This research was carried out to investigate the removal of lead from battery manufacturing wastewater by egg shells. The effect of operating parameters i.e., initial pH, contact time, types of egg shell and dose of egg shell were investigated. The characteristics and chemical compositions of egg shells were also investigated and experimental samples were analyzed using AAS, then the data was statistically processed using least significant difference at a 95% confidence level (p<0.05). The results indicated that the optimum pH for lead removal using 4 types of egg shell was at pH 6, but at this pH final concentration of lead was too low for study of adsorption isotherm. Therefore, unadjusted pH wastewater was used with an initial lead concentration of about 2.365 mg/L, initial pH of 1.35-1.45. Unadjusted pH wastewater decreased the use of expensive chemical reagent for adjusting pH and reduced chemical residues in the environment due to basic properties of egg shell which immediately increased the pH of solution. The optimum dose of egg shell was 1.0 g/100 ml of wastewater with a contact time of 90 minutes. The best adsorbent was natural duck egg shell, which had a significant difference from the other types of egg shell. The final concentration of lead was 0.059 mg/L which was lower than the wastewater quality standard. Equilibrium modeling of the adsorption isotherm showed that removal of lead by 4 types of egg shells were able to be described by the Freundlich model. From this study, precipitation might take part in the adsorption process, especially at the high doses of egg shell which increased the high final pH of solution. Finally, the result of the adsorption isotherm demonstrated that the descending lead removal efficiency was natural duck egg shell, natural hen egg shell, boiled duck egg shell and boiled hen egg shell, respectively.
