Synthesis of cobalt-doped ZnO/rGO nanoparticles with visible-light photocatalytic activity through a cobalt-induced electrochemical method

ZnO is a semiconductor photocatalyst widely applied in photodegradation of organic pollutants and in photoelectric conversion. ZnO exhibits low photocatalytic activity due to poor absorption in the visible region. In this work, a novel cobalt-induced electrochemical growth method was developed to synthesize cobalt-doped ZnO/rGO nanoparticles in an aqueous solution at room temperature. Cobalt-doped ZnO/rGO nanoparticles exhibited wider visible-light absorption band ranging from 400 nm to 700 nm due to cobalt doping. The surface structure of ZnO formed by the cobalt-induced electrochemical method without other ions is suitable for photocatalytic reactions. The cobalt-doped ZnO/rGO nanoparticles were found to exhibit in photodegradation and photo-electrochemical measurements and exhibited enhanced photocatalytic activity under visible-light irradiation.

The Estimation of the Higher Heating Value of Biochar by Data-Driven Modeling

Biomass is a carbon-neutral renewable energy resource.Biochar produced from biomass pyrolysis exhibits preferable characteristics and potential for fossil fuel substitution.For time-and cost-saving,it is vital to establish predictive models to predict biochar properties.However,limited studies focused on the accurate prediction of HHV of biochar by using proximate and ultimate analysis results of various biochar.Therefore,the multi-linear regression(MLR)and the machine learning(ML)models were developed to predict the measured HHV of biochar from the experiment data of this study.In detail,52 types of biochars were produced by pyrolysis from rice straw,pig manure,soybean straw,wood sawdust,sewage sludge,Chlorella Vulgaris,and their mixtures at the temperature ranging from 300 to 800℃.The results showed that the co-pyrolysis of the mixed biomass provided an alternative method to increase the yield of biochar production.The contents of ash,fixed carbon(FC),and C increased as the incremental pyrolysis temperature for most biochars.The Pearson correlation(r)and relative importance analysis between HHV values and the indicators derived from the proximate and ultimate analysis were carried out,and the measured HHV was used to train and test the MLR and the ML models.Besides,ML algorithms,including gradient boosted regression,random forest,and support vector machine,were also employed to develop more widely applicable models for predicting HHV of biochar from an expanded dataset(total 149 data points,including 97 data collected from the published literature).Results showed HHV had strong correlations(|r|>0.9,p<0.05)with ash,FC,and C.The MLR correlations based on either proximate or ultimate analysis showed acceptable prediction performance with test R2>0.90.The ML models showed better performance with test R^(2)around 0.95(random forest)and 0.97–0.98 before and after adding extra data for model construction,respectively.Feature importance analysis of the ML models showed that ash and C were the most important inputs to predict biochar HHV.

Ozone generation enhanced by silica catalyst in packed-bed DBD reactor

In this paper,three dielectric barrier discharge(DBD)configurations,which were plain DBD with no packing,DBD with packed pure quartz fibers and DBD with packed loaded quartz fibers,were employed to investigate the effect and catalytic mechanism of catalyst materials in a packed-bed ozone generator.From the experimental results,it was clear that the DBD configuration with packed pure fibers and packed loaded fibers promotes ozone generation.For the packed-bed reactor,ozone concentration and ozone yield were enhanced by an increase of electric field in the discharge gap with the packed-bed effect.Meanwhile,the enhancement of ozone concentration and yield for the DBD reactor packed by loaded fibers with silica nanoparticles was due to the catalysis of silica nanoparticles on the fiber surface.The adsorption of silica nanoparticles on the fiber surface can prolong the retention time of active species and enhance surface reactions.

Performance of different macrophytes in the decontamination of and electricity generation from swine wastewater via an integrated constructed wetland-microbial fuel cell process

Plants constitute a major element of constructed wetlands(CWs).In this study,a coupled system comprising an integrated vertical flow CW(IVCW) and a microbial fuel cell(MFC) for swine wastewater tre atment was developed to research the effects of macrophytes commonly employed in CWs,Canna indica,Acorus calamus,and Ipomoea aquatica,on decontamination and electricity production in the system.Because of the different root types and amounts of oxygen released by the roots,the rates of chemical oxygen demand(COD) and ammonium nitrogen(NH4^+-N) removal from the swine wastewater differed as well.In the unplanted,Canna indica,Acorus calamus,and Ipomoea aquatica systems,the COD removal rates were 80.20%,88.07%,84.70%,and 82.20%,respectively,and the NH4+-N removal rates were 49.96%,75.02%,70.25%,and 68.47%,respectively.The decontamination capability of the Canna indica system was better than those of the other systems.The average output voltages were 520±42,715±20,660±27,and 752±26 mV for the unplanted,Canna indica,Acorus calamus,and Ipomoea aquatica systems,respectively,and the maximum power densities were 0.2230,0.4136,0.3614,and0.4964 W/m^3,respectively.Ipomoea aquatica had the largest effect on bioelectricity generation promotion.In addition,electrochemically active bacteria,Geobacter and Desulfuromonas,were detected in the anodic biofilm by high-throughput sequencing analysis,and Comamonas(Proteobacteria),which is widely found in MFCs,was also detected in the anodic biofilm.These results confirmed the important role of plants in IVCW-MFCs.

Modelling the thresholds of nitrogen/phosphorus concentration and hydraulic retention time for bloom control in reclaimed water landscape

The risks posed by algal blooms caused by nitrogen and phosphorus in reclaimed water used in urban water landscapes need to be carefully controlled.In this study,the combined effects of the nitrogen and phosphorus concentrations and the light intensity and temperature on the specific growth rates of algae were determined using Monod,Steele,and Arrhenius models,then an integrated algal growth model was developed.The algae biomass,nitrogen concentration,and phosphorus concentration mass balance equations were used to establish a new control model describing the nitrogen and phosphorus concentration and hydraulic retention time thresholds for algal blooms.The model parameters were determined by fitting the models to data acquired experimentally.Finally,the control model and numerical simulations for six typical algae and mixed algae under standard conditions were used to determine nitrogen/phosphorus concentration and hydraulic retention time thresholds for landscape water to which reclaimed water is supplied(i.e.,for a reclaimed water landscape).

Facile construction of honeycomb-shaped porous carbon electrode materials using recyclable sodium chloride template for efficient lithium storage

Carbon materials are the preferred anode materials for Li-ion batteries.Here,we propose an easy and sustainable strategy to prepare honeycomb-shaped porous carbon(HPC)electrode materials through a process involving simple calcination and subsequent water washing by using polyvinyl-pyrrolidone(PVP)as carbon source and NaCl as pore-forming agent.A controllable cavity size and distribution of the carbon materials can be readily obtained solely by adjusting the NaCl amount.Results showed that the optimized HPC sample had a relatively uniform cavity distribution and a highly porous structure.Moreover,the special honeycomb-shaped structure was conducive to the electronic conductivity of the electrode materials,provided a short path for Li-ion transport and a wide interface with the electrolyte,and buffered the volume change of active materials.The special honeycomb-shaped structure was also maintained well after long cycles,which improved electrode stability.When used as anode materials for Li-ion batteries(LIBs),the sample demonstrated excellent cycling stability and rate performance,with a high specific capacity of 230 mA hg^-1 and a reversible capacity of 197 mA hg^-1,after 1200 cycles at 2 C.Overall,we introduced a simple strategy for the potential mass production of porous carbon materials for LIBs.

Preparation of nZVI embedded modified mesoporous carbon for catalytic persulfate to degradation of reactive black 5

High-efficiency and cost-effective catalysts with available strategies for persulfate(PS)activation are critical for the complete mineralization of organic contaminants in the environmental remediation and protection fields.A nanoscale zero-valent iron-embedded modified mesoporous carbon(MCNZVI)with a core-shell structure is synthesized using the hydrothermal synthesis method and high-temperature pyrolysis.The results showed that nZVI could be impregnated within mesoporous carbon frameworks with a comparatively high graphitization degree,rich nitrogen doping content,and a large surface area and pore volume.This material was used as a persulfate activator for the oxidation removal of Reactive Black 5(RB5).The effects of the material dosage,PS concentration,pH,and some inorganic anions(i.e.,Cl^(−),SO_(4)^(2−))on RB5 degradation were then investigated.The highest degradation efficiency(97.3%)of RB5 was achieved via PS(20 mmol/L)activation by the MCNZVI(0.5 g/L).The pseudo-first-order kinetics(k=2.11×10^(−2)min^(−1))in the MCNZVI/PS(0.5 g/L,20 mmol/L)was greater than 100 times than that in the MCNZVI and PS.The reactive oxygen species(ROS),including^(1)O_(2),SO_(4)^(·−),HO^(.),and·O_(2)^(−),were generated by PS activation with the MCNZVI.Singlet oxygen was demonstrated to be the primary ROS responsible for the RB5 degradation.The MCNZVI could be reused and regenerated for recycling.This work provides new insights into PS activation to remove organic contamination.