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Waste multilayer ceramic capacitors secondary resource

Discarded multilayer ceramic capacitor components, represented here by components removed from printed circuit boards of twenty post-consumer computers. This feed is distinct from whole printed circuit boards, tantalum capacitors, pure barium titanate and its constituent elements. The characterized batch contained ceramic and metallic phases; neither a universal capacitor composition nor a criticality designation is assigned. The accepted experiment uses chemical deep eutectic solvents and provides no microbial mechanism or industrial deployment evidence.

Microbial & Biochemical Mechanisms (1)

Abiotic metal mobilization by choline-chloride-based solvents

separation

Chemical solvent exposure mobilized copper, nickel, iron and zinc from pulverized capacitor components into analyzed solution. The citric-acid binary and citric-acid-containing ternary formulations gave greater copper and zinc release than the glycerol binary formulation; nickel release was strongest with the citric-acid binary formulation. These source-scoped comparative trends do not establish a unique molecular pathway, isolated metal products or a validated overall recovery yield.

Experimental Context & Analytical Limits:
A heat gun removed components from the computer boards; its temperature and exposure duration were not specified. Components were pulverized, homogenized and quartered into 100 g fractions, without a reported particle-size distribution. Table 1 reports XRF elemental percentages including Ni 16.1, Fe 5.8, Cu 2.5 and Zn 1.5; this is not a universal feed specification or an independently closed mass balance. Table 2 assigns BaTiO3, BaFeO3-x, Fe3O4, CuZn5 and Cu0.81Ni0.19 with qualitative abundance symbols; no diffractogram or quantitative phase fractions accompany that table. Solvents were prepared at 80 degrees C with stirring until homogeneous and cooled to 15 degrees C. Choline chloride to glycerol was 1:2 molar, choline chloride to citric acid was 1:1, and the ternary choline chloride:glycerol:citric acid ratio was 2.4:3.4:1. Laboratory assays used 0.2 g powder with 10 g solvent, 90 degrees C, 400 rpm and up to 24 h. This loading is a mass ratio, not an inferred mass-per-volume concentration. Filtered 200 microlitre samples were diluted to 50 mL in 2% HCl and analyzed by atomic absorption spectroscopy. Replicate numbers, error-bar definitions, matched component-only controls and an explicit sampling-loss correction are not supplied in the methods.
Curated Evidence Points:
Sections 4.1-4.4, Tables 1-4 and Figure 5 establish the post-consumer component feed, chemical formulations and assay. Figures 1-4 and Sections 2.2.1-2.2.4 support metal mobilization and the stated broad solvent rankings. Glycerol-only hydrogen-bond-donor formulation showed comparatively weak copper and nickel release, so adding a ternary formulation does not establish universal improvement over either binary solvent. The study did not isolate recovered metals or demonstrate solvent reuse in these experiments.
Numerical extraction claims conflict within the source. Section 2.2.2 first reports approximately 25% nickel for the ternary and 6% for the glycerol binary at 24 h, consistent with Figure 2 and the conclusion, but its next paragraph gives 68% and 16%. The abstract gives a 60% iron maximum whereas Figure 3 and the conclusion indicate about 68% for the citric-acid binary; other iron endpoints also differ between prose and conclusion. Near-complete copper and nickel values are variously rounded to 99% or 100%. No single reconciled extraction percentage is accepted. Section 4.4 lists samples at 0.5, 1, 2, 4, 6 and 24 h, whereas the figures include a 16 h point. These discrepancies prevent reconstruction of an unambiguous time-course dataset from the article alone.
Section 3.3 and Table 3 explicitly derive ternary viscosity from a theoretical estimate and other physical properties from literature, rather than measuring the prepared assay solvents. Proposed proton donation, complexation and improved mass transfer remain explanations without direct speciation or kinetic discrimination. Section 3.5 proposes further characterization. Energy savings, low toxicity, solvent recyclability and industrial scalability are not established by this laboratory leaching comparison. Results for whole boards or other capacitor chemistries cited in the discussion are not transferred.

Sources & References

  1. masache2025: Masache-Romero, Moreno, Sanchez and Aragon-Tobar (2025). Sustainable Recovery of Cu, Fe, Ni, and Zn from Multilayer Ceramic Capacitors Using a Ternary Deep Eutectic Solvent. Molecules 30:4254. DOI 10.3390/molecules30214254; complete original, Sections 2-5, Tables 1-4 and Figures 1-5.
    https://doi.org/10.3390/molecules30214254 (accessed 2026-10-14)

Curation History

Timestamp Curator Action Summary
2026-10-14T18:49:59.799118+00:00 Codex (GPT-6; Codex) CREATE Created a distinct post-consumer MLCC resource and abiotic solvent-leaching mechanism after full primary and graphics inspection; retained conflicting extraction values and evidence limits.

Record source: data/records/waste-multilayer-ceramic-capacitors.yaml