Abstract
The objective of this study was to investigate the production of activated carbons (AC) from cashewshells, and millet stalks and their efficiency in fluoride retention. These agricultural residues arecollected from Senegal. It is known that some regions of Senegal, commonly called the groundnutbasin, are affected by a public health problem caused by an excess of fluoride in drinking water usedby these populations. The activated carbons were produced by a combined pyrolysis and activationwith water steam; no other chemical compounds were added. Then, activated carbonaceous materialsobtained from cashew shells and millet stalks were called CS-H2O and MS-H2O respectively. CS-H2O and MS-H2O show very good adsorbent features, and present carbon content ranges between71% and 86%. The BET surface areas are 942 m2:g????1 and 1234 m2:g????1 for CS-H2O and MS-H2Orespectively. A third activated carbon produced from food wastes and coagulation-flocculation sludge(FW/CFS-H2O) was produced in the same conditions. Carbon and calcium content of FW/CFS-H2O are 32.6 and 39.3% respectively. The kinetics sorption were performed with all these activatedcarbons, then the pseudo-first equation was used to describe the kinetics sorption. Fluoride adsorptionisotherms were performed with synthetic and natural water with the best activated carbon fromkinetics sorption, Langmuir and Freundlich models were used to describe the experimental data.Regarding equilibrium data, the experimental data are better described by Langmuir model than bythe Freundlich model. The results showed that carbonaceous materials obtained from CS-H2O andMS-H2O were weakly efficient for fluoride removal. With FW/CFS-H2O, the adsorption capacity is28:48 m2:g????1 with r2 = 0:99 with synthetic water.
Published Version
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