Fluorinated compounds have become prevalent in ecosystems because of their widespread use, yet few methods that can effectively degrade these pollutants exist. We investigated the catalytic reduction of vinyl fluoride (VF), a regulated high-volume chemical and probable carcinogen, over rhodium in H 2 gas or aqueous solution. Water controlled both the kinetics and products of VF reduction. In dry H 2 gas, VF was reduced through primarily hydrogenation, at rates that were too fast to measure. In liquid water, reaction was firstorder in both VF and rhodium concentrations and proceeded predominantly through hydrodefluorination. Experiments and calculations show the reaction was mass transfer-limited. Even adsorbed water molecules on the catalyst surface posed a significant mass transfer barrier and dramatically altered product selectivity. These results provide insights into the kinetics and pathway of VF defluorination and are important for the design of studies that aim to elucidate the reduction mechanisms of and develop treatment methods for fluorocarbons.

Arsenic (As) contamination in groundwater is a great environmental health concern and is often the result of contact between groundwater and arsenic-containing rocks or sediments and from variation of pH and redox potentials in the subsurface. In the past decade, magnetite nanoparticles (MNPs) have been shown to have high adsorption activity towards As. Alerted by the reported cytotoxicity of 5–12 nm MNP, we studied the adsorption behavior of 1.15 nm MNP and a MNP composite (MNPC), MNPs interlinked by silane coupling agents. With an initial concentration of As at 25 mg L−1, MNPs exhibited high adsorption capacity for As(V) and As (III), 206.9 mg·g−1 and 168.6 mg·g−1 under anaerobic conditions, respectively, and 109.9 mg·g−1 and 108.6 mg·g−1 under aerobic conditions, respectively. Under aerobic conditions, MNPC achieved even higher adsorption capacity than MNP, 165.1 mg·g−1 on As(V) and 157.9 mg·g−1 on As(III). For As(V) at 50 mg L−1, MNPC achieved an adsorption capacity as high as 341.8 mg·g−1, the highest in the literature. A kinetic study indicated that this adsorption reaction can reach equilibrium within 15 min and the rate constant of As(V) is about 1.9 times higher than that of As(III). These results suggested that MNPC can serve as a highly effective adsorbent for fast removal of As.