Copper biosorption by Myriophyllum spicatum: Effects of temperature and pH

Using submerged aquatic plants is a cheap and clean technique to remediate heavy metal water pollution at low concentrations. Biosorption of Cu(II) ions by fresh tissues of Myriophyllum spicatum, a submerged aquatic plant, was characterized in an artificial solution system under different values of contact time, temperature and pH in this paper. Cu(II) biosorption was fast and equilibrium was attained within 20 min. The equilibrium biosorption data were analyzed using three widely applied isotherm models: Langmuir, Freundlich and Redlich-Peterson isotherm. Langmuir isotherm parameters obtained from the three Langmuir linear equations by using linear method were dissimilar, except when the non-linear method was used. Best fits were yielded with Langmuir and Redlich-Peterson isotherms (R²=0.961–0.992 and 0.990–0.998, respectively). The saturated monolayer biosorption capacity of M. spicatum for Cu(II) at 298 K was calculated to be 0.19 mmol/g. The biosorption capacity of M. spicatum for Cu(II) increased with increasing pH, and the resulting isotherms were well described by Langmuir and extended Langmuir models (R²=0.931–0.993 and 0.961, respectively). The comparison of calculated q _e and experimental q _e values showed that the extended Langmuir model had a better simulation for Cu(II) biosorption by M. spicatum than the Langmuir isotherm model. FT-IR was used to characterize the interaction between M. spicatum and Cu(II), with the results indicating that carboxyl groups played an important role in Cu(II) binding.