[Characteristics of Pb2+ and Cd2+ sorption in aqueous solution by wheat straw]

Wheat straw was used as biosorbent for lead and cadmium removal from aqueous solution. Especially, the effect of solution pH, contact time and ions concentration on the sorption process was intensively discussed. Result indicated that the metal removal was strongly dependent on solution pH and the sorption capacity increased with the increasing of solution pH in the pH range of 2.0-6.0. The sorption kinetic process fit well with the pseudo-second-order. Langmuir isotherm equation was used to evaluate the sorption capacity of the biomass. The q(max) values for Pb2+ and Cd2+ were 0.15 mmol x g(-1) and 0.11 mmol x g(-1) respectively. After NaOH hydrolated, wheat straw showed higher sorption capacity both for Pb2+ and Cd2+, q(max) values for Pb2+ and Cd2+ reached 0.31 and 0.22 mmol x g(-1) respectively. While the sorption capacity for Pb2+ and Cd2+ on esterified wheat straw decreased greatly. Fourier transform infrared spectroscopy (FTIR) analysis showed that carboxylic groups on the biomass play an important role in Pb2+ and Cd2+ sorption process.