Abstract

Introduction

Wastewater in area of focus

Nanotechnology in water purifcation

Nano‑adsorption

Microbial agent

Nanocomposites

Types of nanocomposites

Synthesis modes for nanocomposites

Graphene oxide‑based composites as a disinfectant

Zinc oxide nanocomposites as disinfectant

Copper oxide nanocomposites

Silver/silver oxide nanocomposites

Titanium oxide nanocomposites

Discussion

Conclusion

References

Abstract

     Water is crucial for the existence of life. The world, however, is facing a global water crisis. There are variety of microorganisms, gases and other toxins responsible for water contamination. Various types of nanomaterials exist that have enormous potential to treat contaminated water (water containing metal toxins or specific organic or inorganic impurities) due to their unique properties such as a high surface area and their ability to work effectively even at low concentrations. In recent years, scientists have been giving considerable attention to the application of nanocomposites for water purification, wastewater treatment, microorganism elimination, chemical contaminants, heavy metals removal and so forth. The incorporation of different nanofillers such as carbon nanotubes, graphene oxide, 2D materials, zinc oxide, titanium dioxide, copper and silver nanoparticles into polymeric materials has facilitated important advances, such as suppressing the accumulation of pollutants and foulants, improving the hydrophilicity, increasing the efficiency and improving the mechanical properties. This review discusses leading advances in the development of nanocomposites for antimicrobial and wastewater treatment with the aim of providing an improved understanding of nanocomposites and their applications in antimicrobial and wastewater treatment.

Introduction

     Water is a basic requirement for human life. However, we are far from meeting global requirements for clean water, and this issue will continue to grow over the time (Hillie and Hlophe 2007; Elwakeel et al. 2020b). The demand of clean drinking water is rising as a result of the deterioration of water quality, global climate change and population growth (Tchobanoglous et al. 1991; Elwakeel et al. 2020d). Emissions of organic dyes and heavy metal ions from the paper, leather and textile industries are a serious problem, as they are potentially mutagenic and carcinogenic. To meet environmental requirements, wastewater contaminated with these organic and inorganic species need to be treated before being discharged (Santhosh et al. 2016; Elwakeel et al. 2021). Heavy metals are widely used in various industries for many purposes, including mining and pigment production. Synthetic dyes are also an important type of pollutant, and their sources for water contamination include the textile, pulp and paper, tinting, printing, painting and tanning industries. The removal of dye from such wastewater is a challenging task, as pigments and synthetic dyes are biodegradation-resistant and remain in the environment for a long time. The destruction and handling of organic dyes is therefore an important issue, and a cost-efective method for removing dye substances from wastewater has been developed (Santhosh et al. 2016; Elwakeel et al. 2018).

Conclusion

     This paper explores the existing nanocomposites used to extract heavy metal ions and dyes from wastewater as efective adsorbents. This article addressed recent developments in nanomaterials as economical and environmentally sustainable water purifcation adsorbents. This review highlights fve commonly used nanomaterials/nanoparticles that are used in most existing nanocomposites. In this review, we concluded that TiO2-based nanocomposites have been used for photodegradation activity by most of the researchers in the literature. Silver-based nanocomposites are mostly used for antimicrobial activity. Silver and GO-based nanocomposites were used for the removal of green dye, anionic dye and Cu(II). Copper-based nanocomposites are mostly used for adsorption and photodegradation activity. Zinc oxide nanocomposites are used for adsorption, antimicrobial and photodegradation activity. Finally, we concluded that GO also greatly contributes to the improvement of other materials’ efciency. Further, much needs to be done to control the two-dimensional GO sheets for advanced technologies in the future. There are many challenges and obstacles associated with handling wastewater, and many precautions are required to prevent environmental and health problems. Therefore, new modern wastewater treatment equipment should be versatile, low-cost and commercially efective.

Abstract

1. Introduction

2. Methods and Materials

3. International Perspective on Air Pollution

4. General and Respiratory Disease Hospitalization and Mortality Rates

5. Children

6. Adults

7. COVID-19 Pandemic

8. Social Awareness of Air Pollution in Poland

9. Limitations and Future Perspectives

10. Conclusions

Abbreviations

References

Abstract

     According to the World Bank Group, 36 of the 50 most polluted cities in the European Union are in Poland. Thus, ambient air pollution and its detrimental health effects are a matter of immense importance in Poland. This narrative review aims to analyse current findings on air pollution and health in Poland, with a focus on respiratory diseases, including COVID-19, as well as the Poles’ awareness of air pollution. PubMed, Scopus and Google Scholar databases were searched. In total, results from 71 research papers were summarized qualitatively. In Poland, increased air pollution levels are linked to increased general and respiratory disease mortality rates, higher prevalence of respiratory diseases, including asthma, lung cancer and COVID-19 infections, reduced forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). The proximity of high traffic areas exacerbates respiratory health problems. People living in more polluted regions (south of Poland) and in the winter season have a higher level of air pollution awareness. There is an urgent need to reduce air pollution levels and increase public awareness of this threat. A larger number of multi-city studies are needed in Poland to consistently track the burden of diseases attributable to air pollution.

Introduction

     Ambient air pollution is one of the most significant environmental issues affecting health and wellbeing. It is linked to increased mortality from cardiovascular and respiratory diseases, including lung cancer and chronic obstructive pulmonary disease (COPD), shortening life expectancy [1]. It is estimated that in Europe in 2019, about 307,000 premature deaths were caused by chronic exposure to fine particulate matter with a diameter of 10 micrometres or smaller (PM10) and to coarse particulate matter with a diameter of 2.5 micrometres or smaller (PM2.5) [2]. In addition, about 40,000 premature deaths were attributed to chronic nitrogen dioxide (NO2) exposure [2].

     According to the World Bank Group, 36 of the 50 most polluted cities in the European Union are in Poland [3]. Moreover, Polish cities are among the urban areas with the highest estimated PM mortality burden [4]. Despite a consistent decrease in annual outdoor PM concentrations in the most polluted Polish cities in the recent decade, current values still do not meet the World Health Organisation (WHO) guidelines [5,6].

Conclusions

     In Poland, increased air pollution levels are linked to increased general and respiratory disease mortality and hospitalization rates as well as a higher prevalence of respiratory symptoms (wheezing, dyspnoea attacks, chronic cough) and respiratory diseases, including bronchitis, asthma, rhinitis, lung cancer and COVID-19 infections. Reduced FEV1 and FVC in spirometry tests are also observed. Infants, children, adolescents as well as adults are affected by worse air quality. Living in the proximity of high traffic areas exacerbates respiratory health problems.

     There is ample evidence that the course of asthma and bronchitis is exacerbated in areas with high ambient air pollution, while the indicators of subjective quality of life in asthmatic patients are lower. In atopic subjects, air pollution seems to sensitise the body and trigger an excessive response when combined with the usual allergen. There is also some evidence that higher concentrations of PM2.5, PM10, SO2, NO2 and ozone may facilitate the spread and infectiousness of SARS-CoV-2.

Highlights

Abstract

Graphical abstract

Keywords

1. Introduction

2. Methods used to conduct the mini-review

3. Composition of healthcare waste

4. Persistence rate of COVID-19 virus and its possible transmission through healthcare solid waste

5. Waste management strategies during the COVID-19 pandemic

6. Challenges

7. Potential for healthcare solid waste management strategies

8. Conclusions

Funding

Ethical approval

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgments

References

Abstract

Healthcare waste comprises the waste generated by healthcare facilities, medical laboratories and biomedical research facilities. Improper treatment of this waste poses serious risks of disease transmission to waste pickers, waste workers, health workers, patients, and the community in general through exposure to infectious agents. Poor management of the waste emits harmful and deleterious contaminants into society. However, contamination of highly contagious agents such as the COVID-19 virus has created enormous instability in healthcare waste handling and subsequent recycling because of the volume of the waste generated and its contagious nature. Several countries have adopted safety measures to combat this contamination and manage healthcare waste; however, these measures are insufficient and vary depending on the context of the country. In addition, the WHO has set out guidelines for management of healthcare waste. These guidelines are helping to manage the highly contagious healthcare waste resulting from the current pandemic. Proper healthcare waste management may add value by reducing the spread of the COVID-19 virus and increasing the recyclability of materials instead of sending them to landfill. Disinfecting and sorting out healthcare waste facilitates sustainable management and allows their utilization for valuable purposes. This review discusses the different healthcare solid waste management strategies practiced in different countries, the challenges faced during this management, and the possible solutions for overcoming these challenges. It also provides useful insights into healthcare solid waste management scenarios during the COVID-19 pandemic and a possible way forward.

1. Introduction

After radiation waste, healthcare waste is considered the second most hazardous waste globally. It includes various forms of waste, both hazardous and non-hazardous, such as sharps, human body parts, blood, chemical waste, pharmaceutical waste, and medical devices (Rodriguez-Morales, 2013). All of this waste is produced mainly by hospitals, primary care facilities, laboratories, mortuaries, autopsy centers, laboratories, blood banks, nursing homes, and other medical locations (Pepin et al., 2014). It is generated during diagnosis, treatment, immunization of humans or animals, research, or the production or testing of biologicals. If not properly handled, it can have devastating effects on human health (Johannessen et al., 2000). During any infectious disease outbreak, the waste generated from healthcare facilities increases exponentially; as a result, special care must be taken by management in order to avoid troubling impacts (Ramteke and Sahu, 2020).

The outbreak of coronavirus disease 2019 (COVID-19) has arisen from the SARS-CoV-2 virus, which causes an acute respiratory disease (Mol and Caldas, 2020; WHO, 2019; WHO, 2020b); it was first reported in Wuhan, China (Wang et al., 2020) in December 2019. It has been acknowledged as a Public Health Emergency of International Concern (PHEIC) (Wilder-Smith and Osman, 2020), and the virus has spread to almost all countries across the globe. The pandemic continues to be a significant public health threat worldwide. The rapid increase in the number of COVID-19 infected patients and the highly transmissible nature of the disease have led to a high number of hospitalizations.

Abbreviations

1. Introduction

2. Method and analysis section

3. Petrochemical wastewater pretreatment and advanced treatment

4. Future perspectives

Acknowledgements

Appendix A. Supplementary data

References

Abstract

Petrochemical wastewater is a major industrial source of pollution that produces a variety of refractory and toxic organic pollutants that are detrimental to animals and plants in natural water bodies; it is especially harmful to biological treatment systems. Regardless of these threats, studies on these specific organic pollutants are limited at present. Consequently, it is extremely essential to promote relevant problem solving efficiently. Currently, only limited processes are available for pretreatment of high-concentration wastewater, and advanced treatment of secondary effluent as compared to the conventional treatment are introduced by current studies. Therefore, in this review, we have systematically generalized the characteristics of petrochemical wastewater; we have particularly summarized and compared different methods (recent developments, influencing factors, etc.) which are applied in pretreatment and advancement of current methods. Additionally, the interaction mechanisms of microbes under a wide range of concentrations of specific organic pollutants and associated degradation pathways have been described comprehensively. Moreover, we have analyzed bioenergy recovery from the degradation/removal of specific organic pollutants with environmental-friendly and economically methods because it can help realize the goal of circular resource utilization during the process of detoxification and minimization.

Introduction

The petrochemical industry is a fundamental industry that plays an essential role 4 in any country’s national economy and provides support to many other sectors, such as agriculture, energy, transportation, etc. (Fig. 1) (Clews, 2016c; Jafarinejad 2017).  Petrochemical wastewater is generated via several routes from this industry, including effluent from raw materials, factory rainwater, cooling water, and domestic sewage. It has been reported that global petroleum production has reached 4.40 billion tons based on related industrial statistics (https://www.sohu.com/a/119515720_122917). Moreover, relevant studies have revealed that 3.00-3.50 m3 10 of petrochemical wastewater is generated per ton of petroleum refinery process (Zhang and Fan, 2016; 12 Siddique et al., 2017). For instance, China’s annual industrial wastewater discharge is 2.10 × 1010 13 t, of which the proportion of petrochemical wastewater was 3.00-5.00% in 14 2016. A report derived from China’s oil and chemical industry has shown that 2.00 15 billion tons of petrochemical wastewater were produced only in 2016, and the total 16 emission increased up to 4.00 billion during the 13th 5-year plan period (CMEP, 17 2015). Moreover, massive petrochemical wastewater was produced all over the world 18 during the same period that needed to be treated properly and urgently.

1- Introduction

2- Sources and characterization of agricultural wastewater

3- Struvite and its recovery performance from agricultural wastewaters

4- Commercial development of struvite products

5- Hindrances to struvite recovery from agricultural wastes

6- Strategies for performance intensification and operational cost reductions

7- Use of struvite as an alternative fertilizer in the soil

8- Economic evaluation

9- Conclusions

References

Abstract

To meet the needs of a fast growing global population, agriculture and livestock production have been intensified, resulting in environmental pollution, climate change, and soil health declining. Closing the nutrient circular loop is one of the most important sustainability factors that affect these issues. Apart from being a serious environmental issue, the discharge of N and P via agricultural wastewater is also a major factor that disturbs nutrient cycling in agriculture. In this study, the performance, in terms of recovery, of N and P (individually, as well as simultaneously) from agricultural wastewaters via struvite has been comparatively summarized. Details on the hindrances to nutrient recovery through struvite formation from agricultural effluents, along with strategies to overcome these hindrances, are provided. In addition, various strategies for recovery performance intensification and operational cost reduction are comprehensively discussed. This work will provide scientists and engineers with a better idea on how to solve the bottlenecks of this technique and integrate it successfully into their treatment systems, which will ultimately help close the nutrient loop in agriculture.

Introduction

The manifestations of rapid population growth, urbanization, improved standards of living, and concurrent intensification of socioeconomic activities on overall environmental health are well recognized and acknowledged (Cordell et al., 2009; Clarke, 2013). Global cereal production has doubled in the past 40 years, mainly from the increased yields resulting from greater inputs of fertilizer, water, pesticides, and so on. This has increased the global per capita food supply and alleviate hunger in poverty-stricken areas (Alexandratos and Bruinsma, 2012). During this process, however, the increase in nitrogenous fertilizer application and exhaustion of the limited reserves of rock phosphate have been quite considerable. At present, the annual fertilizer consumption of rock phosphate is reported to be over one million tons, while the use of N fertilizer could be three times as much (Rahman et al., 2011). Moreover, it is estimated that within 100 years, mined P rocks will be completely exhausted (Cordell and White, 2014”). Global cycling of these nutrients has been altered, owing to their widespread use in intensive agriculture, in ways that can contribute to severe environmental issues. Predominantly, nutrients can escape from farm fields to the surrounding soils, air, and waterways, when applied in excess of the plants’ needs (Deng et al., 2006). Hence, the notion of a closed-loop nutrient cycle provides a simple, persuasive, and elegant approach for realizing efficient natural resource management-improved human well-being, and long-term food security (Maurer et al., 2006). The closing of the nutrient loop includes a wide range of ongoing efforts to make sure that nutrients are applied at times and places that align with the requirements of the plants. It also includes efforts to recover nutrients in usable forms from waste effluents and recycle them into cropping systems (Yorgey, 2014). The logic is that by recovering nutrients from waste effluents, a more “closed” system for sustainable agricultural development can be created.

1- Introduction

2- Chemistry of geopolymers

3- Method and analysis section

4- Synthesis of geopolymers and mechanisms involved

5- Use of industrial waste as filler for the fabrication of crystalline metakaolin-based geopolymer

6- Result and discussion on applications driven by the surface chemistry of geopolymers in water

7- Barriers to utilization

8- Future research and prospects

9- Conclusion

References

Abstract

Geopolymer is a ceramic material, most often amorphous; finds applications in fire- and heat-resistant coatings and adhesives, medicines, refractory ceramics and binders, and manufacturing of radioactive waste container. Over the last decade, new cement based on geopolymers has been developed. Most relevant to this review is the fact that its porous nature and chemical similarity to zeolites is being employed for applications pertaining to wastewater treatment. Most of the work has been on the adsorptive treatment of water. However, using chemical reasoning and literature available we show that geopolymers have relevance for further activity on additional areas of relevance to waste water treatment such as photocatalysis, disinfection, and H2-energy production from waste water etc. These applications would depend strongly on the properties of geopolymers, which in turn would rely on the precursors employed and the synthetic methods used. The relevance of geopolymers for cleaner production is also highlighted. The use of fly ashes and metakaolin composites for the fabrication and surface tailoring of geopolymers (perhaps using relevant surfactants) is suggested as a plausible step in the right direction. Given the critical analysis of the state of the art, and the plausible directions identified, this article will benefit environmental scientists, engineers and chemists interested in deploying geopolymers for environmental remediation purposes. However moving forward, barriers are to be anticipated for the large scale implementation of geopolymers. Several barriers (e.g. legal, economical, technocrats and synthetic challenges) that are likely to hinder future research and translation are highlighted.

Introduction

Heavy metal removal and organic molecule degradation from wastewater have become a major topic of the public interest, due to their relevance to health and environment. Heavy metal and hazardous organic molecules are known to be toxic and a precursor to ill-health of the populace (Jaishankar et al., 2014). They are primarily released into the environment through human/industrial activities (Azimi et al., 2017). Hence research on multifunctional materials which relates to simultaneous environmental remediation and energy production are relevant to contemporary technologies connected with cleaner production. Geopolymers are a promising category of materials, for the removal of toxic substances from industrial and household effluents. It is usually prepared from a rather simple and eco-friendly reaction between an alkali such as NaOH/Na2SiO3 or KOH; and Al and Si source (s), making it a material amenable to clean production. Geopolymers obtained thus are often applied for the removal of metal ions such as Cs+ , Pb2+, Cd2+ etc. from wastewater. Geopolymers have come a long way, since their first discovery four decades ago (Davidovits, 1976). It has gained attention primarily because of the ease with which it can be synthesized with little or zero emission of green house gases (CO2. SO2, NOx etc.) (Noor ul et al., 2016). This coupled with its properties which include toughness, fire and heat resistance (i.e. its refractory nature), radiation hardness (making it relevant for radioactive waste containment) and pozzolanic action (Carsten, 2013), make geopolymers truly multifunctional.

1- Introduction

2- Water; one of the prerequisites for life as we know it

3- Isoscapes

4- Stable isotope ecology

5- Forensic isotope ecology

6- Caveats — a fishy example

7- Conclusions

8- The science bit: isotopologues, chemically identical yet not the same

References

Abstract

Stable isotope ecology and forensic isotope ecology are not only linked by name. More often than not, knowledge and insights gained through the former serve as a springboard for application focused work of the latter. This review aims to offer a glimpse into the fascinating world of both though with more emphasis on forensic isotope ecology. To this end a selection of past and recent published work is presented and discussed to highlight both potential and limitations of isotopic analytical approaches to the detection of illegal trade in plants and animals.

Introduction

Ecology, and its underpinning environmental studies, are two areas within natural and life sciences with a long history of applying stable isotope chemistry and bio-chemistry to gain insights into, for example, food webs, life cycles, or migration. It was only a matter of time before the methods that were developed, and the insights gained during ecological studies, were extended to wildlife forensics. For the appreciation of as wide an audience as possible, in addition to highlighting the wealth of information that stable isotope abundance signatures can provide, in Section 8 this review also provides some background information on the nature of stable isotopes, the terminology used, and why their relative abundance varies in the natural world. In-depth treatises on the subject of stable isotope chemistry in the context of ecological, geochemical, and forensic sciences, have been published in the form of several textbooks [1–5].

In sugarcane crops, several agricultural pesticides are applied simultaneously, and a set of these can be detected in groundwater and surface waters, characterizing a contamination by pesticides mixtures with different concentrations in these bodies of water. Thus, the aim of this work is to estimate the gray water footprint of the pesticide mixture (herbicides) used in a dystrophic Yellow Ultisol in a sugarcane cultivation system, in Pernambuco, Brazil, based on the toxicity of each pesticide used in the mixture. For this objective, the model proposed by Paraiba et al. (2014) was used, where the gray water footprint is determined by physicochemical characteristics of the soil and pesticides, the pesticide application rates (dose), and the lowest value of the effective mean dose of these substances in a population of organisms (EC50). The gray water footprint of the pesticide mixture was 1.32
105 m3 ha1 . The highest volumes of gray water and higher ranks of the mixture were due to Amicarbazone and Hexazinone, with 1.05
105 m3 ha1 (r ¼ 5) and 3.71
104 m3 ha1 (r ¼ 4.6), respectively, and the lowest values were due to Paraquat and Glyphosate, with gray water footprint of 1.64 and 8.43 m3 ha1 , respectively. The gray water footprint for the yield of the sugarcane crop was estimated at 1731.1 m3 t 1 , considered a high value for the gray water footprint of the sugarcane, demonstrating how much this crop can demands water resources to dilute its load of contaminants.

Introduction

There is currently a strong and unavoidable commitment to protecting water and its natural characteristics, as well as the fulfillment of human needs, such as: obtaining food in quantity and quality, fibers, fossil fuels, biofuels and biomass, industry, among others. Moreover, the global production of biological energy resources is expanding and accelerating the growth of agricultural production. As a consequence of these demands, water scarcity represents a major commercial and environmental concern worldwide (Popp et al., 2014). In the agricultural sector, the increased use of technology to produce food, fiber and fuel, for example, has contributed greatly to the productivity gains of agricultural crops (Brodt et al., 2011). However, the inappropriate use of these same technologies as, for example, pesticides, could jeopardize the developments observed in the Agricultural sector (Damalas and Eleftherohorinos, 2011). About the sugarcane culture, Brazil is the world’s largest sugarcane producer, being responsible together with India, for more than half of the production of this commodity on the world. Despite the relevance of the sugarcane crop and its economic results for Brazil in terms of trade balance and also GDP, it is necessary to take into account the environmental aspects resulting from the cultivation of this crop. Studies have shown that the sugarcane crop has negatively impacted the environmental compartments, as well as its biotic and abiotic components (Liboni and Cezarino, 2012; Pignati et al., 2017).

The main objective of this study is to analyze and compare greenhouse gas emission profiles, dynamics thereof, and the climate change mitigation efforts of the major players in the global climate change arena, namely the G7 and BRICS countries that are accounting for more than 60% of the world greenhouse gas emissions as in 2017. Given that the energy sector is the major source of the greenhouse emissions in these countries, the framework of sustainable energy development indicators was applied to the comparative analysis. The analysis revealed the differences among the groups of countries in terms of greenhouse gas emission profiles and development trends of these profiles. The convergence of greenhouse gas emission profiles can be noticed between G7 and BRICS countries during 1990e2017 period. Greenhouse gas emissions per capita has decreased in G7 countries and increased in BRICS countries. Energy intensity, economic growth and carbon factor are the main drivers of greenhouse gas emissions per capita growth in both groups of countries. Carbon factor represents carbon intensity of a country’s energy sector and is measured by greenhouse gas emissions per unit of total primary energy supply. The impact of carbon factor was least significant among the main drivers in both groups. Energy intensity was the major driver of decrease in greenhouse gas emissions per capita for both groups, however, the economic growth exceeded the contribution of energy intensity in BRICS countries and greenhouse gas emissions have increased in this group during investigated period. The comparative analysis of greenhouse gas emission profiles development trends and the main drivers of these trends in both groups of countries provides important insights in shaping future climate change mitigation policies and developing greenhouse gas emission reduction targets. Due to the high greenhouse gas profiles, low GHG reduction commitments and insufficient climate change mitigation the Perform, Achieve and Trade (PAT) scheme in India efforts in both groups there is danger of postponing implementation of Paris commitments and achieving the 1.5
target. The policies implemented in high ranked countries, like or Integrated Resources Planning in South Africa or measures under Energy efficiency directive in EU can be applied in low ranked countries by providing the substantial contribution to the country’s climate targets.

Introduction

The climate change has become an important global issue that is related to energy, economics, environment, and technology. Without taking further actions to reduce the global greenhouse gas (GHG) emissions, global warming is likely to exceed 2
C above the pre-industrialized levels. Such development would have a huge impact on the world’s landscape and sea levels and affect the economic and social development of countries all over the world. Accordingly, it is necessary to identify the paths for GHG emission management in the major emitting countries, which are subjected to the international commitments and national policies. The Group 7 (G7) and BRICS countries account for more than 60% of the world GHG emissions excluding Land Use, Land Use Change and Forestry (LULUCF) as in 2017. These countries present different GHG emission profiles and trends under the climate change mitigation agenda (Climate Transparency, 2018; Climate Action Tracker, 2018). The G7 is an international group of seven world leading developed countries (Canada, France, Germany, Italy, Japan, the United Kingdom, the United States). The G7 represents more than 60% of the global net wealth and almost 50% of the global GDP. The five leading emerging economies compose BRICS (Brazil, Russia, India, China, and South Africa). The G7 and BRICS countries (except Russia) have ratified the Paris Agreement, and Trump Administration’s intent to withdraw from the Paris Agreement creates many concerns in other G7 countries and all over the world. Therefore, the climate change policies and the associated decarbonization actions in those countries are particularly important within the transition towards the low-carbon economy.

1- Introduction

2- Microorganisms- the key players in bioremediation

3- Factors affecting heavy metal bioremediation

4- Role of enzymes in bioremediation

5- Phytoremediation

6- Immobilization techniques in bioremediation

7- Nanoparticles in bioremediation

8- Conclusion

References

Abstract

Pollution by heavy metals has been identified as a global threat since the inception of industrial revolution. Heavy metal contamination induces serious health and environmental hazards due to its toxic nature. Remediation of heavy metals by conventional methods is uneconomical and generates a large quantity of secondary wastes. On the other hand, biological agents such as plants, microorganisms etc. offer easy and eco-friendly ways for metal removal; hence, considered as efficient and alternative tools for metal removal. Bioremediation involves adsorption, reduction or removal of contaminants from the environment through biological resources (both microorganisms and plants). The heavy metal remediation properties of microorganisms stem from their self defense mechanisms such as enzyme secretion, cellular morphological changes etc. These defence mechanisms comprise the active involvement of microbial enzymes such as oxidoreductases, oxygenases etc, which influence the rates of bioremediation. Further, immobilization techniques are improving the practice at industrial scales. This article summarizes the various strategies inherent in the biological sorption and remediation of heavy metals.

Introduction

Recent years have evinced an unparalleled population growth and an accelerated pace of industrialization in line with it. Although, the quality of human life has substantially improved over the years, it is inevitable not to ignore that these developmental activities have taken place at the cost of the quality of our environment. During the last century, mining, electroplating, smelting, fertilizer, pesticides, tanneries, paper and electronic industries have accounted for the release of large amounts of heavy metals and petroleum hydrocarbons into the natural ecosystem, which has been reported to have disrupted the physiological functions in biological systems (Taiwo et al., 2016; Arivalagan et al., 2014). Environmental contamination can also occur through leaching of heavy metals, metal corrosion, atmospheric deposition, sediment resuspension to soil and ground water and metal evaporation from the water resources (Weerasundara et al., 2017; Francov
a et al., 2017). Hence, sediments constitute the major phase of contamination by metals in the aquatic systems (Nagajyoti et al., 2010). Among the pollutants, the hazardous heavy metals such as Arsenic (As), Cadmium (Cd), Lead (Pb), Copper (Cu), Chromium (Cr), Nickel (Ni), Zinc (Zn), Aluminum (Al) and Manganese (Mn) have known to be the major threats to the environment (Ullah et al., 2015; Dhanarani et al., 2016; Karthik et al., 2017a). These heavy metals impart serious health issues both to humans and ecosystems (Zeraatkar et al., 2016; Chen et al., 2015; Ullah et al., 2015). Source of various heavy metals are listed in Table 1. The heavy metal pollutants can enter into the environment through natural and anthropogenic ways and can be deposited in soils, water bodies or in the air (Kuppusamy et al., 2017; Chen et al., 2015).

Since the creation of first man-made plastic, the global production and consumption of plastics have been continuously increasing. However, because plastic materials are durable and very slow to degrade, they become waste with high staying power. The over consumption, disposal, and littering of plastics result in pollution, thus causing serious environmental consequences. To date, only a fraction of waste plastics is reused and recycled. In fact, recycling plastics remains a great challenge because of technical challenges and relatively insufficient profits, especially in mixed plastics. This review 19 focuses on an environmentally friendly and potentially profitable method for plastics separation and recovery and solvents extraction. It includes the dissolution/reprecipitation method and supercritical fluid extraction, which produce high-quality recovered plastics comparable to virgin materials. These methods are summarized and discussed taking mass-produced plastics (PS, PC, Polyolefins, PET, ABS, and PVC) as examples. To exploit the method, the quality and efficiency of solvent extraction are elaborated. By eliminating these technical challenges, the solvent extraction method is becoming more promising and sustainable for plastic issues and polymer markets.

Introduction

The challenge of the disposal of accumulated waste plastics and corresponding environmental issues have received widespread attention from the public and academicians (Rochman et al., 2013; Jambeck et al., 2015). Waste plastics can turn into the resources for new plastic products; thus, a cyclic economy can be achieved by coupling waste prevention with material recycling. For example, a sequential extraction process using mixed solvents to recover polycarbonates can obtain a high yield (>95%) and high purity similar to virgin polycarbonates recycled product using less energy (Weeden et al., 2015). Although green chemistry has grown remarkably (Cui et al., 2011), large amounts of waste plastics remain for safe disposal and reutilization. Recycling plastics can also be viewed as a big business because of its potential environmental benefits and economic profits. However, about 6300 million metric tons of plastic waste have been generated until 2015, and only 9% of them are recycled, 12% are incinerated, and 79% are discarded (Fig. 1) (Geyer et al., 2017). Taking the fastestgrowing component of the municipal solid waste stream as an example, electronic waste (e-waste, global generation 20–50 million tons/year (Robinson, 2009; Herat and 45 Agamuthu, 2012)) contains valuable plastics (~30%) (Gramatyka et al., 2007). In fact, ewaste plastics consist of heterogeneous polymers, which makes the recycling process difficult (Schlummer et al., 2006; Ignatyev et al., 2014), such as ABS, PC, SAN, PS 48 (Beigbeder et al., 2013), PP, and PET (Martinho et al., 2012).

Following the 2015 Paris Agreement, the main challenge for world economies nowadays is to commit themselves to long-term reforms aimed at increasing and promoting sustainable, inclusive and balanced development. An adequate response to this challenge will certainly require using the best available scientific knowledge and constant reevaluation of the development process in light of the scientific findings. To ensure that the sciences are responsive to the emerging needs and to address sustainable development issues. This Virtual Special Issue of the Journal of Cleaner Production is dedicated to both Sustainable Development of Energy, Water and Environment Systems 2016 Conferences – 2nd South East European Sustainable Development of Energy, Water and Environment Systems Conference and 11th Sustainable Development of Energy, Water and Environment Systems Conference. The Virtual Special Issue is focused on four main fields: Energy issues, Water issues, Environmental engineering and management, and Sustainable engineering solutions and large-scale sustainability approaches. The division of selected papers follows the previous Journal of Cleaner Production Special Sections and Volumes dedicated to the Sustainable Development of Energy, Water and Environment Systems Conference series.

Introduction

Sustainable development is a highly interdisciplinary concept that involves interaction of various systems. Integrating various systems, as energy, water, and environment, by using waste from one, as resource in other, and in exact moment when it is beneficial to all, is becoming a necessity for a sustainable, inclusive and balanced development (Mikulčić et al., 2017). To address this issue, at the beginning of this century the Sustainable Development of Energy, Water and Environment Systems (SDEWES) Conference series was established. In 2016, two SDEWES conferences were held. First time in July, it was the 2nd South East European SDEWES Conference (SDEWES SEE 2016) in Piran, Slovenia, and the second time in September, it was the 10th SDEWES Conference (SDEWES 2016) held in Lisbon, Portugal. Both conferences, SDEWES SEE 2016 with 195 participants and SDEWES 2016 with 324 participants, brought together researchers from around the world, to meet, share, and discuss their ideas and findings, in order to ensure that the sciences are responsive to emerging international, European, regional and national challenges. The papers in this Virtual Special Issue (VSI) are based on articles presented at both SDEWES Conferences in 2016. The two conferences covered various research topics, from the technical, economic, environmental and social studies, to the studies which investigated the sustainability of energy, transport, water, environment and food production systems and their interconnection and integration. From 475 accepted manuscripts, that were presented at both SDEWES Conferences 24 were selected for this Journal of Cleaner Production (JCLEPRO) VSI. As a results of a successful cooperation between the JCLEPRO and the SDEWES Conference series, this VSI is a sequel of previous SDEWES Conferences reports and reviews, and follows their format. The papers within the VSI SDEWES 2016 are divided into four research fields that have been established by the previous JCLEPRO Special Issues and Special Volumes dedicated to the SDEWES Conferences. These research fields are: Energy issues (8 papers); Water issues (4 papers); Environmental engineering and management (6 papers); Sustainable engineering solutions and large-scale sustainability approaches (4 papers). Hence, the previously generated SDEWES knowledge base in these four main research areas is extended by this JCLEPRO VSI.

Heavy metals and radionuclides in water are a global environmental issue, which has been receiving considerable attention worldwide. Water-stable MOFs are green and recyclable materials to eliminate the environmental impacts caused by the hazardous heavy metal ions and radionuclides in water. This paper presents a systematical review on the current status of waterstable MOFs that capture and convert a wide range of heavy metal ions (e.g., As(III)/As(V), Pb(II), Hg(II), Cd(II), and Cr(III)/Cr(VI)) and radionuclides (e.g., U(VI), Se(IV)/Se(VI) and Cs(I)) in aqueous solution. Water-stable MOFs and MOF-based composites exhibit the superior adsorption capability for these metal species in water. Significantly, MOFs show high selectivity in capturing target metal ions even in the presence of multiple water constituents. Mechanisms involved in capturing metal ions are described. MOFs also have excellent catalytic performance (photocatalysis and catalytic reduction by formic acid) for Cr(VI) conversion to Cr(III). Future research is suggested to provide insightful guidance to enhance the performance of the MOFs in capturing target pollutants in aquatic environment.

Introduction

In the past decades, contamination with heavy metals and organic pollutants has attracted increasing attention at a global scale due to their adverse health effects to human and aquatic organisms (Elzwayie et al., 2017; Fu et al., 2017; Schwarzenbach et al., 2010; Zou et al., 2016a; Ren et al., 2018a, 2018b, 2018c). Examples of the heavy metals include arsenic (As), lead (Pb), mercury (Hg), cadmium (Cd) and chromium (Cr), which have been found in concentrations ranging from ng/L to mg/L in surface water and industrial wastewater (Fu et al., 2017; Kim et al., 2013; Liu et al., 2017a; Singh et al., 2015; Smith and Steinmaus, 2009). Heavy metals have potential to induce acute and chronic toxicity (e.g., oxidative stress), developmental and reproductive toxicity, genotoxicity, and carcinogenicity on aquatic biota (Fu et al., 2017; Villaescusa and Bollinger, 2008; Wu et al., 2016a; Zhitkovich, 2011). Pb(II) released from pipe corrosion worldwide have recently apprehended serious concern (Abokifa and Biswas, 2017; Delile et al., 2016; Deshommes et al., 2016; Laidlaw et al., 2016; Masters et al., 2016; Pieper et al., 2017). Another great environmental concern emerges with the development of nuclear power, which produces and releases the radionuclides in natural waters (e.g., 235U, 79Se, 99Tc, 137Cs, and 90Sr) (Ding et al., 2016; Little et al., 2016; Sheng et al., 2017; Steinhauser, 2014). Hence, a variety of removal techniques have been investigated. These techniques include physical adsorption by different kinds of adsorbents (e.g., carbon-based materials and metal oxides) and membrane-based filtration as well as photocatalytic redox processes to efficiently recover these heavy metals and radionuclides from the water (Carboni et al., 2013; Ding et al., 2016; Fu and Wang, 2011; Howarth et al., 2015; Hua et al., 2012; Huang et al., 2014; Kim et al., 2013; Liu et al., 2017a; Ma et al., 2016; Singh et al., 2015; Vellingiri et al., 2018; Vilela et al., 2016; Yu et al., 2015; Zou et al., 2016a).