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Teknik BioseparasiDina Wahyu

Genap/ Maret 2014

OutlineChemical Reaction Engineering

Pendahuluanmempelajari ruang lingkup teknik bioseparasi dan teknik “cel disruption”

Teknik Pemisahan Secara Fisika 2Mempelajari teknik pemisahan sedimentasi

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Teknik Pemisahan Secara Fisika 1Mempelajari teknik sentrifugasi pada bioseparasi

Koagulasi dan flokulasi Mengetahui teknik pemisahan dengan cara koagulasi dan flokulasi

Teknik Pemisahan Secara Fisika 3 Mempelajari teknik filtrasi pada bioseparasi

Adsorpsi Proses adsorpsi pada cairan dan gas, serta pengetahuan bahan adsorpsi

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Adsorpsi 2Kinetika Adsorpsi, Isotherm Adsorption7

Adsorpsi ≠ Absorbsi • Absorbsi – fase fluida ditransfer dari

satu medium ke medium lain (air diabsorpsi oleh spon)

• Adsorpsi – komponen fase fluida(cairan atau gas) tertentu ditransfer(cairan atau gas) tertentu ditransferdan dipertahankan pada bagianpermukaan padatan (partikel kecilterikat pada karbon)

• Absorbsimasuknya solut ke dalam bahan

padat (pada tingkat molekuler)

• Adsorpsiproses dengan solut terakumulasi

pada antarmuka cair-padat atau gas-

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pada antarmuka cair-padat atau gas-padat

Sorpsi = Adsorpsi + Absorbsi

Aplikasi adsorpsi dalam proses diindustri:

DehumidifikasiPenghilangan bau/warna/rasaPenghilangan bau/warna/rasaPenghilangan polutan gas (H2S)Pelunakan dan deionisasi airFraksionasi hidrokarbon

• Konsep Dasar:Melibatkan dua fase

1) Fluida yang mengandung solutproduk dan kontaminan

2) Padatan berpori (adsorben) yang secara selektif mengikat solut ataukontaminankontaminan

Proses melibatkan transfer komponendalam fase cair ke permukaan padatan.Melibatkan transfer massa dankesetimbangan pada antarmukapadatan/fluida

• AdsorbatSenyawa yang dihilangkan dari fasecair/gas

• AdsorbenFase padat tempat akumulasi terjadi

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• ContohWarna dapat dihilangkan dari air menggunakan karbon aktif. Warna adalah adsorbat dan karbon aktifadalah adorben

Adsorbat• Rasa dan Bau• Senyawa Organik Sintetik

- Solven aromatik (benzen, toluen)- Pestisida , herbisida

• Humic substancesSenyawa organik alami, umumnya

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Senyawa organik alami, umumnyapembentuk warna, dengan ukuranmolekul berkisar antara beberapa ratussampai ratusan ribuHalometan dapat terbentuk jika air yang mengandung humic substances diklorinasi.Molekul metan dengan halogen (Cl, Br,...) menggantikan H, beberapa bersifat karsinogen

Adsorbat• Logam

Arsen, perak, merkuri

• Virus

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• Virus

• Senyawa anorganik lainnyaKlorin, bromin

Adsorben• Karbon Aktif

Mampu menghilangkan semuaadsorbatAdsorben paling populer

• Resin Sintetik

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• Resin Sintetik

• ZeolitTanah pemucat dengan sifat Adsorpsi

• Silika gel

Karbon Aktif• Karbon yang telah dipirolisis (dipanaskan

dengan sedikit oksigen)

Membakar tar, menguapkan gasMenghasilkan bahan dengan banyak pori

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Menghasilkan bahan dengan banyak porisehingga mempunyai luas permukan besar(500 - 1000 m2/g)Menghasilkan bagian Adsorpsi aktif

• Karbon bersifat non-polar, baik untukAdsorpsi senyawa non-polar

Activated Carbon Picture

13Source: solomon.bond.okstate.edu/thinkchem97/experiments/lab7.html

Tipe• PAC: Powdered activated carbon

A fine powder, < 0.05 mm dia.

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• GAC: Granular activated carbon 0.3 - 3 mm

Silica gel• Paling banyak digunakan sebagai

adsorben dalam kromatografikolom dan lapis tipis

• Dibuat dengan mengasamkansodium silikat dengan asam sulfatdiikuti dengan pencusian dengandiikuti dengan pencusian denganair dan pengeringan

• Sisi aktif silika gel merupakankelompok hidroksil yang terikatpada atom silikon.

OH OH

Si---------O-------Si

Tipe Adsorpsi

• Adsorpsi fisikHasil dari gaya intermolekuler yang menyebabkan pengikatan senyawatertentu pada adsorben tertentutertentu pada adsorben tertentuBersifat reversibel dengan penggunaanpanas (uap air, gas inert panas, oven) Pengikatan lapisan luar dari adsorben

• Adsorpsi kimia (kemisorbsi)Hasil dari interaksi kimiaSejumlah panas dilepaskanIrreversibelTerdapat dalam katalisis

Adsorpsi Fisik• Ikatan Elektrostatik

Partikel bermuatan berlawanan

• Interaksi Dipol-DipolIkatan antara Dua Senyawa Polar

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Ikatan antara Dua Senyawa PolarSenyawa polar mempunyai

distribusi muatan yang tidak sama(satu ujung mempunyai muatan + yang lain bermuatan -)

• Ikatan HidrogenInteraksi dipol-dipol, melibatkan

atom hidrogen dengan muatanpositif

• Ikatan Van der Waals

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• Ikatan Van der WaalsIkatan yang lemah disebabkan olehdua molekul non polar yang berdekatan menyebabkan perubahandalam distribusi muatan, menghasilkan ikatan dipol-dipol

Tahap Separasi Adsorpsi

1. Preadsorpsi: adsorben dalamfluida bebas solut

2. Menambahkan aliran prosestermasuk solut produk dansolut lainsolut lain

3. Adsorpsi terjadi, solutproduk berikatan denganadsorben sedangkan yang lainnya lewat

4. Pencucian (tidak selalu) adsorben melepaskanimpuritis yang tersisa

5. Elusi: merecover solut5. Elusi: merecover solutproduk

6. Regenerasi adsorben

Adsorpsi

• Molekul cenderung berada padatingkat energi yang lebih rendah

• Molekul dapat berada pada tingkat

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• Molekul dapat berada pada tingkatenergi yang lebih rendah dengan caramelekat pada permukaan padatan

senyawa hidrofob

Kesetimbangan

• Pada kesetimbangan: Terlarut dalam fase cairTeradsorpsi pada adsorben fase padat

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Teradsorpsi pada adsorben fase padat

• Adsorpsi bersifat reversibel:Desorbsi

Adsorption chromatography

• Fase stasioner dalam adsorption chromatography disebut adsorben

• Jika cairan digunakan sebagai fase mobildisebut Liquid-Solid Chromatography (LSC) disebut Liquid-Solid Chromatography (LSC) e.g. TLC and HPLC

• Jika gas digunakan sebagai fase mobildisebut Gas-Solid Chromatography (GSC) e.g. Gas Chromatography (GC)

Pada adsorption chromatographyterdapat dua tipe gaya:

• Gaya tarik solut pada adsorben (fasestasioner)

• Gaya yang melepaskan solut dari• Gaya yang melepaskan solut dariadsorben untuk bergerak bersamafase mobil

Gaya tarik:

= Adsorpsi fisik= Adsorpsi fisik

Gaya penyebab pergerakan solut

• Elusi:Kecenderungan solut terlarut danbergerak dengan fase mobil.Solven yang digunakan sebagai fasemobil harus mampu melarutkanmobil harus mampu melarutkansolut sehingga terjadi kompetisidengan gaya adsorpsi dari fasestasioner.Jika digunakan solven yang sangatkuat, maka akan mencuci solut tanpapemisahan.

• Displacement:Dalam kasus molekul solvenberkompetisi dengan solut pada sisiadsorpsi fase stasioner.adsorpsi fase stasioner.Kompetisi ini menyebabkan solutbergerak dalam kecepatan yangberbeda

Langmuir Isotherm:This model assumes monolayer coverage and constant binding energy between

surface and adsorbate. The model is:

0a e

ee

K Q Cq

1 K C

0Q

e1 K C represents the maximum adsorption capacity

(monolayer coverage) (g solute/g adsorbent).

Ce has units of mg/L.

K has units of L/mg

0aQ

BET (Brunauer, Emmett and Teller) isotherm:This is a more general, multi-layer model. It assumes that a Langmuir isotherm

applies to each layer and that no transmigration occurs between layers. It also

assumes that there is equal energy of adsorption for each layer except for the first

layer.

QCKq

0aeB

e

)}C/C)(1K(1){CC(

qSeBeS

e

CS =saturation (solubility limit) concentration of the solute. (mg/liter)

KB = a parameter related to the binding intensity for all layers.

Note: when Ce << CS and KB >> 1 and K = KB/Cs BET isotherm approaches

Langmuir isotherm.Langmuir isotherm.

Freundlich Isotherm:For the special case of heterogeneous surface energies (particularly good for mixed wastes) in which the energy term, “KF”, varies as a function of surface coverage we use the Freundlich model.

n and KF are system specific constants.

n1

eFe CKq n and KF are system specific constants.

Determination of appropriate model:

To determine which model to use to describe the adsorption for a particular

adsorbent/adsorbate isotherms experiments are usually run. Data from these

isotherm experiments are then analyzed using the following methods that are

based on linearization of the models.

For the Langmuir model linearization gives:

0a

e0ae

e

Q

C

QK

1

q

C

A plot of Ce/qe versus Ce should give a straight line with intercept

:

0aQK

1

0aQ

1and slope:

Or:

00 C

1

QK

1

Q

1

q

1

e0a

0ae CQKQq

Here a plot of 1/qe versus 1/Ce should give a

straight line with intercept 1/Qao and slope

0aQK

1

For the Freundlich isotherm use the log-log version :

Clogn

1Klogqlog Fe

A log-log plot should yield an intercept of log KF and a slope of

1/n.

0aBS

e0aB

B

eeS

e

QK

1

C

C

QK

1K

q)CC(

C

1

For the BET isotherm we can arrange the isotherm equation to get:

Intercept =0aB QK

B

0B a s

K 1

K Q C

Slope =

Factors which affect adsorption extent (and therefore affect isotherm) are:

Adsorbate:Solubility

In general, as solubility of solute increases the extent of adsorption decreases. This is known as the “Lundelius’ Rule”. Solute-solid surface binding competes with solute-solvent attraction as discussed earlier. Factors which affect solubility include molecular size (high MW- low solubility), ionization (solubility is minimum when compounds are uncharged), polarity (as polarity increases get higher solubility because water is a polar solvent). because water is a polar solvent).

pHpH often affects the surface charge on the adsorbent as well as the charge on the solute. Generally, for organic material as pH goes down adsorption goes up.

TemperatureAdsorption reactions are typically exothermic i.e., D H rxn is generally negative. Adsorption reactions are typically exothermic i.e., D H rxn is generally negative. Here heat is given off by the reaction therefore as T increases extent of adsorption decreases.

Presence of other solutes

In general, get competition for a limited number of sites therefore get reduced

extent of adsorption or a specific material.

Adsorbent:Virtually every solid surface has the capacity to adsorb solutes. From the

wastewater/water treatment point of view activated carbon (AC) is the adsorbent

of choice. AC prepared from many sources:

•Wood

•Lignite

•Coal

•Nutshells

•Bone

These raw materials are pyrolyzed at high temperature under low oxygen

conditions (so we don’t get complete combustion). This forms a “char”. The

char is then activated by heating to 300 – 1000 oC in the presence of steam,

oxygen or C02.

Result: “Activated carbon” which is highly porous, micro-crystalline material

which resembles graphite plates with some specific functional groups (e.g.

COOH, OH)COOH, OH)

Increasing magnification

Surface area of the AC is huge. Most of the surface area is interior in micro- and

macropores. Typical surface area is in the range of 300-1500 m2/gram.

Quality and hardness of the AC are a function of the starting material and the

activation process.

Pore size distribution:

micropores: <2nm dia

mesopores: 2nm to 20 nm dia

macropores: > 20 nm

Pore size % pore volume

% surface area

Micro 30 - 60 >95

Meso < 10 < 5

Macro 25 - 30 negligible

Most of the surface area is in pores of molecular sized dimensions. This results in slower mass transfer during the adsorption process but also results in greater binding capacity of the adsorbate.Adsorption behavior is related in part to the nature of the functional groups on the carbon surface. In general carbon manufactured at:<500 oC is weakly acidic> 500 oC is weakly basicSpent AC can be regenerated at high temperatures (roughly a maximum of fifteen Spent AC can be regenerated at high temperatures (roughly a maximum of fifteen times).

Adsorption Kinetics.Adsorption onto AC usually is modeled as a three consecutive step process.

These steps are film transport (through the stagnant boundary layer about the

AC particle); transport of the solute through the internal pores; and finally

adsorption to the surface site. One or more of these steps can limit the rate of

solute adsorption. In most cases the actual adsorption process does not limit the

process. In some cases film transport limits and in other cases (most likely) pore

diffusion limits.diffusion limits.

We can lump all the mass transport resistance terms into one term, k, and write:

)CC(akt

Ce

k = overall mass transfer coefficient (cm/min)

a = surface area of carbon per unit volume of reactor (1/cm)a = surface area of carbon per unit volume of reactor (1/cm)

Ce = concentration that would be in equilibrium with

actual amount of solute adsorbed, q (g/liter).

C = actual concentration of solute in bulk solution. (g/liter).

Fresh CarbonTreated Effluent

“S” zone: C goes from C0 to approx. 0

Effluent zone C approx. 0

Exhausted CarbonWaste Influent

Saturated zone: C = C0C/C0 1

0

MANUFACTURE OFACTIVATED CARBON:DIFFERENT RAW MATERIALS

MANUFACTURE OF ACTIVATED CARBON FROM COAL

ACTIVATIONFURNACE TYPES

Rotary kiln

Multiple Hearth ↑

DIFFERENT PHYSICAL FORMS OF ACTIVATED CARBON

First magnification of carbon granules

Continued magnification

Continued magnification

Continued conceptual magnification

Continued conceptualmagnification

Continued conceptualmagnification

ScanningElectronMicroscopePhoto ofMicroscopePhoto ofGAC

Area of a fewgrams ofactivatedcarbon

ApplicationMethodologyMethodology

Granular ActivatedCarbon Columns

GAC Silos

Gas Purification

ContactingColumnInternalsInternals

Typical isothermsolid-phase concentration (y-axis) vs liquid phase concentration (x-axis)

This is a favorable isotherm: higher solid-phase concentration at low liquid concentrations

Column Hydraulics

Adsorptive Forces

The effect of molecular size andfunctional groups on adsorbability

Langmuir isotherm

Freundlich isotherm (linear scale)

Freundlich isotherm, log-log scale

-1.5

-1

-0.5

0

-2 -1.5 -1 -0.5 0 0.5

Lo

g (

x/m

)

Freundlich isotherm, compared with real data

-3

-2.5

-2

Log C

Lo

g (

x/m

)

Four GAC columns in series

REACTIVATION OF ACTIVATED CARBON

Transport of GAC

Decentralized Multiple Hearth Regeneration Facility

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