Raws li paub zoo, qhov tshwm sim hu ua "concentration polarization" tshwm sim thaum lub sijhawm ua haujlwm ntawm nanofiltration thiab thim rov qab osmosis daim nyias nyias, ua rau daim nyias nyias fouling. Txij li thaum ultrafiltration tsis concentrate solutes, tsuas yog lim, qhov "concentration polarization" tshwm sim tsis tseem ceeb thaum lub sij hawm ultrafiltration membrane ua haujlwm. Txawm li cas los xij, ultrafiltration tuaj yeem khaws cov colloids, yog li qhov tshwm sim ntawm "gel txheej polarization" muaj qhov cuam tshuam tseem ceeb ntawm ultrafiltration membranes. Kab lus no qhia txog cov ntsiab lus, cov qauv, thiab qhov tseem ceeb ntawm engineering ntawm ultrafiltration membrane "gel txheej polarization" rau cov kws kho dej.
I. Lub tswv yim ntawm Gel Txheej Polarization
Thaum lub sij hawm ultrafiltration, thaum cov dej pub muaj ntau cov macromolecular solutes (xws li cov proteins, polysaccharides, colloidal hais, thiab lwm yam), cov tshuaj no accumulates nyob rau hauv daim nyias nyias, maj mam tsim ib tug concentrated txheej. Raws li kev pom zoo zuj zus, cov kua qaub nyob hauv cov txheej txheem concentrated nce, nws thiaj li mus txog qhov saturation solubility ntawm cov kua hauv lub cev, yog li tsim cov gel txheej ntawm daim nyias nyias. Tom qab cov ntaub ntawv gel txheej, txawm tias qhov sib txawv ntawm qhov sib txawv ntawm qhov sib txawv (TMP) tseem nce ntxiv, qhov permeate flux tsis nce ntxiv lawm. Cov txheej txheem no hu ua gel txheej polarization tswj. Raws li daim nyias nyias siab sib txawv nce, cov permeate txaus tus nqi pib nce thiab ces stabilizes.
II. Tus Qauv Zauv thiab Cov Qauv Ntsuas
1. Hloov sib npaug ntawm Gel Txheej Polarization
Thaum cov kua qaub concentration ntawm daim nyias nyias mus txog saturation, cov txheej txheem hloov loj ntawm cov kua nyob ze ntawm daim nyias nyias tuaj yeem suav nrog siv cov qauv hauv qab no:
Qhov twg: cm yog qhov concentration ntawm macromolecules ntawm daim nyias nyias; cp yog qhov concentration ntawm macromolecules hauv cov permeate; cb yog qhov nruab nrab concentration ntawm macromolecules nyob rau hauv cov dej pub nyob rau hauv lub membrane caij; Jw yog lub permeate flux; k yog qhov loj hloov coefficient ntawm daim nyias nyias.
Cov mis no nthuav tawm cov qauv ntawm macromolecule "sau" rau ntawm daim nyias nyias: (1) Ua kom muaj qhov sib tw nrawm thiab nce k tuaj yeem txo cov thickness ntawm gel polarization txheej; (2) Txo cov kev khiav hauj lwm flux tuaj yeem tswj cov concentration ntawm macromolecules ntawm daim nyias nyias hauv qab ntawm gel point.
2. Kev sib raug zoo ntawm Limiting Flux thiab siab tshaj plaws
Thaum cov concentration ntawm macromolecules cm ntawm daim nyias nyias nto mus txog qhov gel point cg, lub kaw lus nkag mus rau lub limiting flux xeev. Lub sijhawm no, cov mis hloov pauv loj tuaj yeem ua kom yooj yim rau cov qauv hauv qab no.
Qhov no txhais tau hais tias ib zaug kev khiav hauj lwm tej yam kev mob ua rau lub membrane nto concentration mus txog cg, ntxiv mus rau lub transmembrane siab sib txawv yuav tsis ua rau cov flux.
Qhov tseem ceeb ntawm engineering ntawm cov qauv no yog: (1) Hauv kev tsim cov txheej txheem, qhov kev txwv tsis pub dhau yog qhov tseem ceeb ntawm kev txiav txim siab qhov chaw ntawm daim nyias nyias thiab lub zog noj; (2) Kev ua haujlwm ruaj khov ntawm cov txheej txheem ultrafiltration yuav tsum zam kev ua haujlwm ntev - lub sijhawm ua haujlwm hauv cheeb tsam txwv tsis pub muaj flux.
3. Membrane Surface Pressure thiab Gel Layer Resistance
Lub xub ntiag ntawm cov gel txheej tsis tsuas yog cuam tshuam rau huab hwm coj hloov pauv, tab sis kuj tseem ua rau kom pom kev ua haujlwm zoo. Nws txoj kev qhia lej yog qhia hauv qab no.
Qhov twg: ki, gel yog cov coefficient tsis kam ntawm gel txheej rau macromolecular tshuaj i; Δl yog lub thickness ntawm gel txheej; Di, gel yog diffusion coefficient nyob rau hauv lub gel txheej.
Qhov no qhia tau hais tias thaum lub gel txheej yuav thicker (Δl nce) los yog cov diffusion nyob rau hauv lub gel txheej slows down (Di, gel txo), qhov loj hloov coefficient ki, gel yuav txo qis heev.
Hauv kev tsim engineering: (1) Qhov nce ntawm Δl tuaj yeem tswj tau los ntawm kev nce tus ntoo khaub lig- ntws shear quab yuam, txo cov kev daws teeb meem, lossis ua kom rov qab ntau zaus; (2) Txo qhov muaj zog viscosity nce Di, gel; qhov kub ntawm dej ntau dua, qhov viscosity qis dua. III.
III. Membrane Surface Concentration Distribution thiab tsim qhov tseem ceeb
Macromolecules muaj cov concentrations tsawg dua nyob deb ntawm daim nyias nyias, tab sis lawv cov concentrations sai heev nyob ze ntawm daim nyias nyias, tending ntawm saturation nyob rau hauv lub gel txheej. Tus qauv lej sib raug tau qhia hauv kab zauv hauv qab no:
Qhov twg: ki yog cov kua membrane loj hloov coefficient; ε yog gel txheej porosity.
Cov mis no qhia meej txog cov kua membrane huab hwm coj hloov pauv tsis kam thiab gel txheej diffusion kuj. Thaum cov ntsiab lus polymer hauv cov tshuaj yog siab lossis cov gel txheej yog tuab, qhov diffusion kuj nce ntxiv, ua rau nws yooj yim dua kom ncav cuag lub xeev txwv tsis pub ntxov ntxov.
Cov ntsiab lus
Gel txheej polarization yog ib qho ntawm cov kev ua haujlwm zoo tshaj plaws hauv cov txheej txheem ultrafiltration. Los ntawm kev tshuaj xyuas hauv daim ntawv no, peb tuaj yeem pom tias nws tsis yog qhov teeb meem "fouling", tab sis yog qhov tshwm sim los ntawm kev sib xyaw ua ke ntawm kev hloov pauv huab cua, nthuav tawm, thiab kev ua haujlwm. Cov mis lej qhia txog qhov kev sib raug zoo ntawm qhov concentration, flux, thiab huab hwm coj hloov tsis kam; txheej txheem tsim thiab kev ua haujlwm kom zoo tuaj yeem tswj cov gel txheej polarization rau qee yam; rau cov tshuab polymer, qhov kev xaiv zoo ntawm kev ua haujlwm yog qhov tseem ceeb kom ntseeg tau tias ultrafiltration efficiency. Hauv kev tsim kho vaj tsev, yog cov qauv thiab cov ntsiab lus hauv daim ntawv no tau ua ke nrog kev saib xyuas tsis zoo xws li Jw, k, Di, thiab gel, kev ua haujlwm ruaj khov thiab muaj txiaj ntsig ntawm ultrafiltration system tuaj yeem ua tiav.