Biosorption of Pb(II) ions from aqueous solution by cow hooves (CHs) was investigated as a function of initial pH, contact time, and biosorbent dosage through batch studies. Equilibrium experiments were performed at three different temperatures (298, 308, and 318？K) using initial Pb2+ concentration ranging from 15 to 100？mgg？1. This study revealed that maximum uptake (96.2% removal) of Pb2+ took place within 30 minutes of agitation, and the process was brought to equilibrium within 60 minutes of equilibration. The equilibrium data were modelled using Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. The Langmuir isotherm model fitted the data best at all temperatures considered. The Lagergren second-order kinetic model fitted the biosorption process better than the first-order model. The negative values obtained for both Gibb’s free energy change and enthalpy change are an indication of the spontaneous and exothermic nature of the sorption of Pb2+ onto CH. A study of the FTIR spectral obtained before and after Pb2+ sorption showed that carbonyl, hydroxyl, amino, and carboxyl groups were involved in the sorption process. 1. Introduction The presence of heavy metals in the environment, particularly the aquatic environment, cannot be over emphasized. Their presence in the environment has become a great threat all over the years because of their nonbiodegradability, toxicity, persistency, and bioaccumulation tendency [1, 2]. Heavy metals are introduced majorly into the environment through wastewater generated from various industrial activities such as mining, electroplating, metal finishing, dyeing, battery manufacturing processes, and production of paints and pigments [3, 4]. Lead is one of the most toxic heavy metals and important contaminants in aquatic environments. Lead can exist in organic and inorganic forms. Both forms have been identified to be poisonous with the former being more poisonous [5]. The maximum allowable limit of Pb considered safe in drinking water by the World Health Organization (WHO) is 50？ppb, whereas less than 15？pp is adopted by the United States Environmental Protection Agency (US EPA) [6]. The permissible limit of lead for effluent discharge to inland surface water is 0.1？mg/L [7]. Therefore, to conform to these standards and to keep a safe environment, it becomes absolutely necessary to reduce the amount of this deleterious metal from aqueous wastes generated from industries before they are released into the environment. This necessity has seriously enhanced the demand for new technologies for metal
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