2. Materials and Methods
2.1 Materials
The materials used for the present work are virgin soy oil (SOYA), soy
oil used in frying (donated by a local supplier) and Magnesol®(DALLAS GROUP). Reagents with analytical grade - 99.8% Methanol
(ANIDROL), 85% Potassium hydroxide-KOH (VETEC), 99%
Tetrahydrofuran-THF (VETEC), 99.18% Hexane (NEON), 99.5% Ethyl acetate
(VETEC), 99.8% Dichloromethane (MERCK), 99.8% acetonitrile (VETEC) and
97% NaOH (VETEC) - were purchased from a local supplier and used
without pre-treatment.
2.2. Methods
The methodology developed in this work is illustrated in Figure 1, which
is described in two sections: biodiesel production and recovered of
Magnesol® .
2.2.1 Biodiesel Production
First, on a bench scale biodiesel plant, 10 L of biodiesel was produced
through a batch process from soybean frying oil and virgin soybean
oil. After, the oils (virgin and
frying) had their acidity corrected with KOH, as they were not in
compliance with the requirements of the National Agency of Petroleum,
Natural Gas and Biofuels (ANP). Posteriorly, the two biodiesels were
produced using the same conditions, through the alkaline
transesterification process with KOH 1% (w/w). Thus, the conditions
used in this process were: 6:1 methanol/oil ratio, 65 °C temperature and
1.5 h reaction time. The reactions occurred under constant agitation and
constant oil pumping in the reactor for better homogenization. After
that, the biodiesels sat for approximately 30 h before the separation of
glycerin was carried out, and after which the excess methanol was
removed by heating at 65 °C for 1 h (Kucek et al., 2007).
Purification of biodiesel was performed by the dry route with 1% w/w
Magnesol®/biodiesel, heated at 50 °C under constant
stirring for 30 minutes. After this time, the biodiesel was vacuum
filtered and the adsorbent was taken for purification (Farag and
El-Anany, 2006).
2.2.2 Recovered of
Magnesol®
The magnesol extracted from the biodiesel purification process was
purified according to the methodology presented in Figure 2, to which 1g
of contaminated magnesol was placed in a conical flask and 11.2 ml THF
was added (30:1 ratio (w/w)). The system was stirred for 30 min,
subsequently being centrifuged for 3 minutes at 4000 rpm for decantation
of Magnesol® and removal of the supernatant. This process was repeated
three times, and at the end the product was dried at 70 °C for 24h.
2.4. Characterizations
2.4.1. Characterization of Purified and Unpurified
Biodiesel
Some parameters of the biodiesels from the virgin soybean oil and frying
oil were analyzed in order to compare the efficiency of the purification
with virgin and recovered Magnesol®. The main parameters were
established in accordance with the standards described below.
Determination of acid
value
Based on standard EN14104, 2.5 g of biodiesel was placed in a 250 ml
erlenmeyer flask and 50 mL of ethyl ether/ethanol 2:1 was added,
stirring until complete dissolution. Two drops of phenolphthalein
solution - 1% in ethanol - was added, and it was titrated with a
standardized solution of 0.1 M NaOH. The analyses were performed in
triplicate and the results were expressed as mg KOH/g sample (Alves et
al., 2016).
Determination of the
glycerol
For the determination of glycerol ester contents, about 250 mg of
biodiesel was transferred into a glass balloon and 5 ml methyl
heptadecanoate - internal standard solution (C17;
10 mg/ml) - was added. Approximately 1.0 μl of the prepared solution was
injected into a GC-14B Shimadzu gas chromatograph, equipped with a Flame
Ionization Detector detector and a capillary column (DB-5MS,
30 m × 0.25 mm ID, THK 1µm, Agilent). Nitrogen gas was used as the
mobile phase. The concentration of methyl esters in biodiesel samples
was calculated using the GC data by the method presented in
EN14103:2003(E).
Determination of the flash
point
The flash point was determined according to ASTM D 93 which limits its
minimum value to 100 °C. The equipment used was a FLASHPOINT TESTER -
HFP339 - Pensky Martens.
2.4.2 Analysis of the Purified and
Unpurified
Magnesol®
Elemental
Analysis
The total carbon percentage (%TC) and total nitrogen percentage (%TN)
was performed analysing the samples in the TruSpec CHN non-dispersive
elemental analyser, mark LECO®, equipped with an
infrared detector for carbon and hydrogen, and a thermal conductivity
detector for nitrogen. For the determination, a small amount of the
sample was used, which ranged from 50 mg to 100 mg (± 0.01). The samples
were weighed into thin sheets of tin and taken directly to the
equipment. The samples were burned under a 6.0 oxygen (99.9999 %)
atmosphere with 10 lpm flow and 950 ºC LECO® according
to the ASTM D5291-16. The test was performed in triplicates (Ramos et
al., 2015).
Field Emission Scanning Electron
Microscopy
(FEG-SEM)
The surface morphology of pure and recovered Magnesol®was studied using a FEG-SEM, FEI Inspect F50 equipment, and the samples
were coated with a thin layer of gold. The dimensions were calculated
using the program Image J (n = 20).
Fourier Transform Infrared
Spectroscopy
(FTIR)
FTIR analysis was performed using a Perkin Elmer Instruments Spectrum
One FTIR Spectrometer, and spectrum acquisition was performed with the
Attenuated Total Reflectance (ATR) sample attachment in the 650 to 4000
cm-1 wave number range.
Thermogravimetry analysis
(TGA)
The thermal stability was evaluated by thermogravimetric analyses using
the SDT- Q600 model (TA Instruments) in the range 25 - 800°C with a
heating rate of 20 °C.min-1 under nitrogen. The weight
of the sample was approximately 7.8 mg, and the analysis was carried out
in triplicate.