Removal Of Anionic Azo Dyes Research Articles

A facile synthesis of bimetallic Ni/Co-BTC hollow MOFs for effective removal of congo red

ABSTRACT In this work, we employ an eco-friendly and highly efficient method for the successful removal of anionic azo dye (CR) using emerging Ni/Co-BTC hollow Metal-Organic Frameworks (MOFs). The MOFs was developed via a solvothermal synthesis method. Various kinetic models, adsorption capacities, isotherms (Langmuir and Freundlich), and thermodynamic stability assessments were used to predict the adsorption mechanism and the types of interactions present between CR dyes and Hollow MOFs. Our findings suggest that the adsorption process follows Freundlich isotherm, with PSO kinetic models indicating chemisorption and a maximum Langmuir adsorption capacity of 168.03 mgg−1. We observed a removal efficiency of 74% in neutral medium and 85% in acidic medium. Thermodynamic studies reveal the spontaneity of the process with endothermic enthalpy, attributed to the hydrogen bonding and electrostatic interactions between the dye molecule and the adsorbent. Furthermore, to investigate practical applicability, we conducted studies in real water and dye mixtures. All studies demonstrated that the prepared Ni/Co-BTC hollow MOFs show promising potential adsorbents for the CR dye removal from the wastewater, owing to their high efficiency and reusability.

Performance of Mg/Al and Zn/Al Hydroxide Double Lamellar-Bentonite for Removal of Anionic Azo Dye from Aqueous Solution

This paper presents the preparation and characterization of bentonite coated with hydroxide double lamellar Mg/Al-bentonite and Zn/Al-bentonite as a potential adsorbent material. The coating process involved co-precipitation of mixed metal nitrate solution (Mg-Al) or (Zn-Al), followed by immersion of bentonite (B-Na+) dispersion. The structures and morphologies of the coated bentonites were characterized using XRD, FTIR, BET, and SEM analysis. The results of the BET analysis indicate that Mg/Al-bentonite and Zn/Al-bentonite have larger surface areas and pore volumes compared to bentonite alone. Specifically, the surface area of Mg/Al-bentonite is 209.25 m2/g with a pore volume of 0.423 cm3/g, while Zn/Al-bentonite has a surface area of 175.95 m2/g and a pore volume of 0.313 cm3/g. In contrast, the surface area and pore volume of bentonite alone are 110.43 m2/g and 0.132 cm3/g, respectively. The Mg/Al-bentonite reaches 85% uptake within 3 h (equivalent to 724.20 mg/g at 25 °C and pH 7), achieving rapid equilibrium. In contrast, the Zn/Al-bentonite achieves a maximum adsorption of 74% within 5 h under identical pH and temperature conditions, corresponding to 650.34 mg/g. The error function values, including the correlation coefficient R2, chi-square test χ2, and residual sum of squares RSS, were calculated to evaluate both kinetic and isotherm models. The kinetic adsorption data agreed well with a pseudo-second-order model. The adsorption process followed the Sips isotherm model, and the monolayer adsorption capacity of Mg/Al-bent and Zn/Al-bent composites was 872.41 (R2 = 0.974) and 678.45 mg/g (R2 = 0.983), respectively. The thermodynamic analysis of the adsorption process revealed that it occurred spontaneously with an endothermic characteristic. The parameters ΔS, ΔH, and ΔG were used to determine this.

Removal of anionic azo dye from wastewater using Fe3O4 magnetic nanoparticles adsorbents in a batch system

This work investigates removing the anionic azo dye from wastewater using Fe3O4 magnetic nanoparticle adsorbents in a batch system. The effects of adsorbent dosage (0.1–0.5 g/L), pH (2−10), dye concentration (5–45 mg/L), contact duration (0–140 min), and shaking speed (100–180 rpm) on the removal (adsorption) efficiency at 23 °C were investigated. Besides the kinetic and isothermal studies were applied as well to improve commercial adsorbents’ performance in removing anionic dyes. Fe3O4 magnetic nanoparticles achieve a maximum azo dye removal (adsorption) efficiency of 99.99% at the optimum values of the investigated parameters: 3 g/L of adsorbent dose, 5 mg/L dye concentration, pH 2, and 180 rpm in 120 min at 23 °C. Langmuir adsorption isotherm has the highest correlation coefficient (R2 = 0.977) compared to Freundlich, and Temkin isotherms; the maximum absorption of azo dye is estimated to be 0.4158 mg/g. The values of the equilibrium parameter (RL) in the Langmuir isotherm model are between 0 and 1, indicating the Langmuir isotherm's favorability. The Fe3O4 magnetic nanoparticle adsorption rates follow pseudo-first-order adsorption kinetics, with R2 = 0.973.

Dual-functional Polyvinylidene Fluoride Beta Cyclodextrin-Grafted Graphene Oxide Mixed Matrix Membranes for Removal of Anionic Azo Dyes

Mixed matrix PVDF polymeric membranes were incorporated with β–CD grafted graphene oxide (GO) nanocomposites (β–CD-g-GO) via nonsolvent induced phase separation method and used in the adsorption of congo red (CR) and methyl orange (MO) dyes. The incorporation of β–CD-g-GO (6 wt%) was found to improve the membrane physico-chemical properties and performance. The water content was increased by 24.26%, contact angle reduced from 84.17 to 62.97° while flux increased from 12.42 to 275.03 L m−2 h−1 bar−1. The membranes were able to remove 100% of CR at pH 7 and 99.4% of the MO dye at pH 5 within 240 min. The adsorption kinetics and isotherms were well fitted to the pseudo second-order kinetic model and Freundlich isotherm model respectively. These results indicated that the adsorption of both dyes occurred via chemisorption and in a multilayer on a heterogeneous surface of the membranes. According to these findings, it was concluded that the adsorption mechanism was due to hydrogen bonding interactions between nitrogen and hydroxyl groups, inclusion complexation introduced by β–CD molecules and electrostatic interactions, between the negatively charged oxygen-containing groups of the membrane and the positively charged nitrogen and azo-linkages of the dye molecules. PVDF/β–CD-g-GO membranes have shown excellent adsorption efficiency towards azo dyes. This work indicates that the embedding of adsorptive GO-β–CD nanocomposites in PVDF membranes can remove anionic dyes from wastewater treatment.

Decoration of silver on ZnS for enhancement of sunlight-driven photodegradation of reactive red azo dye and norfloxacin antibiotic

High charge carrier recombination rate is the major difficulty affecting low photocatalytic performance of the UV-responsive ZnS photocatalyst. To overcome the problem, well dispersion of noble metals on the ZnS surface can be regarded as one of the useful strategies to enhance the photocatalytic efficiency. This is due to a synergy of creation of heterojunction structure and surface plasmon resonance effect. In the present work, the surface of the hydrothermally grown ZnS photocatalyst was modified with 10 wt %silver. The hexagonal Ag/ZnS photocatalyst provided high sunlight-active photocatalytic performance toward removal of anionic azo dye and norfloxacin antibiotic with the efficiency of about 99 % and 70 %, within 120 min, respectively. The improvement of the resultant photoactivity is attributed to increasing of charge separation capacity at the interface. Well distribution of silver on ZnS surface results in the generation of the Schottky barrier at the Ag/ZnS interface. This will end up with the increment of quantum efficiency and enlargement of the photocatalytic activity. Additionally, after modification of ZnS surface by addition of silver, a red shift in the light absorption toward visible region was found. This is assigned to the effect of surface plasmon resonance (SPR) of Ag on ZnS surface. The synthesized Ag/ZnS reveals high structural stability with enhanced performance even after the fifth cycle. This work demonstrates a new avenue for creation of a silver-modified ZnS for complete degradation of toxic organic contaminants including dyes and antibiotics by use of the abundant solar energy.

Unveiling the Synergistic Effect of Magnetite and ZrPO4 for Highly Selective Removal of Anionic Azo Dyes via an Ion-Exchange Process

Unveiling the Synergistic Effect of Magnetite and ZrPO₄ for Highly Selective Removal of Anionic Azo Dyes via an Ion-Exchange Process

Adsorptive removal of anionic azo dye by Al3+-modified magnetic biochar obtained from low pyrolysis temperatures of chitosan.

Magnetic γ-Fe2O3/Al3+@chitosan-derived biochar (m-Fe2O3/Al3+@CB) was prepared by introducing magnetic maghemite (γ-Fe2O3) nanoparticles and aluminum sulfate [Al2(SO4)3] into chitosan-derived biochar (CB) obtained at low pyrolysis temperatures. m-Fe2O3/Al3+@CB was used to remove typical anionic azo dye (Congo red, CR). Effects of initial CR concentration, contact time, initial pH value, background electrolytes, and temperature on CR adsorption by m-Fe2O3/Al3+@CB were studied. Compared with magnetic chitosan-derived biochar (m-Fe2O3@CB), m-Fe2O3/Al3+@CB exhibited excellent performance for a wider range of pH values (pH 1-7) and in the presence of background electrolyte. The introduction of Al3+ is an effective method for improving the properties of magnetic chitosan-derived biochar. High CR adsorption capacity (636.94mgg-1) of m-Fe2O3/Al3+@CB could result from collaborative effect of flocculation/coagulation and electrostatic attraction. These results demonstrated that m-Fe2O3/Al3+@CB is a potential adsorbent for effective removal of organic dyes from aqueous solution due to its high adsorption capacity and convenient magnetic recovery and stronger anti-interference ability against coexisting anions in wastewater.

Adsorption potential of pristine biochar synthesized from rice husk waste for the removal of Eriochrome black azo dye

Water contamination is a severe problem in today‘s world and it is progressively increasing day by day due to exponential industrial growth. The main contaminants found in water are dyes, heavy metals, pesticides, PFAS, etc. which are difficult to segregate with normal filtration units. In recent times, there has been a lot of focus on the removal of contaminants by ion exchange, filtration, distillation, adsorption, etc. Biochar derived from feedstock has been an excellent adsorbent and is therefore used in many applications like the removal of various heavy metals, azo dyes, inorganic and organic pollutants, etc. Azo dyes, which are mostly used in leather and textile industries are carcinogenic in nature, making them a great threat to mankind. In this article, we have synthesized pristine biochar at 600 °C through pyrolysis and explored its potential in the removal of anionic azo dye (Eriochrome black T). The biochar showed good porosity, as confirmed by FESEM images. The synthesized biochar showed excellent adsorption capacity for the 94 % removal of Eriochrome black T dye at 2.0 pH, 1.5 g catalyst dosage, 2 hr time, and 20 ppm initial dye concentrations. This work showed effective removal efficiency of pristine biochar in the removal of dyes from the contaminated water in the near future.

Different Adsorption Behaviors and Mechanisms of Anionic Azo Dyes on Polydopamine–Polyethyleneimine Modified Thermoplastic Polyurethane Nanofiber Membranes

Considering the notable mechanical properties of thermoplastic polyurethane (TPU), polydopamine–polyethyleneimine (PEI) -modified TPU nanofiber membranes (PDA/PEI-TPU NFMs) have been developed successfully for removal of anionic azo dyes. The adsorption capacity of PDA/PEI-TPU NFMs was evaluated using three anionic dyes: congo red (CR), sunset yellow (SY), and methyl orange (MO). Interestingly, it exhibited different adsorption behaviors and mechanisms of CR on PDA/PEI-TPU NFMs compared with SY and MO. With the decrease in pH, leading to more positive charges on the PDA/PEI-TPU NFMs, the adsorption capacity of SY and MO increased, indicating electrostatic interaction as a main mechanism for SY and MO adsorption. However, wide pH range adaptability and superior adsorption have been observed during the CR adsorption process compared to SY and MO, suggesting a synergistic effect of hydrogen bonding and electrostatic interaction, likely as a critical factor. The adsorption kinetics revealed that chemical interactions predominate in the CR adsorption process, and multiple stages control the adsorption process at the same time. According to the Langmuir model, the maximum adsorption capacity of CR, SY and MO were reached 263, 17 and 23 mg/g, respectively. After six iterations of adsorption–desorption, the adsorption performance of the PDA/PEI-TPU NFMs did not decrease significantly, which indicated that the PDA/PEI-TPU NFMs have a potential application for the removal of CR molecules by adsorption from wastewater.

A comprehensive review of anionic azodyes adsorption on surface-functionalised silicas.

Surface -functionalised silica networks are advanced adsorbents. They have been given much attention for treating wastewater using the adsorption technique due to the silanol reactivity, resulting in strong binding affinities towards many pollutants. This review discusses the removal of anionic azo dyes utilising various functional groups such as amines, surfactants, polymers, macrocyclic, and other chelating groups functionalised on silica's surface. This review also reveals the steadily increasing interest in surface-functionalised silicas as adsorbents, emphasising the scholarly advancements in this field as a platform for future research. For that, adsorption capacities with different experimental conditions have been compared. The possible adsorption mechanisms, rate-limiting step, and factors affecting the anionic azo dye adsorption process have been comprehensively discussed. This review discloses that adsorbent characteristics such as porosity and functional groups, besides structural properties of an anionic azo dye, significantly affect adsorption. The adsorption process followed the Langmuir isotherm and pseudo-second-order models, with a predominantly spontaneous and endothermic nature. Multiple interactions, including electrostatic interaction, π-π interactions, and hydrogen bonding, are observed between dyes and functionalised silicas, indicating the adsorption process's complexity. Regeneration and cost-economic analysis are also presented to provide a roadmap for sustainable improvements. Chemical and biological regeneration techniques restore > 80% of the spent functionalised silicas. There is a significant opportunity to improve their efficiencies and regenerability, resulting in surface-functionalised silicas being used commercially instead of only in the laboratory. Finally, future research has been proposed by identifying current research gaps, particularly concerning the application of functionalised silicas in wastewater treatment.

Thermodynamics, kinetics and isotherm studies on the removal of anionic Azo-dye (Congo red) using synthesized Chitosan/Moringa oleifera gum hydrogel composites

ABSTRACT Low cost and biocompatible hydrogels were synthesized using chitosan (CS) and Moringa oleifera (MO) gum biopolymers through Maillard reaction with glutaraldehyde as crosslinker. These CS/MO hydrogels were characterized using FT-IR spectroscopy and thermo gravimetric analysis (TGA). Equilibrium swelling behavior at different pH, temperature and salt solutions indicated almost equal swelling at all pH values, while higher swelling was observed at high temperature and low salt concentrations. Congo red dye, an azo dye, is potentially carcinogenic and can have different molecular structure at different pH. For its removal, variables including initial dye concentration, temperature, pH and contact time were optimized in order to achieve best adsorption capacity. The kinetics and isotherm studies suggested that the process of Congo red sorption on hydrogels was better fitted through pseudo second-order and Langmuir isotherm model. Maximum adsorption capacity of 50.25 mg/g was obtained at pH 2 as per Langmuir isotherm that represented a monolayer adsorption mechanism. The thermodynamic evaluation of the system suggested chemical nature of adsorption of dye. Since CS/MO hydrogels showed removal of more than 95% at all pH values along with ease of use, they could exhibit a potential of commercial utility in textile sectors for Congo red dye removal if further studies are conducted.

Active removal of anionic azo dyes (MO, CR, EBT) from aqueous solution by potential adsorptive capacity of zinc oxide quantum dots

AbstractBACKGROUNDOrganic dyes are extremely hazardous waste toxins because they can harm all living organisms as well as the environment. Among them, azo dyes are the most harmful, containing a non‐degradable azo group (NN); these dyes are highly hazardous for both humans and animals, even in low concentration. This research study aims to remove hazardous anionic azo dyes from aqueous solutions by a simple adsorption method using zinc oxide quantum dots (ZnO QDs) synthesized by a facile precipitation method.RESULTSAs synthesized, ZnO QDs were characterized by transmittance electron microscopy, atomic force microscopy, X‐ray powder diffraction, Fourier transform infrared spectroscopy, zeta potential and Brunauer–Emmett–Teller. The azo dyes Methyl Orange (MO), Congo Red (CR) and Eriochrome Black‐T (EBT) have been removed actively from an aqueous solution using the high adsorption characteristic of ZnO QDs. The results demonstrated that the adsorbent was efficient even at a low concentration at 0.05 g L−1. The maximum adsorption capacity of ZnO QDs at 27 ± 1 °C was 102.9, 124.3 and 60 mg L−1 for MO, CR and EBT, respectively, and all these results have been observed in just 30 min. A pseudo‐second‐order and Langmuir isotherm model satisfactorily suited the dye adsorption data and, up to three cycles, the ZnO QDs demonstrated outstanding reusability.CONCLUSIONZnO QDs showed not only efficient removal of individual dyes but also simultaneous removal of azo dyes from mixture solution and proved to be an effective, eco‐friendly, low‐cost adsorbent for dye decontamination in wastewater. © 2022 Society of Chemical Industry (SCI).

Biochar supported CuFe layered double hydroxide composite as a sustainable adsorbent for efficient removal of anionic azo dye from water

This study reports the synthesis of date palm waste-derived biochar (B) supported CuFe layered double hydroxides (CuFe LDH) composite by facile co-precipitation method. The adsorption performance of B-CuFe composite was evaluated for the removal of Eriochrome black T (EBT), as a model anionic azo dye, from the aqueous phase. The B-CuFe composites were characterized by FTIR, XRD, TGA, SEM-EDX and BET techniques. Characterization results revealed the synergistic effect of biochar and CuFe LDH has resulted in substantial improvement in physicochemical characteristics (i.e. surface functionality, surface area and surface morphology) of B-CuFe composite, which promotes rapid and improved adsorption of (EBT) from the solution. The B-CuFe composite with 2.5 g loading of biochar onto CuFe LDH - showed better adsorption performance than that of other B-CuFe composites. The adsorption process of EBT onto B-CuFe composite was well described by the RSM models (with R 2 = 0 . 964 – 0 . 999 ). Acidic pH (2–5) and higher temperature favored the adsorption of EBT onto B-CuFe composite, and almost (70–85%) of EBT was removed from the water within the first 15 min. The highest adsorption capacity, 565.32 mg/g of EBT onto B-CuFe composite, was obtained at pH 2.5 and 45 °C. The adsorption mechanism associated with the strong electrostatic and chemical interactions of EBT sulfonated anions (SO 3 − ) with protonated hydroxyl surface groups ( OH 2 + ) of B-CuFe composite. The B-CuFe composite exhibited better EBT removal in the presence of co-existing anions and demonstrated excellent reusability performance (11% reduction) after five successive cycles. The results demonstrated that the B-CuFe composite has a great potential to be employed as a sustainable and cost-effective adsorbent for the purification of dye contaminated water bodies. • Sustainable biochar-CuFe composite was fabricated by the coprecipitation method. • B-CuFe exhibited improved physicochemical properties than pure biochar and CuFe. • B-CuFe removed 85% of Eriochrome black T dye from the water in 15 min. • The maximum adsorption capacity of B-CuFe was 565.32 mg/g at 45 °C. • B-CuFe composite exhibited excellent reusability performance.

Removal of Anionic Azo Dye from Aqueous Solution Using the Magnetic NiFe2O4 Decorated-Exfoliated Graphite

Environmental issues have recently become more prevalent with the rapid development of global industrialization. Organic dyes, a common pollutant, are compounds which are constituted by benzene rings, making them stable and presenting a pollution source that is harmful to human health. In this study, a new nanocomposite adsorbent was fabricated using exfoliated graphite (EG) and NiFe2O4 and evaluated for adsorption capacity against Congo Red (CR) dye. A number of reaction parameters (pH, CR concentration, dosage and contact time) that affect CR adsorption were considered. The successful synthesis of EG@NiFe2O4 was confirmed by FT-IR analysis. Herein, EG@NiFe2O4 and NiFe2O4 adsorbent with dosage of 0.5 g/L were used to removal 100 mL of CR dye at the concentration of 50 ppm. The results showed that adsorption equilibrium was achieved after 120 min for both adsorbents (EG@NiFe2O4 and NiFe2O4). The optimal working pH for adsorption using EG@NiFe2O4 and NiFe2O4 was 6 and 4 respectively. EG@NiFe2O4 could be reused for up to three times without significant loss of adsorption capacity.

Removal of anionic azo dyes from aqueous solutions by quaternary ammonium salt-functionalized fibers with adjustable surface microenvironments

Adsorption is one of the most effective methods to remove organic pollutants from water. A series of functionalized fiber adsorbents with cationic adsorption sites and different hydrophobic alkyl chains have been prepared by immobilizing quaternary ammonium salts (QASs) on polyacrylonitrile fiber (PANF). The hydrophobicities of these QAS-functionalized fibers were evaluated by water uptake and contact angle analysis. These fibers were employed to remove anionic azo dyes (methyl orange, alizarin yellow R and methyl red from water. The fiber with a twelve-carbon alkyl chain (designated PANQAS-12F) had the highest adsorption capacity for MO and the maximum adsorption capacity (Qe) is 1.82 mmol g-1. The PANQAS-12F dye adsorption process follows second-order kinetics and correlates with a Langmuir model. A possible adsorption mechanism that proposes electrostatic interactions as the primary interactive force and hydrophobic and weak hydrogen bonding interactions as secondary forces is presented. The QAS-functionalized fiber can be reused ten times while still maintaining a removal rate of 99% or higher. The QAS-functionalized fiber is also very suitable for continuous flow processes giving a MO removal rate of more than 90% for the treatment up to 1020 mL of MO-containing water. These QAS-functionalized fibers have very promising application potential.

Synthesis of a novel polysuccinimide based resin for the ultrahigh removal of anionic azo dyes from aqueous solution

A novel hyper-cross-linked polyamide resin (PSI-PA) has been synthesized for the ultrahigh removal of Congo red (CR) and Eriochrom Black T (EBT) from aqueous solution. The mesoporous resin, having a specific surface area (98.80 m2 g−1), showed maximum adsorption capacity (Qmax) of 522.18 mg g−1 for CR (pH 9.0) and 460.34 mg g−1 for EBT (pH 6) at room temperature. The adsorption of these dyes was rapid and the equilibrium was attained within 4 h. The kinetic data was well-fitted by pseudo-second-order rate equation. Analysis of the surface chemical composition of loaded PSI-PA by XPS revealed the appearance of a new peak at around 166.0 eV (S 2p), confirming the adsorption of the sulfur-based dyes onto the resin. Examination of experimental data of dyes adsorption by a variety of non-linear adsorption isotherms and kinetic models suggested that the Langmuir model exhibited the best fit with high correlation coefficients for both CR (R2 = 0.9966) and EBT (R2 = 0.9934). PSI-PA has been extensively characterized by FT-IR, solid state 13C (CP-MAS) NMR, EDS, TGA and BET analysis. Moreover, PSI-PA exhibited 82% removal efficiency for dyes in simulated effluents, manifesting its promise and utility for treating industrial effluent.

Adsorption behavior of dyes from an aqueous solution onto composite magnetic lignin adsorbent.

Magnetic lignosulfonate functional materials that were known to remove several types of dye from water effectively were prepared. The surface of an iron (II,III) oxide (Fe3O4) sample was coated with a layer of organic carbon, and magnetic lignosulfonate (FCS) was synthesised by a crosslinking agent. The morphology, structure, stability and magnetic properties of the materials were characterised by various testing methods. Under experimental conditions, the solution's acidity, alkalinity, contact time, temperature, desorption and dye concentration were measured. The experimental results show that the material reached the highest adsorption capacity at pH=7. In addition, the adsorption data was similar to that of a single layer, Langmuir adsorption model. The maximum adsorption capacities were 198.24mgg-1 (Congo Red) and 192.51mgg-1 (Titan Yellow), respectively. Based on its desorption performance, the material had good recyclability. Therefore, these studies could be used in wastewater treatment. Hopefully, the proposed magnetic composites will inspire more scholars to investigate solutions to the problem of contaminated water resources.

Bio-inspired N,S-doped siligraphenes as novel metal-free catalysts for removal of dyes in the dark

Bio-inspired porous Siligraphene (graphene-like SiC) catalyst and its N and N,S-doped SiC variants were synthesized via a low-temperature magnesiothermic method using natural precursors. The synthesized SiC catalysts were tested for the removal of anionic azo dyes (Congo red, Methyl orange, and Methyl red) in the dark. Si atoms in the siligraphene structure are more positive than C atoms due to the electronegativity of the latter. In doped structure, insertion of N and S atoms can further increase the positive charge of Si atoms and improve adsorption of oxygen and of the above anionic dyes on the surface of SiC. Thus, the catalytic activity of doped SiC for degradation of the dyes increased. A mechanism is proposed where O2 molecules chemisorb onto the surface of SiC, OO bond length elongates, oxygen bond dissociates and radicals are produced. Quenching experiments show that •O2– and •OH radicals are the main reactive species in this process. Doping of nitrogen and sulfur in the presence of Si atoms in siligraphene structure has been shown to improve its capacity for dye removal compared to the corresponding carbon catalysts. Moreover, the SiC catalysts display good stability so that their performance did not significantly decrease even in continuous operation.

Magnetically Separable Fe3O4/BiOBr Microspheres: Synthesis, Characterization, and Photocatalytic Performance for Removal of Anionic Azo Dye

Abstract Recyclable magnetic Fe3O4/BiOBr microspheres (m-Fe3O4/BiOBr MSs) were synthesized by a simple solvethermal method. The crystals' optical, morphology, and magnetic properties of m-Fe3O4/BiO...

The preparation of organophosphorus ligand-modified SBA-15 for effective adsorption of Congo red and Reactive red 2.

P,P-bis (2-oxooxazolidin-3-yl)-N-(3-(triethoxysilyl)propyl)phosphinic amide (APTES-BOP)-modified SBA-15 (SBA-15-BOP) was prepared by a post-synthesis grafting method for the removal of anionic azo dyes from aqueous solutions. The properties of the prepared adsorbent were characterized by PXRD, FT-IR, SEM, TEM, nitrogen sorption, and elemental analysis. Adsorption equilibrium and adsorption kinetic studies demonstrated that the experimental data fitted well with the Langmuir isotherm model and pseudo-second-order model. According to Langmuir fitting, SBA-15-BOP showed high adsorption capacity for CR and RR2 dyes, with the maximum adsorption capacities of 518.1 mg g−1 and 253.8 mg g−1, respectively. The thermodynamic study indicated that the adsorption processes of CR and RR2 dyes on SBA-15-BOP were spontaneous and exothermal. The prepared SBA-15-BOP can be a promising adsorbent for the removal of anionic dyes from aqueous solutions.