Orange G Research Articles

Good adsorption performance for both cationic and anionic dyes by a novel crosslinked tetrafluoroterephthalonitrile-tannic acid-chitosan polymer synthesized via one-pot reaction

In this work, tetrafluorophenonitrile was utilized to crosslink tannic acid and chitosan together to form a new crosslinked polymer (CSTTA), and then the Fe3O4 nanoparticles were prepared and immortalized on the CSTTA at the same time to obtain the Fe3O4/CSTTA composite. The structures of CSTTA polymer and Fe3O4/CSTTA composite were characterized by SEM, FTIR, TGA, 13CNMR, XPS, WAXD, N2 adsorption-desorption isotherm, VSM, and zeta potential measurement. The CSTTA could simultaneously adsorb the cationic methylene blue (MB) and anionic orange G (OG), and its adsorption behaviors for MB and OG conformed to the pseudo-second-order kinetic model and the Langmuir isotherm model, which were spontaneous according to thermodynamic calculation. The CSTTA possessed not only high adsorption capacities for both MB and OG up to 1092.69 mg/g and 519.89 mg/g at 303 K under the optimal pH conditions of pH=10 and pH=1, respectively, but also the good reused ability. In addition, the Fe3O4/CSTTA composite could also absorb both MB and OG with good magnetically recollected ability to avoid secondary pollution.

Enhanced band gap energy of one-pot mechano-synthesized Ag3PO4 for Orange G photodegradation under visible light irradiation: An in-depth experimental and DFT studies

The present study highlights the efficiency of Ag3PO4 photocatalyst with a band gap of 2.25 eV, synthesized by a green and one-pot simple mechanochemical method, towards photodegradation of orange G under visible irradiation. The phase structure, morphology, and optical properties of mechano-synthesized Ag3PO4 were investigated using X-ray diffraction, Scanning Electron Microscopy, Thermogravimetric Analysis, Fourier Transform Infrared, the Brunauer-Emmet-Teller surface area, and UV–vis diffuse reflectance spectroscopy. DFT calculations were also conducted for band gap energy prediction. The photocatalytic activity of the sample was evaluated using a central composite design for surface response methodology (CCD-RSM) to determine the optimal conditions for Orange G (OG) removal. The photocatalytic activity of Ag3PO4 was approximately 93 % within 20 min of reaction under irradiation for 24.6 mg/L and 11 mg/L of Ag3PO4 and Orange G, respectively. Trapping experiments confirmed that peroxides and hydroxyl radicals are the dominant active species in the photodegradation process.

Selective oxidation of organic pollutants by unactivated and carbonate-activated peroxymonosulfate (PMS): Mechanism, kinetics, and transformation pathway

Although the activation mechanisms of peroxymonosulfate (PMS) by various homogeneous and heterogeneous catalysts have been reported, the chemistry of PMS in catalyst-free systems and its interaction with background oxygenated anions remains poorly understood. In this study, the unactivated PMS and carbonate-activated PMS (CO32–/PMS) systems for removal of various organic pollutant (including oxytetracycline (OTC), metronidazole (MNZ), methylene blue (MB), and acid orange G (OG)) were investigated. The results showed that 74.5 %, 90.21 %, 1.22 %, and 2.25 % of OTC, MB, OG, and MNZ were removed, respectively within 180 min in the unactivated PMS system due to the formation of ·OH and 1O2. 95.88 %, 100 %, 100 %, and 6.09 % of OTC, MB, OG, and MNZ were removed, respectively in the CO32–/PMS system, which is primary due to the generation of 1O2. The removal efficiencies of these four pollutants were significantly improved under alkaline conditions. In addition, the TOC removal rates were 21.88 % for MB and 26.53 % for OTC within 180 min in the CO32–/PMS system. The presence of Cl− and SO42− can greatly enhance the OTC removal efficiency both in the unactivated and CO32–/PMS systems. Through the high performance liquid chromatography-mass spectrometry (HPLC-MS) analysis, OTC degradation products in the unactivated PMS and CO32–/PMS systems were identified, revealing six different reaction mechanisms, including hydroxylation (+16 Da), decarbonylation (−28 Da), demethylation (−14 Da), secondary alcohol oxidation (−2 Da), deamination (−15 Da), and dehydration (−18 Da). This study provides insight into the reaction mechanism of catalyst-free PMS systems and may promote the application of unactivated PMS and CO32–/PMS systems for the remediation of organic contaminated water.

An efficient novel NiCu@INA/rGO MOF hollow microsphere Z-scheme heterojunction catalyst for the photocatalytic degradation of tetracycline and simultaneous degradation of cationic and anionic Dyes

Bimetallic metal-organic framework materials have captivated considerable attention in photocatalysis because of their colossal properties like semiconducting, large surface area, and potent visible light harnessing ability. Self-aggregation and rapid recombination rates have greatly hindered their applications in photocatalysis. A novel reduced graphene oxide-incorporated bimetallic nickel copper metal-organic framework (NiCu@INA/rGO MOF) is fabricated using isonicotinic acid as an organic linker. A synergistic effect between the two metals increased the photocatalytic performance. Introducing reduced graphene oxide to nickel-copper MOF increased charge carrier retention transfer and enhanced the catalyst’s water dispersibility. The efficiency of the photocatalyst for the removal of tetracycline (TCn) and a mixture of Rhodamine B (RhB) and Orange G (OrG) dyes was investigated under visible light. A degradation efficiency of up to 89 % for TCn and close to ∼97.8 % and 93.5 % degradation in the case of RhB and OrG dyes was observed. The studies on the photocatalytic degradation mechanism were explored by conducting radical scavenger experiments, Electron spin resonance (ESR) studies, and Mott-Schottky analysis. TCn and RhB degradation pathways were explored by mass spectral analysis of the intermediates during the photocatalytic degradation of TCn and RhB. This work provides new paradigms for the functional modification of MOF for designing efficient photocatalysis.

One-pot synthesis of iron-copper-embedded porous carbon from alginate for activating persulfate towards Orange G decolorization

In recent years, multifunctional materials have garnered significant attention due to their potential to possess multiple properties and functionalities simultaneously.Herein, a novel one-pot pyrolysis was employed to facilely prepare iron (Fe0) and copper (Cu0) nanoparticles (23 ± 4 nm) embedded in porous carbon (FeCu/PC). The as-synthesized nanocomposite had a SBET of 136 m2/g, a Vtotal of 0.133 cm3/g, and a hierarchical porousstructure. In addition, its MS of 10.7 emu/g aids in simple and effective separation using external magnetic fields. For application, 1.00 g/L FeCu/PC activated 3.00 mM persulfate (PS) to decolorize 93.7 % of 25 ppm Orange G (OG) after 120 min at initial pH 7.0 and 30 °C. The combination of Fe and Cu could promote the synergistic effect, which resulted in more effective PS activation over a wide pH range. With the chemical activation, the activation energy (EA) of OG decolorization was only 36 kJ/mol. Overall, the multifunctional FeCu/PC material proved not only potential magnetic separability but also effectiveness in activating PS during OG treatment.

Synthesis and Dye Adsorption Dynamics of Chitosan-Polyvinylpolypyrrolidone (PVPP) Composite.

One major environmental issue responsible for water pollution is the presence of dyes in the aquatic environment as a result of human activity, particularly the textile industry. Chitosan-Polyvinylpolypyrrolidone (PVPP) polymer composite beads were synthesized and explored for the adsorption of dyes (Bismarck brown (BB), orange G (OG), brilliant blue G (BBG), and indigo carmine (IC)) from dye solution. The CS-PVPP beads demonstrated high removal efficiency of BB (87%), OG (58%), BBG (42%), and IC (49%). The beads demonstrated a reasonable surface area of 2.203 m2/g and were negatively charged in the applicable operating pH ranges. TGA analysis showed that the polymer composite can withstand decomposition up to 400 °C, proving high stability in harsh conditions. FTIR analysis highlighted the presence of N-H amine, O-H alcohol, and S=O sulfo groups responsible for electrostatic interaction and hydrogen bonding with the dye molecules. A shift in the FTIR bands was observed on N-H and C-N stretching for the beads after dye adsorption, implying that adsorption was facilitated by hydrogen bonding and Van der Waals forces of attraction between the hydroxyl, amine, and carbonyl groups on the surface of the beads and the dye molecules. An increase in pH increased the adsorption capacity of the beads for BB while decreasing OG, BBG, and IC due to their cationic and anionic nature, respectively. While an increase in temperature did not affect the adsorption capacity of OG and BBG, it significantly improved the removal of BB and IC from the dye solution and the adsorption was thermodynamically favoured, as demonstrated by the negative Gibbs free energy at all temperatures. Adsorption of dye mixtures followed the characteristic adsorption nature of the individual dyes. The beads show great potential for applications in the treatment of dye wastewater.

Valorizing Moroccan crab shells to purify water from Orange G dye: Exploring equilibrium, kinetics, and thermodynamics

A successful approach has been taken to develop a biomaterial derived from fish waste, using Moroccan fish processing by-products from crab shells. Moroccan crab (Portunus pelagicus) shell-derived biomaterial has been developed for wastewater treatment, using marine crustacean waste and addressing the challenges of solid fish waste management. The crab shell powder (CSP) was calcined at 800 °C for three hours and characterized using SEM, EDS, FTIR, and XRD, revealing a predominantly crystalline structure. The CSP's effectiveness as a biosorbent for the removal of the anionic dye Orange G (OG) was assessed under various conditions, including pH, biosorbent mass, temperature, and contact time. Optimal conditions achieved a 98.84 % dye removal rate within 60 min at an adsorbent dose of 0.09 g. The adsorption process adhered to the pseudo-second-order kinetic model and the Freundlich isotherm, indicating a spontaneous, endothermic surface reaction involving multilayer physisorption. The biosorption mechanism is thought to include electrostatic attractions, n-π stacking interactions, hydrogen bonding, and Yoshida hydrogen bonds. The study suggests that CSP is an efficient, eco-friendly adsorbent for industrial wastewater treatment, offering a promising solution for the valorization of fish waste by-products.

PH independent adsorption: Reusable zinc-ferrite nanospheres for the selective recovery of dyes from binary mixtures

Efficient separation of colorant pollutants is a formidable challenge, prompting research into innovative materials. We developed zinc-ferrite nanoparticles via the Microwave-Assisted Solvothermal Technique (MAST), exploiting judicious solvent compositions to enhance Lewis's acidity. Upscaling to gram batches yielded nanoparticles with a higher specific surface area (149 m2g−1). These nanoparticles demonstrated selective separation of dyes from binary mixtures, including Orange-G (OG), Fluorescein-Sodium (FSS), and Methyl-Orange (MO), with their high sorption rate fitting to the pseudo-second-order kinetic model. Langmuir isotherm for OG and MO were observed with respective adsorption capacity (qm) of 94.12 mg/g, 104.28 mg/g, whereas FSS more likely matched Sips isotherm with qm = 124.31 mg/g at natural pH in room temperature (27 °C). Desorption, reliant on solution pH and OH− ions, enabled efficient regeneration and multiple reuses without significant efficiency loss over five reuse cycles. Remarkably, selective separation was independent of surface charge and remained effective across a wide pH range and in the presence of common anions, namely I−, NO3−, C2H3O2− routinely encountered in dye effluents. This ecologically safe, scalable adsorbent offers a promising solution for expensive dye recovery.

Fabrication of mixed matrix membranes based on PVDF matrix and ZrT-1-NH2 filler for efficient adsorptive removal of Orange G

Adsorption membranes have become a hot spot for wastewater treatment in recent years. Due to the lack of active sites in traditional inert materials such as polyvinylidene fluoride (PVDF) membranes, it is difficult to bind pollutants in water with high affinity. Therefore, in this study, ZrT-1-NH2/PVDF mixed matrix membranes (MMMs) were prepared by combining an amino-functionalized Zr-based metal–organic cage (ZrT-1-NH2) with a polymer substrate via non-solvent-induced phase separation method for the efficient removal of Orange G (OG) from water. This method has many advantages such as simplicity in operation, high applicability, controllable MOFs loading. The structural characteristics and adsorption properties and of MMMs were also investigated through a series of characterizations and experiments. The result shows that in a 100 mL OG solution with an initial concentration of 50 mg/L and pH=3, M60 exhibited significant adsorption capacity, the removal efficiency reached 97.23 %, with an adsorption capacity of 64.18 mg/g, which is much higher than the pristine PVDF membrane. It is mainly attributed to electrostatic interactions and hydrogen bonding interactions between ZrT-1-NH2 and OG molecules. This is consistent with the DFT calculations. The introduction of ZrT-1-NH2 filler improves the performance of PVDF membranes and expands their potential applications.

Removal of pollutants by olive stones-derived activated carbon@Fe3O4 nanocomposites: Effect of calcination temperature on adsorption properties

This work focuses on preparing nanocomposites based on activated carbon as a matrix obtained from bio and natural source olive stones calcined at different temperatures (300,450 and 600 °C) and decorated with an ultrasonic dispersion of magnetite Fe3O4. The obtained materials (CA-300@Fe3O4, CA-450@Fe3O4, CA-600@Fe3O4) were used as adsorbents for the elimination of organic and inorganic pollutants, such as dyes (Methylene blue (MB) and Orange G (OG)) and heavy metals (Copper (Cu(II)), Nickel (Ni(II))), by varying various influencing factors (concentration, pH, temperature, contact time effect), and the adsorption data were analysed using two kinetic models (pseudo-first order and pseudo-second order) and two isotherm models (Freundlich and Langmuir). Different characterisation methods, such as FTIR, XRD, nitrogen adsorption–desorption, TGA, SEM, TEM, EDS, and zeta potential, were used. The experimental data show that all synthesised materials have proven their efficiency in the adsorption of both organic and inorganic pollutants even after five reuse cycles without any regeneration treatment. The study showed that all nanocomposites follow the Langmuir isotherm and the pseudo-second-order as kinetic model for both organic and inorganic pollutants. The most efficient nanocomposite was CA-450@Fe3O4 with a maximum adsorption capacity Qmax (564.97, 404.85, 787.4 and 625 mg/g) for the elimination of MB, OG, Cu, and Ni, respectively.

PMMA microspheres-embedded Ti3C2Tx MXene heterophotocatalysts synergistically working for multiple dye degradation

We developed a novel MXene/polymer hybrid material for enhanced photodegradation of multiple organic dyes. Specifically, uniform-sized PMMA microspheres and multilayer Ti3C2Tx MXene were integrated through a facile solution process to form PMMA/Ti3C2Tx composites. The hybridization of the two components significantly increased the specific surface area and pore volume. An optimized composite showed high photocatalytic activity, demonstrating 93 and 98 % degradation efficiencies for orange G (OG) and rhodamine B (RhB) in 60 min of light illumination. Furthermore, the composite revealed good recyclability without a significant performance drop even after four cycles. Moreover, the composite retained its high photocatalytic activity at various conditions, including elevated temperatures, a wide range of pH levels, and in tap water. These results manifest that the PMMA/Ti3C2Tx hetero-photocatalyst is well suited for use in wastewater treatment and environmental cleanup.

Eco-friendly engineering of micro composite-based hydroxyapatite bio crystal and polyaniline for high removal of OG dye from wastewater: Adsorption mechanism and RSM@BBD optimization

The presence of harmful substances such as dyes in water systems poses a direct threat to the quality of people's lives and other organisms living in the ecosystem. Orange G (OG) is considered a hazardous dye. The existing paper attempts to evaluate a low-cost adsorbent for the effective removal of OG dye. The developed adsorbent Polyaniline@Hydroxyapatite extracted from Cilus Gilberti fish Scale (PANI@FHAP) was elaborated through the application of the in situ chemical polymerization method to incorporate PANI on the surface of naturally extracted hydroxyapatite FHAP. The good synthesis of PANI@FHAP was evaluated through multiple techniques including X-ray diffraction (XRD), Scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM/EDS), Fourier Transforms Infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) coupled with thermal differential analysis (DTA) analysis. The results reveal a highly ordered disposition of PANI chains on FHAP, resulting in a well-coated FHAP in the PANI matrix. Furthermore, the presence of functional groups on the surface of PANI such as amine (-NH2) and imine (=NH) groups would facilitate the removal of OG dye from contaminated water. The adsorption of OG onto PANI@FHAP was conducted in batch mode and optimized through response surface methodology coupled with box-Behnken design (RSM/BBD) to investigate the effect of time, adsorbent dose, and initial concentration. The outcomes proved that OG adsorption follows a quadratic model (R2 = 0.989). The kinetic study revealed that the adsorption of OG fits the pseudo-second-order model. On the other hand, the isotherm study declared that the Freundlich model is best suited to the description of OG adsorption. For thermodynamic study, the adsorption of OG is spontaneous in nature and exothermic. Furthermore, the regeneration-reusability study indicates that PANI@FHAP could be regenerated and reused up to five successive cycles. Based on the FTIR spectrum of PANI@FHAP after OG adsorption, the mechanism governing OG adsorption is predominantly driven by π-π interaction, electrostatic interaction, and hydrogen bonding interactions. The obtained results suppose that PANI@FHAP adsorbent can be a competitive material in large-scale applications.

Investigating AgCl-SnO2 nanocomposite for photocatalytic degradation of azo dye, associated reaction pathways, and its antibacterial activity

Herein, AgCl-SnO2 nanocomposite (NC) fabricated through a facile hydrothermal method exhibit substantial potential as an efficient and economical photocatalyst and bactericidal agent. The formation of spherical AgCl-SnO2 NC was confirmed through PXRD and SEM, with an average crystalline size of 12 nm. DR spectra and Kubelka-Munk function were used to determine the band gaps of AgCl (3.10 eV) and SnO2 (3.48 eV). The synthesized NC achieve successful photocatalytic degradation (98 %) of orange-G (OG) dye within 60 min. The NC’s potential was also elucidated by investigating the role of sacrificial reagents. Formation of •OH free radicals is confirmed from photoluminescence studies using terephthalic acid. The effective degradation of OG dye has been substantiated, resulting in the generation of numerous intermediate products with reduced toxicity, such as substituted phenols and aromatic dicarboxylic compounds. Furthermore, the NC demonstrated excellent efficiency even after six consecutive cycles, indicating its stability, regenerative property, and recyclability. The NC also exhibits significant antimicrobial activity against Escherichia coli.

Electrocatalytic and photoelectrocatalytic investigation of Orange G degradation utilizing a novel BHP@Bi2O3 photoanode employing the CCD-RSM experimental design

In this study, we synthesized a bilayer film consisting of BaHPO4 (BHP) and Bi2O3 through the electrodeposition technique. The produced anode was subjected to characterization using cyclic voltammetry to clarify the deposition reactions. Subsequent to this, structural and morphological analyses were conducted utilizing X-ray diffraction alongside scanning electron microscopy, coupled with energy-dispersive X-ray spectroscopy. Additionally, UV–vis diffuse reflectance spectroscopy was employed to determine the bandgap energies of both semiconductors. Following an electrochemical characterization using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and Mott-Schottky (MS) measurements, the photoanode was employed for the electro-degradation of the anionic dye Orange G (OG), varying key degradation parameters such as current density, pollutant concentration, supporting electrolyte concentration, and pH using the CCD-RSM experimental design method. A degradation efficiency of 98% was achieved within a 20-minute timeframe. Photoelectrocatalytic tests under UV irradiation reduced the degradation time from 20 to 6 min, with a degradation rate of 99%. Additionally, under the same conditions, the BHP@Bi2O3 photoanode exhibited good stability, enduring up to 11 cycles of use.

Synthesis of Composite Sorbents with Chitosan and Varied Silica Phases for the Adsorption of Anionic Dyes.

In this work, various types of silica materials were used for the synthesis of chitosan-silica composites. The composites were obtained using the chitosan (Ch) immobilization process from an aqueous solution on various silica phases, i.e., amorphous diatomite (ChAD), crystalline diatomite (ChCD), mesoporous silica MCM-41 (ChMCM), and mesoporous silica SBA-15 (ChSBA). Textural, structural, morphological, and surface properties of the materials were determined by using various measurement techniques, i.e., low-temperature adsorption/desorption isotherms of nitrogen, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), potentiometric titration, high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The adsorption properties towards various anionic dyes, i.e., acid red 88 (AR88), acid orange 8 (AO8), and orange G (OG), were evaluated based on kinetic and equilibrium measurements. The ChSBA, ChAD, and ChMCM composites were characterized by relatively high adsorption capacities (am) for AR88, with values equal to 0.78, 0.71, and 0.69 mmol/g, respectively. These composites were also distinguished by the rapid AR88 adsorption rate, with the values of half-time parameter t0.5 equal to 0.35, 2.84, and 1.53 min, respectively. The adsorption equilibrium and kinetic data were analyzed by applying the generalized Langmuir isotherm and the multi-exponential equation (m-exp), respectively. An interaction mechanism between the dyes and the obtained materials was proposed.

Green biocatalyst for decolorization of azo dyes from industrial wastewater: Coriolopsis trogii 2SMKN laccase immobilized on recycled brewer's spent grain.

This study presents an innovative approach for the reuse and recycling of waste material, brewer's spent grain (BSG) for creating a novel green biocatalyst. The same BSG was utilized in several consecutive steps: initially, it served as a substrate for the cultivation and production of laccase by a novel isolated fungal strain, Coriolopsis trogii 2SMKN, then, it was reused as a carrier for laccase immobilization, aiding in the process of azo dye decolorization and finally, reused as recycled BSG for the second successful laccase immobilization for six guaiacol oxidation, contributing to a zero-waste strategy. The novel fungal strain produced laccase with a maximum activity of 171.4 U/g after 6 days of solid-state fermentation using BSG as a substrate. The obtained laccase exhibited excellent performance in the decolorization of azo dyes, both as a free and immobilized, at high temperatures, without addition of harmful mediators, achieving maximum decolorization efficiencies of 99.0%, 71.2%, and 61.0% for Orange G (OG), Congo Red, and Eriochrome Black T (EBT), respectively. The immobilized laccase on BSG was successfully reused across five cycles of azo dye decolorization process. Notably, new green biocatalyst outperformed commercial laccase from Aspergillus spp. in the decolorization of OG and EBT. GC-MS and LC-MS revealed azo-dye degradation products and decomposition pathway. This analysis was complemented by antimicrobial and phytotoxicity tests, which confirmed the non-toxic nature of the degradation products, indicating the potential for safe environmental disposal.

Sustainable efficient utilization of magnetic porous biochar for adsorption of orange G and tetracycline: Inherent roles of adsorption and mechanisms

Iron-doped biochar has been widely used as an adsorbent to remove contaminants due to the high adsorption performance, but it still suffers from complicated preparation methods, unstable iron loading, unsatisfactory specific surface area, and uneven distribution of active sites. Here, a novel magnetic porous biochar (FeCS800) with nanostructure on surface was synthesized by one-pot pyrolysis method of corn straw with K2FeO4, and used in orange G (OG) and tetracycline (TC) adsorption. FeCS800 exhibited outstanding adsorption capacities for OG and TC after K2FeO4 activation and the adsorption data were fitted satisfactorily to Langmuir isotherm and Pseudo-second-order kinetic model. The maximum adsorption capacities of FeCS800 for OG and TC were around 303.03 mg/g and 322.58 mg/g, respectively, at 25 °C and pH 7.0, which were 16.27 and 24.61 times higher than that before modification. Thermodynamic studies showed that the adsorption of OG/TC by FeCS800 were thermodynamically favorable and highly spontaneous. And the adsorption capacity of OG and TC by FeCS800 remained 77% and 81% after 5 cycles, respectively, indicating that FeCS800 had good stability. The outstanding adsorption properties and remarkable reusability of FeCS800 show its great potential to be an economic and environmental adsorbent in contaminants removal.

In English

Currently, textile and food industries produce a significant volume of sewages containing azo dyes and other organic pollutants. These effluents are serious environmental threats, so new methods for their treatment and the degradation of azo dyes are attracting much attention. Composite materials based on TiO2 modified by noble metals and nanoceria show high activity in the photodegradation of organic contaminates and are proposed for hydrogen synthesis as well. To optimize the treatment of contaminants, different processes can combine including the strategies of adsorption, photoluminescence, photocatalysis, etc. The synthesized TiO2-based nanomaterials (sols, powders) will be exploited for bioremediation due to their small size and surface plasmon resonance from noble metals. Binary nanocomposites based on TiO2 were obtained by the chemical co-precipitation method from solutions of titanium tetraisopropoxide (TTIP) and inorganic salts of cerium, silver, and palladium. It has been stated that TiO2 is represented by anatase with primary particle size (CSR) from 8.5 to 16.8 nm, depending on the nature and concentration of the dopant. It is shown that Ag is reduced on the surface of anatase particles and blocks their growth, while Pd and Ce penetrate the titanium dioxide matrix in the form of small clusters with the deformation of the anatase crystal lattice. Nanocomposite particles formed loose and fragile aggregates, which spontaneously dispersed in solutions of dyes with the formation of colloid-stable sols, required the use of a centrifugal field for their sedimentation. Nanoparticles of TiO2&Pd were electronegative and others were electropositive according to the values 4.1÷9.6 of ZPC (zero point of charge). It was shown that the particles of all composites sorbed Methylene Blue (MB) without photocatalytic activity under the visible light to any dye. Moreover, anionic dyes such as Orange-G (Or-G) and Methyl Orange (MO) were excellently discolorated in the presence of TiO2&Pd system; cationic dyes of MB and Rhodamine B (RhB) discolorated too with the TiO2, TiO2&CeO2, and TiO2&Ag systems under UV light action. As such, photocatalysis tests showed that Orange-G’s and MO’s discoloration was higher for TiO2&Pd (2 wt. %) and TiO2 systems with the correlation coefficient R2 0.999.

Ag2CO3 phases in nanocomposites with palygorskite and their effects on photocatalytic and antibacterial activities

Various nanocomposites based on Ag2CO3 loaded onto natural fibrous palygorskite (Pal) were elaborated by a simple precipitation route. Their composition ranged from metastable hexagonal β-Ag2CO3 nanoparticles immobilized on the surface of Pal microfibers to a mixture with stable monoclinic m-Ag2CO3 particles trapped in the tangle of Pal fibers. The choice of elaboration parameters enables to control the relative content of each phases phase ratio “metastable β-hexagonal / (stable monoclinic + metastable β-hexagonal)” of Ag2CO3 and thus to tune the resulting multifunctional properties (mainly photocatalytic and biocidal activities) of the nanocomposites.Optical studies interestingly revealed, for all Ag2CO3-Pal nanocomposites, a noticeable absorption in the visible light range. Accordingly, all the Ag2CO3 based Pal nanocomposites were found to be photoactive under visible light for the removal of Orange G (OG) dye but biphasic (β + m)-Ag2CO3-Pal nanocomposite was more photoactive than those in which Ag2CO3 was monophasic (either β-hexagonal or monoclinic phases). This could be due to synergy effects between the two Ag2CO3 phases. Besides, all the developed Pal based nanocomposites remained active upon several reusability cycling tests. Likewise, both the nanocomposites materials and the starting Pal clay mineral were found antibacterial against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria.

A novel sugarcane residue-derived bimetallic Fe/Mn-biochar composite for activation of peroxymonosulfate in advanced oxidation process removal of azo dye: Degradation behavior and mechanism

Metal-biochar composites with varying Fe/Mn ratios were synthesized for activating peroxymonosulfate (PMS) oxidative degradation of azo dye Orange G (OG) were investigated. The 1Fe2Mn-BC composite based on 1:2 molar ratio impregnation of Fe/Mn salt concentrations of efficient sugarcane harvest residue showed the best catalytic performance under aqueous pH 3–10 and had the least impacts from coexistence of inorganic anions and humic acids. The OG degradation by 1Fe2Mn-BC/PMS system optimized at catalyst:oxidant:pollutant ratio of 1:1.25:0.5 on g/L basis was found to follow pseudo-first-order kinetic and achieved 100 % degradation efficiency within 30 min. Apparent activation energy for OG degradation by 1Fe2Mn-BC/PMS was 16.91 kJ mol−1, and increasing reaction temperature from 293 to 313 K enhanced degradation rate constant by 49 %. Electron paramagnetic resonance (EPR) and radical quenching experiments revealed dominant non-radical 1O2 and radical O2− pathways in the OG oxidation removal by the 1Fe2Mn-BC/PMS system, although SO4− and OH radicals also participated. XPS spectra of 1Fe2Mn-BC before and after OG degradation indicated dominant surface composition of Fe(III) and Mn(II) valence states over other FeMn-biochar composites. The novel optimized one-step pyrolysis Fe/Mn bimetal biochar composite provides an efficient PMS activation for advanced oxidation process (AOP) treating of azo dyes in wastewater decontamination.