Nitrate removal from wastewater by a novel co-biochar from guava seeds/beetroot peels-functionalized-Mg/Al double-layered hydroxide

Abstract

Increased concentration levels of nitrate in various water resources and supplies have alarmingly increased worldwide owing to severe pollution problems. The growing usage and implementation of nitrogenous fertilizers were identified as the main sources of such serious impact and contribution to the high nitrate levels in domestic wastewater. Therefore, the removal of nitrate pollutants from water using low-cost and eco-friendly materials and techniques is a major concern. Therefore, this study was designed to assemble and prepare a novel co-biochar-double-layered hydroxide nanocomposite (Gs-Bp@Mg/Al LDH) by co-pyrolysis of guava seeds and beetroot peels, followed by functionalization with MgAl double-layer hydroxide (LDH). Various techniques were employed to characterize the assembled composite, confirming its successful synthesis and loading of LDH layers on the surface of co-biochar. The nanocomposite was evaluated as a potential adsorbent for nitrate removal from wastewater using batch experiments. The results showed that the removal efficiency of nitrate using Gs-Bp biochar was 49.1 % at pH 6.0, whereas the corresponding value for Gs-Bp@Mg/Al LDH was 94.9 % at pH 5.0 for 5 mg L-1 after 30 min. The kinetics followed the pseudo-second order model, and the equilibrium condition was reached within 30 min. The adsorption isotherms were well-defined by Freundlich and Langmuir. Thermodynamic parameters indicate that the adsorption process is both spontaneous and exothermic. Furthermore, Gs-Bp@Mg/Al LDH demonstrated excellent removal efficiency for nitrate from different water samples, ranging from 86.2 % to 100 %. In addition, recyclability tests indicated the validity of Gs-Bp@Mg/Al LDH for potential nitrate removal for several cycles without a significant decline in adsorption performance. Overall, (Gs-Bp@Mg/Al LDH) holds promise as an effective adsorbent for the treatment of nitrate-contaminated wastewater.