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

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