Synergistic catalytic removal of NOx and chlorinated organics through the cooperation of different active sites

The synergistic removal of NOx and chlorinated volatile organic compounds (CVOCs) has become the hot topic in the field of environmental catalysis. However, due to the trade-off effects between catalytic reduction of NOx and catalytic oxidation of CVOCs, it is indispensable to achieve well-matched redox property and acidity. Herein, synergistic catalytic removal of NOx and chlorobenzene (CB, as the model of CVOCs) has been originally demonstrated over a Co-doped SmMn2O5 mullite catalyst. Two kinds of Mn-Mn sites existed in Mn-O-Mn-Mn and Co-O-Mn-Mn sites were constructed, which owned gradient redox ability. It has been demonstrated that the cooperation of different active sites can achieve the balanced redox and acidic property of the SmMn2O5 catalyst. It is interesting that the d band center of Mn-Mn sites in two different sites was decreased by the introduction of Co, which inhibited the nitrate species deposition and significantly improved the N2 selectivity. The Co-O-Mn-Mn sites were beneficial to the oxidation of CB and it cooperates with Mn-O-Mn-Mn to promote the synergistic catalytic performance. This work paves the way for synergistic removal of NOx and CVOCs over cooperative active sites in catalysts.

Advancing nuanced pollution control: Local improvements and spatial spillovers of policies on key enterprises

This paper examines the impact of air pollution control policies targeting key polluting enterprises, highlighting a strategic shift towards precision pollution control that concentrates on high-emission, high-risk businesses. The paper explores the efficacy of these policies and their potential spatial spillover effects, utilizing panel data from 259 Chinese cities from 2013 to 2021. Employing the difference-in-differences (DID) model and spatial Durbin model, the study analyzes both the direct local effects and the broader spatial consequences of these regulatory measures on air quality. The findings indicate a significant reduction in air pollutant concentrations in urban areas, attributing this improvement to factors such as industrial restructuring, increased investment in science and technology, and economic growth. Spatial econometric analysis further reveals a substantial positive correlation in air quality among Chinese cities. However, estimates of the spillover effect indicate that while such policies successfully reduce pollution locally, they could unintentionally degrade air quality in adjacent areas. The study highlights the need for nuanced policy strategies to mitigate unintended spatial spillovers and enhance overall effectiveness. It recommends tailored policies that integrate environmental and socioeconomic objectives, national and regional coordination for consistent enforcement, technology-driven compliance strategies, and incentives for sustainable enterprise practices.

Indoor air quality improvement with filtration and UV-C on mitigation of particulate matter and airborne bacteria: Monitoring and modeling

Indoor air, especially with suspended particulate matter (PM), can be a carrier of airborne infectious pathogens. Without sufficient ventilation, airborne infectious diseases can be transmitted from one person to another. Indoor air quality (IAQ) significantly impacts people's daily lives as people spend 90% of their time indoors. An industrial-grade air cleaner prototype (filtration + ultraviolet light) was previously upgraded to clean indoor air to improve IAQ on two metrics: particulate matter (PM) and viable airborne bacteria. Previous experiments were conducted to test its removal efficiency on PM and airborne bacteria between the inlet and treated air. However, the longer-term improvement on IAQ would be more informative. Therefore, this research focused on quantifying longer-term improvement in a testing environment (poultry facility) loaded with high and variable PM and airborne bacteria concentrations. A 25-day experiment was conducted to treat indoor air using an air cleaner prototype with intermittent ON and OFF days in which PM and viable airborne bacteria were measured to quantify the treatment effect. The results showed an average of 55% reduction of total suspended particulate (TSP) concentration between OFF days (110 μg/m3) and ON days (49 μg/m3). An average of 47% reduction of total airborne viable bacteria concentrations was achieved between OFF days (∼3200 CFU/m3) and ON days (∼2000 CFU/m3). A cross-validation (CV) model was established to predict PM concentrations with five input variables, including the status of the air cleaner, time (h), ambient temperature, indoor relative humidity, and day of the week to help simulate the air-cleaning effect of this prototype. The model can approximately predict the air quality trend, and future improvements may be made to improve its accuracy.

Role of short-term campaigns and long-term mechanisms for air pollution control: lessons learned from the "2 + 26" city cluster in China

Protecting people from air pollution is an important task for developing countries. Over the past several decades, different types of policies have been enacted in developing countries to improve air quality, with policy impact analysis being conducted as well. As for China, while there is some existing literature on the impact of short-term action on air quality, there is much less research to investigate the roles of long-term air quality control mechanism on air quality change. This paper uses the "2 + 26" city cluster in China as a case study area to particularly analyze the roles played by short-term campaigns that compose the Winter Action Plan and a long-term mechanism referred to as the environmental accountability system in pollution control. Based on econometric and descriptive statistical analyses, it is found that the implementation of the Winter Action Plan has significantly improved the air quality, and the environmental accountability system seems to have exerted an impact, as cities with better air quality appear to establish a more stringent environmental accountability system. The paper provides the following insights for other developing countries: short-term campaigns can quickly reduce pollution and protect human health, while long-term mechanisms are needed to ensure sustainable environmental protection.

Low-temperature oxidative removal of benzene from the air using titanium carbide (MXene)-Supported platinum catalysts

MXenes are an emerging class of two-dimensional (2D) inorganic materials with great potential for versatile applications such as adsorption and catalysis. Here, we describe the synthesis of a platinized titanium carbide MXene (Pt@Ti3C2) catalyst with varying amounts of platinum (0.1%-2 wt.%) for the low-temperature oxidation of benzene, an aromatic volatile organic compound often found in industrial flue gas. A 1% formulation of Pt@Ti3C2-R allowed near-complete (97%) oxidation of benzene to CO2 at 225 °C with a steady-state reaction rate (r) of 0.119 mol g-1·h-1. This low-temperature catalytic oxidation reaction was promoted by an increase in the lattice oxygen (O*)/Pt2+ species (active sites) of 1%Pt@Ti3C2-R from 45.3/34.6% to 71.0/61.1% through pre-thermal reduction under H2 flow, as revealed by X-ray photoelectron spectroscopy, temperature-programmed reduction, and in situ diffuse reflectance infrared Fourier transform spectroscopy analyses. The cataltyic activity of 1% Pt@Ti3C2-R against benzene was assessed under the control of the key process variables (e.g., catalyst mass, flow rate, benzene concentration, relative humidity, and time-on-stream) to help optimize the oxidation reaction process. The results provide new insights into the use of platinum-based 2D MXene catalysts for low-temperature oxidative removal of benzene from the air.

What is the role of interface in the catalytic elimination of multi-carbon air pollutants?

Multi-carbon air pollutants pose serious hazards to the environment and health, especially soot and volatile organic compounds (VOCs). Catalytic oxidation is one of the most effective technologies for eliminating them. The oxidation of soot and most hydrocarbon VOCs begins with C-H (or edge-CH) activation, so this commonality can be targeted to design active sites. Rationally designed interface nanostructures optimize metal-support interactions (MSIs), providing suitable active sites for C-H activation. Meanwhile, the interfacial reactant spillover facilitates the further decomposition of activated intermediates. Thus, rationally exploiting interfacial effects is critical to enhancing catalytic activity. In this review, we analyzed recent advances in the following aspects: I. Understanding of the interface effects and design; II. Optimization of the catalyst-reactant contact, metal-support interface, and MSIs; III. Design of the interfacial composition and perimeter. Based on the analysis of the advances and current status, we provided challenges and opportunities for the rational design of interface nanostructures and interface-related stability. Meanwhile, a critical outlook was given on the interfacial sites of single-atom catalysts (SACs) for specific activation and catalytic selectivity.

Analysis of the dust-methane two-phase coupling blowdown effect at different air duct positions in an excavation anchor synchronous tunnel

Bolter miners are being increasingly used. Unfortunately, this mining technology causes a considerable amount of air pollution (especially by methane and dust) during excavation. In this study, the multiphase coupling field of airflow-dust-methane for different distances between the pressure air outlet and the working face (Lp) was simulated by using the FLUENT software. The migration law of pollutants in the multiphase coupling field was analyzed, and the distance parameters between the pressure air outlet and the working face were optimized. Finally, the simulation results were verified based on the field measurement results. We found that the blowdown effect was more obvious when 14 m ≤ Lp < 16 m compared with other conditions. The peak value of dust concentration within this distance range was the smallest (44.4% lower than the highest peak value, which was verified when Lp = 18 m), while the methane concentration was < 0.6%. A high-concentration area (where methane concentration > 0.75%), identified near the walking part of the bolter miner, was 13 m shorter than the largest (when Lp = 18 m). Therefore, we determined that the optimal blowdown distance would be 14 m ≤ Lp < 16 m. Within this range, the dust removal and methane dilution effects are optimal, effectively improving the tunnel air quality and providing a safe and clean environment for mine workers.

Comprehensive performance evaluation of coordinated development of industrial economy and its air pollution control

Exploring coordinated pathways that can promote not only the sustainable development of the industrial economy but also air quality is of great significance for the prevention and control of air pollution in China. Currently, the joint development pathways of the industrial economy-environment nexus remain unclear and poorly evaluated. In this study, we proposed a comprehensive performance evaluation combining objective and subjective weighting to identify industrial enterprises' economic-environment nexus benefits. It would be one of the most important steps to explore the coordinated pathways. Based on data envelopment analysis (DEA), the proposed method integrated with the index integration was used to evaluate the comprehensive performances of 41 industrial sectors in China's 13th five-year plan (2016-2020). Evaluation results showed that the comprehensive performances of the economy-environment nexus of the industrial sectors varied significantly, with the five-year average comprehensive technical efficiency (TE) of 0.11-1. Overall, the best two performances were realized by the industries of equipment manufacturing and living consumption, whereas the worst one belonged to the industry of bulk raw materials, with average comprehensive TE values of 0.50, 0.43, and 0.19, respectively. The results of the quantitative evaluation were consistent with those of the qualitative analysis in terms of the developmental status of the industrial sectors. According to the analyses of pure technical efficiency and scale effect, the proposed method identified the industrial sectors with the highest developmental value and with the highest need to control air pollution. Compared with those of the original DEA model, the results of the proposed method showed pronounced differences in terms of the performances of industrial sectors with high energy consumption and high particulate matter (PM) emissions and with low energy consumption and low PM emissions. The proposed evaluation method combining the weighting was suitable for identifying the comprehensive performance of the industrial economy-environment nexus and provides the basis for the prevention and control of air pollution.

Hydroxyl Radical-Mediated Efficient Photoelectrocatalytic NO Oxidation with Simultaneous Nitrate Storage Using A Flow Photoanode Reactor

The selective conversion of dilute NO pollutant into low-toxic product and simultaneous storage of metabolic nitrogen for crop plants remains a great challenge from the perspective of waste management and sustainable chemistry. This study demonstrates that this bottleneck can be well tackled by refining the reactive oxygen species (ROS) on Ni-modified NH2-UiO-66 (Zr) using nickel foam (Ni@NU/NF) as a three-dimensional (3D) substrate through a flow photoanode reactor via the gas-phase photoelectrocatalysis. By rationally refining the ROS to •OH, Ni@NU/NF can rapidly eliminate 82% of NO without releasing remarkable NO2 under a low bias voltage (0.3 V) and visible light irradiation. The abundant mesoporous pores on Ni@NU/NF are conducive to the diffusion and storage of the formed nitrate, which enables the progressive conversion NO into nitrate with selectivity over 99% for long-term use. Through calculation, 90% of NO could be recovered as the nitrate species, indicating that this state-of-the-art strategy can capture, enrich and recycle the pollutant N source from the atmosphere. This study offers a new perspective of NO pollutant treatment and sustainable nitrogen exploitation, which may possess great potential to the development of highly efficient air purification systems for industrial and indoor NOx control.

Effects of shared governance and cost redistribution on air pollution control: a study of game theory-based cooperation

This study seeks cost-effective strategies for PM2.5 reduction to generate insights into minimizing pollution abatement costs subject to different scenarios. This study theorizes that the cooperation of PM2.5 abatement has potential gains for participants and develop an empirical way to compare the costs and efficiency of PM2.5 abatement involving the variation of environmental conditions. This study revises the cooperative game model in the context of threshold effects using data obtained from the Beijing-Tianjin-Hebei metropolitan cluster in China. In general, the results support the key assertion that cooperation in the metropolitan cluster plays a vital role in optimizing the efficiency and costs of PM2.5 abatement. In addition to extending the application of the revised model, this study provides a way to estimate the costs and the mitigation benefits of meeting the pollution targets for each coparticipant and take the scenario of multiparty cooperation into account as well as the scenarios involving other types of pollutants. The empirical findings have important policy implications for regional shared governance, decentralization, and resource reallocation. Economic incentive-based shared governance and cost reallocation work better than traditional regulations.

Balancing acid and redox sites of phosphorylated CeO2 catalysts for NOx reduction: The promoting and inhibiting mechanism of phosphorus

The role of phosphorus in metal oxide catalysts is still controversial. The precise tuning of the acidic and redox properties of metal oxide catalysts for the selective catalytic reduction in NO_x using NH₃ is also a great challenge. Herein, CeO₂ catalysts with different degrees of phosphorylation were used to study the balance between the acidity and redox property by promoting and inhibiting effects of phosphorus. CeO₂ catalysts phosphorylated with lower phosphorus content (5 wt%) exhibited superior NO_x reduction performance with above 90% NO_x conversion during 240-420 °C due to the balanced acidity and reducibility derived from the highest content of Brønsted acid sites on PO₄^3- to adsorb NH₃ and surface adsorbed oxygen species. Plenty of PO₃^- over CeO₂ catalysts phosphorylated with the higher phosphorus content (≥ 10 wt%) significantly disrupted the balance between the acidity and the redox property due to the reduced acid/redox sites, which resulted in the less active NO_x species. The mechanism of different structural phosphorus species (PO₄^3- and PO₃^-) in promoting or inhibiting the NO_x reduction over CeO₂ catalysts was revealed. This work provides a novel method for qualitative and quantitative study of the relationship between acidity/redox property and activity of catalysts for NO_x reduction.

Formation mechanism and control strategy for particulate nitrate in China

Over the past decade, fine particulate matter (PM) pollution in China has been abated significantly, benefiting from strict emission control measures, but particulate nitrate continues to rise. Here, we review the progress in particulate nitrate (pNO₃^-) pollution characterization, nitrate formation mechanisms, and the proposed control strategies in China. The spatial and temporal distributions of pNO₃^- are summarized. The current status of knowledge on the chemical mechanism is updated, and the significance of its formation pathways is assessed by various approaches such as field observation and modelling of nitrate production rate, as well as isotopic analysis. The factors impacting pNO₃^- formation and the corresponding pollution regulation strategies are discussed, in which the importance of atmospheric oxidation capacity and ammonia are addressed. Finally, the challenges and open questions in pNO₃^- pollution control in China are outlined.

Unique Compensation Effects of Heavy Metals and Phosphorus Copoisoning over NOx Reduction Catalysts

Selective catalytic reduction (SCR) of NO_x from the flue gas is still a grand challenge due to the easy deactivation of catalysts. The copoisoning mechanisms and multipoisoning-resistant strategies for SCR catalysts in the coexistence of heavy metals and phosphorus are barely explored. Herein, we unexpectedly found unique compensation effects of heavy metals and phosphorus copoisoning over NO_x reduction catalysts and the introduction of heavy metals results in a dramatic recovery of NO_x reduction activity for the P-poisoned CeO₂/TiO₂ catalysts. P preferentially combines with Ce as a phosphate species to reduce the redox capacity and inhibit NO adsorption. Heavy metals preferentially reduced the Brønsted acid sites of the catalyst and inhibited NH₃ adsorption. It has been demonstrated that heavy metal phosphate species generated over the copoisoned catalyst, which boosted the activation of NH₃ and NO, subsequently bringing about more active nitrate species to relieve the severe impact by phosphorus and maintain the NO_x reduction over CeO₂/TiO₂ catalysts. The heavy metals and P copoisoned catalysts also possessed more acidic sites, redox sites, and surface adsorbed oxygen species, which thus contributed to the highly efficient NO_x reduction. This work elaborates the unique compensation effects of heavy metals and phosphorus copoisoning over CeO₂/TiO₂ catalysts for NO_x reduction and provides a perspective for further designing multipoisoning-resistant CeO₂-based catalysts to efficiently control NO_x emissions in stationary sources.

Short-Term and Long-Term Impacts of Air Pollution Control on China's Economy

To deal with severe air pollution arising from rapid development, a series of air pollution control policies have been implemented in China. Previous literature has explored the short-term economic impacts of air pollution control, but the long-term economic impacts, which can better reflect the effectiveness of air pollution control, have received less attention. This paper has constructed an integrated assessment framework combining a multi-sectoral computable general equilibrium (CGE) model, air quality estimation module, and health impact module, to explore the short-term (2016) and long-term (2030) impacts of air pollution control on China's economy, by setting 2015 as the base year. The possible future air pollution reduction scenarios were set based on the Thirteenth Five-Year Plan (FYP13) proposed by the Chinese government. Our results have shown that air pollution control would harm China's economy and such adverse effects would be increased by stricter pollution reduction targets. Taking the health benefits of air pollution control into account can effectively alleviate the GDP losses, and even reverse them into economic benefits in the long term. Compared with business-as-usual (BAU) scenario (no policy constraints on SO₂ and NO_x emissions), the impact of air pollution control on GDP in the TAC_VIII scenario (emission reduction targets of 20% for SO₂ and NO_x are set every five years after 2015) would change from a loss of 1.20% in 2016 to an increase of 0.28% in 2030. Our results can provide policy implications for the optimization of China's air emissions control in the future.

Experimental analysis and parameter optimization on the reduction of NOx from diesel engine using RSM and ANN Model

The major emission sources of NO_X are from automobiles, trucks, and various non-road vehicles, power plants, coal fired boilers, cement kilns, turbines, etc. Plasma reactor technology is widely used in gas conversion applications, such as NOx conversion into useful chemical by-product. Among the plasma treatment techniques, nonthermal plasma (NTP) is widely used because it does not cause any damage to the surfaces of the reacting chamber. In this proposed work, the feasibility of Dielectric Barrier Discharge (DBD) reactor-based nonthermal plasma (NTP) process is examined based on four operating parameters including NOx concentration (300-400 ppm), gas flow rate (2-6 lpm), applied plasma voltage (20-30 kVpp), and electrode gap (3-5 mm) for removing NOx gas from diesel engine exhaust. Optimization of NTP process parameters has been carried out using response surface-based Box-Behnken design (BBD) method and artificial neural network (ANN) method and compared with the performance measures such as R², MSE (mean square error), RMSE (root mean square error), and MAPE (mean absolute percentage error). Two kinds of analysis were carried out based on (1) NOx removal efficiency and (2) energy efficiency. Based on the simulation studies carried out for Nox removal efficiency, the RSM methodology produces the performance measures, 0.98 for R², 1.274 for MSE, 1.128 for RMSE, and 2.053 for MAPE, and for ANN analysis method, 0.99 for R², 2.167 for MSE, 1.472 for RMSE, and 1.276 for MAPE. These results shows that ANN method is having enhanced performance measures. For the second case, based on the energy efficiency study, the R², MSE, RMSE, and MAPE values from the RSM model are 0.97, 2.230, 1.493, and 2.903 respectively. Similarly based on ANN model, the R², MSE, RMSE, and MAPE values are 0.99, 0.246, 0.46, and 0.615, respectively. From the performance measures, it is found that the ANN model is accurate than the RSM model in predicting the NOx removal/reduction and efficiency. These models demonstrate that they have strong agreement with the experimental results. The experimental results are indicated that optimum conditions arrived based on the RSM model resulted in a maximum NOx reduction of 60.5% and an energy efficiency of 66.24 g/J. The comparison between the two models confirmed the findings, whereas this ANN model displayed a stronger correlation to the experimental evidence.

A benefit allocation model for the joint prevention and control of air pollution in China: In view of environmental justice

The benefit allocation of fair and justice is an inevitable guarantee for the long-term operation of the joint prevention and control of air pollution (JPCAP). The ignorance of interest demands of various governance subjects in the existing benefit allocation mechanism results in the widespread "free rider" behavior in the joint control and unsatisfactory effects of JPCAP. Given this, it is imperative to build a reasonable benefit allocation model. The innovation of this paper is proposing a benefit allocation model of JPCAP to achieve the symmetry between control costs and benefits based on environmental justice. The control objectives and total benefits of JPCAP are calculated through the adjustment of optimal removal rates. The interest demands of various control subjects and benefit compensation scheme are clarified by adopting an improved Shapley method, which comprehensively considers factors affecting environmental justice. An empirical analysis is conducted on SO₂ governance in Beijing-Tianjin-Hebei (BTH) and its surrounding areas. The results show that the benefit allocation model based on environmental justice can not only accurately evaluate the benefits of joint control, but also effectively achieve the symmetry between control costs and benefits. This study provides a scientific and reasonable theoretical basis for the benefit allocation of SO₂ control and can be extended to the researches and practices of other air pollutants control.

Stainless steel catalyst for air pollution control: structure, properties, and activity

With the awakening of environmental awareness, the importance of air quality to human health and the proper functioning of social mechanisms is becoming increasingly prominent. The low cost and high efficiency of catalytic technique makes it a natural choice for achieving deep air purification. Stainless steel alloys have demonstrated their full potential for application in a variety of catalytic fields. The diversity of 3D networks or fibrous structures increases the turbulence within the heterogeneous catalysis, balance the temperature distribution in the reaction bed and, in combination with a highly thermally conductive skeleton, avoid agglomeration and deactivation of the active components; corrosion resistance and thermal stability are adapted to highly endothermic/exothermic or corrosive reaction environments; oxide layers formed by bulk transition metals activated by thermal treatment or etching can significantly alter the physico-chemical properties between the substrate and active species, further improving the stability of stainless steel catalysts; suitable electronic conductivity can be applied to the electrothermal catalysis, which is expected to provide guidance for the reduction of intermittent emission exhausts and the storage of renewable energy. The current applications of stainless steel as catalyst or support in the air purification have covered soot particle capture and combustion, catalytic oxidation of VOCs, SCR, and air sterilization. This paper summarizes several preparation methods and presents the relationships between the preparation process and the activity, and reviews its application and the current status of research in atmospheric environmental management, proposing the advantages and challenges of the stainless steel-based catalysts.

Mix-method modelling of actors' capacity for environmental sustainability and climate compatible development in energy sector

The development of the energy sector has played a major role in greenhouse gas (GHG) emissions and pollution. The situation thus necessitates rigorous actions for climate compatible development (CCD). The energy sector is context-dependent, due to which response strategies for CCD are quite challenging particularly in the context of energy crises and the actors' capacity issue in developing countries. This study was aimed at exploring the role of government actors involved in governing the energy sector, with the objective to assess their capacity using a set of principles, criteria, and indicators (PCIs). The study attempted to answer the question: is the capacity of the line departments involved in energy governance adequate to achieve the targets set under SDG-7 and SDG-13? For this purpose, the study employed a combination of "Rules-based" and "Rights-based" governance approaches at all tiers of governance, i.e., federal, provincial, and district levels. Actors' capacity was assessed by developing a governance index based on the scoring of PCIs. Three hundred forty key informant interviews (KIIs) and 17 focus group discussions (FGD) were conducted at federal, provincial, and district levels where respondents were asked to score each of the indicators. Responses were then statistically analyzed and validated. The findings revealed that departments at the federal level are playing an effective role and are adequately equipped to align SDG-7 and SDG-13 with energy sector development. However, departments at the provincial and district levels are still lagging behind to achieve the desired objectives, which demonstrate the need to enhance the capacities of provincial and district line departments.

Reflection on the joint prevention and control of air pollution from the perspective of environmental justice-insights from a two-stage dynamic game model

The practices of the joint prevention and control of air pollution (JPCAP) present two disadvantages: the low enthusiasm of governance subjects and an unsatisfactory governance effect. Revealing the existing problems and exploring their causes has been a key issue for promoting JPCAP. Given this, we especially establish a two-stage dynamic game model for air pollution control to explore the advantages and dilemmas of JPCAP by analyzing changes in environmental tax rate and social welfare. The results show that the unfair distribution of social welfare among cities is a key reason for the unsatisfactory effect of JPCAP. Therefore, we improve JPCAP by considering both production-oriented and consumption-oriented pollutions based on environmental justice. In the improved JPCAP mode, the social welfare of each city is higher than that of non-joint control of air pollution (NJCAP), in which the increased degree is positively related to the city's negotiation ability. In addition, the consumption tax rate is negatively correlated with the negotiation ability of the central city and the trade transfer coefficient. This study not only provides a theoretical and methodological reference for formulating effective planning and compensation scheme for JPCAP but also can be extended to the practice and theoretical analysis of other cross-regional public issues.

Update on air pollution control strategies for coal-fired power plants

ABSTRACT

Coal is expected to remain a significant power supply source worldwide and shifting to carbon-neutral fuels will be challenging because of growing electricity demand and booming industrialization. At the same time, coal consumption results in severe air pollution and health concerns. Improvement in emission control technologies is a key to improving air quality in coal power plants. Many scientists reported removing air pollutants individually via conventional control methods. However, controlling multiple pollutants combinedly using the latest techniques is rarely examined. Therefore, this paper overviews the current and advanced physical technologies to control multi-air pollutants synergistically, including carbon control technologies. Also, the paper aims to examine how potential air pollutants (e.g., PM_2.5, SO₂, NOx, CO₂), including mercury from the coal-fired power plants, cause environmental impacts. The data synthesis shows that coal quality is the most significant factor for increasing air emissions, regardless of power plant capacity. It is found that selecting techniques is critical for new and retrofitted plants depending on the aging of a power plant and other socio-economic factors. Considering the future perspective, this paper discusses possible pathways to transform from linear to a circular economy in a coal power plant sector, such as utilizing energy losses through energy-efficient processes and reuse of syngas. The article provides an in-depth analysis of advanced cost-effective techniques that would help to control the air pollution level. Additionally, a life cycle assessment-based decision-making framework is proposed that would assist the stakeholders in achieving net-zero emissions and offset the financial burden for air pollution control in coal-fired power plants.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10098-022-02328-8.

Assimilative capacity approach for air pollution control in automotive engines through magnetic field-assisted combustion of hydrocarbons

Deterioration of air quality through the combustion of hydrocarbon fuels has been one of the global transboundary problems put before the research community since last five decades. According to the updated statistics, 79% of energy needs in India are met by fossil fuel combustion which results in the emission of toxic pollutants like carbon monoxide, oxides of nitrogen, and unburned hydrocarbons. Air quality has seriously been affected in many parts of India, and statistically, 13 out of 15 most polluted cities in the world lie in India. Magnetic field-assisted combustion has been proven as a reliable technology in internal combustion engines for enhancing the combustion of fuels and reduction of harmful emissions that are the byproducts of incomplete combustion of fuels. In the present work, the magnetic field-assisted combustion of a liquid-phase and a gas-phase fuel (gasoline and LPG) has been studied in a multicylinder automobile engine replicating on road driving conditions in a laboratory focusing on the levels of emissions in comparison with normal combustion of both the fuels. The experimental study concludes that the applied magnetic field positively influences combustion, resulting in reduced level of emission of toxic components irrespective of the phase of hydrocarbon fuels. It is also observed that the percentage reduction in emissions increases with increase in intensity of magnetization. The maximum reduction obtained for CO and UBHC emissions through this technique is 20.58% and 14.47%, respectively. The effectiveness of MFAC in countering air pollution from vehicular exhaust is also studied with respect to fuel phase and mode of operation. The effectiveness of MFAC is observed to be more in high-speed operation of the engine and decreases in the order CO > UBHC > NO. The obtained emission results have a cumulative significance as 45% of total air pollution in India is caused by combustion of hydrocarbons in automotive engines.

The potential of using Cedrus atlantica as a biomonitor in the concentrations of Cr and Mn

Air pollution is becoming increasingly dangerous which is quite a significant issue of today's world, especially air pollution from heavy metal, whose emission increases with industrial and traffic activities. This is of great importance in terms of environmental pollution and human health. Heavy metals do not deteriorate and disappear easily on earth. They are liable to bioaccumulate within cells in organisms. Most of them demonstrate harmful effects in addition as a result of advanced accumulation, and thus they emerge as toxic and carcinogenic. Therefore, it is of great importance to observe the changes in heavy metal concentrations in the air. One of the most effective techniques for monitoring the change of heavy metal concentrations in the atmosphere is the use of annual rings of trees as biomonitors. In this study, in the annual rings of the Cedrus atlantica Manetti tree cut at the Kastamonu province at the end of 2019, the variation of the concentrations of some of the heavy metals most associated with traffic density was tried to be determined. Within the scope of the study, Cr and Mn concentration in the outer bark and the inner bark was compared with the direction and wood for the variation of heavy metal concentrations. Also, variance analysis and Duncan test were applied and evaluated. As a result of the study, while the highest values in many heavy metals are generally obtained in the outer bark, the transfer of metals in the wood is limited, and some heavy metal concentrations change significantly depending on the direction, especially in the wood. This change is related to the traffic density, so Cedrus atlantica Manetti annual rings are very suitable as biomonitors for air pollution control.

High performance of catalytic sheet filters of V2O5-WO3/TiO2 for NOx reduction

Nitrogen oxide (NO_x) emissions in fuel from the stationary as well as from mobile sources primarily from power stations, industrial heaters, cogeneration plants, and diesel engines represent a major worldwide environmental problem. The selective catalytic reduction (SCR) of NO_x with NH₃ over catalyst based on V₂O₅-WO₃/TiO₂ (VWT) is the most effective benchmark technique to efficiently reduce NO_x emissions from stationary and mobile sources. Among the different transition metals (Mn, Nb, Co, Cr, Cu, Ce) used in current research work, the manganese could make up the loss of SCR activity caused by the decrease of V₂O₅ loading (50%) in prepared VWT powder catalyst. The optimal loading of Mn is 3 wt% in case of 3V9WT powder catalyst, which shows the best catalytic performance. 3Mn3V9WT powder catalyst exhibits enhanced NO conversion performance, i.e., ~ 95-98% with NH₃ leakage < 20 ppm, for the temperature window of 260-320 °C in comparison with all other metal-doped 3V9WT catalyst powder. Manganese is the best substitute (50%) to vanadium in VWT catalyst without compromising the NO conversion performance even in presence of SO₂ (1000 ppm), i.e., > 94% for the temperature of 300-320 °C. The recovery of SCR activity of the 3Mn3V9WT catalyst after SO₂ effect was good, i.e., ~ 94% at 320 °C for long interval of time, where NH₃ leakage was < 5 ppm.

Co-benefits of carbon and pollution control policies on air quality and health till 2030 in China

Facing the dual challenges of climate change and air pollution, China has made great efforts to explore the co-control strategies for the both. We assessed the benefits of carbon and pollution control policies on air quality and human health, with an integrated framework combining an energy-economic model, an air quality model and a concentration-response model. With a base year 2015, seven combined scenarios were developed for 2030 based on three energy scenarios and three end-of-pipe control ones. Policy-specific benefits were then evaluated, indicated by the reduced emissions, surface concentrations of major pollutants, and premature deaths between scenarios. Compared to the 2030 baseline scenario, the nationwide PM_2.5- and O₃-related mortality was expected to decline 23% or 289 (95% confidence interval: 220-360) thousand in the most stringent scenario, and three quarters of the avoided deaths were attributed to the end-of-pipe control measures. Provinces in heavily polluted and densely populated regions would benefit more from carbon and pollution control strategies. The population fractions with PM_2.5 exposure under the national air quality standard (35 μg/m³) and WHO guideline (10 μg/m³) would be doubled from 2015 to 2030 (the most stringent scenario), while still very few people would live in areas with the WHO guideline achieved for O₃ (100 μg/m³). Increased health impact of O₃ suggested a great significance of joint control of PM_2.5 and O₃ in future policy-making.

Removal of volatile organic compounds (VOCs) from waste air stream using ozone assisted zinc oxide (ZnO) nanoparticles coated on zeolite

The release of volatile organic compounds (VOCs) from stationary and mobile sources increases the concentration of these pollutants in the environment. These compounds have the potential to cause adverse effects on human health and the environment. The adoption of management and engineering procedures to control the emission of these pollutants to the air has become essential. The aim of this study was to use an advanced oxidation process namely the catalytic ozonation to reduce the concentration of these pollutants in industrial output. In this experimental study, the catalytic ozonation process in the presence of ZnO nanoparticles coated on zeolite media was used in a laboratory scale to treat the air contaminated with BTEX compounds as indicators of VOCs. For this purpose, First the nanocomposites were synthesized based on chemical co-precipitation method. SEM, XRD, BET and FT-IR analyses were performed to investigate the characteristics of nanocomposites. The variables including initial concentrations of BTEX (50-200 ppm), polluted air flow rate (5-20 l/h), humidity (0-75%) and ozone dose (0.25-1 g/h) were investigated. The concentration of BTEX compounds was measured by the Gas Chromatography (GC) technique according to the NIOSH 1501 manual. The results of SEM, XRD, BET and FT-IR analyses showed the proper synthesis of nanocomposites. According to the laboratory results, the optimal conditions of the process were found to be as follows: the initial concentration of pollutants equal to 50 ppm, inlet air flow rate of 5 l/h, relative air humidity of 25-35%, and inlet ozone concentration equal to 1 g/h. Under these conditions, the removal efficiency of the compounds: benzene, toluene, ethylbenzene and xylene were obtained 98, 96, 92 and 91%, respectively. Simple ozonation and adsorption processes were less efficient than catalytic ozonation. This process had the ability to reduce the concentration of BTEX compounds to standard level.

Fifty years of EPA science for air quality management and control

Research and development has been a key part of the foundation for improvements in US air quality since the establishment of the Environmental Protection Agency (EPA) 50 years ago. Although the scientific accomplishments and advances over the course of EPA's history are often overshadowed by policy debates, much of the air pollution science and engineering we now consider to be routine did not exist when EPA was established. Many of the advances in air pollutant measurement, monitoring, modeling, and control were developed by EPA researchers or supported by EPA programs. The technical foundation built during EPA's early years has since given the Agency the scientific ability to respond quickly and effectively to unexpected and emerging issues. Equally important, EPA also developed approaches to conducting and presenting science in policy settings to ensure that the science was as objective and complete as possible and was communicated effectively. A look back at some of the accomplishments of EPA scientists and engineers provides a reminder that the cumulative effect of continual, incremental advances can result in large and lasting benefits to society.

Reduction of polycyclic compounds and biphenyls generated by pyrolysis of industrial plastic waste by using supported metal catalysts: A case study of polyethylene terephthalate treatment

The accumulation of industrial plastic waste in the environment is a global growing concern. Thermochemical process is a preferred method to dispose plastic waste mainly because it can reduce volume of the waste; however, the thermochemical disposal of plastic waste can emit harmful chemical species such as benzene derivatives and polycyclic hydrocarbons. As an effort to overcome this challenge, supported metal catalysts (carbon-supported Pd and Pt catalysts) were used to inhibit the formation of polycyclic compounds and biphenyl derivatives by pyrolysis of polyethylene terephthalate (PET). Less polycyclic compounds and biphenyl derivatives were generated during the Pd or Pt-catalyzed PET pyrolysis than non-catalytic PET pyrolysis. The concentrations of polycyclic compounds and biphenyl derivatives were 107 % and 56 % lower for the Pt-catalyzed pyrolysis at 700 °C than non-catalytic pyrolysis, respectively. The Pt catalyst was more effective to suppress the generation of polycyclic compounds and biphenyl derivatives during the PET pyrolysis than the Pd catalyst at temperatures from 400 to 800 °C. This was likely because the Pt sites catalyzes decyclization reaction and/or free radical mechanism that is dominant in thermal cracking of carbonaceous substances such as PET. The results of this study would help develop environmentally friendly industrial plastic waste treatment methods via thermochemical processes.

Energy efficiency improvement in nitric oxide reduction by packed DBD plasma: optimization and modeling using response surface methodology(RSM)

The non-thermal plasma (NTP) is a superior proposed method for nitric oxide removal because of operation at atmospheric pressure and ambient temperature. The energy consumption is the main challenge of using this technology. The packed plasma reactor with dielectric materials has been extensively investigated; it has higher energy efficiency. In this study, the energy efficiency and the other effectiveness factors in nitric oxide removal by NTP reactor packed with ceramic and glass beads optimized and modeled using Response Surface Methodology. The findings showed the maximum energy efficiency was 132.69g/J in the optimal conditions of initial concentration, gas flowrate, and duty cycle(voltage) equal to 1050 ppm, 2.5 L/min, and 9%(22KV), respectively in the packed reactor with ceramic beads by 1.7 times than the empty reactor. It is concluded that the use of ceramic beads as a dielectric material in the discharge space significantly increased energy efficiency in the removal of nitric oxide.

Adsorption of acetone and cyclohexane onto CO2 activated hydrochars

Most of the volatile organic compounds (VOCs) are toxic and harmful to human health and environment. In this study, hydrochars activated with CO₂ were applied to remove VOCs. Two typical VOCs, acetone and cyclohexane, were used as the 'model' adsorbates to evaluate hydrochars' performance. Specific surface areas of pristine hydrochars were small (<8 m²/g), whereas activated hydrochars showed much higher values (up to 1308 m²/g). As a result, the adsorption of VOCs onto the pristine hydrochars (13.24-24.64 mg/g) was lower than that of the activated ones (39.42-121.74 mg/g). The adsorption of the two VOCs onto the hydrochars was exothermal. In addition, there were significant correlations (R² > 0.91) between the VOC removal and hydrochars' specific surface area. These results suggest that the governing mechanism was mainly physical adsorption. Increasing experimental temperature (80-139 °C) desorbed the VOCs from the hydrochars. Due to its higher boiling point, cyclohexane desorption required a higher temperature than acetone desorption. The reusability of the activated hydrochars to the two VOCs was confirmed by five continuous adsorption-desorption cycles. The overall results indicated that hydrochars, particularly after CO₂ activation, are sufficient for VOC abatement.

Has the mortality risk declined after the improvement of air quality in an ex-heavily polluted Chinese city-Lanzhou?

Lanzhou, an ex-heavily polluted city, was awarded "The Award for Today's Transformative Step" in 2015 World Climate Conference at Paris for its great efforts on air quality improvement since 2012. However, the health benefits from this improvement remain unclear. Therefore, we collected time-series data covering deaths, weather variables and air pollutants during the two periods (2004-2009, 2014-2017) and fitted single-pollutant models using the generalized additive models to evaluate the change of mortality risks associated with air pollutants in Lanzhou. Results showed that the annual average concentrations of respirable particulate matter (PM₁₀) and sulfur dioxide (SO₂) dropped by 19.28% and 66.29%, while the nitrogen dioxide (NO₂) increased by 16.61% in 2014-2017 compared to 2004-2009. During the period 2004-2009, we found a 10-μg/m³ increase in PM₁₀ (lag 2), SO₂ (lag 0-5) and NO₂ (lag 0-5) were associated with mortality increments of 0.12% (95% CI: 0.01, 0.22), 0.86% (95% CI: 0.42, 1.31) and 1.29% (95% CI: 0.70, 1.90), respectively. During the period 2014-2017, the association between PM₁₀ and daily deaths was not significant, but we observed a 10-μg/m³ increase in SO₂ (lag 0-5) and NO₂ (lag 4) were related to mortality increments of 4.23% (95% CI: 1.82, 6.70) and 0.85% (95% CI: 0.19, 1.52), respectively. From 2004-2009 to 2014-2017, we observed markedly decline of mortality risk due to PM₁₀, but not SO₂ or NO₂. In conclusion, the mortality risk of PM₁₀ in Lanzhou has declined obviously after the substantially improved air quality due to the enforcement of air pollution controlling policies.

Development and deployment of integrated air pollution control, CO2 capture and product utilization via a high-gravity process: comprehensive performance evaluation

In this study, a proposed integrated high-gravity technology for air pollution control, CO₂ capture, and alkaline waste utilization was comprehensively evaluated from engineering, environmental, and economic perspectives. After high-gravity technology and coal fly ash (CFA) leaching processes were integrated, flue gas air emissions removal (e.g., sulfate dioxide (SO₂), nitrogen oxides (NO_x), total suspended particulates (TSP)) and CO₂ capture were studied. The CFA, which contains calcium oxide and thus, had high alkalinity, was used as an absorbent in removing air pollution residues. To elucidate the availability of technology for pilot-scale high-gravity processes, the engineering performance, environmental impact, and economic cost were simultaneously investigated. The results indicated that the maximal CO₂, SO₂, NO_x, and TSP removal efficiencies of 96.3 ± 2.1%, 99.4 ± 0.3%, 95.9 ± 2.1%, and 83.4 ± 2.6% were respectively achieved. Moreover, a 112 kWh/t-CO₂ energy consumption for a high-gravity process was evaluated, with capture capacities of 510 kg CO₂ and 0.468 kg NO_x per day. In addition, the fresh, water-treated, acid-treated, and carbonated CFA was utilized as supplementary cementitious materials in the blended cement mortar. The workability, durability, and compressive strength of 5% carbonated CFA blended into cement mortar showed superior performance, i.e., 53 MPa ±2.5 MPa at 56 days. Furthermore, a higher engineering performance with a lower environmental impact and lower economic cost could potentially be evaluated to determine the best available operating condition of the high-gravity process for air pollution reduction, CO₂ capture, and waste utilization.

Catalytic oxidation at pilot-scale: Efficient degradation of volatile organic compounds in gas phase

Volatile organic compounds (VOCs) are responsible for environmental problems and may affect human health. Several treatment technologies minimize VOCs emissions; among those, catalytic oxidation appears as a promising alternative. In this study, a pilot-scale catalytic reactor was developed and the influence of process parameters on toluene degradation were investigated. Inlet gases were heated by electrical resistances and the catalyst employed was a honeycomb shape commercial automotive catalyst (Umicore, model AFT). Toluene degradation higher than 99% was achieved for several conditions and temperature showed to be the most important process variable for it. For all concentrations, it was observed that when increasing temperature led to a decrease on the space time. At 800 ppmv, varying from 543 K to 633 K, the space time decreased from 0.121 s to 0.08 s, respectively. At 1600 ppmv for the same temperature range, space time was reduced from 0.098 s to 0.040 s, respectively. At 2400 ppmv, varying from 543 K to 633 K, space time decreased from 0.081 s to 0.048 s. The catalytic reactor developed proved to be efficient for VOCs treatment, showing a high potential of application at industrial emission sources.

Chemically activated hydrochar as an effective adsorbent for volatile organic compounds (VOCs)

Hydrochars derived from hickory wood and peanut hull through hydrothermal carbonization were activated with H₃PO₄ and KOH to improve their performance as a volatile organic compound (VOC) adsorbent. Polar acetone and nonpolar cyclohexane were used as representative VOCs. The VOC adsorptive capacities of the activated hydrochars (50.57-159.66 mg⋅g^-1) were greater than that of the nonactivated hydrochars (15.98-25.36 mg⋅g^-1), which was mainly caused by the enlargement of surface area. The significant linear correlation (R² = 0.984 on acetone, and R² = 0.869 on cyclohexane) between BET surface areas of hydrochars and their VOC adsorption capacities, together with the obvious adsorption exothermal peak of differential scanning calorimetry curve confirmed physical adsorption as the dominating mechanism. Finally, the reusability of activated hydrochar was tested on H₃PO₄ activated hickory hydrochar (HHP), which had higher acetone and cyclohexane adsorption capacities. After five continuous adsorption desorption cycles, the adsorptive capacities of acetone and cyclohexane on HHP decreased by 6.2% and 7.8%, respectively. The slight decline in adsorption capacity confirmed the reusability of activated hydrochar as a VOC sorbent.

Recent progress and perspectives in biotrickling filters for VOCs and odorous gases treatment

Pollution caused by volatile organic compounds (VOCs) and odorous pollutants in the air can produce severe environmental problems. In recent years, the emission control of VOCs and odorous pollutants has become a crucial issue owing to the adverse effect on humans and the environment. For treating these compounds, biotrickling filter (BTF) technology acts as an environment friendly and cost-effective alternative to conventional air pollution control technologies. Besides, low concentration of VOCs and odorous pollutants can also be effectively removed using BTF systems. However, the VOCs and odorants removal performance by BTF may be limited by the hydrophobicity, toxicity, and low bioavailability of these pollutants. To solve these problems, this review summarizes the design, mechanism, and common analytical methods of recent BTF advances. In addition, the operating conditions, mass transfer, packing materials and microorganisms (which are the critical parameters in a BTF system) were evaluated and discussed in view of improving the removal performance of BTFs. Further research on these specific topics, together with the combination of BTF technology with other technologies, should improve the removal performance of BTFs.

Removal of acetone from air emissions by biotrickling filters: providing solutions from laboratory to full-scale

A full-scale biotrickling filter (BTF) treating acetone air emissions of wood-coating activities showed difficulties to achieve outlet concentrations lower than 125 mg C m^-3, especially for high inlet concentrations and oscillating emissions. To solve this problem, a laboratory investigation on acetone removal was carried out simulating typical industrial conditions: discontinuous and variable inlet concentrations and intermittent spraying. The results were evaluated in terms of removal efficiency and outlet gas emission pattern. Industrial emissions and operational protocols were simulated: inlet load up to 70 g C m^-3 h^-1 during 2 cycles of 4 h per day and intermittent trickling of 15 min per hour. The outlet gas stream of the pollutant was affected by intermittent spraying, causing a fugitive emission of pollutant. Complete removal efficiency was obtained during non-spraying. Average removal efficiencies higher than 85% were obtained, showing the feasibility of BTF to treat acetone. The outlet gas stream showed a clear dependence on the pH of the trickling liquid, decreasing the removal at pH < 5.5. Thus, a proper control of alkalinity, with regular NaHCO₃ addition, was required for successful operation. The laboratory findings were fruitfully transferred to the industry, and the removal of acetone by full-scale BTF was improved.

Status and perspectives of municipal solid waste incineration in China: A comparison with developed regions

With the rapid expansion of municipal solid waste (MSW) incineration, the applicability, technical status, and future improvement of MSW incineration attract much attention in China. This paper aims to be a sensible response, with the aid of a comparison between China and some representative developed regions including the EU, the U.S., Japan, South Korea, and Taiwan area. A large number of up-to-date data and information are collected to quantitatively and impartially support the comparison, which covers a wider range of key points including spatial distribution, temporal evolution, technologies, emissions, and perspectives. Analysis results show that MSW incineration is not an outdated choice; however, policy making should prevent the potentially insufficient utilization of MSW incinerators. The structure of MSW incineration technologies is changing in China. The ratio of plants using fluidized bed is decreasing due to various realistic reasons. Decision-makers would select suitable combustion technologies by comprehensive assessments, rather than just by costs. Air pollution control systems are improved with the implementation of China's new emission standard. However, MSW incineration in China is currently blamed for substandard emissions. The reasons include the particular elemental compositions of Chinese MSW, the lack of operating experience, deficient fund for compliance with the emission standard, and the lack of reliable supervisory measures. Some perspectives and suggestions from both technical and managerial aspects are given for the compliance with the emission standard. This paper can provide strategic enlightenments for MSW management in China and other developing countries.

Air ionization as a control technology for off-gas emissions of volatile organic compounds

High energy electron-impact ionizers have found applications mainly in industry to reduce off-gas emissions from waste gas streams at low cost and high efficiency because of their ability to oxidize many airborne organic pollutants (e.g., volatile organic compounds (VOCs)) to CO₂ and H₂O. Applications of air ionizers in indoor air quality management are limited due to poor removal efficiency and production of noxious side products, e.g., ozone (O₃). In this paper, we provide a critical evaluation of the pollutant removal performance of air ionizing system through comprehensive review of the literature. In particular, we focus on removal of VOCs and odorants. We also discuss the generation of unwanted air ionization byproducts such as O₃, NOx, and VOC oxidation intermediates that limit the use of air-ionizers in indoor air quality management.

Removal of H2S pollutant from gasifier syngas by a multistage dual-flow sieve plate column wet scrubber

The objective of this study was to observe the performance of a lab-scale three-stage dual-flow sieve plate column scrubber for hydrogen sulfide (H₂S) gas removal from a gas stream, in which the H₂S concentration was similar to that of gasifier syngas. The tap water was used as scrubbing liquid. The gas and liquid were operated at flow rates in the range of 16.59 × 10^-4-27.65 × 10^-4 Nm³/s and 20.649 × 10^-6-48.183 × 10^-6 m³/s, respectively. The effects of gas and liquid flow rates on the percentage removal of H₂S were studied at 50-300 ppm inlet concentrations of H₂S. The increase in liquid flow rate, gas flow rate and inlet H₂S concentration increased the percentage removal of H₂S. The maximum of 78.88% removal of H₂S was observed at 27.65 × 10^-4 Nm³/s gas flow rate and 48.183 × 10^-6 m³/s liquid flow rate for 300 ppm inlet concentration of H₂S. A model has also been developed to predict the H₂S gas removal by using the results from the experiments and adding the parameters that affect the scrubber's performance. The deviations between experimental and predicted H₂S percentage removal values were observed as less than 16%.

Removal of fly-ash and dust particulate matters from syngas produced by gasification of coal by using a multi-stage dual-flow sieve plate wet scrubber

In this work, fly-ash water scrubbing experiments were conducted in a three-stage lab-scale dual-flow sieve plate scrubber to observe the performance of scrubber in fly-ash removal at different operating conditions by varying the liquid rate, gas rate and inlet fly-ash loading. The percentage of fly-ash removal efficiency increases with increase in inlet fly-ash loading, gas flow rate and liquid flow rate, and height of the scrubber; 98.55% maximum percentage of fly-ash removal efficiency (ηFA) is achieved at 19.36 × 10(-4) Nm(3)/s gas flow rate (QG) and 48.183 × 10(-6) m(3)/s liquid flow rate (QL) at 25 × 10(-3) kg/Nm(3) inlet fly-ash loading (CFA,i). A model has also been developed for the prediction of fly-ash removal efficiency of the column using the experimental results. The predicted values calculated using the correlation matched well with the experimental results. Deviations observed between the experimental and the predicted values were less than 20%.

Potential health benefits of controlling dust emissions in Beijing

Although the adverse impact of fine particulate matter (i.e., PM2.5) on human health has been well acknowledged, little is known of the health effects of its specific constituents. Over the past decade, the annual average dust concentrations in Beijing were approximately ∼14 μg m(-3), a value that poses a great threat to the city's 20 million residents. In this study, we quantify the potential long-term health damages in Beijing resulting from the dust exposure that occurred from 2000 to 2011. Each year in Beijing, nearly 4000 (95% CI: 1000-7000) premature deaths may be associated with long-term dust exposure, and ∼20% of these deaths are attributed to lung cancer. A decomposition analysis of the inter-annual variability of premature deaths in Beijing indicates that dust concentrations determine the year-to-year tendency, whereas population growth and lung cancer mortality rates drive the increasing tendency of premature death. We suggest that if Beijing takes effective measures towards reducing dust concentrations (e.g., controlling the resuspension of road dust and the fugitive dust from construction sites) to a level comparable to that of New York City's, the associated premature deaths will be significantly reduced. This recommendation offers "low-hanging fruit" suggestions for pollution control that would greatly benefit the public health in Beijing.

Waste to energy--key element for sustainable waste management

Human activities inevitably result in wastes. The higher the material turnover, and the more complex and divers the materials produced, the more challenging it is for waste management to reach the goals of "protection of men and environment" and "resource conservation". Waste incineration, introduced originally for volume reduction and hygienic reasons, went through a long and intense development. Together with prevention and recycling measures, waste to energy (WTE) facilities contribute significantly to reaching the goals of waste management. Sophisticated air pollution control (APC) devices ensure that emissions are environmentally safe. Incinerators are crucial and unique for the complete destruction of hazardous organic materials, to reduce risks due to pathogenic microorganisms and viruses, and for concentrating valuable as well as toxic metals in certain fractions. Bottom ash and APC residues have become new sources of secondary metals, hence incineration has become a materials recycling facility, too. WTE plants are supporting decisions about waste and environmental management: They can routinely and cost effectively supply information about chemical waste composition as well as about the ratio of biogenic to fossil carbon in MSW and off-gas.

The washing effect of precipitation on particulate matter and the pollution dynamics of rainwater in downtown Beijing

The particulate matter (PM) pollution of Beijing fluctuated significantly before and after precipitation events during the rainy period. The rainwater samples were continually collected at five-minute intervals on the roof of a building in downtown Beijing. The PM₂.₅ was also monitored at same temporal scale. The pH and concentrations of ammonia-N, nitrate-N, phosphorus, sulfur, and heavy metals (Cd, Mn, Fe, Zn, and Cu) in the rainwater samples were measured, and the values were used to assess the effect of washing on PM₂.₅ and determine the characteristics of the rainwater pollutants. The PM₂.₅ was negatively correlated to the quantity of accumulated rainfall (R(2) value ranged from 0.668 to 0.974), which identified the function of the washing process on PM₂.₅ pollution. The washing process of rainfall strongly affects PM₂.₅, which decreased to 10-30 μg m(-3) with 5mm of rainfall. The analysis of the temporal patterns of ten pollutants in rainwater demonstrated that most of the pollution load was contributed by the first 5 to 10 min of the washing process. The event mean concentration (EMC) of nine inorganic pollutants was used to evaluate the pollution load and identify sources of particle pollution. Sulfur was the primary inorganic element detected in PM, and the average EMC of twelve rainfall events was 8.92 mg L(-1). The EMC of ammonia-N, nitrate-N, and phosphorus after significant PM₂.₅ pollution was 11.57 mg L(-1), 1.72 mg L(-1), and 0.019 mg L(-1), respectively. The total pollution load of the rainwater collecting area during the rainy reason was also calculated, and the largest heavy metal load of 3.11 mg was attributed to Zn. The pollution loads of heavy metals and the stable relationship between the pollutants indicate the potential urban environmental management policies in Beijing.

Assessment of methane biodegradation kinetics in two-phase partitioning bioreactors by pulse respirometry

Biological methane biodegradation is a promising treatment alternative when the methane produced in waste management facilities cannot be used for energy generation. Two-phase partitioning bioreactors (TPPBs), provided with a non-aqueous phase (NAP) with high affinity for the target pollutant, are particularly suitable for the treatment of poorly water-soluble compounds such as methane. Nevertheless, little is known about the influence of the presence of the NAP on the resulting biodegradation kinetics in TPPBs. In this study, an experimental framework based on the in situ pulse respirometry technique was developed to assess the impact of NAP addition on the methane biodegradation kinetics using Methylosinus sporium as a model methane-degrading microorganism. A comprehensive mass transfer characterization was performed in order to avoid mass transfer limiting scenarios and ensure a correct kinetic parameter characterization. The presence of the NAP mediated significant changes in the apparent kinetic parameters of M. sporium during methane biodegradation, with variations of 60, 120, and 150% in the maximum oxygen uptake rate, half-saturation constant and maximum specific growth rate, respectively, compared with the intrinsic kinetic parameters retrieved from a control without NAP. These significant changes in the kinetic parameters mediated by the NAP must be considered for the design, operation and modeling of TPPBs devoted to air pollution control.

Integrated assessment of air pollution in tehran, over the period from september 2008 to september 2009

BACKGROUND

Air pollution is a major problem in urban\industrial areas, like Tehran, and has several impacts on human health. This study aimed at assessing concentrations of criteria air pollutants (CO, SO(2), NO(2), O(3), PM(10)) in Tehran, extracting patterns of hourly, daily, weekly, and monthly variations of concentrations, and making comparisons to National Standards and WHO Guidelines.

METHODS

Air quality data were taken from Air Quality Control Corporation and 5 sampling stations (out of 13) were selected for analysis according to data availability. Microsoft Excel 2003 was used for data analysis and plotting the charts.

RESULTS

Patterns of temporal variation (hourly, daily, weekly, and monthly) of air pollutant concentrations were extracted. In some cases extracted patterns matched with the patterns proposed by other researchers. Pollutant concentrations were compared to National Standards and WHO Guidelines and it was observed that in most of the days, we exceeded the limit values.

CONCLUSION

Air pollution in Tehran is quite high and there are many days that we exceed the standards; therefore appropriate control strategies are needed. Although the number of sampling stations is high enough to be representative of whole city, it is proposed that an independent sampling station is setup to check the validity of the measurements.