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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption, other
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No gudeline study used
Qualifier:
no guideline followed
Principles of method if other than guideline:
Activated river sand has been used as adsorbent for removal of oxalic acid from aqueous solution. Validity of Freundlich and Langmuirs adsorption
isotherm has been tested and it was found that adsorption isotherm of oxalic acid on sand follows these adsorption models.
GLP compliance:
no
Media:
other: Activated river sand
Specific details on test material used for the study:
- Name of test material (as cited in study report): oxalic acid
- Substance type: organic acid
- Physical state: solid
- Other: oxalid acid solution of 0.5 N was prepared by dissolving 1.575 g of solid in distilled water and finally diluted to 250 cm3 with distilled water.
Radiolabelling:
no
Test temperature:
25ºC
Details on matrix:
COLLECTION AND STORAGE
- Geographic location: Vainganga Rier bed in Gadchiroli (Maharashtra, India)
- Storage conditions: washed with distilled water and then with double distilled water
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): activated at 120°C for 24 hours before use

PROPERTIES
- mesh size of sand: 60-120
Details on test conditions:
TEST CONDITIONS
- temperature: 25°C

TEST SYSTEM
- Type, size and further details on reaction vessel: flasks
- Water filtered (i.e. yes/no; type of size of filter used, if any): distilled water used for preparation of oxalic acid solutions
- Amount of soil/sediment/sludge and water per treatment: 1 gram of activated sand was added to each flask

flask no oxalic acid/cm3 water/cm3
1 50 0
2 40 10
3 30 20
4 20 10
5 10 40

- Number of reaction vessels/concentration: 5
-Test performed in closed vessels due to significant volatility of test substance: corked flasks
- Method of preparation of test solution: oxalid acid solution of 0.5 N was prepared by dissolving 1.575 g of solid in distilled water and finally diluted to 250 cm3 with distilled water.
Sample no.:
#1
Duration:
30 min
Conc. of adsorbed test mat.:
312 other: g/L
Temp.:
25 °C
Sample no.:
#2
Duration:
30 min
Conc. of adsorbed test mat.:
215 other: g/L
Temp.:
25 °C
Sample no.:
#3
Duration:
30 min
Conc. of adsorbed test mat.:
128 other: g/L
Temp.:
25 °C
Sample no.:
#4
Duration:
30 min
Conc. of adsorbed test mat.:
54.2 other: g/L
Temp.:
25 °C
Sample no.:
#5
Duration:
30 min
Conc. of adsorbed test mat.:
13.5 other: g/L
Temp.:
25 °C
Computational methods:
- Slope of Freundlich adsorption isotherm: 0.44
- intercept of Freundlich equation: 6.31 (log value is 0.8)

- Slope of Langmuir adsorption isotherm: 0.03
- intercept of Langmuir equation: 0.5
Sample No.:
#1
Type:
other: Amount absorbed
Value:
ca. 60 other: g/L
Temp.:
25 °C
Sample No.:
#2
Type:
other: amount absorbed
Value:
ca. 58 other: g/L
Temp.:
25 °C
Sample No.:
#3
Type:
other: amount absorbed
Value:
ca. 47.6 other: g/L
Temp.:
25 °C
Sample No.:
#4
Type:
other: amount absorbed
Value:
ca. 28.3 other: g/L
Temp.:
25 °C
Sample No.:
#5
Type:
other: amount absorbed
Value:
ca. 3.2 other: g/L
Temp.:
25 °C
Validity criteria fulfilled:
yes
Conclusions:
Activated river sand has been used as adsorbent for removal of oxalic acid from aqueous solution. Validity of Freundlich and Langmuirs adsorption
isotherm has been tested and it was found that adsorption isotherm of oxalic acid on sand follows these adsorption models. The slope of the Freundlich adsorption isotherm was 0.44, the intercept of the Freundlich equation was 6.31 (log value is 0.8).The slope of Langmuir adsorption isotherm was 0.03, the intercept of the Langmuir equation was 0.5.
Executive summary:

Activated river sand has been used as adsorbent for removal of oxalic acid from aquous solution. Validity of Freundlich and Langmuirs adsorption isotherm has been tested and it was found that adsorption isotherm of oxalic acid on sand follows these adsorption models. It was observed that the separation efficiency with sand as an adsorbent was excellent as compaired to silica gel.

Description of key information

Key value for chemical safety assessment

Koc at 20 °C:
6.31

Additional information

[LogKoc: 0.8]