University of Oulu, Finland
Anni Keränen received her Master’s degree in environmental engineering in 2012 from the University of Oulu, Finland. After graduation, she started her PhD studies under the supervision of Prof. Juha Tanskanen and Dr. Tiina Leiviskä at the University of Oulu. Her research interests are water treatment, ion exchange, adsorption and biomass-based water treatment chemicals. She is planning to defend her doctoral thesis in 2016.
The utilization of biomass in the production of water treatment chemicals has gained interest over the past few decades. Lignocellulose is an attractive raw material because of its wide availability, low cost, reactive chemical structure and renewability. Chemical modification is required to enhance the anion binding properties of lignocellulose. We used Finnish pine sawdust to produce an anion exchange resin through chemical modification with epichlorohydrin, ethylenediamine, triethylamine and N,N-dimethylformamide, aiming to add cationic, quaternary, ammonium groups in the sawdust structure. Elemental analyses revealed that the modification increased the sawdust’s nitrogen content from 0.8% to 9.4%. Sorption tests using synthetic nitrate solutions were conducted. Nitrate was chosen because it causes severe health problems in drinking water and contributes to eutrophication in water systems. The resin proved to work in a wide pH (3–10) and temperature range (5–70°C), and the sorption of nitrate was very rapid. In column, the resin maintained its capacity for five ion exchange and desorption cycles tested. A maximum sorption capacity of 30.1 mg/g was achieved for NO3--N. The effects of phosphate and sulphate were also studied. Significant inhibition in nitrate reduction (initially 30 mg NO3--N/L) was observed at 50 mg P/L and 100 mg S/L. The results imply that modified sawdust could compete with commercial anion exchange resins. The next step of the study is to develop the modification method into being more environmentally sound and study nitrate removal from industrial and mining wastewaters.
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