Synthesis and characterization of Zn–Al LDHs/activated carbon composite and its adsorption properties for phosphate and nitrate ions in aqueous medium

Abstract

Phosphate and nitrate ions are emerging trace pollutants and have been perceived in groundwater, surface water, and water sources. In the present work, a layered double hydroxides (LDHs) of the binary composite Zn–Al LDHs wrapped into activated carbon (Banana bract) (BBAC@Zn–Al LDHs) composite was synthesized via co-precipitation method. The prepared adsorbent was evaluated for the removal performance of phosphate and nitrate ions from aqueous medium. The fabricated composite was examined by SEM, XRD, FTIR, TGA-DSC, EDAX with mapping images and BET techniques. The effects of adsorbent dosage, solution pH, shaking time, temperature and co-ions on phosphate and nitrate adsorption have been investigated. Kinetics of the adsorption process was studied using diffusion and reaction-based kinetic models. The equilibrium isotherm study was performed by Freundlich, Dubinin–Radushkevich and Langmuir isotherm models. BBAC@Zn–Al LDHs composite showed good reusability and stability until the five cycles but remained inactive after the seven cycles. The BBAC@Zn–Al LDHs composite and anions interacted via the following possible mechanisms: electrostatic attraction, surface complexation, and ion exchange. This study paved the new route for designing a novel LDHs wrapped porous carbon adsorbent and exposed that as an efficient and low-cost adsorbent to control the phosphate and nitrate pollution in water.