No abstract

Magnéli phase titanium suboxide, Ti4O7, has attracted increasing attention as a potential electrode material in anodic oxidation as a result of its high efficiency and (electro)­chemical stability. Although carbon materials have been amended to Ti4O7 electrodes to enhance the electrochemical performance or are present as an unwanted residual during the electrode fabrication, there has been no comprehensive investigation of how these carbon materials affect the electrochemical performance of the resultant Ti4O7 electrodes. As such, we investigated the electrochemical properties of Ti4O7 electrodes impregnated with carbon materials at different contents (and chemical states). Results of this study showed that while pure Ti4O7 electrodes exhibited an extremely low rate of interfacial electron transfer, the introduction of minor amounts of carbon materials (at values as low as 0.1 wt %) significantly facilitated the electron transfer process and decreased the oxygen evolution reaction potential. The oxygen-containing functional groups have been shown to play an important role in interfacial electron transfer with moderate oxidation of the carbon groups aiding electron uptake at the electrode surface (and consequently organic oxidation) while the generation of carboxyl groupsa process that is likely to occur in long-term operationincreased the interfacial resistance and thus retarded the oxidation process. Results of this study provide a better understanding of the relationship between the nature of the electrode surface and anodic oxidation performance with these insights likely to facilitate improved electrode design and optimization of operation of anodic oxidation reactors.

Environmental context. Reverse osmosis (RO) is widely used for the treatment of hazardous wastewaters produced from the coal chemical industry (CCI) to achieve zero liquid discharge however the use of RO inevitably results in accumulation of refractory organic matter in the RO membrane concentrate, the treatment of which is challenging. This work provides useful insights into the organic composition of RO concentrates obtained from a range of real CCI wastewaters. The efficacy of treatment of these concentrates by ozonation processes is assessed as is the cost effectiveness of such treatment.

Heterogeneous catalytic ozonation (HCO) has gained increasing attention as an effective process to remove refractory organic pollutants from industrial effluents. However, widespread application of HCO is still limited due to the typically low efficacy of catalysts used and matrix passivation effects. To this end, we prepared an Al 2 O 3 -supported Fe catalyst with high reactivity via a facile urea-based heterogeneous precipitation method. Due to the nonsintering nature of the preparation method, a heterogeneous catalytic layer comprised of γ-FeOOH and α-Fe 2 O 3 is formed on the Al 2 O 3 support (termed NS-Fe-Al 2 O 3 ). On treatment of a real industrial effluent by HCO, the presence of NS-Fe-Al 2 O 3 increased the removal of organics by ∼100% compared to that achieved with a control catalyst (i.e., α-Fe 2 O 3 /Al 2 O 3 or γ-FeOOH/Al 2 O 3 ) that was prepared by a conventional impregnation and calcination method. Furthermore, our results confirmed that the novel NS-Fe-Al 2 O 3 catalyst demonstrated resistance to the inhibitory effect of high concentration of chloride and sulfate ions usually present in industrial effluent. A mathematical kinetic model was developed that adequately describes the mechanism of HCO process in the presence of NS-Fe-Al 2 O 3 . Overall, the results presented here provide valuable guidance for the synthesis of effective and robust catalysts that will facilitate the wider industrial application of HCO.

No abstract