Metals Bioaccumulation Mechanism in Neem Bark

Area of Science:

• Environmental Science
• Materials Science
• Biotechnology

Background:

• Non-living biomaterials derived from plant biomass offer sustainable solutions for environmental remediation.
• Neem (Azadirachta indica) bark is an abundant and underutilized resource with potential for metal bioaccumulation.

Purpose of the Study:

• To elucidate the bioaccumulation mechanism of metal ions onto neem bark biomaterial.
• To characterize the surface properties and identify functional groups responsible for metal sorption.
• To assess the potential of neem bark as a bioindicator and bioaccumulator for environmental metal monitoring.

Main Methods:

• Preparation of biomaterial from neem bark.
• Characterization using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD).
• Analysis of metal ion sorption capacities and Fourier transform infrared spectroscopy (FTIR) for functional group identification.

Main Results:

• Metals were bioaccumulated in the order Hg(2+) < Cd(2+) < Pb(2+) ≅ Cu(2+).
• Whewellite (CaC2O4·H2O) formation indicated calcium ions involved in ion exchange with metal cations.
• FTIR confirmed the role of functional groups in metal adsorption; anionic species (As, Cr) were not adsorbed due to electrostatic repulsion.

Conclusions:

• Neem bark biomaterial facilitates metal bioaccumulation primarily through ion exchange mechanisms involving carboxylate groups.
• The biomaterial's structural and chemical properties make it suitable for detecting and quantifying environmental metal contamination.
• Neem bark holds promise as a cost-effective and eco-friendly material for bioindication, bioaccumulation, and biomonitoring.