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Gaurang V. Patankar

Final yr. Chemical Engineering

201001011028

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Fluoride in Ground Water Geogenic origin:

breakdown of rocks containing the fluoride ions

Anthropogenic sources:infiltration of chemical fertilizers in agricultural areas andliquid wastes from industrial entities.

Fluoride affected zones of the world

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Effects of fluoride on Human Body

Skeletal Fluorosis

Dental Fluorosis

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Technologies for removing fluoride

from water Non-treatment and blending techniques

Precipitation/coagulation

Membrane techniques

Ion exchange (IE)

Electrochemical technique (electro coagulation+

electro flotation)Adsorption using activated alumina, Zeolites etc.

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Onyango and Matsuda et al. Department of Chemical Engineering, Nagoya University, Nagoya, Japan

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Defluoridation in a packed columnBed depth service time model [BDST]

assumes reaction kinetics plays a limiting role inadsorption.

interaction between fluoride and the active sites followssecond-order kinetics.

St: total number of sites,

SF: the sites occupied by fluoride

St-SF: the sites available for reaction

rs: rate of reaction

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Defluoridation in a column

[SF] =q, [St]=qm, [F-]=c, kais the forward rate constant and

kdthe backward rate constant.

If the adsorbentfluoride bonding is strong, then ka> kd.

Bohart and Adams simplified the above expression for ionexchange as follows:

G.S. Bohart, E.Q. Adams, J. Chem. Soc. 42 (1920) 523.

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Material Balance on CV of Fixed Bed

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Material Balance on CV of Fixed BedAssumptions

fluoride removal is solely by adsorption onto the adsorbentparticles.

the system is assumed to be isothermal, non-equilibriumand non-adiabatic single-component fixed-bed adsorption.

For the control volume, Axdz, for a limiting situation z0,the material balance is given by,

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Material Balance on CV of Fixed Bed Solution:

Linearized form:

for Ct=Cb(breakthrough concentration) Critical bed depth (t=0):

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Thank you for your patience!