Adsorption of cadmium ion from aqueous solution by ground wheat stems

The adsorption behavior of cadmium on ground wheat stems has been investigated in aqueous solution to understand the physicochemical process involved and to explore the potentiality of wheat stems in wastewater treatment. The results have shown that 0.1032 mmol of cadmium is adsorbed per gram of ground wheat stems. The binding process is strongly affected by solution pH, and the optimum pH is 5.0. The process obeys the Langmuir isotherm model. Blocking of the functional groups on ground wheat stems by chemical modification causes the decrease of the maximum cadmium binding capacity, while increasing the number of the functional groups can enhance the binding capacity of ground wheat stems. Fourier transform infrared spectrometer (FTIR) analysis confirms the chemical modification process and indicates that COO- groups on the ground wheat stems are one of the main active groups in cadmium adsorption process. The X-ray photoelectron spectroscopy (XPS) data further indicates that cadmium is adsorbed as Cd2+ and is attached to O- groups on the ground wheat stems. (C) 2008 Elsevier B.V. All rights reserved.