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Title: Development of graphitic adsorbents for water treatment using adsorption and electrochemical regeneration
Author: Asghar, Hafiz Muhammad Anwaar
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2011
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In order to address ground and industrial water pollution, the University of Manchester has developed a novel and economic water treatment technology called the Arvia® process. This technology is being commercialized through a spin-out company, Arvia Technology Ltd. This process consists of adsorption and electrochemical regeneration in a single unit and can be carried out in batch or continuous modes where both operations can run simultaneously. This process has been successfully demonstrated for the removal and destruction of a number of organic contaminants using a graphite based adsorbent known as Nyex®1000. Nyex®1000 is an intercalation compound prepared from Chinese natural large fake graphite. This adsorbent has been found to be capable of fast adsorption and quick electrochemical regeneration in minutes due to its non-porous surface and high electrical conductivity. However, Nyex®1000 has a small adsorptive capacity for a number of organic pollutants and there is thus a need to develop new adsorbents with the aim of achieving high adsorptive capacity with maintaining good electrical conductivity. In this context, three routes for the development of adsorbents were selected, adsorbents developed through electrochemical intercalation, adsorbent developed through thermal and mechanical treatment of GIC-bisulphate and adsorbents developed through the formulation of composite materials. In order to strengthen the contributing effect of surface treatment, all raw graphite materials and developed adsorbents were characterized using Boehm titration, X-ray EDS, zeta potential, powder XRD, SEM, BET surface area, pore volume, particle size and bulk density techniques. These adsorbents were tested for the removal of a number of different target organic pollutants such as acid violet 17, mercaptans, phenol and humic acid using the Arvia® process. The performance of the developed materials was compared with the current adsorbent used in the Arvia® process i.e. Nyex®1000. A range of graphite types (synthetic graphite, Chinese natural large fake gra- phite, Madagascan medium fake graphite, natural vein graphite and recycled Abstract 27 vein graphite) were tested for the removal of acid violet 17 before and after electrochemical treatment in order to investigate the selection of the graphite types for the Arvia® process. The electrochemical surface treatment improved the adsorptive capacity by a factor of two for most of the graphite types tested and changed the surface of the graphite from hydrophobic to hydrophilic. Results obtained through surface characterization using Boehm titration, X-ray (EDS) elemental analysis and zeta potential measurements revealed a significant increase in oxygen containing surface functional groups on the surface of CNLFG in consequence of electrochemical surface treatment. The second type of adsorbent was developed through thermal and mechanical treatment of GIC bisulphate. It was tested for the removal of acid violet 17, mercaptans (ethane thiol & methyl propane thiol), phenol and humic acid using the Arvia® process. This material had twice the electrical conductivity of Nyex® 1000 and improved the adsorptive capacity by a factor of three for acid violet 17, approximately seven to eight for ethane thiol and methyl propane thiol, seven for phenol and two for humic acid. Starting and developed adsorbent materials were characterized using above mentioned techniques. The third type of adsorbent materials, three composite adsorbents were developed using high shear (wet) and compaction (dry) granulation methods. The composite adsorbent made through high shear wet granulation was found to have poor mechanical strength. The second and third composite adsorbents were developed through dry compaction granulation using carbon black, synthetic graphite and exfoliated graphite as raw materials. These adsorbents delivered improved adsorptive capacity for acid violet 17 by a factor of 100 and 9 respectively. Electrochemical regeneration efficiencies of around 100 % were obtained for these adsorbent materials. However, electrochemical parameters required to achieve 100 % regeneration, such as current density and regeneration time were found to vary depending on the adsorptive capacity of each adsorbent material for a particular polluting agent.
Supervisor: Roberts, Ted Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: adsorption ; electrochemical regeneration ; graphitic