Araga, Ramya and Sharma, Chandra Shekhar
(2018)
Carbon and Polymer based Novel Adsorbents for the
Removal of Fluoride from Aqueous Solution.
PhD thesis, Indian institute of technology Hyderabad.
Full text not available from this repository.
(
Request a copy)
Abstract
Excess fluoride in drinking water causes several adverse effects on human health
and is therefore a great concern from past few decades. As groundwater is a primary
source, its de-fluoridation is therefore essential to make it suitable for drinking.
Although several adsorbent materials have been tested towards the removal of
fluoride in the past few decades, there still is a need to improve the performance of
the adsorbents by changing their physicochemical properties. The current
dissertation focuses on developing novel and efficient carbon and polymer based
adsorbent materials of different morphological and surface functional properties.
This includes jamun seed derived activated carbon which is explored for the first
time as an adsorbent whereas coconut shell charcoal is modified with multi-walled
carbon nanotubes (MWCNTs) to yield hierarchical carbon adsorbent material.
Further electrospun polymer nanofibers have been amine functionalized to enable
their use as an adsorbent. The aim of this thesis is to evaluate the defluoridation
efficiency of these novel carbon and polymer based adsorbents. Before synthesizing
the carbon based adsorbents, pyrolysis of two different polymer precursors were
performed in the presence of catalyst aiming towards the reduction of pyrolysis
temperature. We have added different weight ratios of nickel acetate tetrahydrate
(NiAc) and multi-walled carbon nanotubes (MWCNTs) as catalysts into two
different precursors, Polyacrylonitrile (PAN) and resorcinol-formaldehyde (RF)
separately. To examine the effect of pyrolysis temperature and catalyst
concentration, PAN and RF derived carbons were characterized by various
physiochemical characterization techniques. The results revealed that the addition of
NiAc facilitated the similar carbon yield at much lower temperature than what was
obtained without a catalyst. The addition of MWCNT enhanced the crystallinity of
carbon samples which is otherwise possible only by higher heat treatment. Once the
catalytic carbonization was studied in detail, jamun seed derived activated carbon
was prepared by KOH activation of jamun seed powder and the subsequent
pyrolysis at 1173 K. Carbon/CNT composite was prepared by synthesizing the
CNTs over coconut shell charcoal pyrolyzed at 1173 K, by utilizing the mineral
vii
content present in the precursor material as catalysts for CNT growth. Plasma
enhanced chemical vapor deposition (PECVD) technique was used for the low-
temperature synthesis of CNTs at 723 K. Thus PECVD processed charcoal samples
were ball milled and then used for the removal of fluoride from aqueous medium.
Amine functionalized cellulose nanofibers were prepared by the deacetylation of
electrospun cellulose acetate nanofibrous mat followed by ethylenediamine
treatment. In each of these three cases, fluoride adsorption studies were carried out
under batch mode to study the influence of various parameters such as agitation
time, amount of carbon dosage, initial fluoride concentration, initial pH and
temperature on adsorption process. The linear forms of various isotherm and kinetic
models were applied to the adsorption data to determine the best fit for equilibrium
expression. Further, thermodynamic parameters were also estimated to understand
the adsorption mechanism in detail. To validate the performance further, as-prepared
adsorbents were successfully used to treat the fluoride contaminated groundwater
samples collected from Nalgonda district, Telangana, India, which is one of the
worst affected area with excess fluoride. The field test results revealed that all the
three proposed adsorbent materials are suitable for practical application as they
could reduce the fluoride concentration of the real water samples to WHO limit at
the optimized adsorption conditions.
Actions (login required)
 |
View Item |
Altmetric
Altmetric