The plant parts of Pongamia pinnata (also known as Milletia pinnata) like pods, leaves, seeds and bark, are recognized as excellent adsorbents for the removal of heavy metal ions and dyes from aqueous solutions. Pongamia has been classified as an excluder and also as a hyperaccumulator depending on the contaminant. It shows greater efficiencies for the removal of heavy metals like Ni(II), Co(II), Cr(VI), Zn(II), and a wide variety of dyes like Methylene Blue, Malachite green, Grey BL, Rhodamine B. This review paper aims to analyse and summarize the existing research works on heavy metal-bearing pollutants uptake by raw, chemically modified, activated and carbonised Pongamia pinnata (PP) plant parts. Reports reveal that uniform particle sizes of the adsorbent were achieved using mesh sizes ranging from less than 2 mm to 200 mm,100–300 μm and 75–150 nm, depending on the need and availability. Many researchers have reported the use of chemical reagents like H2O2, H2SO4. H3PO4, HCl, KOH, NaOH, and ZnCl2 for the surface activation of pulverised plant parts. The characterization studies of the PP adsorbent were carried out through pore structure analysis, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy. Batch adsorption process was the widely used technique among all the other available methods, as it is simple and economically viable, as reported by researchers. The effect of various controlling parameters like pH, dosage variation, effect of contact time, and initial concentration was studied using this batch adsorption technique. As reported by the various researchers, from the Batch adsorption studies the removal efficiency of heavy metals and dyes exceeds 90% with Pongamia pinnata plant parts as an adsorbent. The sorption mechanism and the rate of the adsorption process of PP - metal ion/dye system were analysed using Pseudo-first-order, Second-order kinetics, Elovich and intraparticle diffusion models. Reports also reveal the use of various adsorption isotherm models employed in the study of the adsorbent-adsorbate system. Among the chemically activated plant parts of PP, phosphoric acid-activated Pongamia pinnata pod shows greater specific surface area of about 935.02 m2/g enabling a higher uptake of metal ions. This review develops a theoretical and methodological approach to support future research and applications of Pongamia pinnata in environmental remediation.

Pongamia pinnata as an Adsorbent in the Sequestration of Heavy Metal Ions and Dyes – A Review Study

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发表日期：

2026年4月22日

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Rogini G,
Gohulavani G

摘要

The plant parts of Pongamia pinnata (also known as Milletia pinnata) like pods, leaves, seeds and bark, are recognized as excellent adsorbents for the removal of heavy metal ions and dyes from aqueous solutions. Pongamia has been classified as an excluder and also as a hyperaccumulator depending on the contaminant. It shows greater efficiencies for the removal of heavy metals like Ni(II), Co(II), Cr(VI), Zn(II), and a wide variety of dyes like Methylene Blue, Malachite green, Grey BL, Rhodamine B. This review paper aims to analyse and summarize the existing research works on heavy metal-bearing pollutants uptake by raw, chemically modified, activated and carbonised Pongamia pinnata (PP) plant parts. Reports reveal that uniform particle sizes of the adsorbent were achieved using mesh sizes ranging from less than 2 mm to 200 mm,100–300 μm and 75–150 nm, depending on the need and availability. Many researchers have reported the use of chemical reagents like H₂O₂, H₂SO₄. H₃PO₄, HCl, KOH, NaOH, and ZnCl₂ for the surface activation of pulverised plant parts. The characterization studies of the PP adsorbent were carried out through pore structure analysis, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy. Batch adsorption process was the widely used technique among all the other available methods, as it is simple and economically viable, as reported by researchers. The effect of various controlling parameters like pH, dosage variation, effect of contact time, and initial concentration was studied using this batch adsorption technique. As reported by the various researchers, from the Batch adsorption studies the removal efficiency of heavy metals and dyes exceeds 90% with Pongamia pinnata plant parts as an adsorbent. The sorption mechanism and the rate of the adsorption process of PP - metal ion/dye system were analysed using Pseudo-first-order, Second-order kinetics, Elovich and intraparticle diffusion models. Reports also reveal the use of various adsorption isotherm models employed in the study of the adsorbent-adsorbate system. Among the chemically activated plant parts of PP, phosphoric acid-activated Pongamia pinnata pod shows greater specific surface area of about 935.02 m²/g enabling a higher uptake of metal ions. This review develops a theoretical and methodological approach to support future research and applications of Pongamia pinnata in environmental remediation.