Effective removal of Cr (VI) ions using low-cost biomass leaves (Sambucus nigra L.) in aqueous solution

The tannery industries have become an important part of societal growth; however, these processes have produced huge volumes of effluents containing heavy metals, particularly Cr(VI) oxyanions. The study is crucial and cost-effective for reducing the chromium (VI) from industrial wastewater. In order to meet the sustainable development goal (SDG) objective 6.3, the capacity of Sambucus nigra L. to adsorb heavy metal is established with the purpose of eradicating hazardous chemical contamination and reducing pollution. In this study, discontinuous tests were carried out to determine the efficiency of Cr(VI) sorption on leaves of Sambucus nigra L. Adsorption factors such as pH, temperature, adsorbent dosage, and contact time were evaluated. At a dosage of 3 g/L and pH 2, an efficiency of 98.22% was achieved under favorable conditions. The equilibrium and kinetic models that best fitted the experimental data are non-linear Freundlich and; pseudo-second order, and intra-particle diffusion, respectively. The thermodynamic parameters of the adsorption process, including Gibbs free energy (ΔG⁰), enthalpy (ΔH⁰), and entropy (ΔS⁰), were measured at 291, 303, 323, and 343 K, indicating that the phenomena was spontaneous and endothermic. The chemical analyses and surface morphology of the adsorbent were analyzed using SEM (scanning electron microscopy), EDS (energy dispersive spectroscopy), FTIR (Fourier transform infra-red), XRD (X-ray diffraction), and ICP-OES (inductively coupled plasma optical-emission spectroscopy) techniques. The results showed that Sambucus nigra L. has a significant removal efficiency of Cr(VI) in the contaminated solutions, establishing adsorbent as a low cost, readily available, and environmentally friendly and ensuring its potential for industrial usage.