Adsorption of lead (Pb-II) using CaO-NPs synthesized by solgel process from hen eggshell: Response surface methodology for modeling, optimization and kinetic studies

Abstract

In this research study, the application of synthesized calcium oxide nanoparticles by sol-gel process from a waste resource of hen eggshells for the adsorption of lead ion from aqueous solutions was investigated. Characteristic behavior of the CaO-NPs like porosity, point of zero charges, Fourier transform infrared radiation spectroscopy, X-ray diffraction, specific surface area, thermal gravimetric analysis, and scanning electron microscopy was analyzed. X-ray diffraction discovered that the size of synthesized calcium oxide nanoparticles was 24.34 nm and the specific surface area was 77.4m2 /g by Sears method. The removal of divalent lead from aqueous solutions was optimized by using response surface methodology. The optimum percentage of lead removal (99.07%) resulted at initial concentration 75.46 ppm, pH 6.94, adsorbent dosage 0.838 g, and contact time 101.97 min. The experimental removal efficiency (98.86%) agreed very well with the predicted one (99.07%), showing the suitability of the model used and the success of response surface methodology in optimizing of removal of Pb (II) ions from aqueous solutions. The lead removal was well fitted into the Langmuir isotherm model with correlation coefficients of 0.9963. The adsorption kinetic data effectively fitted to the pseudo-first-order model with good correlation coefficients of 0.945. The pseudo-second-order model was the rate-limiting step in the lead (II) adsorption process with CaO NPs. From he above output we have conclude that, the calcium oxide nanoparticles prepared from eggshell have a good capacity for the removal of the lead from the aqueous solutions.