Behaviour of selenium and tellurium in copper electrowinning process

2020 ◽  
pp. 82-87
Author(s):  
B. E. Zatitskiy ◽  
◽  
O. A. Trubina ◽  
Keyword(s):  
Commercial Application ◽  
First Order ◽  
Cathode Copper ◽  
Purity Level ◽  
Copper Electrowinning ◽  
Low Concentrations ◽  
Copper Electrolyte ◽  
Maximum Current ◽  
Cathode Reduction

The revamping project to be implemented at Norilsk Nickel’s refining facilities includes commissioning of a nickel plant and increasing the output of copper obtained by electrowinning from liquors produced in matte leach processes. At the revamped facility, a major portion of selenium and a considerable share of tellurium will be transferred with calciner gases to a sulphuric acid facility. The microimpurities that remain after calcination get distributed between the leachates. Considering that semiproducts keep circulating between the nickel and copper plants, selenium and tellurium can accumulate in the product solutions and thus affect the quality of finished metals. This paper examines the behaviour of selenium and tellurium in copper electrowinning process and formulates certain requirements for copper electrolyte that will ensure production of high-purity copper cathodes for commercial application. It is shown that, at low concentrations of selenium (IV) and tellurium (IV) in the copper electrolyte, their discharge follows the laws of diffusion kinetics, i.e. occurs at maximum current, together with cathode reduction of copper, and the concentrations of selenium and tellurium in copper change in correlation with the concentration of chalcogenides in the solution. Simultaneously with cathode reduction on a lead anode, selenium (IV) and tellurium (IV) get oxidized to selenium (VI) and tellurium (VI) that are not precipitable with copper and get accumulated in circulating solutions. It is shown that the concentration of chalcogenides has a negative first order from the removal of copper per unit volume of electrolyte. That’s why the contamination of cathode copper with selenium and tellurium rapidly decreases with an increase in copper removal. The paper provides data that can be used to estimate the allowable concentration of toxic microimpurities in the feed electrolyte that would not affect the desired copper purity level.

Submerged upflow biotower operation and computer simulation

1994 ◽  
Vol 30 (11) ◽  
pp. 143-146
Author(s):  
Ronald D. Neufeld ◽  
Christopher A. Badali ◽  
Dennis Powers ◽  
Christopher Carson
Keyword(s):  
Computer Simulation ◽  
Benzoic Acid ◽  
Computer Model ◽  
Rate Constants ◽  
Batch Mode ◽  
Operational Conditions ◽  
First Order ◽  
Low Concentrations ◽  
Biological Transformation ◽  
Kinetics Of

A two step operation is proposed for the biodegradation of low concentrations (< 10 mg/L) of BETX substances in an up flow submerged biotower configuration. Step 1 involves growth of a lush biofilm using benzoic acid in a batch mode. Step 2 involves a longer term biological transformation of BETX. Kinetics of biotransformations are modeled using first order assumptions, with rate constants being a function of benzoic acid dosages used in Step 1. A calibrated computer model is developed and presented to predict the degree of transformation and biomass level throughout the tower under a variety of inlet and design operational conditions.

Biodegradation rates of aromatic contaminants in biofilm reactors

1995 ◽  
Vol 31 (1) ◽  
pp. 117-128 ◽  
Author(s):  
Jean-Pierre Arcangeli ◽  
Erik Arvin
Keyword(s):  
Aromatic Hydrocarbons ◽  
Competitive Inhibition ◽  
Removal Rate ◽  
First Order ◽  
Biofilm Reactors ◽  
First Order Kinetics ◽  
Reducing Conditions ◽  
Low Concentrations ◽  
Degradation Rates ◽  
Order Surface

This study has shown that microorganisms can adapt to degrade mixtures of aromatic pollutants at relatively high rates in the μg/l concentration range. The biodegradation rates of the following compounds were investigated in biofilm systems: aromatic hydrocarbons, phenol, methylphenols, chlorophenols, nitrophenol, chlorobenzenes and aromatic nitrogen-, sulphur- or oxygen-containing heterocyclic compounds (NSO-compounds). Furthermore, a comparison with degradation rates observed for easily degradable organics is also presented. At concentrations below 20-100 μg/l the degradation of the aromatic compounds was typically controlled by first order kinetics. The first-order surface removal rate constants were surprisingly similar, ranging from 2 to 4 m/d. It appears that NSO-compounds inhibit the degradation of aromatic hydrocarbons, even at very low concentrations of NSO-compounds. Under nitrate-reducing conditions, toluene was easily biodegraded. The xylenes and ethylbenzene were degraded cometabolically if toluene was used as a primary carbon source; their removal was influenced by competitive inhibition with toluene. These interaction phenomena are discussed in this paper and a kinetic model taking into account cometabolism and competitive inhibition is proposed.

Assessing Medical Evidence

2018 ◽  
Author(s):  
Jacob Stegenga
Keyword(s):  
Quality Assessment ◽  
Randomized Trials ◽  
Empirical Studies ◽  
Allocation Concealment ◽  
Assessment Tools ◽  
Medical Evidence ◽  
Empirical Methods ◽  
First Order ◽  
First Order Methods

Medical scientists employ ‘quality assessment tools’ to assess evidence from medical research, especially from randomized trials. These tools are designed to take into account methodological details of studies, including randomization, subject allocation concealment, and other features of studies deemed relevant to minimizing bias. There are dozens of such tools available. They differ widely from each other, and empirical studies show that they have low inter-rater reliability and low inter-tool reliability. This is an instance of a more general problem called here the underdetermination of evidential significance. Disagreements about the quality of evidence can be due to different—but in principle equally good—weightings of the methodological features that constitute quality assessment tools. Thus, the malleability of empirical research in medicine is deep: in addition to the malleability of first-order empirical methods, such as randomized trials, there is malleability in the tools used to evaluate first-order methods.

Effects of initial concentration and irradiation dose to degradation of di butyl phthalate from phosphoric acid (30 % P2O5)

2018 ◽  
Vol 106 (11) ◽  
pp. 909-916
Author(s):  
Louisa Bounemia ◽  
Abdelhamid Mellah
Keyword(s):  
Organic Matter ◽  
Phosphoric Acid ◽  
Optimal Recovery ◽  
Γ Irradiation ◽  
Γ Radiation ◽  
Initial Concentration ◽  
First Order ◽  
First Order Kinetics ◽  
Butyl Phthalate

Abstract The pretreatment of the phosphoric acid is a stage of utmost importance leading to an optimal recovery of the uranium present in this acid. To this end, the degradation of the organic matter which obstructs considerably this recovery was tested by γ irradiation. This study lies within the scope of the radiation/matter interaction; concerning the use of the γ irradiator as proceed of phosphoric acid purification by the degradation of di butyl phthalate (DBP). Studies of the interaction of γ radiation with phosphoric acid solutions polluted by an organic matter concern the study of the influence of some parameters such as: dose rate (0.5–35 kGy), initial concentration (50–500 mg/L) of the pollutant, pH and % in P2O5 on the degradation of organic matter by γ irradiation. The reactions followed pseudo first order kinetics for different initial concentrations. The results made it possible to say that the degradation of di butyl phthalate by γ irradiation is dependent on the amount of the concentration of DBP and pH. The G-values decreased with absorbed doses, and increased with higher initial concentrations.Purification of phosphoric acid by γ radiation does not degrade the quality of this acid.

scholarly journals Growth analysis of sweet pepper cultivated in coconut fiber in a greenhouse

2011 ◽  
Vol 29 (3) ◽  
pp. 316-323 ◽  
Author(s):  
Hamilton César de O Charlo ◽  
Sueyde F de Oliveira ◽  
Renata Castoldi ◽  
Pablo F Vargas ◽  
Leila T Braz ◽  
...  
Keyword(s):  
Growth Analysis ◽  
Dry Mass ◽  
Sweet Pepper ◽  
Absolute Rate ◽  
Coconut Fiber ◽  
First Order ◽  
Growth Production ◽  
Four Blocks ◽  
Over Time

Knowledge about the growth of crops allows the planning of rational cultivation methods which contribute to achieve greater potential of plant species, besides supplying information for the construction of descriptive mathematical models of growth. The growth curve of sweet pepper (Eppo hybrid), cultivated in coconut fiber in a greenhouse with fertirrigation, was determined. The experiment consisted initially of 160 plants divided into four blocks. Two plants were analyzed per block every 21 days after transplanting, ending at 189 days after transplant. The cultivation was carried out in plastics pots of 13 L containing coconut fiber, which were arranged in double rows, spaced 0.5 x 0.8 m between simple rows and 1.1 m between double rows. In each harvest the plant growth, production and quality of mature fruits were evaluated. The dry mass of the shoot increased with time, following the experimental model exponential of first order, reaching a maximum of 451.5 g/plant, 189 days after transplanting (DAT). The production of dry mass of leaves, stem, root and fruit also increased over time reaching maximum values of 68.7, 65.8, 11.5 and 302.9 g/plant, respectively, at 189 DAT. The same occurred with the leaf area per plant, plant height and the absolute rate of growth, whose maximum values were 6.183,5 cm², 136.9 cm and 4.4 g/plant/day, respectively. The growth of the plant was continuous throughout the cycle, and the highest amount of dry mass was accumulated in fruits, reaching a marketable production of 97.3 t ha-1. All fruits were classified as Extra.

scholarly journals Pencucian biodiesel dengan metode kontak gelembung

2018 ◽  
Vol 7 (1) ◽  
pp. 738
Author(s):  
Yoel Pasae ◽  
John Stephen
Keyword(s):  
Biodiesel Production ◽  
Water Molecules ◽  
Air Bubbles ◽  
Process Technology ◽  
Technical Standards ◽  
Purity Level ◽  
Washing Process ◽  
Washing Method ◽  
Total Glycerol

Until today, the conversion of palm oil and recovery of glycerol as a byproduct have been extensively investigated. The purity level of product from the washing process in the biodiesel production technology heavily influences the quality of the biodiesel product. Therefore, this research is aimed at identifying the biodiesel washing process technology which is able to produce biodiesel according to standards for diesel engine application. The washing process employed in this research is the bubble method, which utilizes air bubbles injected from the bottom as a carrier form water molecules to the top layer of the contactor (the biodiesel phase) which contains glycerol, soap, and residual methanol. This bubble method enables the contact between water molecules and glycerol in the biodiesel phase, when the bubbles are swept to the fluid surface, without any external agitation. Experimental results indicate that with a three-stage washing process, the total glycerol content in the biodiesel can be reduced to approach the technical standards for combustion in diesel engines, or the Biodiesel Tentative Standards stipulated by the Indonesian Biodiesel Forum.Keywords: Bubble washing method, biodiesel AbstrakSampai dewasa ini proses konversi reaksi minyak kelapa sawit dan recovery gliserol sebagai hasil samping telah banyak diteliti. Tingkat kemurnian hasil dari tahapan proses pencucian dalam teknologi produksi biodiesel sangat menentukan kualitas biodiesel yang dihasilkan. Oleh karena itu penelitian ini bertujuan untuk mendapatkan teknologi proses pencucian biodiesel sehingga diperoleh biodiesel yang memenuhi standar untuk penggunaan pada mesin-mesin diesel. Proses pencucian yang dilakukan dalam penelitian ini yaitu metode gelembung, yang memanfaatkan gelembung udara yang dinjeksikan dari bagian bawah kolom (bottom) sebagai carrier (pembawa) molekul air ke bagian atas (fasa biodiesel) yang mengandung gliserol, sabun dan sisa metanol. Dengan metode gelembung ini, akan memungkinkan molekul air berkontakan dengan gliserol pada fasa biodiesel, saat terbawa ke permukaan fluida, tanpa dilakukan pengadukan eksternal. Dari hasil penelitian menunjukkan bahwa dengan sistim pencucian tiga tahap, kadar gliserol total dalam biodiesel dapat diturunkan hingga mendekati standar untuk pembakaran pada mesin diesel atau Standar Tentatif Biodiesel dari Forum Biodiesel Indonesia.Kata Kunci: Metode Pencucian Gelembung, Biodiesel.

scholarly journals Akinetic model for the consumption of stabilizer in single base gun propellants

2002 ◽  
Vol 67 (2) ◽  
pp. 103-109 ◽  
Author(s):  
Ljiljana Jelisavac ◽  
Milos Filipovic
Keyword(s):  
Life Time ◽  
Order Reaction ◽  
Zero Order ◽  
Final Phase ◽  
Single Base ◽  
First Order ◽  
Low Concentrations ◽  
Zero Order Reaction ◽  
High Concentrations ◽  
Gun Propellants

A suitable kinetic model for the consumption of stabilizer (diphenylamine) in single base gun propellants was investigated and successfully verified. The model assumes that a reaction of shifting order can be applied for the consumption of diphenylamine in single base gun propellants. It was found that the experimental data were well evaluated by a first-order reaction at high concentrations of diphenylamine in the propellant, but by a zero-order reaction at low concentrations during the final phase of the propellant life time. The mechanism of diphenylamine depletion was discussed with relation to the model and the ageing behavior of the propellants. The kinetic parameters of this model, which permit the calculation of the time up to complete consumption of the diphenylamine, were determined. The results were compared with the kinetic data obtained by a widely accepted model, which combines formally reactions of first and zero order, designated as an "exponential and linear" model. All comparisons gave satisfactory agreement.

scholarly journals Сitric acid influence on electroreduction processes in low concentrated Cu(NO3)2 solutions

2017 ◽  
Vol 5 (2) ◽  
pp. 136-143
Author(s):  
Alla Pravda ◽  
Vasil Larin
Keyword(s):  
Citric Acid ◽  
Ph Value ◽  
Reduction Reaction ◽  
Copper Electrodeposition ◽  
Nitrate Ions ◽  
Low Concentrations ◽  
Physico Chemical ◽  
Influence Of Ph ◽  
Kinetics Of ◽  
Cathode Reduction

Physico-chemical regularities citric acid influence on processes of copper and nitrate-ions reduction in low concentrated nitrate solutions were established. An influence of pH value on inhibitor action of low concentrations of the additive according to cathode reduction reaction of nitrate-ions, on kinetics of copper electrodeposition, on structure of the precipitates obtained was shown. Polarization measurements show us changes of copper electrodeposition at introduction of citric acid in Cu(NO3)2 solution. By the methods of traced elements and extraction into aqueous phase the reversible inclusion complexes into electrolytic copper, was established that proves participation of complexes in cathode process.

scholarly journals A Systematic Comparison of Various Statistical Alignment Models

2003 ◽  
Vol 29 (1) ◽  
pp. 19-51 ◽  
Author(s):  
Franz Josef Och ◽  
Hermann Ney
Keyword(s):  
Training Algorithm ◽  
Dice Coefficient ◽  
Design Decisions ◽  
First Order ◽  
Model Yield ◽  
Alignment System ◽  
Word Alignments ◽  
Alignment Model ◽  
Statistical Alignment

We present and compare various methods for computing word alignments using statistical or heuristic models. We consider the five alignment models presented in Brown, Della Pietra, Della Pietra, and Mercer (1993), the hidden Markov alignment model, smoothing techniques, and refinements. These statistical models are compared with two heuristic models based on the Dice coefficient. We present different methods for combining word alignments to perform a symmetrization of directed statistical alignment models. As evaluation criterion, we use the quality of the resulting Viterbi alignment compared to a manually produced reference alignment. We evaluate the models on the German-English Verbmobil task and the French-English Hansards task. We perform a detailed analysis of various design decisions of our statistical alignment system and evaluate these on training corpora of various sizes. An important result is that refined alignment models with a first-order dependence and a fertility model yield significantly better results than simple heuristic models. In the Appendix, we present an efficient training algorithm for the alignment models presented.

A E-Business Case of Study

2017 ◽  
Vol 8 (3) ◽  
pp. 1-20
Author(s):  
Maria Vargas-Vera ◽  
Camilo Salles ◽  
Joaquin Parot ◽  
Sebastian Letelier
Keyword(s):  
Chemical Composition ◽  
Red Wine ◽  
Business Case ◽  
Order Logic ◽  
Wine Industry ◽  
First Order Logic ◽  
Qualitative Properties ◽  
Wine Quality ◽  
First Order

The main purpose of this research was to find relations between the chemical composition of the wines and the wine testers' opinions on the wine quality. We used in our study a dataset which contains examples of red wine from Vinho Verde, Portugal. Firstly, we did an analysis on the attributes of the examples, in the dataset, to find correlations between quantitative and qualitative properties in wines. Secondly, we performed clustering using the algorithms k-means and x-means. Additionally, we used the J48 algorithm for getting a decision tree and then to extract first order logic rules. We concluded that, there is a relation between physicochemical properties and quality of wines. This result opens the possibility of further analysis and perhaps this could lead to use fewer wine testers and therefore, our research could bring benefit to the wine industry.

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