{
  "spore": "profile",
  "id": "zeolite-5a",
  "spore_version": "0.2",
  "family": "oxide-ceramics",
  "name": "Zeolite 5A molecular sieve",
  "abbreviation": "5A",
  "role": "CO2 and water sorbent (molecular sieve)",
  "category": "ceramics",
  "type": "oxides",
  "summary": "Zeolite 5A is the calcium form of zeolite A, a synthetic aluminosilicate with pores of 5 angstroms (Zeochem). It is the CO2 sorbent in the ISS Carbon Dioxide Removal Assembly, whose beds are designed to operate at 204 °C (NASA). NASA's hydrothermal tests show that humid thermal cycling breaks the pellets into dust, and the RK-38 product broke down fastest.",
  "best_for": "Regenerable CO2 removal in thermal-swing beds such as the ISS CDRA, where the design operating temperature is 204 °C (NASA)",
  "weakest_at": "Dust from pellet breakdown under humid thermal cycling; in NASA's test the RK-38 bed pressure drop rose 74.5 % per 1000 hours at 1.38 mmHg inlet water vapour",
  "identity": {
    "formula": "Calcium-exchanged zeolite A, a crystalline aluminosilicate (CaA, the 5A form)",
    "designations": [
      {
        "system": "Trade name",
        "code": "UOP RK-38",
        "note": "5A product used in the ISS CDRA",
        "source": "nasa-cdra-2017",
        "where": "Table 2, row UOP RK-38 (5Å, CaA zeolite, used in CDRA)"
      },
      {
        "system": "Trade name",
        "code": "UOP ASRT",
        "note": "older 5A pellet product, no longer produced",
        "source": "nasa-cdra-2017",
        "where": "Table 2, row UOP ASRT 1995 and ASRT 2005; text says ASRT can no longer be produced"
      },
      {
        "system": "Trade name",
        "code": "Grace MS 522",
        "note": "5A bead product",
        "source": "nasa-cdra-2017",
        "where": "Table 2, row Grace MS 522 (5Å, CaA zeolite)"
      },
      {
        "system": "Trade name",
        "code": "BASF 5A",
        "note": "5A bead product",
        "source": "nasa-cdra-2017",
        "where": "Table 2, row BASF 5A (5Å, CaA zeolite)"
      },
      {
        "system": "Trade name",
        "code": "5A Purmol Powder",
        "note": "manufacturer powder, calcium form",
        "source": "zeochem-molecular-sieves",
        "where": "Molecular sieves page, 5A Purmol Powder entry"
      }
    ],
    "source": "nasa-cdra-2017",
    "where": "Table 2 lists the 5Å products as CaA zeolite (UOP RK-38, UOP ASRT, Grace MS 522, BASF 5A)"
  },
  "tags": {
    "environments": [
      "low-earth-orbit"
    ],
    "stresses": [
      "thermal-cycling"
    ],
    "applications": [
      "habitats-and-suits"
    ]
  },
  "properties": [
    {
      "benchmark": "pore_diameter",
      "label": "Pore size of calcium-form 5A powder",
      "value": 5,
      "bound": "exact",
      "unit": "angstroms",
      "scope": "material",
      "conditions": {
        "form": "5A Purmol Powder, calcium (Ca) form",
        "basis": "nominal pore size printed by the manufacturer"
      },
      "method": "Manufacturer product-page statement of nominal pore size",
      "status": "ground",
      "source": "zeochem-molecular-sieves",
      "where": "5A Purmol Powder entry on the molecular sieves page",
      "source_detail": {
        "title": "Zeochem: Molecular sieves product page (5A Purmol Powder entry)",
        "url": "https://www.zeochem.com/our-products/molecular-sieves",
        "kind": "datasheet"
      }
    },
    {
      "benchmark": "operating_temperature",
      "label": "Design operating temperature of the ISS CDRA CO2 removal beds",
      "value": 204,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "design operating temperature quoted as 400°F (204°C) for the on-orbit CDRA CO2 beds",
        "configuration": "uniform packed beds of 5A zeolite with an embedded heating element"
      },
      "method": "Design value stated in the NASA paper; flight hardware specification, not a measured test result",
      "status": "flight",
      "source": "nasa-cdra-2017",
      "where": "Section I (Introduction), paragraph after the Figure 1 caption",
      "source_detail": {
        "title": "NASA ICES-2017-188: Investigation of Desiccants and CO2 Sorbents for Exploration Systems 2016-2017",
        "url": "https://ntrs.nasa.gov/api/citations/20170008962/downloads/20170008962.pdf",
        "year": 2017,
        "kind": "paper"
      }
    },
    {
      "benchmark": "hydrothermal_test_temperature",
      "label": "Sorbent set point in the hydrothermal stability test",
      "value": 204.4,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "segment": "Table 2 steps 2 and 3, sorbent temperature",
        "cycle": "thermal profile matched to ISS CDRA ramp rates"
      },
      "method": "Set point of the NASA Hydrothermal Stability Test thermal profile",
      "status": "ground",
      "source": "nasa-hst-2015",
      "where": "Table 2 (HST Sorbent Temperature Profile), steps 2 and 3",
      "source_detail": {
        "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
        "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
        "year": 2015,
        "kind": "paper"
      }
    },
    {
      "benchmark": "heating_ramp_rate",
      "label": "Heating ramp to the test set point",
      "value": 2.84,
      "bound": "exact",
      "unit": "°C/min",
      "scope": "material",
      "conditions": {
        "segment": "step 2 of the HST profile, heating to 204.4 °C"
      },
      "method": "Ramp rate set in the NASA Hydrothermal Stability Test profile",
      "status": "ground",
      "source": "nasa-hst-2015",
      "where": "Table 2, step 2, Ramp Rate column",
      "source_detail": {
        "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
        "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
        "year": 2015,
        "kind": "paper"
      }
    },
    {
      "benchmark": "rk38_pressure_increase_low",
      "label": "UOP RK-38 bed pressure drop increase, low inlet water vapour",
      "value": 15,
      "bound": "exact",
      "unit": "% /1000 Hours",
      "scope": "material",
      "conditions": {
        "sorbent": "UOP RK-38 (5A)",
        "inlet_h2o_pp": "0.012 mmHg",
        "flow": "1.38 slpm",
        "run": "1056 hour run"
      },
      "method": "Hydrothermal Stability Test; percentage pressure increase normalised per 1000 hours of cyclic operation",
      "status": "ground",
      "source": "nasa-hst-2015",
      "where": "Table 4, RK-38 Bed Pressure Drop, row 0.012, column % /1000 Hours",
      "source_detail": {
        "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
        "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
        "year": 2015,
        "kind": "paper"
      }
    },
    {
      "benchmark": "rk38_pressure_increase_mid",
      "label": "UOP RK-38 bed pressure drop increase, mid inlet water vapour",
      "value": 62.8,
      "bound": "exact",
      "unit": "% /1000 Hours",
      "scope": "material",
      "conditions": {
        "sorbent": "UOP RK-38 (5A)",
        "inlet_h2o_pp": "0.70 mmHg",
        "flow": "1.38 slpm",
        "run": "1056 hour run"
      },
      "method": "Hydrothermal Stability Test; percentage pressure increase normalised per 1000 hours of cyclic operation",
      "status": "ground",
      "source": "nasa-hst-2015",
      "where": "Table 4, RK-38 Bed Pressure Drop, row 0.70, column % /1000 Hours",
      "source_detail": {
        "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
        "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
        "year": 2015,
        "kind": "paper"
      }
    },
    {
      "benchmark": "rk38_pressure_increase_high",
      "label": "UOP RK-38 bed pressure drop increase, high inlet water vapour",
      "value": 74.5,
      "bound": "exact",
      "unit": "% /1000 Hours",
      "scope": "material",
      "conditions": {
        "sorbent": "UOP RK-38 (5A)",
        "inlet_h2o_pp": "1.38 mmHg",
        "flow": "1.38 slpm",
        "run": "1056 hour run"
      },
      "method": "Hydrothermal Stability Test; percentage pressure increase normalised per 1000 hours of cyclic operation",
      "status": "ground",
      "source": "nasa-hst-2015",
      "where": "Table 4, RK-38 Bed Pressure Drop, row 1.38, column % /1000 Hours",
      "source_detail": {
        "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
        "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
        "year": 2015,
        "kind": "paper"
      }
    },
    {
      "benchmark": "asrt_pressure_increase_low",
      "label": "UOP ASRT (5A) bed pressure drop increase, low inlet water vapour",
      "value": 5.64,
      "bound": "exact",
      "unit": "% /1000 Hours",
      "scope": "material",
      "conditions": {
        "sorbent": "UOP ASRT (5A)",
        "inlet_h2o_pp": "0.012 mmHg",
        "flow": "1.38 slpm",
        "run": "1056 hour run"
      },
      "method": "Hydrothermal Stability Test; percentage pressure increase normalised per 1000 hours of cyclic operation",
      "status": "ground",
      "source": "nasa-hst-2015",
      "where": "Table 4, ASRT Bed Pressure Drop, row 0.012, column % /1000 Hours",
      "source_detail": {
        "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
        "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
        "year": 2015,
        "kind": "paper"
      }
    },
    {
      "benchmark": "asrt_pressure_increase_mid",
      "label": "UOP ASRT (5A) bed pressure drop increase, mid inlet water vapour",
      "value": 9.49,
      "bound": "exact",
      "unit": "% /1000 Hours",
      "scope": "material",
      "conditions": {
        "sorbent": "UOP ASRT (5A)",
        "inlet_h2o_pp": "0.70 mmHg",
        "flow": "1.38 slpm",
        "run": "1056 hour run"
      },
      "method": "Hydrothermal Stability Test; percentage pressure increase normalised per 1000 hours of cyclic operation",
      "status": "ground",
      "source": "nasa-hst-2015",
      "where": "Table 4, ASRT Bed Pressure Drop, row 0.70, column % /1000 Hours",
      "source_detail": {
        "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
        "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
        "year": 2015,
        "kind": "paper"
      }
    },
    {
      "benchmark": "asrt_pressure_increase_high",
      "label": "UOP ASRT (5A) bed pressure drop increase, high inlet water vapour",
      "value": 6.65,
      "bound": "exact",
      "unit": "% /1000 Hours",
      "scope": "material",
      "conditions": {
        "sorbent": "UOP ASRT (5A)",
        "inlet_h2o_pp": "1.38 mmHg",
        "flow": "1.38 slpm",
        "run": "1056 hour run"
      },
      "method": "Hydrothermal Stability Test; percentage pressure increase normalised per 1000 hours of cyclic operation",
      "status": "ground",
      "source": "nasa-hst-2015",
      "where": "Table 4, ASRT Bed Pressure Drop, row 1.38, column % /1000 Hours",
      "source_detail": {
        "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
        "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
        "year": 2015,
        "kind": "paper"
      }
    },
    {
      "benchmark": "rk38_initial_pressure_low",
      "label": "UOP RK-38 initial bed pressure drop, low inlet water vapour",
      "value": 177,
      "bound": "exact",
      "unit": "Pa",
      "scope": "material",
      "conditions": {
        "sorbent": "UOP RK-38 (5A)",
        "inlet_h2o_pp": "0.012 mmHg",
        "run": "start of 1056 hour run"
      },
      "method": "Initial bed pressure at the start of the run, averaged while the bed is within 2 °C of the adsorb set point",
      "status": "ground",
      "source": "nasa-hst-2015",
      "where": "Table 4, RK-38 Bed Pressure Drop, row 0.012, column Initial Pressure",
      "source_detail": {
        "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
        "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
        "year": 2015,
        "kind": "paper"
      }
    },
    {
      "benchmark": "rk38_initial_pressure_mid",
      "label": "UOP RK-38 initial bed pressure drop, mid inlet water vapour",
      "value": 185,
      "bound": "exact",
      "unit": "Pa",
      "scope": "material",
      "conditions": {
        "sorbent": "UOP RK-38 (5A)",
        "inlet_h2o_pp": "0.70 mmHg",
        "run": "start of 1056 hour run"
      },
      "method": "Initial bed pressure at the start of the run, averaged while the bed is within 2 °C of the adsorb set point",
      "status": "ground",
      "source": "nasa-hst-2015",
      "where": "Table 4, RK-38 Bed Pressure Drop, row 0.70, column Initial Pressure",
      "source_detail": {
        "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
        "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
        "year": 2015,
        "kind": "paper"
      }
    },
    {
      "benchmark": "asrt_initial_pressure_low",
      "label": "UOP ASRT (5A) initial bed pressure drop, low inlet water vapour",
      "value": 399,
      "bound": "exact",
      "unit": "Pa",
      "scope": "material",
      "conditions": {
        "sorbent": "UOP ASRT (5A)",
        "inlet_h2o_pp": "0.012 mmHg",
        "run": "start of 1056 hour run"
      },
      "method": "Initial bed pressure at the start of the run, averaged while the bed is within 2 °C of the adsorb set point",
      "status": "ground",
      "source": "nasa-hst-2015",
      "where": "Table 4, ASRT Bed Pressure Drop, row 0.012, column Initial Pressure",
      "source_detail": {
        "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
        "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
        "year": 2015,
        "kind": "paper"
      }
    },
    {
      "benchmark": "asrt_initial_pressure_mid",
      "label": "UOP ASRT (5A) initial bed pressure drop, mid inlet water vapour",
      "value": 389,
      "bound": "exact",
      "unit": "Pa",
      "scope": "material",
      "conditions": {
        "sorbent": "UOP ASRT (5A)",
        "inlet_h2o_pp": "0.70 mmHg",
        "run": "start of 1056 hour run"
      },
      "method": "Initial bed pressure at the start of the run, averaged while the bed is within 2 °C of the adsorb set point",
      "status": "ground",
      "source": "nasa-hst-2015",
      "where": "Table 4, ASRT Bed Pressure Drop, row 0.70, column Initial Pressure",
      "source_detail": {
        "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
        "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
        "year": 2015,
        "kind": "paper"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Humid process gas during thermal cycling (NASA hydrothermal test)",
      "headline": "Water in the process gas broke the RK-38 5A pellets down into dust much faster than the ASRT product.",
      "effect": "At 1.38 mmHg inlet water vapour the RK-38 bed pressure drop rose 74.5 % per 1000 hours, against 6.65 for ASRT in the same run. NASA's 2025 paper calls RK-38 the product with the poorest hydrothermal stability on ISS.",
      "rating": "moderate",
      "conditions": {
        "cycle": "ISS CDRA-like heating and cooling",
        "run": "1056 hour run"
      },
      "source": "nasa-hst-2015",
      "where": "Table 4 and Section VI (Conclusion)"
    },
    {
      "environment": "Water absorbed by the pellets before strength testing",
      "headline": "Crush strength is sensitive to absorbed water.",
      "effect": "NASA reports a clear sensitivity of the pellet crush strength to absorbed water, which led to the hydrothermal test.",
      "rating": "moderate",
      "source": "nasa-hst-2015",
      "where": "Section I (Introduction), second paragraph"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "No GHS classification or safety data sheet for zeolite 5A was opened in this run. NASA reports that sorbent dust can critically impair the operation of moving parts and seals and can damage pumps and compressors.",
        "ghs": [],
        "source": "nasa-cdra-2017",
        "where": "Introduction, paragraph beginning 'The critical parameter for future systems'"
      }
    ],
    "failure_risks": [
      {
        "mode": "Dusting from pellet breakdown",
        "trigger": "Humid gas during repeated heating and cooling",
        "consequence": "Dust blinds screens, raises the pressure drop and can force a system shutdown and maintenance (NASA 2017).",
        "severity": "high",
        "source": "nasa-cdra-2017",
        "where": "Introduction, paragraph on dust as the critical parameter"
      },
      {
        "mode": "Crushing of the weakest pellets",
        "trigger": "Bed compaction force from the springs",
        "consequence": "Some pellets crush at forces well below the average crush strength, which adds dust.",
        "severity": "moderate",
        "source": "nasa-cdra-dust-2025",
        "where": "Design lesson 5, 'Ensure compacting force will not crush weakest pellets'"
      }
    ],
    "side_effects": [],
    "handling": [
      {
        "text": "Keep the sorbent away from humid gas during heating and cooling cycles. NASA lists humidity adsorbed in the 5A zeolite when it is heated as a suspected cause of the breakdown.",
        "source": "nasa-hst-2015",
        "where": "Abstract"
      },
      {
        "text": "Limit the compaction force so that the weakest pellets do not crush.",
        "source": "nasa-cdra-dust-2025",
        "where": "Design lesson 5"
      }
    ],
    "mitigations": [
      {
        "text": "Cylindrical beds in the SBAR system were a significant improvement in zeolite dust retention and in dust production compared with the rectangular CDRA beds.",
        "source": "nasa-cdra-dust-2025",
        "where": "Section on the SBAR cylindrical beds"
      }
    ]
  },
  "uses": [
    {
      "application": "habitats-and-suits",
      "device": "CO2 removal beds of the ISS Carbon Dioxide Removal Assembly",
      "example": "NASA describes the CDRA CO2 removal beds as uniform packed beds of 5A zeolite, with an embedded heating element and a design operating temperature of 400°F (204°C).",
      "source": "nasa-cdra-2017",
      "where": "Section I (Introduction), paragraph after the Figure 1 caption"
    },
    {
      "application": "habitats-and-suits",
      "device": "Skylab regenerable CO2 removal bed, with 5A as the second layer behind a 13X desiccant layer",
      "example": "NASA's 2025 paper describes the Skylab bed as layered 13X zeolite and 5A zeolite, with 5A as the CO2 layer.",
      "source": "nasa-cdra-dust-2025",
      "where": "Background section, paragraph on the Skylab RCRS bed (near Figure 4)"
    }
  ],
  "supply": [
    {
      "subject": "Natural zeolite minerals (synthetic 5A is made from the 4A form, not mined)",
      "abundance": "No abundance figure for synthetic zeolite A was found in the sources opened. USGS reports world natural zeolite mine production by country for 2025 (estimated).",
      "producers": [
        {
          "country": "Slovakia",
          "year": 2025
        },
        {
          "country": "Georgia",
          "year": 2025
        },
        {
          "country": "Korea, Republic of",
          "year": 2025
        },
        {
          "country": "China",
          "year": 2025
        },
        {
          "country": "Russia",
          "year": 2025
        }
      ],
      "critical_lists": [],
      "recycling": "USGS: zeolites used for desiccation, gas absorbance, wastewater treatment and water purification may be reused after reprocessing; the quantity recycled was unavailable.",
      "substitutes": [
        "magnesium perchlorate",
        "silica gel"
      ],
      "source": "usgs-zeolites-2026",
      "where": "World Mine Production and Reserves table, 2025e column in metric tons (Slovakia 280,000; Georgia 240,000; Korea, Republic of 160,000; China 150,000; Russia 130,000); Substitutes and Recycling sections"
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
      "type": "paper",
      "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
      "year": 2015
    },
    {
      "title": "NASA ICES-2017-188: Investigation of Desiccants and CO2 Sorbents for Exploration Systems 2016-2017",
      "type": "paper",
      "url": "https://ntrs.nasa.gov/api/citations/20170008962/downloads/20170008962.pdf",
      "year": 2017
    },
    {
      "title": "NASA: Advances in Zeolite CO2 Removal System Design for Dust Mitigation",
      "type": "paper",
      "url": "https://ntrs.nasa.gov/api/citations/20250004920/downloads/ICES-2026-371.pdf",
      "year": 2025
    },
    {
      "title": "NASA final report: Space Station Molecular Sieve Development (contract NAS8-36424)",
      "type": "report",
      "url": "https://ntrs.nasa.gov/api/citations/19860021392/downloads/19860021392.pdf",
      "year": 1986
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Zeolites (natural)",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-zeolites.pdf",
      "year": 2026
    },
    {
      "title": "Zeochem: Molecular sieves product page (5A Purmol Powder)",
      "type": "datasheet",
      "url": "https://www.zeochem.com/our-products/molecular-sieves"
    },
    {
      "title": "Wikipedia: Molecular sieve",
      "type": "database",
      "url": "https://en.wikipedia.org/wiki/Molecular_sieve"
    },
    {
      "title": "US patent 3433588: Method for the preparation of 4 angstrom unit zeolites",
      "type": "database",
      "url": "https://patents.google.com/patent/US3433588A/en",
      "year": 1969
    }
  ],
  "gaps": [
    "No GHS classification or safety data sheet for zeolite 5A was opened. The PubChem record returned a browser check, so the hazard entry rests on NASA's dust statement.",
    "No CAS number, UNS, EN, DIN or other standard designation for zeolite 5A was printed in a source opened in this run.",
    "Bulk density, adsorbed water and attrition for the 5A grade appear only in the Wikipedia table. Wikipedia is not used for values here, and no manufacturer datasheet with those figures was opened.",
    "No crush strength for 5A pellets in text: NASA's crush and attrition results are shown only as charts, which were not transcribed.",
    "No CO2 capacity for 5A in text: NASA's capacity results are shown in figures only.",
    "The lowest-humidity row of the NASA hydrothermal test table prints its inlet water-vapour value with an exponent, so that row was left out.",
    "Melting point, crystal density, surface area and thermal conductivity were not searched in this run.",
    "The earlier NASA final report is a scanned document with garbled text. It is cited only for a 5A carbon dioxide retention test; no numbers from it were recorded.",
    "Custom benchmark names were used for the test rows (pore_diameter, operating_temperature, hydrothermal_test_temperature, heating_ramp_rate, and the pressure-rise and initial-pressure rows). None is in spores/property-canon.yaml.",
    "Critical-mineral status for zeolite was not checked against the USGS final list. The USGS chapter was opened, but its critical-minerals table was not.",
    "Producer shares were not calculated: USGS reports mine tonnage for natural zeolites, not output of synthetic 5A.",
    "Terrestrial uses such as industrial drying and natural-gas dehydration appear in the Zeochem table but do not match the space application list, so they are not recorded as uses."
  ],
  "story": {
    "why": "Zeolite 5A is the calcium form of zeolite A, a synthetic aluminosilicate with pores of 5 angstroms (Zeochem). It is the CO2 sorbent in the ISS CDRA, where NASA describes the removal beds as uniform packed beds of 5A zeolite. Its weakness is dust: under humid thermal cycling the pellets break down.",
    "uses": [
      {
        "where": "International Space Station",
        "line": "The ISS Carbon Dioxide Removal Assembly packs 5A zeolite into beds that capture cabin CO2. The beds are heated cyclically to drive the CO2 off again (NASA 2015)."
      },
      {
        "where": "Skylab",
        "line": "The Skylab regenerable CO2 removal bed held 5A zeolite as its CO2 layer, behind a 13X desiccant layer (NASA 2025)."
      }
    ],
    "can_do": [
      {
        "label": "Pore opening",
        "line": "Zeochem prints the pore size of its calcium-form 5A powder as 5 angstroms.",
        "benchmark": "pore_diameter",
        "scope": "material",
        "value": "5 angstroms"
      },
      {
        "label": "CO2 bed temperature",
        "line": "NASA gives the design operating temperature of the ISS CDRA CO2 removal beds as 400°F (204°C).",
        "benchmark": "operating_temperature",
        "scope": "material",
        "value": "204 °C"
      },
      {
        "label": "Humid cycling",
        "line": "In NASA's hydrothermal test at 1.38 mmHg inlet water vapour, the RK-38 bed pressure drop rose 74.5 % per 1000 hours, against 6.65 for ASRT.",
        "benchmark": "rk38_pressure_increase_high",
        "scope": "material",
        "value": "74.5 % per 1000 hours"
      },
      {
        "label": "Heating set point",
        "line": "The hydrothermal stability test heats the sorbent to 204.4 °C at 2.84 °C per minute, matching ISS CDRA ramp rates.",
        "benchmark": "hydrothermal_test_temperature",
        "scope": "material",
        "value": "204.4 °C"
      }
    ],
    "compare": "Among the 5A products in NASA's hydrothermal test, RK-38 beds gained pressure drop faster than ASRT beds at every humidity level, so the product choice matters as much as the zeolite type. NASA's 2025 paper reports that a 13X zeolite was selected for the newer Four-Bed CO2 Scrubber for its overall superiority in strength, attrition resistance, hydrothermal stability and CO2 capacity, while 5A remains the CO2 sorbent of the original CDRA.",
    "compare_rows": [
      {
        "label": "Pore opening",
        "benchmark": "pore_diameter",
        "scope": "material"
      },
      {
        "label": "CDRA bed design temperature",
        "benchmark": "operating_temperature",
        "scope": "material"
      },
      {
        "label": "Pressure increase, RK-38 at 1.38 mmHg",
        "benchmark": "rk38_pressure_increase_high",
        "scope": "material"
      }
    ],
    "handling": [
      "Keep the sorbent away from humid gas during heating and cooling cycles. NASA lists humidity adsorbed in the 5A zeolite when it is heated as a suspected cause of the breakdown.",
      "Limit bed compaction force so that the weakest pellets do not crush (NASA 2025, design lesson 5)."
    ],
    "good_for": [
      "Regenerable CO2 removal in thermal-swing beds. NASA's ISS CDRA packs 5A zeolite into its CO2 beds and is the baseline for future crewed missions beyond low Earth orbit.",
      "Flight heritage. The ISS CDRA has used 5A zeolite, and the Skylab CO2 removal bed also held 5A zeolite (NASA 2025)."
    ],
    "watch_out": [
      "Dust from humid cycling. In NASA's hydrothermal test the RK-38 bed pressure drop rose 74.5 % per 1000 hours at 1.38 mmHg inlet water vapour.",
      "Crush strength depends on water. NASA reports a clear sensitivity of pellet crush strength to absorbed water."
    ],
    "verdict": "Zeolite 5A is the flight-proven CO2 sorbent of the ISS CDRA, but NASA ties its dust problem to humid thermal cycling, so humidity control is part of the design.",
    "recipe": {
      "line": "Zeolite 5A is made from the sodium form of zeolite A by exchanging sodium for calcium. The sodium form is made by combining aqueous sodium silicate and sodium aluminate, then heating to activate it (Wikipedia, production section).",
      "parts": [
        {
          "name": "Sodium form of zeolite A (4A)",
          "role": "Starting sieve. Sodium is the exchangeable cation; the patent describes the 4A form as having a pore size of about 4 angstrom units.",
          "source": "us-patent-3433588",
          "where": "Title and description of US 3433588"
        },
        {
          "name": "Calcium",
          "symbol": "Ca",
          "role": "Ion exchanged into the framework in place of sodium, which gives the 5A (CaA) form.",
          "source": "wikipedia-molecular-sieve",
          "where": "Production section, 4A to 5A by cation exchange"
        },
        {
          "name": "Aluminosilicate framework (silicon, aluminium, oxygen)",
          "role": "The crystal framework that forms the uniform pores.",
          "source": "wikipedia-molecular-sieve",
          "where": "Zeolites are almost always aluminosilicates"
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "No GHS classification or safety data sheet for zeolite 5A was opened in this run.",
        "points": [
          {
            "label": "Dust",
            "line": "NASA states that sorbent dust can critically impair moving parts and seals and can damage pumps and compressors in a spacecraft system."
          }
        ],
        "verdict": "No safety data sheet opened; dust is the stated hazard"
      },
      {
        "title": "For the spacecraft",
        "lead": "NASA's CDRA history shows that dust is the failure mode the bed design must guard against.",
        "points": [
          {
            "label": "Humid cycling",
            "line": "In the NASA hydrothermal test at 1.38 mmHg inlet water vapour, the RK-38 bed pressure drop rose 74.5 % per 1000 hours, against 6.65 for ASRT beds."
          },
          {
            "label": "Crushing",
            "line": "Some pellets crush at forces well below the average crush strength, so bed compaction must be limited (NASA 2025)."
          }
        ],
        "level": 3,
        "verdict": "Dust is the design limit for CDRA beds"
      }
    ]
  },
  "updated": "2026-11-01",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 14,
    "unreachable": 0,
    "caveats": 2,
    "note": "Written by an AI assistant on 2026-11-01 from pages fetched in this run; values copied as printed. The web search budget was used up, so no manufacturer datasheet or SDS was opened."
  },
  "sources": {
    "zeochem-molecular-sieves": {
      "title": "Zeochem: Molecular sieves product page (5A Purmol Powder entry)",
      "url": "https://www.zeochem.com/our-products/molecular-sieves",
      "kind": "datasheet"
    },
    "nasa-hst-2015": {
      "title": "NASA ICES-2015-200: Development of a Test for Evaluation of the Hydrothermal Stability of Sorbents used in Closed-Loop CO2 Removal Systems",
      "url": "https://ntrs.nasa.gov/api/citations/20150016501/downloads/20150016501.pdf",
      "year": 2015,
      "kind": "paper"
    },
    "nasa-cdra-2017": {
      "title": "NASA ICES-2017-188: Investigation of Desiccants and CO2 Sorbents for Exploration Systems 2016-2017",
      "url": "https://ntrs.nasa.gov/api/citations/20170008962/downloads/20170008962.pdf",
      "year": 2017,
      "kind": "paper"
    },
    "nasa-cdra-dust-2025": {
      "title": "NASA: Advances in Zeolite CO2 Removal System Design for Dust Mitigation",
      "url": "https://ntrs.nasa.gov/api/citations/20250004920/downloads/ICES-2026-371.pdf",
      "year": 2025,
      "kind": "paper"
    },
    "nasa-ms-1986": {
      "title": "NASA final report: Space Station Molecular Sieve Development (contract NAS8-36424)",
      "url": "https://ntrs.nasa.gov/api/citations/19860021392/downloads/19860021392.pdf",
      "year": 1986,
      "kind": "report"
    },
    "usgs-zeolites-2026": {
      "title": "USGS Mineral Commodity Summaries 2026: Zeolites (natural)",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-zeolites.pdf",
      "year": 2026,
      "kind": "report"
    },
    "wikipedia-molecular-sieve": {
      "title": "Wikipedia: Molecular sieve",
      "url": "https://en.wikipedia.org/wiki/Molecular_sieve",
      "kind": "web"
    },
    "us-patent-3433588": {
      "title": "US patent 3433588: Method for the preparation of 4 angstrom unit zeolites",
      "url": "https://patents.google.com/patent/US3433588A/en",
      "year": 1969,
      "kind": "database"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/zeolite-5a/"
}