Heavy metals binding properties of esterified lemon.

Area of Science:

• Environmental Chemistry
• Materials Science
• Green Chemistry

Background:

• Heavy metal contamination in water poses significant environmental and health risks.
• Developing cost-effective and sustainable sorbent materials is crucial for effective remediation.
• Agricultural waste offers a potential source for novel adsorbent materials.

Purpose of the Study:

• To investigate the sorption of various heavy metal ions (Cd2+, Cr3+, Cu2+, Ni2+, Pb2+, Zn2+) using a carboxyl group-rich material derived from lemon waste.
• To determine the influence of pH on sorption efficiency and elucidate the sorption kinetics and isotherms.
• To analyze the thermodynamic parameters and identify the primary mechanism of heavy metal removal.

Main Methods:

• Batch sorption experiments were conducted to study the adsorption of Cd2+, Cr3+, Cu2+, Ni2+, Pb2+, and Zn2+.
• Sorption kinetics were analyzed using the pseudo-second-order model.
• Sorption equilibrium data were fitted to the Langmuir and Dubinin-Radushkevich isotherms.
• Thermodynamic parameters (ΔG°, ΔH°) were calculated to understand the sorption mechanism.

Main Results:

• Sorption capacity was highly dependent on pH.
• Equilibrium was reached within 30-240 minutes, following pseudo-second-order kinetics.
• The Langmuir isotherm accurately described the data, with a metal binding capacity order of Pb2+>Cu2+>Ni2+>Cd2+>Zn2+>Cr3+.
• Ion exchange was identified as the primary sorption mechanism, with significant contribution from physical adsorption.

Conclusions:

• Lemon-derived carboxyl-rich material is an effective sorbent for removing multiple heavy metal ions from aqueous solutions.
• The sorption process is spontaneous and exothermic, primarily driven by ion exchange.
• This study highlights the potential of utilizing citrus waste for developing sustainable environmental remediation technologies.