A state-of-the-art of phytoremediation approach for sustainable management of heavy metals recovery

Abstract

Phytoremediation is deemed as an efficient and environmentally friendly alternative which utilizes different types of hyperaccumulator plants known as macrophytes for the removal of heavy metal pollutants from water through different mechanisms including phytoextraction, rhizofiltration, phytovolatilization and phytostabilization. The phytoremediation efficiency is affected by several key factors such as plant species (floating, emergent and submerged), surrounding climate (temperature of about 27 °C with sufficient sunlight and water) and environmental conditions (appropriate amount of sodium chloride, nutrients and chelating agents at pH of 5 to 6). The main problem of phytoremediation is the potential secondary pollution due to the re-released of absorbed contaminants by plants which requires utmost attention. The post-treatment disposal and handling methods of post-phytoremediation plants are reviewed extensively. Heat treatment method is able to produce valuable biochemicals at high temperatures range from 160 to 1600 °C. Extraction treatment can extract up to 99 % of heavy metals, while composting requires relatively low energy usage. Synthesis of nanomaterials from phytoremediated plants reduce the usage of hazardous chemicals but hard to be upscaled. Meanwhile, phytomining is economically feasible (saving of up to $8,710 per hectare of crops) but restricted to certain heavy metal treatment. The major hurdle remains in the capability of these methods to achieve great balance between economic viability and environmental impacts. Therefore, the ultimate goal of this paper is to provide the technical assessment and perspective views in optimizing the phytoremediation performance as well as addressing the underlaying issues corresponded to the available post-phytoremediation treatment disposal and handling methods in order to amplify the commercial value of phytoremediation process as a whole.