Adsorption of methyl orange and methylene blue dyes by lead sulphide modified calix[n]arenes (n=4,6,8)
Various industries around the world such as textile, printing, and leather industries have contributed to major sources of coloured wastewater that can cause severe water pollution. As a result, the current study aims to determine the adsorption behaviour of methyl orange (MO) and methylene blue...
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| Format: | Thesis |
| Language: | English |
| Published: |
2022
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/113998/1/113998.pdf |
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| Summary: | Various industries around the world such as textile, printing, and leather industries have
contributed to major sources of coloured wastewater that can cause severe water
pollution. As a result, the current study aims to determine the adsorption behaviour of
methyl orange (MO) and methylene blue (MB) dyes based on calix[n]arene-modified
lead sulphide (PbS) (n=4, 6, 8) nanoadsorbents under optimal conditions. The
calix[n]arene-modified PbS was formed by mixing 3-glycidoxypropyltrimethoxy silane,
p-tert-butylcalix[n]arene, and PbS in dry toluene with triethylamine as a catalyst.
Characterization studies using fourier transform infrared spectroscopy (FTIR), field
emission scanning electron microscopy (FESEM), and energy dispersive X-ray
spectroscopy (EDX) revealed a successful synthesis of calix[n]arene-modified PbS.
FTIR and EDX showed the presence of O–H stretching vibration, stretching vibration of
C-CH3, C=C aromatic vibration, C-O stretching, carbon (C) and silicon (Si) which are
evidence of successful immobilization of p-tert-butyl-calix[n]arene on the PbS surface.
Morphological change from nanoparticles to flake-like structures is another indication
the presence of p-tert-butyl calix[n]arene. According to the findings, the pH of point of
zero charge (pHPZC) of the calix[4]arene-modified PbS, calix[6]arene-modified PbS, and
calix[8]arene-modified PbS were pH 6.80, pH 7.28, and pH 7.31, respectively. Response
surface methodology (RSM) was executed to develop a response surface for the
optimization of adsorption conditions. The evaluation was further conducted to
investigate the interactive effect of various factors (initial concentration, adsorbent
dosage, contact time, pH, and temperature) on the adsorption of dye using a central
composite design (CCD). The percentage removal of dyes from the water system was
used to assess adsorption performance. The results of batch adsorption tests are presented
in the study, which include the adsorption capacities, kinetics, and isotherms of the MO
and MB adsorption processes. The isotherm parameters were determined using the
Langmuir and Freundlich equilibrium models. The isotherm study of MO adsorption by
calix[4]arene-modified PbS were best fitted by the Freundlich, indicating adsorption on
heterogenous surfaces. In contrast, the isotherm studies of MB adsorption by
calix[4]arene-modified PbS, calix[6]arene-modified PbS, and calix[8]arene-modified
PbS were best described by the Langmuir, suggesting monolayer adsorption onto
homogenously distributed adsorption sites of the adsorbent surfaces. The fitted model
with the maximum adsorption capacity (qmax) of 3.268 mg/g, was discovered for the
adsorption of MO by calix[4]arene-modified PbS. Meanwhile, the qmax for MB
adsorption by calix[4]arene-modified PbS, calix[6]arene-modified PbS, and
calix[8]arene-modified PbS were found to be 5.850 mg/g, 5.495 mg/g, and 11.90 mg/g,
respectively. Pseudo-first order and pseudo-second order of kinetic studies were
demonstrated for their quality to fit the data. The adsorption kinetics of MO adsorption
by calix[4]arene-modified PbS, MB adsorption by calix[4]arene-modified PbS,
calix[6]arene-modified PbS, and calix[8]arene-modified PbS were well described by the
pseudo-second order model suggesting that the adsorption on the adsorbent’s surfaces
occurred via chemical adsorption. The reusability and leaching tests were performed to
reduce the adsorbent disposal issues. The results showed that the adsorbents synthesized
were stable, and there was a low risk of contaminant (Pb) released into bodies of water.
Adsorption mechanisms such as electrostatic interaction, hydrogen bonding interaction,
Yoshida hydrogen bonding interaction, and π-π interactions were proposed for dye
adsorption on calix[n]arenes-modified PbS. Overall, the research presented novel
adsorbents, calix[n]arenes-modified PbS, and a reusability strategy that could be used as
alternative adsorbents in MO and MB dye removal and environmentally sustainable dye
wastewater treatment. |
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