Investigation effect of pH, adsorbent dosage and initial concentration on lead adsorption of contaminated water by goethite and Hormoz Island ochre

Adsorption is one of the effective and frugal methods that used for removal of toxic metals-such as lead- from wastewater. In this paper، effect of three parameters including pH، adsorbent dosage and initial concentration of lead has been studied by two inexpensive adsorbents including natural goethite and Hormoz island ochre. The effect pH on lead adsorption by each of adsorbents shows that lead adsorption percent increase with pH increasing to 5%. On the other hand، experiments showed that with increasing adsorbent dosage، adsorption percent increase in both adsorbents. But ochre unlike goethite has high ability for lead adsorption even in adsorbent dose 2 g/L. Investigations showed that in high lead concentrations ochre toward goethite is more effective adsorbent for lead. So that ochre under condition with initial concentration 150 mg/L، ambient temperature (23. 5◦C)، pH=5، adsorbent dose 6g/L، reaction time 60 min and particle size smaller than 230 mesh removes 97. 57% of lead. Goethite removes 78. 53% of lead at the same condition. In this condition، maximum lead adsorption capacity for ochre and goethite is 24. 39 and 19. 63mg/g respectively. Initial concentration and adsorption percent shows direct relation for ochre، but reverse for goethite. Langmuir and Frundlich adsorption isotherms show that goethite follows Langmuir model with correlation coefficient of 0. 995، but ochre almost follows both models of Langmuir and Frundlich.