Evaluation of FeOOH performance on selenium reduction

Selenium is an important micronutrient for human and animal health: however, at elevated concentrations, it becomes toxic and could cause serious health problems. The objective of this research is to characterize a commercial adsorbent, FeOOH, and investigate the adsorption kinetics and capacity of Se(IV) onto FeOOH. Nitrogen adsorption-desorption analyses indicate that the Brunauer-Emmett-Teller (BET) specific surface of FeOOH is 361.4 m(2)/g. Analyses of spent FeOOH using scanning electron microscope (SEM) and energy dispersion spectrometer (EDS) show that the selenite can be adsorbed onto the FeOOH surface uniformly. The effects of different experimental parameters on the selenite removal efficiency of FeOOH, including solution pH, adsorption time, initial Se concentration and the presence of coexisting contaminants, were also evaluated. The adsorption of selenite was significantly affected by pH, and high removal efficiency was achieved at pH 5.0. SiO32- and PO43- both slightly reduced Se(IV) removal, especially at high concentrations, while the presence of V(V) enhanced the adsorption of Se(IV). The pseudo-second-order model demonstrated the best fitting of kinetic data for Se. Adsorption isotherms at various temperatures were developed, and the data fitted the Langmuir model. The thermodynamic characteristics of the sorption process were also evaluated experimentally, and the derived negative Delta G(0) and positive Delta H-0 values indicate that sorption is spontaneous and endothermic. (C) 2011 Elsevier B.V. All rights reserved.