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<p>This study reports the green synthesis of <i>Piper betle</i>–derived zinc oxide nanoparticles (<i>p</i>ZnONPs) and evaluates their performance for Cr(III) removal, a persistent and often overlooked contaminant in dental wastewater. Phytochemicals present in <i>P. betle</i> leaf extract acted as natural reducing and capping agents, producing stable ZnONPs with nanometer-scale dimensions and surface functional groups favourable for metal ion adsorption. Comprehensive characterization using FTIR, UV–Vis spectroscopy, XRD, DLS, zeta potential analysis, TGA/DTG, and TEM–SAED confirmed the formation of spherical to quasi-spherical, polycrystalline ZnONPs with particle sizes ranging between 50 and 100&#xa0;nm, high colloidal stability (zeta potential − 43.6 mV), and strong thermal resilience. The <i>p</i>ZnONPs demonstrated excellent Cr(III) adsorption efficiency, achieving 96% removal at a dosage of 10&#xa0;mg and exhibiting a maximum Langmuir adsorption capacity of 123.46&#xa0;mg/g. Kinetic modelling revealed an outstanding fit to the pseudo-second-order model (R² = 0.9997), indicating that adsorption was governed by interactions between Cr(III) species and readily available surface-active sites. Isotherm analysis further showed strong agreement with the Langmuir model (R² = 0.9829), confirming monolayer, site-specific adsorption on a largely homogeneous surface. XPS evaluation revealed no detectable Cr peaks after adsorption, but consistent positive shifts in C 1s, O 1s, and Zn core levels provided clear evidence of Cr(III) interaction with the nanoparticle surface. These shifts suggested an adsorption mechanism dominated by electrostatic interactions, hydrogen bonding, and outer-sphere complexation, rather than covalent Cr–O–Zn bond formation. The <i>p</i>ZnONPs also demonstrated promising reusability, retaining &gt; 90% removal efficiency for two consecutive cycles and maintaining 75–80% efficiency after five cycles. Application to real dental wastewater further confirmed practical feasibility, achieving up to 90% Cr(III) removal despite competing ions and organic constituents. Overall, the findings establish <i>p</i>ZnONPs as an eco-friendly, efficient, and cost-effective nanoadsorbent for Cr(III) remediation in dental effluents. The study highlights their potential for decentralized wastewater treatment and broader environmental applications requiring sustainable heavy-metal removal technologies.</p>

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Green Synthesis of Piper betle-Derived ZnO Nanoparticles for Efficient Removal of Cr (III) Ions from Dental Wastewater

  • 期刊论文

  • 发表日期：

    2026年1月8日

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  • Divya Mathew,
  • N. M. Sudheep,
  • Jewel Benny Thomas,
  • Benny Thomas

摘要

This study reports the green synthesis of Piper betle–derived zinc oxide nanoparticles (pZnONPs) and evaluates their performance for Cr(III) removal, a persistent and often overlooked contaminant in dental wastewater. Phytochemicals present in P. betle leaf extract acted as natural reducing and capping agents, producing stable ZnONPs with nanometer-scale dimensions and surface functional groups favourable for metal ion adsorption. Comprehensive characterization using FTIR, UV–Vis spectroscopy, XRD, DLS, zeta potential analysis, TGA/DTG, and TEM–SAED confirmed the formation of spherical to quasi-spherical, polycrystalline ZnONPs with particle sizes ranging between 50 and 100 nm, high colloidal stability (zeta potential − 43.6 mV), and strong thermal resilience. The pZnONPs demonstrated excellent Cr(III) adsorption efficiency, achieving 96% removal at a dosage of 10 mg and exhibiting a maximum Langmuir adsorption capacity of 123.46 mg/g. Kinetic modelling revealed an outstanding fit to the pseudo-second-order model (R² = 0.9997), indicating that adsorption was governed by interactions between Cr(III) species and readily available surface-active sites. Isotherm analysis further showed strong agreement with the Langmuir model (R² = 0.9829), confirming monolayer, site-specific adsorption on a largely homogeneous surface. XPS evaluation revealed no detectable Cr peaks after adsorption, but consistent positive shifts in C 1s, O 1s, and Zn core levels provided clear evidence of Cr(III) interaction with the nanoparticle surface. These shifts suggested an adsorption mechanism dominated by electrostatic interactions, hydrogen bonding, and outer-sphere complexation, rather than covalent Cr–O–Zn bond formation. The pZnONPs also demonstrated promising reusability, retaining > 90% removal efficiency for two consecutive cycles and maintaining 75–80% efficiency after five cycles. Application to real dental wastewater further confirmed practical feasibility, achieving up to 90% Cr(III) removal despite competing ions and organic constituents. Overall, the findings establish pZnONPs as an eco-friendly, efficient, and cost-effective nanoadsorbent for Cr(III) remediation in dental effluents. The study highlights their potential for decentralized wastewater treatment and broader environmental applications requiring sustainable heavy-metal removal technologies.