Acidic Pollutants Research Articles

Understanding the spatial patterns of atmospheric ammonia trends in South Asia

Ammonia (NH3) is the most abundant alkaline gas in the atmosphere, mainly emitted by agricultural activities. NH3 readily reacts with other atmospheric acidic pollutants, such as the oxidation products of sulfur dioxide (SO2) and nitrogen oxides (NOₓ), to create fine particulate matter, which has far-reaching effects on human health and ecosystems. Here, we investigated long-term atmospheric NH3 trends in South Asia (SA) using satellite observations from the Infrared Atmospheric Sounding Interferometer (IASI). We analyzed 15 years (2008–2022) of IASI-NH3 retrievals against climate, biophysical, and chemical variables using an ensemble of multivariate statistical methods to identify the major factors driving the observed patterns in the region. Trend analysis of IASI-NH3 data reveals a significant rise in atmospheric NH3 over 51 % of SA plains, but a downward trend over 31 % of the region. Spatial correlation analysis reveals that biophysical factors, representing cropland expansion and agriculture intensification, have the highest positive correlation over 56 % of SA plains experiencing positive NH3 trends. However, our results reveal that the chemical conversion of NH3 to ammonium compounds, driven by the positive trends in NOₓ and SO2 pollution, is driving the apparently declining trend of NH3 in the other regions. Our results provide important insights into the NH3 trends detected by satellite data and can better inform the policy design aimed at reducing NH3 emissions and improving air quality for developing regions of the world.

The effect of larval exposure to acids and detergents on the life history of the major malaria vector Anopheles arabiensis Patton (Diptera: Culicidae).

Anopheles arabiensis, a highly adaptable member of the Anopheles gambiae complex, poses a challenge for control efforts due to its outdoor biting and resting behaviour. Consequently, indoor insecticide-based control methodsare ineffective against An. arabiensis. Furthermore, An. arabiensis are adapting to breeding in polluted waters, and may be contributing to residual malaria and malaria in urban areas. There have been some advances in understanding the effect of rural pollutants on Anopheles mosquitoes, but the effect of urban pollutants is poorly understood. Thus, in this study, the effect of acidic pollutants [nitric acid (HNO3) and hydrochloric acid (HCl)] and alkaline pollutants (phosphate-free and phosphate-containing detergent) on two laboratory-reared An. arabiensis strains - an insecticide susceptible strain (SENN) and an insecticide-resistant strain selected from SENN (SENN-DDT) - were determined. The median lethal concentration (LC50) and larval exposure on larval development, adult longevity and insecticide tolerance were evaluated. Nitric acid and phosphate-containing detergent were found to be more toxic than HCl and phosphate-free detergent in terms of LC50 values. Detergent exposure (both phosphate-containing and phosphate-free) increased adult longevity of both strains. Nitric acid reduced larval development time in both SENN and SENN-DDT, whereas HCl reduced larval development time in SENN only. By contrast, both phosphate-containing and phosphate-free detergents increased larval development time of both strains. Furthermore, HNO3 and phosphate-containing detergent increased insecticide tolerance the most. The two An. arabiensis strains responded to urban pollutants differently. Thus, this study provides insight into the adaptation of An. arabiensis to acidic and alkaline urban pollutants. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Efficient Recovery of Rare Earth Elements from Acidic Wastewater by a Green β-CDs-Functionalized Nanosponge.

The recovery of rare earth elements (REEs) from acidic wastewater is crucial to sustainable development, industrial processes, and human health. In this research, β-cyclodextrin-based nanosponges (β-CD/PVA-SA NSs) have been proposed as potential adsorbents for europium (Eu), dysprosium (Dy), and gadolinium (Gd) recovery. The nanosponges are synthesized by cross-linking β-cyclodextrin (β-CD) functionalized polyvinyl alcohol (PVA) and sodium alginate (SA). Experimental results indicate that β-CD/PVA-SA NSs exhibit favorable selectivity for Eu, Dy, and Gd, with the maximum adsorption capacity of 222, 217, and 204 mg/g, respectively, in addition to stability and cyclicity. β-CD/PVA-SA NSs maintain selective adsorption effects towards RE ions that are present in acidic mine drainage (AMD), thereby highlighting their potential for practical applications. Furthermore, density functional theory (DFT) simulations have unveiled the fundamental interactions between the functional groups anchored in β-CD/PVA-SA NSs and the REEs, providing vital insights into their adsorption mechanism. Hence, the utilization of β-CD/PVA-SA NSs has the potential to advance initiatives in remediating acidic water pollution and facilitating the sustainable recycling of RE resources.

Complex imprint of air pollution in the basal area increments of three European tree species

The impact of atmospheric pollution on the growth of European forest tree species, particularly European beech, Silver fir and Norway spruce, is examined in five mesic forests in the Czech Republic. Analyzing of basal area increment (BAI) patterns using linear mixed effect models reveals a complex interplay between atmospheric nitrogen (N) and sulphur (S) deposition, climatic variables and changing CO2 concentrations. Beech BAI responds positively to N deposition (in tandem with air CO2 concentration), with soil phosphorus (P) availability emerging as a significant factor influencing overall growth rates. Fir BAI, on the other hand, was particularly negatively influenced by S deposition, although recent growth acceleration suggests growth resilience in post-pollution period. This fir growth surge likely coincides with stimulation of P acquisition following the decline of acidic pollution. The consequence is the current highest productivity among the studied tree species. The growth dynamics of both conifers were closely linked to the stoichiometric imbalance of phosphorus in needles, indicating the possible sensitivity of exogenous controls on nutrient uptake. Furthermore, spruce BAI was positively linked to calcium availability across sites. Despite enhanced water-use efficiency under elevated CO2, spruce growth is constrained by precipitation deficit and demonstrates weakening resilience to increasing growing season air temperatures. Overall, these findings underscore the intricate relationships between atmospheric pollution, nutrient availability, and climatic factors in shaping the growth dynamics of European forest ecosystems. Thus, incorporating biogeochemical context of nutrient availability is essential for realistic modelling of tree growth in a changing climate.

Mechanism and In Situ Prevention of Oxidation in Coal Gangue Piles: A Review Aiming to Reduce Acid Pollution

The acid pollution produced from coal gangue piles is a global environmental problem. Terminal technologies, such as neutralization, precipitation, adsorption, ion exchange, membrane technology, biological treatment, and electrochemistry, have been developed for acid mine drainage (AMD) treatment. These technologies for treating pollutants with low concentrations over a long period of time in coal gangue piles appear to be costly and unsustainable. Conversely, in situ remediation appears to be more cost-effective and material-efficient, but it is a challenge that coal producing countries need to solve urgently. The primary prerequisite for preventing acidic pollutants is to clarify the oxidation mechanisms of coal gangue, which can be summarized as four aspects: pyrite oxidation, microbial action, low-temperature oxidation of coal, and free radical action. The two key factors of oxidation are pyrite and coal, and the four necessary conditions are water, oxygen, microorganisms, and free radicals. The current in situ remediation technologies mainly focus on one or more of the four necessary conditions, forming mixed co-disposal, coverage barriers, passivation coatings, bactericides, coal oxidation inhibitors, microorganisms, plants, and so on. It is necessary to scientifically and systematically carry out in situ remediation coupled with various technologies based on oxidation mechanisms when carrying out large-scale restoration and treatment of acidic coal gangue piles.

Participation of strong charge-assisted hydrogen bonds in interactions of dissolved organic matter represented by Suwannee River Humic Acid

Terrestrial dissolved organic matter (DOM) plays critical roles in many biotic and abiotic environmental reactions as well as in water treatment. Its structure is therefore of great interest. We examined dissolved Suwannee River Humic Acid (HA) to probe the potential participation of exceptionally strong, negative charge-assisted hydrogen bonds, (−)CAHB, in DOM cohesion and interaction with small weak acids using high performance size exclusion chromatography (HPSEC), transmission electron microscopy, zeta-pH curves, and pH drift experiments. The results support a previously proposed two-tier state of aggregation, in which tightly-knit primary particles (≤ ∼10 kDa) form larger secondary aggregates (up to micrometer in size). Evidence for (−)CAHB is gained through zeta potential changes and pH drift experiments. The primary particles interact with (−)CAHB-capable solutes (simple carboxylic acids and phosphate) but not (−)CAHB-incapable solutes. We identified disruption of intra-segmental and inter-molecular (−)CAHB leading to swelling and disaggregation, as well as formation of nouveau (−)CAHB with free groups on HA. The effects were solute-concentration dependent and greater at pH 5 than pH 6, consistent with CAHB theory. Phosphate induced the greatest shifts in the HPSEC molecular size distribution curves. The shifts were unaffected by prior stripping of innate polyvalent metals. We conclude that the (−)CAHB contributes to the cohesion of DOM, affecting its size and charge, and provides a means by which weak acid pollutants, nutrients, and natural compounds can interact with DOM. Such interactions have implications for the behavior of DOM in the environment, the fate and transport of anthropogenic pollutants, and the roles DOM play in water treatment technologies.

Tracing sulfate sources in a tropical agricultural catchment with a stable isotope Bayesian mixing model

Sulfate (SO42−) is an essential anion in drinking water and a vital macronutrient for plant growth. However, elevated sulfate levels can impact ecosystem or human health and could be an important indicator of acid rock drainage or pollution. Therefore, monitoring SO42− sources and transport is important for water quality assessments. This study focused on exploring the sources and transformations of SO42− as well as estimating the proportional contribution of the potential SO42− pollutant sources to groundwater and surface water in a tropical river basin, the Densu River Basin. The study used major ions combined with stable sulfur and oxygen isotope compositions and a Bayesian isotope mixing model, MixSIAR. The major ion characteristics indicate that SO42− concentrations remain stable throughout the rainy and dry seasons but originate from diverse sources. The multi-isotope model (δ34SSO4, δ18OSO4) identified four potential SO42− sources: detergent, precipitation, sewage, and sulfate fertilizer. However, the δ34SSO4 and δ18OSO4 values of the fertilizer source signatures overlapped with those of precipitation and sewage. Nevertheless, the contributions from each source were disentangled using the MixSIAR model, which revealed sewage as the most dominant SO42− pollutant in the Densu Basin, accounting for ~47 % of sulfate in groundwater and ~ 56 % of sulfate in surface water. Sulfate fertilizer (~33 %) was the second most important source after sewage for groundwater, while detergent (~23 %) was the second most important source for surface water. The redox processes of bacterial sulfate reduction and sulfide oxidation were determined to have a minimal impact on the sulfur isotope fractionation within the basin. This study highlights the benefits of combining major ions, sulfur isotopes and the MixSIAR model for identifying sources of sulfate. This approach accounts for uncertainties in source contributions which allows for more robust and reliable apportionment of sulfate sources. The study emphasizes the need for effective waste management and pollution control measures to protect water quality and provides vital guidelines on how to partition sulfate sources on a large catchment scale and evidence for making pollution management decisions on water resources.

Long-term change in winter aerosol composition and sources in Guiyang Southwest China (2003–2020)

This study presents a comprehensive analysis of air quality in China, Southwest China, over four winter seasons: 2003–2004, 2004–2005, 2017–2018 and 2019–2020. We initially collected Total Suspended Particles (TSP) samples during the earlier periods and PM2.5 samples during the later periods. Our goal was to illustrate the changes in sources of atmospheric pollutants over time. By focusing on the chemical composition of water-soluble inorganic ions (WSIIs), we highlighted significant long-term changes in air quality and pollution sources in Guiyang alongside the effectiveness of recent pollution treatment strategies. Historically affected by acid rain and acid pollution, Guiyang has shown notable improvements in air quality. Notably, sulfate pollution, primarily from coal combustion, has significantly decreased, with the sulfates concentration declining from an estimated 19.04 μg m−3 to 30.46 μg m−3 during the winter of 2003–2004, to just 7.37 μg m−3 in PM2.5 during the winter of 2019–2020. Additionally, the mean mass concentration of PM2.5 dropped by 18% between the 2017–2018 and 2019–2020 winters. An increasing ratio of nitrate to sulfate in the aerosols indicates a shift in pollution sources, with secondary nitrate pollution, largely from vehicle emissions, becoming increasingly prevalent. Positive Matrix Factorization (PMF) model analysis identified five major pollution sources, highlighting a transition from secondary sulfate to secondary nitrate as the primary contributors to air pollution in Guiyang, and secondary nitrate pollution mainly from vehicles emission was increasingly severe meanwhile the significance of ammonium should not be overlooked. The results stress the importance of local pollution sources and suggest a need for revised pollution control policies that address the evolving characteristics of aerosols and prioritize the major pollutants in Guiyang, especially during winter months.

Protonated amine and pyrene co-functionalized sodium alginate templated on reduced graphene oxide for highly efficient removal of formaldehyde and acid pollutants

Indoor formaldehyde pollution can cause inestimable harm to human health and even cancers, thus studies on the removal of formaldehyde attract extensive attentions. In this paper, an environmentally friendly and low-cost biomass material, sodium alginate (SA) was utilized to prepare pyrene functionalized amido-amine-alginic acid (AmAA-Py) by acidification and two-step amidation, which is subsequently self-assembled on reduced graphene oxide (rGO) by π-π stacking interaction, and the final composites were acidified to afford a highly porous composite material for chemical removal of formaldehyde. The formaldehyde chemical removal performance of composite is evaluated at different conditions and find that 1.0 g of acidified alginate derivatives and graphene composites (HCl·AmAA-Py-rGO) can adsorb 69.2 mg of HCHO. Simultaneously, amino groups in amido-amine derivative of acidified sodium alginate (AmAA) can react with acidic pollutants such as H2S and HCl via forming ionic bonding without generating any other by-products, which enables efficient and environment-friendly removal of acidic pollutants. The subtle design of the highly porous composite material utilizing low-cost SA and rGO with large specific surface area opens up a new methodology for fabricating highly porous materials for efficient removal of formaldehyde and other indoor hazardous pollutants.

Polymerase Chain Reaction Cleaner with Antibacterial Effect and Faster Elimination of Nucleic Acid Aerosol Pollution

With advancement of nucleic acid detection technology, most universities, biological testing companies, and hospitals have Polymerase Chain Reaction (PCR) laboratories. PCR detection technology is the core technology for nucleic acid detection. When nucleic acid detection is performed in a PCR laboratory, nucleic acid aerosol samples are often dispersed to the environment in the form of aerosols. At this time, there will be some nucleic acid contamination in the PCR laboratory, resulting in false positive samples. The purpose of this paper is to propose a new type of nucleic acid pollution scavenger called PCR Cleaner. Firstly, the best ratio of PCR Cleaner was obtained by a control experiment, and then the antibacterial test for the PCR Cleaner was carried by comparing the nucleic acid pollution removal efficiency of different ratios of PCR Cleaner and common nucleic acid pollution scavenger on the surface and in the air. Experiment results showed that, the removal efficiency of PCR Cleaner on the surface of nucleic acid was much higher than that of alcohol and aqueous solution. Its effect was good enough when compared to the two commonly used nucleic acid pollution scavengers (DNA/RNA-ExitusPlus and PCR clean). The antibacterial and bacteriostatic PCR Cleaner can significantly inhibit the growth of high concentration of E. coli, and can also completely inhibit the low concentration of E. coli.

Effects of bactericides and sulphate reducing bacteria addition on acidification and microbial community structure of newly produced coal gangue

Microbiologically driven acidic pollution of coal gangue has become a major environmental problem in coal gangue dumps in coal mining areas. Addition of bactericides and sulphate reducing bacteria (SRB) is an effective means to control the acidic pollution of coal gangue, but their mechanism of action has not been fully investigated. By adding bactericide, SRB and bactericide-SRB to the newly produced coal gangue, respectively, the effects of these treatments on the microbial community structure were observed. Changes in pH and electrical conductivity (EC) of the gangue leaching solution, as well as the microbial community composition and functional abundance on the gangue surface were analysed by leaching simulation experiments and 16S rRNA sequencing. The results showed that (1) the addition of bactericide-SRB was the most effective treatment to elevate pH before 8 d, while the addition of SRB performed best after 22 d (2) The addition of bactericide and SRB drastically changed the microbial community structure on the gangue surface. Simultaneous addition of both had the best inhibitory effect on pathogenic bacteria and Thiobacillus. (3) All three treatments promote higher abundance of genes related to nitrogen cycling, but reflected in different gene functions. Microorganisms with sulfate respiration function in the experimental group all showed different increases. The abundance of other sulfur cycle genes decreased substantially. However, Human Pathogens All had higher abundance than control check (CK) in each treatment, which may indicate that the addition of either bactericides or SRB increases the risk of microbial pathogenicity to humans.

Multifunctional composite materials of rGO with RAFT initiated polymers with terminal amine or protonated amine functionalities for chemical eliminations HCHO and acidic pollutants at ambient conditions

In this paper, the contribution of self-assembled composite material of bifunctional polymer prepared by RAFT polymerization and rGO to the removal of low concentration HCHO and acids from air were systematically studied. Experimental results demonstrate that the condensation reaction between HCHO and the protonated amino group at the terminal of the rGO-py-pAMHS-NH3+-ph chain effectively can eliminate HCHO chemically, resulting in the release of H2O as the sole by-product following oxime bonds formation. rGO alone is incapable of chemically removing gaseous HCHO, but when combined with the py-pAMHS-NH3+-ph, efficient HCHO conversion can be achieved, well elucidating the remarkable HCHO removal capability via rGO-py-pAMHS-NH3+-ph. The HCHO chemical removal performance of composite is evaluated by a self-made device at the 1000 mL/min N2 velocity under 25 °C and 50 % RH and it is found that 206.41 mg of HCHO can be removed in approximately 4 h by using 1.0 g of rGO-py-pAMHS-NH3+-ph. In addition, cycling experiments demonstrate the rGO-py-pAMHS-NH3+-ph possesses good durability. We also find that the rGO-py-pAMHS-NH2-ph has the ability to remove acids when the terminal protonated amino groups have been converted into amine functionalities. This green and zero-carbon emission methodology for chemical removal of HCHO degradation and acid pollutants could provide valuable reference for developing other efficient strategies to remove other pollutants such as VOCs etc.

Persistent pollution of genetic materials in a typical laboratory environment

From the onset of coronavirus disease (COVID-19) pandemic, there are concerns regarding the disease spread and environmental pollution of biohazard since studies on genetic engineering flourish and numerous genetic materials were used such as the nucleic acid test of the severe acute respiratory syndrome coronavirus (SARS-CoV-2). In this work, we studied genetic material pollution in an institute during a development cycle of plasmid, one of typical genetic materials, with typical laboratory settings. The pollution source, transmission routes, and pollution levels in laboratory environment were examined. The Real-Time quantitative- Polymerase Chain Reaction results of all environmental mediums (surface, aerosol, and liquid) showed that a targeted DNA segment occurred along with routine experimental operations. Among the 79 surface and air samples collected in the genetic material operation, half of the environment samples (38 of 79) are positive for nucleic acid pollution. Persistent nucleic acid contaminations were observed in all tested laboratories and spread in the public area (hallway). The highest concentration for liquid and surface samples were 1.92 × 108 copies/uL and 5.22 × 107 copies/cm2, respectively. Significant amounts of the targeted gene (with a mean value of 74 copies/L) were detected in the indoor air of laboratories utilizing centrifuge devices, shaking tables, and cell homogenizers. Spills and improper disposal of plasmid products were primary sources of pollution. The importance of establishing designated experimental zones, employing advanced biosafety cabinets, and implementing highly efficient cleaning systems in laboratories with lower biosafety levels is underscored. SYNOPSISSTATEMENT. Persistent environmental pollutions of genetic materials are introduced by typical experiments in laboratories with low biosafety level.

Bioindicator responses to extreme conditions: Insights into pH and bioavailable metals under acidic metal environments

Acid mine drainage (AMD) caused environmental risks from heavy metal pollution, requiring treatment methods such as chemical precipitation and biological treatment. Monitoring and adapting treatment processes was crucial for success, but cost-effective pollution monitoring methods were lacking. Using bioindicators measured through 16S rRNA was a promising method to assess environmental pollution. This study evaluated the effects of AMD on ecological health using the ecological risk index (RI) and the Risk Assessment Code (RAC) indices. Additionally, we also examined how acidic metal stress affected the diversity of bacteria and fungi, as well as their networks. Bioindicators were identified using linear discriminant analysis effect size (LEfSe), Partial least squares regression (PLS-R), and Spearman analyses. The study found that Cd, Cu, Pb, and As pose potential ecological risks in that order. Fungal diversity decreased by 44.88% in AMD-affected areas, more than the 33.61% decrease in bacterial diversity. Microbial diversity was positively correlated with pH (r = 0.88, p = 0.04) and negatively correlated with bioavailable metal concentrations (r = −0.59, p = 0.05). Similarly, microbial diversity was negatively correlated with bioavailable metal concentrations (bio_Cu, bio_Pb, bio_Cd) (r = 0.79, p = 0.03). Acidiferrobacter and Thermoplasmataceae were prevalent in acidic metal environments, while Puia and Chitinophagaceae were identified as biomarker species in the control area (LDA>4). Acidiferrobacter and Thermoplasmataceae were found to be pH-tolerant bioindicators with high reliability (r = 1, P < 0.05, BW > 0.1) through PLS-R and Spearman analysis. Conversely, Puia and Chitinophagaceae were pH-sensitive bioindicators, while Teratosphaeriaceae was a potential bioindicator for Cu–Zn–Cd metal pollution. This study identified bioindicator species for acid and metal pollution in AMD habitats. This study outlined the focus of biological monitoring in AMD acidic stress environments, including extreme pH, heavy metal pollutants, and indicator species. It also provided essential information for heavy metal bioremediation, such as the role of omics and the effects of organic matter on metal bioavailability.

Mix Design of Acid Resistant Alkali Activated Materials for Reconstruction of the Building Constructions Damaged by the War

The paper covers the results of development of alkali activated materials stable in the acid environment. Such materials can be used as main materials for reconstruction of the residential and industrial buildings, influenced by the acid pollution or exploitation conditions. It was shown possibility to obtain alkali activated cement able to be use in normal hardening conditions, meeting the requirements for normal cements (compressive strength up to 60 MPa, initial setting time over 45 minutes, coefficient of acid resistance over 0.8). Such results provide possibilities to develop acid resistant repairing mixes for reconstruction and various applications.

Using the overall variation trend and fitting of Na-feldspar crystal plane spacing after chemical corrosion to prevent rock disasters

Sulfuric acid pollution, caused by acid rain, acidic wastewater, and natural acidic wastewater from mines, poses a significant risk to the stability of natural stone slopes and human stone structures. This study aims to develop a non-mechanical testing method for assessing the degree of acid corrosion in rocks, facilitating early intervention by safety engineers. The proposed method involves using XRD to measure the crystal plane spacing of Na-feldspar corroded by different concentrations of sulfuric acid, followed by mathematical analysis to determine the overall deviation degree of the crystal plane spacing. Four Deviation indices were defined to characterize the degree of acid corrosion, and all four indices increased with increasing acidity. By comparing trend charts, an optimized number of crystal planes for analysis was identified. Selecting the 100 sets of data with the largest spacing yielded similar trend results as selecting all the data. In addition, five different fitting methods were compared, and the power function fitting of Weighted Sum of squares of cumulative errors (WSSCE) was found to provide the optimal empirical formula, with a correlation coefficient exceeding 0.98.

The performance of Adsorbing and Removing gaseous acetic acid by activate carbon

Currently, gaseous molecular contaminants (acetic acid) is one of the main factors that cause defects in semiconductors and wafers, reduce product yields in high-tech process plants. Propylene Glycol Monomethyl Ethyl Ether Acetate (PGMEA) is a versatile solvent with many applications. Solvents used in the solder mask process in the manufacture of printed circuit boards (PCBs). The diluent in photoresist and edge bead removers used in semiconductor and wafer fabrication is PGMEA, which forms acetate contaminants through an acid-catalyzed hydrolysis reaction. The concentration standard of acetic acid pollutants in clean rooms is 1ppb.In order to protect the expensive optical components, the acetic acid generated by PGMEA needs to be controlled.For this purpose, the activated carbon filter in the intake filter prevents acetic acid from contaminating the components and corroding the material. In this study, we used the commercially available activated carbon fabricated filter to adsorption of acetic acid. The effect of adsorption under different face velocity (0.03/0.06/0.09 m/s) and initial acetic acid concentrations (4/6/8/10 ppm) were measured according to the principle of ASHRAE 145.1standard. The experimental data are also evaluated for adsorption performance, adsorption capacity, kinetic model of acetic acid adsorption process, and isothermal model of acetic acid adsorption process.The results of the acetic acid adsorption experiment show that MM3000 activated carbon has the highest adsorption capacity and the longest adsorption saturation time than KPL activated carbon. The higher the inlet acetic acid concentration at a fixed wind speed, the shorter the saturation time and the higher the adsorption capacity; the faster the wind speed at a fixed acetic acid concentration, the shorter the saturation time and the higher the adsorption capacity.The Langmuir (R2) of the MM3000 sample is higher than the Freundlich’s coefficient of determination (R2), which indicates that the adsorption phenomenon of the MM3000 sample is more suitable to be described by the Langmuir isothermal adsorption mode, which is the adsorption of a single molecular layer on a homogeneous surface. The Freundlich R2 of the KPL sample is higher than the Langmuir’s coefficient of determination (R2), which means that the adsorption phenomenon of this KPL sample is more suitable to be described by the Freundlich isothermal adsorption mode, and it is a case of adsorption of multiple layers on an inhomogeneous surface. The adsorption of MM3000 activated carbon and KPL activated carbon is more suitable to be described by the proposed second-order adsorption kinetic model, which is a phenomenon of chemisorption.

Cobalt species immobilized on nitrogen‑doped ordered mesoporous carbon for highly efficient catalytic ozonation of atrazine

The strategy of coupling transition metal and N-doped carbon catalysts have garnered great attention in catalytic ozonation. To overcome the inferior mass transfer of O3, we prepared a hetero-structure catalyst (Co3O4@Co-N-CMK3), which was composed of Co3O4 nanoparticles (NPs) and cobalt-nitrogen doped ordered mesoporous carbon. Co3O4@Co-N-CMK3 displayed a uniformly arranged long-range mesoporous channel structure with large surface area (537.24 m2/g). The adsorption efficiency of ATZ (10 μM) was 55% at 15 min in presence of 0.05 g/L catalyst. After aeration of 3.5 mg/L O3 gas (50 mL min-1), the ATZ removal increased to 99.6% with rate constant of 0.354 min-1 in Co3O4@Co-N-CMK3/O3, 35.4-fold that in ozonation. The turnover frequency (TOF) value of Co3O4@Co-N-CMK3 reached 7.08 min-1 g-1, which was 2.2-93.2 folds higher than the reported ozonation catalysts. Co3O4@Co-N-CMK3 displayed the adsorption performance for ATZ and could activate O3 into O2- and OH effectively. The ≡Co2+ and ≡Co-Nx were main active sites. The synergy between Co3O4 and Co-N-CMK3 accelerated interface electron transfer, which was conducive to the redox of ≡Co2+/≡Co3+. The degradation pathway and intermediates toxicity were speculated using HPLC-MS measurement and Toxicity Estimation Software Tool simulation. The stability of Co3O4@Co-N-CMK3 for ATZ removal was certified by five consecutive experiments in catalytic ozonation. Moreover, the Co3O4@Co-N-CMK3/O3 process had good applicability to common anions and humic acid, real water and different pollutants.

Degradation of perfluorooctanoic acid (PFOA) using multiphase fenton-like technology by reduced graphene oxide aerogel (rGAs) combined with BDD electrooxidation

Perfluorooctanoic acid (PFOA) pollution in aqueous environments has attracted considerable attention. Due to its high chemical stability, PFOA is very difficult to degrade, posing potential risks to human health. Therefore, it is of significance to find an efficient and eco-friendly way to remove PFOA from the environment. In this study, reduced graphene oxide aerogel (rGA) was loaded with Fe3O4 and Cu nanoparticles (NPs) to obtain Fe3O4-rGA and Cu-rGA, which were then prepared into cathodes using the microbubble templating method. Heterogeneous Fenton-like system coupling Fe3O4/Cu-rGA cathodes and boron-doped diamond (BDD) electrodes were used to efficiently degrade PFOA in aqueous solutions. The parameters for PFOA degradation were optimized to be initial current density of 20.0 mA cm−2, initial electrolyte pH of 6, and electrolyte (Na2SO4) concentration of 10 mM. After 360 min, the Fe3O4-rGA and Cu-rGA systems achieved PFOA removal efficiencies of 98.25 % and 98.91 %, respectively, which were 16.7 % and 17.5 %, respectively, higher than that achieved by the system using a commercial graphite electrode. PFOA was completely removed, in 720 min and the F− production rates were 62.29 % and 65.48 % in the Fe3O4-rGA and Cu-rGA systems, respectively. PFOA degradation followed pseudo first-order kinetics in both systems (R2 > 0.99). The results of free radical quenching experiment and electrochemical performance experiment showed that the abundant active sites and excellent electrocatalytic properties of Fe3O4-rGA and Cu-rGAs promoted the formation of ⋅OH radicals for efficient PFOA degradation. In conclusion, coupling heterogeneous Fenton-like systems with Fe3O4 or Cu NPs-loaded rGA and BDD electrooxidation have great potential in the treatment of PFOA wastewaters in the future.

Absorption of HCl on sodium-based absorbents at medium and high temperatures: The effect of competing absorption of SO2 and H2O

The utilization of sodium bicarbonate (NaHCO3) as a solid reactant for the mitigation of acidic pollutants from industrial flue gas streams represents a straightforward and efficient process solution. The paper addresses the problem of medium- to high-temperature flue gas dechlorination by investigating the effects of base particle size, temperature, water vapour and different flue gas fractions on the removal of HCl from simulated flue gases by NaHCO3 in a fixed-bed reactor, and the effects of the presence of SO2 and H2O on the chlorination reactivity of NaHCO3 are also investigated by density functional theory (DFT) calculations. The adsorption results implied that 300 °C was the optimum temperature for HCl removal by NaHCO3 in a reaction system not affected by SO2 or H2O; The higher the HCl concentration, the greater the HCl capture, but when the concentration is too high, due to the dense product layer makes the HCl gas molecules to the internal diffusion is blocked, the dechlorination effect becomes poor. The smaller the particle size of NaHCO3, the better the removal of HCl. In the system containing SO2, theoretical calculations based on density functional theory show that the presence of SO2 affects the exchange of electrons between the Cl atoms in HCl and Na2CO3, and the bonding ability of the Na-Cl bond is weakened, thus weakening the dechlorination ability of Na2CO3; However, SO2 has little effect on HCl removal at the same concentration, due to the fact that HCl rapidly consumes the easily accessible surface of the absorber and SO2 must diffuse deeper into the particles for the reaction to occur, suggesting a preferred reaction between HCl and NaHCO3. After the addition of H2O, the adsorption energy of HCl on the surface of Na2CO3(200) was greater than the adsorption energy of SO2 on the surface of Na2CO3(200), and HCl was preferentially adsorbed on the surface of Na2CO3(200), which preferentially reacted with the absorber. These findings help to elucidate the principle of HCl absorption by NaHCO3 and the competition mechanism between HCl and SO2, and improve the theoretical knowledge of acid gas absorption by NaHCO3.