investigating the isotherm and kinetics of lead and cadmium absorption from leachate of waste materials by natural sorbents

background: presence of heavy metals in leachate due to the biological accumulation characteristics of these materials endangered the living creatures' health especially human. purpose of this study is to study and investigate the possibility of two metals' absorption i.e, lead and cadmium from leachate by natural zeolite clinopteliolit and increase of the ability to absorb the zeolite by modified surface. methods: to examine these two metals 'ability in absorption (lead and cadmium) and variables such as type of sorbent, sorbent concentration and contact time were studied. zeolites samples used by the tests i.e, x-ray florescence, the spectrum of x-ray diffraction and bet were analyzed for compound identification. findings: the absorption efficiency of the modified zeolites was increased from 4.2 and 5.3 percent to 71.6 and 75.2٪ for lead and cadmium respectively. with increasing the surfactant concentration from 2 to 20 mmol/l, the absorption efficiency of modified zeolit for lead and cadmium was increased to 71 and 74%, respectively. the best isotherm model for lead adsorption was freundlich model, with a determination coefficient equal to 0.99, and for cadmium it was langmuir model with a determination coefficient equal to 0.99. conclusion: the modified zeolite with surfactant can be used as an appropriate adsorbent for separation of heavy metals from waste leachate. lead and cadmium absorbed in single layer on the modified zeolite with surfactant and with comparing parameters of different studied isotherm models indicated that the capacity of modified zeolite for lead adsorption was more than cadmium adsorption, but cadmium was absorbed with higher energy.