Ultrasound-assisted adsorption of dyes and cadmium ion from aqueous solutions by ZnAl2O4 nanoparticles

Abstract

In this study, we investigated the process of removing heavy metal ions and dyes by ZnAl2O4 nanoparticles from an aqueous solution. ZnAl2O4 nanoparticles were characterized by various physicochemical techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM), and Brauer–Emmett–teller (BET). The parameters of solution pH, sonication time, adsorbent amount, Cd2+, AO, and MB concentrations were investigated under different conditions. We performed the process modeling by Box-Behnken design (BBD) based on response surface methodology (RSM). A second-order polynomial equation was proposed to remove the desired analytes. The high values of the R2adj> 98% and R2pred> 97% parameters indicated the accuracy of second-order polynomial equations for all three analytes. In optimal conditions (pH = 6 for Cd2+, pH = 7 for AO and MB dyes, Cd2+ concentration 20 mg L−1, adsorbent amount 55 mg, ultrasound time 17 min, concentration of AO and MB dyes 10 mg L−1) 92.78%, 97.73%, and 95.30% were removed from Cd2+, AO and MB, respectively. Interference studies showed that the presence of different ions did not considerably affect the removal of Cd2+, AO, and MB. Reusability studies were analyzed based on the number of adsorption-desorption cycles, and the results showed no significant reduction in ZnAl2O4 efficiency if ZnAl2O4 is reused up to 5 times. ZnAl2O4 nanoparticles were also used to remove Cd2+, AO, and MB from environmental and wastewater samples. The results showed that the above process could be used with appropriate and high efficiency to remove Cd2+, AO, and MB from environmental water samples.