Techno Press

Advances in Environmental Research   Volume 2, Number 1, March 2013, pages 35-49
Enhancement effect of phosphate and silicate on water defluoridation by calcined gypsum
Aiman Eid Al-Rawajfeh, Albara I. Alrawashdeh, Asma Aldawdeyah, Shorouq Hassan and Ruba Qarqouda

Abstract     [Full Text]
    Research work on removal of fluoride from water, referred to as water defluoridation, has resulted into the development of a number of technologies over the years but they suffer from either cost or efficiency drawbacks. In this work, enhancement effects of phosphate and silicate on defluoridation of water by low-cost Plaster of Paris (calcined gypsum) were studied. To our knowledge, the influence of silicate on defluoridation was not reported. It was claimed, that the presence of some ions in the treated water samples, was decreasing the fluoride removal since these ions compete the fluoride ions on occupying the available adsorption sites, however, phosphate and silicate ions, from its sodium slats, have enhanced the fluoride % removal, hence, precipitation of calcium-fluoro compounds of these ions can be suggested. Percentage removal of F- by neat Plaster is 48%, the electrical conductance (EC) curve shows the typical curve of Plaster setting which begins at 20 min and finished at 30 min. The addition of phosphate and silicate ions enhances the removal of fluoride to high extent > 90%. Thermodynamics parameters showed spontaneous fluoride removal by neat Plaster and Plaster-silicate system. The percentage removal with time showed second-order reaction kinetics.
Key Words
    water treatment; plaster of Paris; calcined gypsum; adsorption; co-precipitation
1Aiman Eid Al-Rawajfeh,Shorouq Hassan and Ruba Qarqouda: Tafila Technical University (TTU), Department of Chemical Engineering, P.O. Box 179, 66110 Tafila, Jordan;
2Aiman Eid Al-Rawajfeh: Jordan Atomic Energy Commission (JAEC), Shafa Badran, Amman, Jordan;
3Asma Aldawdeyah: Tafila Technical University (TTU), Department of Chemistry, P.O. Box 179, 66110 Tafila, Jordan

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