Preparation and Characterization of Porous Carbon@ZnO-NPs for Organic Compounds Removal: Classical Adsorption Versus Ultrasound Assisted Adsorption

In this paper, the synthesis and characterization of porous carbon (PC) and porous carbon loaded ZnO nanoparticles (PC@ZnO) were investigated. The removal efficiency of Methylene Blue (MB) under ultrasound waves (UAA) and without ultrasound waves (SA) was studied considering the adsorbents dose, contact time, solution pH, temperature and initial dye concentration. Ultrasound irradiation have a positive effect on the removal efficiency of MB whereas ZnO nanoparticles incorporate in the surface of PC improve the regeneration efficiency of PC. PC@ZnO NPs shows high performance of MB removal using UAA, which was used for simultaneous removal of Crystal Violet (CV) and Congo Red (CR). The ultrasonic adsorption of CV/CR on PC@ZnO was found to be dependent on different parameters such as contact time, solution pH and initial dye concentration. The experimental results were found to follow the pseudo-second-order and Langmuir models. The adsorbed amount was found to be 64 mg g−1 (for CR) and 109 mg g−1 (for CV). Further, the effects of various parameters such as contact time, pH, initial dye concentration, and CV:CR ratio, were studied using central composite design coupled with response surface methodology. The data showed that the PC@ZnO has strong selective adsorption of CV dye in comparison to CR, and optimum conditions were found to be natural pH, 11.19 mg, (55:45%) of CV:CR ratio, 25 min and 30 mg L−1 at adsorption temperature T=25 °C ± 1. In these conditions, both dyes (CV and CR) are easily regenerated using HCl (0.1 M).