Chemical Engineering August 2021 - 5

Chementator
Anti-biofouling coating for desalination
membranes extends lifetimes
B
uildup of biofouling on
membranal surfaces
necessitates treatments
with corrosive chemicals,
such as hydrochloric acid,
and even replacement of membrane
cartridges, which can be
costly in desalination operations.
A new coating, developed in the
laboratory of Ran Suckevereine
at
Membrane
Magnifi cation
Biofouled
Filter layer
Clean
water out
Support
layer
Antimicrobial
polyaniiline coating
Contaminated
water out
Kinneret Academic College
(Gallilee, Israel; www.kinneret.
ac.il), is capable of preventing
microbial growth on surfaces of
commercially available desalinaPolyaniline
functionalized
membrane
Dr.
Ran Suckevereine
tion membranes, while maintaining the flowrate and salt
rejection observed with the untreated membrane.
The use of coatings to prevent biofouling on membranes
has been previously tried, but " coating materials
can wash into the treated water if they are not strongly
attached, " explains Suckevereine. " Free-radical mechanisms
can be used to attach active polymers to the
membrane, but without special considerations, the free
radicals may damage the membrane. "
The group's approach overcomes a number of these
issues. The coating is made from polyaniline that is polymerized
in the presence of the membrane in such a
way that it is chemically bound to the membrane. The
Kinneret team used a unique polymerization technique,
known as inverse emulsion polymerization, along with
Water
in
Membrane
wrap
Magnifi cation
Filler
layer
Support
layer
Polyaniline coated
membrane showed
no colonies at all
Reference membrane
exhibited large colony
Standard colonies
counting technique
Standard colonies
counting technique
Edited by:
Gerald Ondrey
sonication, to allow the polymerization
to proceed at faster rates,
and to allow the polyaniline binding
to occur without damaging
the membrane.
Inverse emulsion polymerization
involves a large organic
phase
containing
the
aniline
monomer, and smaller aqueous
phase containing free-radical
initiators. Applying ultrasonic
soundwaves with a sonicator
creates tiny droplets of water
within the organic phase, and
the polymerization occurs at the
water-solvent interphase.
With the small droplets, " there are lots of reaction
sites, which increases the rate and yield of the polymerization, "
says Suckevereine. Also, the sonication
creates free radicals, which allow the binding to the
membrane. Since the membrane is present within the
inverse emulsion, a thin (~80 nm) layer of polymer forms
on the membrane surface.
In tests with E. coli bacteria and water from the Sea
of Gallilee, Suckervereine's group found that the coating
prevents microbial growth (photo), and allows the
same flowrate and degree of salt rejection as untreated
membrane. The team has scaled up the process beyond
laboratory scale, but is currently working on another
scaleup to a cubic-meter-sized reactor.
Recovering carbon black from waste tires
U
ntil now, waste tires have been
used mainly for recovering energy.
Only small proportions of the carbon
black contained in these tires
are recycled, since the mineral ash generated
by pyrolysis consists of about 20 wt.%
of additives used to make the tires. A new
process developed by the Fraunhofer Institute
for Building Physics (IBP; Valley, Germany;
www.ibp.fraunhofer.de) is able to
isolate almost all of this ash, allowing both
the carbon black and the minerals from
the ash to be reused. The process was
developed on behalf of RCB Nanotechnologies
GmbH (Munich, Germany; www.
recovered-carbon-black.com).
To purify the carbon-black/ash mixture
created during the pyrolysis process,
a wet chemical method is used.
The (raw) carbon-black/ash mixture, together
with various additives and a liquid,
are blended in a reactor, and taken
through a defined pressure and temperature
curve. The parameters and additives
are adjusted in such a way that only one
particular mineral is selectively extracted
from the mixture at a time. This demineralization
process produces high-purity,
recycled carbon black for use in tires and
other rubber products, as well as colorants
(masterbatch) for plastic applications,
silicates, which can be used in the
building materials industry or for dyes, for
example, and also zinc salts for a broad
range of applications.
A 200-L pilot plant will operate for the
next two years at Fraunhofer IBP, aiming
to make recovered carbon black usable for
other industrial applications besides tires.
The basic process has already been patented,
and RCB Nanotechnologies GmbH
is the exclusive licensee. The company is
currently working on scaling up the process
and the production hall is already
built. The reactor volume for one production
line is expected to be around 4,000
L, which will produce 400 kg/h of recycled
carbon black from the ash, or 2,500 ton/yr.
In the final expansion stage, the plant will
have a capacity of 30,000 ton/yr.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
AUGUST 2021
TOXICOLOGY TESTING
The world's first toxicologytesting
strategy without animal
testing has been approved by
the Organization for Economic
Co-operation and Development
(OECD; Paris, France; www.
oecd.org). The testing strategy
consists of three so-called alternative
methods. They can be
used to predict whether a substance
causes allergic reactions
in the skin. Unlike in the past,
animal testing will no longer be
necessary for this.
This testing strategy was developed
and validated in a joint
effort by BASF SE (Ludwigshafen,
Germany; www.basf.
com) and Givaudan (Vernier,
Switzerland; www.givaudan.
com). " For more than 10
years, we have been working
towards this goal, " says Robert
Landsiedel, vice president,
Special Toxicology, BASF. " We
have taken a big step forward.
Now we can also use alterna(Continues
on p. 6)
5
Reverse osmosis
setup
In situ aniline
Polymerization
http://www.kinneret http://www.ac.il http://www.oecd.org http://www.ibp.fraunhofer.de http://www.basf http://www.recovered-carbon-black.com http://www.givaudan http://WWW.CHEMENGONLINE.COM
Chemical Engineering August 2021

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