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Nanoparticles of calcium oxide were prepared via hydrothermal method and sodium dodecyl sulfate was used as templating agent. The as-synthesized NP-CaO was used as precursor of aluminium doped calcium oxide nanoparticles. Both type of compounds were used to destructively adsorb 2,4,6 trinitrophenol. The apparatus, chemicals and instruments used for the experimental work are following:
Apparatus and Chemicals:
The chemicals and apparatus used during experimental work is listed as following:
Analytic balance AY220 (Shimadzu) Maximum 220g. 0.001mg accuracy
UV-VIS spectrophotometer UV-1700, Shimadzu
HPLC, LC 20T with Diode Array Detector; Shimadzu
GCMS QP-2010, Shimadzu
FTIR MIDAC M 2000
TGA SDT Q600 V8.3 Build 101
Scan speed mini (Labogene) max. speed: 13500 rpm
Beakers 250ml, 100ml, 50ml
Measuring Flasks 250ml, 100ml, 50ml
All chemicals used in experimental work were of analytical grade.
2,4,6 Trinitrophenol (Picric Acid) moistened with water ≥98% Sigma Aldrich
Calcium Chloride anhydrous, Merck
Sodium Hydroxide, Merck
Sodium Dodecyl Sulfate, Merck
Aluminium Chloride, Riedel-de Haën
Methanol, Riedel-de Haën
Preparation Method for Solutions:
Following are the methods of preparation of all solutions used during experimental work. All solutions were prepared in distilled water to avoid any contamination or impurity.
0.15M CaCl2 Solution
0.30M NaOH Solution
15mM AlCl3.6H2O Solution
Sodium Dodecyl Sulfate Solutions of different Concentrations: 0.004M, 0.006M, 0.008M, 0.01M and 0.012M
Synthesis of CaO Nanoparticles by Hydrothermal Method:
Calcium oxide nanoparticles were prepared by changing reaction parameter i.e. temperature and concentration of surfactant to study their effect on particle size and catalytic activity.
The mixture containing 0.15M of CaCl2 and 0.008M SDS (anionic surfactant) was magnetically stirred at ambient temperature. The precursor to surfactant molar ratio was 1M:0.05M. 0.30M sodium hydroxide as precipitating agent was added drop wise and the reaction solution was allowed to stir for 30 minutes. After stirring, the Teflon liner of stainless steel autoclave (hydrothermal bomb) was fraught with reaction suspension and kept in oven for 4 hours at desired temperature (250 oC, 200 oC 180 oC, 160 oC, 140 oC).
Same as above procedure was adopted to study the effect of surfactant, only molar concentration of SDS was varied near and far from its cmc (crticle micelle concentration) value (0.004M, 0.006M, 0.008M, 0.01M and 0.012M).
CaCl2 + 2NaOH Ca(OH)2 + 2NaCl
After 4hrs, the autoclave was taken out from oven and allowed to cool for 2 hours at ambient temperature. The precipitates of Ca(OH)2 were separated; washed 3 times with methanol and 2 times with deionised water to remove any reactant, ions or surfactant and neutralize their pH by using centrifugation machine at 13000rpm speed. The precipitates were dried and calcined at 600 oC in a furnace with air flow for 3 hours .
Preparation of Al Doped Calcium Oxide Nanoparticles Hydrothermal Method:
For synthesis of aluminium doped calcium oxide nanoparticles, deposition-precipitation method  was adopted. AlCl3.6H2O and as-synthesised CaO nanoparticles were used as precursors. 15mM solution of AlCl3.6H2O was prepared in 9ml of deionized water and 50 mg of NP-CaO was added in different time intervals to attain pH 12.3 for point of zero charge . Meanwhile the reaction was constantly on magnetic stirring. Teflon liner of autoclave (stainless steel) was fraught with reaction solution and kept in oven for 4 hrs at temperature same as that of NP-CaO precursor. The precipitates were washed and calcined same as ascribed above.
Table: 2 Nanoparticle of Calcium oxide prepared by changing hydrothermal temperature and keeping other parameters constant [0.008M SDS (Surfactant), Calcination Conditions (600°C and 3h), Hydrothermal Reaction Time 4h].
Hydrothermal Reaction Temperature (°C)
Table: 3 Synthesis of CaO nanoparticles by changing surfactant concentration and keeping other parameters same [Hydrothermal Conditions (180 °C and 4h), Calcination Conditions (600°C and 3h)]
Surfactant Conentration (M)
Table: 4 Preaparation of Al/CaO nanoparticles by using CaO precursor of variant Surfactant concentration. [Hydrothermal Conditions (180 °C and 4h), Calcination Conditions (600°C and 3h)]
Surfactant Conentration (M)
Method of Characterization:
Chemicals and Solutions:
15ppm solution of 2,4,6-Trinitrophenol (Picric acid)
5mg CaO nanoparticles
5 mg Al/CaO nanoparticles
Measurement of Catalytic Activity by UV-VIS Spectrophotometer:
The catalytic activity of samples synthesised by hydrothermal method by changing different parameters [Table 2, 3, 4] was determined. For this purpose, 15 ppm solution of 2,4,6 Trinitrophenol was prepared in 100ml of distilled water and 5 mg of the nanocatalyst was added to 25 ml of this solution. The spectra of 2,4,6 Trinitrophenol solution was obtained before and after addition of catalyst. The solution with nano-catalyst was placed under UV irradiation with constant magnetic stirring for 15 minutes at ambient temperature. The absorbance of the sample was taken at λmax 356 nm after every 1 min interval.
High Performance Liquid Chromatography:
The picric acid was also analysed by DAD HPLC by using C18 column. A 15ppm solution of picric acid was prepared in double distilled water; there were three types of solutions used.
15ppm solution of standard picric acid
15ppm solution of picric acid with CaO catalyst
15ppm solution of picric acid with Al/CaO catalyst
70% methanol [pH: 3.4] was used as mobile phase for all these solutions. The injection volume of standard picric acid was 20 µL. After 7.5 minutes of injection, a very sharp peak of 7.425 was observed at 355nm. The second solution was prepared by adding CaO nanocatalyst. It was constantly stirred under UV lamp irradiation for 15 min. Then it was filtered and an injection volume of 20 µL was injected in HPLC. Same procedure was repeated for third solution except, change of nanocatalyst.