BIPHASIC CRUDE PALM OIL DECHLORINATION: EFFECT OF VOLUME RATIO AND CONCENTRATION OF SODIUM SILICATE TO HYDROXIDE ION DISTRIBUTION
Authors: Hari Zulfa Kurnia Umani , Abdullah Syamsul Bahari , Jamari Saidatul Shima , Che Mat Che Rahmat , Mahmud Mohd Sabri 
Published: January 2024

Dechlorination of crude palm oil (CPO) to prevent toxic contaminant formation inspired studies of applying alkaline in its treatments. This paper reports distribution of hydroxide ion (OH-) from sodium hydroxide (NaOH) and sodium silicate (SS) between aqueous solution and CPO under equilibrium systems to moderate its presence in CPO and minimize saponification. In this study, OH- was determined through pH measurements, which also indicated sodium hydroxide (NaOH) presence. Filtered CPO was mixed with SS solution at room temperature in various volume ratios and SS concentrations under 800-rpm agitation before being settling down to form layers of liquids. The One-Factor-in-A-Time approach was used to optimize the ratio. Acid value test and GCMS analyses were used to determine free fatty acids. Calibration curve construction revealed 0.0818 of OH- dissociation constant. SS solution could turn to acidic at 6.344 × 10-5 g/ml of concentration probably due to hydrated silica. Using 0.01 g/ml SS solution, volume ratios between CPO and SS solution spanning from 0.33 to 3 were all under alkaline conditions but decreasing OH- concentration, where 2 liquid phases only appeared in the ratio of 2.33 and 3. Concentration of SS was then varied for the 2.33 volume ratio and a sigmoid trend of OH- increase was evident. The McCabe-Thiele plot revealed hydroxide ion equilibrium below operating line suggesting its extraction impossibility to CPO.
ABSTRAK: Penyahklorinan minyak sawit mentah (MSM) bertujuan mencegah pembentukan bahan cemar toksik telah mendorong penggunaan alkali dalam rawatan minyak itu. Manuskrip ini melaporkan taburan ion hidroksida (OH-) daripada sodium hidroksida dan sodium silikat (SS) antara larutan akueus dan MSM di bawah keadaan penampan untuk mengurangkan kehadirannya dalam MSM bagi mengelakkan pembentukan sabun. Dalam kajian ini, kepekatan OH- ditentukan melalui pengukuran pH, yang juga merupakan petunjuk kepada kewujudan NaOH. MSM yang ditapis dicampur dengan larutan SS pada suhu bilik dalam pelbagai nisbah isipadu dan kepekatan di bawah pengadukan 800 rpm sebelum diendapkan untuk membentuk lapisan cecair. Pendekatan Satu-Faktor-Sekali telah digunakan untuk mengoptimakan nisbah tersebut. Ujian nilai asid dan analisis GCMS digunakan untuk menentukan kandungan asid lemak bebas. Penjanaan lengkung penentu-ukuran membolehkan pemalar pelepasan OH- diperoleh iaitu 0.0818. Larutan SS boleh bertukar asid pada kepekatan 6.344 × 10-5 g/ml mungkin disebabkan silika yang terhidrasi. Dengan menggunakan larutan SS 0.01 g/ml, nisbah isipadu antara MSM dan larutan SS dari 0.33 ke 3 berkeadaan alkali dan menurun kepekatan hidroksida. 2 fasa cecair hanya wujud pada nisbah 2.33 dan 3. Kemudian kepekatan SS diubah-ubah untuk nisbah isipadi 2.33 itu dan corak sigmoid hidroksida diperoleh. Plot McCabe-Thiele mendapati keseimbangan kepekatan hidroksida berada di bawah garisan operasi menunjukkan pengekstrakan adalah mustahil berlaku terhadap OH- ke dalam MSM.