Abstract:
Consumption of potable water with high concentrations of fluoride causes serious health
issues. Fluoride ions are released into groundwater primarily as a result of rock erosion.
Among several methods for removal of fluoride from water, adsorption method receives
much attention because of its simplicity. In this context, amongst various materials,
calcium containing minerals and animal bones have been used. The present study is to
remove fluoride from water using a blend of coconut shell charcoal and eggshell powder
in a packed continuous flowing column system and in a simple batch system. The fluoride
removal efficiency (FRE) was determined as a percentage of the ratio of removed
concentration to the initial fluoride concentration. The effect of several factors such as
the ratio of the mass of coconut shell charcoal to the eggshell in the mixture, the flow rate
of fluid in the column system and contact time of water with adsorbents in batch system
were studied. Adsorbing materials in powder-form were prepared by breaking down precleaned
shells and heating in the oven at 1050 C for 3 hours and sieving through a 2 mm
sieve separately. The mixture of coconut shell charcoal and eggshell was prepared with
different mass ratios. Fluoride concentration in water was determined by colorimetric
method by measuring the colour intensity reduction of SPANDS reagent by Fluoride
ions. Calibration curve was prepared for known concentrations. The results demonstrate
that the continuous system is excellent for removing low initial fluoride concentrations
from water, whereas the batch method is best for removing high initial fluoride
concentrations. Different ratios of eggshell and coconut shell powder were prepared
separately. The eggshell Charcoal system's 3:1 ratio shows that approximately 97% and
65.5% of the initial concentration (0.5 ppm) of Fluoride ions could be removed in the
continuous flow and batch systems, respectively, in 8 hours. However, when the initial
concentration of Fluoride ions was increased to 4.5 ppm, only 51% of the initial
concentration was taken from the water, indicating that defloration is limited by the
eggshell surface. Results demonstrate that only the high efficiency of the eggshell powder
technique removes a high concentration of fluoride from water. Furthermore, Batch
system and column system effectively remove fluoride from potable water.
