Catalytic ozonation in advanced treatment of kitchen wastewater:multi-scale simulation and pilot-scale study

Catalytic ozonation is regarded as a promising technology in the advanced treatment of refractory organic wastewater.Packed-bed reactors are widely used in practical applications due to simple structures,installation and operation.However,mass transfer of packed-bed reactors is relatively restrained and amplified deviations usually occurred in scale-up application.Herein,a multi-scale packed-bed model of catalytic ozonation was established to guide pilot tests.First,a laboratory-scale test was conducted to obtain kinetic parameters needed for modeling.Then,a multi-scale packed-bed model was developed to research the effects of water distribution structure,catalyst particle size,and hydraulic retention time(HRT)on catalytic ozonation.It was found that the performance of packed bed reactor was increased with evenly distributed water inlet,HRT of 60 min,and catalyst diameter of about 3-7 mm.Last,an optimized reactor was manufactured and a pilot-scale test was conducted to treat kitchen wastewater using catalytic ozonation process.In the pilot-scale test with an ozone dosage of 50 mg/L and HRT of 60 min,the packed-bed reactor filled with catalysts I was able to reduce chemical oxygen demand(COD)from 117 to 59 mg/L.The performance of the catalytic ozonation process in the packed-bed reactor for the advanced treatment of actual kitchen wastewater was investigated via both multi-scale simulation and pilot-scale tests in this study,which provided a practical method for optimizing the reactors of treating refractory organic wastewater.

One-step ball milling-prepared nano Fe2O3 and nitrogendoped graphene with high oxygen reduction activity and its application in microbial fuel cells

Developing high activity,low-cost and long durability catalysts for oxygen reduction reaction is of great significance for the practical application of microbial fuel cells.The ftill exposure of active sites in catalysts can enhance catalytic activity dramatically.Here,novel Fe-N-doped graphene is successftilly synthesized via a one-step in situ ball milling method.Pristine graphite,ball milling graphene,N-doped graphene and Fe-N-doped graphene are applied in air cathodes,and enhanced performance is observed in microbial fuel cells with graphene-based catalysts.Particularly,Fe-Ndoped graphene achieves the highest oxygen reduction reaction activity,with a maximum power density of 1380±20 mW/m^2 in microbial fUel cells and a current density of 23.8 A/m^2 at-0.16 V in electrochemical tests,which are comparable to commercial Pt and 390%and 640%of those of pristine graphite.An investigation of the material characteristics reveals that the superior performance of Fe-Ndoped graphene results from the full exposure of Fe2O3 nanoparticles,pyrrolic N,pyridinic N and excellent Fe-N-G active sites on the graphene matrix.This work not only suggests the strategy of maximally exposing active sites to optimize the potential of catalysts but also provides promising catalysts for the use of microbial fuel cells in sustainable energy generation.

Erratum to: One-step ball milling-prepared nano Fe2O3 and nitrogen-doped graphene with high oxygen reduction activity and its application in microbial fuel cells

Erratum to:Front.Environ.Sci.Eng.2020,14(2):30 https://doi.org/10.1007/s 11783-019-1209-1 The authors wish to make some corrections as below:(1)Some errors occurred when Fig.5d was exported and the corrected version is shown here.