Nanomaterials for Soil Reclamation

Introduction

Environmental resilience is characterised as an important environmental interaction that prevents natural resources from declining or deteriorating, thus improving the quality of the environment for a longer period of time. However, the world’s general definition of durability or sustainability is continuous development resulting in degeneration of the environment. The rapidly increasing polluted sites have led to a wide range increment in the demand for the development of new ways and techniques and for quicker cleaning or purification of polluted sites and also to reduce the costs of technologies being used (Cecchin et al., 2016). The level of wastes and toxic materials in the environment is growing quickly with the on-going industrial development. Science and technology directly or indirectly add to increase the toxicity in environment. Due to the technological innovations across the world in different processes and products with no proper diligence to the environment, the disposal of materials or wastes into the environment is excessive and that too without proper management (Cecchin et al., 2016). Thus, the research to develop technologies to accelerate the decontamination of these sites as well as reduce the cost of these contaminant removal processes is increasingly promoted (Menendez-Vega et al., 2007). Various restoration strategies have been made to use for the conservation and betterment of environment and one such technique is Bioremediation, which involves the use of micro-organisms or also the use of nanoparticles (Zhang et al., 2020). Several technologies are available for deployment, both in-situ and ex-situ technologies. In in-situ treatment, there is no need to excavate the soils while in ex-situ, it involves polluted soil removal and off-site treatment under suitable maintained conditions (Cecchin et al., 2016). Ex-situ remediation involves the use of prefabricated bed and bioreactor. Over the years, in-situ bioremediation techniques are being used for remediation of various hydrocarbon-polluted sites specifically. In situ treatment is a very established and profitable method and it reduces expensive excavation process and emission (Menendez-Vega et al., 2007) Nanoparticles, on the other hand, have exclusive capabilities as depicted in Fig. 1, to sterilize or sanitize the environments from such harmful toxicants. They tend to provide an active base for microbial activities and thereby, triggering the cleaning process. Nano-bioremediation is the term preferred when the nanoparticles are used for pollutants removal and leading to growth in microbial activities. Nano-bioremediation is one of such kind of methods which received a lot of attention in the past few years. It aims at reducing the contaminant concentrations to risk-based levels, alleviating the additional environmental impacts simultaneously.

Figure 1.

Illustration of nanomaterials in bioremediation

This method brings the benefits of both nanotechnology and bioremediation together to achieve a remediation that is more efficient, less time taking, and environment friendly than the individual processes (Singh et al., 2020) Nanoparticles (NPs), which are used in Nano-bioremediation can be either metallic or non-metallic and of differently shapes. Nanoparticles or Nanocomplexes which are used in purification processes are of the following types- Single metal NPs, Bimetallic NPs, Carbon-based NPs, and Modified NPs etc. There are various advantages of bioremediation processes over other conventional methods as it much is cost effective, has a very high competence, involves minimal use of chemical and biological sludge, they are generally selective to specific metals. Also, there is no use of supplementary nutrient requirements, it also implicates the bio-sorbent regeneration, and greater is the possibility of metal recovery (Davis et al., 2017). Nowadays, sustainable remediation is given a lot of importance as it aims in reduction of quantities to risk-based levels as well as to minimize the environmental impacts such as greenhouse gas emissions, waste generation and natural resource consumption, among others (Cecchin et al., 2016).