He et al. 2023 - Ti3C2/UiO-66-NH2 photoreduction of Cr(VI)
He and colleagues synthesized Ti3C2/UiO-66-NH2 composites and tested their visible-light photoreduction of synthetic Cr(VI) as potassium dichromate. This is primary remediation/testing evidence, not occurrence evidence. The routeable numbers are the potassium dichromate challenge concentration, catalyst loading, removal time, and first-order kinetic rate for the optimized 10 wt% Ti3C2 composite.
Key numbers
Cr(VI) photoreduction setup
Photoreduction was conducted at room temperature under visible light irradiation from a 300 W xenon lamp with 420 nm < lambda < 780 nm. The assay used 10 mg photocatalyst added to 40 mL K2Cr2O7 solution at 100 mg/L and pH 2. The suspension was stirred in the dark for 30 minutes, then irradiated for 40 minutes. Two milliliters of suspension were collected every 10 minutes, filtered through a 0.22 micrometer membrane, and analyzed by the diphenylcarbazide colorimetric method at 542 nm.
For the calibration curve, the authors prepared a 1000 mg/L potassium dichromate mother solution at pH 2, then prepared 0, 20, 40, 60, 80, and 100 ppm potassium dichromate standards.
Catalyst ratios and removal
The Ti3C2/UiO-66-NH2 composites were named by Ti3C2 content:
| Composite | Ti3C2 content |
|---|---|
| 1-T/U | 5 wt% |
| 2-T/U | 10 wt% |
| 3-T/U | 15 wt% |
| 4-T/U | 20 wt% |
The optimized 2-T/U composite, containing 10 wt% Ti3C2, removed 100% Cr2O7(2-) in 40 minutes. Its observed photoreduction rate was 0.0871 min^-1, about 2.6 times higher than the pure UiO-66-NH2 rate.
The authors report that catalyst dose and substrate concentration were also examined in supplemental Figure S5: higher Ti3C2/UiO-66-NH2 dose improved removal efficiency, while removal decreased as Cr(VI) concentration increased above 100 ppm.
Stability and mechanism
The 2-T/U composite retained performance in recycling experiments and maintained PXRD patterns after photoreduction. The authors attribute the improved rate to a heterojunction structure between Ti3C2 and UiO-66-NH2: Ti3C2 acts as an electron sink, and the interfacial interaction/depletion layer suppresses charge recombination after light irradiation.
Methods (brief)
Ti3C2 MXene was synthesized by etching Ti3AlC2 powder with HF. UiO-66-NH2 was synthesized by a solvothermal method. Ti3C2/UiO-66-NH2 composites were prepared by in situ solvothermal growth with adjustable Ti3C2 content. The materials were characterized by PXRD, SEM, EDS/mapping, XPS, FT-IR, N2 sorption, UV-vis diffuse reflectance, Mott-Schottky plots, transient photocurrent, photoluminescence, and electrochemical impedance spectroscopy. Cr(VI) removal was calculated as (1 - C/C0) x 100%.
Implications
Certification: This source does not support HMTc product or ingredient standards. It tests synthetic K2Cr2O7 solution at pH 2 under laboratory irradiation.
Courses: Useful for explaining Cr(VI) reduction kinetics and the difference between an occurrence result and a remediation challenge. The source measures treatment performance, not baseline water contamination.
App: Route to Cr(VI), chromium, titanium/materials, and testing/remediation context. Do not treat the 100 mg/L potassium dichromate challenge as drinking-water occurrence.
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Verification notes
The PDF has author attribution and DOI 10.3390/catal13050876; no DOI conflict was observed. The source reports synthetic potassium dichromate treatment experiments, not natural water, food, ingredient, or product concentrations. Titanium is part of the catalyst material, not a contaminant result.
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 |
|---|---|---|
| c1aef38 | 2026-06-02 | audit-queue: hamid2021-bacterial-plant-biostimulants-review → audited-promote |