Removal of Copper from Aqueous Solution Using Raw Cowpea Husk, And Cowpea Husk Coated With Zinc Oxide Nanoparticle Adsorbent

Abstract

Raw Cowpea husk(CPH), and Cowpea husk coated (CPHC) with nano Zinc oxide (ZnO) were used as adsorption media to remove Copper (Cu²⁺) from aqueous solutions. Functional groups, morphology, structure, and percentages of surfactants before and after adsorption were characterized through Fourier-transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). Several variables, including pH, connection time, dosage, initial concentrations, and temperature, were controlled to obtain the optimum condition. Thermodynamic studies, adsorption isotherm, and kinetics models were examined to describe and recognize the type of interactions involved. Resultantly, the best operation conditions were at pH 5, contact time of 210 min, 1 g/100ml of dosage, initial concentration of 30 mg/L, and a temperature of 45 °C. The removal percentage of Cu²⁺ under the optimum condition was 77% for CPH and 96% for CPHC. Thermodynamic analysis indicated that the removal efficiency was slightly increased with temperature depending on the positive value of Δ𝐻°, thus indicating that the adsorption phenomenon was endothermic. The Langmuir model fitted the study  (R² = 0.987) for CPH and(R² = 0.967) for CPHC, demonstrating that the adsorption sites were homogenous. The experimental results were best matched with the second-order kinetic model, implying that chemisorption was the primary process during the adsorption process.