Dye System Research Articles

The roles of elevated temperature and carriers in the dyeing of polyester fibres using disperse dyes: Part 1 fundamental aspects

AbstractThis review concerns the application of disperse dyes to poly(ethylene terephthalate) (PET) fibres using aqueous immersion dyeing processes and the roles of both elevated dyeing temperatures and carriers in such dyeing systems. This part of the paper presents a review of the fundamental properties and characteristics of PET fibres, disperse dyes and dyeing accelerants. In the next part of the paper, the various theories and concepts that have been proposed to explain the promotional effects imparted by elevated dyeing temperatures and carriers to disperse dye uptake on PET and other types of fibre, are reviewed and analysed, from the viewpoints of the essential physico‐chemical aspects of both the aqueous disperse dye/PET and disperse dye/carrier/PET systems. Later parts of the paper will present a mechanistic model of the disperse dye adsorption process based on dye solubility as well as a novel plasticisation model of dye diffusion.

The roles of elevated temperature and carriers in the dyeing of polyester fibres using disperse dyes: Part 2. Analysis of conventional models of dye adsorption

AbstractThis review concerns the application of disperse dyes to poly(ethylene terephthalate) fibres using aqueous immersion dyeing processes and the roles of both elevated dyeing temperatures and carriers in the dyeing system. The precise reasons why very high temperatures in the region of 130°C promote the uptake of disperse dyes on poly(ethylene terephthalate) fibres from aqueous dyebaths have not been satisfactorily resolved, nor has the exact mechanism by which carriers promote dye uptake at lower temperatures in the region of 98°C been adequately established. In this part of the review series, a detailed review and analysis is presented of the various concepts and theories that have been proposed to account for the promotional effects of temperature and carriers on disperse dye uptake, from the viewpoint of both the thermodynamic and kinetic aspects of the adsorption of the dyes on poly(ethylene terephthalate) and other types of fibre.

Level dyeing property and aggregation morphology of reactive black 5 on cotton fabric in a salt-free and less-water dyeing system

In a traditional water-based dyeing system, large amounts of salts and water are consumed. However, a non-aqueous media dyeing system achieves salt-free and less-water dyeing. In a non-aqueous media dyeing system, a small amount of water is used, which may affect the aggregation morphology of the dyes. The molecular dynamics of reactive dyes on the surface of cotton fibers were investigated. The results showed that the color depth of dyed cotton fabric did not change much when the dosage of salt was below 5.2% o.w.f. However, continuing to increase the amount of salt could influence the dyeing level of dyed fabric. The diffusion coefficient of dye was 0.3044 × 10−5 cm−2/s when there was no salt in dyeing system. But it was decreased by 14.03% and 16.62% when the salt concentration was increased from zero to 5.2% and 13% o.w.f., respectively. When the concentration of sodium sulfate was zero, the dye molecules in the solution displayed in the form of unimolecular molecules and dimers. However, reactive dyes mainly existed in the form of trimers and polymers when the concentration of sodium sulfate was above 5.2%. When there was no salt in the less-water dyeing system, the van der Waal energy between fiber and dye was 131.29 kJ/mol, but it was increased to 382.92 kJ/mol when the dosage of sodium sulfate was 5.2%. Therefore, with the increase of sodium sulfate dosage, the color depth of the dyed fabric changed little, but the level of dyeing property became poorer.

Phenomenological‐based model of direct blue 2 adsorption on corncob in a fixed‐bed

AbstractThis work presents a phenomenologically based semi‐physical model (PBSM) for the liquid–solid adsorption process, which has been experimentally validated. Two modes of operation of adsorption of direct blue 2 dye (DB2) on corn cobs in a fixed bed are discussed by applying the PBSM. The first mode of operation is the typical continuous liquid flow, whereas the second is a semicontinuous mode with the recirculation of liquid leaving the column. These modes of operation were used to illustrate different ways in which the system reaches equilibrium conditions. The equilibrium distribution curve (EDC) for low DB2 concentration was reached with the best fit using the Langmuir–Freundlich model (). The local mass transfer coefficient for the solid phase was evaluated by the PBSM deduction, and subsequently, the diffusivity of the surface solid was experimentally evaluated through comparison in terms of the PBSM. Regardless of the mode of operation, surface diffusion is associated with only the nature of the adsorbent material rather than the concentration of the liquid phase. In addition, the PBSM exhibited liquid and solid concentration changes at different points in the column. Moreover, different operating curves of the process were constructed and validated, exhibiting similar results when comparing the predictions of the model and the experimental data. These findings support the strength of the constructed model, enabling its extension to other adsorbent–dye systems.

Plant leaves extract assisted eco-friendly fabrication of ZnO-SnO2@Chitosan for UV-induced enhanced photodegradation of single and ternary mixtures of Rhodamine B

The inadequate handling and uncontrolled discharge of organic dyes into aquatic environments can result in elevated toxicity levels and have adverse effects on both human health and the overall ecosystem. The present work investigated the photodegradation efficiency of the ZnO-SnO2@chitosan nanocomposite (NC) for Rhodamine B (RhB) under ultraviolet (UV) irradiation. The ZnO-SnO2@chitosan nanocomposite (NC) was synthesized via a simple, eco-friendly, and less energy-intensive route, i.e., the co-precipitation method. The synthesized NC was extensively characterized using X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), UV–Vis spectroscopy, Brunauer-Emmett-Teller (BET) analysis, field emission scanning electron microscope (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). The chitosan-modified nanocomposite (NC) exhibits a moderate surface area of 79 m2/g with a low band gap value of 2.72 eV. The photodegradation process depended on operational parameters, such as pH, irradiation time, temperature, dye concentration, and dosage of the photocatalyst. The degradation data of RhB dye was interpreted through a kinetic model, and the data agreed well with the pseudo-first-order kinetics. The rate constant values deciphered from the kinetic model were found to fall in the range of 0.0281–0.0182 min–1 for 25–100 mg/L of dye concentration, suggesting that the synthesized photocatalysts facilitate the dye mineralization process by reducing the activation energy barrier. The interpretation of the reaction intermediates was accomplished with the help of a GC-MS profile to understand the underlying reaction mechanism. The photodegradation potential of the synthesized NC was explored for individual dyes such as RhB, MB and CV and the mixed dye system (RhB+MB+CV). The NC performs better for individual dyes (RhB, CV, and MB), and the degradation performance diminished slightly in the case of mixed dye solution. The reusability study of the synthesized nanocomposites portrayed the successful utility of the recycled NC up to four times without any significant loss in the degradation capacity, thus making the overall degradation process economical and sustainable. The E–factor (a green chemistry metric) study infers that the NC synthesis process imposes no significant threat to the environment and can be safely used in wastewater treatment.

Low temperature non-aqueous dyeing of wool fiber with reactive dyes: A sustainable and eco-friendly method

Conventional wool dyeing usually performed at a boiling point, often destroys the wool structure, consumes plenty energy and water. Aiming at realizing the sustainable cleaning coloration of wool dyeing and keeping the excellent natural quality of wool fiber, a green dyeing technology, non-aqueous dyeing, has been successfully applied. The effect of acid-pretreatment on the reactive dye adsorption behaviors was explored and optimized the dyeing parameters by the design of experiments as well as a single factor screening way. The results demonstrate that acid-pretreatment improved the dye exhaustion rate to 99.79 % effectively by lowering the pH value of wool fiber and increased the dye fixation rate from 75.33 % to 86.93 % by enlarging the dyeing channel. Additionally, the factors that affected wool dyeing were analyzed, approving additional acetic acid had the most significant effect on the wool dyeing. The optimal wool dyeing condition included 1 % on the weight of fiber (o.w.f) acetic acid indicating low-temperature wool dyeing was achieved by this non-aqueous dyeing system at 85 °C for 60min. Furthermore, a higher color depth, constant mechanical properties, good rubbing fastness, and soaping fastness were obtained by this dyeing method. Compared with conventional dyeing, 24.28% energy consumption, 32.50% water usage, and 31.36% wastewater were reduced by this dyeing method. Therefore, sustainable non-aqueous dyeing technology is eco-friendly and has the potential to protect the wool structure from being damaged in the dyeing process.

MoS2 Nanosheets@Metal organic framework nanocomposite for enhanced visible light degradation and reduction of hazardous organic contaminants

Present research focuses on the environmental cleanup of hazardous organic pollutants that are discharged into the natural aquatic bodies which upshots an undesirable shift in the ecological balance. Recently, aromatic nitro compounds and hazardous organic dyes have been recognized as a threat to fauna, flora and human life forms. Therefore, effective and selective eradication of these hazardous pollutants from wastewater systems is a pressing global issue for the academic community. This study aims to design a MoS2 Nanosheets (NS)@Cu-MOF (MS−HK) catalyst via a convenient hydrothermal approach for the elimination of organic and aromatic nitro contaminants from wastewater effluent. Under visible light irradiation, this photocatalyst presented 96.4% removal efficiency for Rose Bengal (RB) dye within a short duration of 30 min, with a first order degradation rate constant of 0.12223 min−1and a catalyst loading of 240 mg/L. Again, the rate constant of the room temperature reduction of 2,4,6−trinitrophenol (TNP) using NaBH4 as a reducing agent, in presence of the prepared nanocatalyst was calculated to be 2.7 × 10−3 s−1. This excellent degradation efficiency could be due to the loading of HKUST-1 with a narrow band gap semiconductor MoS2 leading to enhanced visible light absorption, effective separation and transport of photoinduced h+−e− pairs that limit their recombination. The plausible photodegradation mechanism was supported by photoluminescence and radical trapping experiments. In addition, the impact of various inorganic ions, water matrices, environmental conditions, different dye molecules and mixed dye system was explored on the RB degradation of the synthesized catalyst. Meanwhile, the as-prepared MS−HK nanocomposite displayed significant stability during the photocatalytic experiments, as evident from XRD results, until four successive cycles maintaining an outstanding degradation efficiency of >89%.

Enhancing adsorption capacity of magnetic magnesium-aluminum layered double hydroxide by surface modification with sodium dodecyl sulfate for efficient removal of organic contaminants

A magnetic magnesium-aluminum layered double hydroxide (Mag-MgAl) was prepared, and its surface was modified using surfactant sodium dodecyl sulfate (SDS) and utilized as adsorbents for antibiotic ciprofloxacin (CIP) and dyes ponceau red (PR) and methylene blue (MB). Mag-MgAl/SDS demonstrated twice the adsorption capacity for CIP compared to Mag-MgAl, confirming that the surface modification by SDS aided the adsorption capacity. At pH 3.5, Mag-MgAl removed CIP and PR, attributed to electrostatic effect and hydrogen bonding, whereas it did not interact with MB. Conversely, Mag-MgAl/SDS successfully removed both MB and CIP, suggesting that SDS micelles acted as nanoreactors attracting cationic contaminants. The PR removal efficiency was low, possibly due to electrostatic repulsion. A binary dye system adsorption assessment was performed by mixing MB and PR aqueous solutions with Mag-MgAl and Mag-MgAl/SDS as selective adsorbents. Mag-MgAl removed around 80% of PR and 45% of MB, whereas Mag-MgAl/SDS removed less than 40% of PR and 80% of MB. SDS remains adsorbed on the surface of Mag-MgAl/SDS after the adsorption process of CIP, MB, or PR. The inversion in the affinity for the target molecules suggests that the surface of the composite can be adjusted to modulate the behavior of the adsorbent toward organic contaminants.

Supply Chain Management Process of Textile Industry: A Case Study on Bangladesh

This research examines a descriptive analysis of Bangladesh's textile industry's process of export, import, and logistic system for yarn dyeing. Bangladesh's industrial sector, which includes the textile industry, is vital to the country's economic growth. In addition to meeting a significant portion of Bangladesh's foreign demand for clothes and apparel, the textile industry provides for about 100% of the country's internal demand. The textile industry is a complex supply chain that manufactures garments, complements, raw materials, and other items. As a traditional management tool, SCM enables manufacturers to work toward increasing the quality of their products, lowering the cost of their products and services, and speeding up product delivery and reaction times in a highly competitive market. Based on primary data of an organization which is Union Limited, a well-reputed and big textile base organization as well as secondary data from internet databases, journals, review articles, etc., this study was constructed. reduced stocks, reduced costs, increased productivity, more agility, shorter lead times, higher profitability, and increased customer loyalty are all aspects of the textile industry's successful supply chain management. This study discusses the overall processing of how a textile industry imports yarn, and how they deliver the final product to the consumer. This research paper will give the concept of the overall processing of the textile industry of Bangladesh.

Regenerated cellulose/polyethyleneimine composite aerogel for efficient and selective adsorption of anionic dyes

With the requirement of sustainable development in modern society, it is urgent to develop the environmentally friendly adsorbents for selective filtration and separation of toxic dyes from hazardous wastewater. Herein, a stable, reusable, and highly compressible three-dimensional regenerated cellulose/polyethyleneimine composite aerogel (RC/PCA) was successfully prepared directly using cheap cotton pulp as raw material and N-methyl morpholine-N-oxide (NMMO) as the “green” solvent, in which the regenerated cellulose (RC) with hydroxyl groups converted from cotton can interact with polyethyleneimine (PEI) with amine groups. After further crosslinking of RC, PEI and glutaraldehyde (GA), the RC/PCA can be used to selectively absorb anionic dyes from the ternary mixed dye system, which maximal adsorption capacity for methyl orange (MO) can be up to 980.39 mg/g. Moreover, the obtained stable RC/PCA can be repeatedly used at least 50 times for the removal of MO (20 mg/L) with a high filtration efficiency of 99.8 %. The kinetics and isothermal adsorption data were described via the pseudo-second-order kinetic model and Langmuir model. Therefore, this research proposes a novel strategy for developing low-cost, highly efficient, regenerated cellulose-based adsorbents to extract organic dyes from wastewater for potential practical applications.

Complete recycling of polymers and dyes from polyester/cotton blended textiles via cost-effective and destruction-minimized dissolution, swelling, precipitation, and separation

The lack of economic dye-polymer and fiber-fiber separations for blended textiles prevents large-scale textile recycling. We focus on a clean, cost-effective, and destruction-minimized fiber-to-fiber recycling, suitable for polyester/cotton blended textiles. Here, dyed polyester was dissolved and separated from the blend, followed by controllable polyester precipitation to retain its dyes separately in the solution. The remaining-colored cotton was swollen to remove its dyes after cleavage of dye-cellulose bonds. Colorless polyester and cotton were regenerated into fibers with similar and 60 % higher tenacity than those before the recycling, respectively. Recycled fibers also had desirable dyeability, including dye exhaustion and colorfastness, after being dyed with the dyes extracted from the polyester/cotton blends, via our newly developed solvent dyeing system. More than 99 % of the solvent used in the recycling was recycled. Our recycling had a cost and energy consumption of less than 20 % of the production of virgin materials.

Reverse Micellar Dyeing of Cotton Fabric with Reactive Dye Using Biodegradable Non-Ionic Surfactant as Nanoscale Carrier: An Optimisation Study by One-Factor-at-One-Time Approach.

This study investigates the feasibility of using biodegradable secondary alcohol ethoxylate (SAE) non-ionic surfactant as a building block for the formation of reverse micelles, functioning as reactive dye carriers for the dyeing of cotton fabric in non-aqueous octane medium. Ten dyeing parameters were optimised, by a one-factor-at-a-time approach, namely: (i) effect of colour fixation agent; (ii) surfactant-to-water mole ratio; (iii) surfactant-to-co-surfactant mole ratio; (iv) volume of soda ash; (v) volume of dye; (vi) solvent-to-cotton ratio; (vii) dyeing temperature; (viii) dyeing time; (ix) fixation time; (x) soda-ash-to-cotton ratio. The colour properties, fastness properties and physical properties of SAE-dyed samples were experimentally compared with the conventional water-dyed samples. The optimised condition was found when SAE samples were dyed as follows: (a) 1:20 surfactant-to-water ratio; (b) 1:8 surfactant-to-co-surfactant ratio; (c) 10:1 solvent ratio; (d) 40 min dyeing time; (e) 60 min fixation time; and (f) 70 °C dyeing and fixation temperature. The results showed that SAE-dyed samples have better colour strength, lower reflectance percentage and comparable levelness, fastness and physical properties than that of water-dyed samples. SEM images revealed that the dyed cotton fibres had no severe surface damage caused by an SAE-based reverse micellar dyeing system. The TEM image depicts that the reverse micelle was of nanoscale, spherical-shaped and had a core-shell structure, validating the presence of reverse micelle as a reactive dye carrier and the potential of an SAE-based reverse micellar system for dyeing of cotton fabrics.

Design of self-healable and recyclable multi-network hydrogels for efficient and selective removal of cationic dyes

In this study, a novel multi-network hydrogel with self-healing ability was developed with the aim of addressing the limitations of traditional hydrogels in adsorption processes for organic contaminant removal from water. The hydrogel was designed by incorporating poly(acrylic acid) (PAAc) and poly(vinyl alcohol) (PVA) to create both chemical and physical crosslinked networks, while a dynamic ionically crosslinked network was introduced using Fe3+. A comprehensive range of characterization techniques confirmed the successful formation of the multi-network hydrogel. Compared to hydrogels with fewer networks, the newly developed PAAc/PVA@Fe3+ hydrogel exhibited significant enhancements in various key aspects. Notably, it demonstrated improved swelling kinetics, mechanical properties including compression strength, Young's modulus, and stretchability, and a remarkable self-healing ability with an efficiency of 88 % at 25 °C after an 8 h contact period. In batch experiments, the PAAc/PVA@Fe3+ hydrogel displayed selective adsorption capabilities, particularly for cationic dyes like methylene blue (MB), even in binary dye systems. Moreover, the hydrogel showcased impressive recycling and reusability, maintaining an MB removal efficiency of over 60 % even after undergoing 10 reuse cycles. An essential aspect of its performance was the preservation of its adsorption efficiency even after consecutive self-healing processes. The unique combination of selective adsorption, self-healing ability, and robust recycling performance positions this hydrogel as a promising candidate for efficient and sustainable water treatment solutions.

A system of FRET dyes designed to assess the degree of nano-scale contact between surfaces for interfacial adhesion

HypothesisInterfacial adhesion caused by intermolecular forces only occur between surfaces at nano-scale contact (NSC), i.e., 0.1–0.4 nm and can be evaluated using Forster resonance energy transfer spectroscopy (FRET). For this, a suitable pair of fluorescent dyes must be selected, which spectroscopic properties will determine the FRET system performance. Here, we present a brand-new FRET dye system specifically designed to measure NSC in the distance range relevant for van-der-Waals and hydrogen bonding, i.e., below 1 nm. ExperimentsWe propose the FRET pair: 7-Amino-4-methyl-cumarin (C120) and 5(6)-Carboxy-2′,7′-dichlor-fluorescein (CDCF) with high quantum yield (QY, QYC120 = 0.91 and QYCDCF = 0.64) and a distance detection range of 0.6–2.2 nm (0.1 mM). Adhered-thin films with increasing NSC degrees are produced with ascending pressure from 1.5 to 150 bar. To validate the proposed FRET measurement, we are correlating the bonded films interfacial adhesion (separation energy) to the measured FRET intensity, indicating its degree of NSC. FindingsWe find that the proposed dyes are producing the desired FRET signal in adhered-thin films, for an interaction range of 0.6–2.2 nm, with high sensitivity due to the dye’s high quantum yields. The increasing adhesion in these films is only caused by its increase in NSC. We find that the adhesion strength, measured as the separation energy between the films, is correlated to the measured FRET signal. Hence, the introduced FRET system is accurately able to measure the degree of NSC between soft surfaces.

DYEING OF COTTON WITH NATURAL COLORANTS EXTRACTED FROM RED ROSE FLOWER

Cotton substrate was dyed with an extract of red rose petals. The dyeing was carried out with and without metallic mordants (alum, copper sulphate, nickel sulphate, ferric chloride and ferrous sulphate), using two different dyeing systems: pre-mordanting system, simultaneous mordanting system. The colour of the cotton substrate was measured by Data color in terms of K/S, and CIELAB values. In both mordanting system ferrous sulphate produced dark shade, the K/S value for simultaneous system is 16.76 and for pre-mordant K/S values is 12.05. It is also observed the higher %fix is of simultaneous system for ferrous sulphate is 76.80% and for pre-moderating the % fix is 71.50%. But statistical analysis of both techniques tells us the reproducibility of copper sulphate is better to other metallic salts the S.D of K/S values for copper sulphate in simultaneous method is 0.2112 and for pre-mordant method the S.D is 0.1132.

THERMODYNAMIC STUDY OF THE ADSORPTION OF ALIZARIN RED ON ATABALGUID

This study is aimed to test the removal efficiency of the Alizarin Red Dye (ARD) from its acidic medium (pH=5.6) aqueous solution by using a local clay named Atabalguid (ATC). The optimum condition for the adsorption process were investigated, such effect of dose, effect of initial, effect of contact time, and effect of temperature. The study showed that the best amount of ATC used is (0.5gm) in a range of initial concentration that ranged between (24-216mg/l) and at a temperature range ranging between (288-328k°). The study showed that the time required to reach equilibrium was (90) minutes, and for this reason, the time (90) minutes was chosen to test the subsequent studies. Thermodynamic study was also included. Thermodynamic functions (∆So , ∆H , ∆G°) were calculated at one concentration (24 mg/L) and at several temperatures (288, 298, 308, 318,and 328). The experiment was repeated at several concentrations. ( 72, 120, 168, and 216 mg/L) The results showed, the equilibrium constant (K) decreases with increasing temperature. This is consistent with the physical nature of the adsorption process. The values of the thermodynamic functions proved that the adsorption system under study is spontaneous, and the forces controlling the bond between the alizarin red dye (ARD) molecules and the available sites on the Atabalguid clay (ATC) surface are physical in nature. The adsorption process leads to more ordered system at a concentration of 24 mg/L, while at higher concentrations the adsorption leads to more random dyes system. This can be attributed to the fact that increasing the concentration increases the number of remaining molecules in the dye solutions, thus increasing the randomness of the system, especially after equilibration

Sulfur-bridged oxotitanium phthalocyanine- and porphyrin-based cocktail dyes as sensitizers for improved dye sensitized solar cell efficiency

Effective non-symmetrical push–pull oxotitanium phthalocyanine dyes substituted with tert-butylsulfanyl groups as electron donors and carboxyethynyl units as anchor groups have been designed, prepared, and used with YD2 porphyrin as sensitizer cocktail dyes in dye-sensitized solar cells (DSSCs). The innovative phthalocyanine structures and YD2 and dye cocktails are designed to harvest a broad range from sunlight. The novel phthalocyanine dyes have been characterized via 1H NMR, FTIR, MALDI-TOF, UV–Vis absorption, CV, SWV and TD-DFT techniques. Moreover, the TiO2 NPs has been synthesis by hydrothermal procedure and characterized via XRD, FE-SEM, Raman and DRS techniques. The photoanode has been prepared with synthesized anatase TiO2 NPs using a spin coating procedure. TiO2 photoanode, dye/dye cocktails, I−/I3− electrolyte and Pt/FTO counter electrode have been utilized in the preparation of solar cells. The characterization of the prepared solar cells has been achieved via J-V, Nyquist, Bode, IPCE, normalized JSC and stability measurements. The highest conversion efficiency of the solar cell prepared with YD2:TiOSPPc (3:1) has been performed 10.96%, which this value was found to be higher than the solar cell efficiency of N719 standard dye (8.90%). With these innovative dye cocktails, it is expected that the dye system with not only high efficiency but also a relatively stable and higher VOC value will be an alternative to ruthenium-based dyes.

Efficient persulfate activation by photo-excited organic dyes: Mechanism and application for actual dyeing wastewater self-purification

Sulfate Radical-Advanced Oxidation Processes are considered an efficient way for purifying dyeing wastewater, which commonly resists conventional treatment processes owing to the complex components, low biodegradability and high toxicity. However, this emerging technique is associated with issues of secondary pollution and great energy consumption during peroxymonosulfate (PMS) or persulfate (PS) activation processes. Herein, a dye pollutant/PS/visible light self-catalytic system was constructed, based on the photosensitive property of organic dyes for PS activation without catalyst and energy input. In this system, the degradation ratio of 100 mL 10 mg L−1 basic fuchsin, rhodamine B and eosin Y significantly increased by 60%, 76% and 50%, compared with the process without light irradiation. Such improvements were attributable to an efficient photo-induced electron transfer from photo-excited dyes to PS, which has the precondition that the lowest unoccupied molecular orbital (LUMO) energy level of the dye is higher than that of PS, thereby generating oxidizing species like ·SO4−, ·OH and 1O2 for pollutants degradation. Due to the high performance of pollutants simultaneous removal, wide pH adaptability and anti-interference, the complex self-catalytic system consisted of nine dyes and bis-phenol A exhibited the possibility for practical application. Expectedly, the actual dyeing wastewater self-purification system featured a decolorization efficiency of 54% accompanied by the removal of co-existing aromatic proteins and tryptophan-like substances; moreover, the acute bio-toxicity of the raw wastewater greatly decreased by 61.6%. Owing to its high efficiency, eco-friendliness and low consumption, the constructed “using waste to treat waste” system provides a promising way for wastewater treatment.

Deep insights into kinetics, optimization and thermodynamic estimates of methylene blue adsorption from aqueous solution onto coffee husk (Coffee arabica) activated carbon

In the current study, an attempt was made to synthesize coffee husk (CH) activated carbon by chemical modification approach (sulphuric acid-activated CH (SACH) activated carbon) and was used as a valuable and economical sorbent for plausible remediation of Methylene blue (MB) dye. Batch mode trials were carried out by carefully varying the batch experimental variables: SACH activated carbon (SACH AC) dosage, pH, initial dye concentration, temperature, and contact time. The optimum equilibrium time for adsorption by SACH activated carbon was obtained as 60 min, and the maximum adsorption took place at 30 °C. Morphological and elemental composition, crystallinity behaviour, functional groups, and thermal stability were examined using SEM with EDX, XRD, FTIR, BET, TGA, and DTA and these tests showed successful production of activated carbon. The outcomes showed that chemical activation enhanced the number of pores and roughness which possibly maximized the adsorptive potential of coffee husk. The Box-Benken design (BBD) was used to optimize the MB dye adsorption studies and 99.48% MB dye removed at SACH AC dosage of 4.83 g/L at 30 °C for 60 min and pH 8.12, and the maximum adsorption was yielded for sulphuric acid-activated coffee husk carbon carbon with 88.1 mg/g maximum MB adsorption capacity. Langmuir- Freundlich model deliberately provided a better fit to the equilibrium data. The SACH AC-MB dye system kinetics showed a high goodness-of-fit with pseudo second order model, compared to other studied models. Change in Gibbs's free energy (ΔGo) of the system indicated spontaneity whereas low entropy value (ΔSo) suggested that the removal of MB dye on the SACH activated carbon was an enthalpy-driven process. The exothermic nature of the sorption cycle was affirmed by the negative enthalpy value (ΔHo). The adsorptive-desorptive studies reveal that SACH AC could be restored with the maximum adsorption efficiency being conserved after the fifth cycles. Overall, the outcomes revealed that sulphuric acid-activated coffee husk activated carbon (SACH AC) can be used as prompt alternative for low-cost sorbent for treating dye-laden synthetic wastewaters.

A hierarchical strategy for fabricating synergistic 3D network bio-based porous carbon and 0D niobium-based bimetallic oxides as counter electrodes for I- and Cu-mediated dye-sensitized solar cells with N719 and Y123 dyes

Designing cost-effective counter electrode (CE) catalysts with advanced nanostructures and exploring their application in different dye-electrolyte systems is crucial for the development of dye-sensitized solar cells (DSSCs). In this work, two types of 3D network bio-based porous carbon (3D-BPC) loaded 0D niobium-based bimetallic oxide nanohybrids (CoNb2O6/3D-BPC and NiNb2O6/3D-BPC) were synthesized using a hierarchical strategy. Benefiting from the optimization of the electron transport pathways and enrichment of catalytically active sites via the hierarchical 0D/3D structure, formed by 3D-BPC and MNb2O6 (M = Co, Ni), the catalytic reduction ability of MNb2O6/3D-BPC was significantly enhanced. To explore the photovoltaic performance of the MNb2O6/3D-BPC based DSSC, the I3−/I− electrolyte and N719 dye system and the Cu2+/Cu+ electrolyte and Y123 dye system were simultaneously employed. The solar cells assembled with the CoNb2O6/3D-BPC and NiNb2O6/3D-BPC CE exhibited device efficiencies of 7.03% and 7.14% in the N719-I3−/I− system, respectively, and 1.84% and 2.42% in the Y123-Cu2+/Cu+ system, respectively, which were almost equal to those of Pt under the same system. Additionally, MNb2O6/3D-BPC catalysts exhibited promising stability in I3−/I− electrolyte. This work provides guidance for the construction of low-cost and high-efficiency nanohybrid catalysts for new energy conversion devices.