Abstract:
Finding low cost, environmentally friendly adsorbents with having higher removal
efficiencies are vital to improve the quality of drinking water in the regions where
groundwater is contaminated with fluorides. In Sri Lanka, this problem is apparent and
has been prevailing especially in the north-central province. Rice husk is claimed to have
better fluoride removal when used as an adsorbent. As a country known for its paddy
cultivation, the waste material of it, the rice husk would be cheaper if can be used as a
filter material. Therefore, this study was sought at investigating the efficiency of rice husk
as a filter material in removing fluoride from groundwater. For that, bio-waste rice husk
was converted to activated carbon by thermal activation and through merely treating with
H3PO4. Characterization of Rice Husk Activated Carbon (RHAC) was carried out using
the following methods: Fourier Transform Infra-Red (FT-IR), physical properties such as
moisture content, ash content, and bulk density were also determined. FT-IR analysis
showed the presence of various functional groups such as C=O, C=C, –OH, and C-H on
the surface of the adsorbent. Moisture content, ash content and bulk density were found to
be 5.32 ± 0.06 %, 15.28± 0.22%, 535 ± 0.51 kg m-3
respectively. The effect of contact
time and initial concentration were studied. Fluoride equilibrium time was found to be
120 minutes. Adsorption of Fluoride fits the Langmuir isotherm. Fluoride adsorption
experiments were performed on the laboratory-scale column. The parameters obtained
from the laboratory scale column were used to build the packed bed column using a scaleup approach.10.0 g of RHAC has the capacity of attaining 83% of fluoride removal for
the initial concentration of 10 mg L-1
.
Keywords: Rice husk activated carbon, Fluoride, Langmuir isotherm, Packed bed column
