Author: T. Tacke
Publisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 42

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Author:
Publisher:
ISBN:
Category : Engineering
Languages : en
Pages : 468

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Author: Priyanka Gheek
Publisher:
ISBN:
Category :
Languages : en
Pages :

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We chose to study the catalytic conversion of dissolved nitrate, which are a major cause of water contamination. It is a complex process into several steps following the reaction: NO3- → NO2-→ [NO] → N2 + NH4+ + + OH- The scientific goal of this thesis was to determine a relationship between the physico-chemical structure of catalysts and their activity and selectivity in the reduction of nitrates. The reaction kinetics were also studied in relation to the structure of catalysts. The work focused around the following points: 1. Preparation of catalyst supports: Two main groups of materials were studied: carbon materials and inorganic materials that have been modified by acid or base treatment or by deposit oxides (Al2O3, ZrO2 alone or in mixture). 2. Synthesis of catalyst: oxides of noble and transition metals have been established on the supports. Systems with monometallic Pt and Pd and bimetallic Pd-Cu have been studied and characterized by many techniques. The effectiveness of these materials was determined depending on their catalytic activity. 3. Determination of the catalytic properties: The role and effect of parameters such as support, type of medium, active phase composition, the presence of inorganic salts in the reaction medium, nature of reducing on the rate of nitrate reduction and selectivity of the reactions were widely studied. The debate highlights the combination support / most effective catalyst for denitrification of drinking water

Author: Michael Sell
Publisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 64

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Author: Rui Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Catalytic hydrogenation over Pd-based catalysts has emerged as an effective treatment approach for nitrate (NO3-) removal, but its full-scale application for direct treatment of drinking water or ion exchange regenerant brines requires improved selectivity for the end-product dinitrogen (N2) over toxic ammonia species (NH4+, NH3). A key to improving N2 versus NH4+ production is to elucidate nitrate reduction pathways and identify the key intermediate(s) that determine selectivity. To address this challenge, aqueous reduction experiments with an Al2O3-supported Pd/In bimetallic catalyst were conducted using isotope-labeled nitrite (15NO2-), the first reduction intermediate of NO3-, alone and in combination with unlabeled proposed reduction intermediates (N2O, NO), and using N2O and NO alone, each as a starting reactant. Use of 15N-labeled species eliminated interference from ambient 14N2 when assessing mass balances and product distributions. Simultaneous catalytic reduction of 15NO2- and 14N2O showed no isotope mixing in the final N2 product, demonstrating that N2O does not react with other NO2- reduction intermediates. N2O reduction alone also yielded only N2, verifying that N2O reduction occurs after the reaction step controlling final N2/NH4+ product distribution. In contrast, simultaneous catalytic reduction of 15NO2- and 14NO yielded mixed-labeled N2 (mass 29), and 15NO reduction alone yielded both N2 and NH4+, indicating that NO is a key intermediate involved in determining final product selectivity. N2/NH4+ product selectivity was also evaluated as a function of varying initial 15NO concentration, and results show that selectivity for N2 increases with initial NO concentration to a point, above which product selectivity remains unchanged. This trend is attributed to the increasing importance of N-N pairing reactions leading to N2O formation as the concentration of catalyst-adsorbed NO (NOads) increases to a point of saturating available adsorption sites, above which no further increases in N2 selectivity occur. These results are important because they yield mechanistic insights into the NO3- reduction pathway and information on how catalytic reduction processes can be optimized to maximize N2 production over NH4+.

Author:
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 574

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Author: Madison Bertoch
Publisher:
ISBN:
Category :
Languages : en
Pages : 80

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Palladium-based bimetallic catalysts hold promise as an alternative water treatment technology for nitrate (NO3-), but practical application requires development of a flow-through reactor that efficiently delivers hydrogen (H2) from the gas phase into water, where it serves as the electron donor for NO3- reduction. In this work, a trickle bed reactor (TBR) was fabricated and evaluated to address this challenge. A series of batch experiments with Pd-In/[greek small letter gamma]-Al2O3 catalysts were conducted in excess H2 to identify a highly active catalyst for the TBR. A 0.1wt%Pd-0.01wt%In on 1 mm [greek small letter gamma]-Al2O3 catalyst was selected due to its high activity and support size that promotes a uniform liquid distribution in a packed bed. The TBR was packed with the same catalyst, and various liquid and gas flow rates were tested to evaluate apparent catalyst activity. Influent and effluent NO3- concentrations were used to calculate apparent zero-order rate constants, and they generally increased with H2 flow rate. Above 900 mL/min, a change in flow regime from pulse to bubble flow was observed, and the calculated zero-order rate constants decreased. An optimal catalyst activity in the TBR of 19.5 mg NO3-/min[bullet=black small circle]g Pd was obtained at a liquid flow rate of 900 mL/min and H2 flow rate of 320 sccm, which is ~22% of the activity obtained in the batch reactor by the same catalyst, indicating H2 mass transfer limitations. A reactive transport model was developed and used to quantify H2 mass transfer rate coefficients from the liquid to gas phase. Mass transfer coefficients initially decrease and then stabilize as the H2 flow rate increases. At elevated H2 flow rates, the highest mass transfer coefficients were obtained at the 900 mL/min liquid flow rate, in agreement with activity trends. Evaluation of a larger range of liquid and gas flow rates is warranted to determine if H2 mass transfer in the TBR can be further enhanced.

Author: Istvan Bogardi
Publisher: Springer Science & Business Media
ISBN: 3642760406
Category : Technology & Engineering
Languages : en
Pages : 438

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Book Description
The nitrate content of drinking water is rising at an alarming rate in several regions of NATO countries and elsewhere in the world. The increase is due to lack of proper sewage treatment, and primarily to excess fertilizer application. Also, eutrophication in several coastal areas is triggered by high nitrate concentrations. The main purpose of this book is to integrate scientific knowledge related to exposure assessment, health consequences and control of nitrate contamination in water. The motivation is related to the magnitude, the possible adverse health effects, and the high cost of control ling nitrate contamination. Future research tasks are defined by an interaction among hydro logists, toxicologists and environmental engineers in an integrated framework for nitrate risk management. The target readership of this book is a mix of university colleagues, practitioners from both the private and public sectors and advanced graduate students working with the hydrological, health science or environmental engineering aspects of nitrate contamination. The main conclusions include: 1. For risk assessment purposes, knowledge and sufficiently accurate models are available to predict nitrate load and its fate in water under changes in land use. 2. Once agricultural exposure controls are implemented, the response times in ground water may be so long as to make controls unrealistic. 3. It is still unknown whether agricultural best management practice is a compromise between nitrate risk reduction and agricultural revenue. 4. The current drinking water guidelines of 10 mg/L NOrN need not be changed.

Author: Juan M. Lema
Publisher: IWA Publishing
ISBN: 1780407866
Category : Science
Languages : en
Pages : 690

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Book Description
This book introduces the 3R concept applied to wastewater treatment and resource recovery under a double perspective. Firstly, it deals with innovative technologies leading to: Reducing energy requirements, space and impacts; Reusing water and sludge of sufficient quality; and Recovering resources such as energy, nutrients, metals and chemicals, including biopolymers. Besides targeting effective C,N&P removal, other issues such as organic micropollutants, gases and odours emissions are considered. Most of the technologies analysed have been tested at pilot- or at full-scale. Tools and methods for their Economic, Environmental, Legal and Social impact assessment are described. The 3R concept is also applied to Innovative Processes design, considering different levels of innovation: Retrofitting, where novel units are included in more conventional processes; Re-Thinking, which implies a substantial flowsheet modification; and Re-Imagining, with completely new conceptions. Tools are presented for Modelling, Optimising and Selecting the most suitable plant layout for each particular scenario from a holistic technical, economic and environmental point of view.

Author: Vincenzo Piemonte
Publisher: John Wiley & Sons
ISBN: 1118629841
Category : Technology & Engineering
Languages : en
Pages : 377

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Book Description
Sustainable development is an area that has world-wide appeal, from developed industrialized countries to the developing world. Development of innovative technologies to achieve sustainability is being addressed by many European countries, the USA and also China and India. The need for chemical processes to be safe, compact, flexible, energy efficient, and environmentally benign and conducive to the rapid commercialization of new products poses new challenges for chemical engineers. This book examines the newest technologies for sustainable development in chemical engineering, through careful analysis of the technical aspects, and discussion of the possible fields of industrial development. The book is broad in its coverage, and is divided into four sections: Energy Production, covering renewable energies, innovative solar technologies, cogeneration plants, and smart grids Process Intensification, describing why it is important in the chemical and petrochemical industry, the engineering approach, and nanoparticles as a smart technology for bioremediation Bio-based Platform Chemicals, including the production of bioethanol and biodiesel, bioplastics production and biodegradability, and biosurfactants Soil and Water Remediation, covering water management and re-use, and soil remediation technologies Throughout the book there are case studies and examples of industrial processes in practice.