Electrochemically controlled sorption processes on carbon electrodes

The brief overview of results obtained on electrochemical control in adsorption phenomena on carbon electrodes presented. As the examples, adsorption of phenol, benzoic acid and chloroform on the fixed flow-through beds of granulated and fiber carbon materials studied. The ability of surface charge control on electrochemically controlled adsorption phenomena is shown both from the choice of material and application of current. Polarization profiles of 3D-carbon electrodes measured. Characteristics of power consumption during electrochemical regeneration are determined. Laboratory scale experiments on water purification have shown the problems of electrochemical regeneration due to the accumulation of sorbate in the microporous structure of adsorbent.Представлен краткий обзор результатов изучения электрохимически управляемой адсорбции на углеродных материалах. В качестве примеров рассмотрена адсорбция фенола, бензойной кислоты и хлороформа на объемных проточных волокнистых и гранулированных электродах. Измерены профили потенциалов трехмерных углеродных электродов. Показана возможность управления зарядом поверхности электрода, как со стороны синтеза, так и наложением тока. В то же время, попытки очистки воды от органических веществ электросорбцией в циклическом режиме поглощения–регенерации натолкнулись на проблему накопления сорбата в микропористой структуре материала.Представлено короткий огляд результатів вивчення електрохімічно керованої адсорбції на вуглецевих матеріалах. Як приклади розглянуто адсорбцію фенолу, бензойної кислоти і хлороформу на проточних об’ємних волокнистих і гранульованих електродах. Виміряно профілі потенціалів об’ємних вуглецевих електродів. Показано можливість керування зарядом поверхні електрода як з боку синтезу, так і накладенням поляризації. У той же час, спроби очистки води від органічних речовин електросорбцією в циклічному режимі поглинання–регенерації наштовхнулися на проблему нагромадження сорбату в мікропористій структурі матеріалу

Electrothermal swing adsorption of toluene on an activated carbon monolith - Experiments and parametric theoretical study

International audienceThe purpose of the present work is to investigate electrothermal swing adsorption (ESA) process with an activated carbon monolith as adsorbent. Experiments are performed with toluene as VOC. Several parameters are investigated both experimentally and through a mathematical model. It is shown that the monolith, as a carbon material, behaves as a semi-conductor. Its resistivity decreases as temperature and amount adsorbed increase. This leads to different types of evolution of dissipated electrical power during desorption at constant current intensity. The concentration of the desorbed VOC as a function of time has the shape of a peak followed by a tail. This shape is interpreted as a dispersive wave in the sense of the equilibrium theory of adsorption columns. The performance of the process is strongly dependent on the operating conditions. The maximal (that is initial) concentration increases almost linearly with current intensity and purge gas flow rate, and increases also with preheating duration. The purge gas flow rate has mainly an effect of dilution. The efficiency of desorption (% VOC desorbed) is almost constant in average with different preheating times. It increases with current intensity and gas purge flow rate

Reactive ion exchange chromatography: Concentrations and separations of amino acids and peptides by means of an aqueous solution of carbon dioxide under pressure as displacer

The feasibility of the separation of peptides by ion exchange chromatography using an aqueous solution of carbon dioxide in water as displacer has been studied. Ion exchange equilibria have been measured for amino acids and dipeptides. Elutions at increasing pressures show the increase of recovered product concentration. Feasibility of displacement separations and dependence upon a global separation factor which takes into account both equilibria in the solution and affinities of the support towards the various molecules are proved. This factor is thus only based on thermodynamic considerations. In case it proves the feasibility of the separation, kinetic limitation considerations had to be taken into account to achieve the best separation

Adsorption and electrothermal desorption of organic vapors using activated carbon adsorbents with novel morphologies

International audienceNovel morphologies of activated carbons such as monolith, beads and fiber cloth can effectively capture organic vapors from industrial sources. These adsorbent materials are also unique because they can undergo direct electrothermal regeneration to recover the adsorbed organic vapors for potential re-use. This investigation compares and contrasts the properties of these adsorbents when using electrothermal–swing adsorption. The adsorption systems consisted of an organic vapor generation system, an electrothermal–swing adsorption vessel, a gas detection unit, and a data acquisition and control system. The activated carbon monolith (ACM) had the lowest pressure drop, highest permeability, highest electrical resistivity and lowest cost as compared to the activated carbon beads (ACB) and the activated carbon fiber cloth (ACFC). ACB had the largest throughput ratio and lowest length of unused bed as compared to the other adsorbents. However, ACFC had the largest adsorption capacity for toluene when compared to ACM and ACB. ACFC was also faster to regenerate and had a larger concentration factor than ACM and ACB. These results describe relevant physical, electrical, adsorption and cost properties for specific morphologies of the adsorbents to more effectively capture and recover organic vapors from gas streams