A plasma-generated carbon aerosol, with the merits of high surface area, abundant porosity and high crystallinity, is a mass synthesized by-product from direct methane conversion in the production of syngas or hydrogen. In the present work, a carbon aerosol produced by rotating gliding arc (RGA) plasma was firstly incorporated with a commercial sponge to fabricate a highly selective and hydrophobic adsorption material. The properties of the carbon aerosol and its derived sponge were comprehensively characterized. By a simple dip-coating method, the wettability of the pristine sponge was altered, which was attributed to the plasma coating of the carbon aerosol. The modified sponge demonstrated an effective and selective adsorption ability for a wide range of oils and solvents, with the maximum adsorption capacity of up to 86 times its own weight. Moreover, the used sponge could be easily recovered by simple evaporation or manual squeezing, while maintaining approximately 100% of its starting adsorption capacity over 5 adsorption-recovery cycles. Such a plasma carbon aerosol coated sponge exhibits a great prospect as a cost-efficient, recyclable and scalable material in separation and adsorption for water treatment.

•A rapid, cost-effective, and comparative methodology was proposed to evaluate the HVs of burning MSW online.•Models ranked in descending order of performance are ANFIS, RF, SVM, MLP.•A well trained model is capable of characterizing the variation trend of HVs accurately.The heating values, particularly lower heating values of burning municipal solid waste are critically important parameters in operating circulating fluidized bed incineration systems. However, the heating values change widely and frequently, while there is no reliable real-time instrument to measure heating values in the process of incinerating municipal solid waste. A rapid, cost-effective, and comparative methodology was proposed to evaluate the heating values of burning MSW online based on prior knowledge, expert experience, and data-mining techniques. First, selecting the input variables of the model by analyzing the operational mechanism of circulating fluidized bed incinerators, and the corresponding heating value was classified into one of nine fuzzy expressions according to expert advice. Development of prediction models by employing four different nonlinear models was undertaken, including a multilayer perceptron neural network, a support vector machine, an adaptive neuro-fuzzy inference system, and a random forest; a series of optimization schemes were implemented simultaneously in order to improve the performance of each model. Finally, a comprehensive comparison study was carried out to evaluate the performance of the models. Results indicate that the adaptive neuro-fuzzy inference system model outperforms the other three models, with the random forest model performing second-best, and the multilayer perceptron model performing at the worst level. A model with sufficient accuracy would contribute adequately to the control of circulating fluidized bed incinerator operation and provide reliable heating value signals for an automatic combustion control system.

PCDD/Fs in fly ash from municipal solid waste incinerators (MSWIs) can be decomposed in non-thermal plasma, more in particular in a vortex-shaped gliding arc. Typical operating conditions are 10 kV voltage, 40 kΩB external current-limited resistor, 11 L/min tangential gas and 2 L/min axial carrier gas flow rates. Degradation efficiencies of PCDD/Fs are respectively 54.9, 61.7 and 66.8 % on mass basis and 60.7, 73.3 and 70.1 % on toxicity basis under N2, air and O2 condition. After treatment the morphology of fly ash has changed: needle-shaped crystals increasing, pores and fragments appearing and high-temperature melting showing which is leaded by direct contact with high-temperature core of arc. The results are explained tentatively by the creation of reactive intermediates leading to dechlorination and oxidation of PCDD/Fs and finally producing end-products such as CO2, CO, HCl and CH4.

Phytoextraction has become one of the most promising remediation techniques for heavy metal (HM) contaminated soils. However, the technique invariably produces large amounts of HM-enriched hyperaccumulators, which need further safe disposal. In this study, two different thermal treatment methods are investigated as potential options for evaporative separation of HMs from the residues. A horizontal tube furnace and a vertical entrained flow tube furnace were used for testing the disposal of grounded hyperaccumulators. The release characteristics of HMs (Cd, Cu, Pb, and Zn) into flue gas and residues were investigated for thermal treatment of the Cd and Zn hyperaccumulators Sedum plumbizincicola and Sedum alfredii. In a horizontal tube furnace, incineration favors the volatilization of Cu and Cd in contrast to pyrolysis. The percentages of HMs in residues after incineration are lower than those after pyrolysis, especially for Cd, Pb, and Zn. However, in an entrained flow tube furnace, Zn content in flue gas increases with increasing temperature, but Cu and Cd contents are fluctuated. In addition, a higher incineration temperature enhances the Cu content in residues.

The effects of SO2, SO3 on de novo synthesis of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were studied using model fly ashes incorporating copper oxide and activated carbon. It was found that the inhibitive effect of SO2 on PCDD/Fs formation is similar to that of SO3. To investigate the inhibition mechanism, CuSO4 formations from both CuO and CuCl2 were examined. The ability of SO3 to convert CuCl2 and CuO on a silica support into sulfate is much stronger than that of SO2. However, replacing silica by activated carbon leads to a much high conversion of CuCl2 to CuSO4 in the presence of SO2. The promotion by activated carbon is explained by the reduction of CuCl2 to Cu2Cl2 and the eventual conversion of Cu2Cl2 into CuSO4 is the main inhibition mechanism of SO2 on de novo synthesis of PCDD/Fs.

Gliding arc discharge has been proved to be effective in treatment of gas and liquid contaminants. In this study, physical characteristics of dc gliding arc discharge and its application to naphthalene destruction are investigated with different external resistances and carrier gases. The decomposition rate increases with increasing of oxygen concentration and decreases with external resistance. This value can be achieved up to 92.3% at the external resistance of 50 kΩ in the oxygen discharge, while the highest destruction energy efficiency reaches 3.6 g (kW h)−1 with the external resistance of 93 kΩ. Possible reaction pathways and degradation mechanisms in the plasma with different gases are proposed by qualitative analysis of postdestructed products. In the air and oxygen gliding arc discharges, the naphthalene degradation is mainly governed by reactions with oxygen-derived radicals.

The effects of temperature and time on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) distribution in fly ash of a municipal solid waste incinerator (MSWI) were studied in a tubular oven under nitrogen atmosphere. The PCDD/Fs in the gas phase and solid phase were detected by high-resolution gas chromatography coupled with low resolution mass spectrometry (HRGC/LRMS) separately. The experimental results showed that the major congener was octa-chlorinated dibenzo-p-dioxin (OCDD) in the gas phase and the low chlorinated congeners were the major products in the solid phase. There were high levels of OCDD in the gas phase in several experimental conditions although the PCDD/Fs in the solid phase could be decomposed. The optimum condition for PCDD/Fs decomposition in fly ash was a heating time of 60 min at 400 °C under nitrogen atmosphere.

•A rapid and cost-effective prediction for the LHV of MSW was developed.•The prediction equation was based on estimated LHVs of wet combustibles in MSW.•The prediction performance of the equation is suitable for practical application.A rapid and cost-effective prediction method based on wet physical composition has been developed to determine the lower heating value (LHV) of municipal solid waste (MSW) for practical applications in China. The heating values (HVs) of clean combustibles were measured in detail, and the effect of combustibles, food waste, and ash content on HV was studied to develop the model. The weighted average HV can be used to predict the MSW HV with high accuracy. Based on the moisture measurements of each major real combustible and the HV of clean solid waste, a predictive model of the LHV of real MSW was developed. To assess the prediction performance, information was collected on 103 MSW samples from 31 major cities in China from 1994 to 2012. Compared with five predictive models based on the wet physical composition from different regions in the world, the predictive result of the developed model is the most accurate. The prediction performance can be improved further if the MSW is sorted better and if more information is collected on the individual moisture contents of the waste.

•Rotating gliding arc (RGA) is proposed in coal bed methane (CBM) conversion.•The performance of CBM surrogate conversion in RGA is comprehensively evaluated.•2D graphene sheets are formed in CBM surrogate conversion by RGA discharge.A novel atmospheric pressure non-thermal plasma, i.e., rotating gliding arc (RGA), is developed to upgrade coal bed methane (CBM) into hydrogen and carbon aerosol simultaneously. CH4 is used as a CBM surrogate. In present work, the V-I characteristics of RGA discharge in CH4 conversion are monitored with different gases (N2, Ar and CO2) as carrier gas, while the active species (such as OH, CH, CN, C2, excited molecules and ions) involved in the plasma reactions are identified by optical emission spectroscopy (OES). According to the sensitivity analysis of specific energy density (SED), the importance of operating conditions on SED sensitivity is in a sequence of CH4 concentration > applied voltage > residence time. The performance of CH4 conversions are comparatively evaluated based on the variation of operating conditions. In general, the enhancement of applied voltage and residence time effectively increases the CH4 conversions, selectivity of hydrogen, as well as the energy efficiency, while the augment of CH4 concentration has a negative effect in contrast. The carbon aerosol obtained in CH4/N2 and CH4/Ar discharge are comparatively investigated. Transparent crumped-like graphene sheets and spherical nanostructure carbon are observed in both obtained carbon aerosol, with relative high ID/IG ratios (∼0.62) indicated in Raman spectroscopy. High C/O ratios (>14) are obtained in the XPS survey spectra, with the intensity ratios of sp2 CC/sp3 C-C occupy about 80%. However, the BET surface area of carbon obtained from CH4/N2 is almost 3 times larger than that from CH4/Ar discharge. In addition, super hydrophobic and oleophilic properties are observed in both carbon samples. The contact angles of water droplets are above 130°, while the contact angle of oil is less than 4°.