Utilization of water hyacinth weed {Eichhornia crassipes) for the removal of Pb(II), Cd(II) and Zn(II) from aquatic environments: an adsorption isotherm study

摘要

The potential of Eichhornia crassipes biomass for the adsorption of three metal ions, Pb(II), Cd(II) and Zn(II), from aqueous solution was studied using five two-parameter adsorption isotherm equations - Langmuir, Freundlich, Flory-Huggins, Temkin and Redlich-Peterson isotherms. The equilibrium adsorption data were obtained at different initial metal ion concentrations (C_o = 10-60 mg/L), 3 h contact time, 30 ℃ temperature, a dosage of 2 g/L, agitation rate of 150 rpm and buffered at pH 4.84. Langmuir isotherms gave monolayer sorption capacities (q_m) of 26.32, 12.60 and 12.55 mg/g for Pb(II), Cd(II) and Zn(II) metal ions, respectively. The same trend of metal uptake was indicated by plots of sorption favourability (S_F). Negative values of ΔG_(ads)~o indicated that the adsorption was spontaneous and exothermic in nature, and values from the Temkin isotherm constant, b_T, suggested a mechanism consistent with an ion-exchange process. The results from these studies indicated that E. crassipes biomass has promising potential for the removal of toxic metals from aquatic environments.