Carbon and Polymer based Novel Adsorbents for the Removal of Fluoride from Aqueous Solution

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.

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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.

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IITH Creators:
IITH CreatorsORCiD
Sharma, Chandra ShekharUNSPECIFIED
Item Type: Thesis (PhD)
Subjects: Chemical Engineering
Divisions: Department of Chemical Engineering
Depositing User: Team Library
Date Deposited: 20 Dec 2018 10:08
Last Modified: 20 Dec 2018 10:08
URI: http://raiith.iith.ac.in/id/eprint/4630
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