Assessment of sources and health risks of heavy metals in metropolitan household dust among preschool children: The LEAPP-HIT study.

The most common construction material used in Taiwan is concrete, potentially contaminated by geologic heavy metals (HMs). Younger children spend much time indoors, increasing HM exposure risks from household dust owing to their behaviors. We evaluated arsenic (As), cadmium (Cd), and lead (Pb) concentrations in fingernails among 280 preschoolers between 2017 and 2023. We also analyzed HM concentrations, including As, Cd, Pb, chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), iron (Fe), and manganese (Mn), in 90 household dust and 50 road dust samples from a residential area where children lived between 2019 and 2021 to deepen the understanding of sources and health risks of exposure to HMs from household dust. The average As, Cd, and Pb concentrations in fingernails were 0.12 ± 0.06, 0.05 ± 0.05, and 0.95 ± 0.77 µg/g, respectively. Soil parent materials, indoor construction activities, vehicle emissions, and mixed indoor combustion were the pollution sources of HMs in household dust. Higher Cr and Pb levels in household dust may pose non-carcinogenic risks to preschoolers. Addressing indoor construction and soil parent materials sources is vital for children's health. The finding of the present survey can be used for indoor environmental management to reduce the risks of HM exposure and avoid potential adverse health effects for younger children.

Oral and inhalation bioaccessibility of mercury in contaminated soils and potential health risk to the kidneys and neurodevelopment of children in Taiwan.

Health risk assessments of exposure to mercury (Hg) from soils via ingestion and inhalation are indispensable for Taiwanese people living in the vicinity of Hg-contaminated sites. In this study, anthropogenic soils were collected from various polluted sources in Taiwan. In vitro oral and inhalation bioaccessible fractions of Hg were analyzed to avoid from overestimating the exposure risk. Discrepancies in oral and inhalation bioaccessible levels of Hg in soils were found using different in vitro assays with different pH levels and chemical compositions. The freshly contaminated soil (soil S7) polluted by chlor-alkali production activity sampled before the site was remediated had the highest total Hg concentration of 1346 mg/kg, with the highest oral bioaccessibility of 26.2% as analyzed by SW-846 Method 1340 and inhalation bioaccessibility of 30.5% as analyzed by modified Gamble's solution. The lesser extent of aging of Hg in soil S7 increased the Hg availability for humans, which was also found based on results of a sequential extraction procedure. Results of the hazard quotient showed that soil ingestion was the main pathway causing non-carcinogenic risks for children and adults. Children were also exposed to higher risks than were adults due to higher frequencies of hand-to-mouth behaviors and lower body weights. Furthermore, hazard index results adjusted for oral and inhalation bioaccessible Hg were lower than those obtained based on the total Hg content; however, an unacceptable value of the non-carcinogenic risk (> 1) for children living near soil S7 was still observed. This study suggests that children living near sites polluted for a short period of time may suffer potential renal effects regardless of the bioaccessibility. Our findings provide suggestions for decision makers on setting new strategies for managing risks of Hg-contaminated soils in Taiwan.

Degradation of trichloroethylene by double dielectric barrier discharge (DDBD) plasma technology: Performance, product analysis and acute biotoxicity assessment.

Trichloroethylene is carcinogenic and poorly degraded by microorganisms in the environment. Advanced Oxidation Technology is considered to be an effective treatment technology for TCE degradation. In this study, a double dielectric barrier discharge (DDBD) reactor was established to decompose TCE. The influence of different condition parameters on DDBD treatment of TCE was investigated to determine the appropriate working conditions. The chemical composition and biotoxicity of TCE degradation products were also investigated. Results showed that when SIE was 300 J L-1, the removal efficiency could reach more than 90%. The energy yield could reach 72.99 g kWh-1 at low SIE and gradually decreased with the increase of SIE. The k of the Non-thermal plasma (NTP) treatment of TCE was about 0.01 L J-1. DDBD degradation products were mainly polychlorinated organic compounds and produced more than 373 mg m-3 ozone. Moreover, a plausible TCE degradation mechanism in the DDBD reactors was proposed. Lastly, the ecological safety and biotoxicity were evaluated, indicating that the generation of chlorinated organic products was the main cause of elevated acute biotoxicity.

Microbial community evolution and functional trade-offs of biofilm in odor treatment biofilters.

Biofilters inoculated with activated sludge are widely used for odor control in WWTP. In this process, biofilm community evolution plays an important role in the function of reactor and is closely related to reactor performance. However, the trade-offs in biofilm community and bioreactor function during the operation are still unclear. Herein, an artificially constructed biofilter for odorous gas treatment was operated for 105 days to study the trade-offs in the biofilm community and function. Biofilm colonization was found to drive community evolution during the start-up phase (phase 1, days 0-25). Although the removal efficiency of the biofilter was unsatisfactory at this phase, the microbial genera related to quorum sensing and extracellular polymeric substance secretion led to the rapid accumulation of the biofilm (2.3 kg biomass/m3 filter bed /day). During the stable operation phase (phase 2, days 26-80), genera related to target-pollutant degradation showed increases in relative abundance, which accompanied a high removal efficiency and a stable accumulation of biofilm (1.1 kg biomass/m3 filter bed/day). At the clogging phase (phase 3, days 81-105), a sharp decline in the biofilm accumulation rate (0.5 kg biomass/m3 filter bed /day) and fluctuating removal efficiency were observed. The quorum quenching-related genera and quenching genes of signal molecules increased, and competition for resources among species drove the evolution of the community in this phase. The results of this study highlight the trade-offs in biofilm community and functions during the operation of bioreactors, which could help improve bioreactor performance from a biofilm community perspective.

Using recoverable sulfurized magnetic biochar for active capping to remediate multiple heavy metal contaminated sediment.

Due to anthropogenic activities, heavy metals are discharged into the hydrosphere and deposit onto the sediment. Heavy metals remobilize through physical disturbance and change in environmental conditions, posing a risk to environments and human health. Among several remediation methods, active layer capping is considered to be more feasible due to its financial and technical advantages; however, its long-term effects remain unknown. To overcome this problem, this work applied a novel, recoverable amendment, sulfurized magnetic biochar (SMBC), to remediate multiple heavy metal (Cu, Ni, Zn, Cr, Hg, and MeHg) contaminated sediment. Physiochemical characterization shows magnetite (Fe3O4) crystalline in both magnetic biochar (MBC) and SMBC, with such characteristics resulting in a greater surface area (324.9 and 346.3 m2/g) than BC (39.6 m2/g) and SBC (65.0 m2/g). FeS crystalline was also observed in SMBC, which plays an important role in controlling heavy metal release from sediment. Microcosm experiments indicated the effectiveness of SMBC in lowering aquatic Cu, Ni, Zn, Hg, and MeHg releases was significantly greater than the other three biochar materials. Notably, the recovery of SMBC by magnetism was 87%, demonstrating the exceptional recoverability of SMBC from seawater and sediment. Based on its robust capability in lowering Cu, Ni, Zn, Hg, and MeHg release and excellent recoverability from seawater and sediment, this technique represents a practical alternative to conventional approaches for heavy metal immobilization from sediment.

Novel applications of vacuum distillation for heavy metals removal from wastewater, copper nitrate hydroxide recovery, and copper sulfide impregnated activated carbon synthesis for gaseous mercury adsorption.

Hydrometallurgical processing of electronic waste produces copper (Cu)-containing wastewater. Recycling of Cu is thus crucial, as it reduces the Cu impact on the environment, and increases Cu sustainability in industry. Vacuum distillation provides excellent performance in both metals removal from aqueous solution, metal recovery, and metal impregnation to porous material. Thus, this work aimed to both utilize a vacuum distillation to remove heavy metals (Cu, Na, Ni, Zn and Fe) and recover copper nitrate hydroxide (Cu2NO3(OH)3) from Cu-containing wastewater in industrial applications (e.g., mordant agent in dyeing and pigment for glass), as well as prepare copper sulfide (CuS) impregnated activated carbon for mercury (Hg0) adsorption. The experimental results indicated a vacuum distillation metals removal efficiency of over 99.99 % at 60 °C and -72 cm Hg. Additionally, the copper nitrate hydroxide (Cu2NO3(OH)3) crystalline solid derived from the vacuum distillation process achieved 77 % purity, and the copper sulfide impregnated activated carbon (CuSAC) adsorbents were prepared by adding activated carbon (AC) during the vacuum distillation process. In adsorption tests, 50 % CuSAC exhibited the greatest gaseous mercury (Hg0) adsorption performance, and it was noted that a high adsorption temperature of 175 °C negatively impacted Hg0 adsorption of 50 % CuSAC due to mercury sulfide (HgS) decomposition. Furthermore, in a simulated flue gas (SFG) environment, Hg0 capture by CuSAC was shown to be slightly obstructed. In addition, mercury temperature-programmed desorption (Hg-TPD) identified that HgS was the dominant species among adsorbed Hg species of Hg-laden 50 % CuSAC, indicating that Hg0 capture of CuSAC was mainly facilitated by sulfur active sites. As such, the vacuum distillation technique proved to efficiently remove metals and leads to successful preparation of adsorbent for Hg. Therefore, the process is an effective treatment method for Cu-containing wastewater, and can be practically applied to capture or recycle Cu in the industry in the future.

Microbial community regulation and performance enhancement in gas biofilters by interrupting bacterial communication.

BACKGROUND: Controlling excess biomass accumulation and clogging is important for maintaining the performance of gas biofilters and reducing energy consumption. Interruption of bacterial communication (quorum quenching) can modulate gene expression and alter biofilm properties. However, whether the problem of excess biomass accumulation in gas biofilters can be addressed by interrupting bacterial communication remains unknown. RESULTS: In this study, parallel laboratory-scale gas biofilters were operated with Rhodococcus sp. BH4 (QQBF) and without Rhodococcus sp. BH4 (BF) to explore the effects of quorum quenching (QQ) bacteria on biomass accumulation and clogging. QQBF showed lower biomass accumulation (109 kg/m3) and superior operational stability (85-96%) than BF (170 kg/m3; 63-92%) at the end of the operation. Compared to BF, the QQBF biofilm had lower adhesion strength and decreased extracellular polymeric substance production, leading to easier detachment of biomass from filler surface into the leachate. Meanwhile, the relative abundance of quorum sensing (QS)-related species was found to decrease from 67 (BF) to 56% (QQBF). The QS function genes were also found a lower relative abundance in QQBF, compared with BF. Moreover, although both biofilters presented aromatic compounds removal performance, the keystone species in QQBF played an important role in maintaining biofilm stability, while the keystone species in BF exhibited great potential for biofilm formation. Finally, the possible influencing mechanism of Rhodococcus sp. BH4 on biofilm adhesion was demonstrated. Overall, the results of this study achieved excess biomass control while maintaining stable biofiltration performance (without interrupting operation) and greatly promoted the use of QQ technology in bioreactors. Video Abstract.

Boosting catalytic stability for VOCs removal by constructing PtCu alloy structure with superior oxygen activation behavior.

The elimination of volatile organic compounds (VOCs) emitted from the process of industry production is of great significance to improve the atmospheric environment. Herein the catalytic oxidation of the toluene and iso-hexane mixture, as the typical components from furniture paint industry, and the enhancement in the catalytic stability for toluene oxidation were investigated in detail. The formation rate of active oxygen species was very important for the development of the catalyst with high catalytic stability. Compared with the Pt/M catalyst, the Pt-Cu/M catalyst owned stronger ability of VOCs adsorption and gaseous oxygen activation by introducing additional sites for activating O2. The Langmuir-Hinshelwood (adsorbed oxygen) and Mars-van Krevelen (lattice oxygen) mechanism existed in toluene oxidation over the present Pt/M and Pt-Cu/M catalysts, respectively. The change in the involved active oxygen species during toluene oxidation was resulted from the Pt-Cu alloy structure. In addition to the adsorption of O2, a part of active lattice oxygen species can also be replenished by the migration of bulk lattice oxygen over Pt-Cu/M. With a rise in the reaction temperature, weakly adsorbed iso-hexane could be timely reacted with the more active lattice oxygen species to keep the catalytic stability over the Pt/M and Pt-Cu/M catalysts. Generally, we not only prepared a promising material for the catalytic removal of VOCs from the furniture paint industry, but also provided a new strategy for the generation of active oxygen species, making the catalyst exhibit high catalytic oxidation stability.

Associations of maternal food safety-related risk perceptions and protective behaviors with daily mercury intake and internal doses of Taiwanese women and their preschool children.

Mercury (Hg) is a well-known toxicant that can affect children's neurodevelopment. This study attempted to evaluate the internal dose of Hg in hair and fingernails and external Hg exposure from dietary consumption in 283 pairs of mothers and their children aged under 6 years in Taiwan. Mean Hg levels in hair and fingernail samples were 1.07 ± 0.67 and 0.42 ± 0.34 µg/g for mothers, and 1.11 ± 1.22 and 0.36 ± 0.26 µg/g for children, respectively. Our results showed that 42% of mothers and 41% of children had hair Hg levels exceeding the US Environmental Protection Agency recommended value of 1 µg/g. Hg exposure in children was greater than that of their mothers. Estimated daily intake (EDI) levels of Hg among preschool children were 3.3-times higher than those of their mothers. A sensitivity analysis indicated that fish consumption was the main potential factor of Hg exposure among both mothers and their children. External Hg exposure using estimated daily dietary ingestion by mothers was a surrogate for internal hair Hg concentrations. However, poor correlations were found between EDI Hg levels and hair Hg levels among children aged 4-6 years. Exposure sources from food and other media, such as soil and dust, need to be considered to arrive at more-valid risk assessments for younger children's exposure to Hg. Children of mothers who did not have food safety-related risk perceptions or protective behaviors had significantly higher hair Hg concentrations compared to children whose mothers had risk perceptions and protective behaviors. Hg exposure of women of childbearing age and preschool children in Taiwan is still an area of great concern. Providing food safety information and risk-benefits of fish consumption for mothers may avoid harm to the developing nervous systems of their children.

Catalytic stability enhancement for pollutant removal via balancing lattice oxygen mobility and VOCs adsorption.

Manganese oxide supported Pt single atoms (Pt1/MnOx) are prepared by the molten salt method. Catalytic oxidation of toluene and iso-hexane, typical emissions from furniture paints industry, is tested. Pt1/MnOx shows poor and high catalytic stability for toluene and iso-hexane oxidation, respectively. Enhancement in the catalytic stability for toluene oxidation is observed after the hydrogen reduction treatment of Pt1/MnOx at 200 °C. The hydrogen treated catalyst possesses the weaker Mn-O bonds and lower coordination number of PtO, with superior mobility of lattice oxygen and appropriate toluene adsorption. Balancing lattice oxygen mobility and volatile organic compounds adsorption is important for the catalytic stability of Pt1/MnOx. For the oxidation of toluene and iso-hexane mixture, owing to the competitive adsorption, iso-hexane oxidation is greatly inhibited, while toluene oxidation is not influenced. The present Pt1/MnOx catalyst holds promising prospect in furniture paints industry applications because of high catalytic stability and water resistance ability.

Estimation of Soil and Dust Ingestion Rates from the Stochastic Human Exposure and Dose Simulation Soil and Dust Model for Children in Taiwan.

This study focuses on estimating the probabilistic soil and dust ingestion rates for children under 3 years old by the Stochastic Human Exposure and Dose Simulation Soil and Dust (SHEDS-S/D) model developed by the U.S. Environmental Protection Agency. The health risk of children's exposure to heavy metals through soil and dust ingestion and dermal absorption was then assessed in three exposure scenarios. In the exposure scenario of direct contact with soil, the average soil and dust ingestion rates for children aged 24 to 36 months were 90.7 and 29.8 mg day-1 in the sand and clay groups, respectively. Hand-to-mouth soil ingestion was identified as the main contributor to soil and dust ingestion rates, followed by hand-to-mouth dust ingestion and object-to-mouth dust ingestion. The soil-to-skin adherence factor was the most influential factor increasing the soil and dust ingestion rate based on a sensitivity analysis in the SHEDS-S/D model. Furthermore, the modeled soil and dust ingestion rates based on the SHEDS-S/D model were coincident with results calculated by the tracer element method. Our estimates highlight the soil ingestion rate as the key parameter increasing the risk for children, while a higher frequency of hand washing could potentially reduce the risk.

Gaseous mercury re-emission from wet flue gas desulfurization wastewater aeration basins: A review.

Wet flue gas desulfurization (WFGD) simultaneously removes Hg and SO2 from coal-fired power plant flue gas streams. Hg0 re-emission occurs when the dissolved Hg(II) is converted to a volatile form (i.e., Hg0) that can be subsequently emitted into the ambient air from WFGD wastewater aeration basins. Others have shown that Hg0 re-emission depends on pH, temperature, ligands (Cl, Br, I, F, SO32-, SO42-, NO3-, SCN-, and ClO-), O2, minerals (Se and As), and metals (Fe and Cu) in WFGD wastewater. Still others have shown Hg0 re-emission restriction via inhibitor addition (adsorbents and precipitators). This is the first review that summarizes the complex and inconsistently reported Hg0 re-emission mechanisms, updates misconceptions related to Hg(II) complexation and reduction, and reviews applications of inhibitors that convert aqueous Hg(II) into stable solid forms to prevent gaseous Hg0 formation and release.

A novel synthesis of sulfurized magnetic biochar for aqueous Hg(II) capture as a potential method for environmental remediation in water.

Due to public health threats resulting from mercury (Hg) and its distribution in the food chain, global restrictions have been placed on Hg use and emissions. Biochar is a porous, carbonaceous adsorbent typically derived from waste biomass or organic matter, making it an eco-friendly material for aqueous mercury (Hg(II)) control. Functionalization of biochar can improve performance in pollution control applications. In this work, carbonization, magnetization, and sulfurization of biochar were combined into a single heating step to prepare sulfurized magnetic biochar (SMBC) for Hg(II) removal from water. Results indicate that SMBC prepared at 600 °C adsorbed 8.93 mg/g Hg(II), more than materials prepared at 400, 500, 700, 800, and 900 °C. Additionally, Hg(II) adsorption onto SMBC was 53.0% and 11.5% greater than onto magnetic biochar (MBC) and biochar (BC), respectively. Hg(II) adsorption is shown to be favorable in acidic conditions (pH 3.5-5), thermodynamically spontaneous, and endothermic. Adsorption results fit the pseudo-second-order (R2 = 0.990 and the sum of squared error (SSE) = 5.382) and external mass transfer (R2 = 0.971 and SSE = 9.422) models. The partitioning coefficients were 4.964 mg/g/µM in freshwater, 0.176 mg/g/µM in estuary water, and 0.275 mg/g/µM in seawater, highlighting the importance of salinity in environmental remediation applications. In summary, SMBC can be readily prepared with minimal processing steps. The product is a robust adsorbent for Hg(II), and it can potentially be applied to remediate contaminated water/sediment/soil in the future.

Effects of soil lead exposure and land use characteristics on neurodevelopment among children under 3 years of age in northern Taiwan.

Lead (Pb) exposure increases the risks of neurodevelopmental disorders in children. Child-specific activities and land use scenarios may lead to elevated opportunities for Pb exposure through the soil. Therefore, we investigated hair and fingernail Pb concentrations among young children in northern Taiwan, in relation to soil Pb pollution and land use characteristics. We also explored the effect of the Pb exposure burden and land use scenarios on neurobehavioral development. In total, 139 healthy children under 3 years of age were recruited in October 2011 to April 2014. Pb levels in hair and fingernail samples were determined using an inductively coupled plasma/mass spectrometer. Pb concentrations in soils and land use types surrounding the children's homes were accessed by a geographic information system to identify any associations with hair Pb levels. The Bayley Scales of Infant and Toddler Development (Bayley-III) were used to evaluate the cognitive, language, and motor development of the children. A multivariable regression model was performed to assess the effects of soil Pb levels and land-use status on Pb exposure in children, as well as associations of Pb exposure and land-use scenarios with neurodevelopmental abilities. Geometric mean Pb concentrations in hair, fingernails, and soil were 2.9 ± 4.8 µg/g, 0.8 ± 5.1 µg/g, and 20.8 ± 4.3 mg/kg, respectively. The multivariable analysis indicated that soil Pb concentrations and green areas around residences had potential links with Pb exposure among children in northern Taiwan. Hair Pb concentrations were negatively associated with expressive language scores. Soil Pb exposure was positively associated with hair Pb concentrations. Land use types around the children's homes in northern Taiwan were associated with their neurodevelopment. Increased green areas were negatively associated with hair Pb concentrations. Living near a highway may have had negative impacts on gross motor scores. A healthy residence can avoid potential health risks for children during their early life.

Emissions, measurement, and control of odor in livestock farms: A review.

Odor emissions from intensive livestock farms have attracted increased attention due to their adverse impacts on the environment and human health. Nevertheless, a systematic summary regarding the characteristics, sampling detection, and control technology for odor emissions from livestock farms is currently lacking. This paper compares the development of odor standards in different countries and summarizes the odor emission characteristics of livestock farms. Ammonia, the most common odor substance, can reach as high as 4100 ppm in the compost area. Sampling methods for point and area source odor emissions are introduced in this paper, and odor analysis methods are compared. Olfactometers, odorometers, and the triangle odor bag method are usually used to measure odor concentration. Odor control technologies are divided into three categories: physical (activated carbon adsorption, masking, and dilution diffusion), chemical (plant extract spraying, wet scrubbing, combustion, non-thermal plasma, and photocatalytic oxidation), and biological (biofiltration, biotrickling, and bioscrubbing). Each technology is elucidated, and the performance in the removal of different pollutants is summarized. The application scopes, costs, operational stability, and secondary pollution of the technologies are compared. The generation of secondary pollution and long-term operation stability are issues that should be considered in future technological development. Lastly, a case analysis for engineering application is conducted.

Mercury speciation and mass distribution of coal-fired power plants in Taiwan using different air pollution control processes.

In this study, the mercury (Hg) emission, speciation, and mass distribution of four coal-fired power plants (CFPPs) located at central, southern, and northern Taiwan with various types of air pollution control devices were investigated. Gaseous Hg in the coal-combustion flue gas was sampled by using the Ontario Hydro method, and the solid and liquid samples were collected for understanding the Hg mass balance. The experimental results showed that the total Hg concentrations in flue gases at the inlets of selective catalytic reduction (SCR) varied from 2.984 to 4.692 µg Nm-3, while the total Hg concentrations in the flue gases at the stacks ranged from 0.240 to 0.675 µg Nm-3. These four CFPPs showed similar Hg speciation results at the stacks. The average Hg removal efficiencies of Plants 1 (SCR + electrostatic precipitator [ESP] + wet flue gas desulfurization [WFGD]), 2 (SCR + ESP + WFGD), 3 (SCR + bag filter (BF) + seawater flue gas desulfurization [SWFGD]) and 4 (SCR + BF + SWFGD) were 92.4%, 90.1%, 85.9%, and 84.8%, respectively. Coal was the major raw material in Hg input of CFPPs with a mass flow rate ranging 5.87-12.05 g hr-1. Elemental Hg (Hg0), accounting for 66.4%-97.1% of the total Hg, was the dominant species emitted to the atmosphere. The Hg mass balances for the four CFPPs varied from 86.0% to 117% of the Hg input, suggesting that good mass balances were obtained from the tested CFPPs.Implications: Mercury emissions from coal-fired power plant (CFPPs) have been greatly concerned and should thus be better comprehended. The present study examined the mercury speciation and mass distribution of four CFPPs located at Taiwan. Overall, these CFPPs had similar Hg speciation results at stack and Hg0 was the dominant species emitted to the atmosphere. The selective catalytic reduction (SCR) + electrostatic precipitator (ESP) + wet flue gas desulfurization (WFGD) system had the highest Hg removal efficiency and the Hg mass balances for the four CFPPs varied from 86.0 to 117%. This study helps better understanding the Hg emission inventory of CFPPs and provides useful information for selecting adequate air pollution control devices (APCDs) for Hg control.

Mercury vapor adsorption and sustainable recovery using novel electrothermal swing system with gold-electrodeposited activated carbon fiber cloth.

A novel electrothermal swing (ETS) system with gold-electrodeposited activated carbon fiber cloth (GE-ACFC) was developed to adsorb and sustainably recover low-concentration Hg0. GE-ACFC with an Au growth time of 1200 s displayed the largest Hg0 adsorption capacity and >90% removal efficiency. The Hg0 adsorption of GE-ACFC was dominated by physisorption via Au amalgamation. In contrast, Hg adsorption of untreated ACFC (RAW-ACFC) was mainly controlled by physisorption and chemisorption related to carbonyl groups. Nevertheless, both ACFCs could reach 100% ETS Hg0 regeneration. The Hg re-adsorption of GE-ACFC was stable, with efficiency >90% at different regeneration temperatures in three-cycle ETS experiments, but the Hg re-adsorption efficiencies of RAW-ACFC greatly decreased to only 60% after 250 â„ƒ regeneration, due to the formation of electrothermal hot spots in the ACFC. Because the thermal and electrical conductivity of GE-ACFC increased due to Au electrodeposition, the presence of electrothermal hot spots in GE-ACFC-1200s was minor. Simulation results showed that both pseudo-first-order and pseudo-second-order models fitted well to the desorption patterns of the GE-ACFC. Mass transfer model further suggested that intraparticle diffusion control was the rate-limiting step, with diffusion coefficients increased from the first to the third cycle for GE-ACFC.

Simultaneous aqueous Hg(II) adsorption and gaseous Hg0 re-emission inhibition from SFGD wastewater by using Cu and S co-impregnated activated carbon.

Seawater flue gas desulfurization (SFGD) has shown great effectiveness in the controlling of sulfur dioxide (SO2) emission and the removing of mercury (Hg) from flue gases of coal-fired power plants. Some problems pertaining to SFGD for Hg control, however, remain to be solved: (1) environmental impact from the discharge of Hg-containing seawater to the ocean, and (2) re-emission of gaseous Hg from the aeration tank to the atmosphere. This study synthesizes the copper/sulfur co-impregnated activated carbon (Cu-S-AC) to simultaneously capture aqueous Hg(II) and inhibit gaseous Hg0 re-emission from actual SFGD wastewater. Cu-S-AC exhibited greater Hg(II) adsorption than both raw activated carbon (AC) and sulfur-impregnated activated carbon (S-AC) at an initial Hg(II) concentration of higher than 8000 ng/L. The Hg(II) adsorption of Cu-S-AC was slightly greater at pH 7 and 8 than that under acidic conditions. The Hg(II) adsorption was well-fitted with both linear and Freundlich isotherms. The results of thermodynamic analyses veiled the endothermic and spontaneous adsorption of Hg(II) on Cu-S-AC. In addition, the pseudo-second-order equation provided the best correlation coefficient for the Hg(II) adsorption on Cu-S-AC. Notably, the increases of pH and temperature increased the Hg0 re-emission. Nevertheless, Cu-S-AC addition significantly inhibited the Hg0 re-emission (92%) from SFGD wastewater.

A short review of bioaerosol emissions from gas bioreactors: Health threats, influencing factors and control technologies.

Bioaerosols have widely been a concern due to their potential harm to human health caused by the carrying and spreading of harmful microorganisms. Biofiltration has been generally used as a green and effective technology for processing VOCs. However, bioaerosols can be emitted into the atmosphere as secondary pollutants from the biofiltration process. This review presents an overview of bioaerosol emissions from gas bioreactors. The mechanism of bioaerosols production and the effect of biofiltration on bioaerosol emissions were analyzed. The results showed that the bioaerosol emission concentrations were generally exceeded 104 CFU m-3, which would damage to human health. Biomass, inlet gas velocity, moisture content, temperature, and some other factors have significant influences on bioaerosol emissions. Moreover, as a result of the analysis done herein, different inactivation technologies and microbial immobilization of bioaerosols were proposed and evaluated as a potential solution for reducing bioaerosols emissions. The purpose of this paper is to make more people realize the importance of controlling the emissions of bioaerosols in the biofiltration process and to make the treatment of VOCs by biotechnology more environmentally friendly. Additionally, the present work intends to increase people's awareness in regards to the control of bioaerosols, including microbial fragment present in bioaerosols.