Adsorption Of Dye Molecules Research Articles

Enhanced removal of methylene blue dye in aqueous solution using eco-friendly Fe(III)–montmorillonite

We have explored the highly efficient and environmentally benign clay mineral, Fe(III)–montmorillonite (Fe(III)–Mt), for methylene blue (MB) dye removal in aqueous solution. The Fe(III)–Mt was interacted with MB dye solution at different pH, temperature and solid-to-liquid ratio. The concentration of MB dye removal was estimated from its optical density at λmax = 665 nm using UV-Vis spectrophotometer. The MB dye molecules removal was rapid at basic pH and increases with temperature up to 40 °C. A complete reduction (100%) was occurred in about 7 min at pH 7 & 10 while at pH 3 in about 10 min. The time taken for complete reduction at 0 °C, RT (30 °C), and 40 °C are 10, 7 and 5 min respectively. The removalfollowed by adsorption of dye molecules on the spent clay mineral was evident from FESEM/EDX analysis. More importantly, Fe(III)–Mt could be separated and retrieved easily after the reaction by centrifugation from the degraded MB dye solution. This study reveals that Fe(III)–Mt has the potential to be used as reductant/adsorbent to remove cationic dye molecules effectively and rapidly from drinking water and large scale of industrial wastewater.

Removal of dye molecules from aqueous solution by carbon nanotubes and carbon nanotube functional groups: critical review

Scheme for the adsorption of dye molecules by CNTs and CNT functionality.

Performance Enhancement of Dye-Sensitized Solar Cells Using a Natural Sensitizer

Dye-sensitized solar cells (DSSCs) based on natural sensitizers have become a topic of significant research because of their urgency and importance in the energy conversion field and the following advantages: ease of fabrication, low-cost solar cell, and usage of nontoxic materials. In this study, the chlorophyll extracted from papaya leaves was used as a natural sensitizer. Dye molecules were adsorbed by TiO2 nanoparticle surfaces when submerged in the dye solution for 24 h. The concentration of the dye solution influences both the amount of dye loading and the DSSC performance. The amount of adsorbed dye molecules by TiO2 nanoparticle was calculated using a desorption method. As the concentration of dye solution was increased, the dye loading capacity and power conversion efficiency increased. Above 90 mM dye solution concentration, however, the DSSC efficiency decreased because dye precipitated on the TiO2 nanostructure. These characteristics of DSSCs were analyzed under the irradiation of 100 mW/cm2. The best performance of DSSCs was obtained at 90 mM dye solution, with the values of Voc, Jsc, FF, and efficiency of DSSCs being 0.561 V, 0.402 mA/cm2, 41.65%, and 0.094%, respectively.

Dual Functional Polymer Interlayer for Facilitating Ion Transport and Reducing Charge Recombination in Dye-Sensitized Solar Cells.

Dye-sensitized solar cells (DSSCs) present low-cost alternatives to conventional wafer-based inorganic solar cells and have remarkable power conversion efficiency. To further enhance performance, we propose a new DSSC architecture with a novel dual-functional polymer interlayer that prevents charge recombination and facilitates ionic conduction, as well as maintaining dye loading and regeneration. Poly(vinylidene fluoride-trifluoroethylene) (p(VDF-TrFE)) was coated on the outside of a dye-sensitized TiO2 photoanode by a simple solution process that did not sacrifice the amount of adsorbed dye molecules in the DSSC device. Light-intensity-modulated photocurrent and photovoltage spectroscopy revealed that the proposed p(VDF-TrFE)-coated anode yielded longer electron lifetime and improved the injection of photogenerated electrons into TiO2, thereby reducing the electron transport time. Comparative cyclic voltammetry and UV-visible absorption spectroscopy based on a ferrocene-ferrocenium external standard material demonstrated that p(VDF-TrFE) enhanced the power conversion efficiency from 7.67% to 9.11%. This dual functional p(VDF-TrFE) interlayer is a promising candidate for improving the performance of DSSCs and can also be employed in other electrochemical devices.

Selective Adsorption and Separation through Molecular Filtration by Hyperbranched Poly(ether amine)/Carbon Nanotube Ultrathin Membranes.

In response to the increasing public awareness of serious dye-contained wastewater contamination, we herein fabricated a novel anthracene-containing hyperbranched poly(ether amine) (hPEA-AN)/carbon nanotube (CNT) ultrathin membrane (UTM), which combined both the merits of the conventional dye adsorption strategy and membrane filtration process, to implement efficient selective adsorption of dye molecules and also the separation of dye mixtures by molecular filtration. Taking advantage of the π-π stacking interactions between anthracene and CNT sidewalls and hydrophobic interactions, CNTs were coated tightly with hPEA-AN to form the hPEA-AN@CNT complex, which can be well-dispersed very stably in water. The formation of the hPEA-AN@CNT complex was confirmed using X-ray photoelectron spectroscopy, Raman spectra, fluorescence spectra, and thermogravimetric analysis. Meanwhile, a simple filtration process was applied to prepare hPEA-AN@CNT UTMs with a thickness of 1.5 μm, which can be further cross-linked through photodimerization of anthracene moieties. The UTMs represented selective adsorption behaviors toward hydrophilic dyes even with similar backbones and the same charge states, namely, they showed high adsorption capacities (Qeq) toward eosin B, erythrosin B (ETB), 4',5'-dibromofluorescein, and Evans blue (EVB) dyes up to 300 μmol/g while showing low adsorption capacities toward calcein (Cal), methyl red, and Ponceau S dyes. On the basis of this unique selective adsorption, molecular filtration was then realized toward mixed ETB/Cal and EVB/Cal dyes, with a separation efficiency of up to 100% and regeneration without an obvious efficiency decrease.

Quantification of Adsorption of Azo Dye Molecules on Graphene Oxide Using Optical Spectroscopy

The presence of azo dye molecules in effluents is a source of water pollution and an environmental hazard. Thus, it is very important to separate out such dye molecules. We have investigated the use of graphene oxide (GO) for the purification of dye-contaminated water. The adsorption efficiency of GO in the degradation of azo dye molecules and the interaction mechanism has been estimated using Ultra Violet-Visible absorption spectroscopy. The charge on the dye molecules along with steric hinderance due to their molecular structure is understood to be detrimental in the adsorption and removal of such dyes. Spectroscopic studies suggest that GO can be used as a potential candidate for efficient removal of cationic azo-dye molecules by adsorption.

Coordination polymers with 1,3-bis(1-imidazolyl)-5-(imidazol-1- ylmethyl)benzene and biphenyl-4,4′-dicarboxylate ligands: Selective adsorption of gas and dye molecules

An exploration of reactions of 1, 3-bis(1-imidazolyl)-5-(imidazol-1-ylmethyl)benzene (biimb) and biphenyl-4, 4′-dicarboxylic acid (H2BPDC) with Co(II) and Mn(II) salts yielded four new coordination polymers [Co(biimb)(BPDC)(H2O)2]·DMA·10H2O (1), [Co(biimb)(BPDC)] (2), [Mn3(biimb)(BPDC)3(H2O)]·2DMF·0.7H2O (3) and [Mn(biimb)2(BPDC)]·2H2O (4) (DMA = N, N-dimethylacetamide, DMF = N, N-dimethylformamide). 1 has pillar-layered 3D structure without interpenetration and can selectively adsorb methyl orange dye molecules, while 2 is an interesting 5-fold interpenetrating 3D framework. 3 is a 3D net with [Mn3(COO)6] sub-units linked by BPDC2− and biimb ligands. Magnetic investigation revealed that there are antiferromagnetic interactions within the trinuclear sub-units in 3. In the case of 4, the coordination of Mn(II) with biimb gives 1D chain, which is further linked by BPDC2− resulting in formation of a 2D network. The structure diversity of 1–4 implies that the varied coordination modes of BPDC2− have remarkable impact in determining the structure and topology of the complexes.

Multifunctional Metal-Organic Frameworks with Fluorescent Sensing and Selective Adsorption Properties.

Metal-organic frameworks (MOFs) have attracted great attention in the past years due to their diverse structures as well as interesting properties. However, MOFs with multifunctionality are still challenging. Under solvothermal conditions, reactions of 1,3,5-tris(1-imidazolyl)benzene (tib) and 4,4',4″-benzene-1,3,5-triyl-tribenzoic acid (H3BTB) with Cd(II) salt give rise to two novel MOFs [Cd3(tib)2(BTB)2]·3DEF·4.5H2O (1) and [Cd3(tib)2(BTB)2(DMA)2(H2O)2]·2DMA·8H2O (2) (DEF = N,N-diethylformamide, DMA = N,N-dimethylacetamide) with three-dimensional framework structures. It is fascinating that 1 and 2 not only show unique selectivity for detection of acetone through fluorescence quenching mechanism but also exhibit selective adsorption of gas (CO2 over N2 at 298 K) and dye (methyl orange) molecules.

Ni doped ZnS nanoparticles as photocatalyst: Can mixed phase be optimized for better performance?

ZnS nanoparticles with Ni2+ as dopant ions, have been synthesized and characterized by X-ray Diffraction, Inductive Coupled Plasma-Atomic Emission spectroscopy and Transmission Electron Microscopy. UV–vis absorption and photoluminescence spectroscopies were employed to investigate different photo-processes occurring on exposure to UV–vis light. The synthesized NPs were evaluated as photocatalyst for the removal of the color of aqueous solution of rhodamine B (RhB) dye as test solution under 250W High Pressure Mercury Vapor lamp. Mott-Schottky, Cyclic Voltammetery, and hot-probe measurements suggest the change in the ‘type’ of semiconductor from n to p as well as phase change (cubic to wurtzite) take place on increasing the amount of dopant to 10%. The newly appeared phase forms ‘local pockets’ in an overall cubic matrix of ZnS NPs, this way created defects at the local grain boundaries of dissimilar phases. These provide active sites for the adsorption of dye molecules, in turn, improve the efficiency of the material as photocatalyst.

Adsorption of Dye Molecules on Single Crystalline Semiconductor Surfaces: An Electrochemical Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy Study

Adsorption of dye molecules on semiconductor surfaces dictates the interaction at and thus the electron transfer across the interface, which is a crucial issue in dye-sensitized solar cells (DSSCs). However, despite that surface enhanced Raman spectroscopy (SERS) has been employed to study the interface, information obtained so far is gathered from surfaces of irregularly arranged nanoparticles, which places complexities for precise attribution of adsorption configuration of dye molecules. Herein, we employ single crystalline rutile TiO2(110) for Raman spectroscopic investigation of TiO2–dye interfaces under electrochemical control by utilizing the enhancement of Au@SiO2 core–shell nanoparticles. FD-TD simulation is performed to evaluate the localized electromagnetic field (EM) created by the core–shell nanoparticles while Mott–Schottky measurements are used to determine the band structure of the semiconductor electrode. Comparative investigations are carried out on nanoporous P25 TiO2 electrodes. The potential-dependent Raman shift of ν(N═C═S) suggests that the binding of the SCN group of N719 to the TiO2 surface is the intrinsic nature of the TiO2–N719 interaction, after removing the possible bonding complexity by surface roughness. Nevertheless, hydrogen bonding between COOH and the TiO2 appears to be more favorable on the atomic flat rutile TiO2(110) surface than on the surface of nanoporous P25 nanoparticle as revealed by the stronger Raman shift of ν(C═O) (COOH) on the former. Electrochemical SERS (EC-SERS) results show that photoinduced charge transfer (PICT) occurs for both the P25 and rutile(110) TiO2 surfaces, and the potential to achieve PICT resonance depends on the band structure of the semiconductor. Our work demonstrates that EC-SERS can be applied to study the single crystalline semiconductor–molecule interfaces using core–shell based surface plasmonic resonance (SPR) enhancement strategy, which would promote fundamental investigations on interfaces of photovoltaic and photocatalytic systems.

Ultrasound-assisted removal of Acid Red 17 using nanosized Fe3O4-loaded coffee waste hydrochar

The Fe3O4-loaded coffee waste hydrochar (Fe3O4-CHC) was synthesized using a simple precipitation method. The as-prepared adsorbent was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FT-IR). The EDX analysis indicated the presence of Fe in the structure of Fe3O4-CHC. The specific surface area of hydrochar increased from 17.2 to 34.7m2/g after loading of Fe3O4 nanoparticles onto it. The prepared Fe3O4-CHC was used for removal of Acid Red 17 (AR17) through ultrasound-assisted process. The decolorization efficiency decreased from 100 to 74% with the increase in initial dye concentration and from 100 to 91 and 85% in the presence of NaCl and Na2SO4, respectively. The synthesized Fe3O4-CHC exhibited good stability in the repeated adsorption-desorption cycles. The high correlation coefficient (R2=0.997) obtained from Langmuir model indicated that physical and monolayer adsorption of dye molecules occurred on the Fe3O4-CHC surface. Furthermore, the by-products generated through the degradation of AR17 was identified by gas chromatography–mass spectrometry analysis.

Understanding photoelectrochemical degradation of methyl orange using TiO2/Ti mesh as photocathode under visible light

A better understanding of photoelectrochemical degradation of methyl orange (MO) on TiO2/Ti mesh photocathode is extremely important for improving the efficiency of dye degradation technology. The influence of morphology, crystallinity, anatase-rutile ratio and the active surface area of the photocathode have been analyzed using atomic force microscope (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV, EIS studies along with product analysis reveal that, the photocathode calcined at 550°C, having rutile:anatase ratio of 20:80, shows highest dye degradation because of favored catalytst morphology, enhanced adsorption of dye molecules and smallest charge-transfer resistance. The product analysis reveals that MO is degraded into simple and useful components such as hydrazine and acetic acid hydrazide.

Fabrication of a TiO2-P25/(TiO2-P25+TiO2 nanotubes) junction for dye sensitized solar cells

The dye sensitized solar cell (DSSC), which converts solar light into electric energy, is expected to be a promising renewable energy source for today's world. In this work, dye sensitized solar cells, one containing a single layer and one containing a double layer, were fabricated. In the double layer DSSC structure, the under-layer was TiO2-P25 film, and the top layer consisted of a mixture of TiO2-P25 and TiO2 nanotubes. The results indicated that the efficiency of the DSSC with the double layer structure was a significant improvement in comparison to the DSSC consisting of only a single film layer. The addition of TiO2-P25 in the top layer caused an improvement in the adsorption of dye molecules on the film rather than on the TiO2 nanotubes only. The presence of the TiO2 nanotubes together with TiO2-P25 in the top layer revealed the enhancement in harvesting the incident light and an improvement of electron transport through the film.

Removal of methylene blue from aqueous media using activated carbon web

Activated carbon web is prepared by controlled pyrolysis of acrylic fibrous waste under the layer of charcoal using physical activation in high-temperature furnace. The carbonization was carried out at 1200 °C under different heating rate (i.e. 150 to 450 °C h−1) with different holding time (i.e. 0 to 60 min) to decide optimum pyrolysis parameters. The heating rate of 300 °C h−1 with no holding time revealed higher specific surface area of 280 m2 g−1. The prepared activated carbon web was later employed as adsorbent for removal of methylene blue from aqueous media. The effect of initial dye concentration, adsorbent dosage, stirring speed, and pH of solution was studied. The obtained results were later compared with adsorption isotherms (i.e. Langmuir and Freundlich). The Freundlich model was found to fit closely with results due to heterogeneous adsorption of dye molecules. Finally, virgin activated carbon and dye adsorbed activated carbon were tested for desorption behavior using differential scanning calorimetry and thermo gravimetric analysis. The significant reduction in desorption enthalpy from 172.46 to 52.43 J g−1 is attributed to less adsorption energies of dye molecules on the surface of activated carbon due to nonhomogeneous distribution of active sites.

Oxidative power of aqueous non-irradiated TiO2-H2O2 suspensions: Methylene blue degradation and the role of reactive oxygen species

In the present study, the degradation of methylene blue in non-irradiated TiO2-H2O2 suspensions was investigated. Five commercially available catalysts were characterized (BET surface area, zeta potential, hydrodynamic diameter) and their oxidative power was assessed by means of the degradation of methylene blue. A subsequent EPR study was made to verify and identify potential oxidative radicals. The results showed that all suspensions could degrade methylene blue significantly stronger compared to hydrogen peroxide alone. A broad variation between the different catalysts in their capability to adsorb dye molecules was found which was essential for decomposition of methylene blue in darkness. The highest degradation rate of all samples was found for Degussa P25 at neutral pH. EPR studies of this sample verified the presence of oxygen centred radicals namely hydroxyl (OH) and superoxide radicals (O2−/OOH). Non-irradiated TiO2-H2O2 systems show great potential not only in dye removal applications but also in the field of disinfection where low concentrations of hydrogen peroxide are required and irradiation may not be feasible.

Carrier-Free and Low-Temperature Ultradeep Dyeing of Poly(ethylene terephthalate) Copolyester Modified with Sodium-5-sulfo-bis(hydroxyethyl)-isophthalate and 2-Methyl-1,3-propanediol

To obtain sufficient dyeability, dyeing of poly(ethylene terephthalate) fabrics must be performed at high temperature and high pressure or by using a no-eco-friendly carrier at atmospheric pressure, which implies large energy consumption and environmental contamination. In order to improve the sustainability of the dyeing process, a carrier-free and low-temperature dyeing procedure was developed for the poly(ethylene terephthalate) copolyester (MCDP) incorporated with sodium-5-sulfo-bis(hydroxyethyl)-isophthalate (SIP) and 2-methyl-1,3-propanediol (MPD). The results obtained from cationic dyeing at optimized conditions show an outstanding dye utilization (99.0%) with MCDP, which is much higher than that of the conventional SIP-modified copolyester. Meanwhile, the introduction of SIP and MPD contents ensures the large adsorption and fast diffusion of dye molecules into the amorphous region of fibers, allowing an efficient and deep disperse dyeing of polyester fabrics under atmosphere in the absence of carr...

Synthesis of mesoporous carbon nanospheres for highly efficient adsorption of bulky dye molecules

A facile synthesis route to the mesoporous carbon nanospheres (MCNs) with tunable size has been prepared via silica cooperative self-assembly using resorcinol as a polymer precursor, tetraethyl orthosilicate as an inorganic precursor, and hexadecyl trimethyl ammonium bromide and triblock copolymer Pluronic F127 as a co-template. The sizes of carbon nanospheres are uniform and easily controlled in the range of 80–170 nm by varying the content of F127. The MCNs exhibit promising properties for adsorption of bulky dye molecules due to their high specific surface area (1481 m2 g−1), large pore volume (2.55 cm3 g−1), and dual mesoporous texture (4.1 and 24.1 nm). Kinetic and isothermal analysis demonstrates the strong interactions between dye molecules and the MCNs. Furthermore, the regenerated MCNs show quite stable adsorption performance, which can be reused for dye removal. The results demonstrated in this work should give a useful enlightenment for the design of adsorbent to remove organic pollutant in wastewater.

Adsorption of different dyes from aqueous solution using Si-MCM-41 having very high surface area

Adsorption characteristics of four different dyes Safranin O (cationic), Neutral Red (neutral), Congo Red (anionic) and Reactive Red 2 (anionic) on Si-MCM-41 material having very high surface area are reported. The surface morphology of Si-MCM-41 material before and after adsorbing dye molecules are characterised by FTIR, HRXRD, nitrogen adsorption–desorption isotherms, FESEM, and HRTEM. The adsorption capacities of Si-MCM-41 for the dyes followed a decreasing order of NR > SF > CR > RR2. The adsorption kinetics, isotherm and thermodynamic parameters are investigated in detail for these dyes using calcined Si-MCM-41. The kinetics and isotherm data showed that both SF and NR adsorb more rapidly than CR and RR2, in accordance with pseudo-second-order kinetics model as well as intraparticle diffusion kinetics model and Langmuir adsorption isotherm model respectively. The thermodynamic data suggest that the dye uptake process is spontaneous. The high adsorption capacities of dyes on Si-MCM-41 (qm = 275.5 mg g−1 for SF, qm = 288.2 mg g−1 for NR) is explained on the basis of electrostatic interactions as well as H-bonding interactions between adsorbent and adsorbate molecules. Good regeneration capacity is another important aspect of the material that makes it potent for the uptake of dyes from aqueous solution.

입상 활성탄에 의한 Rhodamin-B의 흡착 열역학, 동력학 및 등량 흡착열에 관한 연구

The adsorption of Rhodamine-B dye using granular activated carbon from aqueous solution was investigated. Adsorption experiments were carried out as a function of the adsorbent dose, pH initial concentration, contact time and temperature. The equilibrium adsorption data showed a good fit to Langmuir isotherm model. Based on the estimated Langmuir separation factor (RL = 0.0164~0.0314), our adsorption process could be employed as an effective treatment method. The kinetics of adsorption followed the pseudo first order model. Also, the negative values of Gibbs free energy (-4.51~-13.44 kJ/mol) and positive enthalpy (128.97 kJ/mol) indicated that the adsorption was spontaneous and endothermic process. The isosteric heat of adsorption increased with increase in the surface loading indicating lateral interactions between the adsorbed dye molecules.

Shape induced (spherical, sheets and rods) optical and magnetic properties of CdS nanostructures with enhanced photocatalytic activity for photodegradation of methylene blue dye under ultra-violet irradiation

CdS nanostructures of different shapes such as, nanoparticles (NPs), nanosheets (NS) and nanorods (NRs) have been synthesized by one step chemical solvothermal method. The synthesized samples were characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, UV–visible (UV-VIS) spectroscopy, Raman spectroscopy (RS) and vibrating sample magnetometer (VSM) techniques. The effect of shape on optical and magnetic properties of CdS nanostructures was studied. The optical band gap and emission spectra are found to be shape dependent. CdS NRs were found to have high saturation (Ms) magnetization than that of CdS NPs and NS. The role of shape on photocatalytic performance of CdS NPs, NS and NRs was investigated by monitoring the photodegradation of methylene blue (MB) dye under the UV irradiation of wavelength 365 nm. The lower recombination rate of electron-hole pairs and larger surface area as reactive facets for adsorption of MB dye molecules in CdS NS are mainly lead to the better photocatalytic performance of CdS NS compared to NPs and NRs.