Efficient elimination of caffeine from water using Oxone activated by a magnetic and recyclable cobalt/carbon nanocomposite derived from ZIF-67

To eliminate caffeine, one of the most common pharmaceuticals and personal care products, from water, Oxone (peroxymonosulfate salt) was proposed to degrade it. To accelerate the generation of sulfate radicals from Oxone, a magnetic cobalt/carbon nanocomposite (CCN) was prepared from a one-step carb...

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Bibliographic Details
Published in:Dalton transactions : an international journal of inorganic chemistry 2016-01, Vol.45 (8), p.3541-3551
Main Authors: Lin, Kun-Yi Andrew, Chen, Bo-Chau
Format: Article
Language:English
Subjects:
Caffeine
Caffeine - chemistry
Caffeine - isolation & purification
Carbon
Carbon - chemistry
Catalysts
Cobalt
Cobalt - chemistry
Degradation
Hydrogen-Ion Concentration
Nanocomposites - chemistry
Porosity
Radicals
Sulfates
Sulfuric Acids - chemistry
Surface Properties
Temperature
Water - chemistry
Water Pollutants, Chemical - chemistry
Water Pollutants, Chemical - isolation & purification
Zeolites - chemistry
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Summary:To eliminate caffeine, one of the most common pharmaceuticals and personal care products, from water, Oxone (peroxymonosulfate salt) was proposed to degrade it. To accelerate the generation of sulfate radicals from Oxone, a magnetic cobalt/carbon nanocomposite (CCN) was prepared from a one-step carbonization of a cobalt-based Zeolitic Imidazolate Framework (ZIF-67). The resultant CCN exhibits immobilized cobalt and increased porosity, and can be magnetically manipulated. These characteristics make CCN a promising heterogeneous catalyst to activate Oxone for caffeine degradation. Factors affecting the caffeine degradation were investigated, including CCN loading, Oxone dosage, temperature, pH, surfactants, salts and inhibitors. A higher CCN loading, Oxone dosage and temperature greatly improved the caffeine degradation by CCN-activated Oxone. Acidic conditions were also preferable over basic conditions for caffeine degradation. The addition of cetyltrimethylammonium bromide (CTAB) and NaCl both significantly hindered caffeine degradation because bromide from CTAB and chloride from NaCl scavenged sulfate radicals. Based on the effects of inhibitors (i.e., methanol and tert-butyl alcohol), the caffeine degradation by CCN-activated Oxone was considered to primarily involve sulfate radicals and, less commonly, hydroxyl radicals. The intermediates generated during the caffeine degradation were analyzed using GC-MS and a possible degradation pathway was proposed. CCN was also able to activate Oxone for caffeine degradation for multiple cycles without changing its catalytic activity. These features reveal that CCN is an effective and promising catalyst for the activation of Oxone for the degradation of caffeine.
ISSN:1477-9226
1477-9234
DOI:10.1039/c5dt04277a