EXTRACTION. Unit Operasi 2014

Transkripsi

1 EXTRACTION Unit Operasi 2014 Extraction a separation process, based on differences in solubility Extraction is one of the most useful and widely used chemical separation methods. There are two types of extraction process: Solid Liquid Extraction (termasuk Supercritical Fluid Extraction) Liquid Liquid Extraction 1

2 Solid-liquid Extraction (leaching) a solute is extracted from a solid phase with the help of a solvent. Contoh: ekstraksi kopi dari biji kopi pada pembuatan kopi instan ekstraksi senyawa antimikroba dari berbagai jenis daun ekstraksi kalsium oksalat dari tepung porang (pemurnian/pencucian tepung porang) Mekanisme Leaching keterangan : 1. pelarut, 2. padatan (mengandung komponen terlarut), 3. komponen terlarut, 4. padatan (tidak mengandung komponen terlarut), 5. komponen terlarut dalam pelarut 2

3 Mekanisme Leaching komponen terlarut yang terperangkap di dalam padatan, bergerak melalui pori-pori padatan komponen terlarut berdifusi keluar permukaan partikel padatan dan bergerak ke lapisan sekitar padatan, selanjutnya ke larutan Proses ekstraksi padat-cair 3

4 Multistage Extraction Liquid-liquid Extraction Liquid extraction (or solvent extraction) merupakan operasi dimana komponen terlarut dipisahkan dengan menambahkan pelarut cair yang sesuai. Pada operasi ini, pemisahan komponen bergantung pada perbedaan distribusi komponen terlarut diantara dua fase cairan. The mass transfer of the solute liquid takes place from the feed solution to the solvent phase. 4

5 Basic Steps Typical liquid-liquid extraction operations utilize the differences in the solubilities of the components of a liquid mixture. The basic steps involved include: 1. Contacting the feed with the extraction solvent. 2. Separation of the resulting phases 3. Removal/recovery of solvent from each phase. Liquid-liquid extraction is a useful method to separate components (compounds) of a mixture 5

6 The concept of liquid-liquid extraction Liquid-liquid extraction is based on the transfer of a solute substance from one liquid phase into another liquid phase according to the solubility. Extraction becomes a very useful tool if you choose a suitable extraction solvent. You can use extraction to separate a substance selectively from a mixture, or to remove unwanted impurities from a solution. In the practical use, usually one phase is a water or waterbased (aqueous) solution and the other an organic solvent which is immiscible with water. The success of this method depends upon the difference in solubility of a compound in various solvents. For a given compound, solubility differences between solvents is quantified as the "distribution coefficient" Partition Coefficient / Distribution Coefficient (K) When a compound is shaken in a separatory funnel with two immiscible solvents, the compound will distribute itself between the two solvents. Normally one solvent is water and the other solvent is a water-immiscible organic solvent. Most organic compounds are more soluble in organic solvents, while some organic compounds are more soluble in water. 6

7 (1) If there are 30 particles of compound, these are distributed between equal volumes of solvent 1 and solvent 2. (2) If there are 300 particles of compound, the same distribution ratio is observed in solvents 1 and 2 (3) When you double the volume of solvent 2 (i.e., 200 ml of solvent 2 and 100 ml of solvent 1 ), the 300 particles of compound distribute as shown If you use a larger amount of extraction solvent, more solute is extracted An additional 67 particles are extracted with the second portion of extraction solvent (solvent 2 ).The total number of particles extracted from the first (200 particles) and second (67 particles) volumes of extraction solvent is 267.This is a greater number of particles than the single extraction (240 particles) using one 200 ml portion of solvent 2! It is more efficient to carry out two extractions with 1/2 volume of extraction solvent than one large volume! 7

8 If you extract twice with 1/2 the volume, the extraction is more efficient than if you extract once with a full volume. Likewise, extraction three times with 1/3 the volume is even more efficient. four times with 1/4 the volume is more efficient.five times with 1/5 the volume is more efficient The greater the number of small extractions, the greater the quantity of solute removed. However for maximum efficiency the rule of thumb is to extract three times with 1/3 volume Supercritical Fluid Extraction Supercritical fluid extraction (SCFE or SFE) is an extraction process carried out using a supercritical fluid as a solvent. A supercritical fluid (SCF) is a substance at a temperature and pressure above those of the critical point. 8

9 The density of supercritical fluids is close to that of the liquid while their viscosity is low and comparable to that of a gas. These two properties are the key to the functionality of SCFs as extractants. The relatively high density imparts to SCFs good solubilization power while the low viscosity results in particularly rapid permeation of the solvent into the solid matrix. Karbon dioksida (CO 2 ) merupakan pelarut yang paling umum digunakan dalam SFE. Pertimbangan penggunaan CO 2 : segera dapat dipisahkan dari bahan yang dilarutkan viskositas rendah, difusifitas tinggi, tidak berwarna, dan tidak mencemari lingkungan tidak mudah terbakar dan tidak mahal memiliki temperatur kritis 31 o C, sehingga sesuai untuk bahan yang sensitif thd panas 9

10 SFE System 10

11 TEKNOLOGI DAN APLIKASI SFE 1. EKSTRAKSI MINYAK MAKAN Keuntungan ekstraksi dengan CO 2 : Non toxic Mudah dipisahkan dari minyak yang diekstrak Minyak berkualitas tinggi Tidak memberikan pengaruh yang besar terhadap perubahan komponen gizi lainnya Ekstraksi minyak dari biji bunga matahari (canola) Kondisi yang diberikan sbb : berat biji bunga matahari : 4 gram suhu ekstraksi : 40 0 C tekanan ekstraksi : 35 Mpa Ekstraksi minyak dari dedak Kondisi yang diberikan sbb : berat dedak : 150 gram suhu ekstraksi : 35 0 C, ~ 5 jam tekanan ekstraksi : 4350 Psi 11

12 Ekstraksi minyak dari mesokarp (daging buah) Kondisi yang diberikan sbb : berat serpihan mesokarp : gram suhu ekstraksi : 40 0 C tekanan ekstraksi : Psi 2. Dekafeinasi Kopi Keuntungan: bebas residu pelarut Contoh soal: Suatu sampel mengandung komponen X sebanyak 350 partikel. Sampel tersebut memiliki volume 1 dm 3. Untuk mengekstrak komponen X dari sampel ditambahkan pelarut etanol sebanyak 100 cm 3. Komponen X dalam sampel 5 kali lebih terlarut dalam etanol daripada sampel. 1. Hitung berapa jumlah partikel yang didapatkan dengan ekstraksi 1 tahap! 2. Hitung berapa jumlah partikel yang didapatkan dengan ekstraksi 2 tahap (masing-masing tahap menggunakan ½ dari total pelarut) 12

13 Suatu sampel mengandung komponen X sebanyak 250 partikel. Sampel tersebut memiliki volume 1 dm 3. Untuk mengekstrak komponen X dari sampel ditambahkan pelarut etanol sebanyak 100 cm 3. Komponen X dalam sampel 6 kali lebih terlarut dalam etanol daripada sampel. 1. Hitung berapa jumlah partikel yang didapatkan dengan ekstraksi 1 tahap! 2. Hitung berapa jumlah partikel yang didapatkan dengan ekstraksi 2 tahap (masing-masing tahap menggunakan ½ dari total pelarut) TERIMAKASIH 13