Increasing concern about the pollution of environment by inorganic and organic chemicals arising from naturally occurring ecological events and industrial processes has created a need for the search of new techniques in the removal of these contaminants.
One of the natural material that can be used in such processes is clay. Clay minerals have large surface areas and high cation exchange capacities which enables them to be modified by cationic surfactants. The material prepared, often called as & / #8216 / organoclay& / #8217 / , can be used to remove hydrophobic organic and anionic contaminants from polluted water.
Among the anionic contaminants, oxyanions such as nitrate, chromate are detrimental to human life and environment even at µ / g/L- mg/L levels. Application of organoclays for their removal from polluted water appears as one of the practical and rather cheap solution.
In this study, a local clay from Ankara-Kalecik (Hanç / ili Bentonite) was modified by hexadecyltrimethylammonium bromide (HDTMA-Br) to a level of twice of its cation exchange capacity. This process alters the negatively charged surface of the clay into a positively charged one, providing sites for the removal of anionic contaminants. In this study, the degree of HDTMA+ uptake by the clay within a period of eight hours is found to be 97% of the initial amount added.
In desorption studies it was revealed that only about 1% of the sorbed HTDMA+ was leached in a seven days of water-organoclay interaction revealing a rather stable organoclay structure in aqeous media.
Sorption experiments with nitrate, borate, and chromate solutions were performed in order to determine the anion sorption capacity of the organoclays prepared. It turns out that while untreated clay has insignificant capacity, the modified clay can remove considerable amount of nitrate and chromate ions from aqeous solutions. While the nitrate sorption was increased about eleven fold, change in chromate sorption was reached to a level of twenty fold compared to that of the untreated clay. Sorption data for nitrate and chromate are both well described by the Langmuir isotherms. No significant change was observed in case of borate-organoclay interaction. Desorption of nitrate and chromate ions from organoclay surface were also investigated. Sorption of these oxyanions were found to be almost irreversible in aqeous media.
The results imply that a properly prepared organoclay can be used for the removal of oxyanions, such as nitrate and chromate from polluted water systems.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12606674/index.pdf |
| Date | 01 September 2005 |
| Creators | Inam, Deniz |
| Contributors | Gokturk, Emine Hale |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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