Effect of process conditions on reaction-type adsorption of o-xylene by MCM-41 supported sulfuric acid: model simulations of breakthrough curves

2021 ◽  
pp. 106937
Author(s):  
Mengze Ma ◽  
Kaiyin Gao ◽  
Dandan Zhao ◽  
Xiaolong Ma ◽  
Zichuan Ma
Keyword(s):  
Sulfuric Acid ◽  
Breakthrough Curves ◽  
Process Conditions ◽  
Reaction Type ◽  
Model Simulations ◽  
Mcm 41

scholarly journals Extraction of Ta and Nb from a Coltan Bearing Ore by Means of Ammonium Bifluoride Fluorination and Sulfuric Acid Leaching

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1392
Author(s):  
Alidor Shikika ◽  
Francois Zabene ◽  
Fabrice Muvundja ◽  
Mac C. Mugumaoderha ◽  
Julien L. Colaux ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Acid Leaching ◽  
Environmental Benefits ◽  
Process Conditions ◽  
Sulfuric Acid Leaching ◽  
Mechanical Agitation ◽  
Ammonium Bifluoride ◽  
Novel Approach ◽  
Pre Treatment ◽  
Subsequent Acid

A novel approach for Ta and Nb extraction consisting of the pre-treatment of a coltan-bearing ore with an ammonium bifluoride sub-molten salt and subsequent acid leaching has been studied. The effects from ore granulometry, ammonium bifluoride (ABF) to ore mass ratio, temperature and duration of fluorination on the degree of Ta and Nb extraction were examined. The ABF to ore ratio and process temperature were found to have the most pronounced impact on extraction efficiency. The following optimal process conditions were determined: ore granulometric fraction (−75 + 45 µm), ABF-ore (5/1), fluorination temperature (200 °C) and fluorination time (2.5 h). Maintaining these parameters enabled about 94% of Ta and 95% of Nb to be brought into solution during the sulfuric-acid-leaching stage. A comparison of the proposed method with previously reported studies suggests that due to the effects of mechanical agitation and the recirculation of the HF-containing gaseous phase back into the process, the dosage rate of ABF at the fluorination stage could be reduced significantly without sacrificing the overall recovery of Ta and Nb. In such a way, the approach could offer added environmental benefits since release of fluoride-containing effluents into the environment could be limited.

Characterization of effective permeability of prepreg fibers under autoclave molding process conditions using process model simulations

2020 ◽  
Vol 112 (1) ◽  
pp. 1-7
Author(s):  
Prosenjit Maji ◽  
Arpit Jain ◽  
Nibedita Dutta ◽  
Ahmed Ovais Siddiqui ◽  
Debdarsan Niyogi ◽  
...  
Keyword(s):  
Process Model ◽  
Effective Permeability ◽  
Process Conditions ◽  
Molding Process ◽  
Model Simulations

Prediction of breakthrough of pesticides in GAC-filters and breakthrough of colour in ion-exchange-filters

2002 ◽  
Vol 2 (1) ◽  
pp. 103-108 ◽  
Author(s):  
S.G.J. Heijman ◽  
W. Siegers ◽  
R. Sterk ◽  
R. Hopman
Keyword(s):  
Water Quality ◽  
Ion Exchange ◽  
Natural Water ◽  
Drinking Water Treatment ◽  
Breakthrough Curves ◽  
Quality Parameters ◽  
Independent Experiment ◽  
Process Conditions ◽  
Adsorption Parameters ◽  
Exchange Resins

Adsorption columns are widely used in drinking water treatment to improve a number of water quality parameters. Granular activated carbon filtration (GAC) can be used to decrease the concentration of DOC, colour, taste, odour and pesticides. Columns filled with ion-exchange resins are used to remove colour, nitrate and DOC. The regeneration frequency of these types of filters depends strongly on the natural water quality. Especially the DOC-concentration and DOC-composition determines the efficiency of the processes. Because pilot-plant experiments with realistic contact-times will last for more than a year (for GAC) there is a need for a prediction of breakthrough based on shorter and less expensive laboratory experiments. The available models are not accurate enough because the exact parameters are not available. In batch experiments with natural water, with realistic (low) pesticide concentrations and the full grain size of the adsorbent the adsorption parameters are measured in an independent experiment. With the parameters obtained with these experiments an accurate prediction of the breakthrough curve is possible. With the same parameters predictions of breakthrough curves are calculated under different process conditions. The possibilities of process optimisation can reduce the investment costs for new full-scale plants.

scholarly journals East Asian SO<sub>2</sub> pollution plume over Europe – Part 2: Evolution and potential impact

2009 ◽  
Vol 9 (14) ◽  
pp. 4729-4745 ◽  
Author(s):  
V. Fiedler ◽  
F. Arnold ◽  
H. Schlager ◽  
A. Dörnbrack ◽  
L. Pirjola ◽  
...  
Keyword(s):  
Water Vapor ◽  
Sulfuric Acid ◽  
Gas Phase ◽  
Fossil Fuel ◽  
East Asian ◽  
Fossil Fuel Combustion ◽  
Model Simulations ◽  
Upper Troposphere ◽  
The North ◽  
Potential Impact

Abstract. We report on the first observation-based case study of an aged East Asian anthropogenic SO2 pollution plume over Europe. Our airborne measurements in that plume detected highly elevated SO2 mole fractions (up to 900 pmol/mol) between about 5000 and 7000 m altitude. Here, we focus on investigations of the origin, dispersion, evolution, conversion, and potential impact of the observed excess SO2. In particular, we investigate SO2 conversion to gas-phase sulfuric acid and sulfuric acid aerosols. Our FLEXPART and LAGRANTO model simulations, along with additional trace gas measurements, suggest that the plume originated from East Asian fossil fuel combustion sources and, 8–7 days prior to its arrival over Europe, ascended over the coast region of central East Asia to 9000 m altitude, probably in a cyclonic system with an associated warm conveyor belt. During this initial plume ascent a substantial fraction of the initially available SO2 must have escaped from removal by cloud processes. Hereafter, while mostly descending slowly, the plume experienced advection across the North Pacific, North America and the North Atlantic. During its upper troposphere travel, clouds were absent in and above the plume and OH-induced gas-phase conversion of SO2 to gas-phase sulfuric acid (GSA) was operative, followed by GSA nucleation and condensation leading to sulfuric acid aerosol formation and growth. Our AEROFOR model simulations indicate that numerous large sulfuric acid aerosol particles were formed, which at least temporarily, caused substantial horizontal visibility degradation, and which have the potential to act as water vapor condensation nuclei in liquid water cloud formation, already at water vapor supersaturations as low as about 0.1%. Our AEROFOR model simulations also indicate that those fossil fuel combustion generated soot particles, which have survived cloud induced removal during the initial plume ascent, have experienced extensive H2SO4/H2O-coating, during upper troposphere plume travel. This coating may have dramatically altered the morphology and markedly increased the light absorption efficiency of soot particles.

Investigation of process conditions in manufacture of basic aluminum sulfate by dissolution of alumina in sulfuric acid

1977 ◽  
Vol 13 (2) ◽  
pp. 117-118
Author(s):  
N. P. Poezd ◽  
E. D. Radchenko ◽  
V. M. Kornus ◽  
D. F. Poezd ◽  
I. P. Titov ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Aluminum Sulfate ◽  
Process Conditions ◽  
Basic Aluminum

Laboratory Studies of Vanadium Precipitation with Flue-Gas Sulfuric Acid

2013 ◽  
Vol 803 ◽  
pp. 9-12
Author(s):  
Zhen Xiu Wu ◽  
Zhao Hui Sun ◽  
Wen Long Chen ◽  
Guang Chao Du
Keyword(s):  
Sulfuric Acid ◽  
Flue Gas ◽  
Process Conditions ◽  
Laboratory Studies ◽  
One Step ◽  
The Cost ◽  
Experimental Group

The exploratory experiments of precipitating vanadium which simulated the process conditions in a vanadium plant with the indexes of vanadium loss and the cost were tested with industrial sulfuric acid and flue-gas sulfuric acid in laboratory, respectively. The technology optimizations were studied by selecting the experimental group with the lowest vanadium loss and cost. The results indicate that the vanadium loss and cost are the lowest by one-step vanadium precipitation with flue-gas sulfuric acid, and the optimum processes are as follows: the pH of solution is adjusted to 2.2 after adding the vanadium precipitation agent; the precipitation is proceeded 1 hour at 99°C or 100°C. The vanadium loss and cost per 1000 kg V2O3 are respectively 3.06 kg and 763.18 yuan by the optimum processes, which are much less than the processes with industrial sulfuric acid.

scholarly journals Bacteria as Cloud Condensation Nuclei (CCN) in the Atmosphere

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 786
Author(s):  
Mihalis Lazaridis
Keyword(s):  
Contact Angle ◽  
Sulfuric Acid ◽  
Cloud Condensation Nuclei ◽  
Sulfuric Acid Concentration ◽  
Contact Angles ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Condensation Nuclei ◽  
Critical Cluster ◽  
Model Simulations

Bacteria activation and cloud condensation nuclei (CCN) formation have been studied in the atmosphere using the classical theory of heterogeneous nucleation. Simulations were performed for the binary system of sulfuric acid/water using laboratory-determined contact angles. Realistic model simulations were performed at different atmospheric heights for a set of 140 different bacteria. Model simulations showed that bacteria activation is a potentially favorable process in the atmosphere which may be enhanced at lower temperatures. CCN formation from bacteria nuclei is dependent on ambient atmospheric conditions (temperature, relative humidity), bacteria size, and sulfuric acid concentration. Furthermore, a critical parameter for the determination of bacteria activation is the value of the intermolecular potential between the bacteria’s surface and the critical cluster formed at their surface. In the classical nucleation theory, this is parameterized with the contact angle between substrate and critical cluster. Therefore, the dataset of laboratory values for the contact angle of water on different bacteria substrates needs to be enriched for realistic simulations of bacteria activation in the atmosphere.

scholarly journals African biomass burning plumes over the Atlantic: aircraft based measurements and implications for H<sub>2</sub>SO<sub>4</sub> and HNO<sub>3</sub> mediated smoke particle activation

2011 ◽  
Vol 11 (7) ◽  
pp. 3211-3225 ◽  
Author(s):  
V. Fiedler ◽  
F. Arnold ◽  
S. Ludmann ◽  
A. Minikin ◽  
T. Hamburger ◽  
...  
Keyword(s):  
Water Vapor ◽  
Sulfuric Acid ◽  
Biomass Burning ◽  
Vapor Condensation ◽  
Condensation Nuclei ◽  
Smoke Particle ◽  
Model Simulations ◽  
Airborne Measurements ◽  
Smoke Particles ◽  
Water Vapor Condensation

Abstract. Airborne measurements of trace gases and aerosol particles have been made in two aged biomass burning (BB) plumes over the East Atlantic (Gulf of Guinea). The plumes originated from BB in the Southern-Hemisphere African savanna belt. On the day of our measurements (13 August 2006), the plumes had ages of about 10 days and were respectively located in the middle troposphere (MT) at 3900–5500 m altitude and in the upper troposphere (UT) at 10 800–11 200 m. Probably, the MT plume was lifted by dry convection and the UT plume was lifted by wet convection. In the more polluted MT-plume, numerous measured trace species had markedly elevated abundances, particularly SO2 (up to 1400 pmol mol−1), HNO3 (5000–8000 pmol mol−1) and smoke particles with diameters larger than 270 nm (up to 2000 cm−3). Our MT-plume measurements indicate that SO2 released by BB had not experienced significant loss by deposition and cloud processes but rather had experienced OH-induced conversion to gas-phase sulfuric acid. By contrast, a significant fraction of the released NOy had experienced loss, most likely as HNO3 by deposition. In the UT-plume, loss of NOy and SO2 was more pronounced compared to the MT-plume, probably due to cloud processes. Building on our measurements and accompanying model simulations, we have investigated trace gas transformations in the ageing and diluting plumes and their role in smoke particle processing and activation. Emphasis was placed upon the formation of sulfuric acid and ammonium nitrate, and their influence on the activation potential of smoke particles. Our model simulations reveal that, after 13 August, the lower plume traveled across the Atlantic and descended to 1300 m and hereafter ascended again. During the travel across the Atlantic, the soluble mass fraction of smoke particles and their mean diameter increased sufficiently to allow the processed smoke particles to act as water vapor condensation nuclei already at very low water vapor supersaturations of only about 0.04%. Thereby, aged smoke particles had developed a potential to act as water vapor condensation nuclei in the formation of maritime clouds.

scholarly journals Cleaner Production of Chromium Oxide from Low Fe(II)-Chromite

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 460 ◽  
Author(s):  
Qing Zhao ◽  
Chengjun Liu ◽  
Peiyang Shi ◽  
Lifeng Sun ◽  
Maofa Jiang ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Sulfuric Acid Concentration ◽  
Acid Leaching ◽  
Processing Parameters ◽  
Dissolution Behavior ◽  
Optimum Process ◽  
Process Conditions ◽  
Box Behnken Design ◽  
Functional Relationships ◽  
Leaching Process

Sulfuric acid-based leaching is a promising cleaner method to produce chromium salts, but its feasibility for treating low Fe(II)-chromite still remains to be proven. A Box–Behnken design (BBD)-based set of experiments for sulfuric acid leaching of low Fe(II)-chromite was utilized in this work for generating an experimental dataset for revealing the functional relationships between the processing parameters and the extraction yields of Cr and Fe. The dependent variables were found to exhibit strong intercorrelations and the models developed on the basis of statistical criteria showed excellent prediction accuracy. The optimum process conditions of leaching treatment were found to be a temperature of 176 °C, a dichromic acid/chromite mass ratio of 0.12, and a sulfuric acid concentration of 81%. Furthermore, the dissolution behavior of chromite in the leaching process and the effect of dichromic acid were experimentally investigated. It was found that the decomposition efficiency was highly dependent on the Fe(II) content of chromite, and that the dichromic acid acted both as an oxidant and a catalyst in the leaching process. On the basis of the results of this study, a novel process for treating low-Fe(II) chromite was proposed.

Application of genetic algorithms to determine heavy metal ions sorption dynamics on clinoptilolite bed

2012 ◽  
Vol 33 (1) ◽  
pp. 103-116 ◽  
Author(s):  
Elwira Tomczak ◽  
Władysław Kamiński
Keyword(s):  
Heavy Metal ◽  
Genetic Algorithms ◽  
Metal Ions ◽  
Heavy Metal Ions ◽  
Water Solution ◽  
Low Cost ◽  
Breakthrough Curves ◽  
Process Conditions ◽  
Global Extremum ◽  
Sorption Dynamics

Application of genetic algorithms to determine heavy metal ions sorption dynamics on clinoptilolite bed In the last decade a growing interest was observed in low-cost adsorbents for heavy metal ions. Clinoptilolite is a mineral sorbent extracted in Poland that is used to remove heavy metal ions from diluted solutions. The experiments in this study were carried out in a laboratory column for multicomponent water solutions of heavy metal ions, i.e. Cu(II), Zn(II) and Ni(II). A mathematical model to calculate the metals' concentration of water solution at the column outlet and the concentration of adsorbed substances in the adsorbent was proposed. It enables determination of breakthrough curves for different process conditions and column dimensions. The model of process dynamics in the column took into account the specificity of sorption described by the Elovich equation (for chemical sorption and ion exchange). Identification of the column dynamics consisted in finding model coefficients β, KE and Deff and comparing the calculated values with experimental data. Searching for coefficients which identify the column operation can involve the use of optimisation methods to find the area of feasible solutions in order to obtain a global extremum. For that purpose our own procedure of genetic algorithm is applied in the study.

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