Study On The Adsorption Of Lead,Copper,and Mercury By Coriander

Removing the pollutants in the wastewater by the biologic adsorbent is a kind of economic,effective and environmentally friendly water treatment technology,which has attracted much attention in the recent 20 years.It was investigated that absorptive effect of coriander on Pb(Ⅱ),Cu(Ⅱ)and Hg(Ⅱ),and the influence of pH value,adsorption time,adsorbent additive amount,initial concentration of heavy metals in waste water and coexisting ions on coriander adsorption.The adsorption process,dynamics and the isothermal model were fitted to preliminary explore the adsorption mechanism.The main results were as follows:1)The gradient of adsorption capacity of coriander for three heavy metal ions was as follows Pb(Ⅱ)>Cu(Ⅱ)>Hg(Ⅱ).2)The adsorption processes overall were fast for Pb(Ⅱ),Cu(Ⅱ)and Hg(Ⅱ),adsorption equilibrium time was 20 min.The adsorption process of Pb(Ⅱ),Cu(Ⅱ)and Hg(Ⅱ)were affected by the pH value.When the pH value was at 1.5-5.5 range,adsorption capacity and removal rate was increased along with the rose of pH.The maximum adsorption capacity was found at pH5.5 for the adsorption by coriander.The amount of coriander added,coriander of Pb(Ⅱ),Cu(Ⅱ)and Hg(Ⅱ)removal rate increased,and the adsorption quantity falled;the result of which was opposite to effect of the initial concentration.Na+,K+ had little influences on adsorption,while Zn2+,Ca2+,Mg2+ affected the adsorption quite significantly.Coriander had good regeneration capacity.There was only a slight decrease of metal adsorbed(2.81%),desorbed(2.24%)and a small loss of mass of adsorbent after regeneration for 5 times by 0.1 M HNO3 as eluted solution.The adsorption of Pb(Ⅱ),Cu(Ⅱ)and Hg(Ⅱ)by coriander all went with pseudo second order model as well as the Langmuir isotherm.The dynamics studies revealed that the models were all spontaneous and endothermic processes.Adsorption process was dominated by chemical adsorption.