Investigating the efficiency of hydrochar nanocomposite in removing cadmium from aqueous solution using response surface

This study aims to synthesize and investigate the effect of hydrochar modified with zero-valence zinc nanoparticles and stabilized with sodium citrate (HC@nZVZ@SC) on removing cadmium from an aqueous solution under the influence of factors affecting the removal. For this purpose, the effective factors on removal include adsorbent dose, contact time, initial concentration, and pH using the response surface method (RSM) based on the central cube design (CCD) to optimize the removal of cadmium (Cd) ions by HC@nZVZ@SC from aqueous solutions. Also, SEM-EDX, FTIR, and XRD methods were used to check the successful loading of zero-valent zinc nanoparticles on hydrochar. SEM-EDX, FTIR, and XRD results showed that zero valence zinc nanoparticles were successfully loaded on hydrochar. The low P value (<0.0001) and high R2 (0.98) showed that the prediction of cadmium removal from aqueous solution by the adsorbent was done well and with high accuracy by the CCD model. The results showed that the optimal removal of cadmium was achieved at pH = 7, the initial concentration was 75 mg/L, the contact time was 60 minutes, and the adsorbent dose was 1.5 g/L, which was 91.35%. In general, the results of this study showed that hydrochar modified with zero-valent zinc nanoparticles and stabilized with sodium citrate can be used as an inexpensive and high-efficiency adsorbent in removing heavy metals from wastewater. Also, the central cube design should be used as an efficient and low-cost method in modeling and optimizing the removal of pollutants from aqueous solution.