Adsorption of Pb2+, Co2+, and Cd2+ from Aqueous Solution Using Nitric Acid Modified Kola Nut Husk Adsorbent

Abstract

The potential of nitric acid modified kola nut pod adsorbent (MKNP) in removing selected heavy metals such as lead (Pb²⁺⁾, cobalt (Co²⁺), and cadmium (Cd²⁺) ions from aqueous solution was investigated. FTIR spectra before and after the adsorption indicates the presence of functional groups such as hydroxyl and carboxylic acid which are responsible for its surface chemistry. The percentage removal largely depends on pH, contact time and temperature. The results showed that metal ions removal at optimum pH, contact time and temperature were: (Pb²⁺: 89.58, 97.04, 97.11%); (Co²⁺: 77.53, 75.17, 65.42%), and (Cd²⁺: 96.99, 97.06, 96.94%) respectively. The thermodynamic studies revealed that the enthalpy change was negative across the initial metal ion concentrations, indicating that the adsorption process was exothermic. The Gibb’s free energy change (∆G) values at all temperatures (298, 313, 328, 343 and 358K) were also negative, indicating that the adsorption process was spontaneous and feasible. Kinetics parameters obtained showed that pseudo-second order was obeyed throughout the adsorption process. In conclusion, from the favorability of the adsorption process, MKNP would be an efficient, eco-friendly and cheap adsorbent in removing toxic heavy metals ions from wastewater and industrial effluents.