Method and device for cross flow filtration

FOUI-reSlSWti

recover air pollutants

membranes

to the atmosphere

An associate professor

use of materials such as paint

of

solvents and cleaning solutions.

material science and engin-

The activated carbon fibre

eering and her research team at the Massachusetts ofTechnology

cloth is said to have almost

Institute

(MIT),

twice the adsorption

Cam-

bridge, Massachusetts,

low concentrations

paring membranes

woven structure

for waste-

the adsorbent

that makes

electrically

them resistant to fouling. Filtration

membranes

capacity

of activated carbon granules at

USA,

has developed a way of prewater treatment

emitted

through the

to be pliable and

conductive

electrothermal

are

and has a that allows for

desorption.

usually made by a process

Electricity

called immersion

carbon cloth causing heating,

Unfortunately,

precipitation.

while allowing for efficient

this process

leaves a relatively

flows through the

recovery

small num-

and reuse of the cap-

tured pollutants.

ber of pores on the membrane

According

surface. Also, the materials

to researchers,

used tend to be hydro-

the vapour recovery

phobic.Therefore,

oil or

could be used to control the

protein containing

solutions

can easily clog or foul them.

system

emissions from large paint The presence

of these groups

made of different materials

in

booths. The exhaust from the

While there are existing mem-

on the surfaces exposed to the

the hope of further adapting

brane treatments

wastewater

their approach to other mem-

an adsorption

number of cylindrical

that reduce

helps the mem-

booth would be blown through bed containing

fouling, they may add expen-

brane resist fouling. Add-

brane chemistries.

sive steps to the pro-duction

itionally, the comb-containing

of their research is to tether

ridges of activated-carbon

process and aren’t always

membranes

chelating agents to the comb

cloth to capture the solvent

effective.

ber of pores on the surface,

bristles to trap heavy metals

molecules.

increasing the amount of

from effluent.

solvent, an electric

The new approach involves

have a larger num-

mixing into the bulk polymer

solution that can be passed

solution a comb polymer,

through the membrane.

which is composed

membranes

hydrophobic

of a

backbone

with short hydrophilic When the membrane

lined bristles. is cast

The

are also self-

One avenue

air pmllutlon process A device for capturing and

caustic solution,

recovering

containing

a comb-

membrane

can be

To release the current

rapidly heats it. The solvent then boils off, condenses

on

the inside of the chamber and

dilute volatile

organic compounds

drains into a collection

(VOCs)

for recovery

vessel

and reuse.

the different water afhnities of

heated to approximately

90 OC

and other hazardous air pol-

the comb and bulk polymers

in water to re-segregate

excess

lutants has been developed by

can be regenerated

cause the combs to segregate

combs from the bulk, and

scientists

times without degradation

to the membrane

therby re-line the damaged

Illinois, USA.

the membrane hydrophilic hydrophilic

surface. Thus

ends up with a

outer surface and a lining on its

internal membrane

channels.

Flltrtion+Separathm

surfaces with hydrophilic material. The research team is now working on comb backbones

at the University

fibre

passes through the fabric and

High-vdume,

healing, i.e. if damaged by a

a

car-

of

The carbon cloth cartridges over 100 to

the cloth.

The new vapour-recovery

Currently

the system exists

system uses activated carbon

as a bench-scale

fibre cloth and electrical

development

en-

ergy to collect and efficiently

device, but the

of industrial-

sized units is planned.

JanuaryiFabmary2OOll5