Nanosorbent based on coprecipitation of ZnO in goethite for competitive sorption of Cd(II)-Pb(II) and Cd(II)-Pb(II)-Ni(II) systems.

Amongst the various water pollutants, heavy metal ions require special attention because of their toxic nature and effects on humans and the environment. Preserving natural resources will have positive impacts on living conditions by reducing diseases and water treatment by nanotechnology is effective in solving this problem owing to the properties of nanomaterials. In this study, a goethite nanoparticle was prepared by hydrothermal method, while ZnO/goethite nanocomposite by co-precipitation was developed. The nanoparticles were characterized using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Transform Electron Microscopy (TEM), Thermogravimetric Differential Thermal Analysis (TGA-DTA), Dynamic Light Scattering (DLS), and Breunner-Emmet-Teller (BET) surface area analysis. The adsorption of Cd(II)-Pb(II) and Cd(II)-Pb(II)-Ni(II) ions systems on ZnO/goethite nanocomposite was investigated in a batch mode. The findings of the study showed that nanoparticles ZnO/goethite composite were mixed of spherical and rod-like shapes. The BET results revealed average particle sizes of 41.11 nm for nanoparticles for ZnO/goethite while TGA/DTA confirmed the stability of the adsorbents. The optimum adsorption capacities of the nanocomposite for Pb(II), Cd(II), and Ni(II) ions from the Pb-Cd-Ni ternary system were 415.5, 195.3, and 87.13 mg g-1, respectively. The adsorption isotherm data fitted well with the Langmuir isotherm model. The study concluded that the nanoparticle adsorbents are efficient for the remediation of toxic pollutants and are, therefore, recommended for wastewater treatment.

Aluminium dross waste utilization for phosphate removal and recovery from aqueous environment: Operational feasibility development.

The need to minimize eutrophication in water bodies and the shortage of phosphate rock reserves has stimulated the search for sequestration and recovery of phosphate from alternative sources, including wastewater. In this study, aluminium dross (AD), a smelting industry waste/by-product, was converted to high-value material by encapsulation in calcium alginate (Ca-Alg) beads, viz. Ca-Alg-AD and utilized for adsorptive/uptake removal and phosphate recovery from an aqueous environment. Encapsulation of AD in alginate beads solves serious operational difficulties of using raw AD material directly due to density difference constraining efficient contact of AD with pollutants present in water and post-treatment recovery of AD material. The phosphate removal was evaluated in both batch and continuous flow operation modes. The batch adsorption study revealed 96.86% phosphate removal from 10 mg L-1 of initial phosphate concentration in 70 min of optimal contact time. Further, the phosphate removal potential of Ca-Alg-AD beads turned out to be independent of solution pH, with an average of 95.93 ± 1.40 % phosphate removal in the 2-9 pH range. The result reflects phosphate adsorption on Ca-Alg-AD beads following a second-order pseudo-kinetic model. Ca-Alg-AD beads-based adsorption followed Freundlich and Langmuir isotherm models. Further, a continuous packed bed column study revealed a total phosphate adsorption capacity of 1.089 mg g-1. The chemical composition, physical stability, and surface properties of Ca-Alg-AD beads were analyzed by means of state-of-the-art analytical techniques, such as Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy (SEM-EDX), Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetry/Differential Thermal Analysis (TG/DTA). These characterization techniques comprehend the mechanism and influence of surface properties and morphology on the phosphate adsorption behaviour, which induce the involvement of multiple mechanisms such as ligand complexation, ion exchange, and electrostatic attraction for phosphate adsorption on Ca-Alg-AD beads.

Recent Developments in Electrodeposition of Transition Metal Chalcogenides-Based Electrode Materials for Advance Supercapacitor Applications: A Review.

High-performance supercapacitive electrode materials have received significant attention from researchers worldwide, thus aiming for comparable performance similar to the extensively used rechargeable batteries. For emerging energy storage technologies like flexible supercapacitors, transition metal chalcogenides (TMCs) have been in the spotlight due to their promising electrochemical features compared to other electrode materials. Among the synthesis techniques, electrodeposition-mediated preparation of thin films of TMCs offered an affordable binder-free approach for electrode fabrication that effectively improved the supercapacitor performance. Hence, this review mainly focussed on the electrodeposition-based syntheses of single/ multinary chalcogenides and their composites for supercapacitors applications. Further, the effects of different deposition parameters were discussed for boosting the supercapacitor performance. Finally, this review outlined the existing challenges and future perspectives in this research domain, which will assist the upcoming exploration in the energy storage field.

Heterojunction assembled CoO/Ni(OH)2/Cu(OH)2 for effective photocatalytic degradation and supercapattery applications.

Mixed multimetallic-based nanocomposites have been considered a promising functional material giving a new dimension to environmental remediation and energy storage applications. On this concept, a hybrid ternary CoO/Ni(OH)2/Cu(OH)2 (CNC) composite showing sea-urchin-like morphology was synthesized via one-pot hydrothermal approach, and its photocatalytic and electrochemical performances were investigated. The photocatalytic performance was explored using Congo red (CR) as a dye pollutant under visible light illumination. The presence of mixed phases of ternary metal ions could minimize the recombination efficacy of photogenerated charge carriers on the basis of the heterojunction mechanism, resulting in 90% degradation of CR dye (40 mg L-1). The effect of scavengers coupled with electrochemical experiments revealed O2-. radical as the predominating species responsible for the degradation of CR. From the electrochemical analysis of CNC, the well-distinguished redox peaks indicated the redox-type nature with a specific capacity of 405 C g-1. For practical applications, an supercapattery (CNC( +)|KOH|AC( -)) was assembled furnishing an energy density of 42 W h kg-1 at a power density of 5160 W kg-1 at 5 A g-1 along with a high capacity retention and coulombic efficiency of 98.83% over 5000 cycles.

Biodegradation of Phenol Using the Indigenous Rhodococcus pyridinivorans Strain PDB9T NS-1 Immobilized in Calcium Alginate Beads.

Phenolic compounds are the major contaminants identified from various industrial effluents, which pose an extreme threat to the environment. Therefore, investigating an effective technique to remove these toxic phenolic compounds from the contaminated environment is very essential. In the present investigation, batch tests were performed to assess the biodegradation of phenol using an indigenous Rhodococcus pyridinivorans strain PDB9T NS-1 encapsulated in a calcium alginate bead system. In order to improve the mechanical stability, silica was added to the cell-embedded Ca-alginate beads. The impact of experimental conditions such as contact time, pH, and initial phenol doses was investigated. The biodegradation of phenol was examined over a wide range of phenol, and the results showed that more than 99.6% degradation was achieved at an initial phenol dose of 1000 mg/L in 70 h at 30 °C. Among the various sorption isotherm tested, the Freundlich isotherm was the best fitted to the experimental data. This behavior indicated a multilayer biosorption process and was controlled by heterogeneous surface energy. Based on an intra-particle diffusion model, internal mass transfer or pore diffusion predominated over exterior mass transfer in controlling the entire phenol biosorption process. The biosorption of phenol onto the cell encapsulated in the Ca-alginate bead follows pseudo-first-order kinetics with a superior phenol biosorption capacity of 155 mg/g of Ca-alginate. Further stability study revealed that the bead could be recycled successfully without any substantial decline in phenol degradation efficiency, indicating that the immobilized microbe possesses exceptional operating stability.

The Journey from Porous Materials to Metal-organic Frameworks and their Catalytic Applications: A Review.

Metal-Organic Frameworks (MOFs), a class of inorganic-organic hybrid materials, have been at the center of material science for the past three decades. They are synthesized by metal ions and organic linker precursors and have become very potential materials for different applications ranging from sensing, separation, catalytic behaviour to biomedical applications and drug delivery, owing to their structural flexibility, porosity and functionality. They are also very promising in heterogeneous catalysis for various industrial applications. These catalysts can be easily synthesized with extremely high surface areas, tunable pore sizes, and incorporation of catalytic centers via post-synthetic modification (PSM) or exchange of their components as compared to traditional heterogeneous catalysts, which is the preliminary requirement of a better catalyst. Here, in this review, we have presented the history of MOFs, different synthesis procedures, and MOFcatalysed reactions; for instance, coupling reactions, condensation reactions, Friedel-Crafts reaction, oxidation, etc. Special attention has been given to MOFs containing different catalytic centers, including open metal sites, incorporation of catalytic centers through PSM, and bifunctional acidbase sites. The important role of catalytic centers present in MOFs and reaction mechanisms have also been outlined with examples.

Role of Additives in Electrochemical Deposition of Ternary Metal Oxide Microspheres for Supercapacitor Applications.

A simple two-step approach has been employed to synthesize a cobalt-nickel-copper ternary metal oxide, involving electrochemical precipitation/deposition followed by calcination. The ternary metal hydroxide gets precipitated/deposited from a nitrate bath at the cathode in the catholyte chamber of a two-compartment diaphragm cell at room temperature having a pH ≈ 3. The microstructure of the ternary hydroxides was modified in situ by two different surfactants such as cetyltrimethylammonium bromide and dodecyltrimethylammonium bromide in the bath aiming for enhanced storage performance in the electrochemical devices. The effect of the surfactant produces a transition from microspheres to nanosheets, and the effect of micelle concentration produces nanospheres at a higher ion concentration. The ternary hydroxides were calcined at 300 °C to obtain the desired ternary mixed oxide materials as the electrode for hybrid supercapacitors. X-ray diffraction analysis confirmed the formation of the ternary metal oxide product. The scanning electron microscopy images associated with energy-dispersive analysis suggest the formation of a nanostructured porous composite. Ternary metal oxide in the absence and presence of a surfactant served as the cathode and activated carbon served as the anode for supercapacitor application. DTAB-added metal oxide showed 95.1% capacitance retention after 1000 cycles, achieving 188 F/g at a current density of 0.1 A/g, and thereafter stable until 5000 cycles, inferring that more transition metals in the oxide along with suitable surfactants at an appropriate micellar concentration may be better for redox reactions and achieving higher electrical conductivity and smaller charge transfer resistance. The role of various metal cations and surfactants as additives in the electrolytic bath has been discussed.

Probing the electrochemical properties of biopolymer modified EMD nanoflakes through electrodeposition for high performance alkaline batteries.

In the present work, a novel biopolymer approach has been made to electrodeposit manganese dioxide from manganese sulphate in a sulphuric acid bath containing chitosan in the absence and presence of glutaraldehyde as a cross-linking agent. Galvanostatically synthesised electrolytic manganese dioxide (EMD) nanoflakes were used as electrode materials and their electrochemical properties with the influence of biopolymer chitosan were systematically characterized. The structural determination, surface morphology and porosity of nanostructured EMD were evaluated using X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy and nitrogen adsorption-desorption techniques. The results obtained were compared with that of blank EMD (polymer free). The results indicated that the EMD having chitosan cross-linked with glutaraldehyde possesses a reduced particle size and more porous structure than the blank and EMDs synthesized in the presence of chitosan but without glutaraldehyde. The results revealed that chitosan was unable to play any significant role on its own but chitosan in the presence of glutaraldehyde forms a cross-linking structure, which in turn influences the nucleation and growth of the EMDs during electrodeposition. EMDs obtained in the presence of chitosan (1 g dm(-3)) and glutaraldehyde (1% glutaraldehyde) exhibited a reversible and better discharge capacity upon cycling than the blank which showed its typical capacity fading behaviour with cycling. In addition, EMD synthesized in the presence of 1 g dm(-3) chitosan and 2% glutaraldehyde exhibited a superior electrochemical performance than the blank and lower amounts (1%; 1.5%) of glutaraldehyde, showing a stable discharge capacity of 60 mA h g(-1) recorded up to 40 cycles in alkaline KOH electrolyte for a Zn-MnO2 system. Our results demonstrate the potential of using polymer modified EMDs as a new generation of alkaline battery materials. The XPS data show that a surface functional moiety arising from the cross-linked chitosan enhances the electrochemical properties of the Zn-MnO2 system.