Qhov sib txawv tseem ceeb ntawm Langmuir thiab Bet isotherm yog Langmuir isotherm piav qhia txog monolayer molecular adsorption, whereas BET isotherm piav qhia txog ntau txheej molecular adsorption.
Ib qho isotherm, hauv chemistry, yog qhov nkhaus ntawm qhov ntim piv rau qhov kub thiab txias piv rau lub siab, uas qhia tau hais tias ib theem kub. Lo lus "isotherm" yog muab los ntawm "iso", xa mus rau ib theem thiab "therm", hais txog qhov kub thiab txias.
Langmuir Isotherm yog dab tsi?
Langmuir adsorption isotherm yog txoj hauv kev siv los kwv yees cov kab tawm adsorption ntawm qis adsorption ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom ntom. Nws yog ib qho kev qhia theoretical, thiab cov tshuaj sib npaug rau cov lus no yog raws li hauv qab no:
X/M=abc(1 + ac)
Qhov twg X yog qhov hnyav ntawm cov kua dej nqus, M yog qhov loj ntawm cov adsorbent, c yog qhov sib npaug ntawm cov kua nplaum, thiab a thiab b yog qhov tsis tu ncua. Ntxiv mus, Langmuir adsorption isotherm yog siv rau monolayer adsorption mus rau ib homogeneous nto. Txawm li cas los xij, yuav tsum tsis txhob muaj kev cuam tshuam ntawm hom adsorbed.
Bet Isotherm yog dab tsi?
BET isotherm piav qhia txog qhov adsorption ntawm cov roj molecules ntawm cov khoom siv. Lub sij hawm BET sawv cev rau Brunauer-Emmett-Teller isotherm. Cov txheej txheem no ua haujlwm raws li lub hauv paus rau txoj kev tsom xam tseem ceeb, uas yog ib qho tseem ceeb rau kev ntsuas ntawm ib cheeb tsam ntawm cov khoom siv. Peb tuaj yeem soj ntsuam nws raws li lub cev adsorption lossis physisorption. Qhov kev xav no tau qhia los ntawm Stephen Brunauer, Paul Hugh Emmett, thiab Edward Teller hauv xyoo 1938.
Txoj kev xav no tuaj yeem siv rau cov txheej txheem ntawm ntau txheej adsorption, thiab nws feem ntau siv cov pa roj carbon monoxide (lub npe hu ua adsorbent) txhawm rau txheeb xyuas qhov chaw tshwj xeeb. Nitrogen gas yog ib hom roj absorbate siv nyob rau hauv qhov chaw soj ntsuam los ntawm BET txoj kev.
Daim duab 01: BET Model
Peb tuaj yeem pom tias BET isotherm yog qhov txuas ntxiv ntawm txoj kev xav ntawm Langmuir isotherm. Qhov kev txuas ntxiv no tshwm sim los ntawm monolayer adsorption mus rau multilayer adsorption. Txawm li cas los xij, muaj qee qhov kev xav uas peb yuav tsum xav txog thaum siv qhov isotherm:
- Gas molecules lub cev tau adsorbed infinitely ntawm cov khoom hauv txheej
- Gas molecules tsuas yog nrog cov txheej uas nyob ib sab
- Peb tuaj yeem siv Langmuir txoj kev xav rau txhua txheej
- Enthalpy rau adsorption los ntawm thawj txheej yog tas li, thiab nws yog ntau dua li ntawm ob txheej
- Enthalpy ntawm adsorption ntawm ob txheej yog sib npaug rau enthalpy ntawm liquefaction
Qhov txawv ntawm Langmuir thiab Bet Isotherm yog dab tsi?
Ib qho isotherm, hauv chemistry, yog qhov nkhaus ntawm qhov ntim piv rau qhov kub thiab txias piv rau lub siab, uas qhia tau hais tias ib theem kub. Langmuir adsorption isotherm yog txoj kev siv los kwv yees cov kab tawm adsorption ntawm cov adsorption tsawg thiab qhov siab tshaj plaws ntawm qhov chaw ntawm cov hlau ntau dua. BET isotherm piav qhia txog qhov adsorption ntawm cov roj molecules ntawm ib qho khoom nto. Qhov sib txawv tseem ceeb ntawm Langmuir thiab Bet isotherm yog Langmuir isotherm piav qhia txog monolayer molecular adsorption, whereas BET isotherm piav qhia ntau txheej molecular adsorption.
Summary – Langmuir vs Bet Isotherm
Ib qho isotherm yog qhov nkhaus ntawm qhov ntim piv rau qhov kub thiab txias piv rau daim duab siab, uas qhia txog qhov ntsuas kub ib zaug. Qhov sib txawv tseem ceeb ntawm Langmuir thiab Bet isotherm yog Langmuir isotherm piav qhia txog monolayer molecular adsorption, whereas BET isotherm piav qhia ntau txheej molecular adsorption. Peb tuaj yeem txhais tau Langmuir Adsorments yog tus qauv los twv seb cov khoom lag luam tawm ntawm cov roj av qis dua thiab cov adsorption ntawm cov roj av ntawm cov av.
