Abstract

The presence of heavy metals in aquatic environments creates many problems, and if management is not done, the health of human societies and the environment will be endangered. Due to the stability of metals in aquatic environments, we must remove them from aquatic environments. Lead is a heavy metal that is very dangerous and toxic and poses a serious threat to humans and the environment. One of the most common methods of removing heavy metals from aqueous solutions is surface adsorption and it has attracted the attention of researchers due to its good performance and efficiency in terms of economic. In this study, the ability of palm tree leaves as an adsorbent to remove lead (II) ions from aqueous solutions by surface adsorption method was investigated. The effect of three parameters (pH, initial concentration of lead (II) ions, contact time between adsorbent and lead ions) on the adsorption rate of lead was investigated and also isotherm and kinetics of lead adsorption were studied. The results showed that by increasing the pH from 4 to 6, the adsorption rate of lead by the adsorbent increased and the maximum adsorption efficiency at pH was 6. Then, by increasing the pH from 6 to 8, the adsorption rate of lead by the adsorbent decreased. Investigation of the effect of initial concentration of lead ions (II) on lead adsorption rate also showed that with increasing concentration of lead ions from 20 to 300 mg/l, the adsorption rate increases. Examination of the effect of contact time on lead adsorption rate showed that with increasing contact time between adsorbent and lead ions from 15 to 60 minutes, the adsorption rate increased and then decreased in contact time of120 minutes. Examination of adsorption isotherms showed that the Langmuir model described lead adsorption by palm tree leaves better than the Freundlich model. Investigation of adsorption kinetics showed that the Ho model was more consistent with laboratory data than the Lagergren model.