The potential human health issues resulting from the continuous consumption of drinking water containing low concentration levels of persistent emerging pollutants has raised some concerns. The presence of emerging pollutants in surface water bodies and ground-water in Canada together with absence of proper drinking water treatment processes in remote places has created the need for an effective and simple process for removal of emerging pollutants from drinking water. Low seasonal temperatures in regions such as Saskatchewan demand a removal process that is effective at temperatures lower than room temperature. Adsorption with granular activated carbon is a well-established and effective method for removal of organic compounds from drinking water. There are a large number of reports on removal of organic compounds by activated carbon in literature however, the effectiveness of adsorption of emerging pollutants with granular activated carbon is not clear. Effectiveness of ozone treatment for oxidation of emerging pollutants is reported in literature however, effectiveness of regeneration of adsorbents saturated with emerging pollutants with ozone has not been investigated extensively.
In the present work, effectiveness of adsorption with granular activated carbon for removal of emerging pollutants is investigated. Three model compounds of Ibuprofen, 2,4-dichlorophenoxyacetic acid, and Bisphenol A reported at considerable concentration levels in Saskatchewan water bodies were selected as model compounds. Bituminous coal based and coconut shell based granular activated carbons with basic point of zero charge were selected as adsorbents. Isotherm adsorption of model compounds on adsorbents was conducted at 280, 288, and 296 K. The Gibbs free energy, enthalpy, and entropy of adsorption were calculated using isotherm model parameters. Nitric acid pre-treatment was applied to reduce the point of zero charge of adsorbents. Adsorption isotherms were conducted with the acid treated adsorbents. Adsorption removal of model compounds in tap water was studied. Effectiveness of regeneration of saturated adsorbents with ozone was investigated.
In terms of quality of fit to the isotherm adsorption data, Langmuir model was better than Freundlich model indicating monolayer adsorption of model compounds in all experiments. Higher Langmuir monolayer adsorption capacity (Qmax) of bituminous coal based adsorbent than coconut shell adsorbent for adsorption of model compounds was attributed to the higher porosity of bituminous coal based adsorbent. Adsorption of model compounds (i.e. IBP and BPA) present in molecular form in the pH condition of the experiments were more dependent on adsorbent surface functional groups e.g. carboxyl and carbonyl groups. The Qmax of adsorption of 2,4-D present in anionic form was proportional with the specific surface area of adsorbent. Adsorption at temperatures lower than room temperature was effective. Adsorbent with acidic point of zero charge was more effective in removal of model compounds than adsorbent with basic point of zero charge. Adsorption of BPA was higher in tap water in comparison to Millipore water due to the more neutral surface of adsorbent in tap water. Higher pH of tap water than Millipore water and the ionic interaction between the adsorbent and dissolved solids present in tap water caused the more neutral surface of adsorbent. Regeneration of adsorbents with ozone failed in restoration of adsorption capacity of adsorbents and excessive ozonation destroyed the pore structure of adsorbents.
| Identifer | oai:union.ndltd.org:USASK/oai:ecommons.usask.ca:10388/ETD-2014-11-1827 |
| Date | 2014 November 1900 |
| Contributors | Soltan, Jafar |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text, thesis |
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