Eco-friendly arginine-doped polyaniline@Olive Stones composite for high-performance adsorption of Cr (VI) from aqueous solutions

Hexavalent chromium (Cr(VI)) is a highly toxic and carcinogenic contaminant commonly encountered in industrial effluents, posing significant risks to both environmental and human health. In this context, the novel biocomposite material (Arg-PANI@OS) was prepared via a facile chemical oxidative polymerization route, in which aniline was polymerized onto the surface of olive stone material in the presence of arginine as a functionalizing agent. To understand the material's properties, a range of characterization techniques was employed, including Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, and Scanning electron microscopy. In addition, the adsorption performance of the material toward Cr(VI), from water under controlled conditions was investigated. The results showed that the adsorption of Cr(VI) was significantly affected by several physicochemical parameters. Under the optimum conditions of pH 2.0, adsorbent dose of 0.5 g·L⁻¹ , contact time of 1 h, and temperature of 298 K, the material achieved a maximum Cr(VI) removal efficiency of 96.8%. In addition, the adsorption process followed pseudo-second-order kinetics, and the equilibrium data fitted well with the Langmuir isotherm model. Furthermore, the material was reusable over five adsorption–desorption cycles using NaOH as a desorbing eluent, although the removal efficiency decreased to 62% in the fifth cycle. These findings demonstrate that Arg-PANI@OS is a promising and efficient biocomposite for the removal of Cr(VI) from aqueous media. • A new bio-composite compound has been developed using olive stones, polyaniline, and arginine, termed Arg-PANI@OS. • The specialized compound was found to have impressive adsorption ability and specificity in the elimination of hexavalent chromium Cr(VI) ions from polluted water systems. • The adsorption mechanism was largely controlled by the electrostatic interaction sites of the composite material with the ions of Cr (VI). • The performance of the composite material was tested and found effective in the removal of Cr (VI) ions even under large-scale water purification operations.