rexresearch.com
Chaitanya KARAMCHEDU
Desalination
http://www.kptv.com/story/34415847/portland-teen-discovers-cost-effective-way-to-turn-salt-water-into-drinkable-fresh-water
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 his findings.

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," said Karamchedu.

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 research.

"They were very encouraging, they could see things into it that I couldn't, because they've been working their whole lives on this," said Karamchedu.

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 cancer.

"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 seniors.



http://sites.ieee.org/sustech/files/2016/10/CK_desalination-abstract.pdf
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
chaitanya.dasharathi@gmail.com

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 approximately 30%.

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 used.

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 high yield.

https://www.ars.usda.gov/research/publications/publication/?seqNo115=140994
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 monomers.


US2015352520
COMPOUNDED SURFACE TREATED CARBOXYALKYLATED STARCH POLYCRYLATE COMPOSITES

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 treatment.


US4116899
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.

 
US4400496
Water-soluble graft copolymers of starch-acrylamide and uses therefor  

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 ##STR3##

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 1 minute.

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 limits.

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.

EXAMPLE 1

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 homogeneous.

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.

EXAMPLE 2

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.

http://onlinelibrary.wiley.com/doi/10.1002/star.201100077/full
DOI: 10.1002/star.201100077
Starch, Volume 64, Issue 3, March 2012, Pages 207–218
Synthesis, characterization and swelling behaviour of superabsorbent polymers from cassava starch‐graft‐poly (acrylamide)
PC Parvathy, AN Jyothi
Abstract
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.


http://onlinelibrary.wiley.com/doi/10.1002/1521-379X(200107)53:7%3C311::AID-STAR311%3E3.0.CO;2-A/full
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

Abstract
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 kJ/mol.