Reactive Red Research Articles

Enhancement of the anaerobic biodegradation efficiency of azo dye by anthraquinone-loaded biochar biofilm: factors affecting biofilm formation and the enhancement mechanism

Carbon-based materials that serve as microbial carriers, and the role of surface-formed biofilms in anaerobic digestion, merit further investigation. This study explored the role and mechanism behind the biodegradation enhancement of biofilms formed onto anthraquinone-loaded biochar (AQS-BC) surfaces through the anaerobic decolorization process of azo dye Reactive Red 2, and optimized the conditions for AQS-BC biofilm formation. The results indicated that the AQS-BC biofilm system exhibited high treatment efficiency and stability in RR2 anaerobic decolorization. RR2 led to the accumulation of volatile fatty acids (VFAs) and inhibition of methane production, while the presence of AQS increased methane production. The effects of sludge concentration, contact time, carbon source concentration, and RR2 concentration on biofilm maturity were also analyzed. Combining biochemical characteristics, electrochemical properties, surface structure, and microbial community analysis, a mechanism for the anaerobic decolorization of RR2 via AQS-BC as a microbial carrier was proposed. This study provides insights into the roles of biofilms in the anaerobic wastewater treatment processes.Graphical

Modification of polysulfone membranes using magnetite nanoparticles containing sulfonic acid and heteropoly acid groups to improve permeability and antifouling properties

To increase the performance of ultrafiltration membranes, it is necessary to develop new materials. In this study, membrane production was carried out using magnetite nanoparticles functionalized by sulfonic acid and phosphotungstic acid (HPW) to increase permeability and improve antifouling properties. Firstly, Fe3O4@SiO2@NH2-SO3H (FSNS) and Fe3O4@SiO2@NH2-SO3H-HPW (FSNSPW) materials were synthesized. Then, different amounts of the nanoparticles were added to the membrane solutions. While the pure water flux was 164.2 LMH in the bare membranes, it was observed as 202.8 LMH and 195 LMH as a result of adding 0.5 % FSNSPW and FSNS. While Pb removal efficiency was 90 % in the bare membrane, it was measured as 97 % for 0.1 % FSNSPW and 89.6 % for 0.5 % FSNS. Maximum flux recovery ratio is 65.3 % for 0.5 % FSNSPW and 63.4 % for 1 % FSNS. Additionally, the highest Reactive Red 120 dye permeation flux was 72.2 LMH for 0.1 % FSNSPW and 71.9 LMH for 0.1 % FSNS membrane. Additionally, the highest permeation flux of Reactive Black 5 dye solution is 83.3 LMH for 0.5 % FSNSPW and 95 LMH for 0.5 % FSNS membrane. It could be concluded that the presence of the HPW group can improve the performance of the membranes.

Biodecolorization of Azo Dye by Bacteria Alcaligenes faecalis Sub Sp. Phenolicus Isolated from a Bark-Beetle Tunnel Developed in Peltophorum Pterocarpum Plant

This study assessed the decolorization of reactive red 120 (RR120) by Alcaligenes faecalis subsp. phenolicus strain isolated from the bark borer insect (Indarbela tetraonis) tunnel developed in Peltophorum pterocarpum. The optimal parameters for the dye of decolorization 0.1 mg/L of dye were pH 7, temperature 35°C, fructose (0.4% w/v) as the carbon supply (0.4% w/v), peptone (0.2% w/v) as the nitrogen source (0.4% w/v), 12 hours of static conditions, and 0.3 ml of inoculums. Cell suspension, sodium alginate (3%, w/v), and PVA (5%, w/v) immobilized cell beads (10 beads 0.5 mm in size) were used in the batch continuous reactor for complete bio-decolorization of RR120. The batch reactor was subjected to 5 cycles of batches for 3 days of constant use. Under optimal conditions, the batch mode achieved more than 99% dye decolorization and fabric color removal in less than 48 hours of contact. When the control and dye-decolorized media were analyzed using UV spectroscopy, the absorbance of the control medium was higher than that of the decolorized media. GC-MS and FTIR analysis revealed the basic compounds and functional groups of the parent RR120 dye. This strain decolored 76.51% of AB 113, 96.8% of orange II, 98.47% of congo red, 98.3% of RR120, 97.92% of phenol red individual dyes, and 94.72% of the dye mixture at 12 hours. A. faecalis subsp. Phenolicus strains produced positive results in the qualitative analytical test of exopolysaccharides (EPS) and plant growth-promoting rhizobacteria (PGPR) production. The RR120 was decolorized in the presence of heavy metal ions by A. faecalis sub-sp. Phenolicus bacteria.

Performance assessment and characterization of the biosorption of the azo dye reactive Red 2 on thermally inactivated biomass of Trichoderma reesei

The present study evaluated and characterized the performance in the biosorption of the dye azo Reactive Red 2 (RR2) on thermally sterilized biomass of the fungus Trichoderma reesei. An FTIR analysis of unloaded and loaded biomass with RR2 confirmed the interactions between dye molecules and functional groups on the fungal biomass surface. The decrease in the initial pH of 9 to 3 with an increase in the temperature of 20 to 40 °C improved the biosorption, reaching for RR2 a higher removal efficiency of 76.88% at pH 3 and 40 °C. A pseudo-second-order model explained the biosorption kinetics of RR2 (R2≥0.9869), and the intraparticle diffusion model showed that the biosorption process was initially controlled by diffusion rate and later by biomass surface saturation with the dye molecules. The Langmuir isotherm explained the biosorption equilibrium well (R2 ≥ 0.9241), achieving the maximum biomass biosorption capacity (qmax ) value at 61.72 mg g−1. The dimensionless separation factor values (0.0632 ≤ RL ≤ 0.0973) and the thermodynamic evaluation of the process (ΔG° ≤ −24.09 kJ mol−1, ΔH° ≥ 12.39 kJ mol−1, ΔS° ≥ 0.1265 kJ mol−1 K−1) demonstrate that the biosorption was favorable, reversible, spontaneous, and endothermic. The findings in the present study allow it to consider the biomass of Trichoderma reesei thermally sterilized as a biosorbent biomaterial that can be used for bioprocess design in removing the azo reactive dyes from textile wastewater.

Compost as Green Adsorbent for the Azo Dyes: Structural Characterization and Dye Removal Mechanism

The study aimed to determine the feasibility of using compost as a ‘green adsorbent’ for the removal of five anionic azo dyes belonging to the monoazo, disazo and trisazo classes: Direct Red 81 (DR-81), Direct Blue 74 (DB-74), Reactive Blue 81 (RB-81), Reactive Red 198 (RR-198) and Acid Black 194 (ABk-194) from aqueous solutions. The adsorption capacity of the compost was determined using a batch method with initial dye concentrations ranging from 1 to 1000 mg/L. The kinetics of dye removal followed a pseudo-second-order model, indicating chemisorption as the rate-limiting step. The monoazo dyes RB-81, RR-198 and ABk-194 with the smaller molecule size were adsorbed the fastest. The Langmuir and Sips models best fit the adsorption system with maximum adsorption capacities in the range of 12.64 mg/g (RR-198)—20.92 mg/g (ABk-194) and 12.57 mg/g (RR-198)—25.43 mg/g (ABk-194), respectively. The adsorption depended on the dye structure, especially on the ratio of the numbers of proton donors to proton acceptor locations in functional groups. The differences in the adsorption mechanism could be explained by thermodynamic properties such as dipole moments, HOMO–LUMO energy gap, polarizability, electron affinity, ionization potential, electronegativity and chemical hardness obtained by Density Functional Theory.Graphical

Green synthesis of Fe[sbnd]Ni[sbnd]Sn trimetallic oxides from Moringa oleifera for photocatalytic degradation of Reactive Red 6B dye

The nanocomposite FeNiSn trimetallic oxides were synthesized using an aqueous Moringa Oleifera leaf extract. The prepared nanocomposite was analyzed using SEM, FTIR, XRD, N2 adsorption-desorption, Zeta potential, and UV–vis analysis. A common Azo dye named Reactive Red 6B (RR-6B), widely applied in the dyeing industry and causing environmental pollution, was selected to examine the photodegradation of FeNiSn trimetallic oxides nanocomposite under sunlight irradiation, and it was shown that this dye could be successfully degraded by prepared nanocomposite. Effects of parameters such as inorganic salt concentration, H2O2 concentration, contact time, pH, and impact of different concentrations of catalyst and dye were examined to find out degradation conditions. This prepared nanocomposite was applied for the photodegradation of RR-6B dye, and 95 % degradation efficiency was obtained at pH 4, 10 mg of catalyst concentration, 10 ppm of dye concentration, and contact time of 2 h. Degradation kinetics were carried out using Langmuir-Hinshelwood and first-order reaction models. These results showed a facile technique for forming nanocomposite to efficiently degrade organic contaminants from wastewater, which directly impacts industrial wastewater treatment. The antibacterial activity was performed using the Time assay kill method for Gram-positive S. aureus and Gram-negative E. coli bacteria. The results of antibacterial activity showed an inhibition effect on bacterial growth by trimetallic oxides NPs, suggesting their potential use in antimicrobial coatings and materials. These findings underscore the practical applications of our research, demonstrating its relevance and potential impact in real-world scenarios.

Efficient adsorption removal of anionic dyes by waste PET-derived MIL-101(Cr)

Adsorption can be used as a pollutant removal method to solve the increasingly serious problem of synthetic dye pollution and metal organic framework (MOF) is considered as a novel adsorbent for its unique structure. However, the high cost and high toxicity during the synthesis procedure of MOFs like MIL-101(Cr) limited their potential on the large-scale production and application. In this paper, waste PET plastic was depolymerized to prepare terephthalic acid (TPA) as an organic linker to synthesize MIL-101(Cr). Besides, Hydrofluoric acid (HF) was not added during the synthesis to avoid poisonous pollution. MIL-101(Cr) was applied to the adsorption of anionic dyes reactive red 2 (RR2) and reactive blue 19 (RB19). The batch experiments exhibited kinetic data best fitted the pseudo-first-order model (PFO) with the adsorption capacity of 662.87 (RR2) and 863.67 mg g-1 (RB19). The isotherm adsorption data fitted well with the Freundlich isotherm, indicating formation of multilayer coverage over the surface of MIL-101(Cr). The highest regeneration rate of MIL-101(Cr) at the fourth cycle was 91.18 and 91.44 % after RR2 and RB19 adsorption. X-ray photoelectron spectroscopy (XPS) technique and Fourier Transform Infrared (FTIR) spectroscopy both indicated the possible adsorption mechanism of MIL-101(Cr) toward RR2 and RB19 could be attributed to electrostatic interactions, hydrogen bonding, and the π-π stacking. This work proposed a novel method using waste plastics as raw materials to synthesize eco-friendly pollutant adsorbent, which had an enlightening effect on pollutant treatment.

Empowering TiO2–coated PVDF membranes stability with polyaniline and polydopamine for synergistic separation and photocatalytic enhancement in dye wastewater purification

Photocatalytic membranes are effective in removing organic dyes, but their low UV resistance poses a challenge. To address this, self-protected photocatalytic PVDF membranes were developed using polyaniline (PANI) and polydopamine (PDA), whaich are anti-oxidation polymers, as interlayers between the membrane and TiO2. PVDF membranes were first modified by a self-polymerization layer of either PANI or PDA and then coated with titanium dioxide (TiO2). The TiO2 remained firmly attached to the PANI and PDA layer, regardless of sonication and prolonged usage. The PANI and PDA layers enhanced the durability of PVDF membrane under UV/TiO2 activation. After 72 h of irradiation, PVDF–PDA–TiO2 and PVDF–PANI–TiO2 membranes exhibited no significant change. This process improved both separation and photocatalytic activity in dye wastewater treatment. The PVDF–PDA–TiO2 and PVDF–PANI–TiO2 membranes showed enhanced membrane hydrophilicity, aiding in the rejection of organic pollutants and reducing fouling. The modified membranes exhibited a significant improvement in the flux recovery rate, attributed to the synergistic effects of high hydrophilicity and photocatalytic activity. Specially, the flux recovery rate increased from 17.7% (original PVDF) to 56.3% and 37.1% for the PVDF–PDA–TiO2 membrane and PVDF–PANI–TiO2 membrane. In dye rejection tests, the PVDF‒PDA‒TiO2 membrane achieved 88% efficiency, while the PVDF‒PANI‒TiO2 reached 95.7%. Additionally, the photodegradation of Reactive Red 239 (RR239) by these membranes further improved dye removal. Despite an 11% reduction in flux, the PVDF–PDA–TiO2 membrane demonstrated greater durability and longevity. The assistance of PANI and PDA in TiO2 coating also improved COD removal (from 33 to 58–68%) and provided self-protection for photocatalytic membranes, indicating that these photocatalytic membranes can contribute to more sustainable wastewater treatment processes.

Effect of spunbond nonwoven microplastics on dye wastewater treatment via hydrogen peroxide–based catalyst–assisted advanced oxidation processes

The increasing prevalence of microplastics (MPs) in textile wastewater poses significant challenges for treatment processes. This study evaluates the impact of MPs on the decolorization of Reactive Red 239 (RR239) dye using hydrogen peroxide–based advanced oxidation processes, specifically UV/H2O2, H2O2/Fe2+ (Fenton) and H2O2/Fe2+/UV (photo–Fenton). UV/H2O2 oxidation exhibited superior decolorization efficiency compared to both Fenton and photo–Fenton processes. The optimal decolorization efficiency for RR239 was achieved at 94.1% at pH 3 in the Fenton process with H2O2 and Fe2+ concentrations of 2.5 mg/L and 12.5 mg/L, respectively. For UV/H2O2 oxidation, complete decolorization was achieved in 60 min at an optimal UV light intensity of 11 W and H2O2 of 75 mg/L at neutral pH. The presence of spunbond nonwoven MPs in RR239 wastewater significantly inhibited decolorization efficiency and kinetic rate constants. The pseudo–second–order rate constant (Kapp) for the Fenton process without MPs was 0.0101 M–1 min–1, whereas the presence of MPs reduced the Kapp to a range of 0.0026 to 0.0034 M–1 min–1. The UV/H2O2 process maintained a Kapp of 0.1301 min–1 as pseudo–first–order regardless of MP content but was affected by MP size. MPs in the size range of 200–500 µm improved decolorization efficiency, while larger MPs (500–1000 µm) reduced it. The results highlight the necessity of separating MPs to maintain high decolorization efficiency in dye wastewater treatment processes. The findings suggest that optimizing these parameters can enhance the efficacy of advanced oxidation processes in treating dye wastewater containing MPs.

Heterogeneous Fenton process using GO@Fe3O4/Cu catalyst for the degradation of reactive dyes from aqueous solutions: modeling and optimisation

ABSTRACT Various industries such as textile, paper, rubber, plastic, and cosmetics use dyes to produce their products. Some dyes used in textile industries are teratogenic, carcinogenic, mutagenic, and dangerous for humans and other organisms. This study aimed to determine the amount of removal of reactive dyes from aqueous solutions during the heterogeneous Fenton process. In this study, iron oxide nanoparticles and copper nanoparticles were loaded on graphene oxide (GO). GO@Fe3O4/Cu catalyst was synthesised and applied to remove reactive dyes from aqueous solutions in a heterogeneous Fenton process. Contact time, pH, catalyst dose, dye concentration, and H2O2 dose were considered effective parameters. Experiments were designed according to the Box-Behnken design in the Design Expert software. Catalyst properties were determined using SEM, VSM, XRD, and FTIR analysis. The ANOVA showed that the selected statistical model with R2 0.965, p < 0.0001, and F-value 27.79 was significant. In the optimal conditions of pH 3, H2O2 dose 0.48 mL, catalyst dose 0.34 g/L, dye concentration 22 mg/L, and contact time 9 min, the degradation efficiency of Reactive Blue 21 (RB21), Reactive Red 195 (RR195) and Reactive Red 19 (RR19) were 92, 97, and 80%, respectively. The results showed that after 5 cycles of recycling, the catalyst had a high efficiency in pollutant removal and could be utilised many times for dye decomposition. GO@Fe3O4/Cu catalyst was successfully synthesised using a simple method. The heterogeneous Fenton process with a magnetic catalyst in the presence of H2O2 has a high potential to remove reactive dyes from the aqueous solution.

Mechanochemical Synthesis of Cross-Linked Chitosan and Its Application as Adsorbent for Removal of Per- and Polyfluoroalkyl Substances from Simulated Electroplating Wastewater.

Chitosan is a promising adsorbent for removing a wide range of pollutants from wastewater. However, its practical application is hindered by instability in acidic environments, which significantly impairs its adsorption capacity and limits its utilization in water purification. While cross-linking can enhance the acid stability of chitosan, current solvent-based methods are often costly and environmentally unfriendly. In this study, a solvent-free mechanochemical process was developed using high-energy ball milling to cross-link chitosan with various polyanionic linkers, including dextran sulfate (DS), poly[4-styrenesulfonic acid-co-maleic acid] (PSSM), and tripolyphosphate (TPP). The mechanochemically cross-linked (MCCL) chitosan products exhibited superior adsorption capacity and stability in acidic solutions compared to pristine chitosan. Chitosan cross-linked with DS (Cht-DS) showed the highest Reactive Red 2 (RR2) adsorption capacity, reaching 1559 mg·g-1 at pH 3, followed by Cht-PSSM (1352 mg·g-1) and Cht-TPP (1074 mg·g-1). The stability of MCCL chitosan was visually confirmed by the negligible mass loss of Cht-DS and Cht-PSSM tablets in pH 3 solution, unlike the complete dissolution of the pristine chitosan tablet. The MCCL significantly increased the microhardness of chitosan, with the order Cht-DS > Cht-PSSM > Cht-TPP, consistent with the RR2 adsorption capacity. When tested on simulated rinsing wastewater from chromium electroplating, Cht-DS effectively removed Cr(VI) (98.75% removal) and three per- and polyfluoroalkyl substances (87.40-95.87% removal), following pseudo-second-order adsorption kinetics. This study demonstrates the potential of the cost-effective and scalable MCCL approach to produce chitosan-based adsorbents with enhanced stability, mechanical strength, and adsorption performance for treating highly acidic industrial wastewater containing a mixture of toxic pollutants.

Decolourization and detoxification of Reactive Red-195 azo dye by Staphylococcus caprae isolated from textile effluent.

Azo dyes are used as coloring agent in textile industries at larger scale. As a result, large quantity of dye-enriched waste water is generated which subsequently poses environmental problems. Biological tool involving bacteria having azoreductase enzyme has proved to be more effective and efficient in dye effluent treatment. Current work focuses on Staphylococcus caprae (S. caprae) for degradation and decolorization of Reactive Red-195 (RR-195) azo dye. For this purpose, factors such as pH, temperature, inoculums, carbon and nitrogen sources, and dye concentrations have been optimized for maximum decolorization and degradation. S. caprae (4mg/mL) efficiently resulted into 90% decolorization of RR-195 dye under static condition at 100µg/mL concentration, 30°C and pH 7.0 at a 12-h contact period. FTIR analysis has revealed the formation of new functional groups in the treated dye such as O-H stretch at 3370cm-1, C-H band stretching at 2928cm-1, and new band at 1608cm-1 which specify the degradation of aromatic ring, 1382 and 1118cm-1 represents desulfonated peaks. Biodegraded metabolites of RR-195 dye such as phenol, 3, 5-di-tert-butylphenol, and phthalic acid have been identified respectively that find industrial applications. Phytotoxicity test has shown non-toxic effects of treated dye on germination of Vigna radiata and Triticum aestivum seeds. Further, antibiotic diffusion assay has confirmed the biosafety of S. caprae.

Biosynthesis of copper nanoparticles using Bacillus flexus and estimation of their potential for decolorization of azo dyes and textile wastewater treatment

In many underdeveloped countries, textile industries discharge their effluents without any treatment. The untreated textile wastewater consists of both azo dyes and heavy metals which not only change the physicochemical and biological properties of soil and water but also affect human health. In recent years, copper-based nanomaterials have attained worldwide attention because of their unique properties and potential for decolorization of azo dyes and wastewater treatment. The present study demonstrates the bacterial synthesis of copper nanoparticles (Cu-NPs) using Bacillus flexus strain isolated from a textile wastewater followed by their application for photocatalytic degradation of various azo dyes and treatment of actual wastewater. The FT-IR analysis confirmed the presence of various functional groups including proteins on Cu-NPs which improved their stability. The scanning electron microscopy (SEM) images revealed the spherical shape of Cu-NPs with a size of range between 17–34 nm. Similarly, the XRD analysis of biosynthesized Cu-NPs showed various diffraction peaks at 44.5°, 51.5°, 74.75 which confirmed the crystalline nature of nanoparticles. While studying the photocatalytic decolorization of azo dyes by Cu-NPs, it was observed that 88.164 ± 0.19 %, 88.452 ± 1.89 %, 90.433 ± 1.81 %, 64.770 ± 1.02 %, 46.774 ± 1.61 %, and 67.274 ± 2.89 % of reactive black-5, congo red, malachite green, methylene blue, reactive red-2 and blue direct, respectively, were decolorized after 4 h of solar irradiation at 50 ppm concentration. Additionally, the biosynthesized nanoparticles also resulted in reduction of various parameters like EC, pH, TDS, COD, color intensity, sulphates, and phosphates in the textiles wastewater. The reduction of COD, sulfates, and phosphates was about 39.659 %, 43.157 %, and 49.493 %. The results of current work suggest that biosynthesized copper nanoparticles might serve as a potential green solution for the decolorization of various dyes including wastewater treatment.

Understanding the adsorption of Reactive red 2 onto metal hydroxide sludge: analysis with physico-statistical steric and energetic perspectives.

This theoretical investigation delves into the analysis of Reactive red 2 (RR-2) adsorption isotherms on metal hydroxide employing a sophisticated double-layer model characterized by dual-energy levels within the realm of physical adsorption phenomena. An examination of five distinct statistical physics frameworks was undertaken to elucidate the modeling and interpretation of equilibrium data. Expression for the physico-chemical parameters involved in the adsorption phenomena was derived based on statistical physics treatment. Fitting experimental adsorption isotherms (308-333K) to a DAMTBS has revealed the number of anchored molecules per site, occupied receptor site density, and the number of adsorbed layers. The steric parameter n varies between 0.92 and 1.05. More importantly, it is evidenced that the adhesion mechanism of (RR-2) onto metal hydroxide as determined by the estimated adsorption energies (< 40kJ/mol) supports a spontaneous and exothermic physisorption process. Thermodynamic potential functions such as entropy, Gibbs free energy, and internal energy have been computed based on the most suitable model. This research advances our physical understanding of how metal hydroxide captures dye molecules RR-2 through adsorption reaction for water depollution treatment.

Highly efficient removal of contaminant from typical dye wastewater by using individual AOPs-A/O processes: Design, performance, and mechanism

The individual process design suitable for different types of dye wastewater is less reported, and the performance and mechanism of advanced oxidation processes (AOPs)–anaerobic/aerobic (AOPs-A/O) is also unclear. In this experiment, different processes were designed to treat three typical dyes, namely, Disperse Blue (DB), Indigo Blue (IB), and Reactive Red (RR). Their performance and mechanism were studied. Results showed that sodium persulphate oxidation (SPO)/Fenton oxidation (FO) coupling treatment was the optimal treatment process for DB and IB wastewater, and SPO/ozone oxidation (OO) coupling treatment was the optimal treatment process for RR wastewater. After individual AOPs-A/O, the total chemical oxygen demand (COD) removal efficiency (CODre) of DB, IB, and RR were 96.25%, 96.35%, and 96.73%, respectively, and the overall mineralisation efficiency (ME) was 67.04%, 85.97%, and 72.24%, respectively. The contribution efficiency of the three treatment units to wastewater decreased as follows: AOPs > anoxic > aerobic. The initial B/C (B/C is the ratio of BOD to COD, which can indicate the biodegradability of wastewater) of DB, IB, and RR was 0.064, 0.065, and 0.262, respectively. The effluent B/C of DB, IB, and RR increased to 0.292, 0.392, and 0.795, respectively. Sequencing results showed that at the phylum level, its dominant group changed from Proteobacteria to Firmicutes. At the class level, its dominant group changed from Gammaproteobacteria to Clostridia.

Cleaner reactive dyeing with the recycled dyeing wastewater

In order to recycle water and inorganic salts, sodium persulphate (SPS) was used to degrade the C.I. Reactive Red 195 (RR195) dyeing wastewater. The thermodynamic and kinetic relationships of RR195 dyeing in cleaner and conventional dyeing processes were analyzed and compared. The feasibility of the one-bath cyclic dyeing in the recycled dyeing wastewater was confirmed through the properties of dye utilization, color parameters and energy conservation. The appropriate conditions were 0.3 g/L of SPS and treatment at 95 °C for 30 min, which resulted in a decolorization rate of 99.7% for the dyeing wastewater, mainly due to the action of radical sulfate. When cotton fabric was dyed with the cleaner dyeing, the kinetic was pseudo-second-order and the thermodynamic was Freundlich adsorption. There was a 47.5% reduction in half dyeing time, a greater diffusion coefficient and standard affinity, and lower entropy and enthalpy values when dyeing in reused wastewater. Cotton fabrics were dyed with the proposed cleaner dyeing process, which reduced the amount of water and inorganic salt by 95.8% and 89.8%, respectively. The total organic carbon (TOC), biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) were 53.6%, 69.8% and 42.6% lower than the conventional dyeing process, respectively. The recommended technology not only reduces the amount of dyeing wastewater but also enables the recycling of inorganic salts and water, which makes great progress in the textile industry.

Green polycaprolactone/sulfonated kraft lignin phase inversion membrane for dye/salt separation

Exploring environmentally friendly, renewable, and cost-effective raw materials is essential in sustainable membrane fabrication. This study presents a facile and scalable method for fabricating a green and biodegradable tight ultrafiltration membrane for dye/salt separation. This involves simply blending biodegradable polycaprolactone (PCL) with the low-cost biobased sulfonated kraft lignin (SKL) additive. Additionally, we employed acetic acid as a green alternative solvent to enhance the sustainability of the membrane fabrication process. The incorporation of hydrophilic SKL into the PCL matrix resulted in increased hydrophilicity (water contact angle changed from 72° to 56°), surface roughness (increased from 29 nm to 43.5 nm), and enhanced negative electrostatic charge of the membrane (−40 mV to −45 mV). The optimized PCL/SKL membrane (M3) exhibited excellent water flux (∼45 LMH) under 40 psi hydraulic pressure coupled with ∼98 % and ∼10 % rejection rates for reactive red (RR) dye and NaCl, respectively. Moreover, the M3 membrane maintained its exceptional dye/salt fractionation performance while separating the mixtures at low salt concentrations. However, with increasing salt concentration (1–50 g/L), the membrane's RR dye rejection declined from ∼90 % to ∼50 %, with a significant reduction in NaCl and Na2SO4 salts rejection (from ∼14 % to ∼1 % and ∼22 % to –∼1 %, respectively). The M3 membrane exhibited remarkable antifouling properties during dye and humic acid filtration with a high flux recovery ratio (>98 %) and low flux decline rate (<7 %). The PCL/SKL membrane also showed excellent stability and maintained consistent separation performance over a long period. Overall, the novel biodegradable PCL/SKL membrane prepared in this study presents a promising avenue toward sustainable membrane fabrication for wastewater treatment applications.

Manufacturing of isocyanate-based oligomeric dyes with high coloring capabilities: synthesis and application in the dyeing of organic chrome-free leather

Leather dyeing is a critical step in leather manufacturing, as it is responsible for providing leather products with an eye-catching visual aspect and adequate quality properties to meet customers' expectations. This step is becoming more and more challenging as the leather industry advances hand in hand with new environmentally friendly policies and regulations to achieve a safer and healthier planet by replacing the highly polluting Cr-based leather tanning technology with greener alternatives. As a result, achieving high-performance dyeing of organic chrome-free leather is one of the bottlenecks for the sustainable development of the leather industry. Herein, we propose a novel strategy to fabricate an isocyanate-based oligomeric dye (IBD) with high coloring capabilities (component content higher than 62.8%) based on toluene 2,4-diisocyanate and reactive red dye 180. This material has been tested for the dyeing of biomass-derived aldehyde (BDA)-tanned leather with excellent outcomes. The experimental results showed that the crust leather dyed with our novel IBD dyeing agent had higher color fastness and better fullness than the leather dyed with conventional anionic (CAD) or reactive red 180 (RRD-180) dyes. These excellent and promising results open new avenues in manufacturing high-performance organic Cr-free leather products and help to ensure the sustainable transition of the leather industry from Cr-based leather tanning to more sustainable alternatives, maintaining the final quality of the leather products.Graphical abstract

Rosa damascena waste as biosorbent for co-existing pollutants removal: Fixed-bed column study and ANN modeling

The adsorption behavior of Cd(II) and Pb(II) ions in a coexisting environment, alongside with both dyes (Reactive Red198 and Blue29) was systematically investigated by using a continuous fixed-bed column completely packed with Rosa damascena waste biosorbent (RDWB). Artificial neural network (ANN) model was also utilized to predict the performance of RDWB for various inputs. Their column performance was assessed by optimizing parameters such as bed depth, influent flow rate, and biosorbents’ concentration. It was found that an increasing bed depth considerably extended the operational lifespan and decrease in flow rate delays the column adsorption. Its adsorption capacities were 24.9, 24.6, 24.0 and 24.3 mg/g for Pb(II), Cd(II), Red198, and Blue29, respectively. The RDWB also had a higher adsorption capacity, as compared to previously used biosorbents such as chitosan and biochars due to its good thermal stability and high surface area of 421.46 m2/g. The adsorption of target pollutants took place through ion exchange and electrostatic interactions with negatively charged functional groups on the adsorbent’s surface. The experimental data were fitted by various column adsorption models such as the Thomas, Yoon-Nelson, and Adams-Bohart. The findings showed that the Thomas model exhibited a strong correlation with the experimental data. In contrast, the Adams-Bohart model was applicable to the initial phase of the breakthrough curve (Ce/C0 ≤ 0.1). For industrial applications, a scale up model was also presented with the cost analysis of the biosorbent. The comparison of predicted values with experimental percentage (%) removal values of target pollutants by the RDWB indicated the excellent performance of the ANN model for this work.

Electro‐Conductive Ti3C2 MXene Multilayered Membranes: Dye Removal and Antifouling Performance

AbstractThis work describes the fabrication of a novel electroconductive membrane made of Ti3C2Tx (MXene) nanosheet coating through a one‐step pressure‐assisted technique. Ti3C2‐MXene is firmly attached over a polyamide–imide (PAI) microfilter by employing a binder composed of carboxymethyl cellulose (CMC)/glutaraldehyde (GA). Through coating a proper amount of multilayer Ti3C2‐MXene, the electrical conductivity of 174 ± 0.16 S m−1 is achieved. The rejection rates of reactive red 120 (RR120), reactive black (RB), and methyl orange (MO) by the pristine PAI membrane are 45.2%, 40.81%, and 33.65%, respectively. However, rejection rates significantly improve with the Ti3C2 MXene coating to over 99.71%, 97.95%, and 68.91% for RR120, RB, and MO. Applying a 4 V cathodic potential resulted in a flux recovery ratio (FRR) of 99.83% and a flux decline rate (FDR) of less than 1% during humic acid (HA) filtration. Without applying voltage, the MXene‐coated membrane shows an FRR and FDR of 92.51% and 45.56%, respectively. Surface energy analysis reveals strong repulsive interactions between foulants and the membrane surface. Moreover, the surface free energy indicates that foulants such as sodium alginate (SA) and bovine serum albumin (BSA) exhibit stronger adhesion to the membrane than HA, consistent with the fouling experiment results.