Keywords

3.1 Introduction

Human exercises in the last few years have caused extreme concern related to the environment and its preservation. Water shortage, water contamination, air contamination, soil debasement, poor administration of waste, loss of biodiversity are some of the ecological concerns that have caused permanent health impacts on humans as well as on animals and plants. Also, the advancement in industrialization, just as science and innovation, has prompted the enhancement of waste and lethal materials in the environment. Thus, the degradation and diminution of natural resources must be circumvented to achieve a sustainable environment. The conventional physicochemical strategies utilized for the reclamation of the common habitat were seen as improper because of cost, lower productivity and nonspecificity. Consequently, to overcome these constraints, biological methods were amalgamated with the nanotechnology-based physiochemical techniques for the removal of pollutants from the environment (Guerra et al. 2018). The present chapter reviews the existing physical, chemical and biological methods for the treatment of pollutants along with their merits, demerits and the application of nanotechnology in the bioremediation of contaminants. Furthermore, the chapter will likewise concentrate on the biological synthesis of the nanoparticles using microbes which will provide insight into nanobioremediation for removing contaminants from the environment. This nanobioremediation approach for the expulsion of toxicants from nature will be the most dependable and suitable technology as for the cost and effectiveness relative to the financial status of the developing countries.

3.2 Present Day Treatment Methods for the Ouster of Pollutants

Since the contaminants are lethal in nature, they have been contemplated dangerous to the environment. The treatment of these toxins in an environmentally safe way is obligatory before they are being released into the environment. The physical, chemical and biological techniques are the current treatment methods used for the expulsion of contaminants from the environment. Physical techniques incorporate methods like adsorption, reverse osmosis, electrodialysis, etc. Countless toxins are being discharged into the environment, out of which some are exceptionally hard to be treated by regular physical techniques. To solve the limitations of physical techniques, some of the chemical methods like precipitation, ion exchange, electroflotation, coagulation, flocculation, reduction and so forth were utilized for the expulsion of contaminants from the environment. In spite of the fact that the chemical methods used are productive, quick and can remove a wide range of toxins present in nature, their utilization is constrained by the significant price and sludge disposal issues. Furthermore, plenty of chemicals and high level of energy are required by these chemical methods. Considering all the above constraints, biological methods including the utilization of microorganisms (bioremediation) were utilized for the expulsion of lethal contaminants present in the environment (Ojuederie et al. 2017; Sinha et al. 2016; Behl et al. 2019). The process of bioremediation is economically attractive as well as environmentally friendly. Also, there is an advantage of minimum sludge generation, regeneration of biosorbent and possibility of metal recovery. However, the processes are slow, additional nutrition and maintenance are required. Moreover, the pollutants sometimes become toxic to the microorganisms involved in the process. Thus, every above mentioned techniques have their own benefits and disadvantages which make them insufficient to manage the issue of contaminant expulsion from nature.

3.3 Nanotechnology

The remediation of the toxicants by the existing traditional physicochemical methods and biological methods was not very efficient and effective in cleaning up the environment. Therefore, a new technology named ‘nanotechnology’ can be applied for the bioremediation of contaminants from the environment. Nanotechnology is derived from the Greek word ‘dwarf’ (El Saliby et al. 2008) and can be defined as the science of micro-engineering. Micro-engineering is the technique that deals with particles smaller than 100 nm. Nanotechnology was first proposed by Richard Feynman (1960), which now has become one of the fastest developing areas of research and development all around (Yadav et al. 2017). Presently, the field of nanotechnology is regarded as the ‘Next Industrial Revolution’ as in the future it will lessen the industrial costs by diminishing the consumption of energy, environmental pollution and enhancing the production efficiencies in developed countries (Roco 2005). Moreover, nanotechnology may also prove helpful in handling particular social issues of developing nations like the necessity of clean water and treatment of epidemic diseases (Fleischer and Grunwald 2008; Schmidt 2007). Nanotechnology offers a large amount of environmental benefits in remediation, pollution prevention and contributes a lot to developing smaller, more accurate sensing and monitoring devices (Savage et al. 2008). The ability of nanotechnology to abridge contamination is in progress that can result in extensive and profound changes in pollution control (Watlington 2005). Table 3.1 lists some of the common nanomaterials utilized in the remediation process.

Table 3.1 Various nanomaterials used in remediation process
Full size table

3.3.1 Properties of Nanoparticles

The essential part of nanotechnology is the very small particles called nanoparticles or ultrafine particles. Nanoparticles are particles somewhere in the range of 1–100 nm in size that can intensely change their physicochemical properties when contrasted with the bulk material. These particles are comprised of carbon, metal, metal oxides or organic matter and their function relies upon the type of synthesis, size and shape of the particles. They can be round, tubular, cylindrical and so on. Their surface can be uniform or irregular, while some are crystalline to amorphous with single or multi-crystal solids either free or agglomerated.

The nanoparticles are classified into organic, inorganic and carbon based. Organic nanoparticles incorporate dendrimers, liposomes, ferritin and so forth that are non-toxic, biodegradable and are likewise sensitive to thermal and electromagnetic radiation like heat and light, making them ideal for drug delivery (Tiwari et al. 2008). Inorganic nanoparticles are not comprised of carbon. They largely involve metal and metal oxide nanoparticles such as aluminium, copper, gold, iron, iron oxide, aluminium oxide, magnetite, etc. (Dreaden 2012). Carbon-based nanoparticles are totally comprised of carbon like graphene, fullerenes, carbon nanotubes (Saeed and Khan 2016).

The unusual chemical, physical, optical, thermal and electrical properties (Panigrahi et al. 2004) of nanoparticles can be used in various fields like drug delivery (Horcajada et al. 2008), medical imaging (Lee et al. 2008), optical receptors (Dahan et al. 2003), biolabelling (Liang et al. 2006), antimicrobial agents (Sanpui et al. 2008). There are other remarkable properties of nanoparticles like its small size which can cause increase in the surface area per unit mass that makes them profoundly helpful in bioremediation. Because of the small size, a lot of nanoparticles can come into contact with the surrounding medium, consequently influencing its reactivity. Nanoparticles show a remarkable property of surface plasmon resonance which helps in the detection of contaminants present in nature. Furthermore unique properties of nanoparticles likewise make them appropriate for the advancement of electrochemical sensors as well as biosensor (Peng and Miller 2011; Selid et al. 2009). Moreover, scientists have created nanosensors for the recognition of auxin and oxygen dissemination in plants (Koren et al. 2015). Because of the outstanding properties of nanoparticles, they have been proposed as a proficient, economical and environment friendly substitute to the present treatment advancements, in resource preservation as well as in ecological remediation (Friedrich et al. 1998; Dastjerdi and Montazer 2010). The ability of nanomaterials to abate pollution production is in progress and could potentially catalyse the most revolutionary changes in the environmental field in the coming decades (Fig. 3.1).

Fig. 3.1
figure 1

Applications of nanomaterials in bioremediation

Full size image

3.4 Synthesis of Nanoparticles

Nanoparticles can be synthesized by various strategies and approaches that incorporate physical, chemical and biological methods (Fig. 3.2) (Luechinger et al. 2010; Mohanpuria et al. 2008). Conventionally, the nanoparticles were produced by physicochemical strategies that enable them to be synthesized in enormous amounts with definite shape and size in a constrained timeframe; howbeit, these methods are expensive, wasteful, complicated, utilize hazardous chemicals, require high energy and produce toxic by-products that are hazardous to the environment (Li et al. 2011a, b; Rodriguez-Sanchez et al. 2000).

Fig. 3.2
figure 2

Different methods and approaches for synthesizing nanoparticles. Source: (Siavash 2011)

Full size image

Lately, the interest has been focussed on the production of economical and eco-friendly nanoparticles that do not give rise to dangerous and toxic by-products during the manufacturing procedure (Chauhan et al. 2012; Li et al. 2011a, b). Thus, recently, nanoparticles are being produced by biological methods that include microorganisms, plants and their by-products with the assistance of some biological tools. Biologically synthesized nanoparticles have striking and outstanding benefits over physical and chemical strategies like the production approaches are economical, quick and eco-friendly. In addition, the nanoparticles produced by biological path does not require any further stabilizing agents, as microorganisms and plants themselves act as stabilizing agents (Makarov et al. 2014). The biological synthesis of nanoparticles is a bottom-up approach where reducing and stabilizing agents help in synthesizing the nanoparticles (Fig. 3.2). Bio-fabrication of nanoparticles is in general achieved either through reduction or oxidation process. The biomolecules present in microbes or botanical species were found to be responsible for reduction-cum-stabilization of metal ions into their respective nanostructures (Singh et al. 2011). Biosynthesis of various nanoparticles using plants and microorganisms like bacteria, algae, fungi yeast and microbial polysaccharides is compiled below.

3.4.1 Synthesis of Nanoparticles Utilizing Plants

Biological synthesis of nanoparticles by plants is getting a lot of attention these days because of its simple, stable, rapid, cheap and eco-friendly method (Mittal et al. 2013). Additionally, plants are abundantly available, safe to handle and have a wide variability of metabolites that help in reduction. Plant extracts containing bioactive alkaloids, proteins, sugars, phenolic acids, polyphenols play an important role in first reducing the metallic ions and then stabilizing them (Castro et al. 2011). Table 3.2 compiles the information on a large number of plants being utilized for the synthesis of various nanoparticles and it is clear from the information that the synthesis of nanoparticles, their size, application all vary from plant to plant.

Table 3.2 List of various plants used for the synthesis of nanoparticles
Full size table

3.4.2 Synthesis of Nanoparticles Utilizing Bacteria

Biosynthesis of nanoparticles utilizing bacteria has gained a lot of attention in the area of green nanotechnology over the globe because of their abundance in the environment and their capacity to adjust to extraordinary conditions. Additionally, these are fast-growing, inexpensive to cultivate and simple to control (Mehrotra et al. 2019a, b; Kumar et al. 2019). Moreover, the nanoparticles synthesized from bacteria have higher catalytic reactivity, more specific surface area and are of uniform size (Mehrotra et al. 2019a, b). Various species of bacteria till now have been effectively used for the synthesis of different nanoparticles like gold, silver, zinc, cadmium sulphide, palladium, etc. (Table 3.3).

Table 3.3 Some of the nanoparticles synthesized by bacteria
Full size table

3.4.3 Synthesis of Nanoparticles Utilizing Fungi and Yeast

The utilization of fungi in the synthesis of nanoparticles has gained fast interest because of their toleration and metal bioaccumulation capability (Sastry et al. 2003). A large amount of enzymes can be produced by utilizing fungi since they are magnificent secretors of extracellular proteins, which eventually can regulate the synthesis of nanoparticles (Castro-Longoria et al. 2012). Fungi is viewed as better than bacteria in the production of nanoparticles as these secrete huge volume of proteins which directly gets converted to nanoparticles, causing higher productivity (Mohanpuria et al. 2008). Furthermore, various fungal species grow very fast, making their maintenance in the research lab simple. In a similar way, easy maintenance of yeast production in the laboratory, its rapid growth and the use of simple nutrients are some of the remarkable advantages of yeast over bacteria for the mass production of nanoparticles (Skalickova et al. 2017). Fungi and yeast have supremacy over other biological systems because of their wide diversity, simple culture methods, less time and low cost which successively lead to an eco-friendly approach for the synthesis of nanoparticles. Some of the fungal and yeast species successfully utilized for the production of the nanoparticles are documented in Table 3.4.

Table 3.4 Some of the nanoparticles synthesized by fungi and yeast
Full size table

3.4.4 Synthesis of Nanoparticles Utilizing Algae

From the past few years, the utilization of algae for the biosynthesis of nanoparticles has increased tremendously because of their simple access and efficiency (Ogi et al. 2010; Singaravelu et al. 2007). At present, they are also called as ‘biofactories’ for the synthesis of nanoparticles since they are an excellent source of biomolecules (Manivasagan and Kim 2015). These biomolecules like proteins, pigments, starch, nucleic acids, fats and secondary metabolites such as alkaloids present in the algal cell wall act as reducing agents which eventually prompts the reduction and synthesis of metal and metal oxide nanoparticles at ambient conditions (Siddiqi and Husen 2016). Also, seaweeds are advantageous over different reductants because of their high metal accumulating capability, minimal effort, plainly visible structure and anti-biological fouling properties (Davis et al. 2003). In addition, seaweeds have both anti-inflammatory and inhibitory properties that can be utilized to treat diverse ailments and stifle a few types of malignant growth (Fawcett et al. 2017). The biogenic manufacturing of different nanoparticles utilizing diverse algal species is presented in Table 3.5.

Table 3.5 List of some nanoparticles synthesized by algae
Full size table

3.4.5 Remediation Using Biogenic Polysaccharide

Polysaccharides are natural biopolymers of biological systems that have been extracted and put to extensive use. These biopolymers are renewable materials, environment friendly, non-toxic, biodegradable and have excellent functional properties. In recent years, polysaccharide nanomaterial composites have attracted attention of researchers in nanobioremediation due to improved processability, surface area, stability, tunable properties and cost-effectiveness. Table 3.6 provides an overview of biogenic polysaccharides that have been used in the preparation of bionanocomposites.

Table 3.6 List of microbial polysaccharides utilized as bionanocomposites Source: Manikandan et al. (2017)
Full size table

3.5 Nanobioremediation

Utilization of nanomaterials, synthesized from plants, algae, bacteria, fungi and yeast, to clean up the environmental pollutants such as organic or inorganic waste and heavy metals from the affected sites is termed as nanobioremediation (Yadav et al. 2017). The concept of green technology has gained immense interest in the area of nanomaterials for application in bioremediation and also due to its cost-effectiveness in large-scale use, enhanced efficiency and shortened time for the remediation process. Several other reasons contribute towards the use of nanotechnology in bioremediation. Firstly, the size in the range of nanoscale helps to increase the surface area per unit mass of a material, allowing enhanced reactivity rate. Secondly, nanomaterials exhibit quantum effect, thereby requires less activation energy to attain chemical reactions. Lastly, another feature shown by the nanomaterials is surface plasmon resonance (SPR) which can be used to detect toxic materials. There are a diverse range of multiple nanomaterials used for bioremediation, with high level of remedial versatility such as in removing wastes including hydrocarbons, heavy metals and radioactive materials like uranium, in remediation of soil, groundwater and wastewater.

The potential of nanomaterials to alleviate the pollution load is ongoing and could potentially bring about the most profound changes in the field of bioremediation sector in the upcoming years (Rizwan et al. 2014) (Table 3.7).

Table 3.7 Some of the nanoparticles used for removal of contaminants. Source: (Yadav et al. 2017; Yang et al. 2019; Vittal and Jamuna 2011)
Full size table

3.6 Conclusion

Nanotechnology has the potential to metamorphose all the existing technologies that include the techniques involving pollution control as well. This technology is gaining recognition globally for successfully removing the contaminants from the environment. The extraordinary properties of nanoparticles and their concurrence with the present day technologies offer a great opportunity to revolutionize environmental clean-up. It is clear from the reviewed literature that while much attention has been focused on the development and potential benefits of nanomaterials in water treatment processes, concerns have also been raised regarding their potential human and environmental toxicity. Biogenic synthesis of nanoparticles can solve the problem of toxicity to a great extent. Thus, the utilization of biologically synthesized nanoparticles for the process of bioremediation can go a long way in attaining a sustainable environment. Biosynthesis of nanoparticles using microbes helps to reduce the toxicity, is cheap, eco-friendly and saves time. Due to the remarkable and significant capability of nanobioremediation, it is assumed that their application will enhance at a great leap in the near future and will perform a very important and indispensable part in achieving a green and renewable environment.