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1768 East 25 th Street Suite 301 Cleveland, OH 44114 216.367.0602 egeneration.org Molten Salt Reactors: Manufacturing a Better Human Condition How Molten Salt Reactors can assist traditionally resourcestarved countries in creating a better human condition. Let’s feed the world, provide water, power and fuel Authored By: Jon Paul Morrow eGeneration Fellow

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1768  East  25th  Street  Suite  301  Cleveland,  OH  44114  216.367.0602  

egeneration.org  

Molten Salt Reactors: Manufacturing a Better Human Condition How  Molten  Salt  Reactors  can  assist  traditionally  resource-­‐starved  countries  in  creating  a  better  human  condition.  Let’s  feed  the  world,  provide  water,  power  and    fuel  

Authored  By:  Jon  Paul  Morrow    eGeneration  Fellow    

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TABLE OF CONTENTS

Executive  Summary  ............................................................................................................................................................  1  

Introduction  ...........................................................................................................................................................................  1  

Functionalized  Polymers  in  Agriculture  ...................................................................................................................  2  

Super  absorbents  polymers  and  composites  for  agriculture  ...........................................................................  2  

Water  -­‐  insoluble  polymers  ............................................................................................................................................  4  

Polymers  for  soil  remediation  .......................................................................................................................................  5  

How  Agricultural  Hydrogels  are  Made  and  How  MSRs  can  help  ....................................................................  6  

Conclusions  ............................................................................................................................................................................  7  

 

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EXECUTIVE SUMMARY

The  use  of  super  absorbent  polymers,  the  material  used  in  baby  diapers  to  make  them  super  absorbent,  is  gaining  popularity  in  agriculture.  These  polymers  have  provided  solutions  to  present  day  agricultural  problems  to  maximize  land  and  water  productivity  without  threatening  the  environment  and  the  natural  resources.  Superabsorbent  polymer  hydrogels  positively  influence  soil  permeability,  density,  structure,  texture,  evaporation,  and  infiltration  rates  of  water  through  the  soils.    

Function  specific  polymers  are  already  used  to  increase  the  efficiency  of  pesticides  and  herbicides,  allowing  lower  doses  to  be  used  and  to  indirectly  protect  the  environment  by  reducing  pollution  and  cleanup  existing  pollutants.    

INTRODUCTION

The  World’s  population  is  increasing  at  an  alarming  rate  and  is  expected  to  reach  seven  billion  by  the  end  of  year  2050  and  nine  billion  by  2100.  Population  growth  and  the  inevitable  development  of  large  high-­‐density  urban  populations,  in  parallel  with  global  industrialization  of  third  world  countries  reaching  for  first  world  status,  and  increasing  use  of  croplands  being  committed  to  raising  crops  destined  for  energy  production,  have  placed  major  pressures  on  our  environment,  potentially  threatening  environmental  sustainability  and  food  security.  This  has  resulted  in  the  over  buildup  of  chemical  and  biological  contaminants  throughout  the  biosphere,  but  most  notably  in  soils  and  sediments.    

During  the  20th  century,  the  main  emphasis  of  world-­‐wide  agricultural  development  centered  around  increasing  productivity  per  unit  area  of  land  used  for  crop  production  to  feed  our  ever-­‐increasing  populations.  This  was  substantially  accomplished  through  over-­‐farming  (the  excessive  use  of  fertilizers  and  pesticides)  and  exploitation  of  natural  resources  such  as  water  and  plant  resources.  Although  this  practice  has  resulted  in  considerably  increasing  crop  yields  in  the  short-­‐tem,  it  is  not  sustainable  in  the  long  term  considering  the  expected  population  growth  of  the  world.  The  productive  capacity  of  arable  land  has  been  impaired;  natural  water  resources  have  been  depleted  and  polluted  with  pesticides  and  chemical  fertilizers,  which  threatened  the  sustainability  of  not  just  humans,  but  wild  life  as  well.  Therefore,  the  focus  on  agricultural  development  in  this  century  has  shifted  to  the  sustainable  use  of  land,  water  and  plant  resources.  

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The  major  goals  of  the  agriculture  industry  are  to  maximize  land  and  water  productivity  without  threatening  the  environment  and  the  natural  resources.    

Many  nations  have  experienced  considerable  distress  arising  out  of  drought  occurrences  -­‐mass  starvation  (even  famines),  cessation  of  economic  activity  particularly  within  the  developing  world  where  economies  are  inextricably  and  intrinsically  tied  to  agriculture.    

The  study  of  polymers  has  helped  to  foster  the  emergence  of  agricultural  polymers  through  focus  on  natural/synthetic  macromolecular  substances  such  as  proteins,  polyacrylates,  polyacrylamides,  and  polysaccharides.  Through  the  concerted  efforts  of  polymer  chemists,  a  series  of  commercially  natural/synthetic  polymers  have  been  successfully  used  in  many  applications  in  the  field  of  agriculture.    

 

FUNCTIONALIZED POLYMERS IN AGRICULTURE

Synthetic  polymers  play  important  role  in  agricultural  uses  as  structural  materials  for  creating  a  climate  beneficial  to  plant  growth  e.g.  mulches,  shelters  or  green  houses;  for  fumigation  and  irrigation,  in  transporting  and  controlling  water  distribution.  However,  the  principal  requirement  in  the  polymers  used  in  these  applications  is  concerned  with  their  physical  properties;  such  as  transmission,  stability,  permeability  or  weather-­‐ability;  as  inert  materials  rather  than  as  active  molecules.  During  the  last  few  years,  the  science  and  technology  of  reactive  functionalized  polymers  have  received  considerable  interest  as  one  of  the  most  exciting  areas  of  polymer  chemistry  for  the  production  of  improved  materials.  They  have  found  widespread  applications  as  reactive  materials  based  on  the  potential  advantages  of  the  specific  active  functional  groups  and  the  characteristic  properties  of  the  polymeric  molecules.  Their  successful  utilizations  are  quite  broad  including  a  variety  of  fields,  such  as  solid-­‐phase  synthesis,  biologically  active  systems  and  other  various  technological  uses.    

SUPER ABSORBENTS POLYMERS AND COMPOSITES FOR AGRICULTURE

Polymeric  soil  conditioners  were  known  since  the  1950s.  These  polymers  were  developed  to  improve  the  physical  properties  of  soil  in  view  of:    

v Increasing  their  water-­‐holding  capacity,    v Increasing  water  use  efficiency    

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v Enhancing  soil  permeability  and  infiltration  rates    v Reducing  irrigation  frequency    v Reducing  compaction  tendency    v Stopping  erosion  and  water  run-­‐off    v Increasing  plant  performance  (especially  in  structure  -­‐less  soils  in  areas  subject  to  

drought).    

The  presence  of  water  in  soil  is  essential  to  vegetation.  Liquid  water  ensures  the  feeding  of  plants  with  nutritive  elements,  which  makes  it  possible  for  the  plants  to  obtain  a  better  growth  rate.  It  seems  to  be  interesting  to  exploit  the  existing  water  potential  by  reducing  the  losses  of  water  and  also  ensuring  better  living  conditions  for  vegetation.  Taking  into  account  the  water  imbibing  characteristics  of  Super  Absorbent  Polymers  (SAP)  materials,  the  possibilities  of  their  application  in  the  agricultural  field  has  increasingly  been  investigated  to  alleviate  many  agricultural  problems.  Super  absorbent  polymers  (SAPs)  are  compounds  that  absorb  water  and  swell  to  many  times  their  original  size  and  weight.  They  are  lightly  cross-­‐linked  networks  of  hydrophilic  polymer  chains.  The  network  can  swell  in  water  and  hold  a  large  amount  of  water  while  maintaining  the  physical  dimension  structure.  At  present,  the  material's  biodegradability  is  an  important  focus  of  the  research  in  this  field  because  of  the  renewed  attention  towards  environmental  protection  issues.  The  life  of  SAPs  is  in  general  in  the  range  5  -­‐  7  years,  and  they  typically  degrade  into  ammonium,  carbon  dioxide  and  water.    

SAP  hydrogels  potentially  influence  soil  permeability,  density,  structure,  texture,  evaporation,  and  infiltration  rates  of  water  through  the  soils.  Particularly,  the  hydrogels  reduce  irrigation  frequency  and  compaction  tendency,  stop  erosion  and  water  run  off,  and  increase  the  soil  aeration  and  microbial  activity.    

In  arid  areas,  the  use  of  SAPs  in  sandy  soil  (macroporous  medium),  to  increase  its  water-­‐holding  capacity  is  one  of  the  most  significant  means  to  improve  the  quality  of  plants.  The  SAP  particles  may  be  though  of    as  "miniature  water  reservoirs"  in  he  soil.  Water  will  be  removed  from  these  reservoirs  upon  the  root  demand  through  osmotic  pressure  difference.  The  hydrogels  also  act  as  a  controlled  release  system  by  favoring  the  uptake  of  some  nutrient  elements,  holding  them  tightly,  and  delaying  their  dissolution.  Consequently,  the  plant  can  still  access  some  of  the  fertilizers,  resulting  in  improved  growth  and  performance  rates.    

SAPs  can  also  be  used  as  retaining  materials  in  the  form  of  seed  additives  (to  aid  in  germination  and  seedling  establishment),  seed  coatings,  root  dips,  and  for  immobilizing  plant  growth  regulator  or  protecting  agents  for  controlled  release.    

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WATER - INSOLUBLE POLYMERS

This  class  of  polymers  often  referred  to  as  gel-­‐forming  polymers  or  insoluble  water-­‐absorbing  polymers  were  first  introduced  for  agricultural  use  in  the  early  1980's.  These  polymers  do  not  possess  linear  chain  structures  as  described  previously  but  the  chains  are  rather  cross-­‐linked  to  form  a  three-­‐dimensional  network.  Cross-­‐linking  occurs  when  polymerization  is  carried  out  in  the  presence  of  a  small  amount  of  a  divinyl  compound.  Depending  on  synthetic  conditions,  type  and  density  of  covalent  bonds  that  form  cross-­‐  links,  these  polymers  can  absorb  up  to  1000  times  their  weight  in  pure  water  and  form  gels.  Three  main  types  of  hydrogels  (water  absorbing)  have  so  far  been  developed  as  agricultural  polymers:  (1)  starch-­‐graft  copolymers  obtained  by  graft  polymerization  of  polyacrylonitrile  onto  starch  followed  by  saponification  of  the  acrylonitrile  units  (2)  cross-­‐linked  polyacrylates  (3)  cross-­‐linked  polyacrylamides  and  cross-­‐linked  acrylamide-­‐acrylate  copolymers  containing  a  major  percentage  of  acrylamide  units.  Most  of  the  hydrogels  marketed  for  agriculture  come  from  the  latter  group  as  they  are  claimed  to  remain  active  for  a  much  longer  time.    

Gel-­‐forming  polymers  are  small  dry  crystals  that  absorb  water  similar  to  sponges.  Contact  between  the  polymer  granule  and  water  results  in  absorption  until  equilibrium  is  reached.  When  polymers  are  incorporated  into  a  soil  or  soilless  medium  they  retain  large  quantities  of  water  and  nutrients.  These  stored  water  and  nutrients  are  released  as  required  by  the  plant.  Thus,  plant  growth  is  improved,  and/or  water  supplies  are  conserved.    

Researchers  have  found  that  the  use  of  hydrogels  increases  the  amount  of  available  moisture  in  the  root  zone,  thus  allowing  for  much  longer  intervals  between  irrigations.  It  should  be  pointed  out  that  the  polymers  do  not  reduce  the  amount  of  water  used  by  plants.  The  water-­‐holding  capacity  depends  on  the  texture  of  the  soil,  the  type  of  hydrogel  and  particle  size  (powder  or  granules),  the  salinity  of  the  soil  solution  and  the  presence  of  ions.  Cross-­‐linked  polyacrylamides  hold  up  to  400  times  their  weight  in  water  and  release  95%  of  the  water  retained  within  the  granule  to  growing  plants.  In  general,  a  high  degree  of  cross-­‐linkage  results  in  the  material  having  a  relatively  low  water-­‐retention  capacity.  However,  the  water-­‐holding  capacity  drops  significantly  at  sites  where  the  source  of  irrigation  water  contains  high  levels  of  dissolved  salts  (e.g  effluent  water)  or  in  the  presence  of  fertilizer  salts.    

 

 

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POLYMERS FOR SOIL REMEDIATION

Contamination  of  soils  with  toxic  metal  elements  is  of  great  concern  to  scientists  and  the  general  public.  Long-­‐term  intake  of  contaminant  metals  by  humans  may  lead  to  chronic  effects,  although  maximum  acceptable  limits  in  food  were  already  established  for  several  toxic  elements  by  the  National  agency  for  food,  drugs  and  administration  and  control,  European  Food  Service  Authority  and  the  U.S.  Food  and  Drug  Administration.    

Effects  of  metals  on  ecosystems  and  biological  resources  are  also  increasingly  recognized.  Metals  do  not  degrade  as  organic  compounds  do,  and  have  long  retention  times  in  soils.  They  can  however,  exist  in  different  forms,  which  include  water-­‐soluble  (ionic  and  chelated  with  soluble  compounds),  adsorbed  on  soil  surfaces,  chelated  by  insoluble  organic  matter,  precipitated,  occluded  by  soil  oxides  and  hydroxides,  present  in  living  organisms  or  residues,  and  as  part  of  primary  and  secondary  minerals.  Ideally,  a  contaminated  soil  would  be  restored  to  regain  its  original  potential,  but  this  can  be  a  very  expensive  process,  and  thus  depends  not  only  on  the  expected  benefit  of  the  cleanup  and  future  value  of  the  soil,  but  also  on  political  and  public  awareness  of  the  problem.  Conventional  remedial  approaches  to  severely  metal-­‐contaminated  soils  involve  removal  and  replacement  of  soil  with  clean  materials  or  capping  the  soil  with  an  impermeable  layer  to  reduce  exposure  to  contaminants,  chelating  agent  ethylenediaminetetraacetic  acid  (EDTA)  has  been  used  extensively  for  heavy  metals  extraction  from  soil.  Much  work  has  been  done  on  the  recovery  of  metal-­‐loaded  EDTA  by  electrochemical  or  chemical  processes.  Another  chelating  agent,  pyridine-­‐2,  6-­‐dicarboxylic  acid  has  also  been  shown  to  be  effective  in  heavy  metals  although  these  are  not  considered  the  most  economically  or  environmentally  sound  solutions  available.  Only  through  the  establishment  of  a  vegetation  cover  to  stabilize  metal-­‐contaminated  soils  will  a  successful  long-­‐term  rehabilitation  be  achieved.    

Water-­‐soluble  polymers  (WSP)  have  been  used  extensively  for  the  removal  or  recovery  of  metal  ions  from  aqueous  solutions.  There  are  now  reviews  on  the  use  of  this  technology  for  metal  ion  separations.  However,  this  technology  has  only  recently  been  used  to  remove  metals  such  as  lead  from  solid  surfaces.  Three  distinct  advantages  of  using  WSP  are:  1)  The  metal  bound  to  the  polymer  in  solution  can  be  easily  concentrated  by  ultrafiltration  (UF)  2)  the  metal  subsequently  released  from  the  WSP  can  be  easily  segregated  by  UF  to  allow  for  recycle  of  the  extraction  agent  and  disposal  of  the  metal;  and  3)  commercially  available  polymers  can  be  modified  to  selectively  bind  the  target  metal  ions.    

 

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HOW AGRICULTURAL HYDROGELS ARE MADE AND HOW MSRS CAN HELP

Hydrogel  polymers  are  made  from  petroleum-­‐based  products,  but  recent  research  has  enable  their  manufacture  using  byproducts  from  the  Coal  to  Liquids  (CTL),  Coal  to  Syngas  (CTS)  processes  or  from  the  Plasma  Gasification  of  Municipal  Solid  Waste  (PGMSW).  Hydrogels  are  cross-­‐linked  polyacrylamide  polymers  (PAM).  They  are  made  up  of  water-­‐insoluble  acrylamide  and  potassium  acrylate.  Polymers  are  long  parallel  chains  of  molecules,  and  when  cross-­‐linked  they  create  a  network  of  polymeric  chains.  

One  of  the  main  reasons  hydrogel  polymers  are  made  from  petroleum  is  because  the  CTL,  CTS,  and  PGMSW  processes  are  currently  not  cost  effective.  Cost  effectiveness  of  these  processes  are  largely  dependent  upon  the  costs  of  energy  input  to  the  process.  

Molten  Salt  Reactors  (MSRs)  could  easily  make  the  production  of  CTL,  CTS,  and  PGMSW  very  cost  effective  and  thereby  provide  an  economical  way  to  mass-­‐produce  agricultural  hydrogels.

Soils  sometimes  form  semi  hydrophobic  crusts,  which  allow  the  water  to  run  off  instead  of  being  absorbed  in  the  soil.  The  addition  of  hydrogels  in  the  soil  allows  the  water  to  percolate  instead  of  running  off  and  this  retained  moisture  is  then  passed  back  to  the  soil  over  a  period  of  time.  

The  use  of  agricultural  hydrogels  also  allows  damaged  or  unusable  agricultural  land  to  be  reclaimed.  When  hydrogels  are  added  to  the  surface  of  the  soil  the  water  holding  capacity  is  increased  and  rainfall  percolates  the  soil  quite  easily.  Hydrogels  also  reduce  nutrient  loss  from  soils  as  runoff  is  prevented.  In  saline  soils  however  hydrogels  seem  less  effective.  

One  of  the  current  largest  uses  for  PAM  is  to  flocculate  or  coagulate  solids  in  a  liquid,  such  as  in  the  wastewater  treatment  industry.  PAM  can  be  applied  to  various  types  of  wastewater.  The  introduction  of  PAM  as  a  chemical  flocculating  agent  to  wastewater  causes  suspended  particles  in  wastewater  to  aggregate,  forming  what  is  known  as  a  floc.  In  addition,  PAM  products  react  with  water  to  form  insoluble  hydroxides,  which  upon  precipitating,  link  together  to  form  meshes,  physically  trapping  small  particles  into  a  larger  floc.  In  simple  terms,  PAM  makes  the  fine  solids  in  treated  water  adhere  to  one  another  until  they  become  big  enough  to  settle  out  or  be  captured  by  filters  to  make  sewage  sludge.  In  either  case,  the  floc  can  be  filtered  or  removed  more  easily.  

In  municipal  wastewater  treatment,  PAM  can  be  used  in  all  solid-­‐liquid  separation  processes  including  primary  sewage  treatment,  activated  sludge  treatment  and  digested  sludge  treatment.  

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In  industrial  wastewater  treatment,  the  polymers  and  coagulants  are  used  extensively  for  a  wide  variety  of  industrial  processes  involving  paper,  petrochemical,  electroplating,  textiles,  oilfield  chemical  food,  pharmaceutical,  leather  ,  breweries  wineries,  and  slaughterhouses.  

Polyacrylamide  can  also  be  used  to  treat  water  from  mineral  mining  processes,  including  production  of    rare  earths,  coal,  lead,  dioxide,  titanium,  gold,  zinc,  iron,  sand,  phosphoric  acid,  silver,  nickel,  copper,  steel,  gravel,  alumina  uranium  as  well  as  potash  processing.  

Different  types  of  wastewater  require  different  wastewater  treatment  products,  including  different  variances  of  PAM.  The  wastewater  treatment  product  most  effective  in  treating  a  particular  wastewater  will  depend  on,  amongst  other  factors,  the  acids,  chemicals  and  pollutants  found  in  the  wastewater,  as  well  as  the  charge  of  the  wastewater.    

Another  common  use  of  polyacrylamide  is  in  subsurface  applications  such  as  enhanced  oil  recovery,  where  high  viscosity  aqueous  solutions  can  be  injected  to  improve  the  economics  of  conventional  water  flooding.  

For  oil  extraction  applications,  PAM  is  used  to  increase  the  viscosity  of  water  to  improve  the  effectiveness  of  the  water  flooding  process.  In  other  words,  the  P  AM-­‐injected  solution  assists  in  sweeping  (or  pushing)  oil  locked  in  a  reservoir  towards  a  production  pump.  The  result  is  improved  volumetric  sweep  efficiency  –  more  oil  is  produced  for  a  given  volume  of  water  injected  into  the  well.  

Historically,  PAM  oilfield  projects  primarily  used  PAM  supplied  as  a  solid  powder.  This  powder  is  then  hydrated  to  form  an  aqueous  solution.  More  conveniently,  most  PAM  oilfield  projects  now  use  PAM  supplied  in  emulsion  form  as  liquids,  offering  a  more  efficient  and  faster  way  to  get  the  PAM  into  the  aqueous  solution.  

Due  largely  to  early  adoption,  Chinese  PAM  producers  are  the  worldwide  technological  leaders  with  respect  to  the  chemical  compound’s  usage  in  enhanced  oil  recovery.  Not  surprisingly,  Chinese  demand  accounts  for  most  of  the  world's  consumption  in  this  application.  

 

 

CONCLUSIONS

Throughout  human  history,  agriculture’s  main  focus  has  been  providing  a  source  of  food.  Opportunities  have  arisen  through  external  events  and  trends  that  impacted  patterns  of  

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production  and  utilization,  such  as  producing  crops  for  fuel.  Numerous  publications  describe  the  increase  in  yield  of  various  plants  as  a  result  of  better  soil  conditions,  fertilizer,  herbicide  and  pesticide  use  use.  Super  absorbent  polymers  allow  for  the  minimum  use  of  water,  fertilizer,  herbicide,  and  pesticide,  which  facilitates  a  better  and  sustainable  environment.  

Super  Absorbent  Polymer  hydrogels  produced  from  trash  or  readily  available  carbon  feedstocks,  such  as  coal,  have  created  a  very  attractive  story  for  Molten  Salt  Reactors  (MSRs)  as  MSRs  and  the  CTL,  CTS,  and  PGMSW  processes  also  produce  the  components  needed  for  very  cost  effective  desalination  of  brackish  and  seawater.  Considering  the  up  again  and  down  again  price  of  crude  oil,  the  necessity  of  preparing  other  than  petroleum  based  SAPs  seems  obvious.  This  paves  the  way  for  further  developments  in  this  area  in  the  mid  and  far  future  ahead.    

Key  opportunities  exist  for  countries  with  arid  land  to  develop  MSRs  to  provide  electric  power,  transportation  fuel  needed  by  industry,  fresh  water  for  drinking  and  agriculture,  and  away  to  turn  their  arid  deserts  in  to  productive  crop  lands  to  feed  their  people.    

Additionally,  specific  polymers  can  be  produced  to  remediate  contaminated  and  unproductive  lands.