Hybrid peroxi-coagulation/ozonation process for highly efficient removal of organic contaminants

Aromatic compounds such as phenols presented widely in coal chemical industry wastewater(CCW)render the treatment facing great challenge due to their biorefractory characteristics and potential risks to the environment and human health.Ozone-based advanced oxidation processes show promising for these pollutants removal,but the mineralization via ozonation alone is unsatisfactory and not cost-effective.Herein,a hybrid peroxi-coagulation/ozonation process(denoted as PCO)was developed using sacrificial iron plate as an anode and carbon black modified carbon felt as cathode in the presence of ozonation.An enhanced phenol removal of∼100%within 20 min and phenol mineralization of∼80%within 60 min were achieved with a low energy consumption of 0.35 kWh/g TOC.In this novel process,synergistic effect between ozonation and peroxi-coagulation was observed,and beside O_(3) direct oxidation,peroxone played a dominant role for phenol removal.In the PCO process,the hydrolyzed Fe species enhanced the generation of reactive oxygen species(ROS),while•OH was dominantly responsible for pollutant degradation.This process also illustrated high resistance to high ionic strength and better performance for TOC removal in real wastewater when compared with ozonation and peroxi-coagulation process.Therefore,this process is more cost-effective,being very promising for CCW treatment.

A pulsed switching peroxi-coagulation process to control hydroxyl radical production and to enhance 2,4-Dichlorophenoxyacetic acid degradation

The aim of this study was to develop a new pulsed switching peroxi-coagulation system to control hydroxyl radical(∙OH)production and to enhance 2,4-Dichlorophenoxyacetic acid(2,4-D)degradation.The system was constructed with a sacrifice iron anode,a Pt anode,and a gas diffusion cathode.Production of H_(2)O_(2) and Fe^(2+)was controlled separately by time delayers with different pulsed switching frequencies.Under current densities of 5.0 mA/cm^(2)(H_(2)O_(2))and 0.5 mA/cm^(2)(Fe^(2+)),the∙OH production was optimized with the pulsed switching frequency of 1.0 s(H_(2)O_(2)):0.3 s(Fe^(2+))and the ratio of H_(2)O_(2) to Fe^(2+)molar concentrations of 6.6.Under the optimal condition,2,4-D with an initial concentration of 500 mg/L was completely removed in the system within 240 min.The energy consumption for the 2,4-D removal in the system was much lower than that in the electro-Fenton process(686 vs.13610 kWh/kg TOC).The iron consumption in the system was~20 times as low as that in the peroxi-coagulation process(19620 vs.3940400 mg/L)within 240 min.The system should be a promising peroxi-coagulation method for organic pollutants removal in wastewater.

Removal of refractory organics and heavy metals in landfill leachate concentrate by peroxi-coagulation process

Landfill leachate is a complex effluent and it is difficult to deal with. Electrochemical methods have been considered as a promising alternative technology for treatment of landfill leachate with refractory organic contaminants and heavy metals. Peroxi-coagulation(PC)process with iron anode and modified graphite felt cathode was developed for efficient landfill leachate concentrate treatment. Compared to electro-Fenton(EF) and electrocoagulation(EC) processes, the PC process was more cost-effective due to the combined action of·OH oxidation and iron hydroxides coagulation. A maximal TOC removal of 77.2% ± 1.4% was obtained after 360 min at initial p H = 5.0 and current density of 10 m A/cm^(2). After the PC process, concentrations of all seven heavy metals in the final effluents were below the allowable emission limits given by the present regulatory standards. The method preference for heavy metal removal was PC > EC > EF. Based on the three-dimensional fluorescence spectroscopy coupled with regional integration analysis during the PC treatment, the florescence peaks of both humic acids and fulvic acids disappeared after treatment for 360min. Decreasing trends were observed in the fluorescent regional standard volumes for aromatic protein Ⅰ(31.4%), aromatic protein Ⅱ(63.7%), fulvic acid-like(69.5%), soluble microbial by-product-like(75%) and humic acid-like regions(76.3%). The results indicate that comparing to the EF and EC process, the PC process provide a promising and more cost-effective alternative for the treatment of landfill leachate concentrate.