Effective Removal of Cd(II) and Pb(II) from Aqueous Solution by Synthesized Palladium Nanoparticles Using Spent PdCl2 Catalyst: Experimental Design and Optimization

Environmental considerations have motivated the present study to develop and to investigate Cd(II) and Pb(II) removal process from aqueous solutions. This was carried out through the application of ultrasound onto sodium dodecyl sulfate coated palladium nanoparticles (SDSPdNPs). The recovered palladium chloride of petroleum’s spent catalyst used as a precursor for the nanoparticle synthesis. The size, morphology and the structure of the synthesized adsorbent has been fully characterized using transmission electronic microscope (TEM), scanning electron microscope (SEM), and X-ray diffractometer (XRD) spectroscopy measurements. The mean diameter of the SDSPdNPs as typically 23.4 nm for a generally homogeneous size regardless of agglomeration is reported. Statistically designed experiments with the support of central composite design (CCP) and response surface methodology (RSM) were applied to evaluate the main physiochemical parameters that would affect the interactions among the variables with the aim to define optimization criteria for the adsorption efficiency with respect to both of the metal ions. The optimized condition is reported as follows: pH: 4.2; contact time: 92 min; adsorbent dosage: 65 mg. Further to the above findings, the experimental equilibrium data efficiency fitted the Langmuir model with a high adsorption capacity of 323.14 and 207.81 mg/g-1 in the case of Pb(II) and Cd(II), respectively.