Use of municipal solid waste incineration fly ash as a supplementary cementitious material: CO2 mineralization coupled with mechanochemical pretreatment.

The use of municipal solid waste incineration fly ash, commonly referred to as "fly ash", as a supplementary cementitious material (SCM), has been explored to mitigate the CO2 emissions resulting from cement production. Nevertheless, the incorporation of fly ash as an SCM in mortar has been shown to weaken its compressive strength and increase the risk of heavy metal leaching. In light of these challenges, this study aims to comprehensively evaluate the influence of CO2 pressure, temperature, and residual water/binder ratio on the CO2 uptake and compressive strength of mortar when combined with fly ash. Additionally, this study systematically examines the feasibility of mechanochemical pretreatment, which enhances the homogenization of fly ash and augments the density of the mortar's microstructure. The results indicate that the use of mechanochemical pretreatment leads to a notable 43.6% increase in 28-day compressive strength and diminishes the leaching of As, Ba, Ni, Pb, Se, and Zn by 17.9-77.8%. Finally, a reaction kinetics model is proposed to elucidate the CO2 sequestration process under varying conditions. These findings offer valuable guidance for incorporating fly ash as an SCM and CO2 sequestrator in mortar.

PCDD/F adsorption enhancement over nitrogen-doped biochar: A DFT-D study.

Polychlorinated dibenzo-p-dioxin/furans (PCDD/F) have a great threat to the environment and human health, resulting in controlling PCDD/F emissions to regulation far important for emission source. Considering 2,3,4,7,8-pentachlorodibenzo-p-furan (PeCDF) identified as the most contributor to international toxic equivalent, 2,3,4,7,8-PeCDF can be considered as the target molecule for the adsorption of PCDD/F emission from industries. With the aim to in-depth elucidate how different types of nitrogen (N) species enhance 2,3,4,7,8-PeCDF on the biochar and guide the specific carbon materials design for industries, systematic computational investigations by density functional theory calculations were conducted. The results indicate pristine biochar intrinsically interacts with 2,3,4,7,8-PeCDF by π-π electron donor and acceptor (EDA) interaction, six-membered carbon rings of PeCDF parallel to the biochar surface as the strongest adsorption configuration. Moreover, by comparison of adsorption energy (-150.16 kJ mol-1) and interaction distance (3.593 Å) of pristine biochar, environment friendly N doping can enhance the adsorption of 2,3,4,7,8-PeCDF on biochar. Compared with graphitic N doping and pyridinic N doping, pyrrolic N doping biochar presents the strongest interaction toward 2,3,4,7,8-PeCDF molecule due to the highest adsorption energy (-155.56 kJ mol-1) and shortest interaction distance (3.532 Å). Specially, the enhancing adsorption of PeCDF over N doped biochar attributes to the enhancing π-π electron EDA interaction and electrostatic interaction. In addition, the effect of N doping species on PeCDF adsorbed on the biochar is more than that of N doping content. Specially, the adsorption capacity of N doping biochar for PCDD/F can be improved by adding pyrrolic N group most efficiently. Furthermore, pyrrolic N and pyridinic N doping result in the entropy increase, and electrons transform from pyrrolic N and pyridinic N doped biochar to 2,3,4,7,8-PeCDF molecule. A complete understanding of the research would supply crucial information for applying N-doped biochar to effectively remove PCDD/F for industries.

Designing low-carbon cement-free binders for stabilization/solidification of MSWI fly ash.

Low-carbon and high-efficiency binder is desirable for sustainable treatment of municipal solid waste incineration fly ash (MSWI FA). In this study, CaO or MgO was used to activate ground granulated blast furnace slag (GGBS) to form calcium silicate hydrate and magnesium silica hydrate gel for stabilization/solidification of hazardous MSWI FA. Experimental results showed that potential toxic elements (PTEs), such as Pb and Zn, significantly inhibited the formation of reaction products in CaO-GGBS system due to the complexation between Ca(OH)2 and PTEs, whereas PTEs only had insignificant inhibition on transformation from MgO to Mg(OH)2 in MgO-GGBS system, resulting in lower leachabilities of PTEs and higher mechanical strengths. Stabilization/solidification experiments demonstrated that MSWI FA (70 wt%) could be recycled by MgO-GGBS binder (30 wt%) into blocks with desirable 28-day compressive strengths (3.9 MPa) and PTEs immobilization efficiencies (99.8% for Zn and 99.7% for Pb). This work provides mechanistic insights on the immobilization mechanisms of PTEs in CaO/MgO-GGBS systems and suggests a promising MgO-GGBS binder for low-carbon treatment of MSWI FA.

Green photoreduction synthesis of dispersible gold nanoparticles and their direct in situ assembling in multidimensional substrates for SERS detection.

Gold nanoparticles (AuNPs) and their composites have been applied in surface-enhanced Raman scattering (SERS) detection methods, owing to their stable and excellent surface plasmon resonance. Unfortunately, methods for synthesizing AuNPs often require harsh conditions and complicated external steps. Additionally, removing residual surfactants or unreacted reductants is critical for improving the sensitivity of SERS detection, especially when employing AuNPs-assembled multidimensional substrates. In this study, we propose a simple and green method for AuNPs synthesis via photoreduction, which does not require external surfactant additives or stabilizers. All the processes were completed within 20 min. Along this way, only methanol was employed as the electron acceptor. Based on this photoreduction synthesis strategy, AuNPs can be directly and circularly assembled in situ in multidimensional substrates for SERS detection. The removal of residual methanol was easy because of its low boiling point. This strategy was employed for the preparation of three different dimensional SERS substrates: filter paper@AuNPs, g-C3N4@AuNPs, and MIL-101(Cr)@AuNPs. The limit of detection of filter paper@AuNPs for thiabendazole SERS detection was 1.0 × 10-7 mol/L, while the limits of detection of g-C3N4@AuNPs and MIL-101(Cr)@AuNPs for malachite green SERS detection were both 5.0 × 10-11 mol/L. This strategy presents potential in AuNP doping materials and SERS detection.

Stable and Effective Online Monitoring and Feedback Control of PCDD/F during Municipal Waste Incineration.

For the long-term operation of municipal solid waste incineration (MSWI), online monitoring and feedback control of polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) can be used to control the emissions to national or regional standards. In this study, 500 PCDD/F samples were determined by thermal desorption gas chromatography coupled to tunable-laser ionization time-of-flight mass spectrometry (TD-GC-TLI-TOFMS) for 168 h. PCDD/F emissions range from 0.01 ng I-TEQ/Nm3 to 2.37 ng I-TEQ/Nm3, with 44% of values below 0.1 ng I-TEQ/Nm3 (the national standard). In addition, the temperature of the furnace outlet, bed pressure, and oxygen content are considered as key operating parameters among the 13 operating parameters comprising four temperature parameters, four pressure parameters, four flow parameters, and oxygen content. More specifically, maintaining the furnace outlet temperature to be higher than 800 °C, or bed pressure higher than 13 kPa, or the oxygen content stably and above 10% are effective methods for reducing PCDD/F emissions. According to the analysis of the Pearson coefficients and maximal information coefficients, there is no significant correlation between operating parameters and PCDD/F I-TEQ. Only when there is a significant change in one of these factors will the PCDD/F emissions also change accordingly. The feedback control of PCDD/F emissions is realized by adjusting the furnace outlet temperature, bed temperature, and bed pressure to control the PCDD/F to be less than 0.1 ng I-TEQ/Nm3.

Low-Temperature Catalytic Decomposition of 130 Tetra- to Octa-PCDD/Fs Congeners over CuOX and MnOX Modified V2O5/TiO2-CNTs with the Assistance of O3.

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.

Municipal solid waste incineration in China and the issue of acidification: A review.

In China, incineration is essential for reducing the volume of municipal solid waste arising in its numerous megacities. The evolution of incinerator capacity has been huge, yet it creates strong opposition from a small, but vocal part of the population. The characteristics of Chinese municipal solid waste are analysed and data presented on its calorific value and composition. These are not so favourable for incineration, since the sustained use of auxiliary fuel is necessary for ensuring adequate combustion temperatures. Also, the emission standard for acid gases is more lenient in China than in the European Union, so special attention should be paid to the issue of acidification arising from flue gas. Next, the techniques used in flue gas cleaning in China are reviewed and the acidification potential by cleaned flue gas is estimated. Still, acidification induced by municipal solid waste incinerators remains marginal compared with the effects of coal-fired power plants.

Influence of temperature and atmosphere on polychlorinated dibenzo-p-dioxins and dibenzofurans desorption from waste incineration fly ash.

A fly ash sample was heated for 1 h to 200°C, 300°C and 400°C, in order to study the influence of temperature and gas phase composition on the removal of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from fly ash derived from municipal solid waste incineration. The tests were conducted by treating a fixed bed of fly ash both in an inert (nitrogen) and in a reducing (nitrogen+hydrogen) gas flow in a horizontal bench-scale quartz tubular reactor, heated by a surrounding tubular furnace. The results indicate that most of the PCDD/Fs in fly ash were removed by thermal treatment, especially when the temperature was higher than 300°C: the PCDD/Fs' removal efficiency attained up to 96%. PCDD/Fs dechlorination and destruction were much more important than PCDD/Fs desorption, under either inert or reducing atmosphere. At 200°C and 300°C, the experiments with reducing atmosphere yielded slightly better results than those in nitrogen; yet, this tendency was reversed at 400°C. In general, both treatment modes can fully meet the requirements regarding the concentration of dioxins in fly ash to be sent for landfill in China.

Dioxins from medical waste incineration: Normal operation and transient conditions.

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are key pollutants in waste incineration. At present, incinerator managers and official supervisors focus only on emissions evolving during steady-state operation. Yet, these emissions may considerably be raised during periods of poor combustion, plant shutdown, and especially when starting-up from cold. Until now there were no data on transient emissions from medical (or hospital) waste incineration (MWI). However, MWI is reputed to engender higher emissions than those from municipal solid waste incineration (MSWI). The emission levels in this study recorded for shutdown and start-up, however, were significantly higher: 483 ± 184 ng Nm(-3) (1.47 ± 0.17 ng I-TEQ Nm(-3)) for shutdown and 735 ng Nm(-3) (7.73 ng I-TEQ Nm(-3)) for start-up conditions, respectively. Thus, the average (I-TEQ) concentration during shutdown is 2.6 (3.8) times higher than the average concentration during normal operation, and the average (I-TEQ) concentration during start-up is 4.0 (almost 20) times higher. So monitoring should cover the entire incineration cycle, including start-up, operation and shutdown, rather than optimised operation only. This suggestion is important for medical waste incinerators, as these facilities frequently start up and shut down, because of their small size, or of lacking waste supply. Forthcoming operation should shift towards much longer operating cycles, i.e., a single weekly start-up and shutdown.

Migration and distribution characteristics of typical organic pollutants in condensable particulate matter of coal-fired flue gas and by-products of wet flue gas desulfurization system.

The wet flue gas desulfurization (WFGD) system of coal-fired power plants shows a good removal effect on condensable particulate matter (CPM), reducing the dust removal pressure for the downstream flue gas purification devices. In this work, the removal effect of a WFGD system on CPM and its organic pollutants from a coal-fired power plant was studied. By analyzing the organic components of the by-products emitted from the desulfurization tower, the migration characteristics of organic pollutants in gas, liquid, and solid phases, as well as the impact of desulfurization towers on organic pollutants in CPM, were discussed. Results show that more CPM in the flue gas was generated by coal-fired units at ultra-low load, and the WFGD system had a removal efficiency nearly 8% higher than that at full load. The WFGD system had significant removal effect on two typical esters, especially phthalate esters (PAEs), with the highest removal efficiency of 49.56%. In addition, the WFGD system was better at removing these two esters when the unit was operating at full load. However, it had a negative effect on n-alkanes, which increased the concentration of n-alkanes by 8.91 to 19.72%. Furthermore, it is concluded that the concentration distribution of the same type of organic pollutants in desulfurization wastewater was similar to that in desulfurization slurry, but quite different from that in coal-fired flue gas. The exchange of three organic pollutants between flue gas and desulfurization slurry was not significant, while the concentration distribution of organic matters in gypsum was affected by coal-fired flue gas.

Physicochemical properties, mechanism of action of lycopene and its application in poultry and ruminant production.

Lycopene is a kind of natural carotenoid that could achieve antioxidant, anti-cancer, lipid-lowering and immune-improving effects by up-regulating or down-regulating genes related to antioxidant, anti-cancer, lipid-lowering and immunity. Furthermore, lycopene is natural, pollution-free, and has no toxic side effects. The application of lycopene in animal production has shown that it could improve livestock production performance, slaughter performance, immunity, antioxidant capacity, intestinal health, and meat quality. Therefore, lycopene as a new type of feed additive, has broader application prospects in many antibiotic-forbidden environments. This article serves as a reference for the use of lycopene as a health feed additive in animal production by going over its physical and chemical characteristics, antioxidant, lipid-lowering, anti-cancer, and application in animal production.

Synthesis of layered double hydroxides from municipal solid waste incineration fly ash for heavy metal adsorption.

The process of urbanization has resulted in a continuous growth of the production of municipal solid waste, consequently leading to the increase of municipal solid waste incineration fly ash (MSWI FA) over time. This has prompted the need for effective disposal and value-added utilization strategies for MSWI FA. In this study, a hydrothermal method was employed to synthesize CaAl layered double hydroxides (LDHs) using MSWI FA as the raw material. The main objective was to investigate how different synthesis parameters affect the crystallinity of the layered bimetallic hydroxides. Subsequently, the synthesized LDHs were characterized using various techniques such as BET, SEM, XRD, FT-IR, and XPS. The results revealed the presence of calcium and aluminum cations in the interlayer region of the synthesized material, with chloride ions, sulfate ions, and acetate ions being the predominant anions. Moreover, the formation of LDHs presents an effective approach for the self-purification of leachates derived from MSWI FA. The LDHs exhibited excellent adsorption capacity for Cd2+ and Cu2+ in wastewater, with maximum values of 730 mg·g-1 and 446 mg·g-1, respectively. The adsorption mechanisms involved isomorphous substitution, complexation, as well as the precipitation of hydroxides or interlayer anions. This method presents a novel approach for effectively utilizing MSWI FA to produce environmentally friendly value-added adsorbents.

Effects of Black Soldier Fly (Hermetia illucens L., BSF) Larvae Addition on In Vitro Fermentation Parameters of Goat Diets.

The purpose of this experiment was to evaluate the effects of different levels of BSF on rumen in vitro fermentation gas production, methane (CH4) production, ammonia nitrogen (NH3-N), and volatile fatty acids (VFAs). The experiment comprised four treatments, each with five replicates. The control group contained no BSF (BSF0), and the treatment groups contained 5% (BSF5), 10% (BSF10), and 15% (BSF15) BSF, respectively. Results showed that at 3 h, 9 h, and 24 h, gas production in BSF5 and BSF10 was significantly higher than in BSF0 and BSF15 (p < 0.05). Gas production in BSF5 and BSF10 was higher than in BSF0, while gas production in BSF15 was lower than in BSF0. At 6 h and 12 h, CH4 emission in BSF15 was significantly lower than in the other three groups (p < 0.05). There were no differences in the pH of in vitro fermentation after BSF addition (p > 0.05). At 3 h, NH3-N levels in BSF10 and BSF15 were significantly higher than in BSF0 and BSF5 (p < 0.05). At 6 h, NH3-N levels in BSF5 and BSF10 were significantly higher than in BSF0 and BSF15 (p < 0.05). Acetic acid, propionic acid, butyric acid, and total VFAs in BSF0, BSF5, and BSF10 were significantly higher than in BSF15 (p < 0.05). In conclusion, gas production, CH4 emission, NH3-N, acetic acid, propionic acid, butyric acid, and VFAs were highest in BSF5 and BSF10 and lowest in BSF15.

New mechanistic insight into catalytic decomposition of dioxins over MnOx-CeO2/TiO2 catalysts: A combined experimental and density functional theory study.

Elucidation of the catalytic decomposition mechanism of dioxins is pivotal in developing highly efficient dioxin degradation catalysts. In order to accurately simulate the whole molecular structure of dioxins, two model compounds, o-dichlorobenzene (o-DCB) and furan, were employed to represent the chlorinated benzene ring and oxygenated central ring within a dioxin molecule, respectively. Experiments and Density Functional Theory (DFT) calculations were combined to investigate the adsorption as well as oxidation of o-DCB and furan over MnOx-CeO2/TiO2 catalyst (denoted as MnCe/Ti). The results indicate that competitive adsorption exists between furan and o-DCB. The former exhibits superior adsorption capacity on MnCe/Ti catalyst at 100 °C - 150 °C, for it can adsorb on both surface metal atom and surface oxygen vacancies (Ov) via its O-terminal; while the latter adsorbs primarily by anchoring its Cl atom to surface Ov. Regarding oxidation, furan can be completely oxidized at 150 °C - 300 °C with a high CO2 selectivity (above 80 %). However, o-DCB cannot be totally oxidized and the resulting intermediates cause the deactivation of catalyst. Interestingly, the pre-adsorption of furan on catalyst surface can facilitate the catalytic oxidation of o-DCB below 200 °C, possibly because the dissociated adsorption of furan may form additional reactive oxygen species on catalyst surface. Therefore, this work provides new insights into the catalytic decomposition mechanism of dioxins as well as the optimization strategies for developing dioxin-degradation catalysts with high efficiency at low temperature.

Effects of black soldier fly larvae (Hermetia illucens L.) as feed supplements on muscle nutrient composition, meat quality, and antioxidant capacity in Qianbei goat.

Objective: Black soldier fly (BSF) as an animal protein feed source is currently becoming a research hot topic. This study investigated the effects of the BSF as a protein feed source for goats on slaughter performance, muscle nutrient composition, amino acids, fatty acids, minerals, and antioxidant levels. Methods: Thirty Qianbei Ma goats (20.30 ± 1.09 kg) were randomly divided into three groups: the control group (GRPC) supplemented with 10% full-fat soybean, treatment 1 (GRPU) supplemented with 10% untreated BSF, and treatment 2 (GRPT) supplemented with 10% heat-treated BSF. One-way ANOVA among groups (with Fisher's least significant difference (LSD) post hoc comparison) was used in this study. Results: The nutrients, amino acids, fatty acids, minerals, and antioxidants in muscle were analyzed. The results showed that there were no significant differences in the moisture, dry matter (DM), crude protein (CP), ash, amino acids, and mineral content of the muscles among the three feeding groups. The slaughter rate and carcass weight of the GRPU and GRPT groups were significantly lower (p<0.05). The overall meat quality of the GRPU and GRPT groups decreased (p<0.05). The individual unsaturated fatty acids and total unsaturated fatty acids in the GRPU group were higher (p<0.05) than those in the GRPC and GRPT groups. Both GRPU and GRPT decreased (p<0.05) the antioxidant capacity of the meat. Conclusion: Therefore, the heat-treated BSF had a better effect on meat quality compared to untreated BSF, but there were greater negative effects on the meat quality of GRPU and GRPT than GRPC.

Study of PCDD/Fs distribution in fly ash, ash deposits, and bottom ash from a medical waste incinerator in China.

UNLABELLED: Over the past decades in China, the number of medical waste incinerators (MWIs) has been rising rapidly, causing emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). In this study, samples of fly ash, ash deposits, and bottom ash from typical MWIs were analyzed for PCDD/Fs and their distribution characteristics. Results showed international toxic equivalent (I-TEQ) values in the range of 6.9-67 ng I-TEQ/g in fly ash and ash deposits, whereas the concentration in bottom ash was extremely low (only 1.33 pg I-TEQ/g), yet the generation of PCDD/Fs was mostly de novo synthesis in fly ash and ash deposits according to the ratio of PCDFs to PCDDs; the major distribution differences of PCDD/Fs in fly ash was manifested by the content of toxic furan 2,3,7,8-TCDF but other toxic PCDD/Fs showed similar distribution. Other findings are that 2,3,4,7,8-PeCDF had the most contribution to TEQ concentration, and that the most abundant toxic furan congener is 1,2,3,4,6,7,8-HpCDF. Correlation analysis showed that there was no significant correlation between PCDD/Fs concentration and several other physical and chemical parameters. IMPLICATIONS: This paper is of interest because it presents the emission performances of PCDD/Fs in ash from medical waste incineration in China. PCDD/F contents in fly ash and ash deposits vary between 6.9 and 67.3 ng I-TEQ/g. However, the concentration in bottom ash was extremely low (only 1.33 x 10(-3) ng I-TEQ/g). The fingerprints of PCDD/Fs in fly ash are almost similar, except for 2,3,7,8-TCDF. There is no marked correlation between PCDD/Fs and other physicochemical properties.

Activated carbon treatment of municipal solid waste incineration flue gas.

Activated carbon injection is widely used to control dioxins and mercury emissions. Surprisingly little attention has been paid to its modelling. This paper proposes an expansion of the classical Everaerts-Baeyens model, introducing the expression of fraction of free adsorption sites, f (s), and asserting the significant contribution of fly ash to dioxins removal. Moreover, the model monitors dioxins partitioning between vapour and particulate phase, as well as removal efficiency for each congener separately. The effects of the principal parameters affecting adsorption are analysed according to a semi-analytical, semi-empirical model. These parameters include temperature, contact time during entrained-flow, characteristics (grain-size, pore structure, specific surface area) and dosage of activated carbon, lignite cokes or mineral adsorbent, fly ash characteristics and concentration, and type of incinerator plant.

Atmospheric emission characterization of a novel sludge drying and co-combustion system.

A novel system combining sludge drying and co-combustion with coal was applied in disposing sludge and its atmospheric emission characteristics were tested. The system was composed of a hollow blade paddle dryer, a thermal drying exhaust gas control system, a 75 tons/hr circulating fluidized bed and a flue gas cleaning system. The emissions of NH3, SO2, CH4 and some other pollutants released from thermal drying, and pollutants such as NOx, SO2 etc. discharged by the incinerator, were all tested. Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in the flue gas from the incinerator were investigated as well. The results indicated that the concentrations of NOx and SO2 in the flue gas from the incinerator were 145 and 16 mg/m3, respectively. and the I-TEQ concentration of 2,3,7,8-substitued PCDD/Fs was 0.023 ng I-TEQ/Nm3. All these values were greatly lower than the emission standards of China. In addition, there was no obvious odor in the air around the sludge dryer. The results demonstrated that this drying and co-combustion system is efficient in controlling pollutants and is a feasible way for large-scale treatment of industrial sludge and sewage sludge.

Removal of PCDD/Fs and PCBs from flue gas using a pilot gas cleaning system.

A 100 Nm3/hr capacity pilot scale dual bag filter (DBF) system was tested on the flue gas from an actual hazardous waste incinerator (HWI), the removal efficiency of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) was also studied. The first filter collected most of the fly ash and associated chlorinated organic; then activated carbon (AC) was injected and used to collect phase chlorinated organic from the gas. Concentrations of PCDD/Fs and PCBs after the DBF system were 0.07 and 0.01 ng TEQ/Nm3, respectively, which were both far below the national emission standard. Comparing with the original single bag filter system, the PCDD/Fs concentration dropped a lot from 0.36 to 0.07 ng TEQ/Nm3. Increasing AC feeding rate enhanced their collection efficiency, yet reduced the AC utilization efficiency, and it still needs further study to select an appropriate feeding rate in the system. These results will be useful for industrial application and assist in controlling emissions of PCDD/Fs and other persistent organic pollutions from stationary sources in China.

Adsorption of multicomponent VOCs on various biomass-derived hierarchical porous carbon: A study on adsorption mechanism and competitive effect.

Biomass-derived porous carbon materials are potential adsorbents for VOCs. In this work, biomass-derived nitrogen-doped hierarchical porous carbons (NHPCs) were synthesized by a one-step pyrolysis activation combined with nitrogen doping method from several biomass wastes (corn straw, wheat stalk, bamboo, pine, and corncob). NHPCs have a hierarchical porous structure with micro-meso-macropores distribution, nitrogen doping, large specific surface area, and pore volume. The corncob derived carbon (NHPC-CC) has the best activation result as analyses showed that a lower ash content and higher total cellulose composition content of the biomass result in a better pore activation effect. Single and multi-component dynamic adsorption tests of typical VOCs (benzene, toluene, and chlorobenzene) were conducted on NHPCs in laboratory conditions (∼500 ppm). Promising VOC adsorption capacity and great adsorption kinetics with low mass transfer resistance were found on NHPCs. Correlation analysis showed that the high VOC adsorption capacity and great adsorption kinetics can be attributed to the large surface area of micro-mesopores and the mass transfer channels provided by meso-macropores respectively. The competitive dynamic adsorption tests revealed that the VOC with lower saturated vapor pressure has more adsorption sites on the surface of micro-mesopores and stronger adsorption force, which results in the higher adsorption capacity and desorption caused by substitution reaction in VOCs competitive adsorption process. In detail, the process of toluene and chlorobenzene competitive adsorption was described. Besides, well recyclability of NHPC-CC was revealed as the VOCs adsorption capacity reductions were less than 10% after four adsorption-desorption cycles. All studies showed that the NHPC-CC could be potential adsorbent for VOCs in industrial process.