Heavy metals are toxic and non-biodegradable environmental contaminants that seriously threaten human health. The remediation of heavy metal-contaminated water and soil is an urgent issue from both environmental and biological points of view. Recently, nanomaterials with excellent adsorption capacities, great chemical reactivity, active atomicity, and environmentally friendly performance have attracted widespread interest as potential adsorbents for heavy metal removal. This review first introduces the application of nanomaterials for removing heavy metal ions from the environment. Then, the environmental factors affecting the adsorption of nanomaterials, their toxicity, and environmental risks are discussed. Finally, the challenges and opportunities of applying nanomaterials in environmental remediation are discussed, which can provide perspectives for future in-depth studies and applications.

Heavy metal (HM) pollution is increasingly becoming a serious threat to public and environmental health with more-than-ever rapid industrialization and urbanization activities. Phytoremediation is a sustainable and largely accepted technology because of its low cost, simple operation, environmental safety and recognized as a promising approach for environmental remediation applications. Hyperaccumulator plants are the core of phytoremediation, and the study of their accumulation, detoxification, and HM tolerance mechanisms is fundamental to the progress of phytoremediation. In-depth investigations to understand the physiochemical and dissipation pathways of hyperaccumulators such as Leersia hexandra Swartz (L. hexandra) which can serve as a useful tool in environmental remediation applications. L. hexandra as a chromium hyperaccumulator plant, can also be a remarkable choice to remediate copper and nickel contaminated soils. Therefore, this article summarizes the previous studies on the detoxification strategies/tolerance mechanisms and the enhancement of the properties of L. hexandra, which will inspire its future applications in the sustainable environmental cleanup initiatives.

Cr (VI) is hazardous to humans and our environment. Leersia hexandra Swartz (L. hexandra) is the first wet chromium hyperaccumulator found in China. This study constructed the L. hexandra constructed wetland-microbial fuel cell (CW-MFC) system to treat Cr (VI) wastewater. It also determined the effects of different dissolved oxygen (DO) concentrations on power generation, pollutant removal, and Cr (VI) reduction. Cathode aeration promoted the voltage output and pollutant removal of the L. hexandra CW-MFC when the DO concentration was 4.5 mg·L⁻¹: the highest voltage was 520 mV, the chemical oxygen demand (COD) removal rate was 93.73%, and the Cr (VI) removal rate was 97.77%. Moreover, the increase in the DO concentration improved the absorption of heavy metal Cr by the substrate and L. hexandra, and promoted the transformation from Cr (VI) to Cr (III). Chromium mostly exists as a residue with low toxicity and low mobility in L. hexandra and the substrate. This proves that the increased DO concentration promotes the redox reaction in the system and plants, reducing Cr (VI) to Cr (III). At the same time, the key micro-organism Geobacter that enhances the performance of the system and Cr (VI) reduction was found. The research results can provide a reference for the subsequent CW-MFC treatment of actual Cr-containing wastewater.