Wang et al. 2024 - Biochar-alginate hydrogel for cadmium soil passivation
Wang and colleagues prepared a modified biochar-calcium alginate hydrogel composite, abbreviated MB-CA, and tested its ability to adsorb Cd(II) from solution and passivate cadmium in contaminated soil. This is mitigation evidence for cadmium-contaminated cultivated land; its spiked-solution and soil-culture values must not be used as product occurrence concentrations.
Key numbers
The abstract reports a highest Cd(II) removal rate of 85.48% in solution and states that MB-CA adsorbed 35.94% of Cd(II) in soil during the soil-culture experiment.
In the pH experiment, five 50 mL portions of 50 mg/L Cd(NO3)2 solution were adjusted to initial pH values of 2, 3, 4, 5, and 6, treated with 0.06 g MB-CA, magnetically agitated at 25 +/- 1 degrees C for 24 h, and run in three parallel sets. Adsorption capacity rose from 3.65 +/- 1.67 mg/g at pH 2 to 48.52 mg/g at pH 5, then decreased slightly at pH 6. The final pH values reported in the extracted continuation include 6.71 +/- 0.03 and 6.73 +/- 0.01, supporting the authors’ conclusion that MB-CA alkalized initially acidic solutions.
The kinetic experiment fit Cd(II) adsorption better with a quasi-second-order model than a quasi-first-order model:
| Model | Qe calculated | Rate constant | R2 |
|---|---|---|---|
| Quasi-first-order | 68.657 mg/g | 0.111 x 10^-3 min^-1 | 0.868 |
| Quasi-second-order | 75.254 mg/g | 2.273 x 10^-3 min^-1 | 0.915 |
The measured equilibrium adsorption capacity listed in Table 2 was 75.583 mg/g.
In the 30-day soil-culture experiment, MB-CA increased soil pH from 6.7 to 7.1. Compared with the blank control, Cd(II) concentration in contaminated soil decreased from 0.73 mg/kg to 0.40 mg/kg after four samplings. Cadmium speciation shifted toward lower bioavailability: residual Cd increased from 58% to 67%, and exchangeable Cd decreased from 25% to 21%.
Methods (brief)
Pine sawdust was phosphoric-acid impregnated, dried, and pyrolyzed under nitrogen at final temperatures of 450-600 degrees C to prepare modified biochar. The modified biochar was incorporated into a 2% calcium alginate solution, ultrasonically stirred, dropped into 0.2 mol/L CaCl2, washed, cooled, and dried to form MB-CA.
Characterization used SEM-EDS, FTIR, thermogravimetric/differential thermal analysis, and ICP-MS. Batch adsorption tests used Cd(NO3)2 solutions with pH adjusted by HCl and NaOH; kinetic sampling measured Cd(II) by atomic absorption after filtration and dilution. The source reports total Cd/Cd(II) behavior in solution and soil, not cadmium in finished consumer products, fabrics, or fabric protectants.
Implications
Certification: Exclude from occurrence and HMTc benchmark pools. The values describe remediation performance in spiked solution and contaminated soil.
Courses: Useful for remediation modules because it reports pH dependence, kinetic model fit, adsorption capacity, and soil speciation shifts in one compact source.
App: No direct ingredient or product-risk distribution; retain as mitigation-context evidence for cadmium-contaminated agricultural soils.
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Verification notes
This page was built from the PDF text, including the abstract, pH experiment, Table 1 narrative, Table 2 kinetic parameters, soil-culture results, conclusions, and materials/methods. Products and ingredients are intentionally empty because the study does not measure a consumer product or edible crop. The auto-fetch filename’s “fabric-protectants” label is not supported by the paper content.
Page history
The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Description |
|---|---|---|
| 4039d20 | 2026-06-10 | scope: broaden ingest to the full upstream+downstream literature (marine, atmospheric, attribution, exposure, toxicology) — inclusion is the default |