{
  "abstract": "Refinery spent caustic is difficult to treat because of its high alkalinity, sulfur species and dissolved organics. Independent electrolyte-model calculations (PHREEQC; not experimental validation) show that lime treatment cannot both recover caustic and precipitate sulfate as gypsum: gypsum fell below 0.1% of the sulfate once the equilibrium hydroxide exceeded 0.08–0.23 mol/kg (25–90 °C; up to 0.31 with solubility-product shifts of ±0.5 log units), while carbonate causticization stayed favorable (97% conversion at 25 °C, 1 M initial NaOH). Sulfate removal as a solid therefore needs a separate environment from caustic recovery, which defines when neutralization, causticization with recycle or a staged hybrid applies. A Monte Carlo model (10,000 draws; 720 to 1,320 designs) carries this constraint into process design, a sulfate-limited recycle loop and an economic screen against third-party disposal. Oxygen supply is the physical limit: at 80 °C with atmospheric air the required oxygen-transfer rate exceeds the achievable one by a median factor of 23, so the kinetics-only optimum (median NPV $11.7M for Route B, $5.4M for neutralization) is an upper bound. The preferred design is conditional on oxygen enrichment: with 90% oxygen, 60 °C and 12 h, Route B has a median NPV of $6.4M (P10 −$1.3M; P(NPV>0) = 84%) against $0.2M for neutralization, but it meets the sulfide-removal requirement in only 39% of draws without chemical enhancement of transfer and 67% with half the assumed kLa; with air it is not viable. Results are conditional screening values, not forecasts; no experimental data are reported.",
  "abstract_shown": true,
  "affiliations": [
    "Independent researcher"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 1,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Leon Sandler",
      "orcid": "0009-0007-4584-808X"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/4k57m73z7h786.bib",
  "cited_by": 0,
  "doi": "10.26434/chemrxiv.15010706/v1",
  "fulltext_url": null,
  "id": "4k57m73z7h786",
  "issns": [],
  "landing_url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010706/v1",
  "language": null,
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "2207|Process Optimization and Integration"
    ]
  ],
  "openalex": "W7222609022",
  "pdf_url": "https://chemrxiv.org/doi/pdf/10.26434/chemrxiv.15010706/v1",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-20",
  "publisher": "American Chemical Society (ACS)",
  "ris": "https://research.draconitic.com/paper/4k57m73z7h786.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:24Z",
      "native_id": "10.26434/chemrxiv.15010706",
      "source": "chemrxiv",
      "url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010706/v1"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "source:chemrxiv",
      "subfield": "general"
    }
  ],
  "title": "Uncertainty-Aware Techno-Economic Assessment of Calcium-Based Treatment and Caustic Recovery from Refinery Spent Caustic",
  "title_text": "Uncertainty-Aware Techno-Economic Assessment of Calcium-Based Treatment and Caustic Recovery from Refinery Spent Caustic",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:24Z",
  "url": "https://research.draconitic.com/paper/4k57m73z7h786",
  "venue": "ChemRxiv",
  "versions": []
}