Large-scale Environmental Remediation Research Articles

Microwave-Assisted Synthesis of Flower-like MnMoO4 Nanostructures and Their Photocatalytic Performance.

This article describes an affordable method for the synthesis of MnMoO4 nanoflowers through the microwave synthesis approach. By manipulating the reaction parameters like solvent, pH, microwave power, and irradiation duration along this pathway, various nanostructures can be acquired. The synthesized nanoflowers were analyzed by using a powder X-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and UV-vis diffuse reflectance spectroscopy (UV-DRS) to determine their crystalline nature, morphological and functional group, and optical properties, respectively. X-ray photoelectron spectroscopy (XPS) was performed for the examination of elemental composition and chemical states by qualitative and quantitative analysis. The results of the investigations demonstrated that the MnMoO4 nanostructures with good crystallinity and distinct shape were formed successfully. The synthesized MnMoO4 nanoflowers were tested for their efficiency as a photocatalyst in the degradation studies of methylene blue (MB) as model organic contaminants in an aqueous medium under visible light, which showed their photocatalytic activity with a degradation of 85%. Through the band position calculations using the electronegative value of MnMoO4, the photocatalytic mechanism of the nanostructures was proposed. The results indicated that the effective charge separation, and transfer mechanisms, in addition to the flower-like shape, were responsible for the photocatalytic performance. The stability of the recovered photocatalyst was examined through its recyclability in the degradation of MB. Leveraging MnMoO4's photocatalytic properties, future studies may focus on scaling up these processes for practical and large-scale environmental remediation.

One Step Synthesis of TiO2-Activated Carbon Composite Using Hydrothermal Method with Mass Variation of Activated Carbon

One effort to increase the photocatalytic activity of TiO2 is to immobilize it on the surface of the sorbent material. This study aims to produce TiO2-Activated Carbon (TiO2-AC) composites which have higher photocatalytic activity than TiO2, using a simple method. The synthesis of TiO2-AC composites was carried out using the hydrothermal method. The synthesis process was initiated by mixing TTIP, ethanol, H2O, and activated carbon with various masses (5 g, 10 g, 15 g, and 20 g). The mixture was then put into a hydrothermal autoclave and heated at 180°C for 12 hours. The material is then washed until the pH is neutral, and then dried. The TiO2-AC composite powder was then calcined at 500°C for 3 hours. Based on the photocatalytic test of the TiO2-AC composite on the degradation of methylene blue compounds, it was shown that composite with a mass variation of 10 g activated carbon (TiO2-AC/10) had the highest photocatalytic activity. FTIR characterization of the sample TiO2-AC/10 showed a shift in the peak wave number of the hydroxyl and carbon groups. Meanwhile, the results of morphological analysis using SEM showed that TiO2 particles had adhered to the AC surface, which was also confirmed by EDX data in the presence of Ti and O elements in the synthesized material. The results of the crystallinity analysis showed that the 100% synthesized TiO2 was the anatase phase with a crystalline size of 1.80−14.14 nm. This study open up opportunities for the development of TiO2-based composite materials for large-scale environmental remediation applications.

Bioremediation of Polycyclic Aromatic Hydrocarbons from Industry Contaminated Soil Using Indigenous Bacillus spp.

Polycyclic aromatic hydrocarbons (PAHs) are reportedly toxic, ubiquitous and organic compounds that can persist in the environment and are released largely due to the incomplete combustion of fossil fuel. There is a range of microorganisms that are capable of degrading low molecular weight PAHs, such as naphthalene; however, fewer were reported to degrade higher molecular weight PAHs. Bacillus spp. has shown to be effective in neutralizing polluted streams containing hydrocarbons. Following the growing regulatory requirement to meet the PAH specification upon disposal of contaminated soil, the following study aimed to identify potential Bacillus strains that could effectively remediate low and high molecular weight PAHs from the soil. Six potential hydrocarbon-degrading strains were formulated into two prototypes and tested for the ability to remove PAHs from industry-contaminated soil. Following the dosing of each respective soil system with prototypes 1 and 2, the samples were analyzed for PAH concentration over 11 weeks against an un-augmented control system. After 11 weeks, the control system indicated the presence of naphthalene (3.11 µg·kg−1), phenanthrene (24.47 µg·kg−1), fluoranthene (17.80 µg·kg−1) and pyrene (28.92 µg·kg−1), which illustrated the recalcitrant nature of aromatic hydrocarbons. The soil system dosed with prototype 2 was capable of completely degrading (100%) naphthalene, phenanthrene and pyrene over the experimental period. However, the accumulation of PAHs, namely phenanthrene, fluoranthene and pyrene, were observed using prototype 1. The results showed that prototype 2, consisting of a combination of Bacillus cereus and Bacillus subtilis strains, was more effective in the biodegradation of PAHs and intermediate products. Furthermore, the bio-augmented system dosed with prototype 2 showed an improvement in the overall degradation (10–50%) of PAHs, naphthalene, phenanthrene and pyrene, over the un-augmented control system. The following study demonstrates the potential of using Bacillus spp. in a bioremediation solution for sites contaminated with PAHs and informs the use of biological additives for large-scale environmental remediation.

Composition-engineered LaCoO3-based monolithic catalysts for easily operational and robust peroxymonosulfate activation

Herein, we report for the first time the construction of perovskite oxide catalysts on monolithic supports for peroxymonosulfate (PMS) activation to eliminate organic pollutants in wastewater. Specifically, the commercially available porous alumina ceramic (PAC) was utilized as monolithic support, on which Ca − Ti co-modified LaCoO3 perovskites (L1−xCxC1−yTyO3) were successfully loaded through a simple, controllable, and reagent-saving “dripping − calcination” process. The resulting monolithic catalysts (L1−xCxC1−yTyO3@PAC) featured large sizes (cm-scale), highly open porous architectures, and compositionally favorable active components, by which easy catalyst recycling, rapid mass transfer of guest species, and high yet stable catalytic performance were harvested in PMS activation for degradation of the typical antibiotic pollutant metronidazole (MNZ). By optimizing the introduction amount of Ca and Ti, the resulting L0.8C0.2C0.4T0.6O3@PAC showed a high turnover frequency (TOF) value of 12.6 min−1 for MNZ with a low cobalt leaching amount of 0.203 mg L−1, which were significantly superior to the unmodified catalyst LCO3@PAC (TOF: 7.9 min−1; cobalt leaching: 1.71 mg L−1). Roles of Ca and Ti modifiers in the LaCoO3-based monolithic catalyst, degradation pathway of MNZ, and SO4−•/1O2 dominated catalytic mechanism were investigated and elucidated. Our work provides a promising avenue for rational design of low-cost, easily operational, and robust monolithic catalysts toward PMS activation for large-scale environmental remediation.

Horseradish peroxidase immobilization by copolymerization into cross-linked polyacrylamide gel and its dye degradation and detoxification potential

Owing to the ever-increasing environmental and health impacts associated with the discharge of dye-based effluents, effective remediation of industrial waste have become a top priority for the industrialists and environmental fraternity, around the world. Plant-based peroxidases represent a suitable bio-remediating agent for the effective treatment of original dyes or dye-based colored wastewater effluents. In the present study, horseradish peroxidase was immobilized by copolymerization into cross-linked polyacrylamide gel and investigated its potential for the degradation and detoxification of an azo dye, methyl orange. In the presence of N, N′-methylenebisacrylamide as a cross-linker, polyacrylamide gel at 10% concentration furnished >80% of immobilization yield. The surface morphology of the control (free enzyme) and immobilized enzyme, i.e., horseradish peroxidase cross-linked polyacrylamide gel was characterized using scanning electron microscopy. The high yielded horseradish peroxidase cross-linked polyacrylamide gel concentration, i.e., 10% was used to develop a packed bed reactor and exploited for dye degradation and detoxification purposes. A noteworthy level (>90%) of dye degradation was recorded after polyacrylamide gel cross-linked horseradish peroxidase-catalyzed reaction in a packed bed bioreactor. The biodegradation was further assessed by Fourier-transform infrared spectral analysis. The acute toxicity assays demonstrated that enzyme-based bio-degradation might be used effectively for large-scale environmental remediation of dyes and dyes containing wastewater effluents.

Synthesis of ZnAlTi-LDO supported C60@AgCl nanoparticles and their photocatalytic activity for photo-degradation of Bisphenol A

ZnAlTi layered double oxide (ZnAlTi-LDO) supported C60@AgCl nanoparticles were synthesized by the coprecipitation-light-induced method and their photocatalytic activity for photo-degradation of Bisphenol A (BPA) was analyzed quantitatively by high performance liquid chromatography (HPLC). The morphology, structure and composition of the nanocomposites were analyzed by Scanning Electron Microscopy, Transmission electron microscopy, X-ray diffraction patterns, Fourier Transform Infrared spectra and Specific Surface Area. According to the analysis, ZnAlTi-LDO supported C60@AgCl nanoparticles (C60@AgCl-LDO) was characteristic of mesoporous materials. Pore size distribution plots of all the catalysts were well-distributed, ranging between 10 and 20nm. Because the heterostructure of Ag@AgCl enhanced near-field for light scattering, reflection and absorption. The Ag@AgCl-LDO nanoparticles and C60@AgCl-LDO nanoparticles showed a very intense absorption band in the near-UV region. The C60 was used as support materials to enhance the stability of Ag-based photocatalysts. The C60@AgCl can reduce the recombination of photo-induced electron–hole pairs and therefore increase the efficiency of the photocatalysis. The photo-degradation experiment was conducted by using a series of the nanoparticles to degrade BPA under simulated visible light irradiation. Test results show that, photogenerated holes, superoxide radical species, OHbulk and singlet oxygen are responsible for the photo-degradation, among which the superoxide radical species plays an indispensable role in the photocatalytic reaction system. The degradation rate of the C60@AgCl-LDO in photocatalytic degradation of BPA under simulated visible light irradiation is for 90%. The C60@AgCl-LDO nanoparticles with remarkable photocatalytic activity can be used for large-scale environmental remediation.

Horseradish peroxidase-assisted approach to decolorize and detoxify dye pollutants in a packed bed bioreactor

In this study, horseradish peroxidase (HRP) was covalently immobilized on the calcium-alginate support using glutaraldehyde (GA) as a cross-linking reagent for detoxification and degradation of synthetic dyes. Immobilization procedure furnished significant immobilization efficiency (86.27 ± 3.43%) along with apparent and relative activity of 24.39 ± 1.03 U/g and 84.97 ± 3.54%, respectively, for immobilized-HRP. In comparison to free-state, immobilized-HRP catalyzed the substrate oxidation reaction in a slightly acidic and wider temperature range, with an optimum at 60 °C. After 10 and 60 min of incubation at 60 °C, the immobilized-HRP displayed 99.0% and 89.0% of residual activities, whereas the free counterpart retained only 34.0% and 18.0% of residual activities, respectively. Moreover, the immobilized-HRP showed potential efficiency for the decolorization of dyes in sequential dye-decolorizing batch reactions. Cytotoxicity analysis using a plant bioassay and acute test demonstrated that the Ca-alginate immobilized-HRP may effectively be used for detoxification of dyes and has a great potential for large-scale environmental remediation.

Fe(0) Nanomotors in Ton Quantities (10(20) Units) for Environmental Remediation.

Despite demonstrating potential for environmental remediation and biomedical applications, the practical environmental applications of autonomous self-propelled micro-/nanorobots have been limited by the inability to fabricate these devices in large (kilograms/tons) quantities. In view of the demand for large-scale environmental remediation by micro-/nanomotors, which are easily synthesized and powered by nontoxic fuel, we have developed bubble-propelled Fe(0) Janus nanomotors by a facile thermally induced solid-state procedure and investigated their potential as decontamination agents of pollutants. These Fe(0) Janus nanomotors, stabilized by an ultrathin iron oxide shell, were fuelled by their decomposition in citric acid, leading to the asymmetric bubble propulsion. The degradation of azo-dyes was dramatically increased in the presence of moving self-propelled Fe(0) nanomotors, which acted as reducing agents. Such enhanced pollutant decomposition triggered by biocompatible Fe(0) (nanoscale zero-valent iron motors), which can be handled in the air and fabricated in ton quantities for low cost, will revolutionize the way that environmental remediation is carried out.

Seemingly unrelated intervention time series models for effectiveness evaluation of large scale environmental remediation

Large scale environmental remediation projects applied to sea water always involve large amount of capital investments. Rigorous effectiveness evaluations of such projects are, therefore, necessary and essential for policy review and future planning. This study aims at investigating effectiveness of environmental remediation using three different Seemingly Unrelated Regression (SUR) time series models with intervention effects, including Model (1) assuming no correlation within and across variables, Model (2) assuming no correlation across variable but allowing correlations within variable across different sites, and Model (3) allowing all possible correlations among variables (i.e., an unrestricted model). The results suggested that the unrestricted SUR model is the most reliable one, consistently having smallest variations of the estimated model parameters. We discussed our results with reference to marine water quality management in Hong Kong while bringing managerial issues into consideration.

Dam Removal in the Pacific Northwest: Lessons for the Nation

Over the past dozen years, a number of large dams in the Pacific Northwest have been removed in an effort to restore riverine ecosystems and dependent species like salmon. These dam removals provide perhaps the best example of large-scale environmental remediation in the 21st century. This restoration, however, has occurred on a case-by-case basis, without a comprehensive plan. Yet the result has been to put into motion ongoing rehabilitation efforts in four distinct river basins: the Elwah and White Salmon in Washington and the Sandy and Rogue in Oregon. In all, nine significant dams have been removed, and four more — in the contentious Klamath Basin of Oregon and California — are slated for removal in within the next decade. This article surveys both the successful and proposed removals in to draw lessons both within and beyond the Pacific Northwest. We identify a number of factors that determine both the speed and success of dam removal efforts, including the availability of the federal licensing process under the Federal Power Act, the existence and organization of local opposition, the amount and sources of funding, and the support of federal and state resource agencies and well-positioned members of Congress. These factors suggest that the promised removal of the Klamath Dams as well as calls for removing the federal dams on the Lower Snake face significant odds.

Solvent-free production of nanoscale zero-valent iron (nZVI) with precision milling

Despite its effectiveness in degrading a wide array of environmental contaminants and superior physical characteristics for subsurface delivery, large-scale applications of nanoscale zero-valent iron (nZVI) for environmental remediation have been inhibited by the high costs associated with its conventional production technologies. In this contribution, an environmentally-benign and cost-effective production method of nZVI is demonstrated using a precision milling system. Unlike conventional methods such as chemical synthesis and vapor phase condensation, which typically involve toxic chemicals, sophisticated equipment and extensive labor, the precision milling method relies solely on the mechanical impact forces generated by stainless steel beads in a high-speed rotary chamber to break down the micro iron particles. The system uses no toxic solvents, is completely scalable to large-scale manufacturing. Scanning electron microscope (SEM) and BET surface area analysis independently verify that, after 8 hours of milling, the feed micro iron was effectively reduced to particles with sizes below 50 nm. The surface chemistry and crystal composition of the milled iron were characterized with high-resolution X-ray photoelectron spectroscopy (HR-XPS) and X-ray diffraction (XRD). Reactivity of the milled nZVI was probed through reactions with water and seven model chlorinated aliphatic compounds. The results demonstrate the milled nZVI (8 hour) is more reactive for contaminant degradation than the nZVI synthesized by the widely-adopted borohydride reduction method. The ball milling method thus stands as a promising green process for large-scale nZVI production and enhances the prospect of the nZVI technology for large-scale environmental remediation.

Field-scale demonstration of the potential for sewage to remediate acidic mine waters

Pit lake waters are often contaminated by acid mine drainage (AMD) from weathering of pyritic materials exposed by mining operations, leading to low pH, and high solute and heavy metal concentrations. Few cost-effective engineering solutions exist for large-scale environmental remediation of AMD-contaminated pit lakes. However, various studies have demonstrated that biological remediation strategies for remediating AMD-contaminated waters, including microbially-mediated sulphate reduction, show promise at the laboratory-scale. The addition of acidic mine water to raw sewage and workshop wastewaters in an evaporation pond provided an opportunity for a field-scale experiment as essentially a reversal of suggested in-situ treatment of acidic pit lakes by addition of organic carbon. The hyper-eutrophic evaporation pond initially contained high concentrations of nutrients, a pH > 8, high levels of sulphate (500 mg L−1), and had regular algal blooms. Soon after the addition of the AMD pit water, the evaporation pond pH fell to 2.4, and electrical conductivity (EC) and most metal concentrations were elevated by one to two orders of magnitude. Over the following 18 months, the pH of the pond increased and the EC and metal concentrations decreased. After only 18 months of addition of AMD, pond water quality had returned to a level similar to that before AMD addition. These observations suggest that addition of low-grade organic materials shows promise for remediation of acid mine waters at field scale and warrants experimental investigation.

A Qualitative Risk Assessment of Farmland Heavy Metal Pollution in Taiwan

P-793 Introduction: We used a qualitative approach to explore the environmental health risk of heavy metal pollution in Chang-Hua County, Taiwan. We investigated how rice paddies were polluted by waste water from nearby electric plating factories, and traced the discovery of and the responses to environmental health problems by local residents, legislators, the mass media, the government and the scientific community. Methods: We used an ethnographic approach to study the case. Our methods included participant observations, in-depth interviews, policy analyses, media analyses, and content analyses of documents. Results: There were broad concerns from the mass media and the Legislative Yuan of Taiwan regarding the heavy metal pollution in farmlands. In 2003, large-scale environmental remediation projects were started in order to clean up the polluted farmlands. The environmental epidemiological studies of the health effects, however, were still in progress at the time. While local residents were concerned with the health effects of the pollution, they were also skeptical of the effectiveness of the remediation, and the reusability of their farmland. Discussion and Conclusions: Although quantitative data have not yet determined the existence of environmental health effects in this case, qualitative data are valuable in understanding how lay people experience and act on their environmental health problems. We suggest that qualitative methods be incorporated with quantitative environmental health risk assessment.

Catalytic oxidation of gaseous reduced sulfur compounds using coal fly ash

Activated carbon has been shown to oxidize reduced sulfur compounds, but in many cases it is too costly for large-scale environmental remediation applications. Alternatively, we theorized that coal fly ash, given its high metal content and the presence of carbon could act as an inexpensive catalytic oxidizer of reduced sulfur compounds for “odor” removal. Initial results indicate that coal fly ash can catalyze the oxidization of H 2S and ethanethiol, but not dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) at room temperature. In batch reactor systems, initial concentrations of 100–500 ppmv H 2S or ethanethiol were reduced to 0–2 ppmv within 1–2 and 6–8 min, respectively. This was contrary to control systems without ash in which concentrations remained constant. Diethyl disulfide was formed from ethanethiol substantiating the claim that catalytic oxidation occurred. The presence of water increased the rate of adsorption/reaction of both H 2S and ethanethiol for the room temperature reactions (23–25 °C). Additionally, in a continuous flow packed bed reactor, a gaseous stream containing an inlet H 2S concentration of 400–500 ppmv was reduced to 200 ppmv at a 4.6 s residence time. The removal efficiency remained at 50% for approximately 4.6 h or 3500 reactor volumes. These results demonstrate the potential of using coal fly ash in reactors for removal of H 2S and other reduced sulfur compounds.