Environmental remediation by an integrated microwave/UV illumination method. V. Thermal and nonthermal effects of microwave radiation on the photocatalyst and on the photodegradation of rhodamine-B under UV/Vis radiation.

Environmental science & technology · 2003 · Benefit · Low evidence

← Research stream

BenefitLow evidencePaper 3748

Study snapshot

PublicationEnvironmental science & technology · 2003

Study typein_vitro

Reported directionBenefit

Evidence ratingLow

Abstract

The photocatalyzed degradation (PD) of the cationic rhodamine-B (RhB) dye was examined in aqueous TiO2 dispersions using UV/Vis illumination assisted by microwave radiation (PD/MW). The initial degradation by the PD/MW method is compared to the PD method and to the thermally assisted PD method using conventional heating (PD/TH). Total organic carbon (TOC) assays show that the efficiency of complete mineralization of the dye follows PD/MW > PD/TH > PD > MW. In all cases, microwave radiation alone had no effect on the loss of TOC. The degradation involving microwave radiation was especially efficient when coupled to UV irradiation. By contrast, the extent of degradation of RhB involving suitable excited states through visible irradiation of the dye was rather inefficient when coupled to microwave radiation. Contact angle measurements on the TiO2 photocatalyst particles indicate that microwave radiation also causes an increase in the hydrophobic character of the TiO2 surface, with consequences on the adsorption mode of the dye substrate and thus on the overall mechanism of degradation. Deethylated RhB intermediates were identified by an electrospray ESI ionization mass spectral technique in the positive ion mode and subsequently confirmed by HPLC/absorption spectroscopy. Computer simulations led to estimates of frontier electron densities of all atoms of the RhB structure, affording inferences as to the position of radical attack on RhB. The nitrogen atoms of the dye were all converted to NH4+ ions. The major difference between the thermally assisted PD/TH method and the microwave-assisted PD/MW method showed that nonthermal effects from the microwave radiation impact significantly on the nature of the photocatalyst surface. These effects led to a more efficient photodegradation and mineralization of the dye substrate.

Machine Enhanced Logic

AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typein_vitro

Effect directionbenefit

PopulationNot supplied

Sample sizeNot supplied

Exposuremicrowave

Evidence strengthLowConfidence: 74% · Peer reviewed: yes

Main findings

In aqueous TiO2 dispersions, UV/Vis photocatalysis assisted by microwave radiation (PD/MW) produced greater TOC mineralization efficiency than thermally assisted photocatalysis (PD/TH), photocatalysis alone (PD), or microwave radiation alone (MW). Microwave radiation alone had no effect on TOC loss, and the authors report that nonthermal microwave effects altered TiO2 surface properties (increased hydrophobic character), contributing to more efficient photodegradation/mineralization under UV irradiation.

Outcomes measured

Photocatalyzed degradation of rhodamine-B in aqueous TiO2 dispersions
Total organic carbon (TOC) mineralization efficiency
TiO2 photocatalyst surface hydrophobicity (contact angle)
Identification of degradation intermediates (ESI-MS, HPLC/absorption)
Conversion of dye nitrogen to NH4+ ions

Limitations

Microwave exposure parameters (e.g., frequency, power, dosimetry) not provided in the abstract
In vitro/chemical system; no human/animal health outcomes reported
Sample size and replication details not stated

View raw extracted JSON

{
  "study_type": "in_vitro",
  "exposure": {
    "band": "microwave",
    "source": "laboratory microwave radiation (assisting UV/Vis photocatalysis)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "Photocatalyzed degradation of rhodamine-B in aqueous TiO2 dispersions",
    "Total organic carbon (TOC) mineralization efficiency",
    "TiO2 photocatalyst surface hydrophobicity (contact angle)",
    "Identification of degradation intermediates (ESI-MS, HPLC/absorption)",
    "Conversion of dye nitrogen to NH4+ ions"
  ],
  "main_findings": "In aqueous TiO2 dispersions, UV/Vis photocatalysis assisted by microwave radiation (PD/MW) produced greater TOC mineralization efficiency than thermally assisted photocatalysis (PD/TH), photocatalysis alone (PD), or microwave radiation alone (MW). Microwave radiation alone had no effect on TOC loss, and the authors report that nonthermal microwave effects altered TiO2 surface properties (increased hydrophobic character), contributing to more efficient photodegradation/mineralization under UV irradiation.",
  "effect_direction": "benefit",
  "limitations": [
    "Microwave exposure parameters (e.g., frequency, power, dosimetry) not provided in the abstract",
    "In vitro/chemical system; no human/animal health outcomes reported",
    "Sample size and replication details not stated"
  ],
  "evidence_strength": "low",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "microwave radiation",
    "photocatalysis",
    "TiO2",
    "UV/Vis",
    "rhodamine-B",
    "total organic carbon",
    "mineralization",
    "nonthermal effects",
    "surface hydrophobicity",
    "environmental remediation"
  ],
  "suggested_hubs": [
    {
      "slug": "engineering",
      "weight": 0.78,
      "reason": "Laboratory study using microwave radiation to enhance UV/Vis photocatalytic degradation/mineralization of a dye in aqueous TiO2 dispersions."
    }
  ]
}

AI can be wrong. Always verify against the paper.

AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1021/es030326i
PubMed: 14717200

Read the original paper →

Related papers

← Back to the Research Library