Water purification capacity of natural mixed clays from Malawi
Lack of fresh and clean drinking water is a problematic issue for many people worldwide. The water quality in some streams in Malawi, situated in south east Africa, has recently been investigated. The study shows that the concentration of several heavy metals exceeds the guideline values in drink...
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| Format: | Otro |
| Language: | Swedish Inglés |
| Published: |
2009
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| Subjects: | |
| Online Access: | https://stud.epsilon.slu.se/12353/ |
| _version_ | 1855572047677095936 |
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| author | Hernell, Anna |
| author_browse | Hernell, Anna |
| author_facet | Hernell, Anna |
| author_sort | Hernell, Anna |
| collection | Epsilon Archive for Student Projects |
| description | Lack of fresh and clean drinking water is a problematic issue for many people worldwide.
The water quality in some streams in Malawi, situated in south east Africa, has recently
been investigated. The study shows that the concentration of several heavy metals
exceeds the guideline values in drinking water set by WHO. Even though some heavy
metals are essential for human beings in low concentrations, they are hazardous to health
in high concentrations. Problems with contaminated water exist all over the world but
are striking and more difficult to solve in countries with low financial assets. It is
therefore of great importance to find an effective technique to purify water that is both
simple and cheap and where preferably domestic material is used.
The aim of this study is to investigate whether three natural mixed clays from Malawi
can be used to purify contaminated water from the heavy metals chromium(III), lead(II),
cadmium(II), copper(II) and zinc(II) through adsorption.
X-ray powder diffraction analyses proved that all samples contained quartz, and
indicated presence of the iron oxide hematite. The chemical content of the samples was
determined with a scanning electron microscope. Acid and base titrations were
thereafter performed on raw material as well as on clay that had been purified from
organic matter, carbonates and iron compounds, to obtain information regarding the
chemical properties of the clay minerals. Finally, adsorption experiments were carried
out by mixing the clays with heavy metal solutions and study the adsorption as function
of pH.
The pH values of the investigated clays are naturally high, which promotes hydrolyses of
chromium(III) and lead(II) to precipitate and get sorbed on the surface. Cadmium(II),
copper(II) and zinc(II) form on the contrary surface complexes, mainly inner-sphere
ones. The adsorption of chromium(III), lead(II) and copper(II) was complete at pH = 7
for the purified clays, whereas cadmium(II) and zinc(II) were adsorbed to only 77 and
75 %, respectively, at pH ≈ 7.5. However, all metals are in principle completely
removed from the aqueous phase in the raw material, which indicates that these nontreated
natural clays are highly potential in heavy metal removal. |
| format | Otro |
| id | RepoSLU12353 |
| institution | Swedish University of Agricultural Sciences |
| language | Swedish Inglés |
| publishDate | 2009 |
| publishDateSort | 2009 |
| record_format | eprints |
| spelling | RepoSLU123532025-04-01T06:47:03Z https://stud.epsilon.slu.se/12353/ Water purification capacity of natural mixed clays from Malawi Hernell, Anna Dept. of Soil and Environment Water resources and management Lack of fresh and clean drinking water is a problematic issue for many people worldwide. The water quality in some streams in Malawi, situated in south east Africa, has recently been investigated. The study shows that the concentration of several heavy metals exceeds the guideline values in drinking water set by WHO. Even though some heavy metals are essential for human beings in low concentrations, they are hazardous to health in high concentrations. Problems with contaminated water exist all over the world but are striking and more difficult to solve in countries with low financial assets. It is therefore of great importance to find an effective technique to purify water that is both simple and cheap and where preferably domestic material is used. The aim of this study is to investigate whether three natural mixed clays from Malawi can be used to purify contaminated water from the heavy metals chromium(III), lead(II), cadmium(II), copper(II) and zinc(II) through adsorption. X-ray powder diffraction analyses proved that all samples contained quartz, and indicated presence of the iron oxide hematite. The chemical content of the samples was determined with a scanning electron microscope. Acid and base titrations were thereafter performed on raw material as well as on clay that had been purified from organic matter, carbonates and iron compounds, to obtain information regarding the chemical properties of the clay minerals. Finally, adsorption experiments were carried out by mixing the clays with heavy metal solutions and study the adsorption as function of pH. The pH values of the investigated clays are naturally high, which promotes hydrolyses of chromium(III) and lead(II) to precipitate and get sorbed on the surface. Cadmium(II), copper(II) and zinc(II) form on the contrary surface complexes, mainly inner-sphere ones. The adsorption of chromium(III), lead(II) and copper(II) was complete at pH = 7 for the purified clays, whereas cadmium(II) and zinc(II) were adsorbed to only 77 and 75 %, respectively, at pH ≈ 7.5. However, all metals are in principle completely removed from the aqueous phase in the raw material, which indicates that these nontreated natural clays are highly potential in heavy metal removal. Att inte ha tillgång till rent dricksvatten är verklighet för många människor runt om i världen. En undersökning av vattenkvaliteten i några floder i Malawi, i sydöstra Afrika, visar att koncentrationen av ett flertal tungmetaller kraftigt överstiger de gränsvärden som världshälsoorganisationen WHO har slagit fast. Trots att vissa tungmetaller är livsnödvändiga i låga koncentrationer så kan de i för höga halter ha mycket negativa hälsoeffekter. Problem av dessa slag förekommer på många håll, men slår kanske hårdast mot de länder som har små ekonomiska tillgångar. Det finns därför ett stort behov av att utveckla en effektiv reningsmetod som är både enkel och billig och där inhemskt material kan nyttjas. Denna studie syftar till att undersöka huruvida tre olika naturliga leror från Malawi kan användas för att rena kontaminerat vatten från tungmetallerna krom(III), bly(II), kadmium(II), koppar(II) och zink(II) genom adsorption. Med hjälp av pulverröntgendiffraktion kunde det konstateras att alla prover innehåller kiseloxiden kvarts. Det fanns även tecken på att järnoxiden hematit förekommer. Proverna studerades i ett svepelektronmikroskop utrustad med röntgenfluorescensdetektor, vilket möjliggjorde bestämning av grundämnessammansättningen. Genom syra- och bastitreringar på råmaterial samt lera som renats från organiskt material, karbonater och järnföreningar erhölls information om lerytornas kemiska egenskaper. Slutligen genomfördes studier där lera blandades med tungmetallösningar och adsorptionsgraden undersöktes vid olika pH-värden. Lerorna har naturligt ett högt pH-värde vilket främjar hydrolys av krom(III) och bly(II) som därmed faller ut och fastnar på ytorna. De andra studerade tungmetallerna, kadmium(II), koppar(II) och zink(II), adsorberades troligen till ytorna genom bildning av ytkomplex, främst av typen innersfärskomplex. Adsorptionen av krom(III), bly(II) och koppar(II) var fullständig vid pH = 7 i de renade jordarna, medan kadmium(II) och zink(II) endast adsorberades till 77 respektive 75 % i det undersökta pH-intervallet. I de orenade jordarna var däremot samtliga metaller i princip fullständigt avlägsnade från vattenfasen, vilket indikerar att dessa orenade naturliga leror har stor potential att kunna användas i vattenreningssyfte. 2009-11-06 Other NonPeerReviewed application/pdf sv https://stud.epsilon.slu.se/12353/1/hernell_a_171018.pdf Hernell, Anna, 2009. Water purification capacity of natural mixed clays from Malawi. UNSPECIFIED, Uppsala. Uppsala: (NL, NJ) > Dept. of Soil and Environment <https://stud.epsilon.slu.se/view/divisions/OID-435.html> urn:nbn:se:slu:epsilon-s-7982 eng |
| spellingShingle | Dept. of Soil and Environment Water resources and management Hernell, Anna Water purification capacity of natural mixed clays from Malawi |
| title | Water purification capacity of natural mixed clays from Malawi |
| title_full | Water purification capacity of natural mixed clays from Malawi |
| title_fullStr | Water purification capacity of natural mixed clays from Malawi |
| title_full_unstemmed | Water purification capacity of natural mixed clays from Malawi |
| title_short | Water purification capacity of natural mixed clays from Malawi |
| title_sort | water purification capacity of natural mixed clays from malawi |
| topic | Dept. of Soil and Environment Water resources and management |
| url | https://stud.epsilon.slu.se/12353/ https://stud.epsilon.slu.se/12353/ |