic ions onto the Mn_2.7Al_0.3O₄ surface pronounced that adsorption followed pseudo-second-order kinetics. The adsorption capacity for Cd(II) ions was 174.6 mg/g and 75.4 mg/g for Pb(II) ions from the best fit Langmuir and the Sips models, which were authenticated by R², RSS,ARE, and χ² of the statistical functions, and close to the experimental results. The thermodynamic investigations announced that Cd (II) and Pb (II) ions adsorption was a spontaneous and exothermic process with a free energy change of -5.4 kJ ̸mol and ̶̶ 0.193 kJ/mol at 303 K. High adsorption capacity and easy recovery of adsorbent implied to use it for the carcinogenic ions adsorption in any aqueous stream.