# US 6,464,881 B2 · Inorganic nanofiltration membrane and its application in the sugar industry

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- Number: US 6,464,881 B2
- Document ID: US6464881B2
- Status: Granted
- Kind: B2
- Application number: 09/739,986
- Filed: 2000-12-19
- Published: 2001-05-24
- Granted: 2002-10-15
- Earliest claimed: 1996-10-21
- Assignees: Orelis
- Inventors: Valérie Thoraval
- Web page: https://patentgrep.com/patent/US6464881B2

## CPC

- C13B 20/165: {using membranes, e.g. osmosis, ultrafiltration (electrodialysis C13B20/18)}
- B01D 61/027: {Nanofiltration}
- B01D 67/00411: {by sintering}
- B01D 67/0048: {by sol-gel transition}
- B01D 67/0088: {Physical treatment with compounds, e.g. swelling, coating or impregnation}
- B01D 69/108: {Inorganic support material}
- B01D 71/024: {Oxides}
- B01D 2325/0283: Pore size
- B01D 2325/04: Characteristic thickness
- B01D 2325/22: Thermal or heat-resistance properties
- B01D 2325/24: Mechanical properties, e.g. strength
- B01D 2325/30: Chemical resistance
- C13B: PRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR (chemically synthesised sugars or sugar derivatives C07H; fermentation or enzyme-using processes for preparing compounds containing saccharide radicals C12P19/00)
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)

## Abstract

The invention concerns an inorganic nanofiltration membrane with a detachment threshold between 100 and 200 daltons and comprising: a multichannel ceramic monolith support consisting of a mixture of Al2O3 and of TiO2, a microfiltration membrane separating layer, an ultrafiltration membrane separating layer, preferably consisting of ZrO2, a nanofiltration membrane separating layer, preferably consisting of ZrO2, and obtained by a sol-gel type method. This inorganic nanofiltration membrane is designed for use in the sugar industry, more particularly for treating saline effluents derived from the regeneration of ion exchanging resins used if the refining of cane sugar.

## Claims

### Claim 1

An inorganic nanofiltration membrane comprising:
a multichannel monolithic ceramic support consisting essentially of a mixture of Al2O3 and of TiO2 and exhibiting a mean equivalent pore diameter Ds of between 1 and 20 μm,
a microfiltration membrane separating layer situated at the surface of the channels and consisting essentially of sintered particles of metal oxide(s), whose mean equivalent pore diameter Do before sintering is between 0.1 and 3.0 μm, according to a Ds/Do ratio such that 0.3<Ds/Do<200, the said microfiltration membrane layer exhibiting a mean equivalent pore diameter Dm of between 0.05 and 1.5 μm,
an ultrafiltration membrane separating layer situated on said microfiltration membrane layer and consisting essentially of sintered particles of metal oxide(s),whose mean equivalent pore diameter Du before sintering is between 2 and 100 nm, according to a Dm/Du ratio such that 0.5<Dm/Du<750, and
a nanofiltration membrane separating layer situated on said ultrafiltration membrane layer and composed of sintered particles of metal oxide(s), whose mean equivalent pore diameter Dn before sintering is between 0.5 and 1.5 nm,
said inorganic nanofiltration membrane exhibiting a cutoff threshold of between 100 and 2000 daltons.

### Claim 2 (depends on 1)

A membrane according to claim 1, wherein said monolithic support exhibits a porosity greater than 30%.

### Claim 3 (depends on 1)

A membrane according to claim 1, wherein said monolithic support is a ceramic of Al2O3 grains coated at least in part with TiO2 grains, and having a TiO2/(Al2O3+TiO2) ratio by weight between 1 and 75%.

### Claim 4 (depends on 1)

A membrane according to claim 1, wherein the metal oxide(s) of the microfiltration membrane layer is (are) alumina, zirconia or titanium oxide.

### Claim 5 (depends on 1)

A membrane according to claim 1, wherein the metal oxide(s) of the ultrafiltration membrane layer is (are) titanium oxide or zirconia.

### Claim 6 (depends on 5)

A membrane according to claim 5, wherein the metal oxide of the ultrafiltration membrane layer is zirconia, said layer exhibiting a cutoff threshold of between 10 and 300 kD.

### Claim 7 (depends on 1)

A membrane according to claim 1, wherein the nanofiltration membrane layer is zirconia.

### Claim 8 (depends on 1)

A membrane according to claim 1, wherein the nanofiltration membrane layer is made by the sol-gel process comprising a hydrolysis in an alcoholic medium.

### Claim 9 (depends on 8)

A membrane according to claim 8, wherein the nanofiltration membrane layer is a zirconia layer made by the sol-gel process of:
a) preparing a sol by hydrolysis in an alcoholic medium of a zirconium alkoxide precursor, in the presence of a complexing ligand;
b) depositing the sol on the ultrafiltration membrane layer, by bringing the ultrafiltration membrane layer and the sol obtained in above step a), into contact by filling the channels, to which sol has been added beforehand an organic binder;
c) converting the sol into a gel by drying; and
d) carrying out a heat treatment on the gel prepared in step c) to obtain the nanofiltration membrane layer.

### Claim 10 (depends on 1)

A process for the treatment of saline effluents resulting from the regeneration of the ion-exchange resins employed in the refining of cane sugar comprising the step of filtering said effluents with a membrane as defined in claim 1.