The sorption properties for U(Ⅵ) and Cu(Ⅱ) ions

alone or mixed

onto raw sunflower straw were systematically evaluated in a series of batch experiments by varying solution pH

adsorbent dosage

temperature

contact time and initial ion concentration. The kinetic data were examined with pseudo-second-order kinetic model

and the equilibrium data obtained were analyzed with Langmuir

Freundlich and Langmuir-Freundlich isotherm equations. It was shown that the positive and negative enthalpy change suggested the endothermic and exothermic nature of U(Ⅵ) and Cu(Ⅱ) ions sorption

respectively. The kinetic data followed pseudo-second-order equation

indicating that the chemical process (adsorption) was rate-limiting step. The equilibrium adsorption data of alone U(Ⅵ) and Cu(Ⅱ) ions could be well described with Langmuir-Freundlich and Langmuir isotherm model

respectively. While for mixed U(Ⅵ) and Cu(Ⅱ) ions Langmuir-Freundlich equation was better for U(Ⅵ) ion at Cu(Ⅱ) concentration more than 60 mg·L-1

but Langmuir model was best for Cu(Ⅱ) ion at U(Ⅵ) concentration more than 200 mg·L-1. Obviously

sunflower straw is of an excellent adsorption selectivity toward U(Ⅵ) over Cu(Ⅱ) in terms of distribution coefficient and separation factor

which was likely related to itself properties of metal ion. Furthermore

these results obtained by FT-IR

SEM and EDX revealed that the adsorption mechanism of U(Ⅵ) and Cu(Ⅱ) ions onto sunflower straw is likely to ion exchange and complexation.