Investigation of a Low Cost, Stable and Efficient Adsorbent for the Fast Uptake of Cd (II) from Aqueous Media

Cadmium is considered one of the most dangerous and toxic metals, human carcinogenic and teratogen impacting lungs, liver, and kidney. Its allowed amount in drinking water is 5 ppb, according to the US Environmental Protection Agency (USAEPA). In the present study, cadmium was removed from wastewater using Ni-Mn nanoparticles loaded on carbon as adsorbents. The effect of the adsorption parameters, including contact time, temperature, initial metal ion concentration, adsorbent dosage, pH, and the effect of shaking speed, has been evaluated. The results indicated that maximum percentage removal of cadmium was observed at pH 6, at 25 ppm initial metal ion concentration, i.e., cadmium, at a temperature of 308 K, and optimum shaking speed was 150 rpm. At the same time, the adsorbent dosage was 0.1 g/100 mL. The contact time for the establishment of equilibrium was 40 minutes. The adsorption isotherm model, such as Freundlich and Langmuir, was applied to the experimental data, and it has been observed that equilibrium data fitted well with the Langmuir adsorption isotherm. In contrast, data did not show agreement with the Freundlich adsorption isotherm. The different kinetics models were studied, such as pseudo 1st order and pseudo 2nd order. It was determined that experimental data show significant agreement with the pseudo 2nd order kinetics. Thermodynamics studies of adsorption were performed, and the parameters such as Gibbs free-energy change (∆G), change in the enthalpy of solution (∆H), and change in disorders of the solution (∆S) were also calculated, which gives the idea of the exothermic and spontaneous nature of adsorption process. The SEM results revealed that the particles lie at 2 µm. The EDX analysis shows the composition of carbon, nickel, and manganese. The XRD analysis shows that the adsorbent is crystalline in nature and the crystal structure is monoclinic.