Toxic Ammonia Research Articles

Application of photosynthetic microalgae as efficient pH bio-stabilizers and bio-purifiers in sustainable aquaculture of <i>Clarias gariepinus</i> (African catfish) fry

Chlorella lewinii LC172265 and Scenedesmus dimorphus NIES-93 were grown with BG-11 medium and then transferred to fish seedlings' farm and the effects on changes in the pH, nitrite, total ammonia nitrogen and toxic ammonia were studied. Inoculation of the ponds with C. lewinii, S. dimorphus and the combined culture of C. lewinii and S. dimorphus significantly reduced the rise in the pH of the ponds (p<0.05). With these three cultures, the pond pH increased from 6.3±0.03 to only 6.5±0.2, 6.7±0.6 and 6.4±0.1 respectively within a period of 240 hours, as against control pond's pH which increased from 6.3±0.03 to 9.0±0.1 within the same period. Furthermore, inoculation with S. dimorphus reduced the nitrite concentration in the ponds to zero on the 144th hour and the concentration remained zero throughout the experiment. This was closely followed by the combined culture of C. lewinii and S. dimorphus which reduced the nitrite concentration to zero at 240th hour while C. lewinii was the least in nitrite removal. Toxic ammonia was also zeroed by the combined culture of C. lewinii and S. dimorphus at 144th hour of experiment which was followed by C. lewinii (at 192nd hour). Aquaculture ponds co-cultured with microalgae witnessed a maximum fry death rate of 40% which was much lower than 80% death rate observed in the control ponds. These results show that C. lewinii and S. dimorphus are very efficient in sustaining the quality of aquaculture water, and thus prolonging the length of time water can be used before changing.Keywords: nitrogen removal, ammonia, nitrite, fishery, fish pond

Application of the phycoremediation process for tertiary treatment of landfill leachate and carbon dioxide mitigation

Landfill leachate contains a high concentration of organic and inorganic compounds, toxic heavy metals (THMs), ammonia and bio-refractory compounds. Hence, the remediation of landfill leachate is a challenge for environmental scientists and practitioners. Present work aims to study the application of phycoremediation process as tertiary treatment for pre-treated landfill leachate combined with carbon biosequestration in laboratory-scale photobioreactor (PBR) which can be easily scaled-up for on-site application. Real leachate collected from solid waste dumpsite was initially treated with coagulation and air-stripping process. The pre-treated leachate was innoculated with Chlorella pyrenoidosa and subsequently exposed different CO2 concentration to determine the optimum CO2 concentration for maximum biomass productivity. The results of the optimisation study were applied to a laboratory-scale PBR. The pre-treatment process effectively reduced the biologically inhibitive compounds and colour present in the raw landfill leachate which made it suitable for microalgae cultivation. Maximum biomass productivity of C. pyrenoidosa cultivated in pre-treated landfill leachate was observed when exposed to 10% CO2. The phycoremediation process in PBR effectively consumed 91% of DOC, 86% of TN, 90% of NH4-N and 96% of phosphates from pre-treated landfill leachate and also 0.26 g/L/day of CO2 from the air to produce 2.9 g/L of biomass. Results of the study indicated that using phycoremediation for tertiary treatment of landfill leachate can be a sustainable option as residual nutrients were consumed by microalgae for beneficial biomass production and provided superior quality effluent with minimal environmental hazards.

Ecofriendly calcium phosphate and calcium bicarbonate biogrouts

An important direction of construction biotechnology is production and application of the biogrouts to decrease the hydraulic conductivity of soil or fractured rocks. The most popular biogrout is a mixture of calcium chloride, urea, and either ureolytic bacteria or enzyme urease. A disadvantage of this biogrout is the release of a large quantity of toxic ammonia to air, as well as harmful ammonium and hydroxide ions to water. The aim of this study was evaluation of two new biogrouts that release less of harmful by-products to environment. First biogrout was a mixture of acidified hydroxyapatite solution from the bone powder with an addition of two times less urea that is used in conventional biogrout. Final pH was 7. Second biogrout was a solution of calcium bicarbonate produced from chalk powder and carbon dioxide with an addition of urea and acidotolerant ureolytic bacteria. This biogrout released to environment four times less ammonium and ammonia than conventional biogrout. Final pH was 8. Precipitation of about 2 g of calcium carbonate per kg of the cracked stone diminished the water seepage through the specimen by three orders of magnitude. Geotechnical or environmental engineering applications of these environmentally friendly biogrouts are limited by the consumption of a large volume of the grouting solution. It is due to low concentration of dissolved calcium, about 200–400 g m−3, in these liquid biogrouts. So, these biogrouts could be most effective for the sealing and strengthening of the materials with low porosity such as the fractured rocks or cracked concrete.

Two-dimensional delafossite cobalt oxyhydroxide as a toxic gas sensor

To the chain of development of 2D materials, recently synthesized ultrathin cobalt oxy-hydroxide (CoOOH) nano sheets gain potential interest due to its structural, electronic and other properties. We have studied the interaction mechanism of two toxic gases hydrogen peroxide (H2O2) and ammonia (NH3) adsorbed over 2D CoOOH to understand the role of 2D CoOOH as a toxic gas sensor. We employ first principles based dispersion corrected density functional calculations to study the sensing behavior of 2D CoOOH towards H2O2 and NH3 by calculating adsorption energy, electronic band structure, density of states (DOS) and work function. The electronic band structure, DOS and work function of 2D CoOOH are modulated after adsorption of H2O2 and NH3 molecules. Adsorption of gas molecules confirms the sensing behavior of 2D CoOOH towards these molecules and depicts its use in a sensing device. The full phonon dispersion curves and phonondensity of states reveal the dynamical stability of 2D CoOOH. The calculated adsorption energy of H2O2 and NH3 molecules is −0.532 and −0.460 eV respectively which indicates the strong physisorption of these gases over 2D CoOOH. The ultrafast recovery time of 1239 and 1203 ns respectively were found for H2O2 and NH3 on 2D CoOOH. The work function which is 6.29 eV found for 2D CoOOH, decreases to 5.63 eV for H2O2 as it follows the reduction process on 2D CoOOH, and increases to 6.44 eV for NH3 molecules as it acts as oxidation gas on CoOOH. Our study reveals that the 2D CoOOH can be a better sensor for the H2O2 and NH3 gases than some traditional two-dimensional materials.

Identification of a novel function of the silkworm integument in nitrogen metabolism: Uric acid is synthesized within the epidermal cells in B. mori

During nitrogen metabolism, animals convert toxic ammonia to less toxic forms. Uric acid (UA) is an end product of this process in terrestrial insects. In lepidopteran larvae, a large amount of UA is stored in the integument via a phenomenon known as storage excretion. Physiologically, integumental UA plays crucial roles as a barrier against sunlight and as a white pigment for larval pigmentation patterns. Conventionally, UA is thought to be synthesized in the fat body, the insect equivalent of the liver of vertebrates, and to be transported to the epidermis via the hemolymph. Here, we reconsidered the conventional theory by a mosaic analysis targeting genes governing UA synthesis, using CRISPR/Cas9 mutagenesis and a traditional genetic method in Bombyx mori. Notably, we observed mosaic larvae in which the integument comprised both UA-containing white and UA-lacking translucent areas, indicating that UA synthesis in the epidermis is indispensable to the accumulation of a large amount of highly insoluble UA in the epidermis. Our results thus provide a genetic basis for storage excretion wherein lepidopteran insects use nitrogenous waste to adapt to their environment.

The way to improve the efficiency of the neutralization system of nitrogen oxides of diesel internal combustion engines and its efficiency

The article analyzes the work of the neutralization systems of nitrogen oxides used on modern trucks with diesel ICE. It is stated that the modern development of technologies for electronic fuel injection and catalytic neutralization of combustion products provides an opportunity to implement the processes of neutralization of nitrogen oxides with an efficiency up to 90%. The most effective method to reduce the exhaust emissions of diesel engines is to purify exhaust gases in the car exhaust system using the SCR-NH3 method. A significant drawback of this system is the presence of a toxic substance ammonia regulated by Regulation No. 49-06. Regulation No. 49-06 provides for the control in operation of emissions of nitrogen oxides by the on-board diagnostics system by introducing emission limit values, but monitoring of ammonia emissions in operation is not provided. It is noted that the state sanitary standards of the Russian Federation and the environmental monitoring service, prescribe in regulatory documents the control of the limit of emissions of harmful substances of ammonia and nitrogen oxides with MPCss 0.04 mg / m3. Thus, an identical approach to limiting these emissions is provided. In order for the purification system to function effectively with ammonia and to support the neutralization reaction, it is necessary to adjust the purification system and maintain the optimum temperature range of operation. It is noted that to ensure a high activity of reduction reactions, it is necessary to adjust the cleaning system and maintain the optimum temperature range of operation, the temperature is about 350-550 ° C. In this regard, the possibility of refining the neutralization system by the injection of urea into the cylinder of an internal combustion engine at the expansion stroke to neutralize nitrogen oxides and reduce ammonia emissions, as well as to increase the efficiency of a diesel engine, using the heat of exhaust gases by creating high pressure in the working cylinder work and boost pressure. When dosing urea solution having a high heat capacity through the nozzle and the subsequent process of expansion of exhaust gases, the temperature value in the cylinder of the internal combustion engine reaches the required value for the reduction reaction. High temperature, ensuring the removal of the reaction products, contributes to the high efficiency of maintaining the process of neutralization of NOx. Intra-cylinder cooling of the engine with urea-injected water solves the problem of thermal stress of the parts of the cylinder-piston group of a highly forced internal combustion engine without a significant increase in heat loss of the internal combustion engine.

Using meta-omics of contaminated sediments to monitor changes in pathways relevant to climate regulation.

Microbially mediated biogeochemical processes are crucial for climate regulation and may be disrupted by anthropogenic contaminants. To better manage contaminants, we need tools that make real-time causal links between stressors and altered microbial functions, and the potential consequences for ecosystem services such as climate regulation. In a manipulative field experiment, we used metatranscriptomics to investigate the impact of excess organic enrichment and metal contamination on the gene expression of nitrogen and sulfur metabolisms in coastal sediments. Our gene expression data suggest that excess organic enrichment results in (i) higher transcript levels of genes involved in the production of toxic ammonia and hydrogen sulfide and (ii) lower transcript levels associated with the degradation of a greenhouse gas (nitrous oxide). However, metal contamination did not have any significant impact on gene expression. We reveal the genetic mechanisms that may lead to altered productivity and greenhouse gas production in coastal sediments due to anthropogenic contaminants. Our data highlight the applicability of metatranscriptomics as a management tool that provides an immense breadth of information and can identify potentially impacted process measurements that need further investigation.

Hyper-ammonia stress causes induction of inducible nitric oxide synthase gene and more production of nitric oxide in air-breathing magur catfish, Clarias magur (Hamilton).

Nitric oxide (NO) is an important signalling molecule that plays diverse physiological functions in several vertebrates including that of adaptation to various stressful stimuli. The air-breathing magur catfish (Clarias magur) is known to tolerate a very high external ammonia (HEA) stress in its natural habitats. We report here the possible induction of inducible nitric oxide (inos) gene and more generation of NO in magur catfish exposed to HEA. Exposure to HEA (25mM NH4Cl) for 14days led to the higher accumulation of NO in different tissues of magur catfish and also more efflux of NO from the perfused liver of NH4Cl-treated fish as a consequence of high build of toxic ammonia in body tissues. More synthesis and accumulation of NO in body tissues was associated with the induction of iNOS activity, which otherwise was not detectable in control fish. The stimulation of iNOS activity in HEA exposed fish was mainly due to induction of inos gene as evidenced by more expression of inos mRNA and also more abundance of iNOS protein in different tissues of magur catfish. Immunocytochemical analysis indicated the zonal specific expression of iNOS protein in different tissues of magur catfish. The augmentation of iNOS in the fish under HEA could be an adaptive strategy of the fish to defend against the ammonia stress through the generation of NO. Therefore, the present finding identifies the potential role of iNOS to enhance the adaptive capacity and survivability of catfish under various adverse environmental and pathological conditions that it faces in its natural habitats.

Fast response paper based visual color change gas sensor for efficient ammonia detection at room temperature

We show that a cheap, disposable type rapid paper sensor (working at room temperature) can be made using perovskite halide CH3NH3PbI3 (MAPI) to detect presence of the toxic ammonia gas (NH3)by just color change, where the black colored MAPI film (on the paper) changes to yellow color in presence of a very low concentration of NH3 gas. The sensor can detect presence of NH3 gas in open or closed atmosphere down to around 10 ppm with a response time of nearly 10 sec which decreases to few seconds when the concentration exceeds 20 ppm. The easy to fabricate sensor paper being a visual sensor does not need any other extra equipment for its operation. The sensor is not sensitive to moisture with RH upto 90% and does not also respond to gases like Methane (CH4), Nitrous Oxide (N2O), Carbon dioxide (CO2) etc in the test chamber each up to a concentration of 500 ppm. Conversion/decomposition of MAPI to PbI2 on exposure to NH3 has been proposed as the mechanism of color change and the mechanism has been established using a collection of techniques like XRD, EDX, UV-Visible absorption and Photo Luminescence.

Ionic Liquid‐based Microchannels for Highly Sensitive and Fast Amperometric Detection of Toxic Gases

AbstractIonic liquid (IL)‐based microchannels sensors have been fabricated and employed for the detection of toxic ammonia (NH3) and hydrogen chloride (HCl) gases, with enhanced sensitivity and response times compared to conventional electrodes. Electrochemical techniques were employed to understand the behaviour of these highly toxic gases in two ionic liquids, [C4mpyrr][NTf2] and [C2mim][NTf2], on a gold modified microchannels electrode. The limits of detection (LODs) obtained in [C4mpyrr][NTf2] for NH3 (3.7 ppm) and in [C2mim][NTf2] for HCl (3.6 ppm) were lower than the current Occupational Safety and Health Administration Permissible Exposure Limit (OSHA PEL) for the two gases (25 ppm for NH3 and 5 ppm for HCl). The response time of the sensor is 15 s with a sensitivity of 143 nA ppm−1 and 14 nA ppm−1 for HCl and NH3, respectively. These results demonstrate the superiority of IL‐based microchannels sensors for detecting toxic gases, when compared to commercially available sensors or traditional IL‐based sensor designs, where high sensitivity or fast response time is still a challenge.

Extracellular urease from Arthrobacter creatinolyticus MTCC 5604: scale up, purification and its cytotoxic effect thereof

Urease is a potent metalloenzyme with diverse applications. This paper describes the scale up and purification of an extracellular urease from Arthrobacter creatinolyticus MTCC 5604. The urease production was scaled-up in 3.7L and 20L fermentor. A maximum activity of 27 and 27.8U/mL and a productivity of 0.90 and 0.99 U/mL/h were obtained at 30h and 28h in 3.7 and 20L fermentor, respectively. Urease was purified to homogeneity with 49.85-fold purification by gel filtration and anion exchange chromatography with a yield of 36% and a specific activity of 1044.37 U/mg protein. The enzyme showed three protein bands with molecular mass of 72.6, 11.2 and 6.1kDa on SDS-PAGE and ~ 270kDa on native PAGE. The cytotoxic effect of urease was assessed in vitro using cancer cell lines (A549 and MG-63) and normal cell line (HEK 293). Urease showed its inhibitory effects on cancer cell lines through the generation of toxic ammonia, which in turn increased the pH of the surrounding medium. This increase in extracellular pH, enhanced the cytotoxic effect of weak base chemotherapeutic drugs, doxorubicin (50µM) and vinblastine (100µM) in the presence of urease (5U/mL) and urea (0-4mM) significantly.

The role of liver in metabolism: an updated review with physiological emphasis

Liver plays an essential role in metabolism and has an important role in preserving and regulating the levels of lipid, glucose in the body as well as energy metabolism. Among the important functions performed by the liver is maintaining of blood glucose levels under different conditions through group of processes included; glycolysis, glycogenesis, glycogenolysis, gluconeogenesis. The absorbed free fatty acids and those derived from the adipose tissue reach the liver and are utilized for energy, membrane synthesis, or stored as triglyceride. In addition, the liver has a crucial role in keeping homeostasis of body level of cholesterol. Regarding protein metabolism, urea cycle occurs in the liver through the action of urea cycle enzymes to produce urea in order to get rid of the toxic ammonia. In the liver, cholesterol is utilized for bile acids synthesis through a complicated process. These bile acids are considered essential in order to absorb and transport of lipid-soluble vitamins dietary and fat in the diet as well as clearance of drugs, toxic substances and xenobiotics. Adding to these hepatic functions is hepatic detoxification where liver metabolizes a various type of drugs to make soluble execretable compounds. In conclusion, the liver has so important metabolic functions which if impaired will resulted in many liver diseases and might progress to more dangerous conditions such as liver fibrosis or cirrhosis.

Rh protein is key for crab waste disposal

The seabed is far from pristine and can accumulate toxic ammonia in the debris and decaying remains that accumulate there, threatening other dwellers. ‘Ammonia is a major environmental limitation for crabs’, says Luqing Pan from the Ocean University of China. In addition, crabs and other marine species naturally produce and excrete the gas as waste and he details several mechanisms that allow the resourceful crustaceans to excrete it in polluted environments. However, it was not clear whether crabs also carry a specialised class of proteins, known as Rhesus-like glycoproteins (Rh proteins), which pump ammonia out of tissues in mammals, some insects and crustaceans. Intrigued by the possibility that the Japanese blue crab (Portunus trituberculatus) may depend on the protein to clear their bodies of ammonia, Pan and Lingjun Si began searching for one of the elusive Rh protein genes in the crab's DNA.Collecting gills from the crabs, the duo successfully identified a 1855 base pair gene that codes for a protein with all of the essential amino acid characteristics of a Rh protein. And when they searched for evidence of mRNA produced by the gene in a variety of tissues, they found it was mostly produced in the gills, which are the main site of ammonia excretion in many aquatic species. But the duo needed evidence that Rh protein was actually produced from the mRNA in the gill and was responsible for ammonia excretion.Injecting small fragments of RNA into the crustaceans to disrupt production of the protein, the team noticed that the crabs switched to producing other proteins that could contribute to ammonia excretion. And, when they measured how fast the animals were expelling ammonia from their bodies, the rate fell dramatically in the animals that had lost use of their Rh gene, while ammonia accumulated in their haemolymph.Having convinced themselves that the crabs produce the Rh protein, Si and Pan teamed up with Hongdan Wang and Xin Zhang to monitor the responses of several genes that are involved in ammonia excretion in real time to better understand the role of the Rh protein, in combination with other pump proteins, in ammonia waste disposal and they suspect that it is critical. ‘[It] may be the basis of the crab's ability to inhabit benthic water with high ammonia levels’, says Si.

Origanum vulgare essential oils inhibit glutamate and aspartate metabolism altering the photorespiratory pathway in Arabidopsis thaliana seedlings

Essential oils (EOs) have been extensively studied as valuable eco-friendly compounds with herbicidal activity for weed management. Phytotoxic potential of EOs, extracted from a wild population of Origanum vulgare ssp. hirtum (Link) Ietswaart, has been here evaluated on plant model Arabidopsis, through a physiological and metabolomic approach. The EOs composition was mainly characterized by monoterpenes and sesquiterpenes, with a strong abundance of two monoterpenic phenols, namely carvacrol and thymol, and the monoterpene o-cymene. The in vitro bioassay confirmed a strong phytotoxic effect of EOs on Arabidopsis rosettes, showing by both a strong growth reduction and highly chlorotic leaves. In well-developed seedlings, EOs firstly caused growth reduction and leaf chlorosis, together with a series of interconnected metabolic alterations: i) impairing the nitrogen assimilation into amino acids, which affects in particular the glutamine metabolism; and as consequence ii) excessive accumulation of toxic ammonia into the leaves, associated with oxidative stress and damage; iii) declining the efficiency of the photosynthetic apparatus, connected to the reduced CO2 fixation and photooxidation protection; iv) impairing the photorespiratory pathway. Overall, the results highlights that EOs alters principally the ability of Arabidopsis seedlings to incorporate inorganic nitrogen into amino acids, principally glutamine, leading to a dramatic accumulation of ammonia in leaf cells. This primary effect induces, in turn, a cascade of reactions that limits the efficiency of PSII, inducing oxidative stress and finally causing a strong plant growth reduction, leaf necrosis and eventually plant death.These findings suggest that O. vulgare EOs might be proficiently exploited as a potential bioherbicide in an ecofriendly agriculture. Moreover, its multitarget activity could be advantageous in limiting weed resistance phenomenon.

Widespread use of emersion and cutaneous ammonia excretion in Aplocheiloid killifishes.

The invasion of land required amphibious fishes to evolve new strategies to avoid toxic ammonia accumulation in the absence of water flow over the gills. We investigated amphibious behaviour and nitrogen excretion strategies in six phylogenetically diverse Aplocheiloid killifishes (Anablepsoides hartii, Cynodonichthys hildebrandi, Rivulus cylindraceus, Kryptolebias marmoratus, Fundulopanchax gardneri, and Aplocheilus lineatus) in order to determine if a common strategy evolved. All species voluntarily emersed (left water) over several days, and also in response to environmental stressors (low O2, high temperature). All species were ammoniotelic in water and released gaseous ammonia (NH3 volatilization) during air exposure as the primary route for nitrogen excretion. Metabolic depression, urea synthesis, and/or ammonia accumulation during air exposure were not common strategies used by these species. Immunostaining revealed the presence of ammonia-transporting Rhesus proteins (Rhcg1 and Rhcg2) in the skin of all six species, indicating a shared mechanism for ammonia volatilization. We also found Rhcg in the skin of several other fully aquatic fishes, implying that cutaneous ammonia excretion is not exclusive to amphibious fishes. Overall, our results demonstrate that similar nitrogen excretion strategies while out of water were used by all killifish species tested; possibly the result of shared ancestral amphibious traits, phenotypic convergence, or a combination of both.

Utilization of Fly Ash Contaminated by SNCR Flue Gas Denitrification into Polymer Epoxy Anchor

The paper deals with the possibility of using two different types of fly ash contaminated by flue gas denitrification (Selective Non-Catalytic Reduction (SNCR)) as a filler into the polymer anchor based on epoxy resin. Due to the problematic use of contaminated fly ash in silicate materials, the use of such fly ash in polymer materials seems to be effective because by mixing with polymers such as polyester and epoxy resins, toxic gas ammonia (NH3) does not release. Determination of optimal percentage of filling by the fly ash was performed in order to achieve the best possible physical and mechanical properties of the epoxy anchor material. It was found out that the 45% addition of both used of contaminated fly ashes seems to be the most appropriate, when the polymer anchor material exhibited better tensile properties than reference anchors containing quartz sand Dorsilit. Furthermore, it was found that the optimal addition of contaminated fly ash also positively influenced the maximum anchoring force found in the tug test. Detailed connection of anchor material with anchored bar and concrete was observed on tomography images.

A Platinum Cantilever-Based TCD for 3-Omega Sensing of Gas Mixtures

This paper is on the fabrication and characterization of a platinum cantilever-based TCD gas sensor for detection of highly toxic and corrosive ammonia gas. The sensor is made of platinum and supported with 100nm Al2O3 for its mechanical strength. To improve the signal to noise ratio of sensing technique, 3-Omega technique is used. The fabricated platinum cantilever-based TCD sensor successfully detect 60 ppm ammonia in helium carrier.

Simultaneous nutrient removal and biomass/lipid production by Chlorella sp. in seafood processing wastewater

Microalgae cultivation in wastewater has received increasing attention in recent years due to its many advantages. In this work, microalgae were cultured in seafood processing wastewater (SPW) for algal biomass and lipid production as well as nutrient removal. The biomass yield of Chlorella sp. achieved in the batch cultivation was 896 mg L−1, indicating that SPW contains a certain amount of nutrients which can be used for the growth of microalgae. However, the maximum specific growth rate of Chlorella sp. cultured in SPW throughout the whole cultivation period was only 0.040 d−1, suggesting that the growth of algal cells was inhibited during the culture process. High concentration of unionized ammonia in the SPW was found to be a factor inhibiting the growth of Chlorella sp. Aerated SPW (ASPW) and diluted SPW (DSPW) proved to be better culture media than SPW without pretreatment. The maximum specific growth rates of Chlorella sp. cultured in ASPW and DSPW during the culture interval were 0.156 and 0.091 d−1, respectively. Aeration pretreatment of SPW reduced the amount of toxic unionized ammonia, while most of the nutrients were retained in the wastewater. Therefore, higher biomass productivity (77.7 mg L−1 d−1) and higher lipid productivity (20.4 mg L−1 d−1) of microalgae were achieved in ASPW. Additionally, improved nutrient removal rates from ASPW were also achieved due to the faster growth of microalgae. The average nutrient removal rates in ASPW during the whole cultivation period were 4.98 and 1.91 mg L−1 d−1 for nitrogen and phosphorus, respectively.

Effect of Ammonium Ion Content in Fly Ash after Selective Non-Catalytic Reduction (SNCR) on Physical and Mechanical Properties of Autoclaved Aerated Concrete (AAC)

After introducing SNCR in coal combustion process in power plants, the valuable by-product such as fly ash remains contaminated with amount of ammonia in form of NH4HSO4, (NH4)2SO4 respectively, which became undesirable in AAC technology because the toxic ammonia is released in the air during the mixing process. This paper deals with the effect of varying ammonia content in fly ash after selective non-catalytic reduction (SNCR) on the physical-mechanical properties of the fly ash based autoclaved aerated concrete (AAC) with the main focus on determination of the impact of the various content of ammonium ion in fly ash on the initial consistency of fresh slurry, the residual content of ammonium ion in hardened aerated matrix and also the impact on the bulk density, compressive strength and tobermorite formation after hydrothermal treatment. Seven batches of AAC, made out of fly ash with rising content of ammonium ion from 0 ppm to 250 ppm, were tested and based on the results obtained it was found out that ammonia is released during the mixing process entirely and doesn‘t remain in AAC after autoclaving, moreover it doesn‘t affect the properties of both fresh slurry (no apparent foaming effect noticed) and thermally treated samples of AAC. Formation of tobermorite wasn’t negatively affected.

Special Grout for Anchoring Steel Elements with High Proportion of Fly Ash Contaminated by Denitrification Process

This paper focuses on the possible use of fly ash contaminated by denitrification process as filler for special grouts based on epoxy resin. This fly ash is contaminated by combined ammonia ions as a consequence of flue gas denitrification. When mixing this fly ash with water and silica materials, ammonia (NH3) is released, therefore its application in these materials is inappropriate. The use of such fly ash as filler in polymeric substances, e.g. epoxy, polyester or vinyl ester resin, seems to be appropriate. When mixing fly ash with these materials, fly ash particles become coated with a polymeric substance, therefore no toxic ammonia is released. In the experiment, the impact of two kinds of contaminated fly ashes (FA-1, FA-2) and different percentages of filler in a polymer grout was examined on the resulting physical and mechanical properties. It was found that the best properties were by the grout with fly ash from circulating fluidized bed combustion from the Kladno thermal power plant (FA-1) under 45% of filling. This material showed high compressive and three-point bending strength and the flexural modulus was even higher than in the case of the reference material, which contained reference silica sand with optimal round grain shape as filler. Furthermore, chemical resistance of these materials against aggressive liquid solutions used in industrial operations were examined. An ideal grout formula was checked in a cut of an embedded steel element under optical microscope. A pull-out strength test was also performed in the case of the best formulas to determine the anchoring rate of embedded steel rod.