Magnéli phases TinO2n-1 as novel ozonation catalysts for effective mineralization of phenol

Magnéli phases Ti_nO_(2n-1)have been demonstrated as promising environmentally friendly materials in advanced oxidation processes.In this study,Magnéli phases Ti_nO_(2n-1)have been used as catalysts for the ozonation of phenol in aqueous solution for the first time.The materials exhibited excellent catalytic ozonation activities both in phenol degradation and mineralization.When Ti_4O_7was added,the reaction rate was six-fold higher than that of with ozone alone,while the total organic carbon removal rate was substantially elevated from around 19.2%to 92%.By virtue of the good chemical stability of the materials,a low metal leaching of less than 0.15 mg·L^(-1)could effectively avoid the secondary pollution by metal ions.Radical quenching tests revealed·O_2^-and^1O_2to be active oxygen species for phenol degradation at p H 5.As semiconductor catalysts,Ti_nO_(2n-1)materials show electronic transfer capability.Ozone adsorbed at B-acid sites of the catalyst surface can capture an electron from the conversion of Ti(III)to Ti(IV),and is thereby broken into the active oxygen species.It was interesting to observe that Ti_nO_(2n-1)exhibit better catalytic activity for phenol degradation and mineralization with lower n value.The difference in electrical conductivity can be considered as a major factor for the catalytic performances.More highly conductive catalysts show a faster electron-transfer rate and better catalytic activity.Thus,significant evidences have been obtained for a single-electron-transfer mechanism of catalytic ozonation with Magnéli phases Ti_nO_(2n-1).

Chlorine-free emission disposal of spent acid etchant in a three-compartment ceramic membrane reactor

Electrochemical technologies for the on-site treatment of spent acid etchant have received great attention due their ease of operation and economic benefits. On the other hand, a large amount of Cl2 is generated during the electrolysis process, which leads to potential environmental risks. In the present work, a novel threecompartment ceramic membrane flow reactor, including a cathode chamber, an anode chamber, and a gas absorption chamber was developed. The three chambers were divided by an Al2O3 ceramic membrane and a breathable hydrophobic anode diffusion electrode(ADE). The Cl2 evolution onset potential of the ADE was increased to 1.19 V from 1.05 V of the graphite felt, effectively inhibiting the chlorine evolution reaction(CER).The anode-generated Cl2 diffused into the gas absorption chamber through the ADE and was eventually consumed by the H2O2 adsorbent. Cu could be recovered without emitting chlorine due to the special structure of reactor. The current efficiency of copper precipitation and cathode reduction from Cu2+to Cu+reached 97.7%at a working current of 150 m A. These results indicated that the novel membrane reactor had high potential for application in the copper recovery industry.