New Technologies in the Synthesis of Nano-Structures used in Wastewater Treatment- A Review

Nanotechnology is the engineering of functional systems on a molecular scale, which refers to the projected ability to construct materials, tools, and new systems via controlling individual atoms and molecules through the characteristics of particles of matter at the nano-meter scale. One of the main environmental applications of nanotechnology is in the wastewater treatment processes. Mining activities can lead to serious problems such as acidic waste production, heavy metals pollution, cyanide spills, and the pollution by organic pollutants. There are several techniques to eliminate the above pollutants from the wastewater including precipitation, ion exchange, membrane filtration technology, electrochemical methods, and the absorption process. Currently, absorption process is one of the most effective and economic techniques for wastewater treatment. Carbon nanotubes (CNT) and Nano metal oxides are flexible and reusable nanoscale structures, which make them more advantageous over the other nanostructures. Moreover, they have more applications due to their higher surface area in comparison with other particles. This review explains the application of these nanostructures in wastewater treatment

Thermal Transformation of Secondary Resources of Carbon-Rich Wastes into Valuable Industrial Applications

Carbon-based materials have become an indispensable component in a myriad of domestic and industrial applications. Most of the carbon-based end-of-life products discussed in this review end up in landfills. Where recycling is available, it usually involves the production of lower-value products. The allotropic nature of carbon has been analysed to identify novel materials that could be obtained from used products, which also transform into a secondary carbon resource. Thermal transformation of carbon-rich wastes is a promising and viable pathway for adding value to waste that would otherwise go to landfills. The valorisation routes of four different carbon-rich wastes by thermal transformation are reviewed in the study—automotive shredder residue (ASR), textile wastes, leather wastes, and spent coffee grounds (SCGs). Textile wastes were thermally transformed into carbon fibres and activated carbon, while ASRs were used as a reductant to produce silicon carbide (SiC) from waste glass. The leather wastes and spent coffee grounds (SCGs) were employed as reductants in the reduction of hematite. This paper examines the possible routes of thermally transforming carbon-rich wastes into different industrial processes and applications. The transformation products were characterised using several techniques to assess their suitability for their respective applications. The strategy of valorising the wastes by thermal transformation has successfully prevented those wastes from ending up in landfills

Highly mesoporous hybrid transition metal oxide nanowires for enhanced adsorption of rare earth elements from wastewater

Removal of rare earth elements (REEs) from industrial wastewater is a continual challenge. To date, several approaches to the synthesis of nanoadsorbants for this application have been reported, although these are characterized by insufficient adsorption capacity and limitations in cycling stability. The present work reports the fabrication and performance of hierarchical hybrid transition metal oxide (TMO) nanowires deposited on carbon fibers. An ordered assembly of hybrid TMO nanowires exhibits an outstanding adsorbance of 1000 mg·g−1 of REEs with 93% recyclability. This superior performance is attributed to the unique mesoporous architecture of the nanowires, which exhibits a high surface area of 122 cm3 ·g−1 . Further, rapid adsorption/desorption of the REEs reveals minimal morphological alteration and hence high structural stability of these hybrid TMO nanowires after multiple cycles. The ready accessibility of the adsorption sites at crystallite boundaries and the surfaces as well as rapid adsorption of the REEs on the mesoporous nanostructure facilitate considerable adsorption capacity, improved structural stability, and extended cyclability, all of which suggest the potential for this material in REE extraction