Nanomaterials have been extensively studied for heavy metal ions and dye removals from wastewater. This article reviews the role of nanomaterials as effective adsorbents for wastewater purification. In recent years, numerous novel nanomaterial adsorbents have been developed for enhancing the efficiency and adsorption capacities of removing contaminants from wastewater. The innovation, forthcoming development, and challenges of cost-effective and environmentally acceptable nanomaterials for water purification are discussed and reviewed in this article. This review concludes that nanomaterials have many unique morphological and structural properties that qualify them to be used as effective adsorbents to solve several environmental problems. Graphical Abstract& Hamidreza Sadegh

Removal of noxious materials such as heavy metal ions (which are hazardous above certain ppm concentration) from wastewater is one of the biggest environmental challenges that suffers the Downloaded by [New York University] at 19:39 22 June 2015 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 economy nowadays. On the basis of their versatility, environmental friendliness, the adsorption was proved to be a most economical and efficient technology, which is used extensively for their removal from the aqueous media. Among the various developed adsorbents used so far, carbon nanotubes (CNTs) show a unique impact on the fast adsorption and rapid removal of noxious impurities from the aqueous source. CNTs festooned on the sources like activated carbon, nanoparticles and nanocomposities enhanced the efficiency and potential of the adsorbent. Due to their unique structural, electronic, optoelectronic, semiconductor, as well as mechanical, chemical and physical properties, they have been extensively used to remove heavy metals in wastewater treatment. The adsorption mechanisms is majorly contributed by the chemical interactions between the metal ions and the functional groups present on the surface of the CNTs.Greater the surface area more will be the number of reducing groups hence more attributable to better CNT sorption performances.Graphical Abstract: schematic for interaction of carbon nanotube with heavy metal ions in aqueous solution

Rapid removal of noxious synthetic dyes from wastewater is of great concern in the scientific research field, this is due to the expansion of harmful effects of synthetic dyes traces in water streams on the environment and human health with the exponential rise in concentration of synthetic dye globally and demand in various industries that coincided with the implantation of more stringent water quality standards. Various technologies have been applied for the removal of synthetic dye from wastewater, including adsorption technology, which has a great potential in treating varieties of synthetic dyes. This article comprehensively reviews the latest progress in the development of carbon nanotubes (CNTs) and their applications for the removal of synthetic dyes from wastewater, including functionalized of CNTs and their researched counterparts. The emerging trends in the development of alternative adsorbents with different substrates, morphologies, and functional groups are also elucidated.

Novel photocatalyst membrane materials were successfully fabricated by an air jet spinning (AJS) technique from polyvinyl acetate (PVAc) solutions containing nanoparticles (NPs) of titanium dioxide (TiO2). Our innovative strategy for the production of composite nanofibers is based on stretching a solution of polymer with a high-speed compressed air jet. This enabled us to rapidly cover different substrates with TiO2/PVAc interconnected nanofibers. Surprisingly, the diameters of the as-spun fibers were found to decrease with increasing amount of NPs. Our results showed that AJS PVAc-based fibrous membranes with average fiber diameters of 505-901 nm have an apparent porosity of about 79-93% and a mean pore size of 1.58-5.12 μm. Embedding NPs onto the as-spun fibers resulted in increasing the tensile strength of the obtained composite fiber mats. The photodegradation property of TiO2 membrane mats proved a high efficiency in the decomposition of methylene blue dye. The novel fiber spinning technique discussed in this paper can provide the capacity to lace together a variety of types of polymers, fibers and particles to produce interconnected fibers layer. Our approach, therefore, opens the door for the innovation in nanocomposite mat that has great potential as efficient and economic water filter media and as reusable photocatalyst.

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A new, simple chemical route was developed for the synthesis of pure nanocalcite crystals by controlling the reaction of an aqueous solution of CaO and CO2 gas. Results revealed formation of well-defined and pure nanocalcite crystals with controlled crystallite and particle size, without additives or organic solvents. The crystallite and particle size can be controlled, and smaller sizes are obtained by decreasing the CaO concentration and increasing the CO2 flow rate. The decrease of crystallite and particle size below a certain threshold provides the nanocalcite crystal signature characteristics that can be clearly observed in XRD patterns, TEM images, FTIR spectra, Raman spectra, XPS spectra, and thermal stability measurements.

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