Global NEST Journal

ISSN:

Print ISSN: 1790-7632

Electronic ISSN: 2241-777X

Volume 12 - 2010

Articles

Study of the Cu(II) removal from aqueous solutions by adsorption on titania

Georgaka A. and Spanos N., Pages:239-247

DOI:

https://doi.org/10.30955/gnj.000717

Paper Topic:

General

Issue:

Issue 3

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Abstract

The removal of heavy metals from wastewaters is a matter of paramount importance due to the
fact that their high toxicity causes major environmental pollution problems. One of the most
efficient, applicable and low cost methods for the removal of toxic metals from aqueous
solutions is that of their adsorption on an inorganic adsorbent. In order to achieve high
efficiency, it is important to understand the influence of the solution parameters on the extent of
the adsorption, as well as the kinetics of the adsorption. In the present work, the adsorption of
Cu(II) species onto TiO2 surface was studied. It was found that the adsorption is a rapid process
and it is not affected by the value of ionic strength. In addition, it was found that by increasing
the pH, the adsorbed amount of Cu2+ ions and the value of the adsorption constant increase,
whereas the value of the lateral interaction energy decreases.

Poly(sodium acrylate) hydrogels as potential pH-sensitive sorbents for the removal of model organic and inorganic pollutants from water

Bekiari V. and Lianos P., Pages:262-269

DOI:

https://doi.org/10.30955/gnj.000720

Paper Topic:

General

Issue:

Issue 3

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Abstract

Anionic poly(sodium acrylate), PANa, hydrogels bearing negatively charged –COO- groups were
used as sorbents for the removal of colored organic or inorganic model pollutants, namely Crystal
Violet and Cu2+, from water. It was found that PANa hydrogels adsorb stronger Cu2+ions than Crystal
Violet, as a consequence of the formation of coordination complexes between the hydrogel and the
metal ions, while just electrostatic interactions are the major driving forces for Crystal Violet.
Furthermore, the influence of pH, i.e. the neutralization degree i of the hydrogel, on its adsorption
efficiency was investigated. It is shown that the adsorption of Cu2+ ions follows stoichiometry, namely
one metal ion per two carboxylate anions. On the contrary, the adsorption of Crystal Violet is much
lower than the charged stoichiometry.

Study of polyacrylic acid adsorption on the interface of hydroxyapatite – electrolyte solutions

Hafez I.T., Paraskeva C.A., Klepetsanis P.G. and Koutsoukos P.G., , Pages:270-278

DOI:

https://doi.org/10.30955/gnj.000718

Paper Topic:

General

Issue:

Issue 3

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Abstract

The adsorption of polyacrylic acid (PAA) on hydroxyapatite (HAP) from HAP saturated solutions was
studied in this work as a function of PAA concentration, temperature, pH and ionic strength. In all
experiments, the adsorption was studied under conditions of negatively charged adsorbent and
adsorbate, respectively. These conditions ensured that adsorption was not electrostatically favored.
The solution composition was found to influence significantly the maximum of the adsorbed amount.
In fact, the adsorption of PAA, was found to increase with ionic strength, due to the decrease of
double layer thickness of HAP particles. The effect of temperature and ionic strength on the kinetics
of adsorption are also reported. Adsorption isotherms obtained at 30oC were found to be Langmuirtype,
while at higher temperatures they were of the Brunauer-Emmett-Teller (BET) type. The
absorbed amount of PAA was found to decrease with temperature, while it increased with ionic
strength. For pH values lower than 6.5, the adsorption increased while for pH between 6.5 and 9 the
adsorbed amount remained almost constant.

Adsorption of atrazine in packed beds

Kovaios I.D., . Paraskeva C.A, and Koutsoukos P.G, Pages:279-287

DOI:

https://doi.org/10.30955/gnj.000719

Paper Topic:

General

Issue:

Issue 3

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Abstract

The adsorption of the herbicide atrazine in packed beds filled with solids modelling soil components,
(silica and humic acid), was studied at conditions simulating the adsorption of atrazine in cultivated
soils. The choice of only two constituents of soil in the experimental study was based on the
assumption that these two compounds contribute significantly to the adsorption of herbicides in soil
relative to others, like alumina, calcium carbonate, etc. Packed beds were filled with inorganic
material (silica gel grains) and solid organic compounds (humic acid). Adsorption data were fitted to
the Freundlich isotherm. The presence of humic acid, even in small quantities, increases
considerably the amount of adsorbed atrazine. Increasing humic acid content in the packed beds,
the amount of adsorbed atrazine increased. Reversibility tests showed that the adsorption of
atrazine was reversible. Two steps for adsorption and desorption were observed. The first fast step
is attributed to the physical adsorption on the free adsorption sites of the substrates washed by the
solution, while the second slow step is attributed to the diffusion of the molecules of atrazine within
the structure of the silica and of the humic acid. Study of the hydrodynamics of atrazine containing
solutions flow in the packed beds filled with silica and humic acid showed that the morphology of
insoluble humic acid upon hydration changed its shape resulting in its transport through the bed and
clogging of the narrow pores of the medium. As a result the packed bed permeability was reduced
by 99%.

Removal of refractory organic sulfur compounds in fossil fuels using MOF sorbents

Blanco-Brieva G., Campos-Martin J.M., Al-Zahrani S.M. and Fierro J.L.G., Pages:296-304

DOI:

https://doi.org/10.30955/gnj.000721

Paper Topic:

General

Issue:

Issue 3

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Abstract

The stringent new regulations to lower sulfur content in fossil fuels require new economic and
efficient methods for desulfurization of recalcitrant organic sulfur. Hydrodesulfurization of such
compounds is very costly and requires high operating temperature and pressure. Adsorption is a
non-invasive approach that can specifically remove sulfur from refractory hydrocarbons under mild
conditions and it can be potentially used in industrial desulfurization. Intensive research has been
conducted in materials development to increase their desulfurization activity; however, even the
highest activity obtained is still insufficient to fulfil the industrial requirements. To improve the
adsorption capacity and sorbent regeneration, more work is needed in areas such as increasing
specific desulfurization activity, hydrocarbon phase tolerance, sulfur removal at higher temperature,
and development of new porous substrates for desulfurization of a broader range of sulfur
compounds. This work comprehensively describes the adsorption of organo-sulfur compounds
present in liquid fuels on metal-organic framework (MOF) compounds. It has been demonstrated that
the extent of dibenzothiophene (DBT) adsorption at temperatures close to ambient (304 K) is much
higher on MOF systems than on the benchmarked Y-type zeolite and activated carbons. In addition, the
DBT adsorption capacity depends strongly on the MOF type as illustrated by the much higher extent of
adsorption observed on the Cu-(C300) and Al-containing (A100) MOF systems than on the Fe-containing
(F300) MOF counterpart.

Polychlorinated biphenyl sorption to activated carbon and the attenuation caused by sediment

Hale S.E., Kwon S., Ghosh U. and Werner D., Pages:318-326

DOI:

https://doi.org/10.30955/gnj.000716

Paper Topic:

General

Issue:

Issue 3

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Abstract

Activated carbon (AC) is currently being used to treat polychlorinated biphenyl (PCB) contaminated
field sediment. In the presence of sediment, the sorption capacity of AC for PCBs can be reduced. In
this study, sorption attenuation of AC is investigated using previously published data from 5
sampling sites where reductions in aqueous concentrations caused by AC amendment have been
reported. AC-water partitioning coefficients (KAC_clean_water) were determined at a relevant PCB
concentration in clean water using polyoxymethylene (POM) passive samplers. Logarithmic ACwater
partitioning coefficient values ranged from 7.39 to 9.59 for trichlorinated to pentachlorinated
congeners. These AC-water partitioning coefficients were used in a numerical model to predict
expected reductions in aqueous concentrations. Results reveal an overprediction of actual
reductions by a median factor ranging from 2.5 to 5.6. To obtain an estimate of AC sorption
attenuation, an AC-water partitioning coefficient more representative of sediment conditions
(KAC_apparent) was fitted via the model based on the observed reductions in aqueous concentrations.
On average, median KAC_apparent values of individual PCB congeners were smaller than KAC_clean_water
values by 1.08 log units, or a factor of 12, with corrections ranging from 0.1 to 2.3 log units. The
main controls on the reduction in sorption of PCBs to AC are PCB physico-chemical properties and
AC amendment variables. Generally AC sorption attenuation increased with PCB hydrophobicity and
decreased with increasing AC-sediment contact time and AC dose.

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Global NEST Journal

Volume 12 - 2010

Articles

Study of the Cu(II) removal from aqueous solutions by adsorption on titania

Poly(sodium acrylate) hydrogels as potential pH-sensitive sorbents for the removal of model organic and inorganic pollutants from water

Study of polyacrylic acid adsorption on the interface of hydroxyapatite – electrolyte solutions

Adsorption of atrazine in packed beds

Removal of refractory organic sulfur compounds in fossil fuels using MOF sorbents

Polychlorinated biphenyl sorption to activated carbon and the attenuation caused by sediment

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Volume 12 - 2010

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