Predicting the degradation potential of Acid blue 113 by different oxidants using quantum chemical analysis

Decolorization of Azo and Anthraquinone Dyes Using Recombinant Horseradish Peroxidase A2A Isoenzyme Produced by Komagataella phaffii

Water pollution is a significant issue due to industrialization and population growth, and one of the main sources of wastewater is synthetic dyes. The textile sector is particularly affected by dyes like azo and anthraquinone dyes, which are difficult to degrade and produce toxic organic waste. Currently, synthetic dyes are processed through physical and chemical methods, which have financial and methodological disadvantages. Horseradish peroxidase (HRP) is a widely studied enzyme for purifying pollutants like dyes and phenols in wastewater. However, their high cost makes them a costly option. Recombinant protein production is suitable for the mass production of stable and resistant enzymes. In this study, the decolorization potential of recombinant HRP A2A (rHRP A2A) isoenzyme secreted by Komagataella phaffii and purified by affinity technique in a single step on Acid blue 113, Alizarin red, and Remazol brilliant blue R was presented for the first time, and the optimal conditions for the highest decolorization rate were determined. Fe2+ and Mn2+ metal ions increased enzyme activity by 158.62% and 79.54%, respectively. Color removal with 0.006 EU/mL rHRP A2A for Acid blue 113, Alizarin red, and Remazol brilliant blue R was observed at 71.27, 62.26, and 31.22%, respectively. ABTS served as a redox mediator, significantly increasing the rate of dye decolorization in a shorter period at the specified concentration.

Adjusting oxidation pathways via fine-tuning atomic ratios in window-opening MOF membranes for efficient self-cleaning

Peroxymonosulfate (PMS) can be used as a green oxidant to mitigate catalytic membranes fouling and restore filtration performance through advanced oxidation processes (AOP). However, the adjustment of oxidation pathways and the understanding of underlying mechanisms for efficient cleaning without sacrificing the filtration performance need to be studied systematically. We optimized the membranes microenvironment via thermal modification from 25 °C to 400 °C below the catalyst ZIF-8 framework's decomposition temperature. The modified membranes have a doubled pure water flux (158.3 LMH bar-1) and remain rejection rates due to intact ZIF-8 framework structure with "window-opening" effect. The methyl dissociation and self-catalyzed graphitization were regulated by changing temperature, resulting in adjustable nonradical pathway proportion (correlated with the C/Zn atomic ratio at 0.96). The enhanced nonradical pathway targeted attacks on electron-rich regions of organic compounds, resulting in efficient cleaning and almost complete flux recovery (99.3 %). The theoretical simulations revealed that methyl groups dissociation and graphitization significantly influence the electron density and adsorption energy at active sites for tunable oxidation pathways and enhanced catalytic performance. Our work offers a rational strategy to improve both filtration and catalytic performance in catalytic membranes. The enhanced understanding of oxidation mechanisms guides the design of designing efficient AOP membrane cleaning systems.

Capability of copper-nickel ferrite nanoparticles loaded onto multi-walled carbon nanotubes to degrade acid blue 113 dye in the sonophotocatalytic treatment process

In this study, copper-nickel ferrite (CuNiFe₂O₄) nanoparticles were successfully loaded onto multi-walled carbon nanotubes (MWCNTs) by using the coprecipitation method and used as new catalysts (MWCNT-CuNiFe₂O₄) in the sonophotocatalytic degradation process of the acid blue 113 (AB113) dye. The success of the MWCNT-CuNiFe₂O₄ synthesis and its properties were determined by analyzing it using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). A high efficiency of dye removal (100%), total organic carbon (93%), and chemical oxygen demand (95%) were achieved with the following conditions: pH of dye solution = 5, MWCNT-CuNiFe₂O₄ dosage = 0.6 g/L, AB113 dye concentration = 50 mg/L, UV light intensity = 36 W, ultrasonic wave frequency = 35 kHz, and treatment time = 30 min. The kinetic results revealed that the efficiency of the sonophotocatalytic process using MWCNT-CuNiFe₂O₄ was higher than that of the sonolysis, photolysis, photocatalysis, and sonocatalysis processes. Scavenging studies demonstrated that the holes (h⁺) and hydroxyl radical (•OH) were the main reactive species for the AB113 dye degradation. The stability and recyclability of MWCNT-CuNiFe₂O₄ were confirmed with eight consecutive cycles for a maximum efficiency of more than 92%. The high rate of BOD₅/COD indicated that the sonophotocatalytic process had the potential to degrade the dye into degradable compounds. The toxicity study with an Escherichia coli growth inhibition rate emphasized that MWCNT-CuNiFe₂O₄ in the sonophotocatalytic degradation process of the AB113 dye had a significant effect on reducing toxicity, when compared to processes of photolysis and photocatalysis. During the sonophotocatalytic process using MWCNT-CuNiFe₂O₄, the AB113 dye was mineralized into CO₂, H₂O, NH₄⁺, NO₃^-, and SO₄^2-. The results of the present study proved that the MWCNT-CuNiFe₂O₄-based sonophotocatalytic process was a promising dye degradation technology to protect the aquatic environment.

Photovoltaic properties of novel reactive azobenzoquinolines: experimental and theoretical investigations

In this work, synthesis, characterization, DFT, TD-DFT study of some novel reactive azobenzoquinoline dye structures to elucidate their photovoltaic properties. The azobenzoquinoline compounds were experimentally synthesized through a series of reaction routes starting from acenaphthene to obtained aminododecylnaphthalimide and finally coupled with diazonium salts to get the desired azobenzoquinoline. Azo dye synthesized differ in the number of alkyl chains designated as (AR1, AR2, AR3, and AR4) which were experimentally analyzed using FT-IR and NMR spectroscopic methods. The synthesized structures were modelled for computational investigation using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) combined with B3LYP and 6-31+G(d) basis set level of theory. The results showed that the HOMO-LUMO energy gap was steady at approximately 2.8 eV as the alkyl chain increases, which has been proven to be within the material energy gap limit for application in photovoltaic. The highest intramolecular natural bond orbital (NBO) for the studied compounds is 27.60, 55.06, 55.06, and 55.04 kcal/mol for AR1, AR2, AR3, and AR4 respectively and the donor and acceptor interacting orbitals for the highest stabilization energy (E (2)) are LP(1)N 18 and π*C 16−O 19 respectively. The photovoltaic properties in terms of light-harvesting efficiency (LHE), Short circuit current density (J SC), Gibbs free energy of injection (ΔG inj), open-circuit voltage (V OC) and Gibbs free energy of regeneration (ΔG reg) were evaluated to be within the required limit for DSSC design. Overall, the obtained theoretical photovoltaic results were compared with other experimental and computational findings, thus, are in excellent agreement for organic solar cell design.

σ-Hole and LP-Hole Interactions of Pnicogen···Pnicogen Homodimers under the External Electric Field Effect: A Quantum Mechanical Study

σ-Hole and lone-pair (lp)-hole interactions within σ-hole···σ-hole, σ-hole···lp-hole, and lp-hole···lp-hole configurations were comparatively investigated on the pnicogen···pnicogen homodimers (PCl3)2, for the first time, under field-free conditions and the influence of the external electric field (EEF). The electrostatic potential calculations emphasized the impressive versatility of the examined PCl3 monomers to participate in σ-hole and lp-hole pnicogen interactions. Crucially, the sizes of σ-hole and lp-hole were enlarged under the influence of the positively directed EEF and decreased in the case of reverse direction. Interestingly, the energetic quantities unveiled more favorability of the σ-hole···lp-hole configuration of the pnicogen···pnicogen homodimers, with significant negative interaction energies, than σ-hole···σ-hole and lp-hole···lp-hole configurations. Quantum theory of atoms in molecules and noncovalent interaction index analyses were adopted to elucidate the nature and origin of the considered interactions, ensuring their closed shell nature and the occurrence of attractive forces within the studied homodimers. Symmetry-adapted perturbation theory-based energy decomposition analysis alluded to the dispersion force as the main physical component beyond the occurrence of the examined interactions. The obtained findings would be considered as a fundamental underpinning for forthcoming studies pertinent to chemistry, materials science, and crystal engineering.

Transcriptomic Analysis of Degradative Pathways for Azo Dye Acid Blue 113 in Sphingomonas melonis B-2 from the Dye Wastewater Treatment Process

Background: Acid Blue 113 (AB113) is a typical azo dye, and the resulting wastewater is toxic and difficult to remove. Methods: The experimental culture was set up for the biodegradation of the azo dye AB113, and the cell growth and dye decolorization were monitored. Transcriptome sequencing was performed in the presence and absence of AB113 treatment. The key pathways and enzymes involved in AB113 degradation were found through pathway analysis and enrichment software (GO, EggNog and KEGG). Results: S. melonis B-2 achieved more than 80% decolorization within 24 h (50 and 100 mg/L dye). There was a positive relationship between cell growth and the azo dye degradation rate. The expression level of enzymes involved in benzoate and naphthalene degradation pathways (NADH quinone oxidoreductase, N-acetyltransferase and aromatic ring-hydroxylating dioxygenase) increased significantly after the treatment of AB113. Conclusions: Benzoate and naphthalene degradation pathways were the key pathways for AB113 degradation. NADH quinone oxidoreductase, N-acetyltransferase, aromatic ring-hydroxylating dioxygenase and CYP450 were the key enzymes for AB113 degradation. This study provides evidence for the process of AB113 biodegradation at the molecular and biochemical level that will be useful in monitoring the dye wastewater treatment process at the full-scale treatment.

UV-Catalyzed Persulfate Oxidation of an Anthraquinone Based Dye

Wastewater from the textile industry has a substantial impact on water quality. Synthetic dyes used in the textile production process are often discharged into water bodies as residues. Highly colored wastewater causes various of problems for the aquatic environment such as: reducing light penetration, inhibiting photosynthesis and being toxic to certain organisms. Since most dyes are resistant to biodegradation and are not completely removed by conventional methods (adsorption, coagulation-flocculation, activated sludge, membrane filtration) they persist in the environment. Advanced oxidation processes (AOPs) based on hydrogen peroxide (H2O2) have been proven to decolorize only some of the dyes from wastewater by photocatalysis. In this article, we compared two very different photocatalytic systems (UV/peroxydisulfate and UV/H2O2). Photocatalyzed activation of peroxydisulfate (PDS) generated sulfate radicals (SO4•−), which reacted with the selected anthraquinone dye of concern, Acid Blue 129 (AB129). Various conditions, such as pH and concentration of PDS were applied, in order to obtain an effective decolorization effect, which was significantly better than in the case of hydroxyl radicals. The kinetics of the reaction followed a pseudo-first order model. The main reaction pathway was also proposed based on quantum chemical analysis. Moreover, the toxicity of the solution after treatment was evaluated using Daphnia magna and Lemna minor, and was found to be significantly lower compared to the toxicity of the initial dye.

Opposite pH-dependent roles of hydroxyl radicals in ozonation and UV photolysis of genistein

Phytoestrogens were frequently detected in municipal or industrial wastewater, and raised great attentions due to potential risks to humans or organisms. Until now, transformation mechanisms of phytoestrogens in advanced wastewater treatments were largely unknown. Here, pH influence mechanisms on transformations of phytoestrogens during two typical advanced wastewater treatments (ozonation and photolysis) were investigated, employing genistein (Gs) as a case. Removal efficiencies of Gs decreased significantly with increases of pH during ozonation, while photolytic rates increased by 44 or 200 times from pH 4.9 to 11.6 under irradiations without or with UVC. pH increases caused both dissociation of Gs and formation of hydroxyl radicals (OH) in ozonation or photolysis, however, led to opposite changes to degradation rates. This was because that OH played negatively as a competitor for O₃ in ozonation, but acted as an accelerating species inducing self-sensitized photooxidation of Gs under UV light. Ozonation and photolytic products of Gs were similar at pH 4.9 or 8.6, but were totally different at pH 11.6. Most of the transformation products maintained isoflavone structures, and might possess phytoestrogenic effects. This study provided a deep insight into the pH influencing mechanism on typical advanced wastewater treatment processes of phytoestrogens. MAIN FINDING OF THE WORK: Opposite pH-dependent degradation mechanisms caused by hydroxyl radicals (OH) were elucidated for ozonation and UV photolysis of phytoestrogens, taking genistein as a case.