Efficient adsorption of erythrosine and sunset yellow onto modified palladium nanoparticles with a 2-diamine compound: Application of multivariate technique

Reductive Coupling of Nitroarenes and HCHO for General Synthesis of Functional Ethane-1,2-diamines by a Cobalt Single-Atom Catalyst

Despite the extensive applications, selective and diverse access to N,N'-diarylethane-1,2-diamines remains, to date, a challenge. Here, by developing a bifunctional cobalt single-atom catalyst (CoSA-N/NC), we present a general method for direct synthesis of such compounds via selective reductive coupling of cheap and abundant nitroarenes and formaldehyde, featuring good substrate and functionality compatibility, an easily accessible base metal catalyst with excellent reusability, and high step and atom efficiency. Mechanistic studies reveal that the N-anchored cobalt single atoms (CoN4) serve as the catalytically active sites for the reduction processes, the N-doped carbon support enriches the HCHO to timely trap the in situ formed hydroxyamines and affords the requisite nitrones under weak alkaline conditions, and the subsequent inverse electron demand 1,3-dipolar cycloaddition of the nitrones and imines followed by hydrodeoxygenation of the cycloadducts furnishes the products. In this work, the concept of catalyst-controlled nitroarene reduction to in situ create specific building blocks is anticipated to develop more useful chemical transformations.

Adsorptive removal of eriochrome black T (EBT) dye by using surface active low cost zinc oxide nanoparticles: A comparative overview

The ecological toxicity imparted by non-biodegradable organic dyes has been considered as a major risk to handle in front of mankind. In this view, the low-cost zinc oxide nanoparticles (ZnO-NPs) were facially synthesized by coating the surface with surfactant (CTAB) and ionic liquid (BMTF) molecules for the effective removal of Eriochrome Black T (EBT) from aqueous media. Various advanced characterization techniques have given insight into the morphological features, crystalline structure and physio-chemical properties of as-synthesized ZnO-NPs. The systematic analysis of the adsorption isotherms and kinetics models specifies that the adsorption of EBT follow Freundlich model and pseudo-second-order kinetics. The intraparticle diffusion model displayed a linear relationship (R² = 0.98, 0.97 and 0.94 for BMTF@ZnO, CTAB@ZnO and bare ZnO-NPs), which shows that pore diffusion rate is affected by surface modification and effects the overall EBT adsorption process. Furthermore, after the removal of 87% and 84% of EBT dye by BMTF@ZnO-NPs and CTAB@ZnO-NPs, the fabricated nanoadsorbents of ZnO were successfully regenerated and reused after the treatments up to four times. The adsorption aptitude of ZnO-NPs towards EBT dye was systematically explored in real wastewater samples and interference study of inorganic metallic salts was also performed. The toxicity estimations of the treated dye solutions were made using floral and fungal activities, to ascertain their non-toxic nature before releasing into the environment. These outcomes have supported the immense potential of ZnO-NPs towards the removal of EBT in a cost effective manner.

Removal characteristics of two anionic dyes by a polyethylenimine/poly(N,N-dimethylaminoethyl methacrylate) gel

The highly efficient gel obtained via the copolymerization of polyethylenimine (PEI) and poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) was successfully applied for the removal of two anionic dyes (amaranth and sunset yellow) from their aqueous solutions. Moreover, the results of the adsorption experiments for sunset yellow and amaranth on the PEI/PDMAEMA gel demonstrate that the adsorption equilibrium both could be achieved within 1 h, and the maximum adsorption capacities were 757 mg g⁻¹ and 744 mg g⁻¹ under unoptimized conditions, respectively. Moreover, the PEI/PDMAEMA composite gel was found to be pH-sensitive and the addition of salts together with ionic strength were also explored for understanding the adsorption performance. In addition, it can be found from the studies of adsorption mechanism that it is mainly electrostatic adsorption; moreover, the separation process conforms to the Langmuir adsorption isotherm model and the pseudo second-order kinetic model, which is a spontaneous endothermic process. When the PEI/PDMAEMA gel was used in continuous flow column, it could handle large volumes of dye solution with very low concentrations due to its strong enrichment capacity. Finally, the desorption experiments show that the PEI/PDMAEMA gel is easier to regenerate and has a longer lifetime. Therefore, the high adsorption capacity and easy operation of adsorption for amaranth and sunset yellow on the PEI/PDMAEMA gel make it a potential application prospect for the practical removal of other kinds of similar pollutants.

The highly efficient gel obtained via the copolymerization of polyethylenimine and poly(N,N-dimethylaminoethyl methacrylate) was successfully applied to remove two anionic dyes (amaranth and sunset yellow) from their aqueous solutions.

A simple approach for the sonochemical loading of Au, Ag and Pd nanoparticle on functionalized MWCNT and subsequent dispersion studies for removal of organic dyes: Artificial neural network and response surface methodology studies

In this study, the artificial neural network (ANN) and response surface methodology (RSM) based on central composite design (CCD) were applied for modeling and optimization of the simultaneous ultrasound-assisted removal of quinoline yellow (QY) and eosin B (EB). The MWCNT-NH₂ and its composites were prepared by sonochemistry method and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analysis's. Initial dyes concentrations, adsorbent mass, sonication time and pH contribution on QY and EB removal percentage were investigated by CCD and replication of experiments at conditions suggested by model has results which statistically are close to experimented data. The ultrasound irradiation is associated with raising mass transfer of process so that small amount of the adsorbent (0.025 g) is able to remove high percentage (88.00% and 91.00%) of QY and EB, respectively in short time (6.0 min) at pH = 6. Analysis of experimental data by conventional models is good indication of Langmuir efficiency for fitting and explanation of experimented data. The ANN based on the Levenberg-Marquardt algorithm (LMA) combined of linear transfer function at output layer and tangent sigmoid transfer function at hidden layer with 20 hidden neurons supply best operation conditions for good prediction of adsorption data. Accurate and efficient artificial neural network was obtained by changing the number of neurons in the hidden layer, while data was divided into training, test and validation sets which contained 70, 15 and 15% of data points respectively. The Average absolute deviation (AAD)% of a collection of 128 data points for MWCNT-NH₂ and composites is 0.58%.for EB and 0.55 for YQ.

Sonochemical synthesis of amide-functionalized metal-organic framework/graphene oxide nanocomposite for the adsorption of methylene blue from aqueous solution

Graphene oxide-[Zn₂(oba)₂(bpfb)]·(DMF)₅ metal-organic framework nanocomposite (GO-TMU-23; H₂oba=4,4'-oxybisbenzoic acid, bpfb=N,N'-bis-(4-pyridylformamide)-1,4-benzenediamine, DMF=N,N-dimethylformamide) is prepared through a simple and large-scale sonochemical preparation method at room temperature. The obtained nanocomposite is characterized by Field Emission Scanning Electron Microscopy (FE-SEM), powder X-ray diffraction (PXRD) and FT-IR spectroscopy. Additionally, the absorption ability of GO-TMU-23 nanocomposite toward cationic dye methylene blue was also performed. Significantly, GO-TMU-23 nanocomposite exhibits remarkably accelerated adsorption kinetics for methylene blue in comparison with the parent materials. The adsorption process shows that 90% of the dye has been removed and the equilibrium status has been reached in 2min by using the nanocomposites as the adsorbent.

Preparation and characterization of monoliths HKUST-1 MOF via straightforward conversion of Cu(OH)2-based monoliths and its application for wastewater treatment: artificial neural network and central composite design modeling

Highly crystalline water stable monolithic HKUST-1 MOF by a straightforward conversion of Cu(OH)₂-based monoliths was prepared and characterized via FE-SEM, XRD and EDS analysis.

Sono-assisted preparation of bio-nanocomposite for removal of Pb2+ ions: Study of morphology, thermal and wettability properties

Multi-walled carbon nanotubes (MWCNT) loaded poly(ethylene terephthalate) (PET) composites, with different CNT contents, were fabricated through an ultrasound assisted method as a fast and green way. Then, the obtained composites were fully characterized via FT-IR, UV-Vis, XRD, TGA, FE-SEM and TEM, etc. For this purpose, PET bottle was recycled and applied as matrix of nanocomposites (NC)s. Then, we dispersed the covalent functionalization of MWCNTs with a protein dispersant and obtained a powder of protein-functionalized CNTs. Bio-functionalized MWCNTs showed higher Pb²⁺ removal efficiency compared to MWCNT-COOH as ascertained via batch equilibrium adsorption experiments. Also, the results indicated the novel NCs presents a high affinity for Pb²⁺ heavy metal owing to the presence of several good sites. The contact angle results indicated that the addition of MWCNT-BSA increased significantly the contact angle compared to the pure PET. It was concluded that inflame retarding feature of NC was higher than pure polymer.