Nitrate removal from aqueous solution using watermelon rind derived biochar-supported ZrO2 nanomaterial: Synthesis, characterization, and mechanism
Huy Hoang Phan Quang, Kiet Tuan Phan, Phong Dinh Lam Ta, Nga Thi Dinh, Taghrid S. Alomar, Najla AlMasoud, Chao‐Wei Huang, Ankush Chauhan, Van‐Huy Nguyen
Abstract
Recently, biochar has attracted tremendous research interest for environmental applications. In this study, biochar-derived watermelon rind (WM) was produced via optimal pyrolysis at 500 °C for 2 h, and then improved the adsorption capacity by Zirconium oxide nanoparticles (ZrO2 NPs). The WM@ZrO2 was characterized using X-ray diffraction (XRD), Scanning electron microscopic - Energy-dispersive X-ray spectroscopy (SEM-EDS), and Fourier transform infrared (FTIR). The adsorptive capacities of synthesized ZrO2 NPs were investigated for nitrate as a function of pH, adsorbent dosage, contact time, initial adsorbate concentration, and pyrolysis temperature in the batch experiment. The results showed that a Langmuir isotherm and a pseudo-second-order kinetics model were the best-fit for experimental nitrate data in its non-linear form as correlation coefficients (R2) were 0.985 and 0.998, respectively. The maximum adsorption capacity for the Langmuir isotherm model was 15.196 mg g−1. The proposed mechanism, including electrostatic attraction and ligand exchange, played a dominant role in nitrate adsorption. After testing with the real domestic wastewater, the removal of nitrate for WM@ZrO2 was achieved at 78 %, which was equivalent to the adsorption capacity of 8.1 mg g−1 of adsorbent. Overall, the WM@ZrO2 is proposed as a promising, effective, and environmentally friendly adsorbent in removing nitrate from an aqueous solution.