Adsorption of lead(II) ions using KOH-activated carbon derived from water hyacinth

Abstract

ABSTRACT. In this study, the adsorption of Pb(II) ions onto potassium hydroxide activated carbon derived from water hyacinth leaf (KOH-AC-WHL) is described. KOH-AC-WHL was characterized using FT-IR spectrometry. The adsorption kinetics and equilibrium were investigated using square wave anodic striping voltammetry (SWASV) for monitoring Pb(II) ions. The adsorption kinetics showed a better fit with the pseudo-second-order kinetics model with good linear correlation coefficients (R²) value of 0.999 compared to R² value of 0.760 for a pseudo-first-order kinetics. The Langmuir and Freundlich models were used to fit the adsorption experimental data. A better correlation with the Langmuir model was observed with R² value of 0.994 compared to the R² value of 0.986 for the Freundlich model. Hence, the maximum adsorption capacity of the adsorbent for Pb(II) ions was calculated from the Langmuir isotherm and found to be 206 mg/g. Thermodynamic parameters were determined and their values showed that the adsorption of Pb(II) ions on KOH-AC-WHL was spontaneous and endothermic. The adsorbent material effectively removed Pb(II) ions from 100 μg/L of Pb(II) simulated wastewater to the World Health Organization (WHO) permissible level of 10.0 μg/L within 30 min. The reusable efficiency of KOH-AC-WHL was found to be 73% after four consecutive cycles.

KEY WORDS: Lead(II) ions, Activated carbon, Water hyacinth, Adsorption

Bull. Chem. Soc. Ethiop. 2023, 37(6), 1369-1382.
DOI: https://dx.doi.org/10.4314/bcse.v37i6.6