EXPERIMENTALTwo natural bentonites

EXPERIMENTAL
Two natural bentonites (named K and W) from two different deposits of the Mendoza province, Argentine, were used as the starting materials. Tonsil, a commercial acid-activated bentonite extensively used in the vegetable oil industry, was used as reference for the evaluation of the bleaching capacity in the experiments. Alkali-refined sunflower oil was gently donated by Bunge Alimentos S.A (Gaspar-SC, Brazil). The bentonite sample (40 g) was treated with 400 mL of 4 N or 8 N sulphuric acid (analytical grade) at 90°C for 3.5 h (Foletto et al., 2003) in a stirred glass reaction vessel with reflux. After the acid treatment, the sample was filtered and washed with distilled water until free of SO42-. The samples were dried at 60°C for 12 h and ground to pass through a 0.074 mm sieve. Activated samples were designated as K4, K8, W4 and W8, where the numerical value indicates the concentration of acid solution used for the treatment. Bleaching experiments were conducted by a procedure analogous to that of the American oil Chemical Society (AOCS) Official Method Cc 8a-52. The bleaching process was carried out under a vacuum of 450 mmHg at the constant temperature of 100°C with a contact time of 30 min. Stirring and heating were carried out by means of a mechanical stirrer and an electric heating band. The ratio of the mass of clay to the volume of acid solution was 1:10 (w/v). During the bleaching, a stream of N2 was maintained above the oil surface. The hot oil and clay mixture was filtered under vacuum and the color of the bleached oil was measured spectrophotometrically (WFJ525-W UVvisible spectrophotometer). The bleaching capacity percentage of the clays was determined from the equation (Falaras et al., 1999):

where “A0” and “A” are the absorbance of neutral oil and bleached oil, respectively, at the maximum absorbance wavelength of the neutral oil (420 nm). The structural changes of the Argentinean acid bentonites were examined by means of thermogravimetric (TGA) and infrared spectrometric (IR) analyses and chemical analysis (XRF). TGA was performed with a Netzsch STA 409 thermal analyzer at a heating rate of 10°C.min-1 under a flow of atmospheric air of 35 mL min-1, in the temperature range 25-1000°C. IR spectra were recorded in the region 4000-350 cm-1 with a Perkin-Elmer 16 PC spectrophotometer, using the KBr pellet technique. Chemical compositions of the samples were determined by X-ray fluorescence with a Philips PW 2400 spectrometer.

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EKSPERIMEN
Dua bentonit alam (bernama K dan W) dari dua deposito yang berbeda dari provinsi Mendoza, Argentina digunakan sebagai bahan awal. Amandel, sebuah bentonit asam-diaktifkan komersial secara luas digunakan dalam industri minyak nabati, yang digunakan sebagai acuan untuk evaluasi kapasitas pemutihan dalam percobaan. Minyak bunga matahari alkali halus dengan lembut disumbangkan oleh Bunge Alimentos SA (Gaspar-SC, Brazil). The bentonit sampel (40 g) diperlakukan dengan 400 ml 4 N atau 8 N asam sulfat (kelas analitis) pada 90 ° C selama 3,5 jam (Foletto et al., 2003) dalam bejana reaksi kaca diaduk dengan refluks. Setelah pengobatan asam, sampel disaring dan dicuci dengan air suling sampai bebas dari SO42-. Sampel dikeringkan pada 60 ° C selama 12 jam dan tanah untuk melewati saringan 0,074 mm. Sampel diaktifkan ditetapkan sebagai K4, K8, W4 dan W8, dimana nilai numerik menunjukkan konsentrasi larutan asam yang digunakan untuk pengobatan. Percobaan pemutihan dilakukan dengan prosedur yang analog dengan minyak American Chemical Society (AOCS) Official Metode Cc 8a-52. Proses bleaching dilakukan di bawah vakum dari 450 mmHg pada suhu konstan 100 ° C dengan waktu kontak 30 menit. Pengadukan dan pemanasan dilakukan dengan cara pengaduk mekanik dan band pemanas listrik. Rasio massa tanah liat untuk volume larutan asam adalah 01:10 (w / v). Selama pemutihan, aliran N2 dipertahankan di atas permukaan minyak. Campuran minyak dan tanah liat panas disaring di bawah vakum dan warna minyak dikelantang diukur spektrofotometri (WFJ525-W spektrofotometer UVvisible). Persentase kapasitas pemutihan lempung ditentukan dari persamaan (Falaras et al, 1999.): Di mana "A0" dan "A" adalah absorbansi minyak netral dan minyak dikelantang, masing-masing, pada panjang gelombang absorbansi maksimum minyak netral (420 nm). Perubahan struktural dari bentonit asam Argentina diperiksa dengan cara termogravimetri (TGA) dan spektrometri inframerah (IR) analisis dan analisis kimia (XRF). TGA dilakukan dengan Netzsch STA 409 analyzer termal pada tingkat pemanasan 10 ° C.min-1 di bawah aliran udara atmosfer dari 35 mL min-1, dalam kisaran suhu 25-1000 ° C. Spektrum IR tercatat di wilayah tersebut 4000-350 cm-1 dengan Perkin-Elmer 16 PC spektrofotometer, menggunakan teknik pelet KBr. Komposisi kimia dari sampel ditentukan dengan X-ray fluorescence dengan Philips PW 2400 spektrometer.