Isotherm and Thermodynamic studies on the biosorption of Pb(II), Ni(II) and Cd(II) ions from aqueous solution onto Newbouldia leavis (Bignonaesia) pod powder.

Abstract

Anthropogenic activities may have posed a serious threat to the environment due to the release of heavy metal into the environment. In this study, the adsorption behaviour of Newbouldia leavis as regards Pb(II), Ni(II) and Cd(II) ions from wastewater has been studied. A series of experiments were conducted in a batch system to assess the effects of the system variables such as of pH, temperature and initial metal concentrations in solution ranging from 10 to 50 mg/L. The experiment showed that the solution pH strongly influenced the adsorptive capacity of the adsorbent as maximum adsorption occurred at pH 4 for Pb(II) ions and pH 6 for both Ni(II) and Cd(II) ions. For the isotherms models applied for sorption studies, Freundlich best described the data properly. The maximum adsorption capacity of Pb(II), Cd(II) and Ni(II) are 0.0042 mg/g, 0.178 mg/g and 0.552 mg/g respectively. The negative value of  G0 indicates the feasibility and spontaneous nature of the process. The negative value of  H0: -50707.09, -8804.53 and -7234.01 for Pb(II), Cd(II) and Ni(II) ions respectively confirms the exothermic nature of adsorption. Moreover, the negative value of  S0:  -51197.6, -62.79 and -209.18 for Ni(II), Cd(II) and Pb(II) ions respectively suggests the decreased randomness at the solid-solution interface during adsorption process. According to the equilibrium studies, the selectivity sequence can be given as Ni2+ > Cd2+ > Pb2+. These results show that Newbouldia leavis holds great potential to remove cationic heavy metal species from industrial wastewater. Key Words: Heavy metal, Newbouldia leavis, biosorption, Equilibrium, Thermodynamics.