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Preface
The chapters included in the book are differentiated into three sections: the first section covers various "carbon nanomaterials" with a focus on the use of nanoscale carbon applied to wastewater research. The book also covers recent advances in the field and perspectives on future research and development of smart materials for wastewater applications.
CARBON NANOMATERIALS
Easy and Large-Scale Synthesis of Carbon Nanotube-Based Adsorbents
Solutions
Introduction
In recent years, CNTs could be produced in ton-scale quantities per year with high quality. After adsorption, the MCNTs adsorbents could be efficiently and instantly separated using a magnet, reducing potential risks of CNTs as another source of environmental pollution.
Removal of Arsenic from Aqueous Solution
- Activated Magnetic Carbon Nanotube
- Synthesis Method
- Characterization of Adsorbents
- Adsorption Properties
- Sulfhydryl-Functionalized Magnetic Carbon Nanotube
- Synthesis Method
- Characterization of Adsorbents
- Adsorption Properties
In Figure 1.2a, thermogravimetric analysis (TGA) of MI/CNT shows two main regions of weight loss. The magnetization properties of GMI-CNTs were investigated at room temperature by measuring the magnetization curves as shown in Figure 1.13b.
Removal of Organic Pollutants from Aqueous Solution
- Magnetic Carbon Nanotubes for Dye Removal
- Synthesis Method
- Characterization of Adsorbents
- Adsorption Properties
- Magnetic CNTs/C@Fe/Chitosan for Tetracycline Removal
- Synthesis Method
- Characterization of Adsorbents
- Adsorption Properties
For further investigation of the structure, the XRD patterns of CNTs/C@Fe and CNTs/C@Fe/CS were tested as shown in Figure 1.26. The magnetization characteristics of CNT/C@Fe and CNT/C@Fe/CS were investigated at room temperature (Figure 1.28b).
Summary and Outlook
In addition, improved manufacturing and large-scale production have already caused the price of CVD-produced CNTs to drop significantly; therefore, MI/CNTs may be a promising magnetic adsorbent for pollutant removal using APCNTs. The results of this work are very important for the large-scale practical use of already prepared single-walled or multi-walled CNTs containing Fe catalytic particles without the need for preliminary purification.
Acknowledgment
Mitra, Removal of trace amounts of arsenic to meet drinking water standards using iron oxide-coated multi-walled carbon nanotubes. Wu, Adsorption of toluene, ethylbenzene and m-xylene on multi-walled carbon nanotubes with different oxygen contents from aqueous solutions. Chen, Enhanced adsorptive removal of methyl orange and methylene blue from aqueous solution by alkali-activated multiwall carbon nanotubes.
Chen, Unipod, large-scale synthesis of magnetically activated carbon nanotubes and their applications for arsenic removal.
Potentialities of Graphene-Based Nanomaterials for Wastewater
Treatment
Introduction
Carbon-based materials, especially activated carbon, are mostly used in wastewater treatment due to their high specific surface area, versatility, chemically and mechanically. Within this framework, this chapter focuses on graphene-derived materials as nano-adsorbents for wastewater treatment. First, a brief overview of the two general routes adopted for graphene synthesis is presented, including representative methods for each route.
The main features of the methods used for the preparation of the nano-adsorbents, as well as their possible regeneration and reuse after saturation, are briefly summarized.
Graphene Synthesis Routes
For example, excluding NaNO3, increasing the amount of KMnO4 and using a mixture of concentrated H2SO4/H3PO4 in the ratio of 9:1 led to an increase in the efficiency of the oxidation process, which provided a higher yield of hydrophilic oxidized graphene with fewer errors compared to the conventional Hummer method. The results revealed disturbances in the stacking order of graphite amido black (AB) with increasing oxidation levels, as well as the formation of hydroxyl and carboxyl groups at lower oxidation levels and epoxide groups at higher ones. Cross-flow filtration has been proposed to promote the purification of large amounts of GO required on an industrial scale [ 20 , 33 ].
Liquid phase exfoliation, which is based on the use of surfactants or solvents that intercalate between graphite layers to facilitate separation of graphene nanosheets, is another example of the top-down methods.
Adsorption of Water Pollutants onto Graphene-Based Materials
- Adsorption of Heavy Metals
- Adsorption of Organic Contaminants
- Dyes
- Other Organic and Emerging Contaminants
The amount of PVA anchored on the interlamination of the GO membranes was a crucial factor in determining the adsorption capacity of. 93] who investigated the effect of the degree of reduction of RGO and the amounts and distributions of the remaining oxygen-containing functional groups on the adsorption of ten phenolic compounds (Table 2.3). The specific surface area of the RGO sponge played a predominant role in the adsorption of these contaminants, while the surface charge had virtually no effect.
The adsorption of ciprofloxacin (CIP) and norfloxacin (NOR) by RGO-Fe3O4 was reported as a spontaneous and exothermic process, and a synergistic structural effect was suggested in terms of preventing the aggregation of magnetic microparticles and improving the stability of RGO sheet [48].
Comparison of the Adsorption Performance of Graphene-Based
In personal care products, the use of a β-CD-GO/Fe3O4 magnetic nanocomposite for the adsorption of p-phenylenediamine (PPD), a toxic component of hair coloring products, has been studied [102]. It was suggested that CD would increase the adsorption capacity of the adsorbent through the formation of inclusion complexes in solution with organic molecules through host-guest interactions. The results in Table 2.1 also indicate a better performance of the CS/SH-GO composite in the adsorption of both Cu(II) (425 mg g–1) and Cd(II) (117 mg g–1) compared with those reported for the other adsorbents under similar conditions, with the exception of thiol-functionalized magnetic GO, which shows a slightly higher adsorption capacity of Cd(II) ion (125 mg g–1).
Similarly, a rough comparison of the results in Table 2.2 for the adsorption of MB, which has been mostly tested as probe organic molecule, under similar experimental conditions, points to preoxidized GO as the nanoadsorbent with the best performance (1939 mg g– 1) , followed in descending order by 3D GO-DNA hydrogel (1100 mg g-1).
Regeneration and Reutilization of the Graphene-Based Adsorbents
Moreover, in the case of the developed CS/GO monolith, the unidirectional porous structure facilitated the release of Cu(II) ions from the adsorption sites. The adsorption capacity decreased in each of the five subsequent cycles using β-CD/poly(acrylic acid)-GO [12]. Organic contaminants make it difficult to reuse the GO/RGO based adsorbents, consistent with the behavior commonly found in other carbon based adsorbents.
NaOH was also used as a desorbing agent for some of the magnetic GO-based nanoparticles [101].
Conclusion
Acknowledgements
Nomenclature
Zhang, Preparation and characterization of chitosan/graphene oxide composites for the adsorption of Au(III) and Pd(II). Zhang, Synthesis of three-dimensional graphene oxide foam for the removal of heavy metal ions. Liu, Adsorption of clofibric acid from aqueous solution by graphene oxide and the effect of.
Xian, Recyclable removal of bisphenol A from aqueous solution by reduced graphene oxide - magnetic nanoparticles: Adsorption and desorption.
Nanoparticles for the Degradation of Water Pollutants
Introduction
In the case of refractory species, however, the conversion may be only partial, otherwise severe conditions may be necessary to handle these compounds and their derivatives. It requires only an oxidizing agent (preferably atmospheric oxygen) and reagent photons of appropriate wavelength (ideally from the near UV/Vis and visible regions of the electromagnetic spectrum to facilitate the use of sunlight) [1-6], in the presence of a semiconductor material (the photocatalyst) with a large band gap (typically 3.2 eV in the case of TiO2) in the region of the water redox potential. Despite its relatively large band gap, TiO2 absorbs mostly UV light (only 5% of the solar spectrum) with a weak tail in the near-UV to visible range, and thus has limited activity under visible light irradiation.
This prompted researchers to search for modified TiO2 materials with enhanced absorption in the visible light range.
Experimental
- Carbon Materials Preparation
- Synthesis of Carbon–TiO2 Hybrid Catalysts
- Synthesis of Au-Loaded TiO2 Catalysts
- Catalysts Characterization
- Photocatalytic Degradation of DP Using Hybrid Catalysts
The point of zero charge (PZC) value of the material was determined by intercepting the resulting final pH versus initial pH curve with the straight line final pH = initial pH. The morphology of the composites was determined by scanning electron microscopy (SEM) in a FEI Quanta 400FEG ESEM/EDAX Genesis X4M instrument. The UV-Vis spectra of the solid powder materials were measured on a JASCO V-560 UV-Vis spectrophotometer equipped with an integrating sphere attachment (JASCO ISV-469).
A Heraeus TQ 150 medium-pressure mercury vapor lamp was used as a radiation source providing near UV-Vis radiation (λ > 350 nm), while a long-pass filter was used for visible light experiments (λ > 430 nm ).
Results and Discussion
- Materials Characterization
- Diphenhydramine Photocatalytic Degradation
In fact, the highest photocatalytic performance under near-UV-Vis irradiation was found for the GO composite (Au/GO–TiO2) and for the ND composite (Au/ND–TiO2). These effects may account for the higher photocatalytic performance of both Au/GO–TiO2 and Au/ND–TiO2 composites. The photocatalytic activity of Au/TiO2 and the Au/carbon-TiO2 composites for the degradation of DP under visible light irradiation (λ = 420 nm) was also evaluated for a longer reaction time (240 min, Figure 3.7b), and the respective pseudo-first-order rate constants are shown in Table 3.3.
Again, the results show that the Au/GO–TiO2 composite showed the highest photocatalytic activity min–1).
Conclusions
However, the results obtained for Au photocatalysts suggest the existence of different activation mechanisms depending on the type of carbon material and the wavelength of radiation used [75]. Silva, Synthesis, spectroscopy and characterization of titanium dioxide-based photocatalysts for the degradative oxidation of organic pollutants, Ph.D. Chen, Preparation of Au/TiO2 catalysts from Au(I)-thiosulfate complex and study of their photocatalytic activity for the degradation of methyl orange.
Soria, Fourier Transform Infrared Study of the Performance of Nanostructured TiO2 Particles for the Photocatalytic Oxidation of Gaseous Toluene.
Carbon Nanomaterials for Chromium (VI) Removal from Aqueous Solution
- Introduction
- Carbon Nanomaterials for Heavy Metal Removal
- Latest Progress in Nanocarbon Materials for Cr(VI) Treatment
- Graphene and Graphene Oxide–Based Materials
- Magnetic-Based Graphene Materials
- MWNT and SWNT
- Magnetic Carbon Adsorbents
- Summary
The adsorption capacity of CNTs was found to be much higher than that of activated carbon due to the large surface area which helps in the strong interaction between CNTs and dioxins [26]. 31] reported that the adsorption capacity of MWNTs increases with increasing pH and that the capacity can be 0–99% in the pH range of 2–9. The adsorption and photocatalytic reduction of Cr(VI) decreased with increasing pH due to the decrease in the electrostatic interaction between Cr(VI) and TiO2-RGO [40].
The adsorption isotherm of Cr(VI) on PmPD/Fe3O4/MWNTs fit the Langmuir isotherm model and the maximum adsorption capacity was 346 mg g–1.
Acknowledgement
Liu, Removal of zinc(II) from aqueous solution by purified carbon nanotubes: Kinetics and equilibrium studies. Yue, Removal of lead(II) from aqueous solution by adsorption onto manganese oxide-coated carbon nanotubes. Tseng, Efficient adsorption of chromium(VI)/Cr(III) from aqueous solution using multiwalled carbon nanotubes with functionalized ionic liquid as super sorbent.
Yan, Synthesis of poly(m-phenylenediamine)/iron oxide/acid oxidized multi-wall carbon nanotubes for hexavalent chromium removal.
Nano-Carbons from Pollutant Soot: A Cleaner Approach toward Clean
Environment
Introduction
9] collected a variety of BC (both from indoor and outdoor atmospheres) directly on the transmission electron microscope grating (TEM). The TEM image along with the SAED pattern shows the presence of prominent graphite reflection rings for the sample collected from the diesel engine exhaust, shown in Figure 5.1c. Recently, few groups have used this polluting soot BC as a 'carbon precursor' for nanocarbon synthesis, demonstrating the potential for a wide range of multifunctional applications, especially for BC collected outdoors.
Sarkar and co-workers used diesel engine exhaust waste as DPM for the synthesis of water-soluble fluorescent CDs (wsCD) with near-infrared (NIR) emission [ 30 ].
Separation of Nano-carbon from Pollutant BC
The visualization of the surface morphology of Soxhlet-purified DPM was done by FESEM (Figure 5.2b), which shows the spherical nature of CDs with the diameter ranging from 60 to 120 nm (histogram shown in the inset of the figure) with a lot of amorphous carbon . Powder XRD analysis (Figure 5.3d) confirms the graphitic nature of CNPs, showing the presence of two prominent diffraction peaks at 2θ = 23.68° and 42.01°. Furthermore, the crystallinity of obtained graphite was characterized by the Raman spectroscopy for the analysis of characteristic D and G band as illustrated in Figure 5.3e.
Anthropogenic collected MWCNTs were isolated from indoor spider web via the oxidation method, as shown in Figure 5.5(a–d) [6], when long-term exposure to atmospheric oxygen produces ROS.
![Figure 5.3 Characterization of CNPs synthesized by pyrolysis of diesel: (a) FESEM image, (b) low-resolution TEM image, (c) high-resolution TEM image, (d) XRD spectra, and (e) Raman spectra [76].](https://thumb-ap.123doks.com/thumbv2/123dok/10299589.0/188.918.114.814.125.408/figure-characterization-synthesized-pyrolysis-resolution-resolution-spectra-spectra.webp)
Functionalization of Nano-
Carbons Isolated from Pollutant BC
Nano-Carbons from Pollutant Soot for Wastewater Treatment
- Removal of Organic Pollutant
