Dye Removal Performance Research Articles

Degradation of Rhodamine B by Visible Light Driven MoO3@TiO2 Core-Shell Photocatalyst.

In this study, a MoO3@TiO2 composite core-shell material was developed to remove Rhodamine B (RhB) dye through synergistic adsorption and photocatalytic degradation. n-n heterostructures were formed by coupling n-type semiconductors to enhance the efficiency of photocarrier separation and photocatalytic performance. MoO3, which possesses strong adsorption capacity, was primarily used as a dye adsorbent. Additionally, the formation of an n-n heterojunction with TiO2 enabled MoO3 to expand the photocorresponding range of TiO2, leading to the generation of superoxide (O2•) and hydroxyl (•OH) free radicals for dye degradation. The experimental results demonstrate that the MoO3@TiO2 core-shell composite exhibits excellent performance for RhB dye removal, with adsorption and degradation rates reaching 35.7 and 70.3%, respectively, even at low catalyst concentrations. This approach offers new insights into the development of MoO3 core-shell photocatalysts.

A Novel BiOBr/CAU-17 Composite with Enhanced Photo-Catalytic Performance for Dye Degradation and Removal of Tetracycline Antibiotic Under Visible Light.

In order to improve the low specific surface area and high recombinant light generation carriers of BiOBr, loading BiOBr onto suitable Metal Organic Frameworks (MOFs) is an effective strategy to unleash its efficient visible light response and intrinsic catalytic activity. In this study, using classic MOF CAU-17 as a precursor, using a straightforward co-precipitation technique, four BiOBr/CAU-17 composites with distinct MOF contents values BCAU-1, BCAU-2, BC, AU-3, and BCAU-4 were created, and their photo-catalytic characteristics were examined. The BCAU-2 composite exhibited much higher photo-catalytic degradation efficiency for Rhodamine B (RhB) and Tetracycline (TC) than the pristine materials, counter compositions, and early reported materials. XRD, SEM, TEM, XPS, and EDX results revealed the strong synergistic photo-catalytic effect of BiOBr and CAU-17. The photocatalytic degradation of TC was significantly enhanced by the BiOBr bimetal modification, with the 2 wt.% BiOBr/CAU-17 nanocomposite achieving an 87.2 % degradation of TC and 82 % Total Organic Carbon (TOC) removal within 60 min. The high photo-degradation efficiency of BCAU-2 composite should be attributed to the efficient transfer of photo-generated carriers at interfaces and the synergistic effect between BiOBr/CAU-17. Furthermore, the experiments on the capture of the active species proved that the main active free radicals involved in the degradation of RhB and TC are attributed to the photo-induced holes h+ and ⋅ O2 - under visible light. The catalyst's efficacy is corroborated by the outcomes of photoluminescence spectroscopy and photo current response. This study offers a new understanding for the design of green synthesis schemes for photo-catalytic dye degradation and removal of certain antibiotics from the aquatic environment.

Performance optimisation of new basket-shaped TiO2 photoelectrodes in a photocatalytic fuel cell utilising the response surface method: dye elimination and energy generation

ABSTRACT Response Surface Methodology (RSM) simplifies fuel cell design and offers possibilities for process improvement, operating condition optimisation, and performance improvements. By identify the best design parameters, RSM helps create fuel cell systems that are dependable, economical, and efficient. Although RSM is widely applied in many domains, more studies are still needed evaluating photocatalytic fuel cell performance in dye removal and optimising the conditions of reactions. Using RSM (central composite design), the system's ability to remove Methyl Orange (MO) and produce energy was enhanced in this study. TiO2/Ti and CuO/Cu are employed in this system as the photoelectrodes. Effective optimised parameters on contaminant removal and energy production, including dye concentration, electrolyte concentration, and pH, were achieved as 23.31 mg/L, 0.1 M, and pH = 3, respectively. 71.26% MO dye was removed, and 0.63 V, 0.19 mA/cm2, and 0.037 mW/cm2 values were recorded for the open-circuit voltage (VOC), short-circuit current (JSC), and maximum power density (PMAX), respectively, under optimal conditions, which was very close to the experimental values. The analysis of variances for dye removal and VOC, JSC, PMAX, correlation coefficient, and adjusted correlation coefficient for the four mentioned responses indicated a strong correlation between the predicted and experimental data, confirming the model's accuracy.

Removal of Remazol Red Dyes Using Zeolites-Loaded Nanofibre Coated on Fabric Substrates

Nanofibre-based membranes have shown great potential for removing textile wastewater due to their high porosity and surface area. However, nanofibre membranes exhibit lower dye removal efficiency. Hence, this study aims to improve the dye removal performance of nanofibre membranes by incorporating zeolites. The research involved fabricating composite membranes by electrospinning polyvinyl alcohol (PVA) nanofibres incorporated with zeolites. Mechanical strength was enhanced by placing the PVA/zeolite nanofibre membrane between fusible nonwoven interfacing and woven polyester fabric, followed by heat treatment. Morphological analysis revealed the uniform dispersion of zeolite particles within the PVA nanofibres. EDX analysis confirmed the successful incorporation of zeolites into the fibres. Among all membrane samples, the PZ-0.75 membrane exhibited the highest pure water flux (PWF) with approximately 1358.57 L·m−2·min−1 for distilled water and 499.85 L·m−2·min−1 for batik wastewater. Turbidity of batik wastewater increased proportionally with zeolite concentration, with removal rates of 84.79%, 78.8%, 76.96%, and 74.19% for PZ-0.75, PZ-0.5, PZ-0.25, and PVA membranes, respectively. Furthermore, the UV/Vis spectrophotometer demonstrated that dye removal efficiency increased from 2.22% to 8.89% as the zeolite concentration increased from 0% to 0.75%. In addition, the PZ-0.75 membrane effectively removed RR dye at a concentration of 1 mg/L, with an optimal contact time of approximately 60 min. The adsorption mechanism of the PZ-0.75 membrane aligns with the Freundlich model, with an R2 value of 0.983. Overall, this study demonstrates the efficiency of zeolite in the fabric substrates to improve the filtration and adsorption properties for wastewater treatment, particularly in textile industries.

Dye Removal From Tannery Wastewater Utilizing Footwear Waste: A Sustainable Approach

ABSTRACTWaste‐to‐3R (reduce, reuse, and recycle) is a promising mass balance approach in the leather sector for addressing the current challenge of overproduction of rubber sole waste in the footwear industry and dye pollution in tanneries. In this study, low‐cost charcoal derived from discarded natural rubber (NR) soles was effectively employed to remove anionic and cationic dyes from a model tannery dye solution, aligning with mass balance approaches in the leather sector. Discarded rubber charcoal (DRC) was prepared at 350°C using a self‐fabricated pyrolytic cell. The resulting charcoal was then dried, ground, and separated through 40‐mesh size lab‐scale sieves, and it was subsequently employed for the removal of dyes from tannery wastewater. The dye removal performance was optimized by adjusting parameters such as dosage, pH, contact time, and concentration. The maximum adsorption capacity and removal efficiency of the anionic acid dye (AD) were found to be 158.22 mg/g and 88.39% at pH 1, respectively, while those of the cationic methylene blue dye were 166.18 mg/g and 85.53% at pH 12, respectively, between 15 and 30 min, depending on the DRC conditions. Fresh charcoal and dye‐loaded charcoal were characterized through Fourier transform infrared spectroscopy, x‐ray diffraction, Brunauer–Emmett–Teller, scanning electron microscope (SEM), and transmission electron microscope with Energy‐Dispersive X‐ray (EDX) Spectroscopy for respective functional groups and morphology studies, and zeta potential measurements were employed to characterize the charcoal surface charge. The SEM image revealed that the shape of the DRC particles resembles a honeycomb structure, with an average size of 573.56 µm. The adsorption kinetic study indicates that the Freundlich isotherm model and pseudo‐second‐order kinetics were well‐fitted for dye removal in this study. The charcoal exhibited robust stability, retaining its capacity of 57.42 mg/g of AD and 44.94 mg/g of MB dye after four reuse cycles. This resilience was observed in treatment with various desorption agents, including HCl, CH3COOH, NaOH, and C2H5OH. The findings of this study suggest that NR‐derived charcoal could be used as a successful substitute for commercial activated carbon in wastewater treatment to get rid of the acid and basic dyes of the leather industry. Based on the observed results, a plausible mechanism was also proposed.

Photocatalytic nanohybrid UV-light-driven PVDF/GO-NiFe@SiO2 membrane coupled with bentonite adsorption and ozonation process for a sustainable textile wastewater treatment

The textile industries face significant environmental challenges due to the presence of complex pollutant dyes in its wastewater, making it one of the world's major sources of industrial water pollution. Numerous studies have been employed to overcome this problem, including physical, chemical, and biological treatments. However, most of those methods still suffered to achieve higher dye removal performance. This study provides new insight regarding textile wastewater treatment containing indigo red as the main colorant by carrying out a hybrid process combining bentonite adsorption, ozonation, and photocatalytic membrane filtration. For the membrane, we propose a modified polyvinylidene fluoride (PVDF) membrane incorporated with graphene oxide (GO) and nickel-iron doped silica (NiFe@SiO2) photocatalyst, which is named PVDF/GO-NiFe@SiO2 membrane. The membrane was employed under different sets of filtrations (dark and under ultraviolet irradiation) to treat natural dye wastewater from textile industry effluent. Further improvement was achieved when UV light irradiation was subjected to the process. This sequential adsorption-ozonation-membrane process under UV exposure exhibited improved dye removal from 55.11 % to 97.22 %. The results show that the proposed hybrid process successfully improved the membranes' antifouling behavior, thus boosting the membranes' performance and durability. From a broader perspective, our work promotes new insights for the integration of other physical, chemical, and biological treatment methods to improve the performance and durability of membrane-based processes, particularly for dye wastewater treatment.

Efficient Removal of Methylene Blue Dye from Aqueous Media Using Facilely Synthesized Magnesium Borate/Magnesium Oxide Nanostructures.

Methylene blue dye in water sources can pose health risks to humans, potentially causing methemoglobinemia, a condition that impairs the blood's ability to carry oxygen. Hence, the current study investigates the synthesis of novel magnesium borate/magnesium oxide (Mg3B2O6/MgO) nanostructures and their efficiency in removing methylene blue dye from aqueous media. The nanostructures were synthesized using the Pechini sol-gel method, which involves a reaction between magnesium nitrate hexahydrate and boric acid, with citric acid acting as a chelating agent and ethylene glycol as a crosslinker. This method helps in achieving a homogeneous mixture, which, upon calcination at 600 and 800 °C, yields Mg3B2O6/MgO novel nanostructures referred to as MB600 and MB800, respectively. The characterization of these nanostructures involved techniques like X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, N2 gas analyzer, and field-emission scanning electron microscope (FE-SEM). These analyses confirmed the formation of orthorhombic Mg3B2O6 and cubic MgO phases with distinct features, influenced by the calcination temperature. The mean crystal size of the MB600 and MB800 samples was 64.57 and 79.20 nm, respectively. In addition, the BET surface area of the MB600 and MB800 samples was 74.63 and 64.82 m2/g, respectively. The results indicated that the MB600 sample, with its higher surface area, generally demonstrated better methylene blue dye removal performance (505.05 mg/g) than the MB800 sample (483.09 mg/g). The adsorption process followed the pseudo-second-order model, indicating dependency on available adsorption sites. Also, the adsorption process matched well with the Langmuir isotherm, confirming a homogeneous adsorbent surface. The thermodynamic parameters revealed that the adsorption process was physical, exothermic, and spontaneous. The MB600 and MB800 nanostructures could be effectively regenerated using 6 M HCl and reused across multiple cycles. These findings underscore the potential of these nanostructures as cost-effective and sustainable adsorbents for methylene blue dye removal.

Biogenic Iron Oxide Nanoparticles Based on Algal Biofilm Formed in the Wastewater Treatment Plant and Their Dye Removal Performance

In the field of environmental pollution removal, bioremediation plays a crucial role in removing or converting toxic substances from the environment. Bacteria, yeasts, molds, algae, and plants are widely used in bioremediation events. Recently, green-synthesized nanoparticles have also been employed in bioremediation applications. In this study, iron oxide nanoparticles (FeONPs) were synthesized from algal biofilms that are naturally formed in the settling ponds of the Gümüşhane Municipality Wastewater Treatment Plant. These biological nanoparticles were utilized to investigate their adsorption efficiency for water-polluting dyes such as methylene blue (MB), malachite green (MG), and phenol red (PR). The synthesized FeONPs were characterized using Fourier transform infrared spectroscopy (FTIR) scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDX), and X-ray diffraction (XRD). To test their efficacy, MB, MG, and PR dye solutions were treated with 5.0, 10.0, and 20 g/L FeONP concentrations. The remaining dye concentrations were quantified with a UV-VIS spectrophotometer after filtration. The results showed that FeONPs obtained from algal biofilms effectively removed MB, MG, and PR, with the highest efficiency observed for PR.

Improved productivity and dye removal performance of Trametes versicolor pellets using rice husk as a co-substrate

Pellet production represents a critical step for several processes requiring fungal biomass, nevertheless, its optimization is seldom reported. The use of finely ground rice husk as a microcarrier and co-substrate permitted a marked increase (≈ 2.7×) in the productivity of fungal pellet production using Trametes versicolor compared to traditional production methods. The pellets show similar structure and smaller size compared to typical sole-mycelium pellets, as well as comparable laccase activity. The efficiency of the pellets for biodegradation was confirmed by the removal of the crystal violet dye, achieving significantly faster decolorization rates compared to the traditionally produced pellets. The use of these pellets during the continuous treatment of the dye in a stirred tank bioreactor resulted in 97% decolorization operating at a hydraulic residence time of 4.5 d.

Constructing sustainable keratin/algae biohydrogels for efficient removal of aniline blue via a pre-extrusion induced self-crosslinking strategy

Two environmentally friendly hierarchical porous biohydrogels, honeycomb keratin hydrogel (HKH) and spongy keratin-algae hydrogel (SKAH), were fabricated using an extrusion approach by using extruded keratin with or without algae. The extruded keratin exhibits exceptional self-crosslinking properties, making the biohydrogels behave with excellent adsorption performance for aniline blue dye removal from wastewater. In addition, the SKAH demonstrated a significantly higher maximum uptake capacity of 442.56 mg/g, surpassing that of the HKH (134.63 mg/g). This enhancement can be attributed to the looser porous structure of the SKAH, which enables better exposure of active groups within the material, which indicates the introduction of algae led to noticeable variations in the microstructure and performance of the adsorbent. Systematic investigation on the adsorption performance of isotherm and kinetics analyses indicated that chemisorption played a predominant role in governing the overall rate of adsorption. Overall, this extrusion approach allows for a simplified and non-toxic method of synthesizing these biohydrogels without the need for additional chemical reagents or biocross-linkers, promoting their eco-friendliness and reducing potential environmental impacts. The unique feature presents significant opportunity to fabricate sustainable and eco-friendly biohydrogel adsorbent for wastewater treatment.

Effective Removal of Nile Blue Dye from Wastewater using Silver-Decorated Reduced Graphene Oxide.

Nile blue (NB) dye is a highly toxic substance that when discharged into sewage presents a significant risk to the environment and human health. Carbon-based nanomaterials, such as graphene oxide (GO), reduced graphene oxide (rGO), and their nanocomposites, offer considerable potential for eliminating hazardous pollutants from aqueous systems. In this study, we have successfully fabricated bare GO and rGO, and then, the rGO was decorated with silver (Ag) nanoparticles to develop the Ag-rGO composite. The as-prepared materials were characterized by various techniques, such as UV-visible (UV-vis) and Fourier transform infrared (FTIR) spectroscopies, X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and scanning electron microscopy (SEM) to elucidate their structure, morphology, and chemical composition. The pollutant removal performance of the as-prepared materials was evaluated through a batch approach under the effect of various experimental variables for removal of NB dye from wastewater. As obvious, the Ag-rGO composite revealed exceptional performance for NB dye removal from wastewater, with a maximum removal percentage of 94% within 60 min, which is remarkably higher than those of the rGO (i.e., 59%) and GO (i.e., 22%), under the same experimental conditions. The adsorption data was analyzed with thermodynamics, isotherms, and kinetics models to better understand the physicochemical mechanisms driving the effective removal of the NB dye. The results reveal that Ag-rGO nanocomposite exhibit excellent adsorption ability as well as favorable thermodynamic and kinetic parameters for NB dye removal. It was also found that the presence of light enhanced the adsorptive removal of NB while using Ag-rGO as an adsorbent. The present study noted significant reusability of the Ag-rGO nanocomposite, likely due to minimal Ag leaching and/or the robust stability of the Ag-rGO. It is suggested that Ag-rGO-based hybrid materials could serve as promising candidates for efficiently adsorbing and catalytically removing various toxic pollutants from wastewater.

Fe3C and Fe3O4 decorated porous carbon as high volumetric capacitance/rate electrodes for supercapacitor

As the most attractive electrode for supercapacitors, renewable carbon-based material exhibits slow charge and discharge ability and low volumetric energy density, severely hindering its extended applications. Herein, a neotype and high-performance carbon-based nanocomposites were successfully prepared from Linum usitatissimum. L stems assisted with K4Fe(CN)6·3H2O through a green and straightforward high-temperature treatment method. Benefiting from the activation and decomposition of K4Fe(CN)6·3H2O, the carbon-based nanocomposite decorated by Fe3C and Fe3O4 possesses moderate porous volume, heteroatoms content, and graphitization degree. These characteristics endow the supercapacitor assembled from as-prepared carbon-based nanocomposite with fast charge/discharge ability, high volumetric capacitance (303.8 F cm−3, 1 A g−1), excellent rate performance (61.3%, 100 A g−1), and outstanding cycle life. Owing to abundant N/O-containing functional groups, high C=C content, and appropriate specific surface area, the resultant nanocomposite also exhibits excellent organic dye removal performance. Overall, this work offers a green and efficient avenue for designing multi-doped carbon-based nanocomposites in electrochemical energy storage and organic dye removal.

Natural Polysaccharide-Based Hydrogels Used for Dye Removal.

Removal of contaminants from discharge water is vital and demands urgent assistance with the goal to keep clean water. Adsorption is one of the most common, efficient, and low-priced methods used in water treatment. Various polysaccharide-based gels have been used as efficient dye adsorbents from wastewater. This review summarizes cutting-edge research of the last decade of different hydrogels based on natural polysaccharides (chitin, chitosan, cellulose, starch, pullulan, and dextran) concerning their dye adsorption efficiency. Beyond their natural abundance, attributes of polysaccharides such as biocompatibility, biodegradability, and low cost make them not only efficient, but also environmentally sustainable candidates for water purification. The synthesis and dye removal performance together with the effect of diverse factors on gels retaining ability, kinetic, and isotherm models encountered in adsorption studies, are introduced. Thermodynamic parameters, sorbent recycling capacity along with conclusions and future prospects are also presented.

Investigation of Polypyrrole and Polypyrrolepolyethyleneimine as Adsorbents for Methyl Orange Dye Adsorption

The present study has explored the adsorption properties of polypyrrole-based adsorbents (polypyrrole and polypyrrole-polyethyleneimine composite) as novel conducting polymers in adsorbing methyl orange (MO) (an anionic dye) effectively from aqueous solution. The adsorption characteristics of the prepared polymer-based adsorbents were characterized by BET, FTIR, FESEM, and XRD methods. The effectiveness of PPy-based adsorbents for MO dye adsorption was examined using the batch adsorption method. Different parameters were changed during the adsorption process, including contact time, solution pH, and adsorbent dosage. The highest BET surface area of the PPy-PEI composite was found to be 11.85 m2/g, which is much greater than that of the pristine PPy having 8.54 m2/g. The dye removal performance was obtained to be 79.1 % and 98.8 %, by pristine PPy adsorbent and PPy-PEI adsorbent, respectively, at the optimum condition of pH 3, adsorbent dosage of 0.1 g with a contact time of 120 minutes. The Langmuir isotherm model explained the adsorption data better than the Freundlich isotherm model, and the pseudo-second-order model adequately explained the kinetic data for both the adsorbents. The regeneration investigation demonstrated the effectiveness of reusing PPy-PEI composite adsorbents for up to three successive adsorption-desorption cycles. The prepared PPy-PEI composite adsorbents appeared to be very much effective in removing anionic dyes from aqueous solutions.

Waste treats waste: Facile fabrication of porous adsorbents from recycled PET and sodium alginate for efficient dye removal

Dye-contaminated water and waste plastic both pose enormous threats to human health and the ecological environment, and simultaneously solving these two issues in a sustainable and resource-saving way is highly important. In this work, a sodium alginate-polyethylene terephthalate-sodium alginate (SA@PET) composite adsorbent for efficient dye removal is fabricated using wasted PET bottle and marine plant-based SA via simple and energy-efficient nonsolvent-induced phase separation (NIPS) method. Benefiting from its porous structure and the abundant binding sites, SA@PET shows an excellent methylene blue (MB) adsorption capacity of 1081 mg g−1. The Redlich–Peterson model more accurately describes the adsorption behavior, suggesting multiple adsorption mechanisms. In addition to the electrostatic attractions of SA to MB, polar interactions between the PET matrix and MB are also identified as adsorption mechanisms. It is worth mentioning that SA@PET could be recycled 7 times without a serious decrease in performance, and the trifluoroacetic acid-dichloromethane solvent involved in the NIPS process has the possibility of reuse and stepwise recovery. Finally, the discarded adsorbent could be completely degraded under mild conditions. This work provides not only a composite adsorbent with excellent cationic dye removal performance for wastewater treatment, but also an upcycling strategy for waste PET.

Ball milling synthesis of Fe3O4 nanoparticles-functionalized porous boron nitride with enhanced cationic dye removal performance.

Enhancement of the adsorption performance and recyclability of adsorbents is a crucial aspect of water treatment. Herein, we used one-dimensional porous boron nitride (PBN) as a carrier to load Fe3O4 nanoparticles for the preparation of Fe3O4 nanoparticles-functionalized porous boron nitride (Fe3O4/PBN) via a ball milling method. The high-energy ball milling promoted the creation of a negatively charged PBN surface and facilitated the uniform distribution of Fe3O4 nanoparticles on the surface of PBN. The adsorption performance of Fe3O4/PBN toward cationic dyes could be significantly improved while no enhancement was observed for anionic dyes. The great adsorption performance of Fe3O4/PBN is due to its surface functional groups and surface defects formed in the ball milling process. Moreover, the strong interaction force between Fe3O4/PBN and cationic dyes promotes rapid initial adsorption due to their negatively charged surface. Magnetic measurements demonstrated that Fe3O4/PBN is superparamagnetic. The composites with low loadings of Fe3O4 nanoparticles could be quickly separated from the aqueous solution under a low applied magnetic field, improving their recyclability. This work highlights the role of ball milling in improving the adsorption performance of Fe3O4/PBN and greatly promotes the practical application of Fe3O4/PBN in the field of environmental purification.

Zeolite/slag-based porous geopolymer sphere regenerable composites with enhanced mechanical strength and good dye removal performance

Porous slag-based geopolymer spheres were synthesized by a suspension-solidification method using silicone oil as suspending bath. Zeolite powder, expected to improve or optimize the mechanical and/or adsorption properties, was used as second phase. The porous morphology, structure change, specific surface area, porosity, mechanical properties as well as adsorption capacity of the porous solid waste-based sphere composites were investigated. The mechanical strength was significantly improved by the addition of zeolite, along with a slight decrease for methylene blue adsorption properties. The obtained porous slag-based zeolite/geopolymer spheres with high porosity and acceptable strength have potential application as low cost and high effective adsorption composite materials.

The Effect of Silver Nanoparticles/Titanium Dioxide in Poly(acrylic acid-co-acrylamide)-Modified, Deproteinized, Natural Rubber Composites on Dye Removal.

This work aims to enhance the dye-removal performance of prepared poly(acrylic acid-co-acrylamide)-modified, deproteinized, natural rubber ((PAA-co-PAM)-DPNR) through incorporation with silver nanoparticles/titanium dioxide. The (PAA-co-PAM)-DPNR was prepared by emulsion-graft copolymerization with a grafting efficiency of 10.20 ± 2.33 to 54.26 ± 1.55%. The composites based on (PAA-co-PAM)-DPNR comprising silver nanoparticles and titanium dioxide ((PAA-co-PAM)-DPNR/Ag-TiO2) were then prepared by latex compounding using the fixed concentration of AgNO3 (0.5 phr) and varying concentrations of TiO2 at 1.0, 2.5, and 5.0 phr. The formation of silver nanoparticles was obtained by heat and applied pressure. The composites had a porous morphology as they allowed water to diffuse in their structure, allowing the high specific area to interact with dye molecules. The incorporation of silver nanoparticles/titanium dioxide improved the compressive modulus from 1.015 ± 0.062 to 2.283 ± 0.043 KPa. The (PAA-co-PAM)-DPNR/Ag-TiO2 composite with 5.0 phr of TiO2 had a maximum adsorption capacity of 206.42 mg/g, which increased by 2.02-fold compared to (PAA-co-PAM)-DPNR. The behavior of dye removal was assessed with the pseudo-second-order kinetic model and Langmuir isotherm adsorption model. These composites can maintain their removal efficiency above 90% for up to five cycles. Thus, these composites could have the potential for dye-removal applications.

Lignin/PVA hydrogel with enhanced structural stability for cationic dye removal

In this study, a lignin-based hydrogel for wastewater treatment was prepared by incorporating kraft lignin (KL) into a poly (vinyl alcohol) (PVA) matrix. The underwater structural stability of the KL-PVA hydrogel was guaranteed through physicochemical crosslinking, involving freeze–thaw process and chemical crosslinking reaction. The KL-PVA hydrogel displayed superior compressive characteristics compared to the original PVA hydrogel. This improvement was attributed to the chemical crosslinking and the reinforcing effect of the incorporated KL microparticles. The incorporation of anionic KL microparticles into the PVA three-dimensional network structure enhanced the cationic methylene blue (MB) and crystal violet (CV) adsorption efficiency of the prepared KL-PVA hydrogel. The MB adsorption results were well explained by pseudo-2nd order kinetics model and Langmuir isotherm model. Electrostatic forces, hydrogen bonding and π-π stacking interactions were the main adsorption mechanisms between cationic dyes and KL surfaces, indicating the potential of KL-PVA hydrogel as an effective adsorption material. Moreover, regulating the molecular weight of PVA not only prevented lignin leakage from the KL-PVA hydrogel but also elevated the KL content within the hydrogel, consequently improving its dye removal performance. For KL-PVA hydrogel with high molecular weight PVA, the MB and CV adsorption capacities were 193.8 mg/g and 190.0 mg/g, respectively.

Lanthanum-substituted Cobalt Ferrite Established by the Co-precipitation Process: Annealing Temperature Adjustment of Structural, Magnetic, and Dye Removal Characteristics

Co-precipitation process was used for the synthesis of lanthanum-substituted cobalt ferrite nanoparticles at several annealing temperatures (Ta), i.e., 200 °C, 300 °C, and 400 °C, for 5 h. XRD spectral depicted that the produced nanoparticles sample indicates a single phase of fcc inverse spinel conforming to ICDD No 22-1086. The crystallite size (D) calculation at the strongest peaks shows the increase in enhancing the Ta i.e., 18.99 nm, 19.90 nm, and 23.21 nm for 200 °C, 300 °C, and 400 °C, respectively. The FTIR results showed absorption band at the tetrahedral site, v1 ~575 cm−1 and the octahedral site, v2 ~474 cm−1. The absorption bands indicate that the lanthanum ions have successfully replaced the Fe3+ cations in the original cobalt ferrite structure. According to the hysteresis loop, the coercive field's (HC) magnitude falls from 700 Oe down to 550 Oe as Ta increases. This result is consistent with the anisotropy constant which decreased from 0.77×104 erg/cm3 to 0.56×104 erg/cm3. The obtained nanoparticles also showed superior performance (much larger than 95%) for dye removal of Congo red. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).