Sequestration of Antimonite by Zerovalent Iron: Using Weak Magnetic Field Effects to Enhance Performance and Characterize Reaction Mechanisms.

Many oxyanion-forming metals (As, Sb, Se, Tc, etc.) can be removed from water by adsorption and/or redox reactions involving iron oxides, including the oxides associated with zerovalent iron (ZVI). The rate of antimonite (Sb(III) hydrolysis species) removal by ZVI was determined in open, well-mixed batch reactors as a function of experimental factors, including aging of the ZVI, addition of Fe(II), Sb dose, mixing rate, pH, initial concentrations of Sb(III), etc. However, the largest effect observed was the roughly 6-8 fold increase in Sb(III) removal rate due to the application of a weak magnetic field (WMF) during the experiments. The WMF effect on Sb removal arises from stimulated corrosion and delayed passivation of the ZVI, as evidenced by time series correlation analysis of "geochemical" properties (DO, Fetot, Eh, and pH) measured synchronously in each experiment. The removal of Sb under the conditions of this study was mainly due to oxidation of Sb(III) to Sb(V) and adsorption and coprecipitation onto the iron oxides formed from accelerated corrosion of ZVI, as evidenced by Sb K-edge XANES, EXAFS, and XPS. The degree of the WMF enhancement for Sb(III) was found to be similar to the WMF effect reported previously for Sb(V), As(III), As(V), and Se(VI).

Bromate removal from aqueous solutions by ordered mesoporous carbon.

We investigated the feasibility of using ordered mesoporous carbon (OMC) for bromate removal from water. Batch experiments were performed to study the influence of various experimental parameters such as the effect of contact time, adsorbent dosage, initial bromate concentration, temperature, pH and effect of competing anions on bromate removal by OMC. The adsorption kinetics indicates that the uptake rate ofbromate was rapid at the beginning: 85% adsorption was completed in 1 h and equilibrium was achieved within 3 h. The sorption process was well described with pseudo-second-order kinetics. The maximum adsorption capacity of OMC for bromate removal was 17.6 mg g(-1) at 298 K. The adsorption data fit the Freundlich model well. The amount of bromate removed was found to be proportional to the influent bromate concentration. The effects of competing anions and solution pH (3-11) were negligible. These limited data suggest that OMC can be effectively utilized for bromate removal from drinking water.