The textile industry consumes a large volume of organic dyes and water. These organic dyes, which remained in the effluents, are usually persistent and difficult to degrade by conventional wastewater treatment techniques. If the wastewater is not treated properly and is discharged into water system, it will cause environmental pollution and risk to living organisms. To mitigate these impacts, the photo-driven catalysis process using semiconductor materials emerges as a promising approach. The semiconductor photocatalysts are able to remove the organic effluent through their mineralization and decolorization abilities. Besides the commonly used titanium dioxide (TiO2), manganese dioxide (MnO2) is a potential photocatalyst for wastewater treatment. MnO2 has a narrow bandgap energy of 1~2 eV. Thus, it possesses high possibility to be driven by visible light and infrared light for dye degradation. This paper reviews the MnO2-based photocatalysts in various aspects, including its fundamental and photocatalytic mechanisms, recent progress in the synthesis of MnO2 nanostructures in particle forms and on supporting systems, and regeneration of photocatalysts for repeated use. In addition, the effect of various factors that could affect the photocatalytic performance of MnO2 nanostructures are discussed, followed by the future prospects of the development of this semiconductor photocatalysts towards commercialization.
Water pollution caused by the discharged insolubility petroleum contaminants and organic compound dyes seriously threatens the natural self-purity capacity of the water body and the survival of aquatic species, so it is imperative to restraint the deterioration of the aquatic environment. In this paper, pathways are propounded for the simultaneous removal of insoluble spilling oil and organic dye contaminants. Particularly, hydrophobic ZnSnO3 after stearic acid modification and Bi2MoO6 photocatalysts are introduced into the cotton fabric substrate through solution dip-coating. The durability of the prepared fabric suffers from the acid–base corrosion, thermal treatment and mechanical wear, while still exhibiting remarkable water-repellent (WCA?>?150°) property. Furthermore, the remarkable photocatalytic activity makes it possible for reusable degradation and the primary active species, namely the holes, to be verified by the radicals-capturing experiment. It is worth observing that as-prepared superhydrophobic fabric possesses admirable water-proof property and cycling durability of decomposing toxic water-soluble organic dye, thereby contributing to further realizing the ecological concept of clear waters.
Numerous contaminants in huge amounts are discharged to the environment from various anthropogenic activities. Waterbodies are one of the major receivers of these contaminants. The contaminated water can pose serious threats to humans and animals, by distrubing the ecosystem. In treating the contaminated water, adsorption processes have attained significant maturity due to lower cost, easy operation and environmental friendliness. The adsorption process uses various adsorbent materials and some of emerging adsorbent materials include carbon- and polymer-based magnetic nanocomposites. These hybrid magnetic nanocomposites have attained extensive applications in water treatment technologies due to their magnetic properties as well as combination of unique characteristics of organic and inorganic elements. Carbon- and polymer-related magnetic nanocomposites are more adapted materials for the removal of various kinds of contaminants from waterbodies. These nanocomposites can be produced via different approaches such as filling, pulse-laser irradiation, ball milling, and electro-spinning. This comprehensive review is compiled by reviewing published work of last the latest recent 3 years. The review article extensively focuses on different approaches for producing various carbon- and polymer-based magnetic nanocomposites, their merits and demerits and applications for sustainable water purification. More specifically, use of carbon- and polymer-based magnetic nanocomposites for removal of heavy metal ions and dyes is discussed in detail, critically analyzed and compared with other technologies. In addition, commercial viability in terms of regeneration of adsorbents is also reviewed. Furthermore, the future challenges and prospects in employing magnetic nanocomposites for contaminant removal from various water sources are presented.
Over the past decade, several studies have reported trace levels of endocrine disrupting compounds, pharmaceuticals, and personal care products in surface waters, drinking water, and wastewater effluents. There has also been an increased concern about the ecological and human health impact of these contaminants, and their removal from water and wastewater has become a priority. Traditional treatment processes are limited in their ability to remove emerging contaminants from water, and there is a need for new technologies that are effective and feasible. This paper presents a review on recent research results on molecularly imprinted (MIP) and non-imprinted (NIP) polymers and evaluates their potential as a treatment method for the removal of emerging contaminants from water and wastewater. It also discusses the relative benefits and limitations of using MIP or NIP for water and wastewater treatment. MIP, and in particular NIP, offer promising applications for wastewater treatment, but their toxicity and possible health effects should be carefully studied before they are considered for drinking water treatment. More research is also required to determine how best to incorporate MIP and NIP in treatment plants. 相似文献
The demand for high-quality safe and clean water supply has revolutionized water treatment technologies and become a most focused subject of environmental science. Water contamination generally marks the presence of numerous toxic and harmful substances. These contaminants such as heavy metals, organic and inorganic pollutants, oil wastes, and chemical dyes are discharged from various industrial effluents and domestic wastes. Among several water treatment technologies, the utilization of silica nanostructures has received considerable attention due to their stability, sustainability, and cost-effective properties. As such, this review outlines the latest innovative approaches for synthesis and application of silica nanostructures in water treatment, apart from exploring the gaps that limit their large-scale industrial application. In addition, future challenges for improved water remediation and water quality technologies are keenly discussed.
Various human activities like mining and extraction of mineral oils have been used for the modernization of society and well-beings. However, the by-products such as petrochemical wastes generated from such industries are carcinogenic and toxic, which had increased environmental pollution and risks to human health several folds. Various methods such as physical, chemical and biological methods have been used to degrade these pollutants from wastewater. Advance oxidation processes (AOPs) are evolving techniques for efficient sequestration of chemically stable and less biodegradable organic pollutants. In the present review, photocatalytic degradation of petrochemical wastes containing monoaromatic and poly-aromatic hydrocarbons has been studied using various heterogeneous photocatalysts (such as TiO2, ZnO and CdS. The present article seeks to offer a scientific and technical overview of the current trend in the use of the photocatalyst for remediation and degradation of petrochemical waste depending upon the recent advances in photodegradation of petrochemical research using bibliometric analysis. We further outlined the effect of various heterogeneous catalysts and their ecotoxicity, various degradation pathways of petrochemical wastes, the key regulatory parameters and the reactors used. A critical analysis of the available literature revealed that TiO2 is widely reported in the degradation processes along with other semiconductors/nanomaterials in visible and UV light irradiation. Further, various degradation studies have been carried out at laboratory scale in the presence of UV light. However, further elaborative research is needed for successful application of the laboratory scale techniques to pilot-scale operation and to develop environmental friendly catalysts which support the sustainable treatment technology with the “zero concept” of industrial wastewater. Nevertheless, there is a need to develop more effective methods which consume less energy and are more efficient in pilot scale for the demineralization of pollutant. 相似文献
Water scarcity is being recognized as a present and future threat to human activity and as a consequence water purification technologies are gaining major attention worldwide. Nanotechnology has many successful applications in different fields but recently its application for water and wastewater treatment has emerged as a fast-developing, promising area. This review highlights the recent advances on the development of nanoscale materials and processes for treatment of surface water, groundwater and industrial wastewater that are contaminated by toxic metals, organic and inorganic compounds, bacteria and viruses. In addition, the toxic potential of engineered nanomaterials for human health and the environment will also be discussed. 相似文献
Organic dyes are one of the most commonly discharged pollutants in wastewaters; however, many conventional treatment methods cannot treat them effectively. Over the past few decades, we have witnessed rapid development of nanotechnologies, which offered new opportunities for developing innovative methods to treat dye-contaminated wastewater with low price and high efficiency. The large surface area, modified surface properties, unique electron conduction properties, etc. offer nanomaterials with excellent performances in dye-contaminated wastewater treatment. For examples, the agar-modified monometallic/bimetallic nanoparticles have the maximum methylene blue adsorption capacity of 875.0 mg/g, which are several times higher than conventional adsorbents. Among various nanomaterials, the carbonaceous nanomaterials, nano-sized TiO2, and graphitic carbon nitride (g-C3N4) are considered as the most promising nanomaterials for removing dyes from water phase. However, some challenges, such as high cost and poor separation performance, still limit their engineering application. This article reviewed the recent advances in the nanomaterials used for dye removal via adsorption, photocatalytic degradation, and biological treatment. The modification methods for improving the effectiveness of nanomaterials are highlighted. Finally, the current knowledge gaps of developing nanomaterials on the environmental application were discussed, and the possible further research direction is proposed. 相似文献
Biologically based wastewater treatment systems are considered a sustainable, cost-effective alternative to conventional wastewater treatment systems. These systems have been used and studied for the treatment of urban sewage from small communities, and recently, it has been reported that they can also effectively remove emerging organic contaminants (EOCs). EOCs are a new group of unregulated contaminants which include pharmaceutical and personal care products, some pesticides, veterinary products, and industrial compounds among others that are thought to have long-term adverse effects on human health and ecosystems. This review is focused on reporting the ability of biologically based wastewater treatment systems to remove EOCs and the main elimination mechanisms and degradation processes (i.e., biodegradation, photodegradation, phytoremediation, and sorption) taking place in constructed wetlands, ponds, and Daphnia and fungal reactors. 相似文献
Electrocoagulation (EC) is an excellent and promising technology in wastewater treatment, as it combines the benefits of coagulation, flotation, and electrochemistry. During the last decade, extensive researches have focused on removal of emerging contaminants by using electrocoagualtion, due to its several advantages like compactness, cost-effectiveness, efficiency, low sludge production, and eco-friendness. Emerging contaminants (ECs) are micropollutants found in trace amounts that discharging into conventional wastewater treatment (WWT) plants entering surface waters and imposing a high threat to human and aquatic life. Various studies reveal that about 90% of emerging contaminants are disposed unscientifically into water bodies, creating problems to public health and environment. The studies on removal of emerging contaminants from wastewater are by global researchers are critically reviewed. The core findings proved that still more research required into optimization of parameters, system design, and economic feasibility to explore the potential of EC combined systems. This review has introduced an innovative collection of current knowledge on electro-coagulation for the removal of emerging contaminants.
The current study was designed to investigate the potential human health risks associated with consumption of food crops contaminated with toxic heavy metals. Cadmium (Cd) concentration in surface soils; Cd, lead (Pb) and chromium (Cr) in the irrigation water and food crops were above permissible limits. The accumulation factor (AF) was >1 for manganese (Mn) and Pb in different food crops. The Health Risk Index (HRI) was >1 for Pb in all food crops irrigated with wastewater and tube well water. HRI >1 was also recorded for Cd in all selected vegetables; and for Mn in Spinacia oleracea irrigated with wastewater. All wastewater irrigated samples (soil and food crops) exhibited high relative contamination level as compared to samples irrigated with tube well water. Our results emphasized the need for pretreatment of wastewater and routine monitoring in order to avoid contamination of food crops from the wastewater irrigation system. 相似文献
Although epidemiological studies have found a significant amount of toxins in surface water, a complex link between animals’ access to wastewater and associated animal and human welfare losses needs to be explored. The scarcity of safe water has put stress on the utilization of wastewater for crops and livestock production. The access of animals to wastewater is related to the emergence of dangerous animal’s diseases, hampering productivity, increasing economic losses, and risking human health along the food chain. This review explores use of wastewater for agriculture, epidemiological evidence of microbial contamination in wastewater, and animal and human welfare disruption due to the use of wastewater for crop and livestock production. More specifically, the review delves into animals exposure to wastewater for bathing, drinking, or grazing on a pasture irrigated with contaminated water and related animal and human welfare losses. We included some scientific articles and reviews published from 1970 to 2017 to support our rational discussions. The selected articles dealt exclusively with animals direct access to wastewater via bathing and indirect access via grazing on pasture irrigated with contaminated wastewater and their implication for animal and human welfare losses. The study also identified that some policy options such as wastewater treatments, constructing wastewater stabilization ponds, controlling animal access to wastewater, and dissemination of necessary information to ultimate consumers related to the source of agricultural produce and wastewater use in animal and crop production are required to protect the human and animal health and welfare. 相似文献
Background, Aim and Scope
The polynitramines, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX),
are important military explosives and regulated toxic hazardous compounds. Production, testing and use of the compounds has
resulted in numerous acres of contaminated soils and groundwater near many munitions facilities. Economical and efficient
methods for treatment of wastewater and cleanup of soils or groundwater containing RDX and HMX are needed. This study focuses
on the photocatalytic treatment of RDX wastewater with nano-sized titanium dioxide (nano-TiO2) under simulated sunlight, whose
intensity and wavelength are similar to that of the real sunlight in Xi'an at noon. The objective is to determine the potential
for RDX destruction with nano-TiO2 in aqueous solution.
Materials and Methods:
An activated carbon fiber (ACF) cloth-loaded with nano-TiO2 was put into the RDX containing solution, and the concentration
of RDX was measured (by HPLC–UV) at regular time intervals under simulated sunlight.
Results:
The RDX degradation percentage of the photocatalytic process is higher than that of Fenton oxidation before 80 min, equivalent
after 80 min, and it reaches 95% or above after 120 min. The nano-TiO2 catalyst can be used repeatedly.
Discussion:
The photocatalytic degradation kinetics of RDX under simulated sunlight can be described by a first-order reaction kinetics
equation. The possible degradation mechanism of RDX was presented and the degradation performance was compared with that of
biological method.
Conclusions:
It was demonstrated that the degradation of RDX wastewater is very effective with nano-TiO2 as the photocatalytic catalyst
under simulated sunlight. The efficiency of the nano-TiO2 catalyst for RDX degradation under simulated sunlight is nearly
identical to that of Fenton oxidation.
Recommendations and Perspectives:
To date, a number of catalysts show poor absorption and utilization of sunlight, and still need ultraviolet light irradiation
during wastewater degradation. The nano-TiO2 used in the described experiments features very good degradation of RDX under
simulated sunlight, and the manufacturing costs are rather low (around 10 Euro/m2). Moreover, the degradation efficiency is
higher compared to that of the biological method.
This method exhibits great potential for practical applications owing to its easiness and low cost. If it can be applied extensively,
the efficiency of wastewater treatment will be enhanced greatly. 相似文献
Photocatalytic technology has been widely studied by researchers in the field of environmental purification. This technology can not only completely convert organic pollutants into small molecules of CO2 and H2O through redox reactions but also remove metal ions and other inorganic substances from water. This article reviews the research progress of graphene-based photocatalytic nanocomposites in the treatment of wastewater. First, we elucidate the basic principles of photocatalysis, the types of graphene-based nanocomposites, and the role of graphene in photocatalysis (e.g., graphene can accelerate the separation of photon-hole pairs and increase the intensity and range of light absorption). Second, the preparation, characterization, and application of composites in wastewater are introduced. We also discuss the kinetic model of the photocatalytic degradation of pollutants. Finally, the enhancement mechanism of graphene in terms of photocatalysis is not completely clear, and graphene-based photocatalysts with high catalytic efficiency, low cost, and large-scale production have not yet appeared, so there is an urgent need for more extensive and in-depth research.
ABSTRACT The overall objective of this pilot-scale study is to investigate the technical feasibility of the removal and destruction of organic contaminants in water using adsorption and photocatalytic oxidation. The process consists of two consecutive operational steps: (1) removal of organic contaminants using fixed-bed adsorption; and (2) regeneration of spent adsorbent using photocatalysis or steam, followed by decontamination of steam condensate using photocatalysis. The pilot-scale study was conducted to evaluate these options at a water treatment plant in Wausau (Wisconsin) for treatment of groundwater contaminated with tetrachloroethene (PCE), trichloroethene (TCE), cis-dichloroethene (cis-DCE), toluene, ethylbenzene (EB), and xylenes. The adsorbents used were F-400 GAC and Ambersorb 563. In the first treatment strategy, the adsorbents were impregnated with photocatalyst and used for the removal of aqueous organics. The spent adsorbents were then exposed to ultraviolet light to achieve photocatalytic regeneration. Regeneration of adsorbents using photocatalysis was observed to be not effective, probably because the impregnated photocatalyst was fouled by background organic matter present in the groundwater matrix. In the second treatment strategy, the spent adsorbents were regenerated using steam, followed by cleanup of steam condensate using photocatalysis. Four cycles of adsorption and three cycles of steam regeneration were performed. Ambersorb 563 adsorbent was successfully regenerated using saturated steam at 160 °C within 20 hours. The steam condensate was treated using fixed-bed photo-catalysis using 1% Pt-TiO2 photocatalyst supported on silica gel. After 35 minutes of empty bed contact time, more than 95% removal of TCE, cis-DCE, toluene, EB, and xylenes was achieved, and more than 75% removal of PCE was observed. In the case of activated carbon adsorbent, steam regeneration was not effective, and a significant loss in adsorbent capacity was observed. 相似文献
Goal, Scope and Background Sewage sludge produced in wastewater treatment contains large amounts of organic matter and nutrients and could, therefore,
be suitable as fertiliser. However, with the sludge, besides heavy metals and pathogenic bacteria, a variety of organic contaminants
can be added to agricultural fields. Whether the organic contaminants from the sludge can have adverse effects on human health
and wildlife if these compounds enter the food chain or groundwater still remains a point of controversial discussion.
Main Features This paper presents an overview on the present situation in Europe and a summary of some recent results on the possible uptake
of organic contaminants by crops after addition to agricultural fields by sewage sludge.
Results Greenhouse experiments and field trials were performed to study the degradation and uptake of organic micro-contaminants in
sludge-amended agricultural soil in crops, such as barley and carrots grown in agricultural soil amended with anaerobically-treated
sewage sludge from a wastewater treatment plant, but studies hitherto have revealed no immediate risks. Common sludge contaminants
such as linear alkylbenzene sulphonates (LAS), nonylphenol ethoxylates (NPE), polycyclic aromatic hydrocarbons (PAH), bis(diethylhexyl)
phthalate (DEHP), showed neither accumulation in soil nor uptake in plants.
Discussion It is assumed that the annual amount of sewage sludge produced in Europe will increase in the future, mainly due to larger
amounts of high quality drinking water needed by an increasing population and due to increasing demands for cleaner sewage
water. Application of sewage sludge to agricultural soils is sustainable and economical due to nutrient cycling and disposal
of sewage sludge. However, this solution also involves risks with respect to the occurrence of organic contaminants and other
potentially harmful contents such as pathogens and heavy metals present in the sludge. There have been concerns that organic
contaminants may accumulate in the soil, be taken up by plants and thereby transferred to humans via the food chain. Results
obtained so far revealed, however, no immediate risk of accumulation of common organic sludge contaminants in soil or uptake
in plants when applying sewage sludge to agricultural soil. With very high dosages of sewage sludge, there may be a risk for
accumulation of very apolar contaminants, such as DEHP, to the soil.
Conclusions Any conclusions on the safe use of sewage sludge in agriculture have to be drawn carefully, as the studies performed until
now have been limited. Further studies are required, and before final statements can be drawn, it is imminent to study a larger
variety of common crops and the effect sewage sludge application may have on a possible accumulation of organic contaminants
in the crops. Furthermore, a larger variety of organic contaminants need to be studied and special focus should be given to
contaminants newly introduced into the environment. Besides investigating possible plant uptake of organic contaminants, the
fate of these compounds in soil after sludge application need to be monitored too. Here, special attention has to begiven
to studies on degradation and the formation of degradation products, to weathering and to leaching effects on groundwater,
to the application of different crops on the same field (crop rotation), to the use of full-width tillage and strip tillage,
and to long term application of sewage sludge on the soil.
Recommendations and Perspectives There are environmental, political as well as economical incentives to increase the agricultural application of sludge. However,
such usage should be performed with care as there are also ways in which sludge fertilisation could harm the environment and
human health. Recently, a new European COST Action (859) has been established covering the field of food safety and improved
food quality. Part of the Action is dealing with the application of sewage sludge in agriculture. Before any political and
economical measures can be taken, the pros and cons have to be sufficiently investigated on a scientific level first.
ESS-Submission Editor: Prof. Elena Maestri (elena.maestri@unipr.it) 相似文献
Polyaromatic hydrocarbons (PAHs) are widely spread ecological contaminants. Antibiotic resistance genes (ARGs) are present with mobile genetic elements (MGE) in the bacteria. There are molecular evidences that PAHs may induce the development of ARGs in contaminated soils. Also, the abundance of ARGs related to tetracycline, sulfonamides, aminoglycosides, ampicillin, and fluoroquinolones is high in PAH-contaminated environments. Genes encoding the efflux pump are located in the MGE and, along with class 1 integrons, have a significant role as a connecting link between PAH contamination and enrichment of ARGs. The horizontal gene transfer mechanisms further make this interaction more dynamic. Therefore, necessary steps to control ARGs into the environment and risk management plan of PAHs should be enforced. In this review, influence of PAH on evolution of ARGs in the contaminated soil, and its spread in the environment, has been described. The co-occurrence of antibiotic resistance and PAH degradation abilities in bacterial isolates has raised the concerns. Also, presence of ARGs in the microbiome of PAH-contaminated soil has been discussed as environmental hotspots for ARG spread. In addition to this, the possible links of molecular interactions between ARGs and PAHs, and their effect on environmental health has been explored.
