Effective degradation of azo dye from textile wastewater by electro-peroxone process

TiO2-Decorated by Nano-γ-Fe2O3 as a Catalyst for Efficient Photocatalytic Degradation of Orange G Dye under Eco-friendly White LED Irradiation

Azo dyes make up a major class of dyes that have been widely studied for their diverse applications. In this study, we successfully applied nano-γ-Fe2O3/TiO2 as a nanocatalyst to improve the photodegradation efficiency of azo dyes (Orange G (OG) dye as a model) from aqueous solution under white light-emitting diode (LED) irradiation. We also investigated the degradation mechanisms and pathways of OG dye as well as the effects of the initial pH value, amount of H2O2, catalyst dosage, and dye concentration on the degradation processes. The characterizations of nano-γ-Fe2O3 and γ-Fe2O3 Nps/TiO2 were carried out using various techniques, including X-ray diffractometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and UV-visible spectroscopy. The efficiency of the photodegradation reaction of OG was found to follow pseudo-first-order kinetics (Langmuir-Hinshelwood model) with a rate constant of 0.0338 min-1 and an R2 of 0.9906. Scavenger experiments revealed that hydroxyl radicals and superoxide anion radicals were the dominant species in the OG photocatalytic oxidation mechanism. This work provides a new method for designing highly efficient heterostructure-based photocatalysts (γ-Fe2O3 Nps/TiO2) based on LED light irradiation for environmental applications.

Adsorptive removal of acid blue dye 113 using three agricultural waste biomasses: The possibility of valorization by activation and carbonization - A comparative analysis

The presence of various organic and inorganic contaminants in wastewater leads to serious health effects on humans and ecosystems. Industrial effluents have been considered as noticeable sources of contaminating water streams. These effluents directly liberate the pollutants such as dye molecules and heavy metal ions into the environment. In the present study, three biowaste materials (groundnut shell powder, coconut coir powder and activated corn leaf carbon) were utilized and compared for the removal of acid blue dye 113 from aqueous solutions. The characterization study of newly prepared sorbent material (H3PO4-activated corn leaf carbon) and the other utilized sorbents was carried out by Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectrophotometer (FTIR), along with Energy Dispersive X-Ray (EDX) Analysis. The influence of experimental conditions such as pH, initial dye concentration, temperature, contact time, and sorbent dosage on the removal efficiency of the dye were appraised. The adsorption isotherm and kinetic result of acid blue dye 113 adsorption onto the sorbents best obeyed from Sips and pseudo-second-order kinetic model. Overall, the outcomes confirmed that the newly synthesized sorbent material (carbonized H3PO4-activated corn leaf) has superior adsorption capacity, rapid adsorption, and higher suitability for the removal of toxic dyes from the contaminated waters.

Efficient Removal of Carcinogenic Azo Dyes from Water Using Iron(II) Clathrochelate Derived Metalorganic Copolymers Made from a Copper-Catalyzed [4 + 2] Cyclobenzannulation Reaction

A novel synthetic strategy is disclosed to prepare a new class of metalorganic copolymers that contain iron(II) clathrochelate building blocks by employing a mild and cost-effective copper-catalyzed [4 + 2] cyclobenzannulation reaction, using three specially designed diethynyl iron(II) clathrochelate synthons. The target copolymers CBP1-3 were isolated in high purity and excellent yields as proven by their structural and photophysical characterization, namely, Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and UV-VIS absorption and emission spectroscopies. The thermogravimetric analysis (TGA) of CBP1-3 revealed an excellent chemical stability. Investigation of the adsorption properties of the target copolymers towards the carcinogenic methyl red dye from aqueous solution revealed a quantitative uptake in 30 min. Isothermal adsorption studies disclosed that methyl red uptake from aqueous solution followed the Langmuir model for all of the target copolymers, reaching a maximum adsorption capacity (q_m) of 431 mg g^-. Kinetic investigation revealed that the adsorption followed pseudo-first-order with an equilibrium adsorption capacity (q_e,cal) of 79.35 mg g^- and whose sorption property was sustained even after its reuse several times.

Investigation of boron-doped graphene oxide anchored with copper sulphide flowers as visible light active photocatalyst for methylene blue degradation

The non-biodegradable nature of waste emitted from the agriculture and industrial sector contaminates freshwater reserves. Fabrication of highly effective and low-cost heterogeneous photocatalysts is crucial for sustainable wastewater treatment. The present research study aims to construct a novel photocatalyst using a facile ultrasonication-assisted hydrothermal method. Metal sulphides and doped carbon support materials work well to fabricate hybrid sunlight active systems that efficiently harness green energy and are eco-friendly. Boron-doped graphene oxide-supported copper sulphide nanocomposite was synthesized hydrothermally and was assessed for sunlight-assisted photocatalytic degradation of methylene blue dye. BGO/CuS was characterized through various techniques such as SEM-EDS, XRD, XPS, FTIR, BET, PL, and UV-Vis DRS spectroscopy. The bandgap of BGO-CuS was found to be 2.51 eV as evaluated through the tauc plot method. The enhanced dye degradation was obtained at optimum conditions of pH = 8, catalyst concentration (20 mg/100 mL for BGO-CuS), oxidant dose (10 mM for BGO-CuS), and optimum time of irradiation was 60 min. The novel boron-doped nanocomposite effectively degraded methylene blue up to 95% under sunlight. Holes and hydroxyl radicals were the key reactive species. Response surface methodology was used to analyze the interaction among several interacting parameters to remove dye methylene blue effectively.

Secondary bond interface assembly of polyethyleneimine on zein microparticles for rapid adsorption of Reactive Black 5

Textile dye wastewater has the characteristics of high concentration, complex composition and changeable color degree and pH, which is difficult to be effectively and completely treated, and easy to cause environmental pollution. Here, a strategy of secondary bond interface assembly of polyethyleneimine on zein microparticles (PEI) (PEI@zein) was constructed to achieve rapid and efficient removal of Reactive Black 5 (RB5), which is one of the most widely used reactive dyes in the textile industry. Structural analysis indicated that the as-prepared PEI layer immobilized on zein microparticles was constructed based on the interface assembly dominated by hydrophobic interactions and electrostatic attraction between PEI molecules and zein chains. The novel interface showed excellent absorption performance for RB5 with an absorption capacity of 631.0 mg·g^-1, rapid adsorption in 2 min, wide pH range of 4-10. Mechanism analysis suggested the effective adsorption of RB5 by PEI@zein microparticles was mainly attributed to secondary bond interface such as electrostatic interaction and hydrogen bond between RB5 and PEI immobilized on the surface of zein microparticles. Moreover, due to the presence of secondary bond interface, RB5 adsorbed on microparticles can be easily desorbed by using 0.01 M NaOH. Therefore, the strategy of secondary bond interface assembly with polyethyleneimine on zein microparticles has high potential for practical application in the treatment of dye-containing wastewater.

Performance of Dye Removal from Single and Binary Component Systems by Adsorption on Composite Hydrogel Beads Derived from Fruits Wastes Entrapped in Natural Polymeric Matrix

The treatment of contaminated water is currently a major concern worldwide. This work was directed towards the preparation of a composite hydrogel by entrapping cherry stones powder on chitosan, which is known as one of the most abundant natural polymers. The synthesized material was characterized by scanning electron microscopy, by Fourier transform infrared spectroscopy, and by the point of zero charge determination. Its ability to remove two azo dyes models (Acid Red 66 and Reactive Black 5) existing in single form and in binary mixture was evaluated. Response Surface Methodology-Central Composite Design was used to optimize three parameters affecting the process while targeting the lowest final contaminant concentrations. The best results were obtained at pH 2, an adsorbent dose of 100 g/L, and a temperature of 30 °C, when more than 90% of the pollutants from the single component systems and more than 70% of those of the binary mixtures were removed from their aqueous solutions. The adsorption process was in accordance with Elovich and pseudo-second-order kinetic models, and closely followed the Freundlich and Temkin equilibrium isotherms. The obtained results led to the conclusion that the prepared hydrogel composite possesses the ability to successfully retain the target molecules and that it can be considered as a viable adsorbent material.

Enhancement of photocatalytic efficacy by exploiting copper doping in nano-hydroxyapatite for degradation of Congo red dye

This research deals with the photocatalytic activity of hydroxyapatite and the improvement of efficiency by doping various percentages of copper; the catalysts were synthesized by the wet-chemical method. Pure and copper-doped photocatalysts were characterized by several techniques including X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), dynamic scanning calorimetry (DSC), and UV-Vis spectroscopy. The competency of pure and copper-doped hydroxyapatite as photocatalysts was assessed by their interaction with Congo red dye. The crystallographic parameters of the catalysts were also estimated by employing the XRD technique, and a relationship was established between the calculated parameters and photocatalytic performance. Crystallite size was calculated from various model equations, which revealed an acceptable crystallite size of 42-68 nm. Copper doping in hydroxyapatite impressively augmented the photocatalytic efficacy, for example 99% dye was degraded upon 0.63% Cu-doping compared to 75% for the pure HAp, which was exemplified not only by the reaction rate but also by the quantum yield. The degradation percentages changed with time but became fixed at 200 min. The molar extinction coefficient was estimated by employing the Beer-Lambert law and further utilized to compute the photonic efficiency of the catalysts. In the study of the photochemical reaction, a simplified reaction process was proposed, and the potentials of the conduction band and valence band were assessed, which influenced the activity. The doping of Cu in crystalline hydroxyapatite will enhance the photocatalytic activity towards Congo red dye under all experimental conditions.

One-Step Room-Temperature Synthesis of Bimetallic Nanoscale Zero-Valent FeCo by Hydrazine Reduction: Effect of Metal Salts and Application in Contaminated Water Treatment

The effect of initial salt composition on the formation of zero-valent bimetallic FeCo was investigated in this work. Pure crystalline zero-valent FeCo nanoparticles (NPs) were obtained using either chloride or nitrate salts of both metals. Smaller NPs can be obtained using nitrate salts. Comparing the features of the FeCo prepared at room temperature and the solvothermal method revealed that both materials are almost identical. However, the room-temperature method is simpler, quicker, and saves energy. Energy-dispersive X-ray (EDX) analysis of the FeCo NPs prepared using nitrate salts at room temperature demonstrated the absence of oxygen and the presence and uniform distribution of Fe and Co within the structure with the atomic ratio very close to the initially planned one. The particles were sphere-like with a mean particle size of 7 nm, saturation magnetization of 173.32 emu/g, and surface area of 30 m²/g. The removal of Cu²⁺ and reactive blue 5 (RB5) by FeCo in a single-component system was conformed to the pseudo-first-order and pseudo-second-order models, respectively. The isotherm study confirmed the ability of FeCo for the simultaneous removal of Cu²⁺ and RB5 with more selectivity toward Cu²⁺. The RB5 has a synergistic effect on Cu²⁺ removal, while Cu²⁺ has an antagonistic effect on RB5 removal.

Enhancing hydroxyl radical production from cathodic ozone reduction during the ozone-electrolysis process with flow-through reactive electrochemical membrane cathode

In this study, a flow-through ozone-electrolysis (O₃-electrolysis) process was developed by combining ozonation with an electrolysis using a porous reactive electrochemical membrane (REM) cathode. Due to the convection-enhanced mass transport and fast radial diffusion inside the small pores of REM cathodes, the rate of cathodic O₃ reduction to ozonide radicals (O₃^•-) was significantly enhanced, while the further cathodic O₃^•- reduction to oxygen was inhibited during the flow-through O₃-electrolysis process compared to the conventional mixed-tank O₃-electrolysis process. Consequently, more hydroxyl radicals (•OH) were formed from O₃^•- decay in water during the flow-through O₃-electrolysis process than the mixed-tank O₃-electrolysis process. Corresponding to the higher •OH yields from cathodic O₃ reduction, the flow-through O₃-electrolysis process substantially enhanced the abatement kinetics and efficiency of para-benzoic acid (pCBA, a model compound of ozone-resistant micropollutant) in a groundwater than conventional ozonation and the mixed-tank O₃-electrolysis process. These results suggest that the flow-through O₃-electrolysis process may provide a competitive treatment technology for micropollutant abatement in water treatment.

Corn Cob as a Green Support for Laccase Immobilization-Application on Decolorization of Remazol Brilliant Blue R

The high demand for food and energy imposed by the increased life expectancy of the population has driven agricultural activity, which is reflected in the larger quantities of agro-industrial waste generated, and requires new forms of use. Brazil has the greatest biodiversity in the world, where corn is one of the main agricultural genres, and where over 40% of the waste generated is from cobs without an efficient destination. With the aim of the valorization of these residues, we proposed to study the immobilization of laccase from Aspergillus spp. (L_Asp) in residual corn cob and its application in the degradation of Remazol Brilliant Blue R (RBBR) dye. The highest yields in immobilized protein (75%) and residual activity (40%) were obtained at pH 7.0 and an enzyme concentration of 0.1 g.mL⁻¹, whose expressed enzyme activity was 1854 U.kg⁻¹. At a temperature of 60 °C, more than 90% of the initial activity present in the immobilized biocatalyst was maintained. The immobilized enzyme showed higher efficiency in the degradation (64%) of RBBR dye in 48 h, with improvement in the process in 72 h (75%). The new biocatalyst showed operational efficiency during three cycles, and a higher degradation rate than the free enzyme, making it a competitive biocatalyst and amenable to industrial applications.

Natural Fiber-Reinforced Thermoplastic ENR/PVC Composites as Potential Membrane Technology in Industrial Wastewater Treatment: A Review

Membrane separation processes are prevalent in industrial wastewater treatment because they are more effective than conventional methods at addressing global water issues. Consequently, the ideal membranes with high mechanical strength, thermal characteristics, flux, permeability, porosity, and solute removal capacity must be prepared to aid in the separation process for wastewater treatment. Rubber-based membranes have shown the potential for high mechanical properties in water separation processes to date. In addition, the excellent sustainable practice of natural fibers has attracted great attention from industrial players and researchers for the exploitation of polymer composite membranes to improve the balance between the environment and social and economic concerns. The incorporation of natural fiber in thermoplastic elastomer (TPE) as filler and pore former agent enhances the mechanical properties, and high separation efficiency characteristics of membrane composites are discussed. Furthermore, recent advancements in the fabrication technique of porous membranes affected the membrane's structure, and the performance of wastewater treatment applications is reviewed.

Mixed industrial wastewater treatment by the combination of heterogeneous electro-Fenton and electrocoagulation processes

Mixed industrial wastewater treatment efficiency of combined electro-Fenton (EF) and electrocoagulation (EC) processes was investigated in the present study. Alkali modified laterite soil was used as a heterogeneous EF catalyst and found superior performance than the raw laterite soil. Initially, the effect of catalyst dosage, initial pH, and applied voltage on the performance of EF process was carried out. A total of 54.57% COD removal was observed after 60 min of the EF treatment. Further treatment was carried out with EC process at different voltages. A total of 85.27% COD removal after 2 h treatment was observed by combining two electrochemical processes. Performance of EF followed by EC (EF + EC) process was compared with EC followed by EF (EC + EF) process. Even though efficiency is the same, EF + EC is a better strategy than EC + EF as it nullifies the neutralization requirement after EF process in addition to high mineralization efficiency, enhanced biodegradability, and lesser sludge generation.