SO2 H2O Research Articles

Electron binding energies of SO2 at the surface of a water cluster

The electronic properties of SO2 at the surface of a water cluster were investigated by employing a combination of Born–Oppenheimer molecular dynamics and electron propagator theory (EPT). In our work, we utilized a revised version of the Perdew–Burke–Ernzerhof (PBE) exchange-correlation functional, which incorporates empirical corrections for dispersion interactions in line with a recent study of the air–water interface conducted by Ohto et al. [J. Phys. Chem. Lett. 10(17), 4914–4919 (2019)]. Polarization effects induce a significant broadening of the electron binding energy distribution, as predicted by EPT. This broadening can result in a substantial increase in electron affinity, impacting the chemical reactivity of SO2 at the air–water interface, a topic of significant and recent research interest. We discuss the relationship between electron binding energies (EBEs) and the specific connections of SO2 to water. The results indicate that configurations involving an OS⋯H bond tend to yield higher electron affinities compared to complex formation through S⋯OW bonds. Surprisingly, SO2 molecules not bound to water molecules according to a specific criterion may also exhibit higher electron affinities. This feature can be explained by the role played by the polarization field from water molecules. Our best estimate for the HOMO–LUMO (H–L) gap of SO2 at the surface of a water cluster is 11.6 eV. Very similar H–L gaps are predicted for isolated and micro-solvated SO2. Fukui functions for the gas phase, and the micro-solvated SO2–H2O complex supports the view that the LUMO is predominantly localized on the SO2 moiety.

First-principles study of gas molecule adsorption on Ga-doped silicene

In this paper, based on first-principles calculations, the geometric structure and electronic properties of intrinsic silicene and metal element Ga doped silicene were studied, and three harmful gases CO, SO2 and NH3 gas molecules and H2O molecules were analyzed in two adsorption properties on the surface of two material. For each gas molecule, the optimal adsorption site was tried and determined, and parameters such as adsorption distance, adsorption energy, transfer charge, recovery time, and density of states were calculated to understand the adsorption mechanism. It was found that the adsorption capacity of the selected gas molecules on intrinsic silicene was weak except for NH3. While Ga doped silicene is a relatively stable structure, the adsorption energies of CO, SO2 and NH3 gas molecules on its surface increase in different degrees, the adsorption energies are −0.51 eV, −0.82 eV and −0.73 eV, but no adsorption to H2O. The results show that the doping of Ga atoms improves the adsorption performance of silicene materials, and is less affected by the humidity in the air in practical applications, which provides a theoretical reference for the gas-sensing properties of Ga doped silicene materials.

Rovibrational spectra of SO2-containing van der Waals complexes in the v1 region of SO2. Part II. SO2–H2O and SO2–D2O

Jet-cooled rovibrational absorption spectra of SO2–H2O and SO2–D2O complexes have been measured in the v1 symmetric stretching region of SO2 around 1151 cm−1 using a segmented rapid-scan quantum cascade laser spectrometer. The rovibrational spectrum of SO2–D2O has also been measured in the v2 bending region of D2O around 1178 cm−1. The tunneling splittings caused by the internal rotation of the water unit could not be resolved under our experimental conditions. The observed rovibrational transitions for these two complexes are analyzed using a standard A-reduced Watson asymmetric top Hamiltonian, yielding precise molecular constants for the excited vibrational states. The experimental band-origins are 1156.713866(70) cm−1 for SO2–H2O and 1156.819797(66) cm−1 for SO2–D2O in the v1 region of SO2, and 1180.177901(58) cm−1 for SO2–D2O in the v2 region of D2O.

Nickel removal from an industrial effluent by electrocoagulation in semi-continuous operation: Hydrodynamic, kinetic and cost analysis

In the nickel and cobalt production plant located in Punta-Gorda Cuba, an effluent liquor is obtained with several pollutants species of Ni(II)–NH3–CO2–SO2–H2O system. In previous studies the performance of electrocoagulation (EC) for the nickel removal from this effluent was demonstrated on a lab-scale and bench-scale. In this research, geometric, electrical and equilibrium parameters used as criteria for scaling-up the EC process were evaluated through hydrodynamic, kinetic and operating cost analysis. For this purpose, four semi-continuous stirred-tank electrochemical reactors of equal sized with 200 L useful volume were design. Based on the residence time distribution (RTD) curve, the hydrodynamic behavior of EC systems followed multi-branch tanks-in-series model. Experimental mean residence time was of 92 min and hydraulic efficiency 92% for a liquor flow rate 2 L∙min−1, due to the presence of short-circuit, internal recirculation and 3% dead zone. Then, at the operating parameters: nickel concentration 277 ± 52 mg L−1, current density 6.26 mA cm−2, pH 8.40 ± 0.28 and temperature 50 ± 2 °C, the maximum nickel removal was 97.8% with an operating cost $1.008 kg−1 Ni. Combination of RTD model and the conversion time kinetic model (CTV) was presented to predict the removal efficiency with successful outcomes, and the time for complete conversion was 23.3 min under control of chemical reaction. The precipitate presented a nickel concentration of 35.71 ± 2.13%, aluminum 6.05 ± 0.83%, true density 2836 ± 449 kg m−3 and typical layered structure. These results suggest the opportunity for the projection of an industrial production unit of double lamellar hydroxide and reduce the adverse environmental impact.

Adsorption of habitat and industry-relevant molecules on the MoSi2N4 monolayer

The adsorption of various environmental gas molecules, including H2, N2, CO, CO2, O2, NO, NO2, SO2 H2O, H2S, NH3 and CH4, on the surface of the recently synthesized two dimensional MoSi2N4 (MSN) monolayer has been investigated by means of spin-polarized first-principles calculations. The most stable adsorption configuration, adsorption energy, and charge transfer have been computed. Due to the weak interaction between molecules studied with the MSN monolayer surface, the adsorption energy is small and does not yield any significant distortion of the MSN lattice, i.e., the interaction between the molecules and MSN monolayer surface is physisorption. We find that all molecules are physisorbed on the MSM surface with small charge transfer, acting as either charge acceptors or donors. The MSN monolayer is a semiconductor with an indirect band gap of 1.79 eV. Our theoretical estimations reveal that upon adsorption of H2, N2, CO, CO2, NO, H2O, H2S, NH3 and CH4 molecules, the semiconducting character of MSN monolayer is preserved and the band gap value is decreased to ~1.5 eV. However, the electronic properties of the MSN monolayer can be significantly altered by adsorption of O2, NO and SO2, and a spin polarization with magnetic moments of 2, 1, 2 μB, respectively, can be introduced. Furthermore, we demonstrate that the band gap and the magnetic moment of adsorbed MSN monolayer can be significantly modulated by the concentration of NO and SO2 molecules. As the concentration of NO2 molecule increases, the magnetic moment increase from 1 μB to 2 and 3 μB. In the case of the SO2 molecule with increasing of concentration, the band gap decreases from 1.2 eV to 1.1 and 0.9 eV. Obviously, our theoretical studies indicate that MSN monolayer-based sensor has a high application potential for O2, NO, NO2 and SO2 detection.

The simultaneous calcination/sulfation reaction of limestone under oxy-fuel CFB conditions

Using a customized thermogravimetric analyzer, the characteristics of the simultaneous calcination/sulfation reaction of limestone (the simultaneous reaction) under oxy-fuel circulating fluidized bed (CFB) boiler conditions were investigated. The results were compared with the calcination-then-sulfation reaction (the sequential reaction) that has been widely adopted by previous investigators. The sample mass in the simultaneous reaction was higher than that in the sequential reaction. With the increase of SO2 concentration (0–0.9%), the mass difference between the two reaction scenarios increased; while with the increase of temperature (890–950 °C), the difference became smaller. Calcination in the presence of SO2 was slower than that without SO2. With the increase of SO2 concentration, the pore volume of the calcined CaO decreased, and the effectiveness factors of the calcination reaction also declined. This indicates when CaSO4 forms, the pores in CaO were filled or blocked, thus increasing the internal resistance to CO2. Because the simultaneous process is the real one in CFB boilers, and it shows different characteristics from the sequential reaction, all investigations of CaO sulfation in CFB should follow this approach. Also in this work, the effects of SO2 concentration, temperature and H2O on the simultaneous reaction were studied. The sulfation ratio in the simultaneous reaction increased with higher SO2 concentration. Compared with that in the absence of H2O, 8% H2O in flue gas significantly improved sulfation. In the tested range (890–950 °C), the optimum temperature for sulfation was around 890 °C. The sulfation rate in the mass-loss stage was higher than that in the fast sulfation stage, which is likely due to the continuous generation of nascent CaO in this stage.

Simultaneous NO Removal and Hg0 Oxidation over CuO Doped V2O5-WO3/TiO2 Catalysts in Simulated Coal-Fired Flue Gas

A series of CuO doped V2O5-WO3/TiO2 based commercial selective catalytic reduction (SCR) catalysts were synthesized via the improved impregnation method for simultaneous NO removal and Hg0 oxidation under simulated coal-fired flue gas at a temperature range of 150–400 °C. Several characterization techniques, including Brunauer–Emmett–Teller analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction of H2 (H2-TPR), were used to characterize the catalysts. The results indicated that Cu3-SCR catalyst exhibited the superior catalytic activity and a wide active temperature window for simultaneous NO removal and Hg0 oxidation. The effects of flue gas components on the catalytic activity were also investigated. The results indicated that Cu3-SCR catalyst showed good performances on SO2 tolerance and H2O resistance. The effect of Hg0 on NO removal was almost negligible. However, the copresence of NO and NH3 obviously inhibited the Hg0 oxidation activity. Furthe...

In Situ FT-IR and DFT Study of the Synergistic Effects of Cerium Presence in the Framework and the Surface in NH3-SCR

Mn-Ce/CeAPSO-34 was prepared, in which manganese and cerium were supported on the surface through using the Ethanol dispersion method, while cerium was incorporated in the SAPO-34 framework by a one-step hydrothermal method. Based on our previous study, a strong synergistic effect of cerium presented in the framework and the surface was existing in Mn-Ce/CeAPSO-34 catalyst, which showed outstanding SO2 tolerance and H2O resistance in the low-temperature NH3-SCR. In situ FT-IR and DFT calculations were used to investigate the synergistic effects. Based on the characterization results of in situ FT-IR study, it was found that more amount of nitrate species and NH3 species adsorbed on the surface of Mn-Ce/CeAPSO-34, while less the amount of sulfate species deposited during reaction process, which in the presence of SO2. Meanwhile, DFT calculations revealed that Ce site supported on the surface, which neighbored by Ce site in the framework more were capable of reacting with NO and NH3.

Theoretical study of the hydrolysis of HOSO+NO2 as a source of atmospheric HONO: effects of H2O or NH3

Environmental contextNitrous acid (HONO) has long been recognized as an important atmospheric pollutant, with the reaction of HOSO+NO2 being a source of HONO. We explore the effects of an additional water or ammonia molecule on this reaction. Calculations show that the ammonia molecule has a more effective role than the water molecule in assisting the reaction. AbstractDepending on different ways that NO2 approaches the HOSO radical, the main reactant complexes HOS(O)NO2 and HOS(O)ONO–L (lowest energy structure of the isomer) were revealed by Lesar et al. (J. Phys. Chem. A 2011, 115, 11008), and the reaction of HOSO+NO2 is a source of trans (t)-HONO and SO2. In the present work, the water molecule in the hydrolysis reaction of HOSO+NO2 not only acts as a catalyst giving the products of t-HONO+SO2, but also as a reactant giving the products of t-HONO+H2SO3, c-HONO+H2SO3 and HNO3+t-S(OH)2. For the reaction of HOSO+NO2+H2O, the main reaction paths 2, 7, and 9 are further investigated with an additional water or ammonia molecule. The CBS-QB3 calculation result shows that the process of HOS(O)NO2–H2O → t-HONO–SO2–H2O is favourable with a barrier of 0.1kcal mol–1. Although the following process of t-HONO–SO2–H2O → t-HONO–H2SO3 is unfavourable with a barrier 33.6kcal mol–1, the barrier is reduced by 17.3 or 26.3kcal mol–1 with an additional water or ammonia molecule. Starting with HOS(O)ONO–L–H2O, the energy barriers of path 7 and path 9 are reduced by 8.9 and 8.5kcal mol–1 with an additional water molecule and by 9.9 and 9.2kcal mol–1 with an additional ammonia molecule. Ammonia is more beneficial than water for assisting the HOSO+NO2+H2O reaction. Three t-HONO–H2SO3 isomers which contain double intermolecular hydrogen bonds are studied by frequency and natural bond orbital calculations. Frequency calculations show that all hydrogen bonds exhibit an obvious red shift. The larger second-order stabilisation energies are consistent with the shorter hydrogen bonds. H2SO3 can promote the process of t-HONO → HNO2, and reduce the barrier by 45.2kcal mol–1. The product NH3–H2SO3 can further form a larger cluster (NH3–H2SO3)n (n=2, 4) including NH4+HSO3– ion pairs.

Novel CeO2@TiO2 core–shell nanostructure catalyst for selective catalytic reduction of NOx with NH3

The CeO2@TiO2 core–shell nanostructure catalyst prepared by a two-step hydrothermal method was used for selective catalytic reduction (SCR) of NOx with NH3 in this study. The catalyst presented the obvious core–shell structure, and the shell was amorphous TiO2 which could protect the active center from the SO2 erosion. The catalyst showed high activity and stability, excellent N2 selectivity and superior SO2 resistance and H2O tolerance. Characterizations such as TEM, HR-TEM, XRD, BET, XPS, NH3-TPD, and H2-TPR were carried out. The results indicated that the catalyst had large surface area and the active sites were well dispersed on the surface. The NH3-TPD, H2-TPR and XPS results implied that its increased SCR activity might be due to the enhancement of NH3 chemisorption and the increase of active oxygen species, both of which were conductive to NH3 activation. The excellent catalytic performance suggests that it is a promising candidate for SCR catalyst.

Rate-based modelling of combined SO 2 removal and NH 3 recycling integrated with an aqueous NH 3 -based CO 2 capture process

To reduce the costs of controlling emissions from coal-fired power stations, we propose an advanced and effective process of combined SO2 removal and NH3 recycling, which can be integrated with the aqueous NH3-based CO2 capture process to simultaneously achieve SO2 and CO2 removal, NH3 recycling and flue gas cooling in one process. A rigorous, rate-based model for an NH3–CO2–SO2–H2O system was developed and used to simulate the proposed process. The model was thermodynamically and kinetically validated by experimental results from the open literature and pilot-plant trials, respectively. Under typical flue gas conditions, the proposed process has SO2 removal and NH3 reuse efficiencies of >99.9%. The process is strongly adaptable to different scenarios such as high SO2 levels in flue gas, high NH3 levels from the CO2 absorber and high flue gas temperatures, and has a low energy requirement. Because the process simplifies flue gas desulphurisation and resolves the problems of NH3 loss and SO2 removal, it could significantly reduce the cost of CO2 and SO2 capture by aqueous NH3.

Vapor–liquid equilibrium of CO2 in NH3–CO2–SO2–H2O system

Vapor–liquid equilibrium (VLE) of CO2 in CO2 and SO2 loaded aqueous ammonia (NH3–CO2–SO2–H2O system) was investigated in this study. The effect of SO2 loading (mol SO2/mol NH3 in solvent) on VLE of CO2 was measured in the range of 0.1–0.3mol SO2/mol NH3 in 2.5–7.5wt.% aqueous ammonia at 20°C, 40°C and 60°C, using a Fourier transform infrared (FT-IR) gas analysis method with a pressure determination stirred tank apparatus. The equilibrium vapor pressures of CO2 in the aqueous ammonia with no SO2 content were compared with experimental data in the public domain. The electrolyte NRTL model was carried out to predict the VLE data using Aspen Plus. The comparison between experimental results and model predictions showed good agreement. The total equilibrium pressure, NH3 equilibrium partial pressure and liquid speciation in the NH3–CO2–SO2–H2O system were calculated and analyzed. It was found that the total equilibrium pressure decrease slightly at lower CO2 loading (mol CO2/mol NH3), but increase sharply at higher CO2 loading with SO2 loading. The NH3 equilibrium partial pressure, and the NH3 and NH2COO− molar concentrations decrease with SO2 loading. However, the NH4+ and HCO3− molar concentrations increase with SO2 loading. Further CO2 equilibrium partial pressure analysis shows that the driving force and solvent capacity of CO2 absorption decrease with SO2 loading, while the desorption capacity and driving force of CO2 at high temperature significantly increases with SO2 loading, which has the potential to reduce the regeneration energy of CO2.

Water-Accelerated OH Addition to Sulfur Dioxide SO2: Direct Ab Initio Molecular Dynamics (AIMD) Study

Ionization dynamics of water microsolvated sulfur dioxide SO2(H2O)n (n = 1-3 and 6) have been investigated by means of direct ab initio molecular dynamics (AIMD) method to elucidate the hydration effects of OH addition reaction to SO2 following the ionization. The calculations showed that the neutral 1:1 complex SO2-H2O has a C(s) symmetry and the sulfur of SO2 interacts with the oxygen of H2O with an eclipsed form. In the case of ionization of SO2-H2O 1:1 complex (n = 1), the cation complex composed of [H2O-SO2](+) with a face-to-face form was obtained as the product. The OH addition reactions to SO2 were found in larger systems (n = 2, 3, and 6) following the ionization. The reaction was expressed as SO2(+)(H2O)n → SO2(OH)···H(+)(H2O)(n-1) (n = 2, 3, and 6). The proton generated as (SO2-H2O)(+) → (HSO3) + H(+) was stabilized by the second water molecule as the reaction: H(+) + H2O → H3O(+). These processes occurred and were completed within the cluster. The OH addition mechanism in SO2(+)(H2O)n cluster was discussed on the basis of the present results.

The thermal stability of sideronatrite and its decomposition products in the system Na2O–Fe2O3–SO2–H2O

The thermal stability of sideronatrite, ideally Na2Fe3+(SO4)2(OH)·3(H2O), and its decomposition products were investigated by combining thermogravimetric and differential thermal analysis, in situ high-temperature X-ray powder diffraction (HT-XRPD) and Fourier transform infrared spectroscopy (HT-FTIR). The data show that for increasing temperature there are four main dehydration/transformation steps in sideronatrite: (a) between 30 and 40 °C sideronatrite transforms into metasideronatrite after the loss of two water molecules; both XRD and FTIR suggest that this transformation occurs via minor adjustments in the building block. (b) between 120 and 300 °C metasideronatrite transforms into metasideronatrite II, a still poorly characterized phase with possible orthorhombic symmetry, consequently to the loss of an additional water molecule; X-ray diffraction data suggest that metasideronatrite disappears from the assemblage above 175 °C. (c) between 315 and 415 °C metasideronatrite II transforms into the anhydrous Na3Fe(SO4)3 compound. This step occurs via the loss of hydroxyl groups that involves the breakdown of the [Fe3+(SO4)2(OH)]∞2− chains and the formation of an intermediate transient amorphous phase precursor of Na3Fe(SO4)3. (d) for T > 500 °C, the Na3Fe(SO4)3 compound is replaced by the Na-sulfate thenardite, Na2SO4, plus Fe-oxides, according to the Na3Fe3+(SO4)3 → 3/2 Na2(SO4) + 1/2 Fe2O3 + SOx reaction products. The Na–Fe sulfate disappears around 540 °C. For higher temperatures, the Na-sulfates decomposes and only hematite survives in the final product. The understanding of the thermal behavior of minerals such as sideronatrite and related sulfates is important both from an environmental point of view, due to the presence of these phases in evaporitic deposits, soils and sediments including extraterrestrial occurrences, and from the technological point of view, due to the use of these materials in many industrial applications.

Pretreatment of wheat straw using SO2 dissolved in hot water

Efficient pretreatment is important for complete enzymatic conversion of lignocellulosic materials. Pretreatment of wheat straw with sulfur dioxide (SO2) dissolved in hot water achieved xylose and total product yields of up to 61.1% and 93.9%, respectively, based on the mass of lignocellulose in wheat straw. The apparent activation energies for hemicellulose conversion and xylose dehydration were 7.8 and 9.0kJ/mol. FT-IR spectra of the residual solid after treatment showed that the hemicellulosic components were converted, the hydrogen bonds in cellulose were broken, but the lignin structure was not changed. Importantly, the SO2 was recovered from the product mixture by steam stripping and could be reused. Thus, the SO2–H2O system is an efficient and environmentally friendly way for the conversion of hemicellulose in wheat straw into monosaccharides, such as xylose, glucose and arabinose.

Mechanistic study on the atmospheric formation of acid rain base on the sulfur dioxide

The reaction pathways of acid rain formation from reaction of sulfur dioxide vapor and water vapor on the singlet potential energy surface have been investigated theoretically. The calculated results show that the reactants are initially associated with the adduct SO2–H2O through a barrier less process. Subsequently, via a variety of transformations of isomer SO2–H2O, three kinds of products H2SO3, SO3 + H2, and H2O2 + 3SO are obtained. The cleavage and formation of the chemical bonds in the reaction pathways have been discussed using the structural parameters. Also, by means of the transition states and their connected intermediates or products at the CCSD(T)//B3LYP level, mechanism of H2O + SO2 reaction on the singlet potential energy surface are plotted. The calculation results show that the most suitable reaction pathways are the formation of H2SO3. Finally, the rate constants have been calculated only for these suitable pathways by the RRKM and TST theories at temperature range of 250–2500 K.

Single photon ionization of van der Waals clusters with a soft x-ray laser: (SO2)n and (SO2)n(H2O)m

van der Waals cluster (SO2)n is investigated by using single photon ionization of a 26.5 eV soft x-ray laser. During the ionization process, neutral clusters suffer a small fragmentation because almost all energy is taken away by the photoelectron and a small part of the photon energy is deposited into the (SO2)n cluster. The distribution of (SO2)n clusters decreases roughly exponentially with increasing cluster size. The photoionization dissociation fraction of I[(SO2)(n-1)SO+] / I[(SO2)n+] decreases with increasing cluster size due to the formation of cluster. The metastable dissociation rate constants of (SO2)n+ are measured in the range of (0.6-1.5) x 10(4) s(-1) for cluster sizes 5< or =n< or =16. Mixed SO2-H2O clusters are studied at different experimental conditions. At the condition of high SO2 concentration (20% SO2 partial pressure), (SO2)n+ cluster ions dominate the mass spectrum, and the unprotonated mixed cluster ions (SO2)nH2O+ (1< or =n< or =5) are observed. At the condition of low SO2 concentration (5% SO2 partial pressure) (H2O)nH+ cluster ions are the dominant signals, and protonated cluster ions (SO2)(H2O)nH+ are observed. The mixed clusters, containing only one SO2 or H2O molecule, SO2(H2O)nH+ and (SO2)nH2O+ are observed, respectively.

Exploration of Venus with the Venera-15 IR Fourier spectrometer and the Venus Express planetary Fourier spectrometer

The infrared spectrometry of Venus in the range 6–45 μm allows one to sound the middle atmosphere of Venus in the altitude range 55–100 km and its cloud layer. This experiment was carried out onboard the Soviet automatic interplanetary Venera-15 station, where the Fourier spectrometer for this spectral range was installed. The measurements have shown that the main component of the cloud layer at all measured latitudes in the northern hemisphere is concentrated sulfuric acid (75–85%). The vertical profiles of temperature and aerosol were reconstructed in a self-consistent manner: the three-dimensional fields of temperature and zonal wind in the altitude range 55–100 km and aerosol at altitudes 55–70 km have been obtained, as well as vertical SO2 profiles and H2O concentration in the upper cloud layer. The solar-related waves at isobaric levels in the fields of temperature, zonal wind, and aerosol were investigated. This experiment has shown the efficiency of the method for investigation of the Venusian atmosphere. The Planetary Fourier Spectrometer has the spectral interval 0.9–45 μm and a spectral resolution of 1.8 cm−1. It will allow one to sound the middle atmosphere (55–100 km) of Venus and its cloud layer on the dayside, as well as the lower atmosphere and the planetary surface on the night side.

Electrochemical properties of polypropylene membranes modified by the plasma polymerization coating of SO2/acetylene

AbstractPolypropylene membranes were modified by the plasma etching of SO2, SO2O2, or SO2H2O, followed by the plasma polymerization coating of SO2/acetylene. The conditions for SO2 plasma etching were optimized by the measurement of the ion‐exchange capacity (IEC) as a function of the plasma‐etching power (10–30 W), gas pressure (40–60 mTorr), and treatment time (15–120 s). For the plasma etching of SO2O2 and SO2H2O, only the pressure ratio (SO2/O2 and SO2/H2O) was optimized under the optimized conditions determined from SO2 plasma etching. Plasma etching was then combined with the plasma polymerization coating of SO2/acetylene, for which the conditions were again optimized by the measurement of the IEC as a function of the plasma power (10–40 W), chamber pressure (50–200 mTorr), SO2/acetylene ratio (15/135–60/90), and treatment time (0–10 min). Next, the electrical resistance and water uptake were evaluated. The modified membranes were also analyzed with scanning electron microscopy, whereas plasma polymer coatings were characterized with Fourier transform infrared/attenuated total reflection. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3692–3699, 2006

Equilibrium and Mass Transfer in the Ca 2+–SO 2–H 2O System for the Analysis of the Flue Gas Desulphurization Process

An industrial desulphurization process is modelled on the basis of equilibrium data, mass balance, mass transfer and plant data. For the Ca2+–SO2–H2O system the equilibrium diagram at 25°C is constructed. The diagram presents the concentration of total SO2 combined SO2, true free SO2, the pH value and the solubility curve for CaSO3.1/2H2O. Besides the basic chemistry occuring in the process, the role of relevant additional chemical species is explained. The overall desulphurization process is studied through the analysis of the partial processes: absorption of SO2 and sulphite to bisulphite reaction; limestone dissolution and its reaction with Ca(HSO3)2; absorption of O2, oxidation of CaSO3 and gypsum crystallization mass balance and the mass transfer. The model is tested on the basis of data taken from an industrial plant.