I have noticed several papers where the methylene blue number of derived samples of activated carbon where performed under characterization studies. However I did notice a certain level of discrepancies among the actual techniques from paper to paper. Is there a standard procedure for the determination of the methylene blue number? If so is it possible to get any sort of material that would be helpful?
Thanking you in advance :)
Methylene number of active carbon
The aim of the laboratory practice is evaluation of coloring agents removal from waste water efficiency.
INTRODUCTION
Methylene number is a parameter of active carbon (AC) which gives opportunity to indicate de-coloring properties of AC (sorption properties in solutions).
“Methylene blue (CI 52015) is a heterocyclic aromatic chemical compound with the molecular formula C16H18N3SCl. It has many uses in a range of different fields, such as biology and chemistry. At room temperature it appears as a solid, odorless, dark green powder, that yields a blue solution when dissolved in water. The hydrated form has 3 molecules of water per molecule of methylene blue.” [1]
Caution:
“Methylene blue should not be confused with methyl blue, another histology stain, new methylene blue, nor with the methyl violets often used as pH indicators.” [1]
Molar mass 319.85 g/mol (pure substance)
Molar mass 373,9 g/mol (hydrated by 3 molecules of water – typical commercial form)
APPARATUSES AND APPLIANCES
Spectrophotometer, cuvettes (absorption cells), laboratory shaker
GLASS AND CHEMICALS
Methylene Blue, active carbon, laboratory bulbs, laboratory flasks with stoppers, measuring pipettes
Measuring schedule
1. Prepare base solution of the methylene dye by dissolving of 25 mg of the Methylene Blue in 500 cm3 of distilled water.
2. Prepare the set of standard dye solutions:
a. to 7 measuring flask of 10 cm3 volume batch 0.05; 0.1; 0.2; 0.4; 0.5; 0.8; 1.0 cm3 of base solution and fill the flask to the mark using distilled water
b. calculate concetration of obtained solutions in mg/dm3
c. measure the absorbance A of standard solutions using wavelength l=660 nm in the cuvette of thickness of absorbing layer 1 cm
3. Measure of cleaning effectiveness of dye solution by the active carbon
a. to the flask with with stopper of 100 ml volume sample 0.1 g of active carbon with accuracy of 4 fractional numbers (after the dot). Do two repeats (together 3 samples) for the same carbon
b. Add the 50 cm3 of base dye solution. Shake the vessel on the laboratory shaker by the 60 minutes.
c. After shaking separate the solution using paper filter
d. Measure the absorbance A of the solution using wavelength l=660 nm in the cuvette of thickness of absorbing layer 1 cm
Data procesing
1. Data on the absorbance of the standard dye solutions express on the chart absorbance versus concentration of the dye. Draw the line of tendency. In such a way the calibration curve appears.
2. Using the calibration curve find the concentration of the solution obtained after adsorption on active carbon.
3. Calculate the adsorption in g of dye per g of AC [g/g], this value is called methylene number.
Reference
[1] http://en.wikipedia.org/wiki/Methylene_blue (2012-11-03)
the refrence of this method is:
home.agh.edu.pl/~jodlowsk/en/cc/labs/methylene_number.doc
you may also see this paper:
http://www.sciencedirect.com/science/article/pii/S0304389408014702
all the best
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