Mechanistic performance of polyaniline-substituted hexagonal boron nitride composite as a highly efficient adsorbent for the removal of phosphate, nitrate, and hexavalent chromium ions from an aqueous environment

In this study, we synthesized a novel 2D heterostructured composite material by substituting hexagonal boron nitride (h-BN) with polyaniline (Pani), h-BN@x%Pani, via an in situ chemical oxidative method. The h-BN@x%Pani (x = 1, 2, and 5% of aniline) can remove phosphate, nitrate, and hexavalent chromium (Cr(VI)) ions from aqueous solution, and h-BN is generally used as a supporting material because of its good stability and high specific surface area (263.68 m²/g). The physicochemical properties of the h-BN@x%Pani hybrid composite before and after adsorption of the aforementioned contaminants were investigated using various analytical techniques. After substitution of Pani onto h-BN, the surface charge density of the as-synthesized adsorbent was greatly improved, which is in good agreement with zeta-potential measurements. The adsorption mechanism of phosphate, nitrate, and Cr(VI) ions onto h-BN@x%Pani hybrid composite was mainly governed by electrostatic attraction followed by surface complexation and ion-exchange. Furthermore, the h-BN@x%Pani composite was regenerated with 0.1 M NaOH solution as a desorbing reagent without any significant loss of adsorption efficiency for five consecutive cycles. Because of their good removal behavior for phosphate, nitrate, and Cr(VI) ions, the synthesized h-BN@x%Pani hybrid composites are expected to become potential candidates in practical applications for water and wastewater remediation.