Sorption of phosphate from acidic wastewater into three tunisian clay soils
The removal of phosphates from acidic wastewater using three soil minerals (Soil1, Soil2, and Soil3) with high content of paligoskite, smectite and illite, respectively, is studied. The effect of the medium pH value, contact duration and solid:liquid ratio is considered. The smectite-containing soil...
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| Опубліковано в: : | Химия и технология воды |
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| Дата: | 2008 |
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Інститут колоїдної хімії та хімії води ім. А.В. Думанського НАН України
2008
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| Цитувати: | Sorption of phosphate from acidic wastewater into three tunisian clay soils / N. Hamdi, E. Srasra // Химия и технология воды. — 2008. — Т. 30, № 4. — С. 374-384. — Бібліогр.: 19 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859864316379922432 |
|---|---|
| author | Hamdi, N. Srasra, E. |
| author_facet | Hamdi, N. Srasra, E. |
| citation_txt | Sorption of phosphate from acidic wastewater into three tunisian clay soils / N. Hamdi, E. Srasra // Химия и технология воды. — 2008. — Т. 30, № 4. — С. 374-384. — Бібліогр.: 19 назв. — англ. |
| collection | DSpace DC |
| container_title | Химия и технология воды |
| description | The removal of phosphates from acidic wastewater using three soil minerals (Soil1, Soil2, and Soil3) with high content of paligoskite, smectite and illite, respectively, is studied. The effect of the medium pH value, contact duration and solid:liquid ratio is considered. The smectite-containing soil possesses the highest sorption capacity with respect to phosphate. The isotherms of phosphate sorption by soils are processed in the Freundlich and Langmuir equation coordinates. It is shown that the fitting of isotherms in the Freundlich equation coordinates results in better correspondence with experimental data. In addition, the adsorption selectivity of ions (PO₄³⁻, F⁻, Cl⁻) existing in waste solution by these soils was studied, and the fluoride is more selective at acidic pH region.
Вивчено видалення фосфатів з кислих стічних вод трьома видами ґрунтових мінералів (ґрунт 1, ґрунт 2 і ґрунт 3) з високим вмістом палигорскита, смектита і ілліта відповідно. Розглянуто вплив pН середовища, тривалості контакту і відношення кількості твердої речовини до рідини. Ґрунт, що містить смектит має найбільшу сорбційну ємність выдносно фосфату. Ізотерми сорбції фосфату оброблені по рівняннях Фрейндліха і Лэнгмюра. Показано, що представлення ізотерми в координатах Фрейн-дліха краще погоджується з експериментальними даними. Крім того, вивчена селективність адсорбції іонів (PO₄³⁻, F⁻, Cl⁻), що присутні у стічних водах, цими ґрунтами. З’ясовано, що селективність ґрунтів найбільш висока відносно фториду в кислому середовищі
Изучено удаление фосфатов из кислых сточных вод тремя видами почвенных минералов (почва 1, почва 2 и почва 3) с высоким содержанием соответственно палыгорскита, смектита и иллита . Рассмотрено влияние pH среды, длительности контакта и отношения количества твердого вещества к жидкости. Почва, содержащая смектит, обладает наибольшей сорбционной емкостью по отношению к фосфату. Изотермы сорбции фосфата обработаны по уравнениям Фрейндлиха и Лэнгмюра. Показано, что представление изотерм в координатах Фрейндлиха лучше согласуется с экспериментальными данными. Кроме того, изучена селективность адсорбции ионов (PO₄³⁻, F⁻, Cl⁻), присутствующих в сточных водах, этими почвами. Выяснено, что селективность почв наиболее высока по отношению к фториду в кислой среде.
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| first_indexed | 2025-12-07T15:47:32Z |
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| fulltext |
374 ISSN 0204–3556. Химия и технология воды, 2008, т. 30, №4
N. HAMDI, E. SRASRA, 2008
N. Hamdi, E. Srasra
SORPTION OF PHOSPHATE FROM ACIDIC
WASTEWATER INTO THREE TUNISIAN CLAY SOILS
The removal of phosphates from acidic wastewater using three soil minerals (Soil1,
Soil2, and Soil3) with high content of paligoskite, smectite and illite, respectively, is
studied. The effect of the medium pH value, contact duration and solid:liquid ratio
is considered. The smectite-containing soil possesses the highest sorption capacity
with respect to phosphate. The isotherms of phosphate sorption by soils are processed
in the Freundlich and Langmuir equation coordinates. It is shown that the fitting of
isotherms in the Freundlich equation coordinates results in better correspondence
with experimental data. In addition, the adsorption selectivity of ions (PO4
3-, F-, Cl-)
existing in waste solution by these soils was studied, and the fluoride is more selective
at acidic pH region.
1. Introduction
Phosphate is usually considered as the main factor causing environmental
deterioration of water nature. The ability to predict leaching rates of phosphate
through soils to groundwater and surface water is therefore essential for the
long-term management of a site for land disposal of waste. However,
phosphorus removal from wastewater has been widely studied during the past
decades by some authors [1 – 4]. Several parameters and typical removal
methods such as chemical and biological treatments have been successfully
applied [1]. In this context, we can note that the pH and the soil contents of
iron, aluminium, calcite and organic matter are factors affecting immobilization
of soluble P applied to soil through adsorption and/or precipitation reactions
[5, 6]. Furthermore the clay and clay soil was selected among the best natural
adsorbent of phosphate [7 – 10]. In addition the presence of calcite in the soil
increase the phosphate removal by physical adsorption and precipitation at pH
greater than 6 [11,12].
This paper reports phosphate retention/adsorption throughout the profiles
of three Tunisian clay soils intended for the storage of an industrial waste. This
waste is an acidic aqueous solution of pH 3, where the phosphate concentration
is about 1500 mg P/L. An attempt is also made to relate adsorption to physical
and chemical characteristics of these soils. Besides, the capacity of phosphate
sorption by these clay soils was found to depend on pH solution, solid–liquid
ratios and available phosphate concentration with equilibrium being achieved
within 1 – 2 days. In addition, the adsorption characteristics of these materials
for phosphate removal from aqueous solutions were evaluated in batch
experiments and the isotherms were fitted by Langmuir and Freundlich models.
ISSN 0204–3556. Химия и технология воды, 2008, т. 30, №4 375
2. Materials and Methods
The natural samples used in the present experiments were obtained from
three locations designed for acidic waste disposal in the South-East of Tunisia.
However, the purification was made by the classical method of NaCl exchange
[13]. Its physico-chemical compositions (determined by chemical analysis and
XRD), the cationic exchange capacity (CEC) and specific surface areas (SBET)
are presented in Table 1. The initial phosphate content in all samples not exceeds
the 0.1% of the hydrated sample. For all samples, the powders was sieved to
particle sizes lower than 106 мm and were dried at 90°C for a minimum of
24 hours before sorption studies.
Table 1. Mineralogical composition, CEC and SBET of samples according to
Hamdi et al. [14]
Mineralogical composition of clay samples (%) Sample
Paly Smec Kao Il Q Ca Do
SBET
(m2/g)
CEC
(meq/100g)
Soil1 35.5 1.7 14.9 – 28 18.9 – 35.4 16.5
Soil2 – 56.3 6.5 – 12.9 25.6 – 57.1 49.8
Soil3 – – 22.9 62.7 8.8 – 4.7 91.5 24.7
Paly: palygorskite, Smec: Smectite, Kao:Kaolinite, Il: Illite, Q: Quartz, Ca: Calcite, Do:
Dolomite
2.1. Instruments for phosphate and pH measurements. The pH
measurements were made using an HI 9321 Microprocessor pH meter (HANNA
Instruments) combination electrode. Phosphate concentration was measured
by the standard method (vanadomolybdophosphoric acid colorimetric method)
[15] using the spectrophotometer Hach DR/4000. Adsorbed phosphate was
calculated from the difference between the initial phosphate concentration and
the concentration of phosphate that remained in the supernatant solution.
2.2. Experimental procedure for sorption studies. Adsorption capacities
for the different samples were determined at different pH values range (3 to 9) by
shaking 1g of sieved and dried sample with 25 ml of 500 mgP/L of KH2PO4 solution
in polyethylene bottles at 25±2°C. Small amounts (5.10-1 or 5.10-2 M) of HNO3 or
NaOH were also added initially to provide the solutions with final pH values, then
the solute was made up to a volume of 30 mL with deionised water. The bottles
were agitated in a rotary agitator for periods ranging from 1 hour to 2 days before
being centrifuged at 3000 rpm for 10 min. After centrifugation, total phosphorous
concentrations in the recovered solution were measured.
Phosphate sorption isotherms were determined by a procedure similar to
that described above. One gram of sample and 25 mL of KH2PO4 solution at
various concentrations (50 to 2000 mgP/L) were pH has adjusted to 3±0.2 and
the solute was made up to a volume of 30 mL with deionised water, also were
mixed in polyethylene bottles at 25±2°C.
376 ISSN 0204–3556. Химия и технология воды, 2008, т. 30, №4
3. Results and discussion
3.1. Equilibrium time. Phosphate is adsorbed rapidly at the soil surface and
equilibrium is reached within 24 h according Ye et al [7] and Gerritse [12]. This
physically adsorbed phosphate on the soil sample surface is termed mobile as it is
readily exchangeable. After the initial adsorption to the surface, phosphate continues
to react with the soil sample. In this study, the results of phosphate adsorption
kinetic experiments at 25±2°C show that the equilibrium is reached within 20 h
using a synthetic solution and 48h, using the wastewater. This delay of adsorption
in the case of waste solution is caused by the effect of the other ions on the sorption
kinetic phenomena. Moreover, this contact time was considered as the equilibrium
time for the following adsorption study.
3.2. Effect of pH on phosphate adsorption. With a similar procedure, the
effect of pH on phosphate adsorption was examined in a series of experiments that
used the same initial phosphate concentration (500 mgP/L) while maintaining pH
at different values between 3 and 9. The effect of pH on phosphate adsorption for
these soils is illustrated in Figure1 for purified samples and Figure 2 for raw samples.
Adsorption of phosphate by purified clay as a function of pH clearly differs from
the pH response for the raw sample. Besides, for the pure Soil3 sample the general
shape of the pH curves with a peak in adsorption for illite and kaolinite at pH 4 –
6 accords well with the results obtained by other investigators [16,17]. In the case
of pure Soil1 the adsorption decreases with pH increasing, whereas in the case of
pure Soil2 sample is the contrary. This increased phosphate adsorption can be
explained by the fact that smectite contains a large amount of exchangeable calcium
that can react with phosphorus to form an insoluble calcium phosphate phase [17,
18]. Furthermore, the results of raw samples show that the phosphate removal
increase with increasing pH and the Soil2 have the higher adsorption capacity.
This greatest removal efficiency of phosphate occurred at alkaline conditions due
to the higher calcium content and/or to the calcite or dolomite fraction.
Figure 1. Effect of pH on phosphate removal using purified samples
ISSN 0204–3556. Химия и технология воды, 2008, т. 30, №4 377
Figure 2. Effect of pH on phosphate removal using natural samples
3.3. Phosphate sorption isotherms. Based on the results of the kinetic
studies and in order to work in the same condition of wastewater, all equilibrium
experiments were carried out at pH 3±0.2 and for a reaction period of 24 h
using KH2PO4 solution at various concentrations (50 to 2000 mg P/L). The
results of these equilibrium adsorption experiments are presented in Figure 3.
Figure 3. Linearized Langmuir adsorption isotherm of the three samples
378 ISSN 0204–3556. Химия и технология воды, 2008, т. 30, №4
The experimental sorption data for the adsorption of phosphorous were
correlated with Langmuir (Eq. 1) and Freundlich (Eq. 2) models:
e
e
e bC
bCQq
1
0 , (1)
n
eFe CKq
1
. (2)
Where qe is the amount of ions adsorbed per unit weight of adsorbents (mg/g),
Ce is the equilibrium concentration (mg/L), Qo and b are the Langmuir constants
related to capacity and energy of adsorption, respectively. KF and 1/n are the
Freundlich constants. The phosphate adsorption capacity increased with the
phosphate equilibrium concentration increasing. However, the theoretical
linearized of Langmuir and Freundlich isotherms are plotted in Figures 3 and
4 together with the experimental data points.
qe
Figure 4. Linearized Freundlich adsorption isotherm of the three samples
The estimated model parameters with the correlation coefficient (R2) are shown
in Table 2. The fitting curves from the two isotherms are also illustrated in
Figure 5. It is shown that the experimental data of phosphate adsorption on
these samples could be well fitted by the isotherms. We can notes that the
ISSN 0204–3556. Химия и технология воды, 2008, т. 30, №4 379
samples differ in their capacity to adsorb phosphate and Soil2 adsorbing more
than Soil1 which adsorbed more phosphate than Soil3. Clearly, the Freundlich
equation provided better fitting in terms of r2 range between (0.997 – 0.999).
The results of Langmuir isotherm shows that the soil2 had higher adsorption
capacity of order of 31.84mg/g, this result is slightly higher comparing to
literature [7, 17]. This is explained essentially by the highest concentration
used in this study and by chemical bonding of the anions to positively charged
surfaces at pH 3 on the clays.
Table 2. Summary of optimised isotherm parameters
Isotherm type
Langmuir Freundlich
Samples
Q0 (mg/g) b (l/mg) r2 KF 1/n r2
Soil1 23.31 6.92 10-4 0.831 0.030 0.84 0.999
Soil2 31.84 6.18 10-4 0.953 0.029 0.88 0.997
Soil3 19.53 7.82 10-4 0.894 0.029 0.82 0.998
Figure 5. Experimental sorption of phosphate by three samples with fitted
Langmuir, and Freundlich isotherms at pH=3±0.2
3.4. Effect of solid-liquid ratios. Some interested studies [13] have shown
that both organic and inorganic contaminant sorption is dependent on the solid–
380 ISSN 0204–3556. Химия и технология воды, 2008, т. 30, №4
liquid ratio to some degree. However, the S/L ratio presents a significant influence
on the sorption behaviour and its increase supports the increasing of adsorption
capacity. In this context, we studied here the batch tests of solid–liquid ratios of
the magnitude smaller than 3.33%, 6.66% to greater than10% using the lixiviate
solution of pH of 3 and phosphate concentration of 1500 mg/L. The determination
of separate sorption equilibrium time was performed for these samples. For all
sample the equilibrium time necessary for the 6.66% and 10% solid–liquid ratio
was needed 2 days minimum. This increase in time was probably caused by
particle aggregation and the poorer quality of mixing within the small vials.
Also, we noticed that for all samples the adsorption increase with increasing S/
L ratios (Figure 6, 7 and 8). This increased phosphate removal can be explained
by the augmentation of the pH and by the large amount of calcite that can react
with phosphorus and form an insoluble calcium phosphate phase.
Figure 6. Effect of the solid-liquid ratios on the phosphate removal by Soil2
Figure 7. Effect of the solid-liquid ratios on the phosphate removal by Soil1
ISSN 0204–3556. Химия и технология воды, 2008, т. 30, №4 381
Figure 8. Effect of the solid–liquid ratios on the phosphate removal by Soil3
3.5. Effect of other Anions on phosphate removal. Some investigators
have proposed an ion-exchange reaction as a possible mechanism for phosphate
adsorption on clay soil. To test this theory, the adsorption of phosphate by
Tunisian soils in the presence of wastewater concentrations of F- and C1- and
at pH=3 was investigated. Table 3 shows that the selectivity of the fluoride
adsorption onto three samples was 25 – 50 times greater than phosphate
adsorption. The amount of phosphate adsorbed on all sample in waste solutions
was less than that in single solutions Figure 9. However, in this waste solution
at pH 3 these soils selectively adsorbed fluoride more than phosphate.
Table 3. Selectivity adsorption study of anions (PO4
3-, F- and Cl-) from
wastewater on three samples
Removal capacity (mg/g) at
pH=3±0.2 and S/L ratio=3.33% Anions Anions Initial concentration
in wastewater (mg/L)
Soil2 Soil1 Soil3
F- 2360 57.04 60.01 51.92
PO4
3- 1500 2.43 1.52 1.12
Cl- 880 2.17 1.45 0.05
382 ISSN 0204–3556. Химия и технология воды, 2008, т. 30, №4
Figure 9. Amount of phosphate removal by three samples from single and
waste solution. pH = 3, S/L ratio=3.33% and 1500 mg P/L
4. Conclusions. Three Tunisian natural soils were tested to remove
phosphate ions from KH2PO4 solution and acidic wastewater. However, kinetics,
pH effect, the solid-liquid ratios, and effect of others anions as (F- and Cl-)
were examined. The results show that for all samples the phosphate removal
increase with increasing pH and the Soil2 have the higher adsorption capacity.
This greatest removal efficiency of phosphate occurred at alkaline conditions
due to the higher calcium content and/or to the calcite or dolomite fraction.
The results of the experimental data of phosphate adsorption on these samples
could be well fitted by Freundlich isotherm. Furthermore, the solid-liquid ratios
play an interested role for phosphate uptake, the maximum of removal capacity
was found for S/L ratios of 10%. The amount of phosphate adsorbed on these
soils from single and waste solution show that the adsorption is very important
in the first case. In addition, the effect of other anions on phosphate adsorption
may be due to waste composition, pH and their affinity towards these soils.
Moreover, the fluoride is more selective in this waste condition.
Резюме. Вивчено видалення фосфатів з кислих стічних вод трьома
видами ґрунтових мінералів (ґрунт 1, ґрунт 2 і ґрунт 3) з високим вмістом
палигорскита, смектита і ілліта відповідно. Розглянуто вплив pН середо-
вища, тривалості контакту і відношення кількості твердої речовини до
рідини. Ґрунт, що містить смектит має найбільшу сорбційну ємність выд-
носно фосфату. Ізотерми сорбції фосфату оброблені по рівняннях Фрей-
ндліха і Лэнгмюра. Показано, що представлення ізотерми в координатах
Фрейн-дліха краще погоджується з експериментальними даними. Крім
того, вивчена селективність адсорбції іонів (PO4
3-, F-, Cl), що присутні у
стічних водах, цими ґрунтами. З’ясовано, що селективність ґрунтів
найбільш висока відносно фториду в кислому середовищі
ISSN 0204–3556. Химия и технология воды, 2008, т. 30, №4 383
Н. Хамди, Е. Срасра
СОРБЦИЯ ФОСФАТА ИЗ КИСЛЫХ СТОЧНЫХ ВОД ТРЕМЯ
ВИДАМИ ТУНИССКИХ ГЛИНИСТЫХ ПОЧВ
Реферат
Изучено удаление фосфатов из кислых сточных вод тремя видами
почвенных минералов (почва 1, почва 2 и почва 3) с высоким содержани-
ем соответственно палыгорскита, смектита и иллита . Рассмотрено вли-
яние pH среды, длительности контакта и отношения количества твердо-
го вещества к жидкости. Почва, содержащая смектит, обладает
наибольшей сорбционной емкостью по отношению к фосфату. Изотер-
мы сорбции фосфата обработаны по уравнениям Фрейндлиха и Лэнгмю-
ра. Показано, что представление изотерм в координатах Фрейндлиха луч-
ше согласуется с экспериментальными данными. Кроме того, изучена
селективность адсорбции ионов (PO4
3-, F-, Cl), присутствующих в сточ-
ных водах, этими почвами. Выяснено, что селективность почв наиболее
высока по отношению к фториду в кислой среде.
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| id | nasplib_isofts_kiev_ua-123456789-130574 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 0204-3556 |
| language | English |
| last_indexed | 2025-12-07T15:47:32Z |
| publishDate | 2008 |
| publisher | Інститут колоїдної хімії та хімії води ім. А.В. Думанського НАН України |
| record_format | dspace |
| spelling | Hamdi, N. Srasra, E. 2018-02-16T19:26:54Z 2018-02-16T19:26:54Z 2008 Sorption of phosphate from acidic wastewater into three tunisian clay soils / N. Hamdi, E. Srasra // Химия и технология воды. — 2008. — Т. 30, № 4. — С. 374-384. — Бібліогр.: 19 назв. — англ. 0204-3556 https://nasplib.isofts.kiev.ua/handle/123456789/130574 The removal of phosphates from acidic wastewater using three soil minerals (Soil1, Soil2, and Soil3) with high content of paligoskite, smectite and illite, respectively, is studied. The effect of the medium pH value, contact duration and solid:liquid ratio is considered. The smectite-containing soil possesses the highest sorption capacity with respect to phosphate. The isotherms of phosphate sorption by soils are processed in the Freundlich and Langmuir equation coordinates. It is shown that the fitting of isotherms in the Freundlich equation coordinates results in better correspondence with experimental data. In addition, the adsorption selectivity of ions (PO₄³⁻, F⁻, Cl⁻) existing in waste solution by these soils was studied, and the fluoride is more selective at acidic pH region. Вивчено видалення фосфатів з кислих стічних вод трьома видами ґрунтових мінералів (ґрунт 1, ґрунт 2 і ґрунт 3) з високим вмістом палигорскита, смектита і ілліта відповідно. Розглянуто вплив pН середовища, тривалості контакту і відношення кількості твердої речовини до рідини. Ґрунт, що містить смектит має найбільшу сорбційну ємність выдносно фосфату. Ізотерми сорбції фосфату оброблені по рівняннях Фрейндліха і Лэнгмюра. Показано, що представлення ізотерми в координатах Фрейн-дліха краще погоджується з експериментальними даними. Крім того, вивчена селективність адсорбції іонів (PO₄³⁻, F⁻, Cl⁻), що присутні у стічних водах, цими ґрунтами. З’ясовано, що селективність ґрунтів найбільш висока відносно фториду в кислому середовищі Изучено удаление фосфатов из кислых сточных вод тремя видами почвенных минералов (почва 1, почва 2 и почва 3) с высоким содержанием соответственно палыгорскита, смектита и иллита . Рассмотрено влияние pH среды, длительности контакта и отношения количества твердого вещества к жидкости. Почва, содержащая смектит, обладает наибольшей сорбционной емкостью по отношению к фосфату. Изотермы сорбции фосфата обработаны по уравнениям Фрейндлиха и Лэнгмюра. Показано, что представление изотерм в координатах Фрейндлиха лучше согласуется с экспериментальными данными. Кроме того, изучена селективность адсорбции ионов (PO₄³⁻, F⁻, Cl⁻), присутствующих в сточных водах, этими почвами. Выяснено, что селективность почв наиболее высока по отношению к фториду в кислой среде. en Інститут колоїдної хімії та хімії води ім. А.В. Думанського НАН України Химия и технология воды Физическая химия процессов обработки воды Sorption of phosphate from acidic wastewater into three tunisian clay soils Сорбция фосфата из кислых сточных вод тремя видами тунисских глинистых почв Article published earlier |
| spellingShingle | Sorption of phosphate from acidic wastewater into three tunisian clay soils Hamdi, N. Srasra, E. Физическая химия процессов обработки воды |
| title | Sorption of phosphate from acidic wastewater into three tunisian clay soils |
| title_alt | Сорбция фосфата из кислых сточных вод тремя видами тунисских глинистых почв |
| title_full | Sorption of phosphate from acidic wastewater into three tunisian clay soils |
| title_fullStr | Sorption of phosphate from acidic wastewater into three tunisian clay soils |
| title_full_unstemmed | Sorption of phosphate from acidic wastewater into three tunisian clay soils |
| title_short | Sorption of phosphate from acidic wastewater into three tunisian clay soils |
| title_sort | sorption of phosphate from acidic wastewater into three tunisian clay soils |
| topic | Физическая химия процессов обработки воды |
| topic_facet | Физическая химия процессов обработки воды |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/130574 |
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