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Upgrading CO2-rich natural gas or biogas through CO2 capture is essential to reduce greenhouse gas emissions and to increase its energy density. In this study, clathrate-based CO2 capture from CO2-rich natural gas or biogas was investigated with a primary focus on kinetic CO2 selectivity. The time-dependent CO2 selectivity during clathrate formation for pure water, tetrahydrofuran (THF, 5.6 mol%) solution, and tetra-n-butylammonium chloride (TBAC, 3.3 mol%) solution was examined through direct composition analysis and in situ Raman spectroscopy. In pure water, the CO2 composition in the clathrate phase was much higher at the early stage of clathrate formation than that at equilibrium, indicating that CO2 is kinetically and thermodynamically selective. For both the THF (5.6 mol%) and TBAC (3.3 mol%) solutions, the CO2 composition in the clathrate phase was almost constant during clathrate formation. However, the TBAC (3.3 mol%) solution showed significantly higher CO2 composition (∼74%) throughout the reaction, whereas the THF (5.6 mol%) solution exhibited enrichment of CH4 in the clathrate phase. The experimental results clearly demonstrate that CO2 selectivity is dependent on both kinetics and equilibrium of clathrate hydrates and that the addition of thermodynamic promoters, such as THF and TBAC, can affect kinetic CO2 selectivity as well as equilibrium CO2 selectivity in the clathrate phase.

Highlights • Thermodynamic and kinetic influences of NaCl on HFC-125a hydrate were investigated. • NaCl enrichment in the unconverted solution resulted in a lower conversion. • The presence of NaCl had little effect on the ΔH of HFC-125a hydrate. • The hydrate dissociation was retarded due to the formation of NaCl⋅2H2O. In this study, HFC-125a was selected as a hydrate-forming guest for gas hydrate-based desalination. The thermodynamic and kinetic effects of NaCl on HFC-125a hydrates were investigated with a primary focus on phase equilibria, gas uptake, dissociation enthalpy, and dissociation behavior. The equilibrium curve of HFC-125a hydrate shifted to higher pressure regions at any given temperature depending on the concentration of NaCl. The presence of NaCl also reduced the gas uptake and conversion to hydrates, because of the enrichment of NaCl in the solution during gas-hydrate formation. Even though NaCl did not affect the dissociation enthalpy of the HFC-125a hydrate, the thermograms obtained using a high-pressure micro-differential scanning calorimeter (HP μ-DSC) demonstrated that HFC-125a + NaCl hydrates started to dissociate at lower temperatures due to NaCl in unconverted solutions. Rietveld refinement of powder X-ray diffraction (PXRD) patterns indicated that the HFC-125a hydrate (sII) was transformed into Ih as it dissociated. The dissociation of HFC-125a + NaCl hydrates was retarded and completely ended at higher temperatures compared to the pure HFC-125a hydrate by the sodium chloride dihydrate (NaCl⋅2H2O). Overall, these results could facilitate a better understanding of HFC-125a hydrates in the presence of NaCl; further, they might also be useful in the design and operation of hydrate-based desalination plants using HFC-125a.

A practical-scale sandwich-type honeycomb catalyst reactor incorporating non-thermal plasma was developed for the high-throughput removal of isopropanol (IPA) from air. The Pd/γ-Al2O3/honeycomb catalyst was fabricated by coating a cordierite monolith with γ-alumina powder on which to support the palladium (Pd). The supported catalyst showed good activity and the combination of the honeycomb structure with plasma produced a uniform plasma inside the catalyst chamber. The influence of different parameters, including the energy density (SIE), humidity, initial concentration, and flow rate, on the plasma characteristics and IPA removal efficiency was investigated. The results showed that the SIE has the strongest effect on the IPA removal efficiency. The efficiency of IPA removal was 94.5% and the CO2 selectivity was 85% for an SIE of 180 J/L. Using optical emission spectroscopy, we found that the increased formation of atomic oxygen and reactive species plays an essential role in the oxidation of IPA by plasma catalysis. The main byproducts were identified by GC-MS, which indicated that acetone is the major liquid product. A plausible reaction mechanism for the plasma-catalytic oxidation of IPA is proposed based on the intermediates and byproducts.

The aim of this study was to obtain indigenously the mesoporous silica (AMS) precursor to 3-aminopropyltriethoxysilane (APTES) and utilizing chitosan a templating natural biopolymer. The textural characteristics of AMS were obtained by the SEM (Scanning Electron Microscopy) and BET (Brunauer–Emmett–Teller) surface area measurements. AMS solid possessed specific surface area of 511.77 m2/g and having pore size and pore volume of 3.38 nm and 0.036 cm3/g, respectively. Further, the AMS was characterized by the XRD (X-ray Diffraction) and FT-IR (Fourier Transform- Infra Red) analyses. The mesoporous silica was employed for efficient removal of cadmium(II) and lead(II) from aqueous solutions. The influence of solution pH, initial cadmium(II)/or lead(II) concentrations, contact time, and background electrolyte concentrations were studied to deduce the mechanism involved at solid/solution interface. The equilibrium state adsorption data were utilized for the Langmuir and Freundlich adsorption isotherms and the Langmuir adsorption isotherm showed a good agreement with the experimental data. Uptake was found to be fairly fast and the kinetic modelling suggested that the adsorption of cadmium(II)/or lead(II) by AMS was occurred through fractal-like pseudo-second order kinetics. An increase in background electrolyte concentrations from 0.0001 to 0.01 mol/L NaNO3 did not affect the removal of lead(II), whereas the cadmium(II) removal was slightly suppressed. The XPS (X-ray Photoelectron Spectroscopy) analysis indicated that removal of cadmium(II) or lead(II) occurred through the formation of a chemical bond with the oxygen atoms present with AMS solid. Furthermore, fixed-bed column adsorption was conducted and the loading capacity of cadmium(II) and lead(II) was found to be 11.54 and 8.59 mg/g, respectively.

In this study, the kinetics of guest exchange in sII (CH4 (90%) + C3H8 (10%)) hydrate – flue gas (CO2 (20%) + N2 (80%)) replacement was investigated to elucidate the replacement mechanism and guest exchange characteristics for hydrocarbon recovery and CO2 sequestration. The Rietveld refinement of Powder X-ray diffraction (PXRD) patterns of the replaced hydrates at two pressures (11.0 MPa and 17.0 MPa) demonstrated that sII hydrate – flue gas replacement occurred iso-structurally. The time-dependent guest compositions in the hydrate phase and the cage occupancy of guest molecules were examined to understand the effect of pressure on guest exchange behaviors. The increased CO2 inclusion in both the small (512) and large (51264) cages at a higher pressure resulted in the larger production of CH4 and C3H8 and a lower N2/CO2 ratio in the hydrate phase. The slower inclusion rate and lower N2 occupancy in the small (512) cages at a higher pressure during replacement were observed due to the competitive inclusion of CO2 and N2 in the small (512) cages. The molecular dynamics (MD) simulation demonstrated that the expansion or shrinkage of hydrate cages caused by guest exchange has a significant impact on the lattice parameter of the replaced hydrates and it was influenced by not only the average molecular size of guest molecules in each cage but also the dispersive movement of the guest molecules in each cage.

Large-volume atmospheric-pressure plasma based on corona discharge was successfully generated in a sandwich-type plasma reactor by controlling the humidity of the feed gas. The reactor comprised a 5-cm-high and 9-cm-wide commercial honeycomb monolith and two perforated stainless-steel disk electrodes with 3-mm holes, which covered up both sides of the monolith. The high-voltage applied disk electrode was placed 2 ~ 6 mm away from the monolith, whereas the counter ground electrode typically touched it. The characteristics of air plasma such as power delivery, breakdown voltage, current, and impedance were found to strongly depend on the water vapor content in the feed gas as well as in the monolith, exhibiting an exponential increase of discharge power with increasing the humidity. The discharge characteristics also depended on the gas flow rate and the electrode-monolith distance. Better discharge performance was observed as the electrode was closer to the monolith, and as the air flow rate was higher. Discharge power above 30 W was achieved under the condition of gas flow rate 75 L/min, applied voltage 25 kV, and humidity 2.1%(v/v) when the high-voltage electrode was 2 mm away from the monolith, and the ground electrode kept up against it. The air plasma produced reactive species, being demonstrated by the formation of ozone at several tens of ppm, depending on specific energy input. The plasma source has potential applications in the abatements of odor, organic compounds, and NOx with high throughputs.

Removal of dilute N2O from gas streams by a cyclic adsorption–decomposition using Ca13X (Ca2+ exchanged 13X) in combination with N2 nonthermal plasma was studied in this work. Zeolite 13X was found to be the best for N2O uptake among tested commercial zeolites including 4A, H-β and 13X. By modifying 13X with Ca2+ cation using ion-exchange method, the N2O adsorption capacity was greatly enhanced from ca. 3.5 × 10−6 to 80 × 10−6 mol g zeolite - 1 due to the stronger interaction of N2O with Ca2+ cation than that with Na+ cation. Ca. 96% of N2O removal efficiency at a SIEeq (equivalent specific input energy) of 1116 J L−1 was obtained under the cyclic operation of 60-min N2O adsorption (initial concentration: 510 ppm, gas flow rate: 0.5 L min−1) over Ca13X followed by 20-min plasma decomposition of adsorbed N2O in stationary N2 atmosphere. In comparison, a similar performance was reached at a relatively high SIE of 1700 J L−1 as the reactor was operated under continuous plasma condition. The time period of plasma step and therefore the energy consumption could be reduced by properly circulating N2 gas in the reactor. Also, SIEeq was found to decrease with increasing the adsorption time, whereby ca. 95% of N2O removal efficiency could be achieved at a SIEeq of 298 J L−1 as the adsorption time was 180 min. The regeneration of N2O-adsorbed Ca13X by N2 plasma was initiated by plasma-induced desorption of adsorbed N2O followed by decomposing the desorbed N2O in plasma gas phase.

Combined removal of n-heptane and CO using a catalytic reactor coupled with dielectric barrier discharge plasma was investigated over several metal oxide catalysts including bare γ-Al 2 O 3 , Ag 2 O/γ-Al 2 O 3 , MnO/γ-Al 2 O 3 , RuO 2 /γ-Al 2 O 3 and PdO/γ-Al 2 O 3 . In order to effectively utilize the heat generated during plasma discharge for enhancing catalytic reactions, the plasma-catalytic reactor was thermally insulated by covering it with a glass wool jacket. Plasma propagated radially outward from the central high-voltage electrode with gradually increasing the applied voltage, and the temperature decreased with the radial distance due to the decreased plasma intensity, exhibiting a volcanic temperature distribution. The increased reactor temperature could improve the removal of CO and the selectivity toward CO 2 . The results obtained from separate experiments of n-heptane and CO removal showed that the PdO/γ-Al 2 O 3 was the best for the simultaneous removal purpose. The effects of specific input energy ( SIE ), oxygen content, reaction temperature and PdO loading on the simultaneous removal of n-heptane and CO and the formation of byproducts were examined. The removal efficiencies of n-heptane obtained with different catalysts were similar to one another, whereas the removal of CO strongly depended on the type of catalyst. The catalytic activity for the oxidation of CO followed the order: MnO/γ-Al 2 O 3 2 O/γ-Al 2 O 3 2 /γ-Al 2 O 3 2 O 3 . In the present plasma-catalytic hybrid reactor, the mixture of n-heptane and CO was mainly converted into CO 2 , and under an optimized condition, the selectivity toward CO 2 reached 100%.

The aim of this study is to synthesize the three different hybrid materials precursor to natural biopolymer chitosan. The silanes viz., 3-mercaptopropyl trimethoxysilane, trimethoxy(octyl) silane and 3-aminopropyl triethoxysilane were grafted with the chitosan network and were named as CHMS, CHTS and CHAS, respectively. The materials were characterized by the FT-IR spectrometry, SEM–EDX and XPS analyses. These solids were then employed in the efficient removal of Cr(VI) from aqueous solutions using batch and column reactor operations. The functionalized biomaterials possessed extremely high percent removal of Cr(VI) compared to bare chitosan at wide pH range i.e., pH ∼3.0 to 8.0. A fast uptake of Cr(VI) was occurred and high percentage removal was obtained at wide range of Cr(VI) initial concentrations (7.7–100.58 mg/L). The equilibrium state sorption data were utilized for the Langmuir and Freundlich adsorption isotherm studies. Similarly, an increase in background electrolyte concentrations from 0.0001 to 0.05 mol/L NaNO 3 was assessed for the uptake of Cr(VI) by these hybrid materials. Relatively a fast uptake of Cr(VI) by these hybrid materials were obtained and further the time dependence data were fitted well to the pseudo-second-order and fractal-like pseudo-second-order kinetic models rather a pseudo-first-order kinetic model. Furthermore, a detailed sorption mechanism was included with the help of FT-IR, TOC and XPS analyses. In addition, CHMS and CHTS were used for dynamic studies under column reactor operations. The breakthrough curves were then used for the non-linear fitting of the Thomas equation and the loading capacity of the column for Cr(VI) were estimated.

The present communication addresses the development of a novel hybrid material precursor to natural sericite. The hybrid material is then successfully utilized for efficient removal of cadmium and phenol from aqueous solutions. Initially, sericite was annealed and activated with hydrochloric acid. The activation caused a significant increase in specific surface area of sericite, thereby provided a suitable surface structure for grafting of organosilanes. The activated sericite (AS) was functionalized with 3-aminopropyltriethoxysilane (APTES), and the resultant AS-APTES along with pristine sericite and AS were characterized using SEM–EDX, BET, XRD and FT-IR analyses. Batch reactor studies showed that increase in sorptive pH, contact time, initial concentration and temperature significantly favored the sorption of Cd(II), and a 100-fold increase in background electrolyte concentration did not significantly affect the uptake of Cd(II) or phenol from aqueous solutions. Cd(II) removal was found to be spontaneous and the uptake process was endothermic in nature. Further, the intra-particle diffusion was found to be the rate-limiting step in the sorption of Cd(II). Various physico-chemical parametric studies enabled to discuss the sorption mechanism of these contaminants at the solid/solution interface. In a single pollutant sorption studies, it was deduced that the Cd(II) was forming an inner-sphere complexes, whereas phenol was sorbed through the hydrogen bonding with the amino groups or partitioned within the interspace region. Simultaneous sorption studies suggested that these two pollutants were possibly removed simultaneously by the prevailing hydrophilic and hydrophobic groups. Furthermore, desorption and reusability studies as well as the applicability of the material for real wastewater treatment demonstrated that AS-APTES is a promising solid material for the efficient removal of two important water pollutants i.e., Cd(II) and phenol from aqueous waste.

This paper presents a facile method to fabricate the hole injection layer (HIL) for organic photovoltaic cells (OPVs) and organic light-emitting diodes (OLEDs) using a thermally annealed (NH 4 ) 2 WS 4 precursor under air ambient. The thermal gravimetric analysis curve shows that WS 3 , WS 2 , and WO x are formed by the thermal decomposition of (NH 4 ) 2 WS 4 above 160 °C. The disappearance of the S 2p peak in the photoemission spectra and of the W–S peak in the Raman spectra as well as the decrease in the water contact angle after annealing at 250 °C suggest that (NH 4 ) 2 WS 4 decomposed into WO x . The power conversion efficiency (PCE) of the OPV improved from 1.51% to 3.14% after the insertion of 250 °C-annealed (NH 4 ) 2 WS 4 as the HIL, which is comparable to the PCE of the OPV based on poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) HIL (3.23%). Furthermore, the luminance efficiency of the OLED with 250 °C-annealed (NH 4 ) 2 WS 4 (15.76 cd/A) was higher than that of the device based on PEDOT:PSS (12.34 cd/A). The results of the in situ deposition experiments revealed that the improved device performance originates from the energy level alignment and electron–hole balance. These data demonstrate that 250 °C-annealed (NH 4 ) 2 WS 4 is a promising candidate for fabrication of the HIL in optoelectronic devices using a facile solution process under air ambient.

Nanopillars-TiO 2 was immobilized onto a borosilicate glass disk using sol–gel template method. The TiO 2 film was immobilized with and without polyethylene glycol as filler media and annealed at 500 °C. The prepared films were characterized by the IR, XRD, XRF and XPS analytical methods. The surface morphology was obtained using FE-SEM and AFM images of these thin films and the BET specific surface area was obtained. Further, the Nanopillars TiO 2 was employed in the photocatalytic degradation of micro-pollutants viz ., diclofenac sodium and tetracycline hydrochloride from aqueous solutions using UV-light under batch reactor operations. Various physico-chemical parametric studies viz ., effect of pH, pollutant concentration and interfering ions was studied to deduce the mechanism involved in photocatalytic degradation of these pollutants. The time dependence degradation of these pollutants provided kinetics of degradation of these pollutants from aqueous solutions. The studies were further extended with total organic carbon measurement using TOC analyser to demonstrate an apparent mineralization of these pollutants. The photocatalytic degradation was assessed in presence of scavengers and several co-existing ions to simulate the data for real wastewater matrix. The hydroxyl radical scavengers 2-propanol and sodium bicarbonate greatly suppressed the catalytic activity of the thin films. However, the singlet oxygen scavenger sodium azide could not affect significantly the catalytic activity of these thin films at least the degradation of diclofenac sodium and tetracycline from aqueous solutions.

Lithium nitrate has been highlighted as a high temperature phase change material with the melting temperature of ~256 °C for the applications of thermal energy storage. However, low thermal conductivity and corrosive property of lithium nitrate needs to be improved for wide applications. This report experimentally investigates thermal properties of a phase change composite consisting of lithium nitrate and porous copper oxide nanowires integrated on folded meshes. Specifically, porous copper oxide nanowires vertically aligned on the folded copper meshes with desired shapes are synthesized by carrying out chemical solution growth and subsequent heat treatment. Then, lithium nitrate is infiltrated in the network of the thermal conductive fillers under vacuum conditions. Our platform can provide a flexible geometrical configuration to enhance thermal performance by modifying the folded geometries to the target objects. As a result, the fabricated phase change composites with 7 vol% of filling materials exhibit the 6.7 times higher thermal conductivities than pure lithium nitrate, showing the excellent thermal transport by the fillers in the composite. Moreover, the porous copper oxide nanowires exhibit excellent anti-corrosive properties to lithium nitrate for stable operation under repeated phase change processes. Finally, the phase change composite heat storages exhibit the 1.3 times faster thermal charging and discharging characteristics than pure lithium nitrate ones.

CH4–CO2 replacement in naturally occurring gas hydrates has been considered a promising method for both energy recovery and CO2 sequestration. In this study, the time-dependent guest exchange behaviors and guest distributions during CH4–CO2 replacement were closely examined at two different CO2 injecting pressures (2.2 and 3.5 MPa) using nuclear magnetic resonance (NMR), in-situ Raman spectroscopy, powder X-ray diffraction (PXRD), and gas chromatography. The 13C NMR spectra confirmed that the cage occupancy ratio of the CH4 molecules in the large 51262 and small 512 cages (θL/θS,CH4) after the replacement was significantly smaller than that before the replacement because of the preferential occupation of CO2 in the large 51262 cages. The time-dependent Raman spectra revealed that the rate of CO2 inclusion and the resultant CH4 depletion in the hydrate phase during the replacement was faster at a higher CO2 injecting pressure. The Rietveld refinement of the PXRD patterns offered a quantitative cage occupancy of CH4 and CO2 molecules before and after the replacement. The time-dependent cage occupancy values of CH4 and CO2 during the replacement obtained from a multi-methodological approach, which is a combination of PXRD analysis and in-situ Raman measurement, demonstrated that a significant guest exchange in the large 51262 cages had a greater effect on the extent of replacement and that the kinetics of the CH4–CO2 replacement was accelerated at a higher CO2 injecting pressure. The results provide a better understanding of the kinetics and mechanism of the cage-specific CH4–CO2 replacement occurring in the sI hydrates for CH4 recovery and CO2 sequestration.

A dielectric barrier discharge (DBD) plasma reactor was employed for non-oxidative coupling of methane. The coupling reaction in the DBD plasma bed was conducted near atmospheric pressure and room temperature. In the bed, dielectric materials such as ordered mesoporous silica (KIT-6), sea sand silica, and α-Al2O3 were employed. This non-catalytic reaction system could successfully activate C H bond to produce methyl radicals and light hydrocarbons without additional thermal energy and oxidant molecules. The gap distance between dielectric particles was determined by their sizes, which was experimentally shown. The effects of gap distance were found significant on the conversion and the selectivity. The existence of maximum conversion at a specific gap distance was experimentally observed and could be described successfully by using a newly developed concept of micro-electrodes. Based on the concept, the minimum threshold electric potential difference between the dielectric particles could be successfully estimated, where the conversion was shown to be maximized. Furthermore, it seemed quite possible to control the compositions of ethane, ethylene, and acetylene by properly adjusting the size or the gap distance of particles.

The degradation of sulfonamide antibiotics, such as sulfathiazole (STZ), sulfamethazine (SMT) and sulfamethoxazole (SMZ) in water was carried out with a nonthermal dielectric barrier discharge plasma reactor operating under dry air or oxygen. In order to understand the degradation pathways of the antibiotics, the plasma-treated aqueous antibiotic solutions were characterized by various techniques such as UV–visible spectroscopy, ion chromatography, liquid chromatography coupled to a tandem mass spectrometer (LC–MS/MS), pH and electrical conductivity measurements, and total organic carbon analysis. The degradation rates of the antibiotics investigated were found to be higher with pure oxygen than with dry air, and decreased in the order: SMT > STZ > SMZ. As the degradation proceeded, the characteristic absorption peaks gradually decreased and the solution pH and conductivity increased, indicating that the antibiotics were being mineralized. The ion chromatography identified both inorganic (SO42−, NO3− and NH4+) and organic ions (acetate, formate and oxalate) as the stable degradation products. After 60-min plasma treatment with oxygen, the percentage of the S atoms transformed into SO42− was in the range of 66.9–86.4%, depending upon the type of antibiotics, while of the percentage of the N atoms transformed into NH4+ and NO3− was in the range of 15.7–33.2%. The possible degradation pathways of the antibiotics were proposed from the identified intermediate products formed during the degradation, which elucidates that the hydroxylation of the ring structures in the antibiotic molecules initiates the degradation.

The aim of this study is to synthesize novel hybrid porous materials using locally available clay and commercial bentonite and to assess their suitability in the attenuation of arsenic from ground water. Therefore, the clay samples are modified with hexadecylammonium bromide (HDTMA) or pillared with aluminium and then modified with HDTMA. The hybrid materials are characterized by the FT-IR, XRD and SEM analytical methods. Moreover, the BET (Brunauer–Emmett–Teller) specific surface area along with the pore diameter was obtained for these solids. Hybrid materials are then assessed in an effective and efficient remediation of aquatic environment contaminated with arsenic. Various physico-chemical parametric studies enable to deduce plausible mechanism involved at solid/solution interface. The sorptive pH (pH 2.0–10.0), concentrations (1.0–20.0 mg/L) and background electrolyte concentrations (0.001–0.1 mg L −1 NaNO 3 ) dependence sorption of As(III) and As(V) is studied by these solids. The sorption of As(III) or As(V) by these hybrid materials are further illustrated with the FT-IR analysis conducted for the arsenic loaded solids. Further, the simultaneous removal of phenol and arsenic is assessed and results show that the hybrid materials are useful in simultaneous remediation of water contaminated with phenol and, at least, As(V). The removal of arsenic is assessed separately in presence of several cations (Cd(II), Cu(II) and Mn(II)) and anions (glycine, iminodiacetic acid, ethylene diamine tetra acetic acid disodium salt, oxalic acid, phosphate and sulfate).

Present study deals with the preparation of differently shaped copper oxide nanomaterials (CuO NMs) using simple, reproducible wet chemical and hydrothermal approach. The influence of polyethylene glycol on the morphological control was also studied. The prepared nanomaterials exhibited new types of surface morphologies such as rice grain-like, needle-like and plate-like. The Fourier transform infrared spectra and the X-ray photoelectron spectra of all the samples showed identical chemical functional groups and did not exhibit the presence of any impurities. They exhibited good stability in the aqueous environment with the zeta potential values between −25 and −27 mV. The shape dependent anti-bacterial property of the prepared CuO NMs was evaluated against two Gram-positive bacteria namely Streptococcus iniae and Streptococcus parauberis and two Gram-negative bacteria such as Escherichia coli and Vibrio anguillarum . Among three CuO NMs, the plate-like CuO NMs displayed more powerful antibacterial activity than grain or needle shaped CuO NMs.

This study investigated an underwater plasma water treatment system based on a porous hydrophobic hollow ceramic tube and an alternating current (AC) voltage source, and its application to the decomposition of taste-and-odor compounds originated from algae. The taste-and-odor compounds investigated were geosmin and 2-methyl isoborneol (2-MIB), and the decomposition of algae was carried out on cyanobacteria. The features of the present atmospheric-pressure plasma system employing a porous ceramic tube are large gas–liquid interfacial area due to the formation of numerous plasmatic gas bubbles and instant transfer of short-lived reactive species to water through the micro-pores of the ceramic tube right after the generation. The present plasma process was found to effectively decompose not only the taste-and-odor compounds but also the cyanobacteria algae. Both geosmin and 2-MIB were decomposed more rapidly in the raw river water than in the distilled water. The intermediate products resulting from the decomposition of the taste-and-odor compounds were identified, which showed that geosmin and 2-MIB underwent ring opening and subsequent bond cleavage at multiple sites. The specific energy inputs (SEIs) for 90% decomposition of algae ranged from 3.4 to 8.4 kJ L−1 for the initial concentration range of 129–1596 μg L−1. The decomposition efficiencies of the taste-and-odor compounds were well correlated with the SEI.

This work reports the potential of atmospheric pressure dielectric barrier discharge (DBD) plasma for synthesizing Ruthenium dioxide (RuO2) nanomaterials with various morphologies. The RuO2 nanomaterials were grown on four kinds of substrates including copper, silicon, glass and polyethylene terephthalate. The feed gas to the DBD plasma reactor was Ar or Ar + O2 mixture, which creates an inert or oxidation atmosphere, respectively. The prepared nanomaterials were characterized by using X-ray diffraction spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The morphology of the RuO2 nanomaterials prepared by exposing the precursor to the DBD plasma was found to depend strongly on the characteristics of the substrate as well as on the composition of the feed gas. Spherical and sheet shaped nanomaterials prepared using the above technique was analyzed for their size dependent photocatalytic behavior in the presence of visible light. Methylene blue degradation was found mainly dependent on the nanomaterial concentration and at the same time sheet shaped nanomaterials showed more catalytic activity as compared to spherical shaped RuO2.

The aim of this investigation is to assess the suitability and applicability of ferrate(VI) in the treatment of wastewaters contaminated with the Cu(II)-IDA and Zn(II)-IDA (IDA: iminodiacetic acid) complexed species in an attempt to provide safe and environmentally benign treatment process. The study was conducted for the degradation of metal(II)-IDA, followed by the oxidation of IDA and simultaneous removal of metal(II) species by the coagulation/flocculation process obtained by the reduced Fe(VI) into Fe(III). The high purity of ferrate(VI) was synthesized by the wet oxidation process in the laboratory and a regulated dose was imparted to the water contained with metal(II)-IDA species in solution. The batch reactor operations were performed for various parametric studies viz ., effect of solution pH and metal(II)-IDA concentration for a fixed dose of ferrate(VI). The pH dependence data obtained from varying pH from 8.0 to 12.0 showed that higher efficiency of degradation of Fe(VI) was occurred at lower pH value i.e., at pH 8.0. Similarly, the total organic carbon (TOC) values showed in accordance to the UV–Vis data that the lower pH values (i.e., pH at 8.0) favored an enhanced degradation/mineralization of IDA since low TOC values were obtained at low pH values. The simultaneous removal of Cu(II) and Zn(II) was obtained through the process showed that insignificant percent of metal (Cu(II) or Zn(II)) was removed by the process which was significantly enhanced at pH 12.0. The UV–Vis data recorded at different time intervals for the reduction of Fe(VI) at varied metal(II)-IDA concentrations was utilized to demonstrate the kinetics of degradation. Further, this was employed in obtaining the overall rate constant of the degradation. These kinetic data revealed that an efficient degradation of IDA was achieved using the Fe(VI) treatment.

The aim of the present investigation was to utilize the large specific surface area of activated carbons in the impregnation of the manganese oxide as further to enhance the suitability of materials in the remediation of aquatic environment contaminated with two important heavy metal toxic ions viz., Cu(II) and Pb(II). The activated carbons were obtained by exploiting two different agricultural by-product or waste materials viz., rice hulls (AC-R) or areca nut waste (AC-N) enabled, perhaps, a cost effective treatment. The in situ impregnation of manganese oxide within the pores and surfaces of ACs, therefore, was resulted to obtain the manganese immobilized ACs viz., MIAC-R and MIAC-N. These solid samples were characterized by the SEM/EDX analytical methods. Further, these materials were assessed for the removal of Cu(II) and Pb(II) from aqueous solutions under the batch and column reactor operations. The results obtained from batch experiment showed that an increase in sorptive pH was caused apparently to enhance the percent uptake of Cu(II) and Pb(II). The kinetic data were followed with the pseudo-second order kinetic models. Equilibrium modelling studies suggested that the data was fitted well to the Freundlich and Langmuir adsorption isotherms and the 1000 times increase in background electrolyte concentrations could not affect significantly the uptake of these two ions. Further, the breakthrough data was obtained by column experiment which was utilized to fit into non-linear Thomas equation. The results showed that ACs and MIACs obtained from these agriculture by-product/wastes were found to be potential solid materials for the removal of Cu(II) and Pb(II) from aquatic environment.

Spherical and sheet-like Ruthenium oxide (RuO2) nanomaterials were prepared by wet chemical approach. A new kind of sheet-like morphological features in RuO2 (with length and width >1 μm and 250 nm, respectively) was obtained by using polyethylene glycol (PEG) surfactant. The physical and chemical characterization for the synthesized RuO2 nanomaterials were carried out with the help of field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The prepared nanomaterials were assessed for the shape dependent anti-microbial activities against fish pathogenic bacteria such as Vibrio anguillarum, Edwardsiella tarda, Streptococcus iniae and Streptococcus parauberis. Energy dispersive X-ray spectroscopy (EDS mapping) displayed the adsorption of nanomaterials on the bacterial surface. Both types of nanomaterials exhibited higher antibacterial activity against Gram-negative bacteria and in particular, sheet-like RuO2 nanomaterials showed more inhibitive effect than spherical types.

This work investigated the degradation of antibiotics in synthetically prepared wastewater by using dielectric barrier discharge (DBD) plasma. The veterinary antibiotics investigated include lincomycin, ciprofloxacin, enrofloxacin, chlortetracycline, oxytetracycline, sulfathiazole, sulfamethoxazole, sulfamethazine and trimethoprim. The effect of discharge power, initial concentration, working gas type (air or O2) and working gas flow rate on the degradation was examined and discussed. The experimental results indicated that the antibiotics were easily degraded by the DBD plasma and the degradation rates were mainly governed by the amount of the delivered energy. The degradation of the antibiotics followed an exponential decay with respect to the delivered energy. Each antibiotic substance was found to show a different degradability. On the basis of an initial concentration of 5 mg L−1, the energy requirements for 60% degradation efficiency were in the range of 0.26–1.49 kJ mg−1, depending on the type of antibiotic substance, while those for 90% degradation efficiency ranged from 0.39 to 2.06 kJ mg−1. The DBD process proposed in this work may be a promising method for effectively degrading veterinary antibiotics.

A highly porous SIMFUEL particle is prepared here for use as a feed material for electrochemical reduction. The prepared particles were found to have highly porous and sintered structure. The particles were electrolyzed in a LiCl-1 wt.% Li 2 O melt at 650 °C. A steel basket containing the particles and a platinum plate were used as a cathode and an anode, respectively. The analysis result reveals the reduction extent of uranium oxide to be in excess of 99%. The rare earth oxides were reduced to their metallic form in the range of 46–78%. The highly porous structure of the SIMFUEL particles is advantageous to speed up the electrochemical reduction process for pyroprocessing.

The aim of this investigation was to obtain iron-oxide nano-particles-immobilized sand (INS) by simple impregnation process. For the purpose, locally available sand was used with prior acid activation. The INS sample was characterized by XRD and SEM/EDX analytical methods. Further, the solid was employed for its possible implication in the removal of several toxic heavy metal ions viz., Cu(II), Cd(II) and Pb(II) from aqueous solutions under the static and dynamic experimental conditions. Batch experiments were carried out analyzing various physico-chemical parametric studies viz., effect of solution pH, ionic strength and sorptive concentration. The equilibrium state data obtained by concentration dependence study was utilized to obtain the Langmuir and Freundlich adsorption modeling. INS sample was also employed to assess the suitability of material in the removal of these heavy metal toxic ions under the dynamic conditions i.e., in column studies. The breakthrough data obtained by column studies were then utilized to model it with Thomas equation and hence, estimated the loading capacity of Cu(II)/or Cd(II)/or Pb(II) under the specified column conditions. Results obtained showed that INS is found to be one of promising and effective solid material and could be used in several wastewater treatment strategies in particular the treatment wastewaters contaminated with these heavy metal toxic ions.

The present communication aims towards the possible exploitation of modified natural sand materials in the remediation of the heavy metal toxic ions contaminated aquatic environment. The surface of the sand was modified as depositing the nano-particles of manganese (i.e., manganese-modified natural sand: MMNS) and the mineral phase of manganese was perhaps depicted to be pyrolusite as indicated by the XRD analytical data. The d-spacings of quartz was significantly enhanced with the manganese modification indicated the manganese caused an apparent increase in basal spacing of sand structure. SEM images and the EDX analysis showed that manganese nano-particles are evenly distributed onto the surface of sand. The BET surface area of the MMNS was increased significantly. The amount of manganese aggregated was found to be 1002.6 mg/Kg of sand and the stability tests suggested that the nano-particles aggregated onto the sand surface are fairly stable within the pH region 3–10. Further, the removal behavior of this MMNS was employed for the attenuation of two important heavy metal toxic ions i.e., Pb(II) and Cu(II) in aqueous medium. The uptake of these two metal ions followed the Freundlich adsorption isotherm. The removal capacity of MMNS estimated with the Freundlich approximation was found to be 0.4596 mg/g for Cu(II) and 2.996 mg/g for Pb(II). Further, the 1000 times increase in ionic strength caused for relatively insignificant change in uptake of these two ions onto the solid surface points it a predominant strong chemical binding involved at the solid/solution interface. The column experiments and the breakthrough curves suggested that material possessed significantly high removal capacity i.e., 0.190 and 0.895 mg/g, respectively, for Cu(II) and Pb(II) even under the dynamic conditions.

A two-stage process consisting of an ozonizing chamber and an absorber containing a reducing agent solution was proposed to remove nitrogen oxides (NO x ) from exhaust gas. In the ozonizing chamber where the exhaust gas is treated by ozone, NO (the main component of NO x ) was oxidized to NO 2 , and in the next step, NO 2 was reduced to N 2 by sodium sulfide (Na 2 S) used as the reducing agent. The NO x removal efficiency obtained by this two-stage process was higher than 95%. It was found that about three fourth of sodium sulfide was consumed without reacting with NO x , and accordingly the amount of sodium sulfide required should be four times that of NO x to be removed. The problem regarding the emission of H 2 S from Na 2 S was deeply related to the pH of the reducing agent solution, which could be solved by adjusting the pH using a basic reagent (NaOH). The concentrations of NO 2 − and NO 3 − in the reducing agent solution after processing were analyzed, which showed that about 25% of the NO x removed from the exhaust gas was simply dissolved in the reducing agent solution, i.e., about 75% of the NO x removed was reduced to N 2 .

The behavior of the selective catalytic reduction of nitrogen oxides (NO x) assisted by a dielectric barrier discharge was investigated. The principal function of the dielectric barrier discharge in the present system is to generate ozone, which is continuously fed to a chamber where the ozone and NO-rich exhaust gas (NO forms the large majority of NOx) are mixed. In the ozonization chamber, a part of NO contained in the exhaust gas is oxidized to NO2, and then the mixture of NO and NO2 enters the catalytic reactor. The ozonization method proposed in this study was found to be more energy-efficient for the oxidation of NO to NO 2 than the typical nonthermal plasma process. The degree of NO oxidation was approximately equal to the amount of ozone added to the exhaust gas, implying that the decomposition of ozone into molecular oxygen was relatively slow, compared to its reaction with NO. When the exhaust gas was first treated by ozone to produce a mixture of NO and NO2, a remarkable enhancement in the catalytic reduction of nitrogen oxides was observed. Neither NO3 nor N2O5 was formed in the present system, but small amounts of ozone and N2O (less than 5 ppm) were detected in the outlet gas. © 2005 Elsevier B.V. All rights reserved.