Portland teen discovers cost-effective way
to turn salt water into drinkable fresh water
By Kaitlyn Bolduc
A Portland teen is turning heads across the country all because of
a science experiment that began in his high school classroom.
Companies like Intel and universities like MIT are now invested in
With certainty you'll want to remember his name.
"My name is Chaitanya Karamchedu, but you can call me Chai," said
the Jesuit High School Senior.
Karamchedu has big plans of changing the world.
"1 in 8 people do not have access to clean water, it's a crying
issue that needs to be addressed," said Karamchedu.
He made up his mind to address the matter himself.
"The best access for water is the sea, so 70 percent of the planet
is covered in water and almost all of that is the ocean, but the
problem is that's salt water," said Karamchedu.
Isolating drinkable water from the ocean in a cost effective way
is a problem that's stumped scientists for years.
"Scientists looked at desalination, but it's all still
inaccessible to places and it would cost too much to implement on
a large scale," Karamchedu added.
Karamchedu figured it out, on his own, in a high school lab.
"The real genesis of the idea was realizing that sea water is not
fully saturated with salt," Karamchedu said.
By experimenting with a highly absorbent polymer, the teen
discovered a cost effective way to remove salt from ocean water
and turn it into fresh water.
"It's not bonding with water molecules, it's bonding to the salt,"
It's his creativity that makes this a big deal.
"People have been looking at the problem from one view point, how
do we break those bonds between salt and the water? Chai came in
and thought about it from a completely different angle," said
Jesuit High School Biology Teacher Dr. Lara Shamieh.
"People were concentrated on that 10 percent of water that's
bonded to the salt in the sea and no one looked at the 90 percent
that was free. Chai just looked at it and said if 10 percent is
bonded and 90 percent is free, then why are we so focused on this
10 percent, let's ignore it and focus on the 90."
It's a breakthrough that's estimated to impact millions of lives
if ever implemented on a mass scale.
"What this is compared to current techniques, is that it's cheap
and accessible to everyone, everyone can use it," said Shamieh.
Scientists across the country are taking note. He won a $10,000
award from the US Agency for International Global Development at
Intel's International Science Fair and second place at MIT's
TechCon Conference where he won more money to continue his
"They were very encouraging, they could see things into it that I
couldn't, because they've been working their whole lives on this,"
A contribution to science that's sure to make a difference. Though
he's not done yet.
"Now, he's working on at least mentally thinking about the idea of
killing cancer cells from the inside out. I keep telling him to
remember his high school biology teacher when he wins the Nobel
prize," said Shamieh.
"Some problems seem like impossible problems, but to call them
impossible problems is a self-fulfilling prophecy. The more you
think about it as impossible, the more impossible it becomes
sometimes," said Karamchedu.
A line of thinking, by one gifted teen, that just might cure
"I can really see beauty in things that aren't immediately
applicable, and at the same time I want to do something to make a
difference that's not completely in the abstract. It's important
what you do has an impact on people," Karamchedu added.
Back in January, Karamchedu was also named one of 300 Regeneron
Science Talent Search Semifinalists. The STS is thought to be one
of the most prestigious competitions in nation for high school
Addressing global water scarcity with a
novel hydrogel based desalination technique using saponified
starch grafted polyacrylamide's hydrophilic properties to
harvest fresh water with a low energy and chemical footprint
Chaitanya Karamchedu, Student Member, IEEE
Jesuit High School/Portland State University
WATER scarcity is a global crisis affecting over a billion people;
it creates environmental and social stress. Desalination is a
promising approach to address this crisis. With approximately 97%
of the water on Earth represented by oceans, the prospect of
extracting arable or potable water from seawater has the potential
to impact millions of lives, particularly along the world’s
coasts. Current approaches are still expensive, both in monetary
and energy terms; and remain out of reach for many countries. They
rely on thermal, membrane, or hybrid approaches to desalinate
water and impose high energy and environmental costs. Yet,
seawater is on average only 3% - 4% by weight salt and other
dissolved solids, while the maximum solubility of salt in water is
Consequently, nearly 90% of seawater is water that is not bonded
with salt and potentially available for harvesting. The primary
question that motivates this investigation is - whether it is
possible to harvest this remaining 90% of seawater using
superabsorbent hydrophilic polymers, with no external energy,
under room temperature and pressure and produce drinkable water
within WHO’s guidance for safe drinking water. This study
harvested fresh water from seawater using saponified
starch-grafted-polyacrylamide’s hydrophilic properties. This
required a) the creation of a hydrogel to separate freshwater from
seawater, b) the separation of the hydrogel from the brine, c) the
dewatering of the gel resulting in aqueous sulfuric acid and d)
the recovery of fresh water from the aqueous solution. The results
of the investigation were promising. The study demonstrated that:
1. It is possible to use such hydrophilic polymers to desalinate
water without thermal or electrical energy. Water that was not
bonded with salt, bonded with the starch grafted polyacrylamide to
form a hydrogel, effectively isolating it from the salt water.
2. The extracted water’s conductivity was comparable to fresh
water indicating that the salts have been separated. The average
conductivity of the resulting water was 306.32 µS/cm, comparable
to the conductivity of 200 µS/cm for the reference distilled water
3. That this approach has promise in mitigating desalination
pre-treatment and post-treatment problems. Mass and conductivity
analysis confirmed that the extracted water had a total dissolved
solids concentration of 513 mg/L, (WHO guidance is <600 mg/L)
compared to 35,000 mg/L for seawater. The concentration of sodium
in the extracted water was 25.8 mg/L (compared to 10,500 mg/L for
seawater) and that of chloride was 36 mg/L (compared to 19,000
mg/L for seawater). The corresponding EPA secondary concentration
levels (aesthetic standards) for sodium is 20 mg/L and for
chloride is 250 mg/L.
The process required no external energy – a significant
improvement over current energy dependent techniques; fresh
drinkable water yield was over 70% and produced a commercially
useful fertilizer, CaSO 4 , as a byproduct. Another significant
promise of this approach is that it appears amenable to small
scale use. Sustainable and accessible means for desalination have
potential to improve millions of lives; the implementation of the
proposed hydrogel based desalination technique may be able to
address this need with very low infrastructure investments and a
Polymer Engineering & Science. 43(10):1666-1674.
PREPARATION OF STARCH-GRAFT-POLYACRYLAMIDE
COPOLYMERS BY REACTIVE EXTRUSION)
Willett, Julious / Finkenstadt, Victoria
Interpretive Summary: Starch, a renewable resource derived
from corn and other grains, often requires chemical modification
to provide specific properties desired for end-use applications.
These processes often use large quantities of water and generate
significant amounts of by-products. New processes for modifying
starch which use less water and reduce environmental impact are
desirable. One promising method, known as reactive extrusion, is a
continuous process using equipment similar to that used for
production of puffed food products. We have demonstrated that
reactive extrusion can be used to modify starch and other natural
materials in a rapid and continuous manner. This process can be
used to prepare modified starches with a wide range of properties,
while decreasing water use by half or more. Application of this
technology may reduce the cost of producing modified starches and
lead to new materials based on starch, in addition to reducing the
environmental impact of starch processing.
Technical Abstract: Graft copolymers of starch and
polyacrylamide (PAAm) were prepared by reactive extrusion using a
co-rotating twin screw extruder and ammonium persulfate initiator.
Feed rates were 109 g/min to 325 g/min (all components) at a
moisture content of 50%, with screw speeds in the range 100 rpm to
300 rpm. Starch/acrylamide weight ratios ranged from 5:1 to 1.3:1.
Conversions of acrylamide to PAAm were generally 80% or greater
with residence times of 400 seconds or less. Conversion was
independent of residence time, and increased with feed rate,
suggesting that reaction efficiency was proportional to the degree
of fill in the extruder. Grafting efficiencies were in the range
of 50% to 80%. Grafting efficiencies were lower for waxy maize
starch than for normal corn starch. Extractable fractions in 30/70
ethanol-water solvent were approximately 10% to 15%, of which 25%
to 70% was polyacrylamide. Soluble PAAm increased with decreasing
starch/acrylamide ratio. PAAm molecular weight increased with
increasing acrylamide content, consistent with free radical
polymerization kinetics. Extrusion temperature had no significant
impact on acrylamide conversion, while PAAm molecular weights did
not show the expected decrease with increasing temperature. Graft
frequency, as measured by the number of anhydroglucose units per
graft, were essentially constant over the starch:acrylamide ratio
and temperature range studied. At a starch:acrylamide ratio of
5:1, graft frequency decreased with increasing screw speed, giving
materials with fewer grafts of lower molecular weight. These
results show that reactive extrusion offers the potential for
rapid production of starch graft copolymers with unsaturated
COMPOUNDED SURFACE TREATED CARBOXYALKYLATED STARCH
Inventor(s): SUAREZ-HERNANDEZ OSCAR, et al.
A dual-surface treated composite superabsorbent particle
comprising a polycarboxylate polymer (e.g., saponified
polyacrylamide) and a carboxylated starch polymer is disclosed.
The surface of the particle is cross linked through esterification
with a C2-C4 polyol exemplified with glycerol. In addition, the
surface region is crosslinked through ionic bonds with a trivalent
metal ion exemplified with aluminum. In a critical method of
making, the acidification of the surface with the polyol occurs
prior to treatment with the trivalent metal ion, which results is
a hybrid particle that can include up to about 40% of
carboxymethyl starch yet exhibit a FSC of at least 47 g/g, a CRC
of at least 27 g/g, an AUL of at least 18 g/g under a load of 0.7
psi, and a SFR of at least 180 ml/min. Also disclosed is a method
of making that includes a surface esterification prior to aluminum
Increasing absorbency of polymeric compositions by curing
Inventor(s): FANTA GEORGE, et al.
Absorbent polymeric compositions are prepared by drying aqueous
dispersions of physical mixtures of polyhydroxy polymers, such as
starch, with carboxylate-containing synthetic polymers, such as
saponified polyacrylonitrile of partially saponified
polyacrylamide, and then curing the resulting dry solids with
either heat or prolonged standing at room temperature. These
compositions typically absorb several hundred times their weight
of deionized water.
Water-soluble graft copolymers of starch-acrylamide and uses
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the invention, there is provided a high
molecular weight graft copolymer containing starch as the backbone
and polyacrylamide or poly(acrylamide-acrylic acid) as grafted
side chains. Starch is derived from such crops as corn, wheat,
yams, or potatoes. It is a white, tasteless, odorless, granular
solid and is classed chemically as a complex carbohydrate. Certain
natural starches and certain fractions of starch are soluble in
water. It is this class of materials, those capable of forming
aqueous solutions, that are employed in this invention. The
macromolecule of the water soluble starch is composed of glucose
units joined .alpha.-1,4'. The repeating unit of the chemical
formula of water soluble starch is: ##STR1## To this starch
macromolecule is grafted repeating units of acrylamide ##STR2##
alone or in combination with repeating units of acrylic acid
The preparation of this copolymer is accomplished in general under
oxygen-free conditions by adding acrylamide to an aqueous starch
solution followed by the addition of a polymerization initiator
and allowing time for graft polymerization to occur. When acrylic
acid units are desired a previously prepared graft copolymer of
starch-acrylamide is subjected to hydrolysis conditions capable of
converting some of the amide units to carboxylic acid units.
To a container of appropriate size containing a mechanical stirrer
and inert gas inlet is added between 2 and 75 parts by weight of
starch per 1000 parts distilled or deionized water. The mixture is
heated to 85 DEG-95 DEG C. with stirring, to dissolve the starch.
Certain fractions or types of starch require heating to
temperatures as high as 150 DEG C. under pressures as high as 15
psig to dissolve the starch in water. If such a starch is used,
these temperature and pressure conditions should be applied for at
least 30 minutes. After dissolution, the mixture is allowed to
cool to 25 DEG C. while being stirred and bubbled with an inert
gas such as nitrogen, helium, neon, argon, krypton, or xenon.
Between 5 and 400 parts, preferably between 70 and 225 parts, by
weight of acrylamide are added to the reaction mixture per 1000
parts water. The system is then deoxygenated for about 30 minutes
by bubbling with an inert gas. Certain impurities present in
commerically-available acrylamide may inhibit or prevent the
copolymerization, and it is therefore preferred that acrylamide be
used that has been freshly recrystallized from trichloromethane
and vacuum dried.
The preferred polymerization initiator is ceric ion (Ce@+4). Other
initiators that may be used include vanadium (V@+5) or manganese
ions (Mn@+3, Mn@+4, Mn@+7). It is preferred that the physical form
of the initiator be an acidic aqueous solution. Preferably the
initiator is a 0.001 to 0.1 molar aqueous solution of ceric
ammonium nitrate, Ce(NH4)2 (NO3)6, in 0.001 to 1.0 molar nitric
acid. Other acid soluble cerium salts, however, can be used.
Between 0.01 and 7 parts of this ceric ion initiator solution is
added to the above reaction mixture and the mixture is stirred for
The graft copolymerization reaction can be conducted with or
without stirring once the initiator has been dispersed in the
reaction mixture. The reaction is allowed to proceed for 1 to 200
hours, with 48 hours being a typical reaction time. It is
preferred to terminate the copolymerization by addition of a free
radical scavenger such as hydroquinone.
If it is preferred to form poly(acrylamide-acrylic acid)-starch
graft copolymer by replacing a fraction of the acrylamide in the
above procedure with acrylic acid, it is best accomplished by
hydrolyzing some of the amide groups of the polyacrylamide-starch
graft copolymer, preferably with a base, such a sodium hydroxide
or with acid, such as nitrous acid.
The graft copolymer is easily recovered from a liquid reaction
mixture. If the reaction mixture is a gel it can be made pourable
by mixing with 5 to 8 times its volume of distilled or deionized
water under low shear conditions until a homogeneous, pourable
system is formed. The reaction mixture is added to 2-50,
preferably 5-30, times its volume of a nonsolvent for the
copolymer, such as acetone. Preferably the nonsolvent is stirred
vigorously so as to form a vortex and the copolymer solution is
slowly drained directly into the center of this vortex. The
precipitated graft copolymer is then removed from the nonsolvent
solution by filtration, washed with nonsolvent, filtered, and
vacuum-dried to a constant weight.
The amount of all save one of the components of the reaction
mixture can be varied within reasonable limits of those given in
this description. The acrylamide concentration of the reaction
mixture should remain between 5 parts and 400 parts, preferably 70
to 225 parts per 1000 parts by weight of reaction medium.
Copolymers having the high molecular weight needed for efficient
water viscosification in oil recovery may not be formed in
reaction mixtures with acrylamide concentrations beyond these
The following examples illustrate certain embodiments of this
invention wherein parts and percentages are by weight and
temperatures are in centigrade unless otherwise indicated. Pfaltz
and Bauer starch, catalog number SO8583, and Eastman reagent-grade
acrylamide were used in these syntheses.
A 50 ml. Erlenmeyer flask containing 25 ml. of deionized,
distilled water and 0.336 g of starch was heated to 95 DEG C. and
stirred for 30 minutes. The flask was allowed to cool to 25 DEG C.
and 2.91 g of recrystallized and vacuum dried acrylamide and 15
ml. of deionized, distilled water were added. The system was
sparged with argon for 30 minutes and capped with a serum cap. The
initiator solution was made by dissolving 1.3703 g of ceric
ammonium nitrate in 20 ml of 1 molar nitric acid contained in a 25
ml volumetric flask. The flask was then filled to its volume mark
with 1 molar nitric acid to form a 0.0999 molar solution of ceric
ion, Ce@+4, in 1 molar nitric acid. Using a syringe, 0.041 ml of
the initiator solution was injected into the reaction mixture and
the mixture was stirred for 1 minute. The flask was placed in a
constant temperature bath held at 30 DEG C. and allowed to react
for 48 hours. The reaction mixture was stirred for one minute
every one-half hour until the mixture became too viscous to stir.
The addition of 0.5 ml of deionized water saturated with
hydroquinone terminated the reaction. The reaction mixture was
mixed with 250 ml of deionized water until the system was
Dropwise addition of 250 ml. of acetone to the dilute, viscous
solution of copolymer caused the solution to become cloudy and
nonviscous. The mixture was then slowly poured into 2.5 liters of
acetone to precipitate the copolymer. The white, fibrous copolymer
was removed from the acetone by filtration, washed with 200 ml. of
acetone, and placed in a high speed, Waring laboratory blender
with 300 ml. of acetone. The mixture was beaten for 3 seconds to
pulverize the copolymer and the resulting slurry was filtered. The
copolymer was dried under vacuum at room temperature. The product
was 3.02 g of a copolymer of acrylamide grafted to starch and
having an intrinsic viscosity of 10.6 dl/g.
To a 50 ml Erlenmeyer flask was added 25 ml of distilled,
deionized water and 1.00028 g of starch. The flask and contents
were heated to 80 DEG C. and stirred for 30 minutes. When the
flask and contents had cooled to 25 DEG C., 4.27 g of acrylamide
and 15 ml of distilled, deionized water were added. Argon was
bubbled through the solution for 30 minutes before the flask was
capped and 0.051 ml of the ceric ammonium nitrate solution,
prepared as in Example 1, was added. The solution was stirred for
one minute, and placed in a controlled temperature bath at 30 DEG
C. The sample was removed from the bath every 15 minutes and the
reaction mixture stirred for one minute. After 45 minutes, the
mixture was too viscous to stir and the sample was left
undisturbed for another 71.25 hours. The reaction was terminated
by the addition of 0.5 ml of water saturated with hydroquinone and
the reaction mixture was placed in 300 ml of deionized water and
stirred slowly for 3 days. A total of 230 ml of acetone was added
dropwise to form a cloudy, nonviscous dispersion of copolymer in
acetone and water. The dispersion was slowly added to 1.5 liters
of vigorously stirred acetone. The precipitated copolymer was
revovered from the acetone by filtration, placed in a covered
beaker, and dried to constant weight under vacuum at 25 DEG C. The
product was 5.3 g of a copolymer of acrylamide grafted to starch
and having an intrinsic viscosity of 12.4 dl/g.
Starch, Volume 64, Issue 3, March 2012, Pages 207–218
Synthesis, characterization and swelling
behaviour of superabsorbent polymers from cassava
PC Parvathy, AN Jyothi
Superabsorbent polymers (SAPs) were prepared from cassava starch
by graft copolymerization of acrylamide on to starch using ceric
ammonium nitrate (CAN) as free radical initiator, followed by
alkali saponification. The reaction parameters such as
concentration of acrylamide, concentration of CAN, temperature,
and duration of polymerization reaction were optimized for maximum
water absorbency using a 4-factor 3-level Box-Behnken design. The
highest values of percentage grafting and absorbency obtained were
174.8% and 425.2 g/g, respectively. The polymers were
characterized by determination of grafting efficiency, N-content,
acrylamide content, FTIR analysis, SEM and XRD analyses.
Thermogravimetric analysis (TG) showed that the SAP has higher
thermal stability. The rate of water absorbency and the swelling
behaviour of the SAP under different conditions of pH, and
different salts were determined. The de-swelling pattern of the
hydrogels over different time durations was also determined.
Starch, Volume 53, Issue 7, July 2001, Pages 311–316
Grafting of 2-(Dimethylamino)ethyl
Methacrylate onto Potato Starch Using Potassium
Permanganate/Sulfuric Acid Initiation System
Li-Ming Zhang, Dan-Qing Chen
Graft copolymerization of 2-(dimethylamino)ethyl methacrylate onto
potato starch was carried out in an aqueous medium using a
potassium permanganate/sulfuric acid initiation system. The
grafting percentage and grafting efficiency were determined as
functions of the concentrations of potassium permanganate,
sulfuric acid and the monomer, and also polymerization temperature
and time. The IR spectrum of the graft copolymer showed the peaks
characteristic of the grafted chains. The grafting percentage and
grafting efficiency increased and then decreased with increasing
the concentrations of potassium permanganate, sulfuric acid, and
the monomer, as well as polymerization temperature. The grafting
reaction was characterized by an initial fast rate followed a
lower rate which leveled off after a certain time. The overall
activation energy for the grafting was estimated to be 66.9
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