Values Of Thermodynamic Parameters Research Articles

Statistical evaluation of cow-dung derived activated biochar for phenol adsorption: Adsorption isotherms, kinetics, and thermodynamic studies

Sustainable and economical wastewater treatment forms a vital step towards long-term sustainability of petrochemical refineries and industries. An affordable solution to this challenge is to employ biowaste as the key consumable active component. This paper describes the synthesis and characterization of activated biochar derived from cow-dung, a readily available raw material in low-resource settings, and its application for adsorption of phenol, one of the major pollutants in industrial wastewater. Adsorption parameters are optimized by using response surface methodology. Phenol adsorption equilibrium and kinetics data are well fitted to Freundlich isotherm (R2 = 0.97) and pseudo-second-order model (R2 = 0.99), respectively. The maximal adsorption capacity (518.89 mg/g) was attained using the Langmuir isotherm model at pH 6.0. Negative values of thermodynamic parameters confirmed the spontaneity, feasibility, and exothermic behaviour of adsorption reaction. The results demonstrate that synthesized activated biochar showed an excellent phenol adsorption capacity of 98.8 %.

Antimicrobial nanocomposite adsorbent based on poly(meta-phenylenediamine) for remediation of lead (II) from water medium

In this study, poly(m-phenylenediamine)@ZnO (PmPDA@ZnO) nanocomposite was fabricated by in-situ chemical oxidative polymerization for the effective lead(II) removal from aqueous solutions. PmPDA@ZnO was characterized by several instrumental methods like FTIR, XRD, EDX, TGA, FESEM, TEM, zeta potential, and BET. The TEM images showed a core–shell-like structure for the PmPDA@ZnO nanocomposite. TGA results showed that the thermal stability of the PmPDA@ZnO nanocomposite was higher than the PmPDA. The maximum adsorption of lead (II) onto PmPDA@ZnO nanocomposite was obtained at pH 6, adsorbent dosage 60 mg, lead(II) ion concentration 90 mg/L, and agitation time 90 min. Langmuir and Freundlich's isotherm models were evaluated to simulate the lead(II) sorption via empirical data. Langmuir's model was in good agreement with empirical data with a maximum adsorption capacity (Qmax) of 77.51 mg/g. The kinetic data adsorption fitted best the pseudo-second-order model. The values of thermodynamic parameters of ΔS° and ΔH° were obtained 0.272 J/mol K, and 71.35 kJ/mol, respectively. The spontaneous and endothermic behavior of the adsorption process was confirmed by the negative and positive response of ΔG° and ΔH°, respectively. Moreover, the addition of coexisting cations e.g. cobalt (II), nickel (II), calcium (II), and copper (II) had no significant effect on the removal efficiency of lead(II). Adsorption–desorption studies showed that the PmPDA@ZnO nanocomposite can be remarkably regenerated and reused after three sequential runs without a significant decline in its adsorption performance. The antimicrobial activities of PmPDA@ZnO nanocomposite were evaluated against Escherichia coli and Staphylococcus aureus bacteria species. These results confirmed that the PmPDA@ZnO nanocomposite could be a good candidate for water decontamination.

Preparation, characterization, and application of modified magnetic biochar for the removal of benzotriazole: process optimization, isotherm and kinetic studies, and adsorbent regeneration.

The adsorption of benzotriazole (BTA) by chemically modified magnetic biochar (MMBC) as a cheap and abundant biosorbent was investigated and optimized using response surface methodology (RSM). Initially, the MMBC composite was synthesized and characterized by scanning electron microscopy (SEM) energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and Brunauer-Emmett-Teller (BET) techniques. The characterization results confirmed the existence of Fe3O4 in the composite structure, which had uniformly dispersed over biochar (BC) with porous texture. Moreover, the presence of Zn and Cl elements in EDX analysis indicated that the magnetic biochar (MBC) had been modified successfully. The effects of chemical modification methods on the adsorption capacity of magnetic biochar were investigated. Maximum BTA removal efficiency was demonstrated by MMBC, modifying using ZnCl2 (>99%). Optimization was carried out based on reaction time, BTA concentration and the concentration of adsorbent. Optimum experimental conditions for the removal of BTA from aqueous solutions were found to be 35 min of reaction time, 0.55 g/L of adsorbent, and 50 mg/L of initial BTA concentration. At these optimal conditions, the predicted BTA adsorption efficiency was 92.6%. The adsorption process followed the Avrami fractional-order reaction kinetic and the Langmuir adsorption isotherm with the maximum adsorption capacity of 563.1 mg/g. The values of thermodynamic parameters demonstrated that the adsorption of BTA on ZnCl2-MBC is endothermic and spontaneous. Under optimum usage of MMBC, the adsorptive removal efficiency of BTA non-significantly decreased from 99.2 to 93.9% after the 5th cycle. Thus, MMBC can be recommended as an environmentally friendly and cost-effective adsorbent to remove micropollutants from water.

Low Error Estimation of Half-Cell Thermodynamic Parameters from Whole-Cell Li-Ion Battery Experiments: Physics-Based Model Formulation, Experimental Demonstration, and an Open Software Tool

Low C-rate charge and discharge experiments, plus complementary differential voltage or differential capacity analysis, are among the most common battery characterization methods. Here, we adapt the multi-species, multi-reaction (MSMR) half-cell thermodynamic model to low C-rate cycling of whole-cell Li-ion batteries. MSMR models for the anode and cathode are coupled through whole-cell charge balances and cell-cycling voltage constraint equations, forming the basis for model-based estimation of MSMR half-cell parameters from whole-cell experimental data. Emergent properties of the whole-cell, like slippage of the anode and cathode lithiation windows, are also computed as cells cycle and degrade. A sequential least-square optimization scheme is used for parameter estimation from low-C cycling data of Samsung 18650 NMC∣C cells. Low-error fits of the open-circuit cell voltage (e.g., under 5 mV mean absolute error for charge or discharge curves) and differential voltage curves for fresh and aged cells are achieved. We explore the features (and limitations) of using literature reference values for the MSMR half-cell thermodynamic parameters (reducing our whole-cell formulation to a 1-degree-of-freedom fit) and demonstrate the benefits of expanding the degrees of freedom by letting the MSMR parameters be tailored to the cell under test, within a constrained neighborhood of the half-cell reference values. Bootstrap analysis is performed on each dataset to show the robustness of our fitting to experimental noise and data sampling over the course of 600 cell cycles. The results show which specific MSMR insertion reactions are most responsible for capacity loss in each half-cell and the collective interactions that lead to whole-cell slippage and changes in useable capacity. Open-source software is made available to easily extend this model-based analysis to other labs and battery chemistries.

Immobilization of Thermomyces lanuginosus lipase via ionic adsorption on superparamagnetic iron oxide nanoparticles: Facile synthesis and improved catalytic performance

The present work describes a simple, rational, and optimized methodology for the immobilization of lipase from Thermomyces lanuginosus (TLL) via ionic adsorption on non-commercial superparamagnetic iron oxide nanoparticles (SPIONs). First, the surface loads of both the enzyme and nanoparticles were evaluated by zeta potential measurements over a wide pH range. In addition, the loading surface of TLL was mapped computationally using the information obtained from the Protein Data Bank (PDB) under three different pH conditions. This information allowed to conduct the directional immobilization of the lipase on the surface of the SPIONs in order to maximize the lipase–SPION interaction and keep the enzyme’s active sites facing the solution. TLL was immobilized at a low ionic strength (5 mmol L–1) on the SPIONs under optimized conditions (sodium acetate buffer, pH 4, 25 °C using an initial enzyme loading of 30 mg per gram of support). Under such conditions, almost full immobilization (99.49% adsorption capacity) was observed. The prepared biocatalyst retained 62.3% of its hydrolytic activity relative to the initial activity of the free lipase. Maximum catalytic efficiency (or acid conversion percentage) of 80% in decyl oleate synthesis performed in a solvent-free system was observed after 12 consecutive cycles of reaction of 180 min each. In addition, the lipase–nanoparticle interaction was also evaluated by fluorescence spectroscopy and the thermodynamic parameter values ΔGo=-25.8kJmol-1, ΔHo=-10.44kJmol-1, and, ΔSo=0.122kJmol-1K-1 were found, which is consistent with the occurrence of predominantly ionic interactions. These results clearly show the promising use of the prepared biocatalyst to catalyze decyl oleate production, an ester with emollient properties, in an eco-friendly process (solvent-free system).

Nitrate adsorption onto surface-modified red mud in batch and fixed-bed column systems: equilibrium, kinetic, and thermodynamic studies.

This research aimed to develop a novel composite as a low-cost adsorbent for the removal of nitrate ion from aqueous solutions. The characterization of this composite (composition of red mud with dimethyldioctadecylammonium bromide (DDAB)) was performed by XRF, XRD, FTIR, and BET analyses. The most influential variables on nitrate adsorption, including contact time, solution acidity, adsorbent amount, and temperature were studied. The maximum amount of nitrate adsorbed onto the prepared adsorbent was obtained at pH 5.5 and contact time 30min. The heterogeneous adsorption occurred during the uptake of nitrate. The results of kinetic study revealed that intra-particle diffusion was the major limitation for nitrate adsorption rate. The values of thermodynamic parameters illustrate the non-spontaneous, associative, and exothermic adsorption process. Increasing the temperature enhances the tendency of the process to non-spontaneously. Research on fixed-bed column has been done under different initial nitrate concentrations. The adsorption capacity of nitrate was increased with an increase in the initial concentration of nitrate. The results of column data were successfully explained using the Thomas and Yoon-Nelson models.

The effect of calcium carbonate content on the zinc quantity-intensity relationship in some soils of Mosul, Irak

The quantity-intensity relationship (Q/I) was used to evaluate thermodynamic parameters of zinc in soils under different agricultural management. Ten soil samples were collected from Mosul city to study zinc distribution of calcium carbonate content in these soils. Generally, Q/I relationship of zinc may provide an index for the strength and quantity of effective zinc supply to plants in soils. The Q/I parameters of zinc were studied to quantify zinc release before and after removing carbonates in the studied soils. Results showed that the zinc activity ratio (AReZn) is related to changes with labile zinc (±ΔZn) at equilibrium and increased together with increasing zinc concentrations, intensity (I) ranged between 0.8584 and 0.9972×10-3 mol/L1/2 before removing carbonates and between 0.0909 and 2.7626×10-3 mol/L1/2 after removing carbonates. The ranges of labile Zinc (ZnL) values before and after removing carbonates were between 0.5755-0.7815 and 0.0009-0.0104 cmol/kg, respectively, while the Zinc (PBCZn) before and after removing carbonates fluctuated from 0.5839 to 0.9104 and 0.00112 to 0.00990 cmol/kg(mol/L)−1/2, respectively. That means calcium carbonate increases exchangeable zinc and zinc capacity at equilibrium conditions. The free energy (−ΔF) ranged between -1.001 and -0.979 kJ/mol before removing carbonates and between -1.319 and -0.841 kJ/mol after removing carbonates. Gapon Selectivity Coefficient (kG) ranged between 0.0193835 and 0.027453 and 0.000045 and 0.00450 (mol/L)1/2 before and after removing carbonates, respectively. Therefore, these results may be used as a reference for zinc soil fertilization, whereas thermodynamic parameters values may be used to predict soil ability to supply available zinc.

Polysaccharides Used in Biosorbents Preparation for Organic Dyes Retaining from Aqueous Media.

Natural polymers can themselves be efficient as materials with biosorptive properties but can also be used to transform microbial biomass into an easy-to-handle form, respectively, into biosorbents, through immobilization. The article aims to study biosorbents based on residual microbial biomass (Saccharomyces pastorianus yeast, separated after the brewing process by centrifugation and dried at 80 °C) immobilized in sodium alginate. The biosorptive properties of this type of biosorbent (spherical particles 2 and 4 mm in diameter) were studied for removal of reactive dye Brilliant Red HE-3B (with concentration in range of 16.88–174.08 mg/L) from aqueous media. The paper aims at three aspects: (i) the physico-chemical characterization of the biosorbent (Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and Fourier Transform Infrared (FTIR) spectra); (ii) the modeling of biosorption data in order to calculate the quantitative characteristic parameters using three equilibrium isotherms (Langmuir, Freundlich, and Dubinin–Radushkevich—DR); and (iii) the evaluation of thermal effect and the possible mechanism of action. The results of the study showed that biosorption capacity evaluated by Langmuir (I) model is 222.22 mg/g (ϕ = 2 mm) and 151.51 mg/g (ϕ = 4 mm) at 30 °C, and the free energy of biosorption (E) is in the range of 8.45–13.608 KJ/mol (from the DR equation). The values of thermodynamic parameters suggested an exothermic process due the negative value of free Gibbs energy (ΔG0 = −9.031 kJ/mol till −3.776 kJ/mol) and enthalpy (about ΔH0 = −87.795 KJ/mol). The obtained results underline our finding that the immobilization in sodium alginate of the residual microbial biomass of Saccharomyces pastorianus led to an efficient biosorbent useful in static operating system in the case of effluents with moderate concentrations of organic dyes.

Morphology-controlled synthesis of gold nanoparticles with chitosan for catalytic reduction of nitrophenol

Gold nanoparticles (AuNPs) were synthesized using chitosan as both reducing agent and stabilizer and characterized by UV–vis spectra and transmission electron microscope (TEM). Synthesized AuNPs were used in the reduction of nitrophenol to aminophenol in the presence of NaBH4. The experimental parameters such as the dosage of catalyst, NaBH4/4-nitrophenol molar ratio, temperature, AuNPs obtained under different synthetic conditions were investigated in detail. The reaction rate constants were calculated through the pseudo-first-order kinetic equation. The results indicated that the morphology of AuNPs was controllable just by adjusting the concentration, molecular weight (MW) and degree of deacetylation (DD) of chitosan. The catalytic activities of as-prepared AuNPs was dependent on their morphology and the nature of the reducing agent and stabilizer. Triangular AuNPs synthesized by 0.1% (w/v) chitosan with low DD (63.1%) showed the highest reaction rate constant 0.7050 min−1, which was followed by spherical and small AuNPs (around 10 nm) synthesized by 0.01% (w/v) chitosan and irregular and large AuNPs with wide size distribution synthesized by 0.3% (w/v) chitosan. The values of thermodynamic parameters including activation energy, enthalpy change, entropy change and Gibbs free energy change for the activation were calculated and revealed that the activation of catalytic process was non-spontaneous and endothermic. A comparative study for the catalytic reduction of three kinds of nitrophenols showed that the catalytic activity order of AuNPs was 3-nitrophenol > 2-nitrophenol > 4-nitrophenol.

End-of-life waste criteria: synthesis and utilization of Mn\u2013Zn ferrite nanoparticles as a superparamagnetic photocatalyst for synergistic wastewater remediation

Dyes are toxic compounds that are widely included in industrial discharge. Their efficient and economical remediation can be explored through Fenton’s oxidation. Mn0.6Zn0.4Fe2O4 nanoparticles are prepared via a simple and efficient co-precipitation technique and its chemical composition is confirmed through X-ray diffraction and its morphology via high-resolution transmission electron microscope. The prepared superparamagnetic photocatalyst based on Mn0.6Zn0.4Fe2O4 is applied for almost complete Synozol Blue dye removal (98% dye removal and 87% COD removal) and the results confirmed that the process is an efficient sustainable technique for the easily magnetically recoverable catalyst. Central composite design analysis was chosen to optimize the parametric conditions of the magnetized Fenton’s variables through 13-level of a quadratic model. The optimized system variables were attained at 39 and 404 mg L−1 for catalyst and H2O2, respectively, at pH 3.0 with model correlation coefficients over than 98%. Recover and reuse are a viable option for ‘close the loop’ waste after final treatment as an ‘end-of-life’ waste potential and high removal efficiency is attained up to the 8th cycle of catalyst reuse. Kinetics of Synozol Blue oxidation fitted through the first-order kinetic model. Finally, the thermodynamic parameters values concluded that the process is non-spontaneous and endothermic in nature.

Double-layer modelling and physicochemical parameters interpretation for chromium adsorption on ZnMnOAC nanocomposite

An efficient ZnMnO nanocomposite-based activated carbon (AC) was synthesized using the co-precipitation technique and was characterized by XRD, FTIR, FE-SEM and EDAX spectroscopic methods. The as-synthesized nanocomposite-based activated carbon was applied for the adsorption of toxic chromium using batch experiments. To enhance the removal efficiency, the effect of parameteric alterations such as adsorbent dose; pH; shaking time etc. have been studied. The kinetic model for adsorption of chromium onto the ZnMnOAC follows the pseudo-second-order reaction. According to the evidence obtained from isotherm work, the Langmuir model is acceptable and adequate as compared to that of other models under-study with a Qmax of 250 mg/g. The negative value of thermodynamic parameters indicates that the adsorption process is both spontaneous and stable. Among the three statistical models used for the adsorption process, double-layer was best fitted with n < 0.5 (0.369-0.339) values, representing a parallel orientation of adsorbate onto the surface of adsorbent (ZnMnOAC).

Determination of Graphene Oxide Adsorption Space by Lysozyme Uptake─Mechanistic Studies.

The interaction between graphene oxide (GO) and lysozyme (LYZ) in aqueous solution was investigated for GO specific surface area determination and for the thermodynamic description of the process. It was experimentally proved that LYZ is a much better adsorbate than the most common methylene blue, allowing the determination of genuine GO surface area. Our fluorescence spectroscopy results indicate that LYZ molecules interact with GO at high- and low-affinity sites depending on the surface coverage, reflecting the protein mono- and multilayer formation, respectively. The lack of the secondary structure changes confirms LYZ usability as a model adsorbate. The calculated values of thermodynamic parameters (Δ(ΔH0) = −195.0 kJ/mol and Δ(ΔS0) = −621.3 J/molK) indicate that the interactions are exothermic, enthalpy-driven. All the reported results reveal the physical nature of the LYZ–GO interaction at the studied concentration ratios.

Kinetic control concept for the diffusion processes of paracetamol active molecules across affinity polymer membranes from acidic solutions

BackgroundParacetamol compound remains the most used pharmaceutical as an analgesic and antipyretic for pain and fever, often identified in aquatic environments. The elimination of this compound from wastewater is one of the critical operations carried out by advanced industries. Our work objective was to assess studies based on membrane processes by using two membranes, polymer inclusion membrane and grafted polymer membrane containing gluconic acid as an extractive agent for extracting and recovering paracetamol compound from aqueous solutions.ResultThe elaborated membrane characterizations were assessed using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Kinetic and thermodynamic models have been applied to determine the values of macroscopic (P and J0), microscopic (D* and Kass), activation and thermodynamic parameters (Ea, ΔH#, ΔS#, ΔH#diss, and ΔH#th). All results showed that the PVA–GA was more performant than its counterpart GPM–GA, with apparent diffusion coefficient values (107D*) of 41.807 and 31.211 cm2 s−1 respectively, at T = 308 K. In addition, the extraction process for these membranes was more efficient at pH = 1. The relatively low values of activation energy (Ea), activation association enthalpy (ΔH≠ass), and activation dissociation enthalpy (ΔH≠diss) have indicated a kinetic control for the oriented processes studied across the adopted membranes much more than the energetic counterpart.ConclusionThe results presented for the quantification of oriented membrane process ensured clean, sustainable, and environmentally friendly methods for the extraction and recovery of paracetamol molecule as a high-value substance.

Adsorptive Detoxification of Congo Red and Brilliant Green Dyes Using Chemically Processed Brassica Oleracea Biowaste from Waste Water

Water pollution being a potential risk to mankind is treated in several ways which includes chemical treatments. Among them, adsorption took a prominent position for the removal of many hazardous dyes from waste water. Here in this study, an environment-friendly, inexpensive, and broadly available leaves of Brassica oleracea were utilized for adsorption of two carcinogenic dyes, i.e., Congo red and brilliant green. The adsorbent Brassica oleracea leaves were collected, dried, and characterized by FTIR and SEM and then utilized in batch manner for dye removal. Isothermal modeling was carried out on data obtained after experiment which show the best fitting of Langmuir with [Formula: see text] 42.553 and 103.093 mg.g-1 for Congo red (CR) and brilliant green (BG), respectively. Consequently, a homogenous, monolayer mode of adsorption was followed. Kinetic modeling supported pseudosecond order and Elovich model in most suitable manner. It was also found that a spontaneous, exothermic process provided by the values of thermodynamic parameters ([Formula: see text], [Formula: see text], and [Formula: see text]) was calculated.

Batch studies of hexavalent chromium biosorption from mining wastewater using Aspergillus niger

The effects of selected process parameters in the biosorption of chromium (VI) ions for wastewater treatment using Aspergillus niger were studied whilst keeping temperature and pH constant. The biosorption capacity was observed to be optimum at 15 h contact time, 2.8 g biomass dose and 200 rpm agitation speed. The Jovanovic isotherm model best represented the biosorption equilibrium data, and the equilibrium biosorption capacity was found to be 0.0574 mg/g. The biosorption kinetics was investigated, and the pseudo-second-order kinetic model gave the best fit concerning the generated biosorption data according to linear regression analysis. Thermodynamic study of the biosorption process ascertained the values of standard thermodynamic parameters, including ΔGo, ΔHo, ΔSo, which helped characterize the biosorption process to be exothermic, physical, and spontaneous.

New equations of state describing both the dynamic viscosity and self-diffusion coefficient for potassium and thallium in their fluid phases

Experimental data on the viscosity and self-diffusion coefficient of two metallic compounds in their fluid phases, that is, potassium and thallium, are modeled using the translational elastic mode theory, which has been successfully applied to the case of water. It is shown that this theory allows the experimental data to be accounted for in accordance with their uncertainties and, above all, it allows the different variations observed between the different authors to be explained. Particularly in the case of thallium, this theory makes it possible to represent viscosity data with much better precision than the so-called reference equation of state. The dilute-gas limit laws connecting various parameters of the theory obtained in the case of water are confirmed here and thus give them a universal character. The elastic mode theory is accompanied by the development of new equations of state, mainly to describe properties along the saturated vapor pressure curve, which greatly extend the temperature range of application of these equations compared to those found in the literature. The whole analysis thus makes it possible to propose precise values of various thermodynamic parameters at the melting and boiling temperature corresponding to atmospheric pressure.

Treatment of fluorinated wastewater with chitosan modified activated sludge lysis ash.

Preparation of a novel environmentally friendly and cost-effective composite adsorbent for fluoride removal is presented in this work. An activated sludge lysis ash/chitosan (ASLA/C) composite adsorbent was synthesised using an in situ coprecipitation method, and the removal effect of the material was analysed by static adsorption, isothermal adsorption and kinetic adsorption tests. Langmuir model could better describe the adsorption process and the adsorption was in accordance with the kinetic equation of the pseudo-second-order kinetics reaction. The values of adsorption thermodynamic and kinetic parameters were indicated that the adsorption of fluoride ions is a spontaneous, heat-absorbing entropic process, and the reaction was carried out by a combination of mechanisms, such as electrostatic adsorption, ion exchange, surface complexation and hydrogen bonding. The experimental results indicated that ASLA/C can be used as a cheap and readily available alternative efficient adsorbent where the maximum fluorinate absorption was observed with 7.714 mg g-1, while solving the problem of waste from activated sludge lysis disposal and realizing the environmental benefits of waste.

Fabrication of Pb₃O₄ and Fe₂O₃ nanoparticles and their application as the catalysts in thermal decomposition of ammonium perchlorate

Nanoparticles (NPs) of lead tetroxide (Pb3O4) with the spherical morphology were manufactured by the reaction of lead nitrate with sodium hydroxide, while the nanoparticles (NPs) of red iron oxide (Fe2O3) with similar morphology were fabricated by hydrothermal route in the presence of ferric chloride hexahydrate as the precursor. Evaluation of the chemical structure, the purity and the morphology of the manufactured Fe2O3 and Pb3O4 NPs was carried out by analysis via X-ray diffraction (XRD) as well as scanning electron microscope (SEM). The outcomes of XRD recognized establishment of the desired oxides, wherever the SEM images clearly exhibited the morphology of the manufactured Pb3O4 and Fe2O3 as the spherical NPs with an average particle sizes of near to 40 and 46 nm, respectively. The catalytic effect of the metallic oxide NPs on the perfection of ammonium perchlorate (AP) thermal decomposing was established by testing their AP nano-composites via differential scanning calorimetric (DSC) together with thermogravimetric analysis (TG). Thermal behavior studies displayed that adding of 5% Fe2O3/Pb3O4 NPs (as the mixture) delivers a concerned catalytic effect during AP thermal decomposition. Additionally, thermal decomposition of AP could be amended by adding of 2% Pb3O4 NPs. Further comparison of the NPs catalytic effects was obtained by computing the values of activation energies (E) and thermodynamic parameters (i.e., ΔS#, ΔH# and ΔG#) for their thermal decomposition by non-isothermal approaches.

Biochar material derived from natural waste with superior dye adsorption performance

In this work, methyl orange (MO) in an aqueous solution was adsorbed by activated carbon prepared from date seeds (ACDS). This biochar was chemically activated using H3PO4 with a weight ratio of 1:1 at 900 °C for 2 h. Fourier Transform InfraRed analysis (FTIR), Scanning Electron Microscopy and the isoelectric pH were used to characterize the obtained material. The FTIR showed the loss of serval functional groups of the date seeds during the preparation process. The morphology study has demonstrated that ACDS exhibited a porous structure. However, the isoelectric point was found at pH 6. The maximum adsorption amount of MO on ACDS is 334 mg/g was obtained after 2 h of interaction between 0.4 g of activated carbon and 100 mg/L of MO at pH 3. Moreover, the study of adsorption isotherms showed that the pollutant adsorption data follow the Langmuir model, indicating the monolayer coverage of OM on the biochar adsorbent surface. The determined thermodynamic parameters values are negative. The nature of the reaction is therefore exothermic, feasible and the adsorption of MO is spontaneous.

ДИССОЦИАЦИЯ ОКСИДОВ ЖЕЛЕЗА В РАСПЛАВАХ ТЯЖЕЛЫХ МЕТАЛЛОВ

At present, the problem of providing corrosion resistance of steels in heavy liquid metal coolants is solved by forming and maintaining protective oxide films on the surfaces of structural steels. However, oxide films are not absolutely impermeable barriers for the components of steels (primarily iron), which, as a result of diffusion processes, inevitably enter the coolant and can interact with oxygen to form solid-phase oxides. Within the framework of this work, a method is considered for obtaining the numerical values of the quantities characterizing the processes of dissociation of iron oxides as a function of temperature and oxygen potential of HLMC. The performed calculations made it possible to obtain specific numerical values of the limiting solubilities of iron oxides as a function of the temperature and the initial state of the coolant with respect to iron and oxygen impurities, and also made it possible to obtain numerical values of other thermodynamic parameters characterizing the current and limiting state of HLMC. The considered approach is of a general nature and can be used in experimental studies of the kinetic and thermodynamic characteristics of the dissociation processes of compounds in liquid metals.