MENVSC / Department of Ecology and Resource Management / Fluoride is one of the anionic contaminants which is found in excess in groundwater because
of geochemical reaction or anthropogenic activities such as the disposal of industrial
wastewaters. Among various methods used for defluoridation of water such as precipitation,
ion-exchange processes, membrane processes, the adsorptions process is widely used. It offers
satisfactory results and seems to be a more attractive method for the removal of fluoride in
terms of cost, simplicity of design and operation.
In this work, the preparation of clay polymer nanocomposites (CPNCs) used in defluoridation
began by modifying the original natural Mukondeni clay to render the layered silicate miscible
with the chosen polymer, microcrystalline cellulose. Clay polymer nanocomposites (CPNCs)
were synthesized using the melt intercalation method. Mukondeni black clay with
microcrystalline cellulose as polymers was melt mixed at 220 °C for 10 minutes in an extruder
for exfoliation of the resulting composite. Physicochemical characteristics and mineralogical
characteristics of the CPNC was determined using XRD, XRF, BET, FTIR and SEM. Batch
adsorption experiments were conducted to determine the efficiency of CPNCs in defluoridation
of groundwater. The pH, EC, TDS and fluoride concentration of field water was determined
using the CRISON MM40 multimeter probe and the Orion versastar fluoride selective
electrode for fluoride concentration.
Elemental analysis revealed that CPNC 1:1 is mainly characterized of cellulose, Quartz and
Albatite as the major minerals with traces of Montmorillonite, Ednite and Magnesium as minor
minerals constituting CPNC 1:1. The structure of 1:4 CPNC was partially crystalline and
partially amorphous showing increased cellulose quantity (1:4 clay to cellulose) as compared
1:1 CPNC, 1:2 CPNC and 1:3 CPNC.
Maximum adsorption of fluoride was attained in 10 minutes using 0.5g of 1:4 CPNC removed
22.3% of fluoride. The initial fluoride concentration for the collected field groundwater was
5.4 mg/L, EC 436 μS/cm, and TDS 282 mg/L. The regeneration potential of CPNCs was
evaluated through 3 successive adsorption desorption cycles. Fluoride removal decreased after
the first cycle for all ratios of CPNCs, a continued decreased can be observed following the
second cycle. CPNC 1:2 decreased from 9.32 % at the 1st cycle to 2.84 % and 0.56 % on the
2nd and 3rd cycle respectively. CPNC 1:4 decreased from 8.22 % at the 1st cycle to 4.80 % and
0.72 % on the 2nd and 3rd cycle respectively. The fluoride-rich Siloam groundwater had a
slightly alkaline pH of 9.6.
iv
The low adsorptive characteristic displayed by all 4 CPNCs can be deduced from the BET
analysis that revealed low surface area, pore volume, and pore size, it is evident from the BET
analysis that less fluoride will be absorb as adsorption sites will be limited.
Based on the findings of this study, recommendations are designing of correct preparation
techniques to obtain nanocomposites with desirable properties, polymer melting points and
evaporation point of the binder should be taken into consideration. / NRF
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:univen/oai:univendspace.univen.ac.za:11602/1352 |
| Date | 18 May 2019 |
| Creators | Nengudza, Thendo Dennis |
| Contributors | Gitari, W. M., Kayembe, J. D. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | 1 online resource (viii, 70 leaves : color illustrations) |
| Rights | University of Venda |
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