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Chitosan (Ch)-derived from biowaste along with smectite, an abundant clay mineral, were used in a low-cost and eco-friendly synthesis of a new type of catalyst. Nanocomposite catalysts constituted of Co supported on smectite with chitosan-derived carbon loading were obtained using an impregnation‑carbonization procedure and denoted as Co/cCh-S-T (T stands for applied carbonization temperature). The carbonization was performed in the temperature range from 400 °C to 700 °C in the flow of N2 providing inert atmosphere. The temperature of 500 °C was found to be the most suitable for catalyst synthesis regarding catalytic performance in a peroxymonosulfate activated degradation of tartrazine. The incorporation of carbonized chitosan structure within the interlamellar space of the smectite was confirmed using X-ray powder diffraction. The high-resolution transmission electron microscopy confirmed a layered structure of nanocomposites characteristic for smectite, as well as the presence of small spherical cobalt containing nanoformations (confirmed by energy dispersive X-ray spectroscopy) well dispersed within structure. The existance of cobalt in the CoII and CoIII oxidation state was proven by X-ray photoelectron spectroscopy. The Co/cCh-S-500 catalyst was proven to be stable and efficient after 5 consecutive cycles. This work showed that nanocomposite Co-catalysts, based on smectite and biowaste-derived carbon, as peroxymonosulfate activators exhibited a very promising performance in the degradation of water pollutants. Supplementary material: [https://cherry.chem.bg.ac.rs/handle/123456789/5671]

In this work cobalt-supported carbon-smectite catalyst was synthesized and tested as peroxymonosulfate (in form of Oxone®) activator in the degradation of food dye tartrazine. The incipient wetness impregnation method was used to introduce cobalt species into chitosan-smectite biocomposite. The impregnated sample was carbonized in a tube furnace at 500 ºC in a nitrogen atmosphere. The obtained catalyst was characterized by FTIR spectroscopy and N2 physisorption. The FTIR spectra indicated the presence of bands characteristic for carbonaceous structures. It was observed that the presence of cobalt has a significant impact on the textural properties of the resulting cobalt-supported carbon-smectite catalyst. Catalytic tests were performed in 50.0 mg dm-3 tartrazine solution using 10 mg of catalyst in the presence of 0.130 mmol Oxone®. As the first step in catalytic degradation of tartrazine solution, decolorization was monitored using UV-Vis spectrophotometry at λmax= 426 nm. The catalytic process was fast at 30 ºC and besides decolorization included further degradation of products of tartrazine oxidation. After 60 minutes of reaction, the degree of decolorization reached 97%. The influence of the initial pH of reaction solution on catalytic efficiency was tested.

Heterogneous Fenton-like reaction is one of the most efficient solutions for the degradation of organic pollutants in water. A variant of this reaction involves the application of Oxone reagent, based on potassium peroxymonosulfate. Oxone, in conjunction with cobalt, is the source of sulfate radicals. These radicals are very efficient oxidants because of their high standard reduction potential at neutral pH. In this work Co-impregnated Al-pillared clay (CoAP2) was used as heterogeneous catalyst in the degradation of Tartrazine azo-dye in aqueous solutions. For this purpose, Namontmorillonite source clay from Wyoming, USA, with particle diameters of up to 2×10-6 m was submitted to pillaring with aluminium (Keggin ions) and subsequent impregnation with Co(NO3)2 followed by calcination. Morphological and textural characterization as well as phase and chemical characterization were performed on the obtained material. Catalytic degadation of Tartrazine using CoAP2 and Oxone was investigated with respect to reaction temperature in the range from 30–70 °C and monitored using UV-Vis spectroscopy. The obtained spectra indicated that solution decolorization was efficient. Increasing temperature increased decolorization efficiency, and led to the degradation of the dye, the formation and subsequent disappearance of different reaction products. The catalyst showed to be stable under investigated conditions.

Magnetic beads were obtained by dropping a solution of sodium alginate containing magnetite particles into a CaCl2 solution. TiO2anatase particles were synthetized by a sol-gel method at low temperature (75 °C), and were supported on magnetic beads to obtain the magnetic photocatalyst, MC. Magnetite particles and magnetic photocatalyst were characterized by nitrogen adsorption (BET, surface area), their morphology observed by scanning electronic microscopy (SEM) and TiO2 phase was analyzed by means of Raman spectroscopy. The photocatalytic activity of MC was evaluated on tartrazine degradation, highly used in food industry, at two different concentrations. Finally, MC stability was evaluated by reusability assays in several subsequent cycles. Results showed a good photocatalytic response for tartrazine degradation, especially at low concentration, easy recuperation and appropriate perform in the reusability of MC. RESUMENEn el presente trabajo se han obtenido perlas magnéticas mediante la adición de una solución de alginato de sodio conteniendo partículas de magnetita a una solución de CaCl2, las cuáles fueron utilizadas como soporte de TiO2. Las partículas de TiO2 en fase anatasa, obtenidas por el método sol-gel a baja temperatura (75 °C), fueron soportadas en las perlas magnéticas para obtener el fotocatalizador magnético, CM. La superficie específica BET del núcleo de magnetita y el fotocatalizador magnético fueron obtenidas por adsorción de N2, la morfología de las partículas fueron observadas por microscopía electrónica de barrido (SEM) y la fase TiO2fue analizada mediante espectroscopía Raman. La actividad fotocatalítica de CM fue evaluada en la degradación del colorante tartrazina, muy utilizado en la industria alimenticia, a dos concentraciones diferentes. Finalmente, la estabilidad del catalizador fue evaluada mediante ensayos de la re-usabilidad en varios ciclos posteriores. Los resultados mostraron que la fase anatasa soportada en las partículas magnéticas presentan buena actividad fotocatalítica en la de degradación de tartrazina, principalmente cuando la concentración del colorante es baja, y que pueden ser fácilmente recuperados y re-utilizados en varios ciclos con una moderada pérdida en la eficiencia fotocatalítica.

Magnetic beads were obtained by dropping a solution of sodium alginate containing magnetite particles into a CaCl2 solution. TiO2 anatase particles were synthetized by a sol-gel method at low temperature (75 °C), and were supported on magnetic beads to obtain the magnetic photocatalyst, MC. Magnetite particles and magnetic photocatalyst were characterized by nitrogen adsorption (BET, surface area), their morphology observed by scanning electronic microscopy (SEM) and TiO2 phase was analyzed by means of Raman spectroscopy. The photocatalytic activity of MC was evaluated on tartrazine degradation, highly used in food industry, at two different concentrations. Finally, MC stability was evaluated by reusability assays in several subsequent cycles. Results showed a good photocatalytic response for tartrazine degradation, especially at low concentration, easy recuperation and appropriate perform in the reusability of MC. En el presente trabajo se han obtenido perlas magnéticas mediante la adición de una solución de alginato de sodio conteniendo partículas de magnetita a una solución de CaCl2, las cuáles fueron utilizadas como soporte de TiO2. Las partículas de TiO2 en fase anatasa, obtenidas por el método sol-gel a baja temperatura (75 °C), fueron soportadas en las perlas magnéticas para obtener el fotocatalizador magnético, CM. La superficie específica BET del núcleo de magnetita y el fotocatalizador magnético fueron obtenidas por adsorción de N2, la morfología de las partículas fueron observadas por microscopía electrónica de barrido (SEM) y la fase TiO2 fue analizada mediante espectroscopía Raman. La actividad fotocatalítica de CM fue evaluada en la degradación del colorante tartrazina, muy utilizado en la industria alimenticia, a dos concentraciones diferentes. Finalmente, la estabilidad del catalizador fue evaluada mediante ensayos de la re-usabilidad en varios ciclos posteriores. Los resultados mostraron que la fase anatasa soportada en las partículas magnéticas presentan buena actividad fotocatalítica en la de degradación de tartrazina, principalmente cuando la concentración del colorante es baja, y que pueden ser fácilmente recuperados y re-utilizados en varios ciclos con una moderada pérdida en la eficiencia fotocatalítica. Fil: Heredia, Carla Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones Para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones Para la Industria Química; Argentina Fil: Sham, Edgardo Ling. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones Para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones Para la Industria Química; Argentina Fil: Farfan Torres, Elsa Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones Para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones Para la Industria Química; Argentina