Nanotechnology for Environmental Remediation by unknow

Author:unknow
Language: eng
Format: epub
ISBN: 9783527834150
Published: 2022-09-26T00:00:00+00:00

Fe3O4@SiO2‐NH2 NPs were combined with nanofiltration membranes, increasing the overall water flux and the removal efficiency for Cd as heavy metal and methylene blue dye, due to the creation of stable bond with the amine groups [75]. Fe3O4 NPs have been also modified with different ligands (silica, metmorfine, and amine) and combined with nanofiltration membranes [76].

TiO2 NPs have been also explored as modifiers for nanofiltration membranes [78]. Oleic acid‐functionalized TiO2 has been proved to increase the antibiofouling properties of filtration membranes to increase overall reusability and efficiency in water treatment [79]. L‐Cysteine‐functionalized TiO2 NPs that have been combined with polyether‐imide nanofiltration membranes result in increased water flux with improved capabilities for the removal of Pb, Cr, and Cu ions due to the presence of negative groups in the functionalized membrane for interaction with the ions [77]. TiO2 has also been combined with reduced graphene oxide into nanohybrid NPs with enhanced performance and antibiofouling properties [81]. To increase the compatibility and stability, the hybrids were functionalized with aminosilane groups.

Amine‐functionalized UiO‐66 particles were incorporated in nanomembranes and used for nanofiltration of organic solvents and dyes. Positively charged dyes, such as Rose Bengal, are successfully isolated due to electrostatic repulsion by Donnan exclusion [83]. Poly(sodium 4‐styrenesulfonate)/polyamide‐modified ZIF‐8 NPs increased the hydrophilicity and adsorption capacity of nanofiltration membranes in the removal of dyes, such as reactive black (RB) 5 and reactive blue 2, to a removal percentage of up to 99% [84]. Amine‐functionalized ZIF‐8 has been used for organic solvent nanofiltration [85].

Activated carbon‐based Janus micromotors have been employed as moving nanoadsorbents for the removal of heavy metals. The micromotors contain a platinum hemisphere that decomposes hydrogen peroxide into oxygen bubbles for efficient propulsion in water. Efficient removal of Rhodamine B, paraoxon, dinitrotoluene, Cd, and Pb is achieved in just 5 minutes with the micromotors as compared with the 30 minutes required in static (without movement) conditions [86]. rGO‐wrapped Janus micromotors have been used for the dynamic removal of polybrominated diphenyl ethers and 5‐chloro‐2‐(2,4‐dichlorophenoxy) phenol (triclosan) as model relevant pollutants. The incorporation of γ‐Fe2O3 NPs in the micromotor structure allows for reusability in consecutive cycles of persistent organic pollutants (POPs) removal. Quantitative removal of both pollutants (higher than 90%) was obtained after 10‐minute navigation of graphene‐coated micromotors, whereas only 12% and 23% removal was obtained by using static micromotors and SiO2/Pt micromotors, revealing the crucial role of graphene for the removal of the compounds [87]. Janus graphene/Fe3O4/Pt micromotors have been used for antibiotics removal, using tetracycline as a model compound, as shown in Figure 12.3a [88]. The ultraviolet–visible spectrophotometry (UV–VIS) spectra in Figure 12.3a indicate the quantitative removal of such pollutants by using moving micromotors, whereas negligible adsorption was achieved with static micromotors and control experiments in the sole presence of peroxide fuel. The magnetic nature of the micromotors allows for reusability in four consecutive cycles with almost 100% efficiency in all cases.

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