Application of the Zimm-Bragg Model to the Removal of Azo Dyes with Pectin

In this work, the ability of pectin (Pec) to remove direct red 80 (DR80), Congo red (CR), methyl orange (MO), and methyl red (MR) was studied. The removal percentages under adequate pH and ionic strength conditions were as follows: DR80 (99.5%), CR (99.8%), MO (88.6%), and MR (68%), showing that this methodology is efficient to remove azo dyes. The proposed method included the addition of native Pec to the dye aqueous solution and the formation of a gel that occurred when a calcium salt solution was added. This gel retains the molecules adsorbed onto the molecular surface of Pec through hydrogen bonds and electrostatic and hydrophobic interactions. To our knowledge, it is the first time that the Zimm-Bragg model is used to describe the removal of azo dyes with native Pec. This model includes two parameters: K u (nucleation constant), which is related to the tendency exerted by a dye molecule attached to the Pec to bind to other molecules present in the aqueous phase, and U (cooperativity parameter), which determines the aggregation capacity of the dye molecules already attached to the Pec. This model fits the experimental isotherms very well, suggesting that Pec binds single molecules and dye aggregates. The obtained results in the values of K u ranged from 922 mol/kg (MR) to 1,157,462 mol/kg (CR), and U varied from 2.51 (MR) to 169.19 (MO). These results suggest that the use of Pec is a viable option to remove azo dyes from aqueous effluents and that the Zimm-Bragg model fits adequately the isotherms of dyes that have a high tendency to form aggregates.

A New Three-Component Photo-Initiating System for Visible Light Recording of Volume Holograms with Single-Pulsed Laser

Versatile substituted electron-deficient trichloromethylarenes can easily be synthesized and combined with a Safranine O/triarylalkylborate salt to form a highly efficient three-component photo-initiation system that starts free radical polymerization to finally form holographic gratings with a single-pulsed laser. The mechanism of this photo-initiation most likely relies on an electron transfer from the borate salt into the semi-occupied HOMO of the excited dye molecule Safranine O, which after fragmentation generates an initiating alkyl radical and longer-lived dye radical species. This dye radical is most probably oxidized by the newly introduced trichloromethylarene derivative as an electron acceptor. The two generated radicals from one absorbed photon initiate the photopolymerization and form index gratings in a suitable holographic recording material. This process is purely photonic and does not require further non-photonic post treatments.

Adsorption, Equilibrium Isotherm, and Thermodynamic Studies towards the Removal of Reactive Orange 16 Dye Using Cu(I)-Polyaninile Composite

To overcome some of the limitations of activated carbon like efficiency, cost-effectiveness, and reusability, the present work deals with Cu(I)-based polyaniline (PANI) composite for the removal of reactive orange 16 (RO16) dye. Following the synthesis and characterization of formed Cu(I)-PANI composite, the batch experiments performed for the removal of RO16 dye indicated that the composite has the capacity to reduce the coloring from RO16. The experiments were conducted for the study of effects against changes in pH, time, and dose at room temperature, where we observed for a pH impact on the dye adsorption capacity in the range of 2–12. Among all, the optimal RO16 removal was found to be 94.77% at a pH of 4 and in addition, the adsorption kinetics confirmed to be pseudo-second-order with more suitability towards the Langmuir isotherm, where it is presumed to be the formation of a monolayer of dye molecule at the homogeneous absorbent surface. The calculated maximum capacity, qm, determined from the Langmuir model was 392.156 mg/g. Further application of isotherms to attain thermodynamic parameters, a slight positive value of S° for RO16 adsorption was observed, meaning that there is an increased randomness in the irregular pattern at the specific Cu(I)-PANI interface for an adsorption process. This mechanism plays an essential role in maintaining the effects of water pollution; and, based on the analysis therefore, it is prominent that the Cu(I)-PANI composite can be employed as a promising and economical adsorbent for the treatment of RO16 and other dye molecules from the sewage in wastewater.

Removal of Bromocresol Green from aqueous solution by electro-Fenton and electro-Fenton like processes with different catalysts: laboratory and kinetic model investigation

This study presents the removal of triarylmethane dye Bromocresol Green from aqueous solution by the electro-Fenton process. As catalysts five different cations were used: Fe2+, Ce3+, Ni2+, Mn2+, and Co2+. They play crucial role in the whole process because they react with H2O2 producing hydroxyl radicals that are capable of destruction of dye molecule. Based on this, a comparison of catalytic activity of these cations in the electro-Fenton process is made in the case of Bromocresol Green degradation. Simple and universal kinetic model is also applied to study the catalytic activity of investigated catalysts. Due to its multidimensionality it is fitted to experimental data using genetic algorithm. The procedure of fitting using genetic algorithm is thoroughly described and demonstrated. The activity of utilized catalysts is compared basing on both experimental and model data revealing that in the case of Bromocresol Green removal all alternative catalysts (Ni2+, Co2+, Ce3+, Mn2+) are better than the typical one (Fe2+, 51.83% degradation). The best catalyst is Co2+ with 78.35% degradation efficiency. Moreover, the adopted kinetic model proved its universality and outlined different interactions between catalysts and dye molecules.

Effect of Calcination Temperature on Photocatalytic Degradation Performance of Electrospun β-Ga2O3 Nanofibers

In the present work, Ga2O3 nanofibers were successfully synthesized by electrospinning a solution of polyvinylpyrrolidone (PVP) and gallium nitrate, followed by temperature-controlled calcination treatment of the as-spun PVP and gallium nitrate composite nanofibers. The crystallinity and crystallite size of the Ga2O3 nanofibers can be readily controlled by varying the calcination temperature. From the physicochemical analysis results of the synthesized nanofiber, it was found that the nanofiber calcined at a higher temperature showed a higher crystallinity and a larger crystallite size. The photocatalytic degradation results on rhodamine-B (Rho B) revealed that the photocatalytic activity of the Ga2O3 nanofibers can be improved by optimizing the conflicting characteristics, crystallinity and crystallite size, through the control of the calcination temperature. The photocatalytic activity of a nanofiber calcined at 800 °C for the degradation of Rho B under ultraviolet irradiation exhibits 2.39 and 1.16 times higher than that of nanofibers synthesized at 700 °C and 900 °C, respectively, which is ascribed to relatively efficient charge transfer and dye molecule adsorption by its proper crystallinity and crystallite size.

The synthesis of novel BODIPY compounds for DSSC applications.

The dye-sensitized solar cell (DSSC) represents one of the most promising next-generation photovoltaic technologies. In addition, the DSSC manifold provides an exceptional platform to further appreciate photoinduced electron transfer and the fundamental features required for light-harvesting. The dye molecule is a key component in the DSSC and has achieved minor success utilizing both an organic and inorganic photosensitizers. DSSC’s show great promise owing to their inexpensive synthesis tunable optical and electrochemical properties, and a plethora of design possibilities. The typical anatomy of organic and inorganic DSSC dyes are comprised of a redox-active donor/chromophore (D) that is connected, through a conjugated linker (π), to an acceptor (A) capable of anchoring to titania (TiO2). Fine tuning each of these components can shift the absorption spectrum increasing the overall device efficiency. Boron-dipyrromethene (BODIPY) is an attractive moiety to integrate into DSSC dyes. BODIPY’s rigid organic framework should be able to improve dye stability while the high extinction coefficients of BODIPY based molecules have the potential to increase device performance. Herein, we explore the synthesis and physicochemical properties of BODIPY in an attempt to synthesize efficient DSSC dye molecules and efficient photovoltaic technologies.

The synthesis of novel BODIPY compounds for DSSC applications.

The dye-sensitized solar cell (DSSC) represents one of the most promising next-generation photovoltaic technologies. In addition, the DSSC manifold provides an exceptional platform to further appreciate photoinduced electron transfer and the fundamental features required for light-harvesting. The dye molecule is a key component in the DSSC and has achieved minor success utilizing both an organic and inorganic photosensitizers. DSSC’s show great promise owing to their inexpensive synthesis tunable optical and electrochemical properties, and a plethora of design possibilities. The typical anatomy of organic and inorganic DSSC dyes are comprised of a redox-active donor/chromophore (D) that is connected, through a conjugated linker (π), to an acceptor (A) capable of anchoring to titania (TiO2). Fine tuning each of these components can shift the absorption spectrum increasing the overall device efficiency. Boron-dipyrromethene (BODIPY) is an attractive moiety to integrate into DSSC dyes. BODIPY’s rigid organic framework should be able to improve dye stability while the high extinction coefficients of BODIPY based molecules have the potential to increase device performance. Herein, we explore the synthesis and physicochemical properties of BODIPY in an attempt to synthesize efficient DSSC dye molecules and efficient photovoltaic technologies.