Lead biosorption using a dairy sludge--thermodynamic study and competition effects

Local diary sludge as a biosorbent was used in this study for lead ion adsorption from aqueous solution. Batch experiments were carried out as a function of temperature, initial concentration, and ionic strength. Lead uptake was significantly enhanced from 149 to 224 mg/g of dairy sludge by a temperature increase at pH 5. Equilibrium data for metal ion adsorption were analyzed using model equations, namely Langmuir and Freundlich isotherms, and the best fit to the experimental data was provided by the first isotherm model. Brunauer-Emett-Teller and Fourier transform infrared analyses were also performed to characterize the biosorbent. Ionic strength using NaCl, NaNO3, and Ca(NO3)2 did not affect Pb(+2) sorption, while there was a 20% decrease using CaCl2. A limited effect of Cd(+2) ions present in the binary system on lead sorption was observed. This study shows that this local dairy sludge can be an alternative to the commercially available adsorbents for the removal of heavy metals from liquid effluents.