Current Trends in the Application of Nanomaterials for the Removal of Pollutants from Industrial Wastewater Treatment-A Review.

In the recent decades, development of new and innovative technology resulted in a very high amount of effluents. Industrial wastewaters originating from various industries contribute as a major source of water pollution. The pollutants in the wastewater include organic and inorganic pollutants, heavy metals, and non-disintegrating materials. This pollutant poses a severe threat to the environment. Therefore, novel and innovative methods and technologies need to adapt for their removal. Recent years saw nanomaterials as a potential candidate for pollutants removal. Nowadays, a range of cost-effective nanomaterials are available with unique properties. In this context, nano-absorbents are excellent materials. Heavy metal contamination is widespread in underground and surface waters. Recently, various studies focused on the removal of heavy metals. The presented review article here focused on removal of contaminants originated from industrial wastewater utilizing nanomaterials.

Porphyrin N-Pincer Pd(II)-Complexes in Water: A Base-Free and Nature-Inspired Protocol for the Oxidative Self-Coupling of Potassium Aryltrifluoroborates in Open-Air.

Metalloporphyrins (and porphyrins) are well known as pigments of life in nature, since representatives of this group include chlorophylls (Mg-porphyrins) and heme (Fe-porphyrins). Hence, the construction of chemistry based on these substances can be based on the imitation of biological systems. Inspired by nature, in this article we present the preparation of five different porphyrin, meso-tetraphenylporphyrin (TPP), meso-tetra(p-anisyl)porphyrin (TpAP), tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (TSTpSPP), meso-tetra(m-hydroxyphenyl)porphyrin (TmHPP), and meso-tetra(m-carboxyphenyl)porphyrin (TmCPP) as well as their N-pincer Pd(II)-complexes such as Pd(II)-meso-tetraphenylporphyrin (PdTPP), Pd(II)-meso-tetra(p-anisyl)porphyrin (PdTpAP), Pd(II)-tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (PdTSTpSPP), Pd(II)-meso-tetra(m-hydroxyphenyl)porphyrin (PdTmHPP), and Pd(II)-meso-tetra(m-carboxyphenyl)porphyrin (PdTmCPP). These porphyrin N-pincer Pd(II)-complexes were studied and found to be effective in the base-free self-coupling reactions of potassium aryltrifluoroborates (PATFBs) in water at ambient conditions. The catalysts and the products (symmetrical biaryls) were characterized using their spectral data. The high yields of the biaryls, the bio-mimicking conditions, good substrate feasibility, evading the use of base, easy preparation and handling of catalysts, and the application of aqueous media, all make this protocol very attractive from a sustainability and cost-effective standpoint.

Dynamic covalent bonding-triggered supramolecular gelation derived from tetrahydroxy-bisurea derivatives.

A new class of bisurea derivatives bearing tetrahydroxy groups have been proven to be non-gelators in water and various organic solvents even under long-term sonication or efficient heating treatment. We found that it is possible to trigger physical gelation behaviour by constructing dynamic covalent bonding. The results show that formation of dynamic covalent bonding between the borate anion and ethanediol substituent in these bisurea derivatives brings about rapid physical gelation at ambient temperature in a mixture of DMSO and water. During dynamic covalent bonding-triggered gelation, the stepgrowth polymerization from the B-O bonds would increase the size of the molecules and reduce the entropy of mixing as well as facilitate ion-dipole interactions in the linear polymeric gelators. They would drive a self-assembly transition and boost the construction of gel networks in coordination with α-tape urea-urea hydrogen bonding. The gelation mechanism was explored by 1H NMR, FTIR and rheology techniques. Moreover, the resulting gels are transparent and thixotropic, and could be turned into the sol state under CO2 or water-stimulus. Furthermore, they are stable in the presence of HAuCl4 and alkali. Therefore, they would afford another new medium for the growth of Au nanocrystals via in situ reduction and a new sensing medium for detecting Hg2+ ions.

Salt Tunable Rheology of Thixotropic Supramolecular Organogels and Their Applications for Crystallization of Organic Semiconductors.

Physical gelation behaviors of a series of novel bisurea-based derivatives bearing fatty alkyl tertiary amine moieties have been explored in water and common organic solvents. One of these amines exhibits very good thixotropic gels in apolar aromatic solvents (e.g., xylenes). The corresponding sol-gel transition is instantaneous and could be repeated for at least 50 cycles. Interestingly, the elasticity and strength of the resulting gels can be remarkably enhanced initially by the addition of a trace amount of tetrabutylammonium acetate (TBA) followed by a subsequent drop with further salt addition. Temperature-dependent 1H NMR confirmed that hydrogen bonding is the main driving force for the physical gelation. TEM, rheology, 1H NMR titration, and examination of critical gelation concentration (CGC) reveal that the phenomenon is due to the dominated effects, the salting out effect at lower TBA concentration, or the anion-urea hydrogen bonding at higher TBA concentration. Furthermore, the obtained transparent gels in this work can be used as good media for growing crystals of several organic semiconductors.

Preparation of novel chitosan polymeric nanocomposite as an efficient material for the removal of Acid Blue 25 from aqueous environment.

A novel, sustainable chitosan polymeric nanocomposite (CS-PVA@CuO) was synthesized and subjected to the removal of acid blue 25 (AB25) from the aqueous environment. The influence of different variables such as pH, contact time, initial dye concentration, temperature, and adsorption kinetics has been examined in the batch adsorption process. The CS-PVA@CuO composite was systematically characterized by XRD, FTIR, SEM, and EDX analysis. The pseudo-first order (PFO), pseudo-second order (PSO), and intra-particle diffusion kinetics equations were used to examine the kinetic data of the adsorption process. The adsorption kinetics confirms that the PSO model was a more exact fit. Thermodynamics study typically revealed that the uptake of AB25 by the adsorbent is spontaneous and endothermic in nature. Remarkably, the results reveal the highest adsorption capacity of the CS-PVA@CuO was 171.4 mg/g at 313 K. To be specific, CS-PVA@CuO polymer nanocomposite can be effectively used as a suitable adsorbent material for the potential elimination of anionic AB25 dye from the aqueous solutions.

Synthesis and characterization of Cu(OH)2-NWs-PVA-AC Nano-composite and its use as an efficient adsorbent for removal of methylene blue.

The present study focused on the synthesis of copper hydroxide nanowires decorated on activated carbon (Cu(OH)2-NWs-PVA-AC). The obtained Cu(OH)2-NWs-PVA-AC Nano-composite was distinguished by XRD, SEM, EDX, BET, FTIR and XPS respectively. Besides, different variables such as solution pH, and initial dye concentration, contact time, and temperature were performed on the adsorption efficiency of MB in a small batch reactor. Further, the experimental results are analyzed by various kinetic models via PFO, PSO, intra-particle diffusion and Elovich models, and the results revealed that among the kinetic models, PSO shows more suitability. In addition, different adsorption isotherms were applied to the obtained experimental data and found that Langmuir-Freundlich and Langmuir isotherm were best fits with the maximum adsorption capacity of 139.9 and 107.6 mg/g, respectively. The Nano-composite has outstanding MB removal efficiency of 94-98.5% with a span of 10 min. and decent adsorption of about 98.5% at a pH of 10. Thermodynamic constants like Gibbs free energy, entropy, and enthalpy were analyzed from the temperature reliance. The results reveal the adsorption processes are spontaneous and exothermic in nature. The high negative value of ΔG° (- 44.11 to - 48.86 kJ/mol) and a low negative value of ΔH° (- 28.96 kJ/mol) show the feasibility and exothermic nature of the adsorption process. The synthesized dye was found to be an efficient adsorbent for the potential removal of cationic dye (methylene blue) from wastewater within a short time.

Hydrogen-free hydrogenation of nitrobenzene via direct coupling with cyclohexanol dehydrogenation over ordered mesoporous MgO/SBA-15 supported Cu nanoparticles.

Direct catalytic coupling of nitrobenzene hydrogenation and cyclohexanol dehydrogenation was studied in the gas phase over mesoporous MgO-SBA15 supported Cu nanoparticles. This approach avoids an external supply of H2 and utilizes the in situ liberated H2 from the dehydrogenation step of the first reactant for the hydrogenation reaction of the second reactant. A catalyst series consisting of four Cu/MgO-SBA15 mesoporous solids with varying Cu loadings (5-20 wt%) were prepared and systematically characterized by BET, ICP, XRD, TPR, TPD, FT-IR, SEM, XPS, and TEM. Among the series, the 15 wt% Cu catalyst exhibited the best performance with ≥82% conversion of nitrobenzene along with ≥89% cyclohexanol conversion. In addition, significantly higher yields of cyclohexanone (83%) and aniline (75%) could be achieved successfully over the same catalyst. Furthermore, the catalyst exhibited almost stable activity during 30 h time-on-stream with slow deactivation. The highly ordered mesoporous silica increases the metal-support interaction with smaller particles of Cu on the surface, and the synergism between acid-base sites is responsible for the improved catalytic activity.

CO2 utilization as a soft oxidant for the synthesis of styrene from ethylbenzene over Co3O4 supported on magnesium aluminate spinel: role of spinel activation temperature.

Magnesium aluminate spinel (MgAl2O4) supported Co3O4 catalysts are synthesized and tested for the oxidative dehydrogenation (ODH) of ethylbenzene using CO2 as a soft oxidant. The effect of spinel calcination temperature on the catalytic performance has been systematically investigated. With an increase in the activation temperature from 600 to 900 °C, the active presence of a single-phase MgAl2O4 spinel is observed. A catalyst series consisting of MgAl2O4 spinel with varying Co loadings (10-20 wt%) were prepared and systematically distinguished by ICP, XRD, BET, TPR, NH3-TPD, UV-Vis DRS, FT-IR, XPS, SEM, and TEM. Among the tested cobalt catalysts, 15Co/800MA sample derived by calcination of MgAl2O4 support at 800 °C exhibits the most excellent catalytic performance with the maximum ethylbenzene conversion (≥ 82%). Also, high yields of styrene (≥ 81%) could be consistently achieved on the same active catalyst. Further, the catalyst exhibited almost stable activity during 20 h time-on-stream with a slow decrease in the ethylbenzene conversion from 82 to 59%. However, the selectivity of styrene (98%) stayed almost constant during the reaction. Activation of the MgAl2O4 spinel at 800 °C facilitates a dramatic chemical homogeneity for the alignment of Co3O4 nanoparticles on the surface of the active catalyst. Moreover, the isolated Co3O4 clusters have a strong chemical/electronic interaction with the Mg2+ and Al3+ ions on the support perform a crucial role to achieve the maximum catalytic activity.