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Struvite-(K) mineral

Struvite-(K) is the approved potassium magnesium phosphate hexahydrate mineral, KMg(PO4).6H2O, IMA 2003-048. It is distinct from ammonium struvite, hazenite, newberyite, anhydrous magnesium potassium phosphate and the mixed battery washwater used in one experiment. Curated evidence concerns laboratory abiotic synthesis and precipitation from real spent-alkaline-battery washwater. Neither microbial formation, a phase-specific potassium recovery yield, industrial precipitation deployment nor criticality inherited from potassium, magnesium or phosphorus is established.

Microbial & Biochemical Mechanisms (2)

Abiotic synthesis of crystalline potassium magnesium phosphate hexahydrate

other

Raising the pH of a magnesium chloride and potassium dihydrogen phosphate solution with potassium hydroxide produced a recoverable crystalline solid assigned to struvite-(K) by powder diffraction and complementary spectroscopy. The experiment establishes a synthetic mineral analogue, not microbial precipitation or recovery from an industrial waste feed.

Experimental Context & Analytical Limits:
Gardner2021 Section 2.1 (page 196, PDF page 2) used 25 g KH2PO4 and 5 g anhydrous MgCl2 in 100 mL deionized water, with a nominal Mg:P ratio of 1:3.5. After ten minutes of stirring, the flask was angled about 45 degrees and the initial pH 4.4 was raised to 7.5 by approximately 20 mL 45 wt% KOH added in 1-2 mL increments. The mixture stood at room temperature for seven days. The white solid was vacuum-filtered, washed repeatedly with deionized water and finally acetone, and vacuum-desiccated for two days. No independent synthesis-replicate count or matched precursor-omission control series is reported. The n=10 composition analyses are EDX spots, not independent synthesis batches.
Curated Evidence Points:
Section 2.1 reports 13.61 g isolated powder, stated as 0.0511 mol and 97.26% yield relative to the limiting 0.0525 mol magnesium precursor. This is the authors' isolated-solid synthesis yield on a magnesium basis, not a wastewater removal percentage or proof of absolute purity. Section 3.1 and Figures 2-3 (page 197, PDF page 3) show the diffraction pattern indexed against the struvite-K reference and prismatic/tabular particles; morphology alone is not the phase assignment.
Sections 3.1-3.2 and Figure 4 (pages 197-198, PDF pages 3-4) report no precursor peaks visible by diffraction, but a weak phosphorus NMR resonance near 3.8 ppm could represent residual KH2PO4 below the diffraction detection limit. Thus the claimed complete reaction does not establish an impurity-free product. The observed major phosphorus, magnesium and potassium environments support the assigned analogue; they do not identify biological involvement.
Figure S1 on supplementary page S2 shows a representative BSE image and EDX spectrum containing K, Mg, P and O. Main Section 3.1 describes ten spot analyses and a near-target Mg:K:P ratio. This is supporting elemental evidence, not an independent quantitative water assay or a universal phase-purity measurement.
Context_only Source: ima_2026_09
The exact Struvite-(K) row and list definitions establish the approved mineral name, ideal composition and IMA number 2003-048. They do not certify either synthetic preparation or confer an element's criticality.
The complete identity entry describes the potassium equivalent of struvite from Switzerland and Austria, with natural diffraction and structural information. The Austrian bone-alteration occurrence is not an experimentally established microbial formation mechanism.

Chemical precipitation of struvite-(K)-bearing solids from spent-battery washwater

other

Magnesium oxide and phosphoric acid additions to real potassium-rich alkaline-battery washing water produced struvite-(K)-assigned solids, with reagent- and pH-dependent newberyite, hazenite and residual MgO. Laboratory concentration-removal percentages, fitted crystalline phase fractions and isolated mineral recovery are distinct quantities. No inoculum or biological mechanism was tested, and the pilot filtration used to prepare the feed does not demonstrate pilot precipitation.

Experimental Context & Analytical Limits:
Abayie2025 Sections 2.1-2.6 and Tables 1-3 (PDF pages 2-4) describe Tracegrow-supplied washwater prepared from 137.4 kg sieved, magnetically separated spent alkaline-battery black mass and 87.9 L water. After one hour of mixing and overnight settling, the surface liquid was pilot filter-pressed, yielding about 35 L of feed with pH 13.4. Precipitation used 600 mL feed in 700 mL beakers, duplicate experiments at 25 degrees C, 500 rpm mixing, three hours reaction, one hour settling, filtration and ten days room-temperature desiccation. Model 1 used nominal 85% sidestream MgO with NaOH pH adjustment; Model 2 used that MgO at pH 7 with HCl; Model 3 compared nominal 71% sidestream and 97% commercial MgO at pH 7 and nominal Mg:K:P 0.5:1:0.5. Other ratios and pH values are separate arms. No matched reagent-free or ionic-strength-matched control series or closed potassium mass balance is reported.
Curated Evidence Points:
Sections 3.3-3.5 and Figures 4-7 (PDF pages 7-10) show the pH-7 products' diffraction and SEM-EDS. Figure 6b identifies struvite-K in both Model 3 products; newberyite accompanies the sidestream arm. Figure 6a and Section 3.5 report first-cycle K concentration removal of 59.5% for nominal 71% sidestream MgO and 65.1% for nominal 97% commercial MgO. Equation 3 in Section 2.7 is (K0-K1)/K0 using solution concentrations. These are not phase-specific solid recovery yields, and the equation does not itself correct for reagent-volume changes.
Sections 3.4-3.5 report Rietveld-derived struvite-K phase proportions, including 82% and 99.8% for Model 3 sidestream and commercial products. Figures 4b and 6b show assigned peaks but no refinement residuals, internal-standard amorphous correction or uncertainty for those fractions. Those reported fitted proportions are not adopted as an absolute purity or potassium-yield claim. Local SEM-EDS ratios and morphology in Figures 5 and 7 do not remove that limitation.
Section 3.5 (PDF pages 8-9) reports no further change in potassium concentration during the second recycled-water precipitation cycle; potassium was not fully removed. The proposed chloride interference and competing-phase explanations were not isolated experimentally from the simultaneous pH, reagent and solution-composition changes.
Figures S1-S4 show different phase-labelled mixtures at Model 1 pH 10.5-12, including hazenite-dominated high-ratio patterns. Table S1 supplies final concentration cells, not a solid mass balance or raw refinement files. The Model 1 aqueous potassium removal cannot be assigned entirely to struvite-(K); no phase-specific yield is inferred from those mixed solids.
The abstract calls commercial MgO 95%, whereas Sections 2.1, 2.6, Table 3 and Figure 6 use 97%; the latter defines the curated arm. Sidestream MgO is described as 71% or 70.9%, while Table 1 gives 70.01 wt% MgO. Table 3 reagent doses are retained as source-defined nominal recipes rather than independently reconciled stoichiometry. Table 4 lists Model 2 Cd as 2 mg/kg against its own 1.5 mg/kg inorganic fertilizer limit, contradicting Section 3.6's statement that every measured heavy metal is below the listed limits. No fertilizer compliance, safe agricultural use or current regulatory claim is made.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026: definitions on PDF page 1 and Struvite-(K) row on PDF page 208; approved A, 2003-048, ideal KMg(PO4)(H2O)6.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15)
  2. handbook_struvite_k: Handbook of Mineralogy, Struvite-(K), complete one-page entry revised 19 April 2011; natural mineral identity, diffraction and occurrence.
    https://www.handbookofmineralogy.org/pdfs/struvite-K.pdf (accessed 2026-10-15)
  3. gardner2021: Gardner et al. (2021). Characterization of and Structural Insight into Struvite-K, MgKPO4.6H2O, an Analogue of Struvite. Inorganic Chemistry 60:195-205. Complete 11-page original from White Rose; synthesis and characterization Sections 2.1-3.2, Figures 1-4.
    https://doi.org/10.1021/acs.inorgchem.0c02802 (accessed 2026-10-15)
  4. gardner2021_si: Gardner et al. official Supporting Information, ic0c02802_si_001.pdf, three pages; Figure S1 SEM/EDX and Figure S2 thermal-product refinements, acquired from the ACS Figshare deposit.
    https://doi.org/10.1021/acs.inorgchem.0c02802.s001 (accessed 2026-10-15)
  5. abayie2025: Abayie et al. (2025). K-Struvite precipitation from source-separated battery wastewater. Journal of Environmental Chemical Engineering 13:117323. Complete 12-page original from OuluREPO; Methods 2.1-2.7, Figures 1-7 and Tables 1-4.
    https://doi.org/10.1016/j.jece.2025.117323 (accessed 2026-10-15)
  6. abayie2025_si: Abayie et al. official supplementary DOCX, 1-s2.0-S2213343725020196-mmc1.docx; Figures S1-S4 original embedded diffraction images and Table S1 native table cells inspected.
    https://ars.els-cdn.com/content/image/1-s2.0-S2213343725020196-mmc1.docx (accessed 2026-10-15)

Curation History

Timestamp Curator Action Summary
2026-10-15T06:13:08.382896Z codex (GPT-6; codex) CREATE Added the distinct struvite-(K) mineral with primary-supported abiotic synthesis and battery-washwater precipitation, retaining phase mixtures, removal denominators, second-cycle null and source inconsistencies.

Record source: data/records/struvite-k.yaml