Water Treatment by Adsorption and Electrochemical RegenerationDevelopment of a Liquid-Lift Reactor

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Abstract

Efficient and economic treatment of low concentration organic pollutants in water, wastewater or industrial process streams is normally very difficult to achieve. Activated carbon has been widely used for contaminant adsorption, but there are problems associated with its regeneration. In this work, a novel, non-porous, highly-conducting graphite intercalation compounds material (GIC) is used. The use of such an adsorbent can significantly reduce the time required to achieve both equilibrium and electrochemical regeneration. This character allows the design of an innovative treatment process that can adsorb contaminants and electrochemically regenerate itself simultaneously within a single unit. A novel liquid-lift reactor for water treatment by an adsorption and electrochemical regeneration process is developed in this work. Batch experiments are carried out to determine the adsorption kinetics and equilibrium isotherm of adsorption Acid Violet 17 onto the GIC adsorbent. The experimental kinetic data are analyzed using the pseudo-first order, pseudo-second order, intra-particle diffusion and three-stage kinetic models. The linear pseudo-second order model offers the highest r2 correlation coefficient. The experimental isotherm data are analyzed using Langmuir, Freundlich and Tempkin isotherm models. The non-linear Langmuir model gives the highest r2 correlation coefficient. High regeneration efficiency (more than 90%) over a number of cycles is obtained by passing a charge of 6.4 C g-1 of the GIC adsorbent, at a current density of 5 mA cm-2 using a batch, sequential adsorption (60 min) and electrochemical regeneration (30 min) process. The simultaneous adsorption and regeneration process indicates that 100 % AV 17 can be removed in 60 min (4L of 100 mg L-1 AV 17 solution, 140g of the GIC adsorbent, current density of 5mA cm-2). The flow behaviour in the electrochemical reactor has been studied using a pulse tracer technique. The residence time distribution shows that the flow behaviour in the liquid-spouted reactor can be regarded as a plug flow in series with a continuous stirred tank reactor. For the batch adsorption system, a “parallel adsorption barren well hypothesis” is proposed in this thesis. For the batch simultaneous adsorption and electrochemical regeneration system, a multi-parameter model is proposed in this thesis.

Layman's Abstract

Efficient and economic treatment of low concentration organic pollutants in water, wastewater or industrial process streams is normally very difficult to achieve. Activated carbon has been widely used for contaminant adsorption, but there are problems associated with its regeneration. In this work, a novel, non-porous, highly-conducting graphite intercalation compounds material (GIC) is used. The use of such an adsorbent can significantly reduce the time required to achieve both equilibrium and electrochemical regeneration. This character allows the design of an innovative treatment process that can adsorb contaminants and electrochemically regenerate itself simultaneously within a single unit. A novel liquid-lift reactor for water treatment by an adsorption and electrochemical regeneration process is developed in this work. Batch experiments are carried out to determine the adsorption kinetics and equilibrium isotherm of adsorption Acid Violet 17 onto the GIC adsorbent. The experimental kinetic data are analyzed using the pseudo-first order, pseudo-second order, intra-particle diffusion and three-stage kinetic models. The linear pseudo-second order model offers the highest r2 correlation coefficient. The experimental isotherm data are analyzed using Langmuir, Freundlich and Tempkin isotherm models. The non-linear Langmuir model gives the highest r2 correlation coefficient. High regeneration efficiency (more than 90%) over a number of cycles is obtained by passing a charge of 6.4 C g-1 of the GIC adsorbent, at a current density of 5 mA cm-2 using a batch, sequential adsorption (60 min) and electrochemical regeneration (30 min) process. The simultaneous adsorption and regeneration process indicates that 100 % AV 17 can be removed in 60 min (4L of 100 mg L-1 AV 17 solution, 140g of the GIC adsorbent, current density of 5mA cm-2). The flow behaviour in the electrochemical reactor has been studied using a pulse tracer technique. The residence time distribution shows that the flow behaviour in the liquid-spouted reactor can be regarded as a plug flow in series with a continuous stirred tank reactor. For the batch adsorption system, a “parallel adsorption barren well hypothesis” is proposed in this thesis. For the batch simultaneous adsorption and electrochemical regeneration system, a multi-parameter model is proposed in this thesis.

Keyword(s)

Acid Violet 17; Adsorption ; Electrochemical regeneration ; Graphite intercalation compound; Liquid spouted bed reactor

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