Photocatalytic Degradation Of Caffeine Research Articles

Ceria-decorated zeolite nanocomposite for synergistic adsorption and photocatalytic degradation of caffeine

The adsorption-photocatalytic degradation behaviour of emerging contaminant caffeine, an endocrine-disrupting compound was investigated. The adsorbent material zeolite with porous structure was modified by acid treatment to form a support for attachment of cerium oxide nanoparticles. The photoactive CeO2 was decorated on zeolite (Ceria/zeolite) using the surface modification approach. The physicochemical techniques used for the evaluation of a Ceria/zeolite nanocomposite were performed using XRD, FT-IR, SEM and EDS point mapping, and BET surface area analysis. The effect of caffeine removal was investigated by considering different parameters: pH (3–11), caffeine concentration (10–40 mg/L), and nanocomposite usage (250–750 mg/L). After 90 min of reaction, 68.32 ± 1.38 % adsorption/photocatalytic activity was achieved under dark conditions. UV irradiation increased photocatalysis-mediated removal by 90.63 ± 2.03 %. The process showed the best fit to the PFO model of adsorption kinetics with an R2 value of 0.98. The equilibrium data fitted well to the adsorption isotherm model of Langmuir isotherm, indicating monolayer adsorption. The residual toxicity evaluation revealed 75 % cell viability in the model algal strains. Furthermore, the synthesized nanocomposite photocatalyst can be reused for numerous cycles due to its high caffeine degradation and photocatalytic efficiency. Finally, utilizing HR-LCMS analysis, the probable mechanism of caffeine breakdown is elucidated.

Photocatalytic degradation of caffeine using metal ion-modified pillared interlayered clays and H2O2 under UV radiation

Caffeine (CAF) is a widely used stimulant in beverages, foods, and drugs. Extreme usage of this popular molecule can create caffeine pollution for water sources. A photocatalytic method was developed to degrade CAF in water. The pillared interlayered clays (PILCs) were used as the photocatalytic material. Zeolite, a type of clay, was used to prepare PILCs. The operational parameters, such as reaction time, CAF concentrations, H2O2, and PILCs amounts, were examined to obtain the highest removal percentages. The removal rates reached 97%, 100%, and 100% in 120, 180, and 300 min, respectively, using 1.0 mL H2O2 and 1.0 g of Fe-Ti-PILC for 50.0 mg/L CAF under UV exposure. The experiments were carried out in batch method, and RP-HPLC was used to find the remaining CAF concentrations.

Porous vs. Nanotubular Anodic TiO2: Does the Morphology Really Matters for the Photodegradation of Caffeine?

Herein, the preparation of nanotubular and porous TiO2 structures (TNS) is presented for photocatalytic applications. Different TNS were prepared in three different types of glycerol- and ethylene glycol-based electrolytes on a large area (approx. 20 cm2) via anodization using different conditions (applied potential, fluoride concentration). Morphology, structure, and optical properties of TNS were characterized by Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD), and Diffuse Reflectance Spectroscopy (DRS), respectively. All TNS possess optical band-gap energy (EBG) in the range from 3.1 eV to 3.2 eV. Photocatalytic degradation of caffeine was conducted to evaluate the efficiency of TNS. Overall, nanotubular TiO2 possessed enhanced degradation efficiencies (up to 50% degradation) compared to those of porous TiO2 (up to 30% degradation). This is due to the unique properties of nanotubular TiO2, e.g., improved incident light utilization. As the anodization of large areas is, nowadays, becoming a trend, we show that both nanotubular and porous TiO2 are promising for their use in photocatalysis and could be potentially applicable in photoreactors for wastewater treatment. We believe this present work can be the foundation for future development of efficient TiO2 nanostructures for industrial applications.

Photocatalytic degradation of caffeine in a slurry reactor with intermittent UV irradiation: optimization and response surface modelling

Abstract This study focusses on the photocatalytic degradation of caffeine (CAF), a stimulating drug and environmental contaminant that poses a threat to humans and the environment. The effect of operating parameters such as CAF initial concentration (5–20 mg/L), catalyst dosage (0.1–0.9 g/L) and pH (3.0–9.0) were explored in detail. The experimental results showed the maximum CAF and chemical oxygen demand (COD) removals of 87.2% and 66.7% respectively. The optimized parameters were: CAF initial concentration – 5 mg/L, catalyst dosage – 0.5 g/L and pH – 7.2. The photocatalytic degradation of CAF followed pseudo-first order kinetics. The obtained experimental data were analysed with response surface methodology (RSM) using Design Expert Software.

Modified TiO2 for photocatalytic removal of organic pollutants in water

In this work, TiO2/Ti2O3 composite catalysts were prepared by simple one-step thermal treatment method at various temperatures. The morphology and structure of as-prepared samples have been examined by XRD, TGA and SEM. The XRD characterization results revealed three-phase mixture in sample treated at 550°C, while at 650°C phase transformation from TiO2 anatase to TiO2 rutile and particle size growth was observed. Moreover, the effect of treatment temperature on the photocatalytic degradation of caffeine was evaluated under UV light irradiation. Results indicated that TiO2/Ti2O3-550 exhibited higher catalytic activity than others achieving complete caffeine removal in 60 min.

Photocatalytic degradation of caffeine and E. coli inactivation using silver oxide nanoparticles obtained by a facile green co-reduction method

In this study, silver oxide nanoparticles (Ag2O-NPs) were synthesized from silver nitrate using green amaranth leaf extract as a reducing agent. The degradation of caffeine and inactivation of Escherichia coli (E. coli) by Ag2O-NPs was studied under compact fluorescent lamp illumination irradiation. Apart from that, the antibacterial and antioxidant activities of Ag2O-NPs were also examined. Synthesized Ag2O-NPs were shaped like monodispersed husk, and cubic structured with surface area, and average particle size was detected to be 100.21 (m2/g) and 81 nm, respectively. Antioxidant efficacy of the Ag2O-NPs was evaluated using 1, 1-diphenyl-2-picrylhydrazyl, and 91% inhibition was achieved with 100 µg Ag2O-NPs. Cell viability assay demonstrated that Ag2O-NPs showed less cytotoxicity for human embryonic kidney (HEK 293) cells. The bacteriocidic propensity of Ag2O-NPs was examined against the S. aureus and P. aeruginosa by disk diffusion, minimum inhibitory concentration (MIC), live and dead assay. It was observed that the NPs have a higher bactericidal effect on Gram-negative as compared to Gram-positive bacteria. Up to 96%, photocatalytic inactivation of E. coli was achieved using 30 µg/mL of NPs. Photocatalytic degradation of caffeine (50 ppm initial concentration) was observed to be 99% at pH 9 in 15 h using 50 mg/L of Ag2O NPs. These results indicate that Ag2O NPs can be employed in environmental applications like harmful bacteria inactivation and organic pollutants degradation.

Reusability in visible light of titanate nanotubes for the removal of organic pollutants: role of calcination temperature

ABSTRACT Titanate nanotubes (NTs) were synthesised by the hydrothermal method and later calcined at temperatures between 100–500°C. The calcined NTs were characterised and evaluated in the physicochemical adsorption of the safranin dye and photocatalytic degradation of caffeine. The materials calcined at low temperatures displayed a tubular structure and the H2Ti3O7 crystalline phase, which was transformed into anatase nanoparticles at 400°C. The NTs treated at 100°C showed the highest adsorption capacity (94%). Safranin was adsorbed through an ion-exchange mechanism, following the Langmuir isotherm and a pseudo-second-order kinetic model. While NTs calcined at lower temperatures were better for adsorption, the photocatalytic degradation of caffeine increased in samples calcined at higher temperatures with a maximum removal of 72%. The photocatalytic behaviour of the NT samples confirmed that the crystalline anatase structure in conjunction with structural OH groups enhanced the photocatalytic activity. The addition of isopropanol as a scavenger confirmed the important role played by the •OH radicals in the photocatalytic process. NTs calcined at 300°C were efficient for both adsorption and photocatalytic processes. Due to its efficiency, this sample was reused after dye adsorption for the photocatalytic degradation of caffeine under visible light due to its enhanced absorbance in the visible region. This research work shows the potential of NTs for wastewater purification.

Visible-light-induced self-cleaning functional fabrics using graphene oxide/carbon nitride materials

Functional cotton fabrics consisting of neat polymeric carbon nitride (CN) combined with graphene oxide (GO) were prepared by a simple impregnation route. The CN-based coated fabrics were characterized by several techniques. The self-cleaning efficiency of these hybrid fabrics was assessed in the photocatalytic degradation of caffeine and rhodamine B (RhB) in aqueous solutions under visible light-emitting diodes (LEDs). It was demonstrated that GO, even if present at a low % v/v(0.1%), confers to the coated fabrics higher photocatalytic efficiency for degradation of both organic pollutants in comparison with CN coated fabrics. The photoluminescence quenching observed on coated GO/CN fabrics suggests an electron transfer between the CN and GO phases. In general, both coated CN and GO/CN fabrics show high stability after three uses with intensive washes between each run. The antibacterial activity against Escherichia coli using CN and GO/CN colloids was assessed. Results showed >99.2% of E. coli inactivation with CN-based colloids activated by visible radiation.

Photocatalytic Degradation of Caffeine in a Solar Reactor System

AbstractIn this paper, solar photodegradation of caffeine in aqueous solution was studied, this organic compound is the most consumed stimulant around the world. The degradation experiments were carried outdoors in a solar reactor and Evonik-Degussa P25 TiO2was used as catalyst. The photochemical and photocatalytic effect were tested in aqueous solutions of caffeine. Experimental results indicate that the organic compound is easily degraded over a very short period of time using 0.5 g L-1of catalyst. The kinetic analysis indicates that the initial reaction rate of caffeine is described by the LH-HW model. However, the original compound cannot be mineralized very fast, caffeine is converted to other organic compounds with a longer lifetime before the mineralization, converting caffeine CO2and water.

Synthesis, characterization and efficient photocatalytic activity of novel Ca/ZnO-Al2O3 nanomaterial

In this paper Ca/ZnO-Al2O heterojunction photocatalysts was prepared in two steps. First, Zn-Al-CO3 layered double hydroxides (LDH) precursor was synthesized by co-precipitation method. Second, Ca at various content (1, 3 and 5 wt%) was incorporated on LDH structure using solid state reaction at 500 °C. Samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) coupled with energy dispersive X-ray analysis (EDX) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The photocatalytic activity of the catalysts was evaluated in the degradation of caffeine as a model of pharmaceutical pollutants in aqueous solutions under UV irradiation. The Ca-doped ZnO-Al2O3 materials showed significantly higher photocatalytic activity compared to undoped, pure ZnO and standard Degussa P-25 titanium dioxide. This behavior was attributed to increased adsorption capacity, crystallinity of the catalysts and surface morphology. The maximum degradation rate (98.5 ± 0.5%) was obtained in 70 min by 5%Ca-ZnO-Al2O3 photocatalyst. Furthermore, the effect of different parameters such as irradiation time, photocatalyst amount, caffeine concentration, initial pH and reuse on the resulting photocatalytic activity was investigated. The photocatalytic degradation of caffeine was increased with an increase in the Ca-loaded amounts. This work demonstrates that the prepared Ca doped ZnO-Al2O3 nanoparticles are promising material for the photocatalytic degradation of pharmaceuticals pollutants.

Photocatalytic degradation of caffeine by ZnO-ZnAl2O4 nanoparticles derived from LDH structure

In this research, ZnO-ZnAl2O4 mixed phases were prepared by calcination of Zn-Al-CO3 layered double hydroxides (LDH) precursors. Firstly, a series of Zn-Al-CO3 LDH were synthesized at different Zn/Al molar ratios (r=1, 3 and 5) and then calcined at different temperatures (300, 400, 500, 600, 800 and 1000°C) for 6h. The materials were characterized by XRD, FTIR, TGA/DTA, ICP-AES and TEM. The photocatalytic activity of the samples was evaluated for the degradation of caffeine as a model pharmaceutical pollutant in aqueous solution under UV irradiation. The effect of the Zn/Al molar ratio, calcination temperature and initial pH of aqueous solution was investigated. The experimental results show that the sample obtained from the molar ratio of 3 and calcined at 500°C with a large capacity of adsorption obtained by reconstruction process was photocatalytically much higher than standard Degussa P-25 titanium dioxide.

Effect of dopants on the structure of titanium oxide used as a photocatalyst for the removal of emergent contaminants

Abstract Photocatalysts composed of titanium dioxide modified with B, F, N and P have been synthesized, characterized and applied to the degradation of caffeine, diclofenac, ibuprofen and salicylic acid. The modified TiO2 samples were prepared by the sol–gel technique starting from titanium(IV) isopropoxide and using H3BO3, NH4F, N(C2H5OH)3 and H3PO4 as precursors of the modifiers, with the content varying between 0 and 5 wt%. Structural characterization was based on nitrogen physisorption at −196 °C, powder X-ray diffraction (PXRD), simultaneous thermogravimetric/differential thermal analysis (TG/DTA) and X-ray photoelectron spectroscopy (XPS). The structural properties of the modified TiO2 solids were significantly different depending on the nature and amount of modifiers and the calcination temperature. TiO2 in the anatase phase was obtained in all cases and was stable upon calcination at 400 °C. The photocatalytic degradation of caffeine, diclofenac, ibuprofen and salicylic acid by modified TiO2 was investigated under ultraviolet irradiation at 25 °C. The photocatalytic degradation behavior followed the order: caffeine > diclofenac = ibuprofen > salicylic acid. B-doped TiO2 was the most efficient catalyst in the degradation of these selected emerging contaminants.

Photocatalytic degradation of caffeine: Developing solutions for emerging pollutants

The photocatalytic degradation of the psychoactive substance caffeine was studied using composites prepared with multi-walled carbon nanotubes and three different TiO2 materials: one synthesized by a modified sol–gel method and two others obtained from Evonik and Sigma–Aldrich. These materials were characterized by several techniques (e.g., DRIFT, XRD, N2 adsorption–desorption isotherms, TEM, SEM).The tested materials increased the caffeine degradation rate and the oxygenated groups created by acid treatment on the surface of the carbon nanotubes were crucial for the photocatalytic activity of all prepared composites. In addition, the photocatalytic activity of TiO2 from Sigma–Aldrich markedly increased with the addition of functionalized carbon nanotubes, which seems to be related with the larger TiO2 crystallite sizes and the better contact of these TiO2 particles with carbon nanotubes.Selective trapping of photogenerated holes and radicals by EDTA and tert-butanol shows that photogenerated holes are crucial on the photodegradation pathway but free radicals produced by photoexcited electrons do also participate in the mechanism and seem to be responsible for the higher activity observed for composites prepared with functionalized carbon nanotubes and TiO2 from Sigma–Aldrich in comparison to TiO2 alone. Films prepared with these composites revealed higher photocatalytic activity than films of TiO2 from Evonik.