Calcium hydroxide precipitation in an electrolytic reactor with hydrodynamic separation

Abstract

A system and method to precipitate calcium hydroxide at low temperatures (T<40° C.) using an electrolytic reactor with hydrodynamic separation. The calcium can be supplied by any calcium bearing material such as calcium carbonate or basalt rock, or from industrial wastes such as brine or steel slag. The solid feedstock undergoes dissolution, whereas the brine may be utilized as is. Once in solution, the feed stream is directed towards an electrolyzer reactor which comprises a cathode, an anode, and a membrane separator. At the cathode, or in a separate precipitation chamber, an alkaline catholyte solution containing calcium hydroxide (portlandite) and magnesium hydroxide (brucite) precipitates, and hydrogen gas is produced.

1 - 84 . (canceled) 
     
     
         85 . A system comprising:
 a dissolution chamber disposed at a first end of the system comprising:
 a first anolyte inlet disposed at a first end of the dissolution chamber; 
 a feed inlet disposed at the first end of the dissolution chamber; and 
 a first leachate outlet disposed at a second end of the dissolution chamber; and 
 a first spent mixture outlet disposed at the second end of the dissolution chamber; 
   a pretreatment chamber coupled to the dissolution chamber comprising:
 a first leachate inlet disposed at a first end of the pretreatment chamber and coupled to the first leachate outlet; 
 a first nanofiltration feed outlet disposed at a second end of the pretreatment chamber; 
 a first waste stream outlet disposed at the second end of the pretreatment chamber; and 
 a first filtration membrane disposed between the first leachate inlet and the first nanofiltration feed outlet; 
   at least one nanofiltration unit coupled to the pretreatment chamber comprising:
 a first nanofiltration feed inlet disposed at a first end of the at least one nanofiltration unit and coupled to the first nanofiltration feed outlet; 
 a first retentate outlet disposed at the first end of the at least one nanofiltration unit; 
 a first permeate outlet disposed at a second end of the at least one nanofiltration unit; and 
 a nanofiltration membrane disposed between the first retentate outlet and the first permeate outlet; 
   an electrolyte chamber coupled to the at least one nanofiltration unit comprising:
 a first electrolyte feed inlet coupled to an electrolyte feed source; 
 a first permeate inlet coupled to the first permeate outlet of the at least one nanofiltration unit; and 
 a first electrolyte product outlet; 
   an electrochemical cell coupled to the at least one nanofiltration unit and the electrolyte chamber comprising:
 a cathodic chamber coupled to the at least one nanofiltration unit comprising:
 a first retentate inlet coupled to the first retentate outlet; 
 a first conductive element; 
 a first catholyte solution outlet; 
 a plurality of flow channels configured to facilitate the passage of fluids through the cathodic chamber; and 
 a first gas outlet; 
 
 an anodic chamber coupled to the cathodic chamber and the electrolyte chamber, comprising:
 a. first electrolyte product inlet coupled to the first electrolyte product outlet of the electrolyte chamber; 
 a second conductive element: 
 a first anolyte solution outlet; and 
 a second gas outlet; 
 
 an electrochemical membrane disposed between the cathodic chamber and the anodic chamber, and 
 wherein the cathodic chamber and the anodic chamber are in ionic communication; 
   a settling chamber coupled to the cathodic chamber comprising:
 a first catholyte inlet disposed at a top of the settling chamber; 
 a first mineral outlet disposed at a first bottom of the settling chamber; and 
 a catholyte supernatant outlet; 
   an anolyte chamber coupled to the anodic chamber comprising:
 a first anolyte solution inlet disposed at a top of the anolyte chamber and coupled to the first anolyte solution outlet of the anodic chamber; and 
 a second spent mixture outlet. 
   
     
     
         86 . The system of  claim 85 , wherein the first conductive element and second conductive element are separated by an interelectrode distance from 0 mm to about 18 mm. 
     
     
         87 . The system of  claim 85 , wherein the feed inlet is a calcium feed inlet. 
     
     
         88 . The system of  claim 85 , wherein the dissolution chamber further comprises an apparatus, disposed at a position between the first and second ends of the dissolution chamber, selected from a mechanical agitator, a sonicator, or an impeller. 
     
     
         89 . The system of  claim 85 , wherein the first conductive element is in the form of a mesh, plate, or rod and is selected from iron, iron alloy, nickel, nickel alloy, titanium, titanium alloy, aluminum, aluminum alloy, and platinum, or a combination of any of the foregoing. 
     
     
         90 . The system of  claim 85 , wherein the first conductive element is in the form of a mesh, plate, or rod and is selected from transition group metals, platinum group metals, or a combination of any of the foregoing. 
     
     
         91 . The system of  claim 89 , wherein the first conductive element further comprises a coating comprising platinum, nickel phosphate, or molybdenum sulfate. 
     
     
         92 . The system of  claim 85 , wherein the first gas is hydrogen. 
     
     
         93 . The system of  claim 85 , wherein the second conductive element is selected from a group VIII metal, a group IX metal, a group X metal, titanium clad with a group VIII metal, titanium clad with a group LX metal, titanium clad with a group X metal, and titanium clad with mixed metal oxide, or a combination of any of the foregoing. 
     
     
         94 . The system of  claim 85 , wherein the second conductive element is selected from a transition group metal, platinum group metal, or a combination of any of the foregoing. 
     
     
         95 . The system of  claim 85 , wherein the electrochemical membrane comprises PVDF, PTFE, cellulose, a copolymer of tetrafluoroethylene and sulfonated perfluorovinyl ether, sodium polystyrene sulfonate, poly(2-acrylamido-2-methyl-1-propanesulfonic acid), poly(acrylamido-N-propyltrimethylammonium chloride), poly[(3-(methacryloylamino)-propyl]trimethylammonium chloride), or polyethylenimine. 
     
     
         96 . The system of  claim 85 , wherein the first mineral outlet is a Ca(OH) 2  outlet. 
     
     
         97 . The system of  claim 85 , further comprising a precipitation chamber coupled to the cathodic chamber and the settling chamber comprising:
 a second catholyte inlet coupled to the first catholyte solution outlet of the cathodic chamber;   a precipitate outlet disposed at a bottom of the precipitation chamber; and   a second supernatant outlet disposed at a top of the precipitation chamber and coupled to the first catholyte inlet of the settling chamber.   
     
     
         98 . The system of  claim 85 , wherein the anolyte chamber further comprises a first recycled anolyte outlet, and wherein the dissolution chamber further comprises a first recycled anolyte inlet coupled to the first recycled anolyte outlet. 
     
     
         99 . The system of  claim 85 , wherein the electrochemical cell has a production capacity of about 1 kg/day, about 2 kg/day, about 3 kg/day, about 4 kg/day, about 5 kg/day, about 6 kg/day, about 7 kg/day, about 8 kg/day, about 9 kg/day, about 10 kg/day, about 15 kg/day, about 20 kg/day, about 25 kg/day, about 30 g/day, about 40 g/day, about 50 g/day, about 60 g/day, about 70 g/day, about 80 g/day, about 90 g/day, about 100 g/day, about 125 g/day, about 150 g/day, about 175 g/day, or about 200 g/day. 
     
     
         100 . The system of  claim 85 , wherein the electrochemical cell has an electrode area of about 6 cm 2 , about 8 cm 2 , about 10 cm 2 , about 12 cm 2 , about 14 cm 2 , about 16 cm 2 , about 18 cm 2 , about 20 cm 2 , about 22 cm 2 , about 24 cm 2  about 2500 cm 2 , about 3500 cm 2 , about 4500 cm 2 , about 5500 cm 2 , about 6500 cm 2 , about 7500 cm, about 8500 cm, about 9500 cm 2 , or about 10,500 cm 2    
     
     
         101 . The system of  claim 85 , wherein the electrochemical cell has a Faradaic efficiency of greater than about 95% at an influent flowrate of about 20 mL/min and a reactor volume of about 40 L, about 45 L, about 50 L, about 55 L, about 60 L, about 65 L, about 70 L, about 75 L, about 80 L, about 85 L, or about 90 L. 
     
     
         102 . The system of  claim 85 , wherein the system is configured to produce a metal salt. 
     
     
         103 . The system of  claim 85 , wherein the electrochemical cell has an applied current density of about 300 A/m 2  about 500 A/m 2 , about 1000 A/m 2 , about 3000 A/m 2 , about 5000 A/m 2 , about 10000 A/m 2 , about 15000 A/m 2 , about 20000 A/m, about 25000 A/m 2 , or about 30000 A/m 2 . 
     
     
         104 . The system of  claim 85 , wherein the nanofiltration membrane comprises a plurality of pores, and each of the plurality of pores has a pore diameter of from about 0.001 to about 0.01 μm. 
     
     
         105 . The system of  claim 85 , wherein the system comprises one nanofiltration unit coupled to the pretreatment chamber. 
     
     
         106 . A method comprising:
 combining a solid comprising target ions and a neutral fluid or an acidic fluid in a dissolution chamber, thereby forming a first suspension;   passing the first suspension into a pretreatment chamber configured to remove impurities from and filter the first suspension to form a nanofiltration feed solution comprising the target ions;   passing the nanofiltration feed solution into at least one nanofiltration unit configured to separate the nanofiltration feed solution to form a permeate and a retentate comprising the target ions;   passing the retentate via a first retentate outlet to an electrochemical cell;   performing an electrochemical process comprising:
 applying a voltage to a cathode and an anode in the electrochemical cell; 
 contacting the cathode disposed inside the electrochemical cell with the retentate thereby forming hydrogen gas and a catholyte solution; 
 contacting the anode disposed inside the electrochemical cell with an anolyte solution thereby producing oxygen gas;
 wherein an electrochemical membrane is disposed between the anode and the cathode, and the cathode and anode are in ionic communication; 
 
   passing the catholyte solution via a catholyte solution outlet into a settling chamber and precipitating mineral precipitates from the catholyte solution, thereby forming mineral precipitates and a catholyte supernatant;   passing the mineral precipitates from the settling chamber via a mineral outlet.