Abstract
Heavy metal pollution of aquatic media has grown significantly over the past few decades. Therefore, a number of physical, chemical, biological, and electrochemical technologies are being employed to tackle this problem. However, they possess various inescapable shortcomings curbing their utilization at a commercial scale. In this regard, nanotechnology has provided efficient and cost-effective solutions for the extraction of heavy metals from water. This review will provide a detailed overview on the efficiency and applicability of various adsorbents, i.e., carbon nanotubes, graphene, silica, zero-valent iron, and magnetic nanoparticles for scavenging metallic ions. These nanoparticles exhibit potential to be used in extracting a variety of toxic metals. Recently, nanomaterial-assisted bioelectrochemical removal of heavy metals has also emerged. To that end, various nanoparticle-based electrodes are being developed, offering more efficient, cost-effective, ecofriendly, and sustainable options. In addition, the promising perspectives of nanomaterials in environmental applications are also discussed in this paper and potential directions for future works are suggested.
Highlights
A number of physical, chemical, biological, and electrochemical technologies are being employed to tackle this problem
The main focus of this review is to provide a basic insight of the conventional nanomaterials used (CNT-graphene oxide (GO), silica-based, zero-valent iron (ZVI)) and show how magnetic NP exhibit a significant advantage over these nanomaterials
One of the main problems of using Carbon nanotube (CNT) is associated with their agglomeration or bundling resulting in a lower specific surface for adsorption. When it comes to their applicability at an industrial scale, their attachment to filters should be strong enough to prevent their release into treated waters [54]
Summary
Nanomaterials (NM), due to properties such as high specific surface, porosity, surface functionalities, and ion binding capabilities, have been widely researched over the past two decades in water and wastewater treatment applications They show a high potential in the removal of metallic ions even in trace amounts [31,32]. It was found that no agglomeration takes place, so the adsorption only depends on the amount of adsorbent added Based on these studies, it can be concluded that the concentration of adsorbent affects the removal process, but it depends on the nature and chemical properties of the ad-sorbent itself, suggesting that either an increase or decrease in the removal will occur. Higher and lower volumes of NP with equal concentration will lead to the same results
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