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Catalytic degradation of tartrazine in the presence of Oxone® activated by a catalyst constituted of cobalt supported on a nanocomposite of smectite with chitosan-derived carbon was investigated. The catalyst was synthesized using cobalt impregnation followed by carbonization at 773 K in an inert atmosphere. The synthesized catalyst was previously fully characterized using appropriate characterization methods, including XRPD, XPS, FTIR, HR-TEM, and low-temperature N2-physisorption analysis. The catalytic experiments were performed by varying different experimental parameters (dye concentration, Oxone® concentration, temperature, and initial pH of the reaction solution). The kinetic and thermodynamic parameters were estimated from the experimental results. The kinetics data showed the best fit with the pseudo-first-order kinetics model. The activation energy of the investigated degradation process was calculated according to the Arrhenius equation. The catalyst showed excellent performance at low temperatures even at 298 K, and in the wide range of pH values.

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.

Mixed Al, Fe pillared clay (AlFePILC) was synthesized from Na-exchanged Wyoming clay (Na-Wy) rich in montmorillonite. In the pillaring process Na-Wy was modified with a mixed intercalating (Al, Fe) solution with molar ratio of Fe3+/(Al3++Fe3+) = 10%. The obtained AlFePILC was impregnated with cobalt using the incipient wetness impregnation method, dried at 110 ºC and calcined at 450 ºC (Co-AlFePILC). Co-AlFePILC was tested as a catalyst in catalytic oxidation of tartrazine in the presence of Oxone®. Decolorization was monitored at wavelength =426 nm, while degradation of aryl groups was followed at =257 nm using UV-Vis spectroscopy. The influence of the mass of the catalyst on degradation process was followed in the mass range from 10 mg to 50 mg at 30 °C. It was found that mass increase was beneficial for the decolorization rate. The effect of temperature was investigated from 30 ºC to 60 ºC. The decolorization was over 90% after only 10 minutes for the temperature of 60 ºC, while with the temperature decrease, the decolorization rate decreased. Co-AlFePILC was found to be an efficient catalyst in degradation of tartrazine in the presence of Oxone®.

In this work smectite pillared with mixture of aluminium and cobalt poly(hydroxo metal) cations (Al,Co-PILC) was synthesized and tested as catalyst in degradation of food dye tartrazine by peroxymonosulfate. The Al,Co-PILC was obtained using a common procedure consisting of the following steps: grinding, sieving, Na exchange, intercalation, drying and calcination. Co2+ to (Al3++Co2+) molar ratios in the pillaring solution was 10%. Catalytic tests were carried out in a semibatch reactor under stirring and constant temperature maintained by circulation of thermostatic fluid using Julabo MC 4 heating circulator. Initial dye concentration was 50 ppm in the presence of excess of peroxymonosulfate. Decolorization of tartrazine solution was monitored using UV-Vis spectrophotometry at max= 426 nm. The influence of the mass of the catalyst and reaction temperature was investigated. Catalyst mass and temperature increase were beneficial for dye degradation rate. The catalytic process at 30 ºC reached 97% for 120 min and besides decolorization included further degradation of products of tartrazine oxidation. At 50 ºC complete decolorization occurred for only 30 min. This work showed that application of smectite pillared with mixture of aluminium and cobalt poly(hydroxo metal) cations as peroxymonosulfate activators for degradation of water pollutants is very promising.

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.

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.

Degradation of tartrazine in presence of cobalt activated Oxone® (potassium peroxymonosulfate) was investigated. Aluminium pillared clay acted as a support for catalytically active Co2+. Oxone® was a precursor of SO4˙ˉ radical anions. Along with decolorization of tartrazine solution, the degradation of tartrazine and formation of oxidation products was monitored using UV-Vis spectroscopy. Quantum chemical calculations were performed in order to predict UV-Vis spectra. Different models were tested, and the results of calculation have shown that the combination of TPSS-D3 method and aug-cc-pVDZ basis set is quite satisfactory level of theory. The experimentally obtained peaks that arose during degradation were identified using this method.

In this work aluminum pillared clay impregnated with cobalt (CoAP) was tested as catalyst in the degradation of azo-dye tartrazine in the presence of potassium peroxymonosulfate (Oxone®). Aluminum pillared clay was synthesized -exchanged clay from Wyoming, USA (Na-Wy) using common procedure. The influence of Oxon®/catalyst ratio on catalytic performance was investigated. The cobalt impregnated pillared montmorillonite was found to be promising catalyst for dye decolorization.

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.