scholarly journals Gas Antisolvent Fractionation: a New Method to Obtain Enantiopure Compounds, a Case Study on Mandelic Acid

2018 ◽  
Vol 63 (1) ◽  
pp. 130-137 ◽  
Author(s):  
Márton Kőrösi ◽  
Attila Sedon ◽  
Kinga Komka ◽  
Tamás Sohajda ◽  
Edit Székely
Keyword(s):  
Mandelic Acid ◽  
Fine Particles ◽  
Racemic Mixture ◽  
Operational Parameters ◽  
Batch Type ◽  
Equivalent Quantity ◽  
Molar Equivalent ◽  
Gas Antisolvent ◽  
Diastereomeric Excess

Micronization processes involving supercritical carbon dioxide are rapid methods to produce fine particles. They also might offer the possibility of using less organic solvent than conventional crystallization methods leading to an environmentally friendlier processing. The separation capabilities of such processes are now demonstrated on the diastereomeric resolution of mandelic acid using (R)-1-phenylethanamine as a resolving agent, utilizing the batch type gas antisolvent fractionation as the separation method. A detailed study was conducted on the effects of the operational parameters pressure (12-20 MPa), temperature (35-55 °C) and co-solvent concentration (33-99 mg/ml). At 12 MPa, 35 °C and 99 mg/ml methanol concentration, a selectivity of 0.52 and a diastereomeric excess of 62% was reached. The same operational parameters were applied during the investigation of the recrystallization-based further purification of the diastereomeric salts, applying the resolving agent in molar equivalent quantity to a non-racemic mixture of mandelic acid. It has been found that the more stable (R)-1-phenylethylammonium-(R)-mandelate salt can be purified to de>98% through four additional recrystallization steps following the initial, half-molar equivalent resolution step.

scholarly journals Optimizing Flotation Circuit Recovery by Effective Stage Arrangements: A Case Study

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 417 ◽  
Author(s):  
Vahid Radmehr ◽  
Sied Shafaei ◽  
Mohammad Noaparast ◽  
Hadi Abdollahi
Keyword(s):  
General Rule ◽  
Optimal Recovery ◽  
Operational Parameters ◽  
Matlab Software ◽  
One Stage ◽  
Additional Costs ◽  
Circuit Configuration

Recovery is one of the most important metallurgical parameters in designing and evaluating flotation circuits. The present study used the recovery arrangement for two and three stage circuits to evaluate the effect of stage recovery on the overall circuit recovery and flotation circuit configuration. The results showed that mainly the highest recovery value should be assigned to the rougher stage in order to achieve the maximum overall circuit recovery. Countercurrent rougher-cleaner and rougher-scavenger circuits, in which recycling streams step back one stage at a time, follow a general rule for the assignment of recovery. Finally, a flotation plant containing six flotation banks was examined as a case study. A program for calculating total circuit recovery, for all possible combinations of recovery was developed in MATLAB software. 720 recovery combinations were evaluated. The results showed that optimal recovery allocation in stages could be effective in achieving overall circuit recovery. It was shown that the use of a large number of stages in some of the flotation circuits leads to the loss of equipment and additional costs. The proposed approach can be employed as an effective tool for designing and optimizing various flotation circuits and their operational parameters.

Parameters affecting nitrifying biofilm reactors

1994 ◽  
Vol 29 (10-11) ◽  
pp. 1-11 ◽  
Author(s):  
M. Boller ◽  
W. Gujer ◽  
M. Tschui
Keyword(s):  
High Energy ◽  
Experimental Investigations ◽  
Operational Parameters ◽  
Oxygen Utilization ◽  
Trickling Filters ◽  
Biofilm Reactors ◽  
Biomass Activity ◽  
Rotating Biological Contactors ◽  
High Energy Consumption

The variables affecting nitrification in biofilms are identified on a theoretical basis. The influence of various design and operational parameters which affect the resulting substance fluxes into and out of the biofilm and the biomass activity regarding nitrification are illustrated with the help of experimental investigations with plastic media trickling filters, rotating biological contactors and different aerated biofilters. The results of experiments with these systems in tertiary nitrification applications reveal process limitations and technical measures to enhance nitrification performance in each system. In a case study, a comparison between the different biofilm processes and activated sludge alternatives showed that biofilm systems may lead to remarkably smaller reactor volumes, but high energy consumption due to unfavorable oxygen utilization.

The effect of SDE on the separation of diastereomeric salts: a case study for the resolution of mandelic acid derivatives with Pregabalin

2014 ◽  
Vol 25 (15) ◽  
pp. 1095-1099 ◽  
Author(s):  
Zsolt Szeleczky ◽  
Péter Bagi ◽  
Emese Pálovics ◽  
Elemér Fogassy
Keyword(s):  
Mandelic Acid ◽  
Diastereomeric Salts ◽  
Mandelic Acid Derivatives

Sub-type source profiles of fine particles for fugitive dust and accumulative health risks of heavy metals: a case study in a fast-developing city of China

2020 ◽  
Vol 27 (14) ◽  
pp. 16554-16573 ◽  
Author(s):  
Fangqi Wu ◽  
Shaofei Kong ◽  
Qin Yan ◽  
Wei Wang ◽  
Haibiao Liu ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Health Risks ◽  
Fine Particles ◽  
Fugitive Dust ◽  
Source Profiles

scholarly journals Microwave-Assisted Synthesis of(±)-Mandelic Acid-d5, Optical Resolution, and Absolute Configuration Determination

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Claudio Bruno ◽  
Giovanni Lentini ◽  
Angelo Lovece ◽  
Maria Maddalena Cavalluzzi ◽  
Alessia Carocci ◽  
...  
Keyword(s):  
Capillary Electrophoresis ◽  
Mandelic Acid ◽  
Optical Resolution ◽  
Racemic Mixture ◽  
Microwave Assisted Synthesis ◽  
Salt Formation ◽  
Microwave Assisted ◽  
Diastereomeric Salts ◽  
Chiral Capillary Electrophoresis ◽  
Resolving Agents

An efficient microwave-assisted synthesis of(±)-mandelic acid-d5was developed. The racemic mixture was resolved by diastereomeric salt formation using 1-phenylethylamine enantiomers as resolving agents. At each step, the resolution process was checked by determining mandelic acid-d5enantiomer ee values directly on fractional crystallized diastereomeric salts by chiral capillary electrophoresis analysis. Highly enriched (−)- and (+)-mandelic acid-d5(95% and 90% ee, resp.) were obtained and their absolute configurations—RandS, respectively—were determined by correlation of the (−)-mandelic acid-d5circular dichroism spectrum to the (R)-mandelic acid one.

scholarly journals Application of electrocoagulation for water conditioning

2019 ◽  
Vol 6 (2) ◽  
pp. 59-70
Author(s):  
Hana Posavčić ◽  
Ivan Halkijević ◽  
Živko Vuković
Keyword(s):  
Water Source ◽  
Point Of View ◽  
Pollutant Removal ◽  
Operating Costs ◽  
Mechanical Equipment ◽  
Operational Parameters ◽  
Economic Point ◽  
Water Conditioning ◽  
Electrocoagulation Process

Water conditioning is a method of removing altering minerals, chemicals and contaminants from a water source and it is carried out on facilities equipped with the corresponding electro-mechanical equipment. Although efficient, conventional processes typically use several complex devices connected to a single functional unit, which are often expensive to maintain and occupy large areas. Therefore, the aim of this paper is to present the electrocoagulation (EC) method as an alternative to conventional water conditioning processes. The examples of previous studies of the EC process application is presented in this paper. The focus of the paper is to investigate the influence of the certain operational parameters such as pH, temperature, electrode material, etc., on the efficiency of pollutant removal such as Escherichia coli and elevated concentrations of iron, arsenic, manganese, ammonia and others. Further, an economic analysis is made, which, from an economic point of view, shows when it is feasible to use the EC in the conditioning process. Furthermore, a case study of electrocoagulation process for Total Nitrogen (TN) removal is presented. According to results, 69.7 % of TN was removed with aluminum electrodes after 240 minutes. For this case, total operating costs were 7.60 €/m3.

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