Dye Adsorption Capacity Research Articles

Green Synthesis and Characteristics of Cellulose Nanocrystal/Poly Acrylic Acid Nanocomposite Thin Film for Organic Dye Adsorption during Water Treatment.

Nanocellulose shows potential as an effective natural adsorbent for removing harmful contaminants from wastewater. This paper describes the development of innovative nanocellulose thin films made of cellulose nanocrystals (CNCs), polyacrylic acid (PAA), and active carbon (AC) as adsorbent materials for absorbing azo dyes from wastewater. The CNCs were recovered from sugarcane bagasse using alkali treatment and acid hydrolysis. The composition and processing parameters of the thin films were optimized, and their adsorption capacity was determined using thermodynamic isotherms and adsorption kinetics. Adsorption characteristics such as the methylene blue (MB) dye concentration, contact time, temperature, and pH were investigated to determine how they affected adsorption. The results show that the adsorption process follows pseudo-second-order kinetics. At an adsorbent mass of 50 mg, dye concentration of 50 ppm in 50 mL, and contact period of 120 min at 25 °C, the thin film comprising 64 wt% CNC, 16 wt% PAA, and 20 wt% AC showed high dye removal efficiency (86.3%) and adsorption capacity (43.15 mg/g). The MB removal efficiency increased to 95.56% and the adsorption capacity to 47.78 mg/g when the medium's pH was gradually increased from neutral to alkaline. The nontoxicity, low production cost, water stability, easy recovery, and high adsorption capacity of these membranes make them suitable for water treatment systems.

Bimetallic (Fe/Zn-ZIF-8) crystals: Fabrication and adsorptive removal activity

This work presents an investigation on the fabrication and characterization of Fe doped zeolitic imidazolate framework (ZIF-8) of 1:1 M ratio of Zn:Fe (Fe/Zn-ZIF-8) and adsorption performances of acquired materials. The synthesized Zn-ZIF-8, Fe-ZIF-8, and Fe/Zn-ZIF-8 materials were characterized for the phase structure, morphology, elemental analysis and surface area by using X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM), Energy Dispersive X-Ray (EDX), and BET surface area, respectively. The results revealed the adsorption capacity was enhanced by incorporation of Fe into ZIF-8 structure. The CR dye adsorption capacities were 287, 219, and 412 mg/g for Zn-ZIF-8, Fe-ZIF-8, and Fe/Zn-ZIF-8 adsorbers, respectively. The CR adsorption obeyed to the pseudo 2nd order model and the Langmuir model was most closely matched during the high value of correlation coefficient (R2), signifying a palpable monolayer adsorption rather than multilayer.

Green synthesis of eco-friendly magnetic metal-organic framework nanocomposites (AlFum -graphene oxide) and pollutants (dye and pharmaceuticals) removal capacity from water

Herein, Graphene Oxide (GO), CoFe2O4, CoFe2O4/GO nanocomposite, aluminum fumarate (AlFum), and AlFum-CoFe2O4/GO (ACG) eco-friendly nanocomposites with different amounts of CoFe2O4/GO nanocomposite (5, 10, and 15 wt% denoted as 5ACG, 10ACG, and 15ACG, respectively) were green synthesized and characterized using FTIR, SEM, XRD, TEM, XRD, EDX, and BET. The XRD patterns of ACGs indicate that AlFum is fixed onto the surface of CoFe2O4/GO and its structure is well maintained. The SEM and TEM images indicated the 10ACG with good size distribution and shape. The EDX spectrum of ACG showed the homogeneous distribution of O, Fe, and Co in the synthesized materials. The synthesized ACG nanocomposite dispersed in water could be effortlessly separated from wastewater by an external magnet within several seconds. The dye (Direct Red 23: DR23) adsorption capacity of AlFum, 5ACG, 10ACG, and 15ACG was 120, 145, 230, and 167 mg/g, respectively. The Langmuir isotherm is a more adequate isotherm for characterizing the adsorption (R2 = 0.9998, 0.9918, 0.9997, and 0.9996 for AlFum, ACG-5, ACG-10, and ACG-15 respectively). Adsorption followed the pseudo-second-order kinetic. In addition, the synthesized composite had pharmaceuticals (tetracycline and doxycycline) removal ability.

Effective Adsorptive Removal of Coomassie Violet Dye from Aqueous Solutions Using Green Synthesized Zinc Hydroxide Nanoparticles Prepared from Calotropis gigantea Leaf Extract

The removal of color from dye wastewater is crucial, since dyes are extremely toxic and can cause cancer in a variety of life forms. Studies must be done to use cost-effective adsorbents for the removal of color from dye effluents to protect the environment. To our knowledge, virtually no research has been done to describe the possibility of using Calotropis gigantea leaf extract zinc hydroxide nanoparticles (CG-Zn(OH)2NPs) as an adsorbent for the decolorization of Coomassie violet (CV) from the aqueous emulsion, either in batch mode or continuously. In the present batch investigation, CV dye is removed from the synthetic aqueous phase using CG-Zn(OH)2NPs as an adsorbent. The synthesized nanoparticles were characterized using various instrumental techniques such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and Brunauer–Emmett–Teller (BET) surface area and pore volume, a particle size analyser, and zero-point charge. The decolorization efficacy of CV dye from an aqueous phase by the adsorbent was examined in batch mode by varying process parameters. The consequences of various experimental variables were optimized using response surface methodology (RSM) to achieve the maximum decolorization efficiency (90.74%) and equilibrium dye uptake, qe (35.12 mg g−1). The optimum pH, dye concentration, CG-Zn(OH)2NPs adsorbent dosage, and particle size were found to be 1.8, 225 mg L−1, 5 g L−1, and 78 μm, respectively for CV dye adsorption capacity at equilibrium. The adsorbent zero-point charge was found to be at pH 8.5. The Langmuir isotherm model provided a good representation of the equilibrium data in aqueous solutions, with a maximum monolayer adsorption capability (qmax) of 40.25 mg g−1 at 299 K. The dye adsorption rate follows a pseudo-second-order kinetic model at various dye concentrations, which indicated that the reaction is more chemisorption than physisorption. The negative values of ΔG and positive values of ΔH at different temperatures indicate that the adsorption process is spontaneous and endothermic, respectively. Reusability tests revealed that the prepared nanoparticles may be used for up to three runs, indicating that the novel CG-Zn(OH)2NPs seems to be a very promising adsorbent for the removal of Coomassie violet dye from wastewater.

Facile fabrication of bioinspired hierarchical porous MOFs for selective adsorption of Congo red and Malachite green from vegetables and fruits juices

The dye pollution in environmental water and food caused by industrial production and illegal addition is a serious problem worldwide, which endangers ecosystem, food safety and human health. To effectively overcome these challenges, a magnetic bioinspired hierarchical porous MOFs (BHP-MOFs) based on ZIF-8, Fe3O4 and three-dimensional graphene was successfully prepared for selective adsorption of Congo red (CR) and Malachite green (MG) from aqueous solutions. The surface morphology, physicochemical structure and composition of BHP-MOFs were characterized by SEM, TEM, FT-IR, XRD, Zeta potential, TGA and VSM analysis. The prepared BHP-MOFs exhibited a large specific surface area (225.522 m2/g), high pore volume (0.248 cm 3/g) and superparamagnetism, which made it an efficient adsorbent for fast adsorption of CR and MG. The adsorption kinetics studies showed that the adsorption mechanism of CR and MG followed the pseudo-second model and the adsorption process fitted well to Langmuir isotherm equation. Thermodynamic experiments have shown that the adsorption process is spontaneous and endothermic. The maximum adsorption capacities of CR and MG were 176.06 and 448.43 mg/g, respectively. Under the optimum conditions, BHP-MOFs were successfully used as magnetic adsorbents for the removal of CR and MG in environmental water and fruit juices, with removal efficiency ranged from 97.09% to 76.00%. The reusability of the BHP-MOFs was repeated with seven cycles and removal efficiency remained at 63.01% and 82.20% for CR and MG, respectively. It is proved that BHP-MOFs composite has excellent adsorption capacity for dyes and has a wide application prospect in practical applications.

Characterization and Dye Removal Application Using Initiated Carbon Originated from Rubber Seed Shell Biomass

The utilization of agricultural waste biomass presents an exciting substitute, established on its possibility to be switched into initiated carbon. In this research, initiated (activated) carbon (AC) was formulated from rubber seed shell biomass, infused with ammonium chloride at a temperature of 500 °C for 2 h. The activated carbon was characterized by its functional groups, thermal stability, surface morphology, and elemental identification by using FTIR, TGA/DTA, and SEM/EDAX. Additionally, the AC remediation strength was assessed with dye (Congo Red) under various parameters like dosage and pH; and the Langmuir and Freundlich adsorption isotherm prototypes were used to evaluate the utmost uptake (qmax) of Congo Red by the adsorptive material. The maximum dye adsorption capacity was achieved at 24.35 g/L and fits well in the Langmuir isotherm model. Therefore, the findings of this research reveal the possibility of utilizing rubber seed shell biomass as economical and competent raw ingredients to manufacture initiated carbon for wastewater treatment, to improve (increase) the water potability level.

Influence of Zinc and Humic Acids on Dye Adsorption from Water by Two Composts

Searching for alternative low-cost biosorbents for the removal of textile dyes from wastewater is currently an important subject of research. In this work, we have investigated how the presence of other contaminants in textile wastewaters can affect dye adsorption by biosorbents. We tested the adsorption of three dyes of different types: Basic Violet 10 (BV10), Acid Blue 113 (AB113) and Direct Blue 71 (DB71) by two different composts-municipal solid waste compost and pine bark compost-in the presence of Zn (5 mg L-1) or dissolved organic matter (100 mg humic acids L-1) in batch experiments. Dye adsorption capacity for both composts followed the following sequence: BV10 > AB113 > DB71. In general, dye sorption at the equilibrium was adequately described by the Freundlich model, but not always by the Langmuir model, which did not allow for the estimation of maximum retention capacities in all cases. In general, these were around 1 mg g-1 for DB71, 2 mg g-1 for AB113, and 40 mg g-1 for BV10. Municipal solid waste compost had slightly higher affinity than pine bark compost for the anionic dyes AB113 and DB71, whereas for the cationic dye BV10, pine bark compost presented a much higher adsorption capacity (41.7 mg g-1 versus 6.8 mg g-1). The presence of Zn or dissolved organic matter in the solutions at typical wastewater concentrations did not decrease the dye adsorption capacity of the composts. This result is positive both for the real application of composts to real textile wastewaters and for the validity of the results of biosorbent performance obtained with single-dye solutions.

A sulfonate-functionalized covalent organic framework for record-high adsorption and effective separation of organic dyes

The emerging global water crisis necessitates the development of solid adsorbents for the removal of organic pollutants from wastewater. Herein, we develop an anionic sulfonate-functionalized covalent organic framework (COF), termed TpStb-SO3Na, by the Schiff-base condensation between 2,4,6-triformylphloroglucinol (Tp) and 4,4′-diaminostilbene-2,2′-disulfonic acid (Stb-SO3H) under solvothermal conditions in the presence of sodium acetate. Thanks to the dense sulfonate groups in the periodic one-dimensional channels, the negatively charged TpStb-SO3Na displayed rapid kinetics (average ∼ 99% uptake in merely 10 min) and ultrahigh adsorption capacities for multiple cationic dyes including methylene blue (MB, 1078 mg g−1), crystal violet (CV, 1861 mg g−1), malachite green (MG, 5857 mg g−1) and janus green B (JGB, 1339 mg g−1) at room temperature. Noteworthy, the adsorption capacities of TpStb-SO3Na toward CV, MG, and JGB were the record-high values among the documented COFs, metal–organic frameworks (MOFs), and other benchmark adsorbents. In addition, the adsorption behaviors of MB, CV, MG, and JGB on TpStb-SO3Na obeyed the pseudo-second-order adsorption kinetic model. On the contrary, TpStb-SO3Na presented low adsorption capacity for anionic dyes like methyl orange (MO) and fluorescein sodium (FS), rendering it a promising sorbent for the separation of cationic and anionic dyes based on charge difference. Furthermore, TpStb-SO3Na was easily regenerated and reused for five cycles with no obvious loss in its adsorption performance. This work uncovers the vast potential of anionic COFs for the effective removal of organic dye pollutants in wastewater.

Adsorption of organic dyes onto nanozeolites: A machine learning study

Wastewater pollution with organic dyes has generated great concern in society due to the hazardous effects these contaminants pose to humans and aquatic life. In this view, the application of the adsorption process using nanoadsorbents has been a promising alternative due to the relatively low cost, high efficiency and simple operation. In addition, nanozeolites were highlighted in scientific literature due to their properties (surface area, porosity, ion exchange capacity, chemical and thermal stability), being useful for dye removal from wastewater. However, time and cost in experimental procedures are required to find optimal conditions for the adsorption of dyes onto these nanozeolites. Therefore, machine learning methods have emerged as a suitable tool for the prediction of the adsorption capacity of the nanoadsorbents in an efficient manner, being capable of recognizing patterns in the process and addressing the process feasibility. In this context, the present work aims to develop a machine learning (ML) study of the adsorption of organic dye onto nanozeolites and to identify the main variables that affect the adsorption capacity and removal of organic dye from wastewater. Thus, four ML algorithms (RF, LGB, XBG, and ANN) were tested as a regression model. This study revealed that XBG showed the best performance in comparison to the other models, being suitable in the prediction of adsorption capacities of nanozeolites for cationic dyes. Additionally, an exploratory analysis and hypothesis testing confirmed the great effect of the dye and nanoadsorbent concentrations, contact time and pH in the adsorption process. Therefore, the XGB proved to be capable to address the predicted adsorption capacity of nanozeolite from a relatively small dataset, being characterized as a starting point before experimental procedures and scale-up of wastewater treatment concerned with organic dye removal.

Statistical optimization of process parameters for ultrafast uptake of anionic azo dyes by efficient sorbent: Zn/Cu layered double hydroxide

The extensive use and release of synthetic dyes by various industries is a primary cause of contamination of water resources. Herein, the adsorption efficiency of Zn/Cu layered double hydroxide (LDH) was estimated for the uptake of a series of anionic dyes, out of which maximum removal efficiency was observed for Congo red (CR) dye. The effect of processing parameters, mainly adsorbate and adsorbent concentration, contact time, and pH on the adsorption capacity of CR dye, was analyzed by making use of response surface methodology (RSM). Based on the analysis of variance and experimental results, the modified quadratic regression model was found to be statistically acceptable. Further, the ultrafast removal efficiency of the synthesized material was observed with the maximum percentage removal of dye (>99%) within 4 min of contact time. In addition, batch adsorption experiments were conducted under the optimized reaction conditions for equilibrium and kinetic studies. Langmuir isotherm (R2 = 0.9965) and pseudo‐second‐order model (R2 = 1.0) were found to be the best‐fitted isotherm and kinetic models, respectively. Using Langmuir isotherm, the maximum adsorption capacity of the sorbent was calculated to be 167.22 mg/g. Furthermore, the adsorbent exhibited excellent regeneration capability and can be used efficiently for up to three cycles with >90% dye removal. The adsorption behavior of Zn/Cu LDH in different water matrices, that is, tap water, groundwater, and textile wastewater, was also investigated suggesting it to be an excellent adsorbent for real‐time applications.

Construction of alkalized MXene-supported CoFe2O4/CS composites with super-strong adsorption capacity to remove toxic dyes from aqueous solution

Owing to the unique surface microstructure, plentiful active sites and rich functional groups, two-dimensional transition metal carbide/nitride (MXene) is getting more and more attention in the field of pollutant removal. Now, we design a new magnetic adsorbent with CoFe2O4/chitosan (CS) composite supported onto alkalized MXene (alk-MXene) sheet using a facile hydrothermal and self-assembly technique. The structure and surface properties of the as-synthesized alk-MXene/CoFe2O4/CS composites are characterized by XRD, SEM, FTIR, TGA, BET and XPS. Batch experiments on adsorbing Congo Red (CR), Rhodamine B (RhB) and Malachite Green (MG) dyes are carried out, where the introduction of CoFe2O4/CS into alk-MXene can greatly enhance the adsorption capacity for cationic and anionic dyes. Notably, it is concluded that 24 h is a more suitable etching time to improve the adsorption performance of the composite during the synthesis process. An ultra-high adsorption capacity of S1 achieves up to 2095.9, 1333.9 and 537.6 mg g−1 for CR, RhB and MG dyes, respectively. The influence factors (etching time, pH values, contact time, initiate concentration and temperature) on the adsorption behaviors are discussed, where spontaneous and endothermic adsorption nature is confirmed. Analyses of the adsorption mechanism indicate that the synergistic effects of electrostatic interaction, π-π interaction and hydrogen bonding lead to superior adsorption abilities of the alk-MXene/CoFe2O4/CS composites. In a word, with the specific consideration on the advantages of MXene, CoFe2O4 and CS, this study offers a new track to obtain the MXene-based magnetic adsorbents with the simultaneous and high-efficiency removal of cationic and anionic dyes from the aqueous solutions.

Physicochemical and adsorption properties of guava leaves-activated carbon by hydrochloric acid on adsorption of methylene blue

This study emphasizes the biomass waste which is dried guava leaves as a natural low-cost adsorbent precursor of activated carbon for methylene blue (MB) dye solution due to its high abundance and availability in Malaysia. MB dyes which were largely consumed by the textiles industry pose several hazardous complications on human health without proper wastewater treatment. Thus, adsorption for water treatment serves as a cost-effective method to adsorb the dyes using low-cost adsorbent from dried leaves biomass. The dried leaves underwent chemical activation with hydrochloric acid (HCl) with ratio 1:1 and were carbonized at 700 °C for an hour and then neutralized for characterization and batch adsorption study. The physicochemical properties of guava leaves HCl activated carbon (GL-HAC), was characterized using ash content, moisture content, bulk density and iodine number. Percentage yield of GL-HAC was apparently high at 89.90 %. The GL-HAC reported had relatively low percentage of ash content and moisture content. The bulk density of the activated carbon was also low at 1.6 g/mL. The iodine number was calculated at 339.9 mg/g. The pHPZC for GL-HAC was obtained at 4.3 indicating that this activated carbon is efficient for the removal of MB dye with the pH solution above the pHPZC value. The results of the FTIR study shows that the functional groups of hydroxyl, amine, carbonyl, and carboxylic acid are present in GL-HAC. Batch adsorption studies were carried out to determine the most favourable condition for the activated carbon to adsorb methylene blue dye. The operating variables studied were adsorbent dosage, initial pH of solution, initial dye concentration and contact time. The results revealed that the effect of initial concentration and contact time were directly proportional to the adsorption capacity of MB dyes on the activated carbon. Thus, this study has demonstrated the potential of dried guava leaves as low-cost precursor of activated carbon for the removal of MB dyes.

Insights into Selective Removal by Dye Adsorption on Hydrophobic vs Multivalent Hydrophilic Functionalized MWCNTs.

Hydrophilic functionalized carbon nanotubes (MWCNT-COOH) were developed via hydrothermal glucose-coated carbonization, mixing MWCNTs with glucose in different weight ratios. Methyl violet (MV), methylene blue (MB), alizarin yellow (AY), and methyl orange (MO) were used as dye models for adsorption studies. Comparative dye adsorption capacity onto the pristine (MWCNT-raw) and functionalized (MWCNT-COOH-11) CNTs was evaluated in aqueous solution. These results revealed that MWCNT-raw is capable of adsorbing either anionic or cationic dyes. In contrast, an induced selective cation dye adsorption capacity is significantly enhanced on multivalent hydrophilic MWCNT-COOH, in comparison to a pristine surface. This ability can be tuned to the selective adsorption of cations over anionic dyes or between anionic mixtures from binary systems. An insight into adsorbate-adsorbent interactions shows that hierarchical supramolecular interactions dominate the adsorption processes, which is ascribed to the chemical modification by switching from a hydrophobic to a hydrophilic surface, dye charge, temperature, and potential matching multivalent acceptor/donor capacity between chemical groups in the adsorbent interface. The dye adsorption isotherm and thermodynamics on both surfaces were also studied. Changes in the Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were evaluated. Thermodynamic parameters were endothermic on MWCNT-raw, whereas the adsorption process on MWCNT-COOH-11 revealed that adsorption processes were spontaneous and exothermic, accompanied by a significant reduction of entropy values as a consequence of a multivalent effect. This approach provides an eco-friendly, low-cost alternative for the preparation of supramolecular nanoadsorbents with unprecedented properties to achieve remarkable selective adsorption independent of the presence of intrinsic porosity.

Novel 3D sphere-like β-In2S3/Biochar nanoflowers for remediation of dyes in single and binary systems and interpretation using statistical physical modeling

A novel 3D sphere-like β-In2S3/Biochar nanoflowers have been fabricated through the solvothermal process for effectively removing cationic malachite green and methylene blue dye in both single and binary systems. XRD, SEM, EDX, Elemental Mapping, TEM, BET, XPS, and FT-IR were used to characterize the physical and chemical properties of β-In2S3/Biochar. It was found that MG and MB had an adsorption capacity of 636.94 mg/g and 625.02 mg/g for β-In2S3/Biochar in single systems, while in binary systems, they had an adsorption capacity of 564.97 and 438.58 mg/g, respectively. The adsorption capacities in the multicomponent system were calculated using the extended Langmuir modeling, and the kinetic behavior of the adsorption in both systems followed pseudo-second-order kinetics. From the statistical physical modeling, the nD parameter values for MG adsorption obtained were 0.468, 0.498, and 0.612 at 298, 308, and 318 K, and the nD parameter values for MB adsorption were 0.63, 0.833, and 0.896, respectively in the single systems. These results showed that the dyes were adsorbed in a parallel orientation, and the adsorption followed a multi-interaction mechanism. The effect of water matrices and competing species, such as organic and inorganic compounds, are also investigated to find potential applications in real wastewater. In addition, the decrease in adsorption capacity for both dyes in the binary system was credited to the antagonistic effect, and the high efficiency and reusability of the fabricated β-In2S3/Biochar might provide new ideas for developing competent adsorbents to remove dyes from wastewater.

Functionalization of pine sawdust biochars with Mg/Al layered double hydroxides to enhance adsorption capacity of synthetic azo dyes: Adsorption mechanisms and reusability

This study determined that the adsorption of azo dyes, Methyl Orange (MO) and Sunset Yellow FCF (SYF), using the pristine pine sawdust biochar (PSB) and post-modified PSB with Mg/Al layered double hydroxides (PSB-LDHMgAl) was examined to offer valuable information into the differences in their adsorption mechanisms. Although a lower specific surface area of PSB-LDHMgAl (147.2 m2 g−1) than PSB (495.7 m2 g−1), LDHMgAl were successfully functionalized on the PSB surface through co-precipitation, which was highly related to the improvements of adsorption capacity of PSB-LDHMgAl toward MO and SYF. The MO and SYF adsorption kinetics by PSB and PSB-LDHMgAl were confirmed to the pseudo-second-order and considered chemisorption. The adsorption capacity of MO and SYF adsorbed onto PSB-LDHMgAl (MO = 21.8 mg g−1, SYF = 23.6 mg g−1) were significantly higher than that of PSB (MO = 2.2 mg g−1, SYF = 1.6 mg g−1). The adsorption isotherms of MO and SYF by PSB were well fitted by Freundlich isotherm, whereas the MO and SYF via PSB-LDHMgAl were by Langmuir isotherm. Even after 3 adsorption-desorption cycles using desorbents, the PSB-LDHMgAl remained excellent reusability (reuse efficiency: >81.2%). These findings suggest that post-modification with LDHMgAl might accelerate the adsorption performance (i.e., electrostatic interaction) of azo dyes to PSB in water.

Dried Leaves Powder of Adiantum capillus-veneris as an Efficient Biosorbent for Hazardous Crystal Violet Dye from Water Resources

The dyeing industry uses many chemicals and dyes. After the dying process is completed, they release a significant amount of dyes in wastewater. The dyes’ color emissions are extremely poisonous and dangerous for aquatic and terrestrial life. Due to the toxic nature of dyes, the current study was carried out to evaluate whether it would be effective to employ an adsorption procedure with leaves from the Adiantum capillus-veneris plant as an adsorbent to remove commonly used textile dyes from an aqueous dye solution and wastewater. The effect of pH, concentration, time and the adsorbent dose on the adsorption process was studied in order to determine the maximum adsorption under ideal conditions. The selected pH was 3; the optimum concentration was 30 ppm with a contact time of 90 min and the optimized adsorbent dose was 60 mg. The absorbent under study showed excellent results when compared with commercial adsorbents i.e., animal charcoal and silica gel. The leaves of the Adiantum capillus-veneris plant revealed a maximum removal of 90.36 percent crystal violet dye (adsorption capacity (Qe) 9.05 mg/g) without any treatment to activate or alter the surface chemistry of the biosorbent. Its effectiveness was also tested with water gathered from several sources, including canal water, tap water, distilled water, and saline water, to determine whether it was practical. In both the canal and the tap water, the adsorbent displayed good removal efficiency. From the results of the current study, it can be inferred that the leaves of the Adiantum capillus-veneris plant are a reasonably priced biosorbent that can be used to remove toxic dyes from wastewater to protect water bodies from toxic pollution and can be used to treat industrial wastewater directly.

Aminated Covalent Organic Polymers for Anionic Dye Adsorption in Aqueous Systems

Aminated covalent organic polymer (ACOP) was synthesized through a catalyst-free Schiff base reaction involving terephthalaldehyde and melamine, and the prepared ACOP was used for the adsorption of anionic dyes. The prepared ACOP possessed a high specific surface area (582.07 m2/g) with an average pore size of 88.71 Å. Its point of zero charge was determined as pH 8.26. Anionic dye molecules, methyl orange (MO) and orange G (OG), were used to evaluate the dye adsorption efficiency of the prepared ACOP, and it was found that they were adsorbed rapidly on ACOP within 1 min. The maximum adsorption capacities (qm) of the prepared ACOP for MO and OG were 351.9 and 227.9 mg/g, respectively. Furthermore, the results of dye adsorption as a function of the initial pH and presence/absence of cationic dye (methylene blue; MB) revealed that dye adsorption on ACOP proceeded through charge–charge and π–π interactions. The presence of MB along with MO and OG enhanced the dye adsorption capacity because of the synergistic effect of the positively charged quaternized nitrogen atoms in the prepared ACOP. The dye adsorption mechanism was further investigated using Fourier transform infrared (FT-IR) analysis and X-ray photoelectron spectrometry (XPS). The ACOP adsorbent prepared herein using a facile catalyst-free reaction offers rapid adsorption with a high adsorption efficiency over a wide pH range and in the presence of cationic dye. For these reasons, it can be used for environmental remediation, especially in aqueous systems.

The effect of sintering temperature on the properties of the BiOCl films for potential application in DSSC

In this work, BiOCl films were obtained by tape casting using BiOCl powders synthesized by the co-precipitation method. The effect of the film's sintering temperature (300 °C–600 °C) on the morphology, chemical composition, crystalline phases and optical characteristics was studied. The obtained BiOCl powders showed a flake-like morphology, a tetragonal crystalline structure without secondary phases and a wide band gap of 3.53 eV. For BiOCl films, results indicated that as the sintering temperature increased the flake-like shaped particles changed to rectangular ones while the amount of chlorine in the films decreased. A phase transition from tetragonal BiOCl to monoclinic Bi24O31Cl10 was also observed as the sintering temperature increased. Consequently, optical studies revealed that the band gap of BiOCl films decreased from 3.03 eV to 2.82 eV. FTIR analysis demonstrated that the organic groups were removed from the films only for sintering temperatures above 400 °C. The Rhodamine B dye adsorption capacity of BiOCl films decreased with increasing sintering temperature. The results obtained allow us to conclude that BiOCl films are suitable for use in DSSC when the sintering temperature is in the range of 400–500 °C.

Schottky construction of bimetallic Au-Cu alloy@TiO2 hollow nanoboxes embedded optical switch for enhancing photocatalytic and selective adsorption activities via one-pot deposition-precipitation strategy

One-pot soft integration strategy based on wet chemistry via a simple in situ deposition-precipitation approach has been developed to fabricate series of bimetallic Au-Cu alloy@TiO2 hollow nanoboxes (THB) embedded optical switch. The bimetallic Au-Cu alloys were embedded into the nanodevice through Schottky junctions. This embedded optical switch could exhibit excellent photocatalytic performance. Under simulated sunlight irradiation, Au-Cu4:3 @THB nanodevice exhibited the photodegradation rate of RhB was of 99.4 % in 150 min, which was 3.0 times higher than that of THB. The oxidation rate of NO reached 27.0 %, 2.3 times that of THB. The enhanced photocatalytic activity could mainly be attributed to Au-Cu alloy SPR effects; the photoreactivity of the nanodevice was greatly improved after modification with bimetallic Au-Cu. Under dark conditions, the RhB adsorption rate of bimetallic Au-Cu4:3 @THB nanodevice reached 98.6 %, which was 6.1 times higher than that of THB. As the adsorption effect test of mixed dyes (MB/MO and RhB/MO), after 5 h of adsorption, the adsorption capacity of cationic dyes was 3.1 times that of anionic dyes, it was concluded that the bimetallic Au-Cu4:3 @THB optical switch had an excellent selective adsorption effect. This was due to the large surface area and mesoporous structure of the adsorbent, good electron transport structure, and the formation of a galvanic cell after adding dyes. This research provides a promising catalytic material with optical switch for environmental restoration and protection. It has broad application prospects in photocatalytic degradation, photocatalytic oxidation and adsorption of organic pollutants.

An investigation on the influence of highly acidic media on the microstructural stability and dye adsorption performance of UiO-66

Stability of UiO-66 in 1 M HCl for different exposure times up to 15 days was investigated by employing various characterization techniques such as XRD, FESEM, TEM, TGA, and nitrogen adsorption/desorption. The lower surface area, smaller pore size, and slightly lower thermal stability indicated that the UiO-66 structure experienced a partial breakdown, but could maintain its main structure and showed acceptable stability. In addition, the exposure to the HCl solution added to the missing-linker defects in the structure of UiO-66. The adsorptive performance of HCl-aged UiO-66 nanoparticles towards anionic methyl orange (MO) dye was then evaluated. Compared to as-synthesized UiO-66, maximum dye adsorption capacity of HCl-aged UiO-66 towards MO exhibited over 60 % loss for 15 days aged UiO-66. Moreover, negative charges took over the positive surface charge of as-synthesized UiO-66 upon HCl aging. Therefore, the selective adsorption analysis showed that while neat UiO-66 adsorbs MO selectively over cationic dyes, acid-aged samples have a higher affinity towards cationic dyes. The adsorption kinetics of pristine and acid-aged UiO-66 particles were well outlined by pseudo-second-order, and isotherm studies demonstrated that the adsorption could be delineated well by the Langmuir and Freundlich model, inferring that adsorption takes place both multilayer and monolayer in parts.