Clays from the Bafang region (West Cameroon): Properties and potential application as decolorizing agent of river water

A clay sample from the Bafang region (Cameroon) was analysed by a number of techniques which include grain size distribution, major and trace elementʹs determination, thermogravimetry, X-ray diffraction and scanning electron microscopy. The clay had an average magnetite content of 20%. The fine clay fraction with 25% of the raw material consisted of kaolinite/halloysite and goethite and magnetite as associated minerals. The study of decolouration of river waters showed that the clay can be used as adsorbent. Amounts of 8–9% discoloured the Nyong River waters from 267 to 33 PtCo colour units. When the pH of the water was lowered to 4.7 with sulfuric acid, only 4% clay was required and the colour obtained was 27 PtCo. The adsorption of humic substances on the clay was indicated by the IR adsorption bands of the hydroxyl groups. Aluminum sulfate used as the reference material was not able to eliminate all humic substances from the Nyong waters. When the clay was used as an adsorbent after coagulation by aluminum sulfate, 1.5% clay permitted to attain a colouration of 6 PtCo units. The settling velocity of the clay particles in the water at 1.5% content, was higher than 1 m/h.