Langmuir Adsorption Theory Research Articles

Chitosan grafted with gallic acid and cerium dioxide hybrid nanocomposites as environmentally friendly corrosion inhibitors for mild steel: An experimental and computational study

Chitosan grafted with gallic acid (CS-GA), along with CS-GA doped with CeO2 nanoparticles (CS-GA-CeO2) were synthesized as novel environmentally friendly mild steel corrosion inhibitors. The formation of these derivatives was confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), hydrogen nuclear magnetic resonance spectroscopy (1H NMR), and thermal analysis (TGA). Based on potentiodynamic polarization curves (PDP) measurements, the inhibitors acted primarily as hybrid inhibitors, while following the Langmuir adsorption theory model. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy(XPS) and 3D surface profiles, confirmed that CS-GA-CeO2 adsorbed on the mild steel forming a protective layer thus preventing the invasion of corrosive media. The corrosion protection mechanism of chitosan derivatives was investigated by molecular dynamics simulations. Electrochemical measurements were used to investigate the corrosion inhibition by CS-GA and CS-GA-CeO2 on mild steel in a 3.5 % NaCl solution. At room temperature, the highest inhibition efficiency (93.58 %) was achieved at 200 ppm CS-GA-CeO2. Modified chitosan nanocomposites were confirmed as promising corrosion inhibitors.

Controllable synthesis of porous boron nitride fibers modified by cobalt and nickel oxides for efficient ceftriaxone sodium adsorption from aqueous solution.

Antibiotics can easily enter the water environment through direct or indirect approach, causing environmental pollution and endangering the health of organisms. Therefore, development of highly efficient adsorbent materials to adsorb and remove antibiotics is necessary. Here, cobalt oxide and nickel oxide are uniformly and tightly bonded on the surface of porous boron nitride fibers (PBNFs-NiCo), significantly increasing the number of functional groups (B-O and N-H) and hydrogen bond receptors within PBNFs. The total pore volume and specific surface area of resulting PBNFs-NiCo can reach up to 0.48 cm3/g and 720.3 m2/g, respectively. Encouraged by the unique micromorphology and chemical composition mentioned above, PBNFs-NiCo exhibits excellent ceftriaxone sodium (CS) adsorption ability, showing the adsorption capacity and removal efficiency up to 410.9 mg/g and 96.5%, respectively. Chemical adsorption plays an important role in their adsorption behavior, abiding by Langmuir adsorption theory and pseudo-second-order kinetic equation. Importantly, PBNFs-NiCo exhibits fascinating adsorption effects in surroundings with pH ranging from 4 to 6, 25 °C and varying salt concentrations. This work would establish a practical and feasible foundation for the practical application of PBNFs-NiCo for CS adsorption in aqueous solution.

Heavy metal decontamination by ion exchange polymers for water purification: counterintuitive cation removal by an anion exchange polymer

Ion exchange polymers were used for mercury and lead ions removal in water. The heavy metal ion concentration was analyzed by two independent methods: inductively coupled plasma–optical emission spectroscopy (ICP-OES) and gravimetry. The studied cation exchange polymer (CEP) was sulfonated poly(ether ether ketone) (SPEEK), and the anion exchange polymer (AEP) was poly(sulfone trimethylammonium) chloride (PSU-TMA). The removal capacity was connected with the ion exchange capacity (IEC) equal to 1.6 meq/g for both polymers. The concentration ranges were 0.15–0.006 mM for Hg2+ and 10.8–1.0 mM for Pb2+. SPEEK achieved 100% removal efficiency for mercury and lead if the concentration was below the maximum sorption capacity (Qmax), which was about 210 mg/g for Pb2+ with SPEEK. For PSU-TMA, the surprising removal efficiency of 100% for Hg2+, which seemed incompatible with ion exchange, was related to the formation of very stable complex anions that can be sorbed by an AEP. Langmuir adsorption theory was applied for the thermodynamic description of lead removal by SPEEK. A second-order law was effective to describe the kinetics of the process.

Dopamine functionalized graphene oxide (DGO) as a corrosion inhibitor against X60 carbon steel corrosion in a simulated acidizing environment; An electrochemical, weight loss, SERS, and computational study

This study examines the effectiveness of dopamine-functionalized graphene oxide (DGO) as a corrosion inhibitor for carbon steel in a 15 % HCl solution simulating an oilfield acidizing corrosive environment. Experimental electrochemical and weight loss techniques were used for the evaluation, complemented by surface analytical methods such as FTIR, SEM/EDS, and AFM. The influence of temperature on the performance of the inhibitor was also studied. The adsorption behavior of DGO at different concentrations was studied using surface-enhanced Raman scattering (SERS). Computational tools were also used to understand the mode of adsorption of the inhibitor molecules on the steel surface and the nature of the interaction between the silver nanoparticles used in the SERS study and the inhibitor molecules. DGO showed a maximum inhibition efficiency of over 85 % at room temperature at the optimum concentration of 5 ppm as observed in the weight loss and electrochemical studies. The inhibitor behaved like a mixed-type according to the PDP measurement and obeyed the Langmuir adsorption theory. SEM/EDS, AFM, and FTIR analyses of the steel surface after 24 h of immersion in the test solution confirmed the adsorption of the inhibitor on the steel surface to form a protective layer that protects the steel from aggressive attack by corrosive media. The intensity of SERS showed a strong correlation with the electrochemical and weight loss results. Computational analysis revealed that the primary adsorption mechanism of DGO molecules on the carbon steel surface involves the bonding between the steel surface and the aromatic rings of the GO component. This research is significant as it addresses two major environmental issues: corrosion and waste disposal using GO derived from waste graphite powder. The SERS technique used in this study has the potential to serve as a sensor to monitor the dynamic adsorption of corrosion inhibitors irrespective of the type of metal.

Porous BCNO fibers for efficient methylene blue adsorption from aqueous solution

With the development of dye production and the printing/dyeing industry, the discharge of dyestuff wastewater has sharply increased, posing a threat to the health of organisms. Therefore, it is necessary to develop efficient adsorbent materials to remove dyes. Porous BCNO (pBCNO) was prepared via pyrolysis of melamine borate modified by hydroxyethyl cellulose (HEC). Compared to traditionally pyrolytic melamine borate, the incorporation of HEC can not only alter the product's microstructure, but also significantly adjust its bonding and chemical composition. Specifically, the specific surface area and total pore volume of pBCNO are as high as 1102.4 m2/g and 0.55 cm3/g, respectively. The generation of B–N, C–B, C–O, N–C and B–O bonds enriches the bonding and chemical activity of pBCNO. Encouraged by these unique microstructures and chemical compositions, pBCNO exhibits excellent methylene blue (MB) adsorption and recycling capabilities, showing a maximum adsorption capacity and removal efficiency of 709.5 mg/g and 99.9 %, respectively. The adsorption behavior is dominated by chemical adsorption, following Langmuir adsorption theory and pseudo-second-order model. This study not only provides a new synthesis route to pBCNO, but also establishes an experimental and theoretical foundation for the practical adsorption of pBCNO toward organic pollutants in industrial effluent.

Rapid Hydrate Formation Conditions Prediction in Acid Gas Streams

Sour gas in hydrocarbon reservoirs contains significant amounts of H2S and smaller amounts of CO2. To minimize operational costs, meet air emission standards and increase oil recovery, operators revert to acid gas (re-)injection into the reservoir rather than treating H2S in Claus units. This process requires the pressurization of the acid gas, which, when combined with low-temperature conditions prevailing in subsurface pipelines, often leads to the formation of hydrates that can potentially block the fluid flow. Therefore, hydrates formation must be checked at each pipeline segment and for each timestep during a flow simulation, for any varying composition, pressure and temperature, leading to millions of calculations that become more intense when transience is considered. Such calculations are time-consuming as they incorporate the van der Walls–Platteeuw and Langmuir adsorption theory, combined with complex EoS models to account for the polarity of the fluid phases (water, inhibitors). The formation pressure is obtained by solving an iterative multiphase equilibrium problem, which takes a considerable amount of CPU time only to provide a binary answer (hydrates/no hydrates). To accelerate such calculations, a set of classifiers is developed to answer whether the prevailing conditions lie to the left (hydrates) or the right-hand (no hydrates) side of the P-T phase envelope. Results are provided in a fast, direct, non-iterative way, for any possible conditions. A set of hydrate formation “yes/no” points, generated offline using conventional approaches, are utilized for the classifier’s training. The model is applicable to any acid gas flow problem and for any prevailing conditions to eliminate the CPU time of multiphase equilibrium calculations.

Mechanism of Fast NO Response in a WO3-Nanorod-Based Gas Sensor

The development of fast and reliable gas sensors is a pressing and growing problem for environmental monitoring due to the presence of pollutants in the atmosphere. Among all gases, particular attention is devoted to NO, which can cause serious health problems. WO3 nanorods represent promising candidates for this purpose due to their high electrical stability and low cost of production. Here, the hydrothermal synthesis of WO3 nanorods is reported, in addition to the realization of a chemo-resistive NO sensor. NO-sensing tests were performed at different temperatures (250–400 °C) and under different gas concentrations (250–2500 ppm), and NO response and recovery curves were also modeled by using the Langmuir adsorption theory by highlighting the NO-sensing mechanism of the WO3 nanorods. An interaction occurred at the surface between NO and the adsorbed oxygen ions, thus clarifying the NO-reducing behavior. The fast response and recovery times open the route for the development of fast NO sensors based on WO3.

Utilizing birch leaf extract in pickling liquid as a sustainable source of corrosion inhibitor for pipeline steel

This study set out to determine the effectiveness of birch leaves extract (BLE) as a corrosion inhibitor against X52 pipeline steel in the pickling solution. Chemical and electrochemical techniques, as well as scanning electron microscope (SEM), Fourier-transform infrared (FT-IR), and adsorption isotherms were used in the research. Various triterpenoids, including betulin, betulinic acid, oleanolic acid, sitosterol, and kaempferol, are unquestionably involved in the corrosion inhibition mechanism, according to the high-performance-liquid-chromatography (HPLC) analysis. The 95% efficiency of the produced BLE extract (at optimum concentration 400 mg L−1) significantly reduced the corrosion rate of X52 pipeline steel in the pickling solution. The adsorption of BLE extract molecules on the X52-steel surface was demonstrated by SEM and FT-IR analysis. The adsorption activity follows the Langmuir adsorption theory.

Diaminoalkanes functionalized graphene oxide as corrosion inhibitors against carbon steel corrosion in simulated oil/gas well acidizing environment

Experimental weight loss and electrochemical measurements were used at ambient and high temperatures to evaluate the corrosion inhibition efficacies of diaminodecane functionalized graphene oxide (DAD-GO) and diaminododecane functionalized graphene oxide (DADD-GO) against carbon steel corrosion in 15.0 %HCl, mimicking an acidizing environment in an oil/gas well. The GO was made from waste graphite and then grafted with the diaminoalkanes (DAD & DADD). The GO and functionalized GOs were described using FTIR, Raman, TEM, and TGA. Concentration and temperature effects on the inhibitors'performance were also looked into. The inhibition efficiency increased with concentration at room temperature, reaching a maximum of 84 % for DAD-GO and 78 % for DADD-GO at a concentration of 5 ppm for both. At the temperatures studied, the inhibitors performed well at extremely low concentrations; however, as the temperature rises, the inhibitor's performance decreases. According to the PDP measurement, the inhibitors function primarily as mixed-type inhibitors. The Langmuir adsorption theory was found to be followed by thestudied compound. AFM, SEM, EDX, and FTIR characterization of the steel surfaces revealed that the functionalized GOs molecules adsorbed on the steel to create a protective layer that insulated the steel from aggressiveacid assault after the immersion time (24 h) in the inhibited solutions. DFT calculations were utilized to determine the relative stability of functionalized GOs toGOand to learn more about the inhibitor molecules' interactions with the steel surface. The DFT calculations corroborated the experimental findings. This study is important in tackling two significant environmental concerns: corrosion and waste management because GO is manufactured from waste graphite.

Performance Evaluation of an Octadecyltrimethyl Ammonium Chloride-Dimethyl Silicone Oil as a Waterproof Locking Agent in Low-Permeability Reservoirs.

Low porosity and permeability of oil and gas reservoirs make it difficult to develop these resources. To address these problems, we developed and evaluated a novel, environmentally friendly waterproof locking agent, which was prepared using dimethyl silicone oil and octadecyltrimethylammonium chloride and characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and particle size measurement. The waterproof locking performance of the agent was evaluated in a low-permeability reservoir using surface tension and contact angle measurements, and thermodynamic calculations were performed. The average particle size or median diameter (D50) of a 1% mother liquor was 325 nm at 20 °C and 470.8 nm at 70 °C. The contact angle of clean water on the core surface increased from 10 to 110°. At 70 °C, the surface tension of water was reduced to 24 mN·m–1, indicating good waterproof locking performance. The interaction parameters were calculated in accordance with the Langmuir adsorption theory. The increase in temperature from 20 to 70 °C reduced Γmax from 4.59 × 10–6 to 1.36 × 10–6 mol·m–2 and ΔGθ from −40.93 to −56.54 kJ·mol–1. Thus, the adsorption behavior of the developed locking agent is believed to improve the productivity of oil wells.

Inhibition Effect and Mechanism Explanation of Perilla Seed Extract as a Green Corrosion Inhibitor on Q235 Carbon Steel.

The development of environmentally friendly corrosion inhibitors has become a research hotspot. Aiming at the potential corrosion inhibition effect of perilla seed extract on Q235 carbon steel, the corrosion inhibition effect was quantitatively evaluated by various research methods, and the effective corrosion inhibition composition and mechanism were discussed. The research methods include potentiodynamic polarization curve method, HPLC-MS, FT-IR, XPS and chemical calculation. The experimental results show that the inhibitor prepared from perilla seed extract is a mixed inhibitor, and its adsorption behavior accords with Langmuir adsorption theory and its adsorption free energy is −22.70 kJ/mol. Combined with the experimental results and theoretical calculation, the effective corrosion inhibiting components are luteolin and apigenin. Theoretical calculation shows that both of them are adsorbed parallel to the surface of carbon steel to form thin films. The adsorption mechanism is that carbonyl O atoms in luteolin and apigenin hybridize with the 3 d empty orbit of Fe. From the point of view of quantum chemistry, the smaller the HOMO value and the energy gap value, the better the adsorption of corrosion inhibitor on the surface of carbon steel. From the point of view of molecular dynamics simulation, the greater the absolute value of adsorption energy, the better the adsorption of corrosion inhibitor on carbon steel surface.

Synthesis of Amine Grafted Poly (Acrylic-Maleic) as an efficient inhibitor against stainless steel corrosion in a highly saline medium

In this study, a novel amine grafted poly-(acrylic maleic) (APAM) was synthesized and its efficiency was investigated against the corrosion of stainless steel 316 L in simulated saline (3.5 % NaCl) environment using electrochemical and weight loss experiments at various temperatures i.e. 25, 40 and 60 °C. The synthesized compound was characterized by FTIR, proton, and carbon-13 NMR techniques. The compound performed excellently and was observed to function as a mixed-type inhibitor, inhibiting both the cathodic hydrogen evolution and anodic iron dissolution reactions. The adsorption of APAM molecules obeyed the Langmuir adsorption theory and the estimated values of ∆Gado obtained using weight and PDP data suggest that APAM adsorbed on the steel surface by both the chemisorption and physiosorption mechanisms. APAM molecules adsorbed to the steel surface to create an APAM layer that inhibits the corrosive medium from reaching the surface, according to surface morphological observations and examination of the protected steel surface using SEM, EDS, AFM, and FTIR spectra.

The inhibition performance of diaminoalkanes functionalized GOs against carbon steel corrosion in 15% HCl environment

The corrosion inhibition performance of the synthesized diaminohexane modified graphene oxide (DAH-GO) and diaminooctane modified graphene oxide (DAO-GO) was investigated against the corrosion of carbon steel in 15% HCl, utilizing the experimental weight loss and electrochemical measurement techniques at ambient and high temperature. FTIR, Raman, and TEM methods demonstrate that GO was successfully synthesized and grafted with diaminoalkanes. TGA analysis revealed that DAH-GO and DAO-GO are more stable than GO. The effect of temperature and concentration on the inhibitors’ efficiency was also studied. The inhibition efficiency of DAH-GO increased with concentration, reaching a maximum of 82% while that of DAO-GO reaches a maximum of around 86% at a concentration of 5 ppm for both. The inhibitors performed well at an extremely low concentration at the temperatures tested, however as the temperature rises, the inhibitor’s performance reduces. The inhibitors function mostly as an inhibitor of the mixed kind, according to the potentiodynamic polarization measurement. The examined compounds were found to follow the Langmuir adsorption theory. DFT calculations were used to estimate the relative stability of functionalized GOs to GO and to understand the nature of the inhibitor molecules’ interactions with the steel surface. The results obtained from the DFT calculations supported the experimental results. Because GO was made from scrap graphite, this work is critical in addressing major environmental concerns: corrosion and waste management.

Modelling Methane Adsorption Isotherms on Shale at Different Temperatures

Prediction of adsorption isotherms under different temperatures is significant to reserve estimation of shale gas reservoirs. Based on the Polanyi adsorption potential theory and Langmuir adsorption theory, a method was presented to predict adsorption isotherms at different temperatures. In this method, the relationship between Langmuir pressure and temperature was quantified. By utilizing this method, we predicted adsorption isotherms of Longmaxi shale from 45 °C to 120 °C according to experimental data at 30 °C. Meanwhile, by considering the pressure and temperature gradients, we also predicted the adsorption capacity of Longmaxi shale with geologic depth. Results show that the adsorption data predicted by our method are in accord with experimental data and the error coefficient is less than 5%. In addition, the isosteric heat of adsorption for Longmaxi shale can be calculated by predicted adsorption data based on the Clausius–Clapeyron equation of capillary systems. Therefore, our study illustrates theoretical foundations for the efficient evaluation of adsorbed gas content in shale gas reservoirs at geologic conditions.

Competitive adsorption characteristics based on partial pressure and adsorption mechanism of CO2/CH4 mixture in shale pores

• Gas partial pressure is the decisive factor under certain temperature and pore size. • Each adsorption layer of mixture gas can be explained by monolayer adsorption theory. • Appropriate timing and amount of CO 2 injection were proposed for CS-EGR technology. In the context that CS-EGR technology has received more and more attention, molecular dynamics simulation method was used to analyze the competitive adsorption characteristics and mechanism of CO 2 /CH 4 mixture in graphene-MMT heterogeneous surface pores. In the case of certain temperature and pore size, the gas partial pressure of mixture is found to be the decisive factor of the competitive adsorption behavior. It’s better to describe the competitive adsorption behavior by gas partial pressure. Langmuir equation was applied to fitting adsorption isotherm in the first adsorption layer and the second adsorption layer. The good fitting results indicate that although the competitive adsorption mechanism of CO 2 /CH 4 mixture can’t be considered as monolayer adsorption due to the existence of multiple adsorption layers, each adsorption layer can be explained by Langmuir adsorption theory. To enhance the CH 4 recovery and CO 2 storage, the appropriate timing and amount of CO 2 injection were proposed. The pressure should be reduced to as low as possible in the first pressure drawdown process, because the first pressure drawdown is obviously beneficial to CH 4 production. The Ratio should be controlled not to exceed 1.11 ∼ 1.21 when injecting CO 2 . The operation recommendations can effectively enhance the shale gas recovery and CO 2 storage and may help to optimize the design of CS-EGR technology.

Low temperature detection of nitric oxide by CuO nanoparticles synthesized by pulsed laser ablation

Fast, selective and low-cost sensors for nitric oxide (NO) detection are highly desirable due to the harmful effects of this gas. Low temperature NO detection is challenging, requiring selective and effective catalytic processes. Here, we present an experimentally based CuO-NO interaction model in the 50–400 °C temperature range and a promising NO chemoresistive sensing device working at 50 °C based on CuO nanoparticles (NPs) produced by pulsed laser ablation in liquid environment (PLAL). Ligand-free Cu/Cu2O nanostructures produced by PLAL were converted into 35 ± 12 nm CuO NPs by 400 °C annealing, and analysed by X-Ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray techniques. The chemoresistive sensor is produced by drop-casting the CuO NPs suspension onto an interdigitated electrode and tested in a flow-controlled test chamber. Below 250 °C, oxidation behavior is recorded, while above 350 °C reduction takes place, with a peculiar transient regime observed at 300 °C. A full model of CuO-NO interaction is proposed, based on Langmuir adsorption theory and kinetics barriers extracted by response curves in the 50–400 °C temperature range. A peculiar catalytic activity of CuO NPs emerges in combination with oxygen species absorbed at different temperature, leading to effective NO detection. The ease and scalability of CuO NPs production by PLAL and the reported fast and selective NO sensor working at 50 °C open promising routes towards exploitation for massive and affordable harmful gas detection.

Isothermal Desorption Hysteretic Model for Deep Coalbed Methane Development

The adsorption/desorption mechanism of coalbed methane is significant for gas control and coalbed methane exploitation; scholars have done a lot of research on it and generally have confidence in that temperature, pressure, and moisture are central factors affecting the adsorption of coalbed methane. Considering the reduction of recovery efficiency caused by desorption hysteresis in deep coalbed methane drainage, the effects of high reservoir pressure, high gas content, and low permeability on the hysteresis index were analyzed. A desorption hysteresis model based on the combination of dual-porosity media and traditional Langmuir adsorption theory was proposed. By comparing with the four experimental data of Ma et al., the advantages of the new model in fitting desorption data were investigated. Based on the new desorption hysteresis model, the hysteresis index was calculated from the adsorption capacity and desorption capacity under the abandonment pressure. The hysteresis index under different coal sizes and adsorption pressure were calculated, and a good linear relationship was found between the adsorption pressure and the hysteresis index. Through a large number of field production data analysis, the following conclusions are drawn: as the adsorption pressure increases, the hysteresis index enhances; when the coal sample size increases, the hysteresis index also increases. Finally, by comparing experimental data from deep and shallow coal samples, the influence of desorption hysteresis on deep coalbed methane mining was explored. This paper draws the conclusion that although the gas content in deep coalbed methane is considerable, its hysteresis index is also enhanced, which makes coalbed methane development more difficult. The findings of this study can provide theoretical support for coal bed gas control and coal bed methane heat injection mining.

SANS characterization of time dependent, slow molecular exchange in an SDS micellar system.

We have investigated the molecular exchange of sodium dodecyl sulfate (SDS) micelles in aqueous solution by time-resolved small angle neutron scattering (TR-SANS) measurements as a function of the surfactant and salt concentration. Starting with deuterated (d-SDS) and protonated (h-SDS) SDS micelles, surfactant exchange across the micelles leads to a randomized distribution of d-SDS and h-SDS within each micelle. By employing the contrast matching technique, we have studied this randomization process which is a direct measure of the molecular exchange of this system. Our results show that the randomization of the pure h-SDS and d-SDS micelles occurs in two steps: first, an almost instantaneous drop in the scattering intensity is observed where ∼80% of the micelles are randomized (contrast matched). After this, micelle randomization progresses slowly spanning over ∼100 hours. Importantly, we show that the kinetics in the second step are dominated by the formation of domains rich in either h-SDS, d-SDS and randomized (50 : 50 h-SDS : d-SDS). The slow exchange step is modeled via a phenomenological approach by drawing analogy to the Langmuir adsorption theory. Finally, the effects of the surfactant and salt concentrations on the instantaneous, and the time dependent randomization of SDS micelles are discussed.

A comprehensive study of char reaction kinetics: Does CO always promote NO reduction on char surface?

This investigation focuses on the NO reduction process over chars and quantifies the effects of CO on char-NO reactivity under different conditions. Kinetic data were measured in a lab-scale fixed-bed reactor at temperatures between 1023 K and 1223 K, involving three coal chars with coal ranks ranging from lignite to anthracite. Experimental results show that CO can promote the reduction of NO over chars at low temperatures. However, there is a significant decrease in NO conversion rate at high temperatures compared to the case without CO present in the gas. The promotion or inhibition effects of CO on char-NO reactivity will become more obvious if the CO concentration is higher. Moreover, the consumption rate of NO is about the same as the generating rate of CO2 under high-level CO conditions, while a considerable amount of CO is generated during the direct reduction of NO by carbon. Further analysis based on Langmuir adsorption theory also indicates that char plays a catalytic role in NO reduction rather than acting as a reactant when CO is added. In addition, under the same temperature and gas conditions, the reactivity of SC lignite char is roughly five times higher than that of HP bituminous char and ten times higher than that of WH anthracite char, namely, the increase of coal rank leads to the decline in char-NO reactivity. Besides, the char made from higher rank coal has a broader range of temperature at which the CO presents a positive effect on NO reduction. Finally, a simple expression was proposed to calculate the NO reduction rate on char surface based on the experimental data, which can be easily applied in the description of nitrogen chemistry for fluidized bed combustion.

Application of Titanium Dioxide for Zirconium Ions Adsorption and Separation from a Multicomponent Mixture

This work studies the adsorption of zirconium ions by mesoporous titanium dioxide and by sodium-modified mesoporous titanium dioxide. Experimental maximal adsorption values of zirconium ions by H-TiO2 and Na-TiO2 were found to be 64 mg/g and 109,5 mg/g respectively. This process depends on the interaction time, equilibrium concentration of zirconium ions and acidity of the solution. Adsorption kinetics fit well into the diffusion kinetic model and indicate a several stages of zirconium ions adsorption. Equilibrium adsorption of zirconium ions is well described by the Langmuir's adsorption theory for both adsorbents. The results obtained by inductively coupled plasma mass spectrometry showed that the investigated adsorbent selectively adsorb zirconium ions from the mixture with strontium and yttrium ions in the range of solution pH = 0-1. The percentage of maximum extraction of zirconium ions is 86,61% for H-TiO2 and 94,11% for Na-TiO2. This fact is extremely valuable for nuclear forensics or for the determination of 90Sr in low activity background samples.