Kinetic Rate Model Research Articles

A facile synthesis of ternary hybrid nanocomposite of WS2/ZnO/PPy: An efficient photocatalyst for the degradation of chromium hexavalent

In this study novel and promising ternary hybrid nanocomposite of tungsten disulphide (WS2), zinc oxide (ZnO) and polypyrrole (PPy) has been synthesized for the efficacious photocatalytic reduction of hexavalent chromium (Cr(VI)). This ternary hybrid nanocomposite was prepared using the hydrothermal and in situ oxidative polymerization method. The crystal structures, physicochemical and optical features of the prepared nanocomposite were examined using various characterization techniques such as XRD, FTIR, and UV–Vis spectroscopy. The synthesized nanocomposite contains the morphologies of pristine samples such as nanosheets, nanorods and nanoparticles of WS2, ZnO and PPy, respectively as demonstrated from FESEM images. The adsorption and photocatalytic degradation studies were performed as a function of concentrations of Cr (VI). The synthesized nanocomposite shows enhanced degradation efficiency (81.82%–94.66%) from pristine samples (1.81–4.85% for WS2, 29.09–36.36% for ZnO and 45.55–48.94% for PPy) towards 10 mg/L concentration of Cr(VI) under dark and light conditions, respectively. This enhanced degradation efficiency was attributed to the large surface area, lower recombination rate for photogenerated species, superior absorption for light and generation of free radicals under dark and light conditions as explained by TCSPC decay, tauc's plot (2.28 eV) and EPR measurements, respectively. EPR and scavenger study both supports for the formation of free radicals (•O2−) and (.OH) in light and dark both conditions. The value of g-factor comes out to be 2.01 from EPR study. The kinetic study illustrates that the photocatalytic degradation of Cr(VI) by the prepared ternary nanocomposite followed pseudo-second-order rate kinetics model and Langmuir adsorption isotherm. These models proposed that the removal of Cr(VI) was take place through both physisorption and chemisorption processes. The degradation mechanism was analyzed with the help of Mott-Schottky/scavenger studies, and revealed that the superoxide radicals (•O2−) were the primary active species. The reusability experiment demonstrates that the prepared nanocomposite can be reused up to 5 times with almost the same efficiency in all cycles and hence, can be considered as a promising candidate for wastewater treatment.

Synthesis and characterization of nanostructured ternary composites of graphene oxide/Fe3O4/NiO for waste water treatment

Photocatalysis using solar energy and semiconductors is widely used in the purification of air and the processing of wastewater. Present study deal with cost-effective GO synthesis, supporting NiO/Fe3O4 ternary nanocomposites; for the rapid photocatalytic degradation of the Rhodamine B Dye. For this purpose, nickel oxide nanoparticles and iron oxide nanoparticles were synthesized by hydrothermal method. Synthesis of graphene oxide was done by using modified hummers method. These trimetallic nanoparticles were characterized by FTIR (Fourier Transform Infrared Spectroscopy), Scanning Electron Microscopy (SEM) and X-ray Diffraction Crystallography (XRD) for structure, shape and composition determination. The photocatalytic degradation of Rhodamine B dye was conducted and various parameters like catalyst amount, dye concentration, pH and contact time optimization were performed to evaluate dye degradation efficiency of Fe3O4/NiO/Graphene trimetallic nanoparticles. Kinetic models were studied to check degradation rate and Pseudo 1st order kinetic model was most suitable to the experimental data of dye degradation.

Kinetics-based fatigue damage investigation of asphalt mixture through residual strain analysis using indirect tensile fatigue test

Fatigue damage, one of the major distresses of asphalt pavement, has been found to have a phenomenological correlation with the accumulated residual strain (RS) of the asphalt mixture tested by stress-controlled fatigue test with excessive creep. However, it remains a challenge to quantitatively model such phenomenological correlation. This study aims to address this challenge by applying the kinetics theory to the indirect tensile fatigue test (ITFT) with excessive creep data of various asphalt mixtures. First, ITFTs of asphalt mixtures under different conditions were conducted to analyze the RS response. Then, the RS kinetics model was established based on the fast-constant rate kinetics model. Finally, two of the kinetics model parameters, the RS constant rate (kc) and activation energy, were successfully applied to characterize the fatigue life (Nf) and the fatigue damage resistance of the asphalt mixture, respectively. It was found that the established RS kinetics model can accurately describe the development of the accumulated RS determined by ITFT. The kc determined by ITFT is an effective indicator for the rate of the initial damage evolving to the failure threshold. The established kc-based fatigue equation can be used to predict the Nf of the asphalt mixture tested by ITFT from kc. The RS accumulation activation energy can effectively characterize the fatigue damage resistance of the asphalt mixture tested by ITFT.

Magnetite incorporated amine-functional SiO2 support for bimetallic Cu-Ni alloy nanoparticles produced highly effective nanocatalyst

In this article, inclusion of iron oxide (Fe3O4) in amine functional silica (SiO2-NH2) support is attempted to see any improvement in catalytic property for anchored bimetallic Cu-Ni alloy nanoparticles. The Fe3O4-SiO2-NH2 support is first prepared by one-step solvothermal route. Secondly, bimetallic Cu-Ni alloy nanoparticles are generated on the Fe3O4-SiO2-NH2 support via in-situ simultaneous sorption and reduction of Cu and Ni ions. The resulting product, named as Fe3O4-SiO2-NH2/Cu-Ni nanocatalyst, contained face-centered-cubic (fcc) bimetallic Cu-Ni alloy with average crystallite size of 4.76 nm and possessed strong paramagnetic character (27.76 emu g−1). The Fe3O4-SiO2-NH2/Cu-Ni nanocatalyst showed faster reduction kinetics for the conversion of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) compared to both unsupported Cu-Ni and supported SiO2-NH2/Cu-Ni nanocatalysts. The Fe3O4-SiO2-NH2/Cu-Ni nanocatalyst is recoverable magnetically and reused up to 6th cycle without any drop in activity, producing 100% conversion at pH 6. The reduction reaction preferably followed the pseudo-first-order kinetic rate model. Overall, the catalytic activity and recycle stability of bimetallic Cu-Ni nanocatalyst enhanced dramatically following the use of magnetic Fe3O4-SiO2-NH2 composite support. Additionally, the prepared Fe3O4-SiO2-NH2/Cu-Ni nanocatalyst possessed good application potential as antibacterial agent due to the presence of Cu-Ni.

Synthesis of ecological chitosan/PVP magnetic composite: Remediation of amoxicillin trihydrate from its aqueous solution, isotherm modelling, thermodynamic, and kinetic studies

The simple co-precipitation technique was followed to prepare an eco-friendly Chitosan/Polyvinylpyrrolidone magnetic composite in different ratios (CPF37, CPF55, CPF73) to exterminate Amoxicillin trihydrate (AMXT) from its aqueous environment. The batch method was practised to study the different parameters affecting the adsorption procedure. Among the three, CPF37 was found to be the best adsorbent for our study, owing to its highest adsorption capacity. The synthesized material was characterized using standard analytical techniques like FT-IR spectroscopy, XRD, SEM-EDX, TEM, VSM, TG-DTA, DSC, and Zeta-seizer. Furthermore, the efficiency of CPF37 reached up to 93% at pH 8 with 1 g/L optimized dosage for 100 mg/L AMXT solution at 308 K. The isotherm data attributed to multilayer adsorption, Freundlich isotherm (R2 = 0.9929) at 308 K and Qmax was calculated as 73.52 mg/g. The results from Kinetic studies concluded that the reaction followed pseudo-second order rate kinetic model, while the mechanism being the combination of several forces at a time. Moreover, Thermodynamic studies revealed the process to be endothermic (ΔH = +25.38 KJ/mol) and spontaneous (ΔG = −2.390 KJ/mol at 308 K).

Nonequilibrium Dissociation and Recombination Models for Hypersonic Flows

A recombination reaction model for high-temperature chemical kinetics is analytically derived from ab initio simulation data. When atoms recombine, the kinetic rate model shows that product molecules favor high vibrational energy states. In this manner, recombination repopulates high vibrational energy states depleted by dissociation, in a high-temperature reacting gas. Coupling of internal energy relaxation, dissociation, and recombination results in depleted or overpopulated (relative to a corresponding Boltzmann distribution) vibrational energy distributions. Through a simple model, we show that non-Boltzmann behavior, in other words, depletion or overpopulation of high-energy states, is not only linked to thermal nonequilibrium but also chemical nonequilibrium. The mathematical derivation also indicates that the conventional approach for modeling recombination rates, where shock-tube dissociation rate measurements are combined with the principle of detailed balance, is incorrect. The complete analytical dissociation/recombination model embeds all relevant kinetic processes, including specific terms for translation/rotation/vibration/chemistry coupling, anharmonic and quasi-bound effects, and non-Boltzmann depletion and overpopulation effects. The model is a multitemperature model that can be used within computational fluid dynamics simulations with no appreciable increase in computational expense. Finally, because the model is analytical, containing separate terms for various physical effects, further model simplification could be performed depending on the flow conditions of interest.

Heterogeneous numerical modelling for the auto thermal reforming of crude glycerol in a fixed bed reactor

A mathematical model for the catalytic autothermal reforming (ATR) reaction of synthetic crude glycerol to hydrogen in a fixed bed tubular reactor (FBTR) and over an in-house developed metal oxide catalyst is presented in this work. The heterogeneous model equations account for a two-phase system of solid catalyst and bulk feed gas. Also, the ATR of crude glycerol reaction scheme and intrinsic kinetic rate model over an active, selective, and stable nickel-based catalyst were integrated in the developed model. Also, the model was validated using experimental data generated in our labs for the ATR of synthetic crude glycerol. The modelling results adequately described the detailed gas product composition and distribution, temperature profiles, and conversion propagation in the axial direction of the fixed bed reactor over a wide range of reaction temperature (773–923 K) and mass-time (12.71–158.23 g cat·min·(mol C) −1 ). The crude glycerol conversion predicted with the model showing a close resemblance to those obtained experimentally with an average absolute deviation (AAD) of less than 8%. The maximum crude glycerol conversion and hydrogen yield were found to be 92% and 3 mol hydrogen/mol crude glycerol, respectively. Also, the gas product concentration profile in the reactor was adequately described (90%) accuracy with a hydrogen concentration of 39 vol%.

Overall Rate Kinetics Model for Chlorine Demand of Urban Rainfall Runoff

The built environment significantly alters the rainfall-runoff response and associated transport of particulate matter (PM), chemicals, and pathogens in the urban water cycle. Urban water sustainability requires mitigation of runoff impacts while providing a potential resource to traditional water supply sources. Chlorination for wastewater, combined sewer overflows (CSOs), and reuse waters is the most common disinfection practice to ensure public health. Chlorinated wastewater effluent is a common reclaimed water for reuse applications such irrigation and mixing with source-area runoff during wet-weather events. Chlorine demand models have been developed for source waters and wastewaters. The current study adds to this knowledge base through modeling of sodium hypochlorite demand kinetics for source-area runoff PM and also dissolved phases utilizing dissolved chemical oxygen demand (CODd). Second-order rate models of hypochlorite demand are developed for both phases, with the PM phase subdivided into three fractions on a granulometric basis. PM (suspended, settleable, and sediment) fractions exert a significant hypochlorite demand compared with the dissolved fraction. Ultimate chlorine demand translates to 36% of the CODd, of which 39% of the demand is exerted in less than 5 min, which is in the range of residence times for small manufactured unit operations that are common for best management practices (BMPs). Chlorine demand is 350 mg/g for suspended, 320 mg/g for settleable, and 650 mg/g for sediment PM.

Structural and Optical Characterizations of Cadmium Chalcogenide Layers on Polyamide Formed Using Monotelluropentathionic Acid.

Mixed cadmium tellurides–cadmium sulfide thin layers were formed on the polyamide PA 6. Monotelluropentathionic acid (H2TeS4O6) was used as a precursor of tellurium and sulfur. A low-temperature, nontoxic, and cost-effective SILAR method was applied. Cadmium telluride (CdTe) and sulfide (CdS) layers were formed through the consecutive reactions of sorbed/diffused chalcogens species from telluropentathionate anion (TeS4O62−) with functional groups of polyamide and alkaline cadmium sulfate. The pseudo-second-order rate and Elovich kinetic models were the best fit to quantify an uptake of chalcogens and cadmium on PA 6. The effects of chalcogens and Cd on the structure and optical properties of PA 6 were characterized using UV-Vis and IR spectra. The clear changes of these properties depended on the concentration and exposure time in the precursor solutions. Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy were applied in order to evaluate the effect of the chalcogen species on the changes in structure of polyamide 6 films, depending on the exposure time in the solution of the chalcogens precursor and its concentration. The optical bandgap energy of the formed layers was found to be in the order of 1.52–2.36 eV. Studies by scanning electron microscopy and atomic force microscopy reveal that the diameter of the average grain is approximately 30 nm. The grains are conical in shape and unevenly distributed all over the surface of the substrate.

Kinetic modeling of removal of aromatic hydrocarbons from petroleum wastewaters by UiO-66-NH2/TiO2/ZnO nanocomposite

In this study, the UiO66-NH2/TiO2/ZnO (UTZ) nanocomposite was synthesized using the sol-gel method. The mean particle size of UTZ nanocomposite was about 33.63 nm. The present work investigates the applicability of a photocatalytic oxidation process for benzene, toluene and xylene (BTX) degradation. The response surface modeling (RSM) was utilized to optimize important parameters, i.e. catalyst content (g/L), lamp power (W), initial contaminant concentrations and pH. The optimized values of these parameters involved UTZ concentration of 0.11 g/L, lamp power of 15 W, the initial pollutant concentration of 50 ppm and pH= 7. The BTX degradation and total organic carbon (TOC) removal efficiencies were 90.03% and 85.16%, respectively, under optimal conditions. Ultimately, a new kinetic reaction rate model was developed in the form of Langmuir- Hinshelwood equation based on the intrinsic-element reactions in the form of−r=0.102I0.5[UTZ]0.5[BTX]/1+1.9298[BTX]0+1.6059I0.5[UTZ]0.5. The first-order kinetic constant determined by this model was 0.133 min-1. It was observed that the model for the photocatalysis reaction rate was well fitted with the experimental data at minimal mean absolute relative residual (14.18%).

Symbiotically Augmented removal of Congo red by polyaniline/cobalt sulfide/graphite composites

The presence of Congo red dye (CR) in industrial sewage causes a serious threat to the environment. Therefore, it is imperative to develop high-performance, low-cost functional materials to mitigate such issues. During past decades, polyaniline and its composites have been recognized as an emerging candidate to remove hazardous organic effluents from water. The present work demonstrates the successful elimination of CR from water in presence of newly synthesized graphite/cobalt sulfide/PANI-based ternary composites. Several morphological or physicochemical characterization tools were adopted to confirm the formation of the ternary composite and subsequent synergistic interaction between individual elements of the composites. The experimental results delineate that a maximum of ∼95.55% CR removal (%) was achieved after 120 min. Fast removal (∼5–10 min) of CR dye is observed for APS/Ternary composite system. From the fitted experimental data utilizing 1st or 2nd order rate kinetic models, it was observed that the adsorption induced degradation of CR dye and the process was chemisorptions in nature. Further, an intra-molecular diffusion model was also introduced that signifies both boundary layer diffusion or intraparticle diffusion phenomenon was responsible for CR removal. Furthermore, the cytotoxicity profile of the composite treated Congo red aqueous solution was evaluated when exposed to L929 fibroblast cells after 24 h or 72 h of exposure and the result deciphers the non-toxic nature of composite treated CR water.

Optimization of Pb(II) removal by a novel modified silica aerogel using Quince seed mucilage with response surface methodology

The synthesis of new environmentally friendly and biocompatible material is an exciting research field to remove various pollutants from water/wastewater samples. The main objective of this paper is the successful synthesis of an Eco-friendly and novel modified silica aerogel (NMSA) by adding a small amount of Quince seed mucilage (QSM, 0.05 wt%) to water glass precursor and an ambient pressure drying method. The prepared NMSA was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and N2 adsorption/desorption isotherms. Results showed that adding a small amount of QSM to the precursor causes the formation of relatively uniform nanoparticles with an approximate size of 20 nm. The synthesized NMSA was then used for Pb(II) removal from an aqueous solution. Pb(II) adsorption in NMSA was about 30% more than raw Silica aerogel (SA). After performing some preliminary experiments and confirming the excellent efficiency of the NMSA in Pb(II) removal, RSM (response surface methodology) study via a central composite design (CCD) optimization approach was made to study the effects of the interaction of the influencing variables on the adsorption efficiency. The maximum Pb(II)-removal efficiency of 75% was achieved for the optimized run with conditions of pH: 4, contact time: 62 min, NMSA dosage: 1.4 g/L, and initial Pb(II) concentration: 50 mg/L. The Pb(II) removal by the modified NMSA adsorbent well obeyed the Langmuir isotherm and a pseudo-second-order rate kinetics model.

Development of a kinetic reaction model for reduction and oxidation of Si doped Mn2O3 for thermochemical energy storage in concentrated solar power plants

Thermal energy storage plays a significant role in concentrated solar power plants. Particularly, thermochemical energy storage has been proposed as a promising future candidate due to its high energy density. One of the most studied thermochemical reactions are metal oxides redox reactions. The simplicity of using air as both heat transfer fluid and reactant provides important advantages. Among the studied materials, Mn2O3 has been deeply investigated due to its low cost and toxicity, although its reversibility has been shown to be highly deteriorated when exposed to high temperatures. Doping Mn2O3 with 1 at% of Si counteracted this weakness leading to a promising candidate for energy storage. In this work, thermogravimetric analysis of (Mn0.99Si0.01)2O3 demonstrated no significant changes in enthalpy compared to Mn2O3, while the oxidation kinetics and mostly, its cycling stability experienced great improvements. In order to provide tools for future thermochemical reactor design, a complete study of the reduction and oxidation kinetics of (Mn0.99Si0.01)2O3 in a thermobalance was carried out, obtaining satisfactory kinetic parametrization models. Both processes are mainly controlled by nucleation and growth mechanisms, although the diffusion mechanism prevails at high conversion extents (α > 0.8). In order to mimic accurately the effect of the oxygen partial pressure on the reaction kinetics, significant in the case of the oxidation reaction, the developed model includes an innovative contribution. The so called ‘isoconversional activation energy’ was introduced in the model, turning into an accurate prediction tool able to simulate the material kinetics deceleration within the hysteresis zone, providing a reaction rate kinetic model with extended range which has not been provided before.

Deactivation behaviour of intermetallic Ga‐Ni catalyst in CO2 hydrogenation to methanol

AbstractThe chemical conversion of greenhouse gas CO2 to environmentally benign compounds, especially alternative fuels like methanol, is an inevitable solution to the global warming problem. The intermetallic catalysts exhibit superior catalytic activity compared to the monometallic ones but suffer from loss of activity during the reaction. Herein, we report the influence of the preparation method on the deactivation behaviour of Ga3Ni5 catalyst in CO2 hydrogenation to methanol. The Ga3Ni5 catalyst was prepared through three different methods. The spent catalysts from the reactor were characterized by X‐ray diffraction, transmission electron microscopy‐energy dispersive X‐ray spectroscopy (TEM‐EDX), Brunaue‐Emmett‐Teller (BET), H2‐pulse chemisorption, and Fourier‐transform infrared spectroscopy (FTIR) technique to evaluate the cause and nature of deactivation. After 250 hr of CO2 hydrogenation, all catalysts had lost about 50% of their initial activity due to the erosion of active sites. The nanoparticle dispersion was found to increase in the order Ga3Ni5‐CE< Ga3Ni5‐IWI < Ga3Ni5‐CP. The activity of catalysts during methanol synthesis (at 473 K, 20 bar) initially depicted a similar trend. However, the selectivity to methanol remained comparatively high for the catalysts prepared by the co‐precipitation method. The loss of activity in Ga3Ni5 catalysts was mainly attributed to the metal sintering and a lesser extent, by coke deposition. The kinetics of deactivation was studied based on the normalized dispersion, and the deactivation rate constant was estimated using the power‐law kinetic rate model. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

Multiscale study of poly(butylene terephthalate) hydrolysis

This paper reports the hydrolysis of several PBT materials (pigmented or not). Degradation was monitored by gel permeation chromatography (chain scission), DSC (crystalline morphology), tensile test (residual mechanical properties) and DVS (polymer-water interaction). The embrittlement comes from chain scission associated with a small chemicrystallization effect. Results lead to the proposal of a kinetic model for the chain scission rate aimed to describe the auto-acceleration effect induced by carboxylic acids (chain ends) and successfully compared to results both from this work or literature. The mixed “average molar mass – crystallinity” criterion proposed in a previous paper was specified. At last, the effect of pigments is illustrated and shows that carbon black (present in particular in one masterbatch) plays an aggravating role on hydrolysis.

Quasi-equilibrium phase coexistence in single component supercritical fluids

In their supercritical state simple fluids are generally thought to assume a homogeneous phase throughout all combinations of pressures and temperatures, although various response functions or transport properties may exhibit anomalous behavior, characterizing a state point as either more gas-like or liquid-like, respectively. While a large body of results has been compiled in the last two decades regarding the details of the supercritical phase in thermodynamic equilibrium, far less studies have been dedicated to out-of-equilibrium situations that nevertheless occur along with the handling of substances such as carbon dioxide or Argon. Here we consider successive compression-expansion cycles of equal amounts of Argon injected into a high-pressure chamber, traversing the critical pressure at two times the critical temperature. Due to expansion cooling, the fluid temporarily becomes sub-critical, and light scattering experiments show the formation of sub-micron-sized droplets and nanometer-scale clusters, both of which are distinct from spontaneous density fluctuations of the supercritical background and persist for a surprisingly long time. A kinetic rate model of the exchange of liquid droplets with the smaller clusters can explain this behavior. Our results indicate non-equilibrium aspects of supercritical fluids that may prove important for their processing in industrial applications.

Toluene Bioremediation by Using Geotextile-Layered Permeable Reactive Barriers (PRBs)

Sources of contamination in a subsurface environment are petrol, diesel fuel, gasoline at oil refineries, underground storage tanks, transmission pipelines, and different industries. The permeable reactive barrier (PRB) is a promising technology to remediate groundwater in-situ. In this study, synthetic groundwater samples containing toluene are treated in three reactor columns by biological processes. PRB-1 consisted of sand and gravel as reactor media, microbial inoculum (bioaugmentation—BA), and nutrients (biostimulation—BS); PRB-2 consisted of sand and gravel as reactor media, microbial inoculum, nutrients, and 12 layers of nonwoven geotextile fabrics; and PRB-3 consisted of only sand and gravel as reactor media (natural attenuation—NA). This study was conducted to assess the impact of geotextile fabric filter, bioaugmentation, and biostimulation on toluene degradation efficiency. After 167 days of treatment, toluene biodegradation efficiencies varied between 88.2% and 93.8% for PRB 1, between 98.0% and 99.3% for PRB 2, and between 14.2% and 68.6% for PRB 3. The effluent toluene concentrations for PRB-2 were less than the guideline value (0.7 mg/L) of the World Health Organization. Reaction rate data were fitted with a first-order kinetic reaction rate model. This study showed that the toluene removal efficiency in the geotextile layered PRB combined with BA and BS process was significantly higher compared to the other processes tested. This lab-scale study introduced a new PRB configuration suitable for the remediation of sites contaminated with toluene.

Adsorption of nickel ions from electroplating effluent by graphene oxide and reduced graphene oxide

Heavy metal pollution in the water bodies causes a serious threat to all living beings. Extended exposure of heavy metals such as nickel (Ni) ions causes cancer. Henceforth, the current study investigated the removal of Ni ions from the electroplating effluent using nanocomposites namely, Graphene Oxide (GO) and Reduced Graphene Oxide (rGO) in the presence of various factors such as contact time, pH, agitation speed and sorbent dosage. Further, it was determined the rate kinetic model and adsorption equilibrium isotherms. The study also focused on comparing the removal efficiency of two nanocomposites. The maximum sorption efficiency were found to be 90.8% and 84.4% at optimized pH (8), contact time (180–1440 m), RPM (250–300) and adsorbent dosage (0.2 mg/L) for GO and rGO respectively. Furthermore, toxicity of treated and untreated effluent were tested against Phosphobacter and Azospirillium using GO and rGO and found that the treated effluent was non-toxic. The contribution of this study to agriculture in using recycled effluent for crop cultivation was being verified by seed germination of Lablab purpureus seeds watered with treated and untreated effluent. Finally we concluded that the results of treated water can be used for cultivation as there was healthy growth of plants.

Waste Fiber-Based Poly(hydroxamic acid) Ligand for Toxic Metals Removal from Industrial Wastewater.

Toxic metals in the industrial wastewaters have been liable for drastic pollution hence a powerful and economical treatment technology is needed for water purification. For this reason, some pure cellulosic materials were derived from waste fiber to obtain an economical adsorbent for wastewater treatment. Conversion of cellulose into grafting materials such as poly(methyl acrylate)-grafted cellulose was performed by free radical grafting process. Consequently, poly(hydroxamic acid) ligand was produced from the grafted cellulose. The intermediate products and poly(hydroxamic acid) ligand were analyzed by FT-IR, FE-SEM, TEM, EDX, and XPS spectroscopy. The adsorption capacity (qe) of some toxic metals ions by the polymer ligand was found to be excellent, e.g., copper capacity (qe) was 346.7 mg·g−1 at pH 6. On the other hand, several metal ions such as cobalt chromium and nickel also demonstrated noteworthy sorption capacity at pH 6. The adsorption mechanism obeyed the pseudo second-order rate kinetic model due to the satisfactory correlated experimental sorption values (qe). Langmuir model isotherm study showed the significant correlation coefficient with all metal ions (R2 > 0.99), indicating that the single or monolayer adsorption was the dominant mode on the surface of the adsorbent. This polymer ligand showed good properties on reusability. The result shows that the adsorbent may be recycled for 6 cycles without any dropping of starting sorption capabilities. This polymeric ligand showed outstanding toxic metals removal magnitude, up to 90–99% of toxic metal ions can be removed from industrial wastewater.

Rapid selective removal of thorium via electrosorption towards efficiently managing rare-earth extraction residue

In this present study, thorium ion [Th(SO4)32-] was removed from aqueous sulphate medium using fabricated activated carbon-based electrodes (CBE). The thermal cross-linking technique was used to synthesize the CBE. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) technique, X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FESEM) were used to characterize the CBE adsorbent. The adsorptive characteristics were investigated through batch static adsorption experiments by varying the concentration, time and applied voltage. The adsorption statistics were justified by isotherm and kinetic models. The Langmuir and Freundlich adsorption model was revealed to be fitted, with a maximum adsorption capacity of 8.4 mg-Th/ g-Carbon. The electrosorption of [Th(SO4)32-] onto the CBE followed the pseudo-first and second-order kinetic rate models. Through FESEM, XRD and XPS characterization studies, a suitable mechanism for thorium sorption has been postulated.