Mechanochemistry (MC) exerts extraordinary degradation and decomposition effects on many chlorinated, brominated, and even fluorinated persistent organic pollutants (POPs). However, its application is still limited by inadequate study of its reaction kinetic aspects. In the present work, the ball motion and energy transfer in planetary ball mill are investigated in some detail. Almost all milling parameters are summarised in a single factor—total effective impact energy. Furthermore, the MC kinetic between calcium oxide/Al and hexachlorobenzene is well established and modelled. The results indicate that total effective impact energy and reagent ratio are the two factors sufficient for describing the MC degradation degree of POPs. The reaction rate constant only depends on the chemical properties of reactants, so it could be used as an important index to appraise the quality of MC additives. This model successfully predicts the reaction rate for different operating conditions, indicating that it could be suitably applied for conducting MC reactions in other reactors.

•The chloride ions contained in fly ash negatively influence upon PCDD/Fs-degradation during MCD.•A novel additive, a mix of calcium oxide and aluminium metal, was proposed.•Dechlorination is the major mechanism for PCDD/Fs degradation and CaO-Al promotes the degradation of PCDD.Mechanochemical dechlorination and destruction of polychlorinated dibenzo-p-dioxins and -furans (PCDD/F) on fly ash from Municipal Solid Waste Incineration was tested with and without additives (CaO and CaO/aluminium powder). The first results disappointed because of obvious PCDD/F-reformation and a second test series was conducted after removing soluble salts (NaCl, KCl …) by thorough two-stage water washing. This second test series was successful and demonstrated good destruction results, especially with combined CaO/aluminium powder as additive. In a third test series salt was again added to the water-washed fly ash, and the first, poor results were largely reconstituted. For all tests a fairly complete (94 out of 136 congeners) isomer-specific analysis was conducted and analysed, allowing to differentiate between, e.g., 2,3,7,8-substituted PCDD/F and congeners formed following the chlorophenol route. The first became more important in the samples series Fly Ash, Milled Fly Ash, milling with added CaO, and milling with CaO/aluminium-addition. The second follow the opposite trend. This isomer-specific analysis will form the basis for further study using Principal Component Analysis.

Municipal solid waste incineration (MSWI) fly ash has been classified as hazardous waste and needs treatment in an environmentally safe manner. Mechanochemical (MC) treatment is such a detoxification method, since it destroys dioxins and solidifies heavy metals. Milling, however, also introduces supplemental metals (Fe, Ni, Cr, Mn…), following wear of both steel balls and housing. Milling moreover reduces the particle size of fly ash and disperses catalytic metal, potentially rising the reactivity of fly ash to form and destroy ‘dioxins’, i.e. polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD + PCDF or PCDD/F). To test this issue, model fly ash (MFA) samples were composed by mixing of silica, sodium chloride, and activated carbon, and doped with CuCl2. Then, these samples were first finely milled without any additives for 0 h (original sample), 1 h and 8 h, and the effect of milling time (and hence particle size) was investigated on the formation of polycyclic aromatic hydrocarbons (PAHs), and of polychlorinated phenols (CP), benzenes (CBz), biphenyls (PCB) and dioxins (PCDD + PCDF) during de novo tests at 300 °C for 1 h, thus simulating the conditions prevailing in the post-combustion zone of an incinerator, where dioxins are formed and destroyed. These compounds are all characterized by their rate of generation (ng/g MFA) and their signature, i.e. internal distribution over congeners as a means of gathering mechanistic indications. PAH and CBz total yield did not decrease in MC treated MFA with milling time, while total pentachlorophenol (PeCP), PCB and PCDD/F yield decreased up to 86, 94 and 97%, respectively. International Toxic Equivalents (I-TEQ) concentration decreased more than 90%, while degree of chlorination varied inconsistently for PCB and PCDD/F, and average congener patterns of PCDD/F do not vary considerably with milling time for both gas and solid phase.

In this study, a reliable and steady PCDD/F generation system was utilized to investigate the performance of catalysts, in which 130 congeners of tetra- to octapolychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) vapors were studied under simulated flue gas with/without O3. TiO2 and carbon nanotubes (CNTs) supported vanadium oxides (VOX/TiO2–CNTs) modified with MnOX and CuOX, which were reported to be beneficial to the decomposition of model molecules, were found to have a negative effect on the removal of real PCDD/Fs in the simulated flue gas without O3. Moreover, the addition of MnOX presented different effects depending on whether CuOX existed in catalysts or not, which was also contrary to its effects on the degradation of model molecules. In an O3-containing atmosphere, low chlorination level PCDD/Fs congeners were removed well over VOX-MnOX/TiO2–CNTs, while high chlorination level PCDD/Fs congeners were removed well over VOX-CuOX/TiO2–CNTs. Fortunately, all PCDD/Fs congeners decomposed well over VOX-MnOX-CuOX/TiO2–CNTs. Finally, the effects of tetra- to octachlorination level for the adsorption and degradation behaviors of PCDD/Fs congeners were also investigated.

Cationic emulsified asphalt (CEA) and poly(vinyl alcohol) (PVA) polymer binding agents may affect the combustion characteristics and pollutant emissions of coal logs shaped for transportation in hydraulic pipelines. Therefore, these characteristics were investigated using thermal analysis as well as a lab-scale fixed-bed combustor, together with those of raw coals. Three raw coals, anthracite, bitumite, and lignite, were selected to produce coal logs. The results of thermal analysis were compared to those of raw coals. Binders made the three coals more prone to be ignited. Binders improved the combustion of coal logs made of anthracite yet worsened the combustion performance of bitumite coal logs. CEA binder ameliorated the combustion performance of coal logs made of lignite. PVA binder slightly worsened the combustion performance of coal logs made of lignite. Different binders had dissimilar effects on the pollutant emissions when burning coal logs made of different coals.

It is of great interest and importance to have a comprehensive understanding of the characteristics of tar derived from major components of municipal solid waste to guide gasification syngas cleaning and upgrading. In this paper, cellulose and polyvinyl chloride (PVC) were chosen as principle components, and the surface tension, kinematic viscosity, and contact angle of tar derived from cellulose, PVC, and their mixture at temperatures of 400, 500, and 600 °C were experimentally studied. Gas chromatography–mass spectrometry (GC–MS) and 13C nuclear magnetic resonance (NMR) were employed to identify major tar species and their corresponding molecular bonds. Results indicated that the surface tension increased from around 51.4, 41.4, and 58.6 mN/m at 400 °C to 54.8, 47.2, and 64.9 mN/m at 600 °C for cellulose, PVC, and their mixture, respectively. Correspondingly, the kinematic viscosity changed from around 5.64, 20.37, and 10.37 cSt to 10.35, 34.21, and 15.51 cSt. The surface tension was affected by the co-pyrolysis of cellulose and PVC, while no obvious interaction was observed for kinematic viscosity. GC–MS results showed that the major species of tar generated from cellulose were miscellaneous hydrocarbons with a proportion between 69.7 and 96.3%. The composition for tar derived from PVC and their mixture showed a dramatic difference compared to that from cellulose. NMR spectra indicated that the function group of tar derived from the PVC and cellulose mixture was dominated by PVC.

•A Laval nozzle arc discharge as plasma generation source.•Its special geometry leads to high ionization degree and plasma density.•It features low energy consumption and good conversion.•Hydrogen production by ammonia decomposition via plasma was innovative studied.The production of hydrogen from hydrogen compounds for fuel cell or internal combustion engine applications is a potential method for responding to the energy crisis and environmental problems. In this work carbon dioxide reforming of methane and decomposition of ammonia using a Laval nozzle arc discharge (LNAD) reactor has been exploited at atmospheric pressure without external heating or catalysts. CH4 (or NH3) conversion and H2 selectivity were observed to be negatively correlated with the concentration of CH4 (or NH3) and the flux of CO2 (N2) and positively correlated with voltage and the Laval nozzle throat radius. Power consumption increased with the concentration of methane at the same CO2 flow rate, and the conversion of methane gradually increased with the content of water vapor in the gas mixture. A high conversion rate and fair H2 selectivity were achieved, 51% and 37.5%, respectively, when the methane and carbon dioxide flow rates were 4 L/min and 14 L/min, respectively, and the minimum distance between the two electrodes was 2.5 mm. The LNAD reactor used in this study exhibited a good conversion rate and low energy consumption, which should be suitable for the industrial scale-up of the system.

The experimental test of co-incinerating Chinese raw municipal solid waste (MSW) and coal in a laboratory-scale tubular reactor was first reported in present study, and the emission of normal gas components and the effects of the S/Cl molar ratio or coal mixing percentages on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs) emission were investigated and discussed. The results indicated that OCDD was the only PCDD homologues since others like TCDD-HpCDD was hardly detected, while as the categories of PCDF homologues were comparatively much more general. The amount of PCDD was much larger than that of PCDF in all operating conditions. Since ∑PCDF/∑PCDD<<1, the dominant role of the precursor formation was proven in our experimental conductions. With increasing the coal addition to MSW (from 0 to 16%), PCDD and PCDF were reduced considerably. Coal and MSW may suppress the PCDD/F emissions efficiently (over 95%) during the MSW incineration process. The PCDD/F suppression results of the present study could be helpful guidance to the industrial application of Chinese MSW and auxiliary coal co-incineration processes. The PCDD/F stack emission data of two industrial incinerators using co-incineration technology in China seem to have a great positive reduction of PCDDs/Fs.

Chlorine source is indispensable for polychlorinated dibenzo-p-dioxin and furan (PCDD/F) formation during municipal solid waste (MSW) incineration. Inorganic chlorine compounds were employed in this study to investigate their effects on PCDD/F formation through heterogeneous synthesis on fly ash surfaces. A fly ash sample obtained from a fluidized bed incinerator was sieved to different size fractions which served as the PCDD/F formation sources. The capability of different metal chlorides which facilitate the formation of PCDDs/Fs was found to follow the trends: Na < Mg < K < Al < Ca, when two particle fractions of >177 μm and 104–125 μm were used in the experiments. However, the capability of NaCl, MgCl2 and KCl did not seem much different from each other, whereas CaCl2and AlCl3 were much more active in PCDD/F formation. NaCl and MgCl2 were relatively effective to produce more PCDDs, while KCl, AlCl3 and CaCl2 generated more PCDFs during heterogeneous reactions occurring on fly ash. 2,3,7,8-TCDF was the most significant contributor to the toxicity of the PCDDs/Fs formed from inorganic chlorine sources. Decreasing the sizes of fly ash particles led to more active formation of PCDDs/Fs when NaCl was used as inorganic chlorine in the experiment. The highest PCDDs/Fs produced from particles with size <37 μm, while the lowest PCDDs/Fs produced from particles with size >177 μm. The toxicity generally increased with decreasing size of the fly ash particles. The formation of PCDDs was mainly facilitated by the two size fractions, 104–125 μm and <37 μm, while the formation of PCDFs was favored by the two other size fractions, >177 μm and 53–104 μm.