Filtration Of Pollutants Research Articles

Assessment of filtration efficiency and physiological responses of selected plant species to indoor air pollutants (toluene and 2-ethylhexanol) under chamber conditions.

Three common plant species (Dieffenbachia maculata, Spathiphyllum wallisii, and Asparagus densiflorus) were tested against their capacity to remove the air pollutants toluene (20.0mgm-3) and 2-ethylhexanol (14.6mgm-3) under light or under dark in chamber experiments of 48-h duration. Results revealed only limited pollutant filtration capabilities and indicate that aerial plant parts of the tested species are only of limited value for indoor air quality improvement. The removal rate constant ranged for toluene from 3.4 to 5.7Lh-1m-2 leaf area with no significant differences between plant species or light conditions (light/dark). The values for 2-ethylhexanol were somewhat lower, fluctuating around 2Lh-1m-2 leaf area for all plant species tested, whereas differences between light and dark were observed for two of the three species. In addition to pollutant removal, CO2 fixation/respiration and transpiration as well as quantum yield were evaluated. These physiological characteristics seem to have no major impact on the VOC removal rate constant. Exposure to toluene or 2-ethylhexanol revealed no or only minor effects on D. maculata and S. wallisii. In contrast, a decrease in quantum yield and CO2 fixation was observed for A. densiflorus when exposed to 2-ethylhexanol or toluene under light, indicating phytotoxic effects in this species.

Synthesis, Morphologies and Building Applications of Nanostructured Polymers.

Nanostructured polymers (NSPs) are polymeric materials in the size of nanoscale, normally consisting of nanoparticles, nanofibers, nanowires, nanospheres and other morphologies. Polymer nanoparticles (PNPs) can be fabricated either by physical methods (i.e., solvent evaporation, nanoprecipitation, salting out) or by direct nanosynthesis, using micro- or nanoemulsions with nanoreactor compartments to perform polymerization. Polymer nanofibers (PNFs) can be produced via various techniques and the most commonly used approach is electrospinning, whereby a charged solution of a polymer when exposed to an opposite high electric field is pulled into long thin nanofibers. NSPs in general exhibit enhanced properties such as excellent structural and mechanical properties, making them promising candidates for some particular building applications. A variety of PNFs have been developed and used for noise and air pollution filtration. Moreover, PNFs can also be fabricated with phase change materials which are usually employed for thermal energy storage in construction industry. In this review, we will summarize the morphologies and nanosynthesis methods of NSPs, in particular, PNPs and PNFs. In addition, representative NSPs mainly used in construction are introduced for building applications.

Long-term indoor air conditioner filtration and cardiovascular health: A randomized crossover intervention study

The association of short-term air pollution filtration with cardiovascular health has been documented. However, the effect of long-term indoor air conditioner filtration on the association between air pollution and cardiovascular health is still unclear. We recruited 200 homemakers from Taipei and randomly assigned 100 of them to air filtration or control intervention; six home visits were conducted per year from 2013 to 2014. The participants under air filtration intervention during 2013 were reassigned to control intervention in 2014. The air pollution measurements consisted of particulate matter less than or equal to 2.5μm in diameter (PM2.5) and total volatile organic compounds (VOCs); blood pressure was monitored for each participant during each visit. The following morning, blood samples were collected after air pollution monitoring. The blood samples were used to analyze biological markers, including high sensitivity-C-reactive protein (hs-CRP), 8-hydroxy-2′-deoxyguanosine (8-OHdG) and fibrinogen. Household information, including cleaning, cooking, and air conditioning, was collected by a questionnaire. Mixed-effects models were used to investigate the associations among air pollution measurements, blood pressure and biological markers. The results showed that increased levels of PM2.5 and total VOCs were associated with increased hs-CRP, 8-OHdG and blood pressure. The health variables were higher among participants in the control intervention phase than among those in the air filtration intervention phase. We concluded that air pollution exposure was associated with systemic inflammation, oxidative stress and elevated blood pressure. The long-term filtration of air pollution with an air conditioner filter was associated with cardiovascular health of adults.

Selection of optimized air pollutant filtration technologies for petrochemical industries through multiple-attribute decision-making

Selecting cost-effective and efficient air filtration technologies that ensure sustainable development is a challenge to national, regional and local policy makers. Various factors such as efficiency, maintainability, and design of the developed devices can affect the selection of optimized technologies. The present study aimed to select optimal technologies for air filtration devices in petrochemical industries through a multi-criteria decision-making (MADM) method based on a fuzzy model of Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). Five criteria (filtration efficiency, cost, maintainability, designability, and size) were used to rank air pollution control technologies designed to eliminate particulate matter (PM), volatile organic compounds (VOCs), and ammonia (NH3). According to the results, the research criteria had different weights for different air pollutants. High-efficiency particulate air (HEPA + pre collector) filters, plasma chemistry, and chemical absorption were identified as the most appropriate filtration methods for PM, VOCs, and NH3, respectively (coefficients = 0.923, 0.9586, and 0.867, respectively).

Population genetic structure of eelgrass (Zostera marina) on the Korean coast: Current status and conservation implications for future management.

Seagrasses provide numerous ecosystem services for coastal and estuarine environments, such as nursery functions, erosion protection, pollution filtration, and carbon sequestration. Zostera marina (common name “eelgrass”) is one of the seagrass bed-forming species distributed widely in the northern hemisphere, including the Korean Peninsula. Recently, however, there has been a drastic decline in the population size of Z. marina worldwide, including Korea. We examined the current population genetic status of this species on the southern coast of Korea by estimating the levels of genetic diversity and genetic structure of 10 geographic populations using eight nuclear microsatellite markers. The level of genetic diversity was found to be significantly lower for populations on Jeju Island [mean allelic richness (AR) = 1.92, clonal diversity (R) = 0.51], which is located approximately 155 km off the southernmost region of the Korean Peninsula, than for those in the South Sea (mean AR = 2.69, R = 0.82), which is on the southern coast of the mainland. South Korean eelgrass populations were substantially genetically divergent from one another (FST = 0.061–0.573), suggesting that limited contemporary gene flow has been taking place among populations. We also found weak but detectable temporal variation in genetic structure within a site over 10 years. In additional depth comparisons, statistically significant genetic differentiation was observed between shallow (or middle) and deep zones in two of three sites tested. Depleted genetic diversity, small effective population sizes (Ne) and limited connectivity for populations on Jeju Island indicate that these populations may be vulnerable to local extinction under changing environmental conditions, especially given that Jeju Island is one of the fastest warming regions around the world. Overall, our work will inform conservation and restoration efforts, including transplantation for eelgrass populations at the southern tip of the Korean Peninsula, for this ecologically important species.

Pairing micropollutants and clay-composite sorbents for efficient water treatment: Filtration and modeling at a pilot scale

Organically modified clay minerals have been widely developed, tested and employed as sorbents for organic pollutants. However, the process of pollutant-composite pairing is not commonly addressed, which would be valuable for efficient pollutant filtration by such sorbents. This study presents an approach for achieving efficient pollutant removal by large-scale composite filters, based on pairing chemically compatible pollutants and composites and by employing a predictive filtration model. The removal of three organic pollutants, simazine, sulfentrazone and diclofenac by lab-scale filtration columns containing one of three sorbents, a polymer-, micelle- or liposome-clay composite, was measured. Understanding the factors governing pollutant-organic modifier interactions enabled to pair an efficient sorbent to each pollutant. The high removal (80%) of simazine by the polymer composite, was attributed to hydrogen bonds and π-π interactions, compared to less than 20% removal by the surfactant composites. The removal of the anionic diclofenac (pKa=4.1) was mainly governed by electrostatic attraction, explaining its high removal by the most positively charge sorbent, the liposome composite. Sulfentrazone (pKa=6.5) removal was mostly affected by micellar solubilization and upon its removal, the zeta potential of the micelle-composite was not reduced as obtained for diclofenac removal. The filtration of the successful pairs was modelled to determine sorbent capacity and adsorption and desorption rate constants. The pilot filtration experiments were well described by the model and demonstrated efficient removal of paired pollutants and sorbents. Model simulations predicted promising treatment at environmental pollutant concentrations in the μgL−1 range. This pairing approach along with model calculations can be a strong and valid tool for efficient pollutant-sorbent filtration.

“Green” nano-filters: fine nanofibers of natural protein for high efficiency filtration of particulate pollutants and toxic gases

By combining the significant properties of nanofibers and the multi-functionality of pure proteins, “green” multifunctional air-filters with high removal efficiency of particulates and toxic gases is achieved.

Numerical modeling of an electrically enhanced membrane bioreactor (MBER) treating medium-strength wastewater

In this paper, a numerical model of an electrically enhanced membrane bioreactor (MBER) was developed. MBER is a reactor that combines biological decomposition, membrane filtration and electrocoagulation of wastewater pollutants in a hybrid unit. To assess its design, the final contents and removal efficiencies of organics, nutrients, and metals were carried out using varying influent compositions. In a 60-day test of a laboratory-scale MBER, experimental results were used to calibrate and validate the model. The modeling results were in agreement with the experimental data and showed that the MBER can remove 99% of total phosphorus (TP), 99.9% of chemical oxygen demand (COD), 91% of total nitrogen (TN), 79% of nickel (Ni), 89% of iron (Fe), and 80% of chromium (Cr), using a current density of 15 A/m2 intermittently supplied in a cycle of 5 min ON and 15 min OFF.

(Invited) Natural Fiber Welded Composites: Electrodes and Capacitors

Natural fiber welding (NFW) is a method whereby solvent blends and process conditions are tailored to selectively swell and mobilize the biopolymers of fibrous, natural materials for functional (chemical and physical) modification.1-4 For example, careful control of solvent to substrate ratio, solvent composition (efficacy), as well as the time, temperature, pressure, and location of solvent exposure results in robust composites composed of fibrous substrates that are fused without glues or resins. The biopolymers within the cores of individual fibers may be demonstrated to retain their native structures and thus functionalities. In addition to unique fiber blends, other materials such as conductive carbons, magnets, fire retardants, et cetera may be incorporated during processing to yield highly functional composites that are sustainably produced and exhibit low embodied energy. In this presentation, we will discuss NFW processes to create flexible carbon-containing yarns for wearable supercapacitor applications. In particular, repeatable, scalable processes that generate composites that perform on par with similar state of the art devices reported in the literature. Given that these composites are based on truly ‘green’ cellulosic and lignocellulosic substrates (cotton and bamboo) and utilizing a nonfluorinated binder (cellulose from cotton), we believe this to be a significant breakthrough for the prospects of wearable energy storage.5-8 In addition, we will discuss the prospects for large scale nonwoven bio-based electrodes produced from inexpensive agricultural wastes and suitable for any number of important applications (e.g., filtration of pollutants from air and water). Acknowledgements: Portions of this work were funded by the Air Force Office of Scientific Research. Any opinions, findings, conclusions or recommendations expressed in the material are those of the authors and do not necessarily reflect the views of the U.S Navy or U.S Air Force. K. Jost acknowledges support from the DoD National Defense Science and Engineering Graduate (NDSEG) Fellowship.

Design and performance study of hybrid photocatalytic reactor-PVDF/MWCNT nanocomposite membrane system for treatment of petroleum refinery wastewater

This study focuses on the design and performance of a hybrid system consisting of a photocatalytic reactor and a membrane permeation cell. Initially, an ultraviolet lamp was installed in the photocatalytic reactor to decompose the organic pollutants in the presence of 200ppm titanium-dioxide (TiO2). Individual hydrocarbon pollutants were identified by gas chromatography–mass spectrometry (GC–MS) analysis of wastewater samples. Polyvinylidene fluoride (PVDF)/multi-walled carbon nanotube (MWCNT) nanocomposite membranes were fabricated to enhance the rejection, flux and fouling resistance for full filtration of pollutants from photocatalytic reactor such as decomposed refinery wastewater and TiO2 photocatalyst. The nanocomposite membranes were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The TiO2 cross-over during permeation was detected by using an atomic adsorption spectrometer, which proved that TiO2 rejection was more than 99% for oxidized MWCNT nanocomposite membranes. Furthermore, GC–MS analysis was concluded over 90% decomposition which occurred by photocatalytic reaction and practically all pollutants were removed by ultrafiltration permeation cell. The nanocomposite membrane with 1.0wt.% of oxidized MWCNTs incorporated in PVDF matrix was found to be the best nanocomposite membrane among all of the fabricated membranes for the filtration purposes, due to the over 99% rejection and excellent anti-fouling property.

The Impact of Stormwater Runoff on Nutrient Removal in Sand Columns

Mulch layer also assists filtration of pollutants mainly larger sediment particles in bioretention. The objective is to evaluate the efficiency of bioretention facilities in removing nitrogen and phosphorus by varying the types of mulch layers through sand column. 200 mm filter media cells consisted of river sand with composited fine and coarse sand. Three types of mulch layer wood chip, tea waste and coconut husk were applied at the top of the sand layer at 50 mm depth. Runoff was monitored and analyzed to measure nutrient concentration within six hours. Woodchip showed the highest capability in removing phosphorus by 60.3% as compared to tea wastes and coconut husk. Lower removal efficiency was seen for nitrogen for all mulch materials. Tea waste provides additional nitrogen in effluent concentration. Coconut husk has a potential to be applied as mulch materials based on its capability even wood chip was seen to be favorably materials.

Insulated Conducting Cantilevered Nanotips and Two-Chamber Recording System for High Resolution Ion Sensing AFM

Biological membranes contain ion channels, which are nanoscale pores allowing controlled ionic transport and mediating key biological functions underlying normal/abnormal living. Synthetic membranes with defined pores are being developed to control various processes, including filtration of pollutants, charge transport for energy storage, and separation of fluids and molecules. Although ionic transport (currents) can be measured with single channel resolution, imaging their structure and ionic currents simultaneously is difficult. Atomic force microscopy enables high resolution imaging of nanoscale structures and can be modified to measure ionic currents simultaneously. Moreover, the ionic currents can also be used to image structures. A simple method for fabricating conducting AFM cantilevers to image pore structures at high resolution is reported. Tungsten microwires with nanoscale tips are insulated except at the apex. This allows simultaneous imaging via cantilever deflections in normal AFM force feedback mode as well as measuring localized ionic currents. These novel probes measure ionic currents as small as picoampere while providing nanoscale spatial resolution surface topography and is suitable for measuring ionic currents and conductance of biological ion channels.

Bioremediation Mariculture in Zanzibar, Tanzania: A Viability Assessment of Using Bath Sponge and Pearl Oyster Farms to Filter Highly Polluted Waters in the Zanzibar Channel

Bioremediation of polluted water off the coastline of the urban center of Zanzibar—Stone Town, Unguja—was assessed for implementation feasibility through bath sponge and pearl oyster mariculture. A vast research base of the city’s coastal area exists, including the pollution concentrations at various locations, the ramifications of this pollution on the fringing ecosystems, and the relevant water circulation system of eddies and passageways produced by the north flowing East African Counter Current. In following the experimental examples of bioremediation projects around the world, this study tested facets of the filtration abilities of marine sponges and oysters. Both organisms suggested strong pollution filtration abilities. Phosphate concentrations decreased from an average of 3.93 ug/L (micrograms per liter) to 1.33 and 1.73 ug/L for sponges and oysters, respectively. Unique capabilities of each organism were displayed in the experiments. The marine sponges visibly eliminated the turbidity level in the 36-hour study period. The marine oysters were suggested to chemically convert the dissolved nitrates through the tested increase in ammonium concentration from an average of 4.01 ug/L in the contaminated water to and average replicate concentration of 21.5 ug/L. The respective mariculture techniques were examined along with management logistics to assess the viability of implementing the mariculture for the pollution remediation. It was concluded that the mariculture techniques could be feasibly established by carefully collaborating with the nature of the pollution distribution, the consultation and aid of private and governmental organizations and further background scientific research.

Feasibility of bioengineered two-stages sequential batch reactor and filtration–adsorption process for complex agrochemical effluent

In the present study, the feasibility of a bioengineered two-stages sequential batch reactor (BTSSBR) followed by filtration-adsorption process was investigated to treat the agrochemical effluent by overcoming factor affecting process stability such as microbial imbalance and substrate sensitivity. An air stripper stripped 90% of toxic ammonia, and combined with other streams for bio-oxidation and filtration-adsorption. The BTSSBR system achieved bio-oxidation at 6 days hydraulic retention time by fending off microbial imbalance and substrate sensitivity. The maximum reduction in COD and BOD by heterotrophic bacteria in the first reactor was 87% and 90%, respectively. Removal of toxic ammoniacal-nitrogen by autotrophic bacteria in a post-second stage bio-oxidation was 97%. The optimum filtration and adsorption of pollutants were achieved at a filtration rate of 10 and 9 m(3)m(-2)h(-1), respectively. The treatment scheme comprising air stripper, BTSSBR and filtration-adsorption process showed a great promise for treating the agrochemical effluent.

Solving a model for 1-D, three-phase flow vertical equilibrium processes in a homogeneous porous medium by means of a Weighted Essentially Non Oscillatory numerical scheme

Mathematical models of multi-phase flow are useful in some engineering applications like enhanced oil recovery, filtration of pollutants into subsurface, etc. In this work, we derive a mathematical model for the motion of one-dimensional three-phase flow in a porous medium under the condition of vertical equilibrium, which can be viewed as an extension of some two-phase flow models described in the literature.Our model involves a system of two partial differential equations in the form of viscous conservation laws, whose solutions may contain very sharp transitions. We show that a high-order/high resolution Weighted Essentially Non Oscillatory scheme is an appropriate tool to discretize the buoyancy flux and obtain a well resolved representation of the solution of the model. In addition, we show that the efficiency of the scheme may be improved by using Implicit–Explicit (IMEX) strategies, where the parabolic terms are handled by an implicit discretization.

Herbicide occurrence in riparian soils and its transporting risk in the Songhua River Basin, China

A riparian zone is the interface between land and a river or stream. Riparian zones are major elements of ecosystems. However, human conversion of riparian land to agricultural uses has reduced the ecological benefits of riparian land such as water and pollutant filtration. Over 80 % of the original riparian area has been lost from North America and Europe over the past 200 years. Intensive land use along riparian areas has increased soil erosion and, in turn, sedimentation in rivers. Intensive land use has also increased the transfer of unused fertilizers, e.g., nitrates and pesticides in river water. We therefore studied pesticide transfer and soil erosion in riparian zones of the Songhua River Basin in China. For that, we identified land use type and measured herbicide residues of acetochlor and atrazine in riparian soils and soil columns of samples from 248 stations. We also modeled the risk of herbicide transfer. Our results show that herbicides were detected in 97 % of the samples, evidencing a widespread contamination. Acetochlor residue concentrations in soils are 26.10 μg/kg for farm land, 1.76 μg/kg for grass land, 1.46 μg/kg for forest land, and 2.48 μg/kg for bare land on average. Atrazine residue concentrations in soils are 11.28 μg/kg for farm land, 0.51 μg/kg for grass land, not detected in forest land, and 0.13 μg/kg for bare land on average. Atrazine residue concentration increased in riparian agricultural soils below 25 cm; whereas atrazine residue concentration of grassland soils showed a decrease. We found also that the highest risk of soil erosion and herbicide transfer is located in the middle reach of the Songhua River.

New multi-metric Salt Marsh Sediment Microbial Index (SSMI) application to salt marsh sediments ecological status assessment

Salt marshes are very important areas for biogeochemical cycling, sediment accretion, pollution filtration and retention and erosion and stabilization of the river margins. The high organic matter content in the salt marsh plant sediments along with the radial oxygen diffusion provided by these halophyte root systems gather the ideal conditions for the development of a microbial rhizosphere community. Due to the quick feedback of the microbial communities to an environmental change, these organisms become important monitors for environmental impact assessment. A Salt marsh Sediment Microbial Index (SSMI) that reflected physical–chemical and microbial parameters was applied to plant rhizosphere sediments of five salt marshes from three important water bodies from Portugal. The SSMI revealed to be plant-independent evaluating efficiently the different marshes according to their maturity degree and disturbance influence. Mature salt marshes SSMI classification grouped all the systems at this development stage, while the younger salt marshes are classified in different groups according to their evolution degree. Also the impact degree is reflected at this level discriminating also the more adversely impacted salt marshes. Being a multi-metric index, the SSMI sub-metrics are also susceptible of ecological interpretation, giving important backstage information about the underlying biogeochemical cycling processes.

Multifunctional graphene oxide–TiO2 microsphere hierarchical membrane for clean water production

The severe scarcity of clean water is arousing concern worldwide. The development of clean water production heavily relies on membrane technology, although the performance of current membranes is significantly restricted by membrane fouling. In this work, a novel graphene oxide (GO)–TiO2 microsphere hierarchical membrane was fabricated through assembling GO–TiO2 microsphere composite on the surface of a polymer filtration membrane. This kind of membrane possesses the multifunction of concurrent water filtration and degradation of pollutants. GO sheets play double roles in GO–TiO2 membrane, including (1) cross linker for individual TiO2 microspheres; and (2) electron acceptor to enhance photocatalytic activity. Hence, this novel membrane shows sustainably high permeate flux due to the hierarchical membrane structure, high photodegradation activity and no membrane fouling. The excellent performance of this GO–TiO2 hierarchical membrane indicates its promising potential in clean water production field.

Facile Fabrication of Open-Ended High Aspect-Ratio Anodic TiO<sub>2</sub> Nanotube Films and their Applications

In the present work, we demonstrated a facile process to prepare an open-ended high aspect-ratio TiO2 nanotube films through separating the anodic TNT array from the Ti substrate by a small reverse bias and opening the tube bottom by a chemical etching. The possible mechanisms of film detachment and pore opening processes have been briefly discussed. Such a process allows controlling the open-ended morphology by the straightforward chemical etching, which shows great potential in many applications, such as flow-through photocatalytic reactions, biofiltration, and diffusion controlling, and so on. An example using the open-ended TNT films is finally given as a flow-through photocatalytic reactor. The photocatalytic film has been shown to have multiple functions such as physical separation of contaminants, filtration, and decomposition of organic pollutants during diffusion.

Turbulent transport of airborne pollutants in a residential room with a novel air conditioning unit

Modeling on indoor air quality is performed considering the effect of a new window-type air conditioner, which is a promising way toward compromising energy consumption and residential air environment. Sensitivity analysis of the actual operating situations has been implemented, including the total fresh air supply and the full room air recirculation. The effects of supplying air flow rate, pollutant filtration efficiency, and indoor thermal buoyancy on the airborne pollutant transports are also illustrated. The numerical results demonstrate that the reduction of indoor pollutant levels can be accomplished either by increasing the fresh air ratio, or by increasing filtered removal efficiency, or by increasing the supplying airflow rate, or by decreasing the strength of indoor heating source. The indoor contaminant concentration asymptotically approaches to a small value for the situation of full fresh air supply, which agrees well with the analytical solutions of indoor contaminant concentration under the extreme operations.