Mixed Dye Solutions Research Articles

Anti‐fouling loose polyamide nanofiltration membrane preparation by biodegradable sophorolipids for precise separation of simulated dyeing wastewater

AbstractBackgroundStrengthening the recycling and utilization of resources is deeply significant in achieving carbon neutrality. The nanofiltration membranes possess separation ability within the nanoscale by utilizing special pore size ranges and surface charge properties, showing great application prospects in resource recycling. The commercial nanofiltration membranes are mainly prepared by interfacial polymerization with fast reaction speed and easy scaling‐up advantages. However, the obtained polyamide nanofiltration membranes possess dense selective layers with low permeance and separation efficiency to the molecules. Herein, the biodegradable surfactant sophorolipid was added to the aqueous solution to improve the performance of the polyamide nanofiltration membranes.ResultsCompared with the traditional nanofiltration membranes, the permeance of the sophorolipid‐modified nanofiltration membrane was improved from 3 to 18 L·m−2·h−1·bar−1. The modified membrane showed high rejection of the dyes with large molecular structures and low rejection of those with small molecular structures.ConclusionThe modified membrane may separate the mixed dye solution of congo red (molecular weight 696.66 g/mol) and indigo carmine (molecular weight 407.98 g/mol) and the mixed congo red/NaCl solution precisely. Besides, the modified membrane showed good anti‐fouling properties in the long‐term stability test. This study may offer research significance for the resource treatment of printing and dyeing wastewater. © 2024 Society of Chemical Industry (SCI).

Dicarboxylate cellulose nanofibrils-supported silver nanoparticles as a novel, green, efficient and recyclable catalyst for 4-nitrophenol and dyes reduction

This study reports dicarboxylate cellulose nanofibrils (DCNF) as a novel reducing and supporting agent for producing silver nanoparticles (AgNPs) with high efficiency (63.82 % reduction) and loading (6.88 %) using UV light. Unlike previous research, AgNPs formation with DCNF doesn't involve cellulose oxidation. Instead, it appears to involve a loss of carboxyl groups from DCNF. In comparative studies, pristine CNF (PCNF) and TEMPO-oxidized CNF (TOCNF) were also examined for AgNPs production. The resulting AgNPs from DCNF exhibited a significantly smaller average size (3.9 ± 0.7 nm) compared to those from PCNF (26.9 ± 10.9 nm) and TOCNF (13.5 ± 4.5 nm). Catalytic activity evaluation by the 4-nitrophenol (4-NP) reduction reaction revealed a high rate constant of 8.47× 10−3 s−1 by AgNPs/DCNF, which surpassed AgNPs/TOCNF (1.79 × 10−3 s−1) and AgNPs/PCNF (0.63 × 10−3 s−1) by 4.7 and 13.4 times, respectively. Besides 4-NP, AgNPs/DCNF aerogels were also applied for methyl orange and Rhodamine B dyes reduction. The aerogels showed excellent reusability, maintaining over 95 % conversion even after five cycles and also effective in treating real samples and mixed dye solutions. This study opens the door for future research exploring DCNF as a support material for various metal, metal oxide, and carbon nanoparticles.

Facile construction of ZnWO4/g-C3N4 heterojunction for the improved photocatalytic degradation of MB, RhB and mixed dyes

This study presents the construction of binary ZnWO4/g-C3N4 nanocomposite via a facile hydrothermal approach to enhance the photocatalytic performance under the visible light irradiation. The proposed ZnWO4/g-C3N4 nanocomposite photocatalyst shows excellent photodegradation towards organic dyes, such as methylene blue (MB) and rhodamine B (RhB). The optimal loading of ZnWO4 and g-C3N4 leads to the synergistic effect which plays a predominant role in inhibiting the fast electron-hole pairs recombination rate at the interface of ZnWO4/g-C3N4 photocatalyst. The degradation rates of MB and RhB is achieved around 92.9 % and 88.8 % under the visible light irradiation for 120 min. According to our findings, the radical quenching experiments suggested that the ●OH radicals played a positive impact in the photodegradation process. Since, our proposed photocatalyst exhibit superior photocatalytic activity towards the individual MB and RhB degradation. The ZnWO4/g-C3N4 photocatalyst were further applied to demonstrate the degradation of mixed dyes (MB and RhB) at an irradiation time of 180 min. In the mixed dye solution, the ZnWO4/g-C3N4 photocatalyst achieved a highest reaction rate of 0.010 min−1 for MB and 0.012 min−1 for RhB with the degradation rate of 87.8 % and 83.3 % for RhB and MB, respectively. For the mixed dyes, the radical quenching experiments confirmed that the ●OH radicals are responsible for the fast photodegradation. Additionally, the practicality of the proposed ZnWO4/g-C3N4 photocatalyst towards the degradation of MB, RhB and the mixed dyes were examined in the tap water samples. Furthermore, the plausible photodegradation mechanism of ZnWO4/g-C3N4 photocatalyst was proposed in detail. This study provides a new insight for the simultaneous degradation of mixed chemical pollutants using our proposed ZnWO4/g-C3N4 photocatalyst.

Facile fabrication of superhydrophilic copper foam for rapid and efficient filtration of cationic dyes from water

Rapid and efficient separation of dyes from water is a formidable challenge due to the trade-off between separation selectivity and permeability. Here, a novel superhydrophilic copper foam (CF) enabling the rapid and efficient filtration of cationic dyes from water is reported. The fabrication involves brushing a coating consisting of attapulgite (APT), poly(vinyl alcohol) (PVA), TiO2 and glutaraldehyde (GA) onto copper foam and then heating. The obtained copper foam (CF-PVA/GA@APT/TiO2) is superhydrophilic and negatively charged with dye adsorption capability. The interconnected cage-shaped porous structure endows the foam with long tortuous permeation channels and large pore size. It is able to separate various cationic dyes with a separation efficiency reaching to 99.93 % and a permeation flux up to 1671 ± 189 L m-2h−1 under gravity. Furthermore, the CF-PVA/GA@APT/TiO2 can realize the selective separation and recovery of various cationic dyes from rhodamine B (RhB)-mixed dye solutions. Molecular dynamics-based computational modeling and experimental studies revealed that the interaction energy between the surface of CF-PVA/GA@APT/TiO2 and methylene blue (MB) is much stronger than that of the former and RhB, leading to adsorption of MB in the permeation channel, while RhB gradually migrates through the permeation channel and passes through the channel with water. The tortuous permeation channels of CF-PVA/GA@APT/TiO2 increase the contact area and absorption opportunities for cationic dye molecules on the surface, and its large pore size maintains the filtration flux. These properties provide the as-prepared foam with excellent potential applicability for industrial dye wastewater treatment.

Facile Fabrication of Porous Adsorbent with Multiple Amine Groups for Efficient and Selective Removal of Amaranth and Tartrazine Dyes from Water.

The development of an advanced dye adsorbent that possesses a range of beneficial characteristics, such as high adsorption capacity, swift adsorption kinetics, selective adsorption capability, and robust reusability, remains a challenge. This study introduces a facile method for fabricating an amine-rich porous adsorbent (ARPA), which is specifically engineered for the adsorptive removal of anionic dyes from aqueous solutions. Through a comprehensive assessment, we have evaluated the adsorption performance of ARPA using two benchmark dyes: amaranth (ART) and tartrazine (TTZ). Our findings indicate that the adsorption process reaches equilibrium in a remarkably short timeframe of just 20 min, and it exhibits an excellent correlation with both the Langmuir isotherm model and the pseudo-second-order kinetic model. Furthermore, ARPA has demonstrated an exceptional maximum adsorption capacity, with values of 675.68 mg g-1 for ART and 534.76 mg g-1 for TTZ. In addition to its high adsorption capacity, ARPA has also shown remarkable selectivity, as evidenced by its ability to selectively adsorb TTZ from a mixed dye solution, a feature that is highly desirable for practical applications. Beyond its impressive adsorption capabilities, ARPA can be efficiently regenerated and recycled. It maintains a high level of original removal efficiency for both ART (76.8%) and TTZ (78.9%) even after five consecutive cycles of adsorption and desorption. Considering the simplicity of its synthesis and its outstanding adsorption performance, ARPA emerges as a highly promising material for use in dye removal applications. Consequently, this paper presents a straightforward and feasible method for the production of an effective dye adsorbent for environmental remediation.

Efficacy of Mg-Al-layered double hydroxide nano-adsorbents for a multi-anionic mixed dye solution

Through this work, we show the efficacy of Mg-Al layered double hydroxide (LDH) as an efficient multi-anionic toxic dye adsorbent. Contrary to typical dye adsorption experiments where a single dye is usually tested for checking the potency of a particular adsorbent, eight different (anionic) dyes (comprising of anionic, reactive, azo, and acid dyes) were blended into one dye solution so that it can closely mimic a wastewater effluent of anionic dyes. With LDH adsorbent, the dye adsorption experiments depicted ∼ 100 % dye removal for all eight individual dye solutions along with the mixed dye solution in just two minutes.

Pyridinium and trifluoromethanesulfonate bifunctional poly(ionic liquid)s for highly efficient and selective adsorption of anionic dyes

The efficient and selective removal of dyes from polluted water by low cost, durable, sustainable, and reusable adsorptions remain challenges. In this study, a pyridinium and trifluoromethanesulfonate bifunctional poly(ionic liquid)s, named Py-CF3SO3-PIL was prepared by co-polymerization of 4-vinyl pyridine (4VP), divinylbenzene (DVB) and styrene (ST), followed by quaternization with 1-bromobutane and anion exchange with lithium trifluoromethanesulfonate. The resulting bifunctional Py-CF3SO3-PIL exhibited remarkable adsorption capacity (2192 mg g−1) and efficiency (within 10 min) for selective removal (>99.9%) of methyl orange (MO) from (mixed) dye solutions. The superior adsorption capacity and selectivity of Py-CF3SO3-PIL towards the removal of MO was attributed to the strong electrostatic interactions and π-π stacking interaction between the adsorbent and MO dye. Detailed kinetic studies, adsorption isotherms, and thermodynamic experiments revealed an endothermic monolayer chemical adsorption mechanism of MO on Py-CF3SO3-PIL, which is perfectly matched with the Langmuir isotherm model (R2 > 0.999). Importantly, the Py-CF3SO3-PIL could be easily collected and regenerated for multiple repeated uses, highlighting its reusability. The exceptional adsorption capacity and selectivity towards anionic dyes make Py-CF3SO3-PIL a promising candidate for dye separation applications. Our findings will contribute to the rational design of functional poly(ionic liquid)s-based adsorbents for water purification.

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.

UV‐initiated preparation and absorption properties of pseudo‐polyrotaxane cyclodextrin‐based PVA/poly (acrylamide‐co‐acrylic acid) hydrogel

AbstractThe recycling of dyes from dye wastewater is one of the most challenging problems in wastewater treatment. In this study, a pseudo‐polyrotaxane cyclodextrin based PVA/poly (acrylamide‐co‐acrylic acid) hydrogel was prepared by UV‐initiated polymerization. The network structure of the hydrogel and the performance on the dye absorption were adjusted by controlling the content of cyclodextrin. The study was mainly focused on the absorption of methylene blue (MB) in different environments, selectivity of absorption in mixed solutions and the cyclic absorption behavior. At room temperature, the absorption efficiency of this hydrogel for MB and methylene green reached 91.37% and 94.23%, respectively. In addition, the hydrogel exhibited highly selective absorption towards MB in mixed dye solutions. In the absorption‐desorption cyclic experiments, a more cost‐effective and environmental friendly solvent, a mixture of ethanol and water, was used, and after ten cycles, the highest absorption efficiency was basically maintained. Hence, the hydrogel is expected to be a candidate for more efficient and economical absorbent material in dye wastewater treatment.

Preparation of copolymer brush‐type restricted access microspheres with adjustable adsorption selectivity to variety of dyes

AbstractRestricted access materials (RAMs) with adjustable selectivity was developed for the removal and detection of residual dyes for the solve problems of dye contamination. In this work, using homemade poly(4‐vinylbenzyl chloride‐co‐divinylbenzene) (PVBC/DVB) microspheres as substrate and successive two‐step surface‐initiated atom transfer radical polymerization (SI‐ATRP) as synthesis method, the two types of monomers, sodium 4‐vinylbenzene sulfonate (Nass) and styrene (St) were first grafted for constructing mixed interactions of adsorption sites, and then the hydrophilic glycidyl methacrylate (GMA) was polymerized, following by hydrolysis to construct diol groups on the external PVBC/DVB as the restricted access sites. The developed PVBC/DVB@poly(St‐co‐Nass)@poly(GMA) of adsorption properties was investigated by six dyes including methylene blue (MB), basic fuchsin (BF), acid fuchsin (AF), neutral red (NR), methyl orange (MO), and Congo red (CR), the adsorption capacities of those dyes and the removal rate for the binary mixed dye solution both rely on the ratio of St/Nass, confirming the adjustable adsorption selectivity. When PVBC/DVB@poly(St‐co‐Nass)@poly(GMA) was packed as solid phase extraction adsorbent in couple with UV–vis spectrum, it was applied to the determination of MB and BF in the water, fish and shrimp, good linearity with satisfactory recoveries for MB and BF are obtained to show the favorable practicability.

Remediation of charged organic pollutants—binding motifs for highly efficient water cleaning with nanoparticles

AbstractMany charged organic molecules behave as persistent and hazardous pollutants with harmful effects on human health and ecosystems. They are widely distributed related to their charged molecular structure that provides water solubility. In order to track the fate and behavior of such pollutants, charged dyes with specific absorption in the visible spectra serve as convenient model compounds. We provide a platform of smart adsorbers that efficiently remediate positively and negatively charged dyes (crystal violet and Amaranth) from water. Metal oxide nanoparticles serve as a core with an intrinsically large surface area. The surface potential was tuned towards positive or negative by decorating the cores with self‐assembled monolayers of dedicated long‐chained phosphonic acid derivatives. Selective remediation of the dyes was obtained with corresponding oppositely charged core‐shell nanoparticles. Mixed dye solution can be cleaned by a cascade approach or by applying both particle systems simultaneously. The removal efficiency was determined as a function of particle concentration via UV‐spectroscopy. The results of remediation experiments at different pH values and using superparamagnetic iron oxide nanoparticle cores lead to a simple process with recycling capability.

Magnetic nanocellulose-based adsorbent for highly selective removal of malachite green from mixed dye solution

Herein, a novel magnetic adsorbent (BC/AA/MN@Fe3O4) was successfully prepared from waste bamboo fiber tissue and montmorillonite, and subsequently applied for the highly selective removal of malachite green (MG, removal efficiency = 97.3 %) from the mixed dye solution of MG with methyl orange (MO, removal efficiency = 4.5 %). The magnetic adsorbent has a high porosity with abundant mesopores. In the single dye MG solution, the adsorbent could effectively remove MG over a wide pH range from 4 to 10, and the maximum adsorption capacity (qmax) was 2282.3 mg/g. Moreover, the magnetic adsorbent could remove MG from various solutions including mixed dye solution, high salinity solution, and real river water dye solution. The thermodynamic results proved that the adsorption process of MG was spontaneous and endothermic. The adsorption of MG was due to the comprehensive effects of electrostatic attraction, hydrogen bonding interactions and ions exchange, between the adsorbent and MG. Furthermore, the BC/AA/MN@Fe3O4 exhibited an excellent reusability with adsorption efficiency above 53.4 % after five consecutive cycles. Therefore, the prepared magnetic nanocellulose-based adsorbent was expected to be a promising material for highly selective adsorption and separation of MG from mixed dye solution.

Application of a Mixed-Ligand Metal–Organic Framework in Photocatalytic CO2 Reduction, Antibacterial Activity and Dye Adsorption

In this paper, a known mixed-ligand MOF {[Co2(TZMB)2(1,4-bib)0.5(H2O)2]·(H2O)2}n (compound 1) was reproduced, and its potential application potential was explored. It was found that compound 1 had high photocatalytic activity for CO2 reduction. After 12 h of illumination, the formation rate of CO, which is the product of CO2 reduction by compound 1, reached 3012.5 μmol/g/h. At the same time, compound 1 has a good antibacterial effect on Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and Candida albicans (C. albicans), which has potential research value in the medical field. In addition, compound 1 can effectively remove Congo Red from aqueous solutions and achieve the separation of Congo red from mixed dye solutions.

Unusual, hierarchically structured composite of sugarcane pulp bagasse biochar loaded with Cu/Ni bimetallic nanoparticles for dye removal

Biochar-supported nanocatalysts emerged as unique materials for environmental remediation. Herein, sugarcane pulp bagasse (SCPB) was wet-impregnated with Cu(NO3)23H2O and Ni(NO3)26H2O, then pyrolyzed at 500 °C, under N2, for 1 h. We specifically focused on sugarcane pulp instead of SCB and biochar materials. The metal nitrate to biomass ratio was set at 0.5, 1, and 2 mmol/g, with Cu/Ni initial ratio = 1. The process provided hierarchically structured porous biochar, topped with evenly dispersed 40 nm-sized CuNi alloy nanoparticles (SCPBB@CuNi). The biochar exhibited an unusual fishing net-like structure induced by nickel, with slits having a length in the 3–12 μm range. Such a fishing net-like porous structure was obtained without any harsh acidic or basic treatment of the biomass. It was induced, during pyrolysis, by the nanocatalysts or their precursors. The CuNi nanoparticles form true alloy as proved by XRD, and are prone to agglomeration at high initial metal nitrate concentration (2 mmol/g). Stepwise metal loading was probed by XPS versus the initial metal nitrate concentration. This is also reflected in the thermal gravimetric analyses. The SCPBB@CuNi/H2O2 (catalyst dose: 0.25 g/L) system served for the catalyzed removal of Malachite Green (MG), Methylene Blue (MB), and Methyl Orange (MO) dyes (concentration = 0.01 mmol/L). Both single and mixed dye solutions were treated in this advanced oxidation process (AOP). The dyes were removed in less than 30 min for MG and 3 h for MB, respectively, but 8 h for MO, therefore showing selectivity for the degradation of MG, under optimized degradation conditions. The catalysts could be collected with a magnet and reused three times, without any significant loss of activity (∼85%). AOP conditions did not induce any nanocatalyst leaching.To sum up, we provide a simple wet impregnation route that permitted to design highly active Fenton-like biochar@CuNi composite catalyst for the degradation of organic pollutants, under daylight conditions.

Enhanced simultaneous degradation of simulated dyes using ZnO/GCN heterojunction photocatalyst.

The scarcity of water leads to research nowadays to focus on techniques for treating wastewater. Photocatalysis emerged as a technique of interest due to its nature of friendliness. It utilizes light and catalyst to degrade the pollutants. One of the popular catalysts to be used is zinc oxide (ZnO), but its usage is limited due to the high recombination rate of electron-hole pair. Herein, in this study, ZnO is modified with graphitic carbon nitride (GCN), and the GCN loading amount was varied to study the impact on photocatalytic degradation of mixed dye solution. To the best of our knowledge, this is the first work that reports on the degradation of mixed dye solution using modified ZnO with GCN. Structural analysis showed that GCN is present in the composites which proves the success of the modification. Photocatalytic activity revealed that the composite with 5 wt% loading of GCN showed the best activity at a catalyst dosage of 1 g/L with degradation rates of 0.0285, 0.0365, 0.0869, and 0.1758 min-1 for methyl red, methyl orange, rhodamine B, and methylene blue dyes, respectively. This observation is expected due to the formation of heterojunction between ZnO and GCN which creates a synergistic effect and thus led to an improvement in the photocatalytic activity. Based on these results, ZnO modified with GCN has a good potential to be used in the treatment of textile wastewater which consists of various dye mixtures.

Preparation of paramagnetic ferroferric oxide-calcined layered double hydroxide core–shell adsorbent for selective removal of anionic pollutants

Adsorption is one of the most common methods of pollution treatment. The selectivity for pollutants and recyclability of adsorbents are crucial to reduce the treatment cost. Layered double hydroxide (LDH) materials are one type of adsorbent with poor recyclability. Prussian blue (PB) is a sturdy and inexpensive metal–organic framework material that can be used as the precursor for synthesizing paramagnetic ferroferric oxide (Fe3O4). It is intriguing to build some reusable adsorbents with magnetic separation by integrating LDH and PB. In this work, paramagnetic Fe3O4-calcined LDH (Fe3O4@cLDH) core–shell adsorbent was designed and prepared by the calcination of PB-ZnAl layered double hydroxide (PB@LDH) core–shell precursor, which exhibits high anionic dyes selectivity in wastewater solutions. The paramagnetism and adsorption capability of Fe3O4@cLDH come from the Fe3O4 core and calcined ZnAl-LDH shell, respectively. Fe3O4@cLDH shows an adsorption capacity of 230 mg g−1 for acid orange and a high selectivity for anionic dyes in cation–anion mixed dye solutions. The regeneration process indicates that the high selectivity for anions is related to the specific hydration recovery process of ZnAl-LDH. The synergistic effect of the paramagnetic Fe3O4 core and calcined ZnAl-LDH shell makes Fe3O4@cLDH an excellent magnetic separation adsorbent with high selectivity to anions.

Porous amorphous metal-organic frameworks based on heterotopic triangular ligands for iodine and high-capacity dye adsorption.

The research on amorphous metal-organic frameworks (aMOFs) is still in its infancy, and designing and constructing aMOFs with functional pores remains a challenge. Two aMOFs based on Co(II) and heterotopic triangular ligands with large conjugated aromatic planes, namely aMOF-1 and aMOF-2, were constructed and characterized by IR, XPS, EA, ICP, XANS and so on. aMOF-1 possesses mesopores, whereas aMOF-2 possesses micropores. The porosity, conjugated aromatic plane and uncoordinated N atoms in the framework allow these aMOFs to adsorb iodine and dyes. The iodine adsorption capacity of aMOF-1 is 3.3 g per g, which is higher than that of aMOF-2 (0.56 g per g), mainly due to the expansion or swelling of aMOF-1 after iodine adsorption. The uptake of cationic dyes by aMOF-2 showed more rapid kinetics and a higher removal rate than that by aMOF-1, mainly due to the difference in the porosity and surface charge. Although the surface charges of aMOF-1 and aMOF-2 are negative, both of them showed significantly faster adsorption kinetics toward anionic dyes, among which methyl orange (MO) and Congo red (CR) can be removed in 5 min. This occurs possibly because the quick adsorption of Na+ ions alters the surface charge of the framework and promotes dye uptake. The adsorption capacities of aMOF-1 for MO and CR reached 921 and 2417 mg g-1, respectively. The correlation data for aMOF-2 are 1042 and 1625 mg g-1, respectively. All adsorption capacities are among the highest compared to many cMOFs. Adsorption in mixed dye solution is found to be charge-dependent, kinetic-dependent, and synergetic in these systems. The porosity, surface charge regulation during adsorption, weak interactions and multiple adsorption processes contribute to the dye adsorption performance.

Cobalt oxide nanoparticles by flame pyrolysis for efficient removal of mixed dyes

The cobalt oxide nanoparticles were prepared by low cost, gram scalable and environment friendly flame pyrolysis method by directly burning ethanolic solution of cobalt chloride. The cobalt oxide formation, functional group identification, morphology and particles size of as-synthesized nanoparticles were carried out using routine techniques viz. XRD, FTIR, FE-SEM, HR-TEM, Raman Spectroscopy and Vibrating Sample Magnetometer (VSM) analysis. The XRD pattern ensured the formation of Cobalt Oxide nanoparticles (CoO NPs). It also emphasized that synthesized CoO NPs are pure, crystalline and single phased. EDS ensured the purity of CoO NPs which contained only cobalt and oxygen. FE-SEM exhibited spherical morphology with particles size of around 30 nm aligned with Debye–Scherrer’s calculated average crystallite size of 20 nm. The optical direct band gap of CoO NPs was estimated using Kubelka - Munk function to be 2.97 eV. The magnetic behavior examined at room temperature by VSM confirmed the formation of CoO NPs with weak ferromagnetic nature. The CoO NPs were utilized successfully for the removal of mixed dye solutions. The CoO NPs showed excellent efficiency for the removal of mixture of hazardous dyes from the aqueous solutions. This makes CoO NPs valuable for removal of industrial dyes and colorants for the waste water treatment processes.

Graphene oxide enabled self-assembly of silver trimolybdate nanowires into robust membranes for nanosolid capture and molecular separation.

A graphene oxide (GO) assisted self-assembly strategy for growing a silver trimolybdate nanowire membrane with capabilities of nanosolid capture and small molecule separation is reported. Thanks to the GO bridges and the accurate self-assembly process, the resulting membrane exhibits outstanding mechanical properties (can withstand 4300 times its weight) and impressively high porosity (97%). On the basis of the robustness and high porosity of the membrane, column-shaped filter apparatus has been fabricated, in which the membrane served as a self-standing permeation barrier to assess its permeability and practical application as a nanosolid filter and molecule filter. The permeability test of the membrane with pure water uncovers that the membrane exhibits fast permeability while driven by hydrostatic pressure only because of its significantly high porosity. The separation test of the membrane with P25 TiO2 solution, 13 nm Au solution, and yellow-emitting CdTe QDs reveals that all the tiny nanosolids are completely removed from the solution, which suggests that the membrane is an efficient nanosolid filter. Its efficiency is increased by the induction of surface collision from numerous nanowire barriers and the deposition of nanosolids on the nanowire surface. The separation test of the membrane with a mixed-dye solution reveals that sulfur containing methylene blue (MB) molecules are highly efficiently extracted under various chemical conditions, evidencing that the membrane is an ideal molecule filter too. Its high selectivity and high efficiency originated from the Ag-S bonding between the interlayered silver ions of the silver trimolybdate nanowire and the sulfur atom of MB molecules. Based on the above results, the silver trimolybdate nanowire membrane has been applied to purify drugs, which successfully removed sulbactam sodium impurity F from sulbactam sodium, demonstrating a purity increment from 98.92% to 99.93%. The present work should provide a significant step forward to bringing macroscopic 1D nanomaterial architectures much closer to real-world applications involving isolation and enrichment of catalyst reclamation, high-value chemical recovery, drug purification, and environmental remediation.

Simultaneous Removal of Cationic Crystal Violet and Anionic Reactive Yellow Dyes using eco-friendly Chitosan Functionalized by Talc and Cloisite 30B

Designing adsorbent materials that can effectively remove many types of organic dyes is crucial because of the wide diversity of synthetic dyes found in wastewater. Thus, this study presents the synthesis of economic and eco-friendly adsorbent composites composed of chitosan (Cs), talc (T), and Cloisite 30B clay (C) to remove both cationic crystal violet (CV) and anionic reactive yellow 145 (RY) dyes for the first time. Cs was functionalized with T and subsequently the CsTC1 and CsTC2 composites were prepared by sensitizing the obtained CsT with different weight ratios of Cloisite 30B (C). X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), N2 adsorption–desorption isotherm, and zeta potential analysis were employed to characterize the materials. The addition of T to Cs matrix improves the thermal stability, pore size, and pore volume with respect to pure Cs. The effect of C inclusion was examined by measuring the affinity of the prepared composites towards adsorption of cationic CV and anionic RY dyes in comparison to pure Cs and CsT composite. The adsorption results in a single dye solution revealed that the CsTC1 composite is the most effective adsorbent for removal of RY dye with 76.9 mg/g adsorption capacity, whereas the CsTC2 composite exhibited the highest adsorption activity for CV dye (37.03 mg/g). Furthermore, RY and CV co-adsorption on CsTC composites was tested from a mixed dye solution. The adsorption kinetics of RY and CV adsorption followed the pseudo second order model. Langmuir isotherm model described the experimental adsorption data better than the Freundlich, Dubinin–Radushkevich, and Temkin isotherm models, indicating a monolayer sorption process for both dyes. The proposed mechanism for RY and CV adsorption using CsTC composites was investigated.