ABSTRACT
Among the most serious threats to soil and water supply are persistent organic compounds and heavy metals that pollute the soil, which accumulate in the soil of agricultural fields and reach the food chain, causing serious health effects. Recently, scientists have tried to search for advanced methods and continuity between them, such as treatment with nano-phytoremediation, in order to demonstrate real efficiency in removing persistent organic pollutants and heavy metals in soil and water. Phytoremediation is a mechanism that uses the green plants to decontaminate, uptake, stabilize, metabolize, or detoxify contaminants from soil, water, and waste. Plants with unusual metal-accumulating ability of metals in their above-ground parts are known as hyperaccumulator plants, such as Alyssum bertolonii, Thlaspi caerulescens, Calendula officinalis, and Tagetes erecta. Significant surface areas, a high number of active surface sites and high adsorption capabilities make nanomaterials a favorable alternative for polluted soil remediation. The different physical and chemical properties of heavy metal ions and interactions with nano zerovalent iron (nZVI)-based materials play an important role in different adsorption processes, including 446adsorption, redox, aggregation, ion exchange, hydroxylation, and subsequent precipitation. Unfortunately, the direct use of nZVI is restricted by powder state as a result of the small particle size and, and the intrinsic characteristics of nZVI to react with surrounding media or agglomerate during the preparation process decreases the reactivity of nanoparticles and also results in poor mobility and efficient transfer of nZVI to the contaminated area for continuous in situ remediation. To address this problem, integrating phytoremediation with nanotechnology provides a better solution for heavy metals and hydrophobic organic pollutants remediation, through various mechanisms. Nanomaterials can enhance phytoremediation by direct pollutant removal by nanomaterials through redox reactions, surface processes, adsorption, ion exchange, surface complexation, and electrostatic interaction, or by improving plant growth and development, such as plant-growth promoting rhizobacteria (PGPR), applying plant growth regulators and using transgenic plants, and increasing the phytoavailability. Several authors studied the combination between nanotechnology and phytotechnology for detoxification of organic pollutants and remediation of heavy metals in contaminated environments. Integration of organic acids (i.e., citric, malic, tartaric, and oxalic acids), organic amendments, and nZVI with phytoremediation are feasible practices for the repair of metal polluted soils, which can be because of the resulting increase in reactive surface locations, higher nZVI volume to surface area, which might bind to more metal ions and enhancing availability of heavy metals for phytoremediation. Moreover, recent studies have shown beneficial effects of microorganisms in the rhizosphere with nanotechnology on the performance of phytoremediation in removing heavy metals. The combination of bioamendments with nZVI remediation techniques maximizes the favorable effect of nZVI and minimizes its toxicity and improves growth parameters and gas exchange, leading to new insight into nZVI heavy metal remediation. Green nanotechnology can provide safe and environmentally friendly possibilities to clean and manage the ecosystem without harming the nature. The appropriate types of plants and nanomaterials must be selected to uptake the pollutants, along with improving the agricultural management of the high-precision cleaning process. For example, the combination of Ficus ZVI (F–Fe0), ipomoea–silver (Ip–Ag0), and brassica–silver nanoparticles (Br–Ag0) as green nanotechnology, and Plantago major as phytoremediation has played a principal role in the clean-up of water and soil polluted with chlorfenapyr (Romeh and Saber, 2020). In addition, the contribution of adsorbents assisted by F–Fe0, in particular, wheat bran (WB) and P. major would play an effective role in the complete removal of chlorpyrifos from the water with a significant 447reduction in the dangerous degradation product TCP (Rady et al., 2019). It can be concluded that the impact of Fe0 on phytoremediation may be an important issue, and alternatives are required to mitigate its potential negative effects on phytoremediation or accelerate its positive effects.
