Molar Ratio Of NH Research Articles

Synergistic effects of L-glutamine and inorganic nitrogen molar ratios enhance the induction of somatic embryogenesis of Pinus maximinoi H.E. Moore

Clonal breeding programs of Pinus maximinoi require the establishment of a robust somatic embryogenesis (SE) protocol to produce enough cell lines to accelerate the effective continuous deployment of elite planting stocks to research and commercial compartments. Somatic embryogenesis was induced from immature zygotic embryo explants enclosed in megagametophytes of P. maximinoi collected from two plantations located in different climatic conditions. Cones were collected during the winter months from July to August and the influence of seed family, cone collection date and culture medium formulation, with emphasis on the organic and inorganic nitrogen supply, were studied. Ammonium to nitrate molar ratios of 1:1 and 1:2 in modified Litvay’s medium (mLV) produced the highest numbers of extrusions, while a 1:4 ratio mostly produced unhealthy, non-embryogenic extrusions. The formation of a tissue showing a rapidly-proliferating, spiky morphotype was produced in a medium supplemented with 1.5 g/L of L-glutamine. Morphologically advanced cultures with nodular structures were produced in megagametophytes from both plantations in a 1:2 NH4+:NO3− medium regardless of L-glutamine supplementation levels. The optimal medium for P. maximinoi SE induction contained a 1:2 NH4+:NO3− molar ratio with 1.5 g/L L-glutamine. The synergy between the molar ratio of NH4+:NO3− and L-glutamine resulted in the highest numbers of extrusions. The overall inductive competence window for somatic embryogenic response in P. maximinoi was determined to be from the second week of July to the first week of August for both plantations. The “peak” period was in the fourth week of July 2022. The success of the SE technology in P. maximinoi seed families is determined by the optimal inductive competence window of the immature megagametophytes enclosing zygotic embryos and the chemical composition of the induction medium in terms of the ammonium to nitrate molar ratio and the concentration of the L-glutamine used.

Submerged macrophytes regulate diurnal nitrous oxide emissions from a shallow eutrophic lake: A case study of Lake Wuliangsuhai in the temperate arid region of China

Submerged macrophytes can increase oxygen concentrations of water and promote diel oxygen fluctuations, and this phenomenon is hypothesized to play a vital role in regulating nitrous oxide (N2O) emissions from eutrophic lakes. However, the effects of submerged macrophytes on N2O emissions in shallow eutrophic lakes remain poorly investigated. In this study, Lake Wuliangsuhai, a typical shallow eutrophic lake, was investigated to study the role of submerged macrophytes in regulating N2O emissions. We measured the N2O fluxes and related parameters through continual 72-h in situ diel monitoring in two sampling sections that covered dense submerged macrophyte areas and open water. In this study, the dissolved oxygen (DO) concentration of the water in the submerged macrophyte area exhibited significant diurnal variations, with significantly higher water oxygen concentrations than the open water area during the daytime. The N2O fluxes of Lake Wuliangsuhai ranged from 0.01 to 0.24 μmol m−2 h−1, with an average value of 0.11 μmol m−2 h−1. Moreover, significant diel variations in the N2O flux and net N2O production were observed in the submerged macrophyte areas, where the maximum N2O flux occurred at midday. The molar ratios of NH4+-N to oxygen (N/O ratio) of the water were responsible for the diel variations in the N2O production in the lake. However, the high oxygen concentration of the water was the major regulator of the N2O flux of Lake Wuliangsuhai. Therefore, submerged macrophyte restoration is significant not only for water quality improvement in shallow eutrophic lakes but also for N2O emission mitigation by increasing the DO concentration of the water.

Isotopic source analysis of nitrogen-containing aerosol: A study of PM2.5 in Guiyang (SW, China)

The source of fine particulate matter (PM2.5) has been a longstanding subject of debate, the nitrogen-15 isotope (δ15N) has been used to identify the major sources of atmospheric nitrogen. In this study, PM2.5 samples (n = 361) were collected from September 2017 to August 2018 in the urban area of Guiyang (SW, China), to investigate the chemical composition and potential sources of PM2.5. The results showed an average PM2.5 of 33.0 μg m−3 ± 20.0 μg m−3. The concentration of PM2.5 was higher in Winter, lower in Summer. The major water resolved inorganic ions (WSIIs) were Ca2+, NH4+, Na+, SO42−, NO3−, Cl−. Nitrogen-containing aerosols (i.e., NO3− and NH4+) suddenly strengthened during the winter, when NO3− became the dominant contributor. Over the sampling period, the molar ratio of NH4+/(NO3− + 2 × SO42−) ranged from 0.1 to 0.9, thus indicating the full fixation of NH4+ by existing NO3− and SO42− in PM2.5. The annual value of NOR was 0.1 while rised to 0.5 in Winter. The variations of NOR (Nitrogen oxidation ratio) (0.1–0.5) values suggest that the secondary formation of NO3− occurred every season and was most influential during the winter. The total particulate nitrogen (TN) δ15N value of PM2.5 ranged from −5.9‰ to 25.3‰ over the year with annual mean of +11.8‰ ± 4.7‰, whereas it was between −5.9‰ and 14.3‰ during the winter with mean of 7.0‰ ± 3.8‰. A Bayesian isotope mixing model (Stable Isotope Analysis in R; SIAR) was applied to analyze the nitrogen sources. The modeling results showed that 29%, 21%, and 40% of TN in PM2.5 during the winter in Guiyang was due to nitrogen-emissions from coal combustion, vehicle exhausts, and biomass burning, respectively. Our results demonstrate that biomass burning was the main contributor to PM during the winter, 80% of the air mass comes from rural areas of Guizhou border, this transport process can increase the risk of particulate pollution in Guiyang.

Electron buffer formation through coupling thiosulfate-dependent denitratation with anammox in a single-stage sequencing batch reactor

The combination of thiosulfate-dependent denitratation and anammox in a single-stage reactor provides a feasible way to improve total nitrogen removal. The molar ratios of NH4+/NO3− and S2O32−/NO3− were confirmed to be two key factors affecting the reactor performance. The optimal total nitrogen removal efficiency of 99.4% was achieved at NH4+/NO3− of 0.75 and S2O32−/NO3− of 0.85. The multiple thiosulfate oxidation pathways contribute to electron buffers generated in the system. A novel isotope labeling method using 15N was applied to reveal N transformation pathways and a 3-step model was proposed. The nitrate was first converted to nitrite or nitric oxide (NO) by sulfur-oxidizing bacteria. In the second step, both nitrite and NO were utilized by anammox bacteria. Finally, the nitrate generated from anammox could be removed using sulfur deposits as electron donors. The findings provide a potential solution for mainstream nitrogen removal.

A holistic and sustainable approach for recovery of phosphorus via struvite crystallization from synthetic distillery wastewater

Phosphorus is a limited resource and at the current usage, world’s reserves of phosphate rocks will soon get exhausted. The present study focuses on phosphorus recovery in the form of struvite from synthetic distillery wastewater. A response surface methodology was adopted to optimize process parameters (pH, concentration of phosphorus, ammoniacal nitrogen and magnesium) for struvite precipitation and removal of phosphate from wastewater. The optimized values for pH, molar ratio of NH4+:PO4−3 and Mg2+:PO4−3 were found to be 9.0, 2.28 and 1.72 respectively, resulting in 95% phosphate removal and 3306 mg/L yield of struvite. This study also investigated the effect of phenol and melanoidins on phosphate removal efficiency, purity and yield of the struvite. When concentration of phenol was increased from 0 to 9000 mg/L in a melanoidins free solution, the phosphate percentage removal decreased from 99% to 93% and the struvite crystal purity decreased from 96% to 62%. However, melanoidins containing wastewater showed 99%–88%, 93%–41% and 3700 mg/L to 2900 mg/L decrease in phosphate percentage removal, struvite purity and yield of precipitate respectively. Furthermore, dilution of distillery wastewater with seawater (source of magnesium) at 1:1.3 M ratio of P:Mg, serves as an economical and sustainable route for struvite crystallization. The pot trial experiments conducted with Brassica alba demonstrated promising fertilizer potential of the recovered struvite, comparable with commercially available fertilizers. The present study demonstrates that struvite crystallization from distillery wastewater is a sustainable and promising technology which could be applied efficiently for remediation of nutrient-rich wastewater and the recovered struvite can be employed as an alternate source of slow-release fertilizer for plants.

Seasonal study of stable carbon and nitrogen isotopic composition in fine aerosols at a Central European rural background station

Abstract. A study of the stable carbon isotope ratios (δ13C) of total carbon (TC) and the nitrogen isotope ratios (δ15N) of total nitrogen (TN) was carried out for fine aerosol particles (PM1) and was undertaken every 2 days with a 24 h sampling period at a rural background site in Košetice (Central Europe) from 27 September 2013 to 9 August 2014 (n=146). We found a seasonal pattern for both δ13C and δ15N. The seasonal variation in δ15N was characterized by lower values (average of 13.1±4.5 ‰) in winter and higher values (25.0±1.6 ‰) in summer. Autumn and spring were transition periods when the isotopic composition gradually changed due to the changing sources and ambient temperature. The seasonal variation in δ13C was less pronounced but more depleted in 13C in summer (-27.8±0.4 ‰) as compared to winter (-26.7±0.5 ‰). A comparative analysis with water-soluble ions, organic carbon, elemental carbon, trace gases and meteorological parameters (mainly ambient temperature) has shown major associations with the isotopic compositions, which has provided greater knowledge and understanding of the corresponding processes. A comparison of δ15N with NO3-, NH4+ and organic nitrogen (OrgN) revealed that although a higher content of NO3- was associated with a decrease in the δ15N of TN, NH4+ and OrgN caused increases. The highest concentrations of nitrate, mainly represented by NH4NO3 related to the emissions from biomass burning leading to an average δ15N of TN (13.3 ‰) in winter. During spring, the percentage of NO3- in PM1 decreased. An enrichment of 15N was probably driven by the equilibrium exchange between the gas and aerosol phases (NH3(g) ↔ NH4+(p)), which is supported by the increased ambient temperature. This equilibrium was suppressed in early summer when the molar ratios of NH4+/SO42- reached 2, and the nitrate partitioning in aerosol was negligible due to the increased ambient temperature. Summertime δ15N values were among the highest, suggesting the aging of ammonium sulfate and OrgN aerosols. Such aged aerosols can be coated by organics in which 13C enrichment takes place by the photooxidation process. This result was supported by a positive correlation of δ13C with ambient temperature and ozone, as observed in the summer season. During winter, we observed an event with the lowest δ15N and highest δ13C values. The winter event occurred in prevailing southeast air masses. Although the higher δ13C values probably originated from biomass-burning particles, the lowest δ15N values were probably associated with agriculture emissions of NH3 under low-temperature conditions (< 0 ∘C).

Characteristics of submicron particles coming from a big firecrackers burning event: Implications to atmospheric pollution

Firecrackers burning on different occasions all over the world is a short-term big source of fine particles and their precursors in the air. This study presents the real-time changes in concentrations, composition and characteristics of non-refractory particulate matter smaller than 1 μm aerodynamic diameter (NR-PM1), and black carbon (BC) during the Diwali festival, when a huge amount of firecrackers are burnt in India. Online measurements (1 min integration time) of organics, SO42−, NO3−, NH4+, and Cl− were performed using high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), and that of BC with seven wavelength aethalometer over a big urban city (Ahmedabad, 23.0ºN, 72.6ºE) in western India. A sharp increase (3–23 times higher) in the concentrations of all the measured species was observed on the evening of the Diwali that persisted overnight due to a combination of primary emissions and secondary formation of aerosol. Organics were the dominant contributor (∼85%) followed by SO42− (∼13%), Cl− (∼4%), NO3− (∼4%) and NH4+ (∼2%) to NR-PM1 on the Diwali night. Further, variations in H/C and O/C ratios before, during and after the Diwali suggest fresh emissions of primary organics on the Diwali night, and highly oxidized secondary organic formation on the next day. Aerosol neutralization ratio (ANR, defined as the molar ratio of NH4+ to sum of SO42−, NO3− and Cl−), an indicative of aerosol acidity, reduced to as low as 0.1 on the Diwali night, which has implications to short-term acute atmospheric air pollution.

Effects of Atmospheric Dry Deposition on External Nitrogen Supply and New Production in the Northern South China Sea

The South China Sea (SCS) is one of the world’s largest oligotrophic marginal seas. Increases in biomass and primary production in the surface layer of the northern SCS are affected by anthropogenic aerosol use among north Asian peoples. The seasonal variation of dry deposition and its contribution to new production in the ocean are vital to determining the effect that such dry deposition has on the biogeochemical cycle of the SCS. This study collected 240 samples of total suspended particles at Dongsha Island in the northern SCS from April 2007 to March 2009; the major ions and water-soluble nitrogen species in the samples were analyzed. The analysis results indicated that the concentration distributions of major water-soluble ions and nitrogen species in total suspended particles exhibited significant seasonal (source) variation. The north-east monsoon seasons (autumn to spring) brought relatively high concentrations because most air masses during this period arrived from the northern continental region. We found that the concentration of nitrogen species shows a latitude distribution, gradually decreasing from north to south. In addition, this study also discovered that the ratio of organic nitrogen to total dissolved or water-soluble nitrogen also varies in a similar manner, resulting in a concentration of <20% for locations north of 30° N and >30% for those south of 30° N. Aerosols at Dongsha Island mainly comprised sea salt; however, significant chloride depletion was observed during the north-east monsoon season. The molar ratio of NH4+ to non–sea salt (NSS) sulfate (nss-SO42−) was 0.8, indicating that the amount of artificially produced NH4+ in the region was insufficient for reaction with nss-SO42−. Therefore, NH4+ was mainly present in the form of NH4HSO4. The fluxes of water-soluble inorganic nitrogen (WSIN) and water-soluble organic nitrogen (WSON) within the region were 23 ± 13 and 27 ± 15 mmol m−2 y−1, respectively. The new production converted from atmospheric water-soluble nitrogen species in the northern SCS was estimated to be 0.52–0.81 mmol C m−2 d−1. This flux made about 5.6–8.7% (the global average was about 3.5%) contribution to the primary production (9.24 mmol C m−2 d−1) of the SCS surface water. This result indicates that the ocean’s external nitrogen supply, provided by anthropogenic aerosols, is vital for the biogeochemical cycle in Asian marginal seas, particularly the northern SCS.

The optimization of microalgal culturing in liquid digestate after struvite precipitation using gray relational analysis.

Liquid digestate (LD) is highly turbid and contains ammonium (NH4+-N), which negatively influences microalgal growth. Therefore, a method of reducing LD turbidity and NH4+-N content is proposed, using struvite precipitation. To obtain struvite precipitation supernatant with an ideal UV transmittance, NH4+-N concentration, and N/P ratio for microalgal growth, the effects of pH and the molar ratio of NH4+/Mg2+/PO43- were studied. Results show that the optimal NH4+/Mg2+/PO43- molar ratio was 1:1.5:1.5, with a pH value of 8.5, following NaOH addition. Gray relational analysis (GRA) was applied to obtain a relative gray scale for the evaluation of multiple outputs. Results show that Chlorella regularis FACHB-1068 was the optimal microalgae species to support growth in the struvite precipitation supernatant. Using struvite precipitation and treatment with cultured C. regularis FACHB-1068 for 7days, the removal efficiencies of NH4+-N, PO43--P, and COD in LD were 96.52, 99.33, and 35.30%, respectively.

Enhanced phosphorus removal using acid-treated magnesium slag particles.

Magnesium-enriched magnesium slag particles (MSPs) can be used as an adsorption substrate as well as the magnesium source for struvite precipitation. In this study, an HCl treatment was used to enhance MSPs for phosphorus removal. After soaking in 1mol/L HCl, an 11.27% decrease in median diameter (D50) and a 6.73% increase in specific surface area were observed when compared with the original MSPs. The improvement of the MSP surface properties resulted in 188.96mg/kg increase in the PO43- adsorption capacity. Irrespective of HCl treatment, the phosphorus adsorption process followed the Dubinin-Radushkevich (D-R) model much more accurately than the Langmuir and Freundlich equations with correlation coefficients higher than 0.94. The adsorption free energy obtained through the D-R model revealed a 9.75% decrease after HCl treatment. Sequential fraction extraction results indicated that 96% of the Mg2+ released from the HCl-treated MSPs came from acid-soluble magnesium (exchangeable and carbonate-bound). Mg2+ obtained from HCl-treated solutions provided a reliable magnesium source for struvite precipitation. The PO43- removal rate can reach 53.63% with the optimal pH value of 10.0 and molar ratio of NH4+ to PO43- of 1:1. Struvite precipitation and adsorption can simultaneously occur in HCl-treated MSP solution. It contributed 63.19% to the overall PO43- removal and is a major contributor compared with adsorption. Thus, HCl treatment greatly enhanced the potential of MSPs for phosphorus removal due to an improved adsorption capacity and is a reliable Mg2+ source for struvite precipitation.

Inorganic ions in ambient fine particles over a National Park in central India: Seasonality, dependencies between SO42−, NO3−, and NH4+, and neutralization of aerosol acidity

Twelve hour integrated ambient fine particles (PM2.5) were collected over an Van Vihar National Park (VVNP), in Bhopal, Central India. Samples were collected on filter substrates every-other-day for two years (2012 and 2013). In addition to PM2.5 mass concentration, water soluble inorganic ions (WSIIs) were also measured. Further, on-site meteorological parameters including temperature, wind speed, wind direction, relative humidity, rainfall and atmospheric pressure were recorded. During 2012, the average PM2.5 concentration was 40 ± 31 μgm−3 while during 2013 it was 48 ± 50 μgm−3. Further, in about 20% of the samples the 12 h integrated fine PM mass exceeded the daily (24 h) average standards (60 μgm−3). This observation suggests that the PM2.5 mass concentration at the study site is likely to be in violation of the National Ambient Air Quality Standard (NAAQS), India. During the study period the sum of three major ions (SO42−, NO3−, and NH4+) accounted for 19.4% of PM2.5 mass on average. Air parcel back trajectory ensembles revealed that emissions from thermal power plants were likely to be the main regional source of particulate SO42− and NO3− measured over VVNP. Further, local traffic activities appeared to have no significant impact on the concentrations of PM2.5 and its WSIIs constituents, as revealed by a day-of-the-week analysis. PM2.5 mass, SO42−, NO3−, and NH4+ showed a pronounced seasonal trend with winter (Jan, Feb) and post-monsoon (Oct, Nov, Dec) highs and pre-monsoon (Mar, Apr, May) and monsoon (Jun, Jul, Aug, Sep) lows, during both 2012 and 2013. Further, when the sum of SO42− and NO3− constituted greater than 90% of water soluble inorganic anions by mass, they were linearly dependent on one another and moderately anti-correlated (r2 = 0.60). The molar ratios of NH4+ and non-sea salt SO42− were examined to understand the aerosol neutralization mechanisms and particulate NO3− formation. An assessment of these ratios and subsequent analyses suggested that in NH4+ rich samples, NO3− and non-sea salt SO42− were almost entirely neutralized by NH4+. In NH4+ poor samples, in addition to NH4+ non-sea salt K+ played a role in acidity neutralization. These observations are unlike those reported for PM10 and total suspended particles (TSP) over other locations in India, where mineral aerosol species (specifically Ca2+) played an important role in neutralizing acidic species. Additionally, both during 2012 and 2013, the aerosol acidity showed a pronounced seasonality - the aerosol was alkaline or near-neutral during the winter and post-monsoon seasons, while during the pre-monsoon and monsoon seasons it was acidic.

Influence of Ammonium Ion on Nitrolysis of 3,7-Dinitro-1,3,5,7-tetraazabicyclo[3,3,1]nonane (DPT)

Based on the two mechanisms of 3, 7-dinitro-1, 3, 5, 7-tetraazabicyclo[3,3,1] nonane (DPT) nitrolysis via HNO3-NH4NO3 or HNO3, the effects of NH4+ in nitrolysis of DPT were studied by experiment and theoretical calculation. The effect of NH4+ on the yield of HMX was studied with adding the ammonium salts including (NH4)2HPO4, (NH4)2SO4 and CH3COONH4 to nitrate solution system. Results show that the above-mentioned ammonium salts can improve the yield of HMX to 41.5%, 37.4% and 20.7%, respectively. Their function is similar to NH4NO3. In different nitric acid-ammonium salt systems, when the molar ratio of NH4+ and DPT is close to 10, the yield of HMX reaches a maximum value of 56.3%, 52.2% and 35.5%, respectively. Results of the nitrolysis of DPT in nitric acid-ammonium salt systems and nitric acid-nitrate system are compared, finding that NH4+ plays a dominant role in improving the yield of HMX. The reaction mechanism of NH4+ in the nitrolysis process of DPT is theoretically explained by the density functional theory (DFT), deriving that the activation energy of DPT nitrolysis in HNO3/NH4+ is 133.95 kJ·mol-1, lower than 376.73 kJ·mol-1 in HNO3.

Community Structures and Distribution of Anaerobic Ammonium Oxidizing and nirS-Encoding Nitrite-Reducing Bacteria in Surface Sediments of the South China Sea

Anaerobic ammonium oxidation (anammox) and denitrification are two important processes responsible for nitrogen loss; monitoring of microbial communities carrying out these two processes offers a unique opportunity to understand the microbial nitrogen cycle. The aim of the current study was to characterize community structures and distribution of anammox and nirS-encoding nitrite-reducing bacteria in surface sediments of the northern South China Sea (SCS). The consistent phylogenetic results of three biomarkers of anammox bacteria, including 16S rRNA, hzo, and Scalindua-nirS genes, showed that Scalindua-like bacteria were the only anammox group presenting in surface sediments of the SCS. However, a relatively high micro-diversity was found within this group, including several SCS habitat-specific phylotypes, Candidatus "Scalindua zhenghei". Comparing to 16S rRNA gene, hzo and Scalindua-nirS genes provided a relatively higher resolution to elucidate anammox bacteria. For the nirS-encoding nitrite-reducing bacteria, the detected nirS gene sequences were closely related to various marine nirS denitrifiers, especially those which originated from coastal and estuarine sediments with a much higher diversity than anammox bacteria. Anammox bacterial communities shifted along with the seawater depth, while nirS-encoding nitrite-reducing bacteria did not. Although nirS-encoding nitrite-reducing bacteria have a much higher abundance and diversity than anammox bacteria, they showed similar abundance variation patterns in research sites, suggesting the two microbial groups might be affected by the similar environmental factors. The significant correlations among the abundance of the two microbial groups with the molar ratio of NH4 (+) to (NO2 (-) + NO3 (-)), pH, and organic matters of sediments strongly supported this hypothesis.

Relationship between stability degree and chemical indices of livestock manure composts

Principal chemical indices of compost associated with compost stabilization were investigated using relationship between stability degree (SD) and chemical indices including pH, electrical conductivity (EC), total C, extractable C, decomposability, total N, NH4 +, NO3 −, molar ratio of NH4 + to NO3 −, C/N, total P, and soluble P of various composts. Compost SD was positively (p<0.05) correlated with pH and C/N, and negatively (p<0.05) with EC, total N, and molar ratio of NH4 + to NO3 −. However, the correlation with pH, C/N, and total N were in contradiction to other studies that reported an opposite relationship to ours, probably due to different properties of initial composting materials. Therefore, the present study in conjunction with other studies suggest that EC and the molar ratio of NH4 + to NO3 − are the chemical indices closely associated with stabilization of composts regardless of composting materials.

Mitigation of signal suppression caused by the use of trifluoroacetic acid in liquid chromatography mobile phases during liquid chromatography/mass spectrometry analysis via post‐column addition of ammonium hydroxide

A method has been developed to reduce the mass spectrometric ion signal suppression associated with the use of TFA as an additive in LC mobile phases. Through post-column infusion of diluted NH(4)OH solution to LC eluents, the ammonium ion introduced causes the neutral analyte-TFA ion pair to dissociate which consequently releases the protonated analyte as free ions into the gas phase (through regular electrospray ionization mechanisms). An ion signal improvement from 1.2 to 20 times for a variety of compounds had been achieved through the application of this method. The molar ratios of NH(4)OH:TFA which result in a reduction of signal suppression were determined to be between 0.5:1 and 50:1. In addition, it was shown that this NH(4)OH infusion method could reduce the level of doubly-charged species and the product ions formed via in-source collision. The use of diluted NH(4)OH solution is favorable since it is compatible with mass spectrometry analysis, and it is applicable in both positive and negative-ion generation mode.

Preparation of amorphous aluminium ammonium phosphates

ABSTRACTA method for obtaining of amorphous aluminium ammonium phosphates is developed. The statistical program STATISTICA 9 is used for planning and evaluation of the experiments. Research is carried out according to the Box-Behnken model for the following values of independent variables (input factors): pH: 6.0 ± 2; concentration of reagents: 40 ± 10 wt%, molar ratio of NH4+:PO43- in substrates (2 ± 1:1) i.e. Al3+:NH4+:PO43- (0.66:1-3:1). On the basis of this research, process parameters are determined, in which materials with the expected physicochemical properties (chemical composition, specific surface area, oil absorption number) can be obtained.

A simple template-free approach to TiO2 hollow spheres with enhanced photocatalytic activity

Mesporous anatase-phase TiO(2) hollow spheres with high photocatalytic activity were prepared by hydrothermal treatment and self-transformation of amorphous TiO(2) solid spheres in an NH(4)F aqueous solution. The prepared samples were characterized by X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, N(2) adsorption-desorption isotherms and UV-vis absorption spectroscopy. The photocatalytic activity was evaluated by photocatalytic oxidation decomposition of acetone in air under UV irradiation. It is found that F(-) plays an essential role in the formation of TiO(2) hollow spheres. F(-) not only induces the hollowing of TiO(2) solid spheres, but also promotes the crystallization of anatase TiO(2) nanocrystals. A possible formation mechanism for the TiO(2) hollow spheres by localized Ostwald ripening or chemically induced self-transformation is proposed based on the experimental observations. Furthermore, the molar ratios of NH(4)F to TiO(2) (R) exhibit a significant influence on the morphology and photocatalytic activity of the TiO(2) samples. The photocatalytic activity of the samples prepared in the presence of NH(4)F is higher than that of TiO(2) sample prepared in pure water and commercial Degussa P25 (P25) powders. Especially, the TiO(2) hollow spheres prepared at R = 1 show the highest photocatalytic activity and the specific rate constant S(k) exceeds that of P25 by a factor of more than two.

Struvite Recovery from Swine Waste Biogas Digester Effluent through a Stainless Steel Device under Constant pH Conditions

To investigate the struvite precipitation under constant and non-constant pH conditions and to test a stainless steel device under different operating regimes to maximize the recovery of struvite. The molar ratio of NH4+: Mg2+: PO4(3-) was adjusted to 1: 1.2: 1.2 and pH was elevated to 9.0. The absorbance measurement was used to trace the process of struvite crystallization. Wastewater and precipitate analysis was done by standard analytical methods. The pH constant experiment reported a significantly higher struvite precipitation (24.6 +/- 0.86 g) than the non-constant pH experiment (19.8 +/- 1.86 g). The SAR ranged from 5.6 to 8.2 g m(-2) h(-1) to 3.6-4.8 g m(-2) h(-1) in pH constant and non-constant experiments, respectively. The highest struvite deposit on the device was found in regime 3 followed by in regimes 2 and 4. The highest PO4(3-) (97.2%) and NH4+ (71%) removal was reported in the R1 regime. None of the influent Cu2+ or Zn2+ was precipitated on the device. A higher struvite yield is evident in pH constant experiments. Moreover, the stainless steel device facilitates the isolation of heavy metal free pure (around 96%) struvite from swine waste biogas digester effluent contaminated with cu2+ and Zn2+ and the highest yield is attainable with the device operating at 50 rpm with agitation by a magnetic stirrer.

Rapid reduction in gelation time and impregnation of hydrophobic property in the tetraethoxysilane (TEOS) based silica aerogels using NH 4F catalyzed single step sol–gel process

The experimental results on the synthesis and physical properties of tetraethoxysilane (TEOS) based superhydrophobic silica aerogels, obtained by single step sol–gel process, are reported and discussed. Superhydrophobic silica aerogels were prepared by varying the molar ratio of MeOH/TEOS ( M) from 11 to 275, molar ratio of NH 4F/TEOS ( A) from 1.2 to 9.6 and concentration of NH 4F from 0.001 to 1 M, respectively. All the alcogels were dried under supercritical conditions. The remarkable results were obtained in terms of drastic reduction in the gelation time which is less than 1 min, using single step sol–gel process. Further, the obtained aerogels are hydrophobic ( θ = 155°) without use of any hydrophobic reagents. The obtained hydrophobic property of the aerogels was improved using mono, di and tri-functional methoxysilanes as co-precursor such as, trimethylmethoxysilane (TMMS), dimethyldimethoxysilane (DMMS) and methyltrimethoxysilane (MTMS), respectively. It was observed that as the order of functional groups of methoxysilane decreases, the contact angle of the water droplet on the aerogel surface increases, indicating the aerogel become more hydrophobic. The highest contact angle of ( θ = 168°) was observed for trimethylmethoxysilane as a co-precursor. The aerogels were characterized by bulk density, volume shrinkage, porosity, optical transmission and thermal conductivity measurements. The effect of humidity on the aerogel samples was studied using programmable environmental test chamber. The hydrophobicity of the aerogels was quantified by contact angle measurements and FTIR studies while microstructural studies were done using Transmission Electron Microscopy (TEM).

Research on the hygroscopic properties of aerosols by measurement and modeling during CAREBeijing‐2006

To further understand and improve air quality for the 2008 Beijing Olympic Games, the Campaigns of Air Quality Research in Beijing and Surrounding Region 2006 (CAREBeijing‐2006) were carried out in an urban and a suburban area from 10 August to 12 September 2006. As a part of an intensive series of measurements, the optical and physical properties of the aerosol were monitored together with identification of the chemical species involved. A method to calculate the hygroscopic factor for aerosol scattering f(RH), defined as the ratio of the aerosol scattering coefficient at given relative humidity (RH) to that at 35% RH, is proposed on the basis of the optical parameters. Over the course of the study f(80%) = 1.63 ± 0.19. The observation that the molar ratio of NH4+ to (2*SO42− plus NO3−) was very close to 1 implies that the chemical form of the sulfate aerosol may be ammonium sulfate (NH4)2SO4 and that nitrate possibly existed as NH4NO3. On the basis of the measurements of size‐resolved chemistry, RH, and published functional relationships between the chemical composition and water uptake, the aerosol scattering coefficients could be calculated by the Mie theory for the major particle species (ammonium sulfate, ammonium nitrate, sodium chloride, particulate organic matter, elemental carbon, and residual material). This retrieval method synthesizes the high temporal resolution of mass concentration measurements and low temporal resolution size distribution for water soluble ionic components and carbonaceous aerosols. A local closure experiment is obtained by comparing the measured f(RH) with model calculations using aerosol chemical composition and chemical thermodynamics. Results from the closure study show that the measured and the predicted values of f(RH) agree within measurement uncertainties.