Adsorption Of Dye Molecules Research Articles

Preparation and characterisation of montmorillonite-Fe3+ (MMT-Fe3+) nanoclay mineral for crystal violet (CV) removal from aqueous solutions

Montmorillonite-Fe3+ (MMT-Fe3+) nanoclay mineral was successfully prepared using a ferric chloride precursor. The prepared sample was characterized using IR, XRD, BET and SEM-EDX. We have explored the highly efficient and environmentally benign MMT-Fe3+ for adsorption of Crystal Violet (CV) dye from aqueous solution under ambient conditions. The MMT-Fe3+ was interacted with CV dye solution at different pH, temperature and solid-to-liquid ratio. The concentration of CV dye removal was estimated from its optical density at λmax = 590 nm using UV–Vis spectrophotometer. The CV dye 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 and 10 while at pH 3 in about 10 min. The time taken for complete reduction at 0, 30 and 40 °C are 10, 7 and 5 min respectively. The removal followed by adsorption of dye molecules on the spent nanoclay mineral was evident from SEM/EDX analysis. More importantly, MMT-Fe3+ could be separated and retrieved easily after the reaction by centrifugation from the degraded CV dye solution. The experimental results of CV dye removal from MMT-Fe3+ follows the pseudo first order kinetics. This study reveals that MMT-Fe3+ has the potential to be used as reductant/adsorbant to remove cationic pollutants effectively and rapidly from drinking water and large scale of industrial wastewater.

Influence of TiO2 surface defects on the adsorption of N719 dye molecules

Surface defects influence the dye adsorption on TiO2 used as a substrate in dye-sensitized solar cells (DSSCs).

Study on the Adsorption of Methylene Blue from Dye Wastewater by Humulus Japonicus Leaves

This paper took the objective of preparing high-performance, low-cost biological adsorbent for printing and dyeing wastewater, and the adsorption experiment of dyestuff wastewater with high chromaticity and high biodegradability was studied. The Methylene Blue was adsorbed by the prepared Humulus Japonicus Leaves (HJ), the effects of adsorption time, pH, dosage of adsorbent, initial Methylene Blue concentration and temperature on the adsorption process were investigated, and the adsorption mechanism was described by adsorption isotherm, adsorption thermodynamics and adsorption kinetics, and the results showed that: when HJ was added 0.15g and ph was 7, the temperature was 30°C (303K), adsorption was carried out for 20min, simulated dye wastewater, adsorption efficiency of Methylene Blue of 100mg/l were excellent, adsorption rate reached up to 92%, the equilibrium adsorption rate was positively correlated with the initial concentration of CV dye. Humulus leaves adsorption CV Gibbs free energy of ΔG<0, ΔH>0, ΔS>0 showed spontaneous adsorption process, the adsorption process Methylene Blu was more suitable for the Freundlich isothermal adsorption equation, the adsorption kinetics accorded with the quasi two level kinetic model, the adsorption of the Methylene Blue dye molecule by the HJ was chemically adsorbed as the rate control step, the Methylene Blue molecule was mainly adsorbed on the surface of the Humulus leaves; the model of internal diffusion kinetics showed that there was membrane diffusion and internal diffusion of the HJ in the process of Methylene Blue adsorption. The experimental results showed that HJ as adsorbent can effectively remove Methylene Blue from dye wastewater, and the research results provide a new method and idea for biological treatment of dye wastewater.

Applicability of gypsum in selective removal of anionic dye molecules from aqueous medium

This article describes how selectively anionic organic molecules could be removed from aqueous medium using naturally available gypsum (GS) adsorbent. Gypsum (CaSO4.2H2O) shows strong interactions with anionic dye molecules while it dos not show any affinity towards cationic dye molecules. We have shown the removal efficiency of gypsum taking chlorazole yellow (anionic dye) and methylene blue (cationic dye) as examples of adsorbates. The GS has been to be even more effective than activated carbon in attaining chlorazole yellow (CY) removal. Three well-known kinetic equations e.g. pseudo-first-order, pseudo-second order and intraparticle diffusion were exploited to interpret the experimental data. Results show best fitting with second order kinetic process with excellent regression coefficient (r2 = 0.99) for the adsorption process. The equilibrium data were analyzed exploiting some adsorption isotherm models. It was apparent that the Freundlich isotherm model superbly fitted for CY dye adsorption process. And the maximum adsorption capacity, Qm, was obtained as 12.85 mg g−1 at room temperature. The negative values of Gibb’s free energy change (ΔGo) suggests that the CY dye molecule adsorption process is spontaneous in nature. Moreover, negative enthalpy change (ΔHo) indicates the exothermic nature of the adsorption process. The outcome could be exploited where anionic organic molecules are required to be separated, selectively.

Influence of Ni (II) oxime complex coupled with the combination of diverse sized ZnO nanoparticles on Photovoltaic Performance

The one side selective synthesis of quinoline carboxylic acid oxime complex was carried out successfully. The as-prepared quinoline carboxylic acid oxime complex was complexed with nickel (II) salts to form nickel (II) oxime complex. These complexes were further adsorbed onto ZnO films containing ZnO nanoparticles of various sizes. ZnO films containing a diverse proportion of ZnO nanoparticles were investigated to enhance the photovoltaic efficiency of the dye-sensitized solar cell. The as-synthesized complex was characterized by scanning electron microscopy (SEM), Ultra violet visible spectroscopy (UV-vis), Fourier Transform Infrared Spectroscopy (FT-IR) spectroscopy, 1Hydrogen Nuclear magnetic resonance spectroscopy (1HNMR), Liquid chromatography coupled with mass spectrometry (LC-MR), Brunauer–Emmett–Teller (BET), and Attenuated total reflection Infra-red spectroscopy (ATR-IR). The combination of large and small ZnO nanoparticles has significantly improves the photovoltaic efficiency. The optimum mixing ratio for the best performance (0.127%) of a dye-sensitized solar cell is achieved by mixing the small: large ZnO particles in a ratio 60:40. The increased efficiency is due to the harvesting of light caused by scattering effect from larger sized ZnO particles. The ZnO layer consisting of smaller particles which are very next to the ZnO bigger particles makes a good electronic contact between film electrode and the Indium-doped tin oxide glass substrate resulting in the increases in the dye molecules adsorption. The over-layered, large-sized ZnO particles enhance the light-harvesting by light scattering effect. Compared to the other mixtures of ZnO films, there is a decrease in the photovoltaic performance of the solar cell when ZnO particles (small and large in a ratio 1:1) were adsorbed onto the Ni (II) oxime complex, which are caused due to the decrease in the surface area and dye aggregation.

Tartaric Acid-Modified Holarrhena antidysenterica and Citrullus colocynthis Biowaste for Efficient Eradication of Crystal Violet Dye from Water

Two novel adsorbents Holarrhena antidysenterica (HA) and Citrullus colocynthis (CC) were collected from native Pakistan and treated with tartaric acid. The adsorbents were characterized by Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy, and their adsorptive behavior was studied against model cationic dye crystal violet (CV). Role of biosorbent dose, time of contact, temperature studies, agitation rates, and solution pH was investigated. Optimum conditions obtained for the removal of CV dye for H. antidysenterica-tartaric acid modified (HA-TA) were as follows: 0.8 g adsorbent dose, 35 minutes contact time, 5.0 pH, 40°C temperature, and 150 rpm agitation rates as compared to H. antidysenterica that gave 1.4 g adsorbent dose, 40 minutes time of contact, 6.0 pH, 50°C temperature, and 150 rpm agitation speed. C. colocynthis-tartaric acid modified (CC-TA) removed CV dye at 0.6 g adsorbent dose, 30 minutes contact interval, 4.0 pH, 40°C temperature, and 125 rpm agitation speed in contrast to C. colocynthis which gave 0.8 g adsorbent dose, 40 minutes time of contact, 6.0 pH, 50°C temperature, and 125 rpm agitation speed, respectively. Isothermal studies for both raw and modified biosorbents were compliant with the Langmuir model indicating monolayer, chemisorption. The maximum Langmuir capacities were up to 128.20 mg/g, 136.98 mg/g, 144.92 mg/g, and 166.66 mg/g for HA, CC, HA-TA, and CC-TA. Pseudo-second-order kinetic model well fitted the dye removal data. The rate-determining steps involved both surface and intraparticle diffusion mechanisms. Adsorption of dye molecules on active surfaces was governed by electrostatic attractions and chelating abilities. Thermodynamics research revealed the spontaneous and exothermic nature of the reaction. The adsorbents serve promising candidates for the effective removal of hazardous dyes from aqueous solutions.

Ce(III) networked chitosan/β-cyclodextrin beads for the selective removal of toxic dye molecules: Adsorption performance and mechanism

The adsorption of dye molecules from the contaminated water onto the biopolymer is regarded as insignificant since such materials have weak physical, chemical and mechanical stability. However, their surface modification with various organic and inorganic materials lead to a drastic change in their adsorption behaviour. The work revealed the fabrication of a new Ce(III) networked chitosan/β-cyclodextrin (Ce@CCD) adsorbent beads and their utilization for the adsorption of RB4, IC and AB158 dye molecules from water/wastewater. The maximum adsorption capacity of Ce@CCD beads for the removal of RB4, IC and AB158 dye molecules were 29.56, 30.57 and 30.57 mg/g, respectively. The adsorption of RB4, IC and AB158 dye molecules on Ce@CCD beads mainly take place through the electrostatic attraction, hydrogen bonding and surface complexation interactions. The experiments recommended a promising method for the preparation of Ce@CCD adsorbent beads and their application in the advanced adsorption of dye molecules from water.

Synthesis of water dispersible phosphate capped CoFe2O4 nanoparticles and its applications in efficient organic dye removal

We synthesize cobalt ferrite nanoparticles capped with an ultrathin phosphate layer of ∼ 1 nm thick by co-precipitation followed by hetero condensation of free surface OH- groups of orthophosphoric acid on CoFe2O4 particles. The synthesized phosphate capped CoFe2O4 nanoparticles (CFP) are characterized using X-ray diffractometer (XRD), simultaneous thermogravimetric analyser with differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), Vibrating sample magnetometer, Dynamic light scattering, Transmission electron microscopy and Energy dispersive X ray spectroscopy. XRD results confirm the formation of CoFe2O4 nanoparticles and the signature of POM stretching vibrations at 900 – 1200 cm−1 seen in FTIR spectrum confirm the surface bound phosphate moieties. The prevalent adsorption of water molecules through hydrogen bonding with PO43- moieties capped on CoFe2O4 nanoparticles made them hydrophilic in nature. The adsorption of different dyes on these particles is studied systematically. The phosphate moieties over cobalt ferrite greatly enhanced the adsorption of methylene blue where the adsorption efficiency and adsorption capacity were ∼ 89.5 % and ∼ 4.5 mg. g−1 respectively within 5 min. of incubation, as compared to nearly zero adsorption of methylene blue on uncoated CoFe2O4. On the other hand, the adsorption efficiency and capacity of brilliant blue R, bromo phenol blue and rhodamine B on CFP was very low. These results show that the adsorption of dye molecules over these particles depends on the nature of interactions between their functional moieties. The modes of interaction and influence of different functional moieties of dyes with phosphate moieties on CFP is studied and compared. As compared to the nonmagnetic nanoparticle based dye removal, the present approach is most suited for straight through channel dye removal without labor intensive steps such as centrifugation, precipitation and filtration.

Dual-Responsive Pickering Emulsion Stabilized by Fe3O4 Nanoparticles Hydrophobized in Situ with an Electrochemical Active Molecule

In this paper, a redox and magnetic dual responsive toluene-in-water Pickering emulsion was stabilized by negatively charged Fe3O4 nanoparticles hydrophobically modified by positively charged oxidized ferrocene azine (Fc+A) via electrostatic interaction. The results showed that the adsorbed amount was 0.24 mmol/g and the molecular area was 0.27 nm2 for Fc+A at the Fe3O4 particles surface, which was higher than that at air-water interface (0.21 nm2), implying the adsorption process was typical monolayer adsorption. Because of the adsorption and desorption of Fc+A on the Fe3O4 particles surface, the Pickering emulsion prepared by Fc+A modified Fe3O4 nanoparticles could be reversibly switched between stable and unstable states by alternately adding reducing agent N2H4·H2O and oxidant H2O2. And approximately 80% of particles adsorbed at oil-water interface were returned to water phase after adding N2H4·H2O into the emulsion. At the same time, the emulsion droplets could be close to each other by applying an external magnetic field without demulsification due to the super paramagnetic properties of Fe3O4 nanoparticles, indicating the high stability and magnetic responsiveness of emulsion. Moreover, by applying an external magnetic field, Fc+A modified Fe3O4 nanoparticles stabilized Pickering emulsion was a good extraction system for purifying the aqueous solution contaminated by rhodamine B (RhB).The extraction efficiency (about 97.5 %) was attributed to the hydrophobicity, non-covalent interaction between RhB and Fc+A modified Fe3O4 nanoparticles, and the high specific surface area of emulsion droplets. After the adsorption, the emulsion droplets could be restored to the original emulsion by washing using magnetic field, which can be used to extract contaminated water again. That is to say, the redox and magnetic field dual-responsive Pickering emulsions can not only achieve demulsification/emulsification cycles by redox regulation, but also respond to magnetic field, which provides a promising way to construct functional Pickering emulsion in situ to adsorb dye molecules from aqueous solution.

Recent Advances in the Use of Metal-Organic Frameworks for Dye Adsorption.

Organic dyes are heavily used in industries for the manufacture of colored goods. This has eventually resulted in the generation of contaminated wastewater which is hard to be purified. Recent studies have demonstrated that metal-organic frameworks (MOFs), a class of supramolecular materials of immense interest, are useful in the adsorption of organic dye molecules because of their modifiable porous structures. In this mini review, the recent advances in the use of MOFs for the adsorption of organic dyes will be summarized.

Perceptive removal of toxic azo dyes from water using magnetic Fe3O4 reinforced graphene oxide–carboxymethyl cellulose recyclable composite: Adsorption investigation of parametric studies and their mechanisms

A magnetic FGC composite was prepared using Fe3O4 particles and graphene oxide–carboxymethyl cellulose which were blended as the source materials. The adsorptive interactions of FGC matrix with dye molecules like Congo Red (CR), Acid Red 1 (AR1) and Reactive Red 2 (RR2) were examined and explained through various analytical techniques. The optimum conditions for the adsorption of dyes include the initial concentration of dyes (50 mg/L), volume of dyes (50 mL), adsorbent dosage (100 mg) and solution pH (3-6). In these conditions, the FGC showed extreme adsorption efficiency of 45.09, 47.32 and 46.21 mg/g for the removal of CR, AR1 and RR2 dye molecules, respectively. The Freundlich isotherm data shows better fit for dye molecules adsorption. The thermodynamic results confirmed the endothermic and spontaneous nature in adsorption. The mechanism of CR, AR1 and RR2 dyes adsorption on FGC composite follows the interactions such as electrostatic attraction, hydrogen bonding, π−π stacking, and surface complexation. The FGC composite was regenerated over 65% after five consecutive cycles using an aqueous 0.1 M NaOH solution. The FGC composite showed an enhanced adsorption capacity for the removal of toxic azo dyes. Hence, the prepared composite could be used as a potential adsorbent for the removal of dye molecules from contaminated water.

Fe2O3/MCM‐41 as catalysts for methyl orange degradation by Fenton‐like reactions

AbstractA large amount of contaminated industrial wastewater has aroused mounting concern by researchers and environmentalists. Dyes contained in industrial effluents are often quite persistent to biodegradation, which must be treated before being disposed of. In this context, the use of Fenton processes is a potential alternative to treat a wide range of dyes and other organic pollutants found in wastewater. Thus, several Fe2O3/MCM‐41 catalysts have been synthesized in the following molar ratio of SiO2/Fe2O3: 10, 20, 40, 100, and 200. They were characterized by N2 adsorption–desorption isotherm, X‐ray fluorescence (XRF), X‐ray diffraction (XRD), UV–vis spectroscopy and H2 temperature‐programmed reduction (H2‐TPR), and applied to degrade methyl orange dye (MO) via a heterogeneous Fenton reaction. Catalytic tests revealed that SiO2/Fe2O3 = 10 reached the highest activity due to greater availability of active sites which generated a larger quantity of hydroxyl (•OH) and perhydroxyl (•OOH) radicals. Furthermore, 70% of color removal has been achieved after 120 min at room temperature. Moreover, the systems moderately enhanced organic matter mineralization according to chemical oxygen demand (COD) testing. There was also catalytic activity loss in consecutive reaction cycles, which is probably due to dye molecules adsorption on active sites.

DyxMnFe2-xO4 nanoparticles decorated over mesoporous silica for environmental remediation applications

An efficient, environment-friendly and economical catalyst to control contaminants of environment is an enduring interest in recent years. In this study, a new composite, DyxMnFe2-xO4nanoparticles decorated over mesoporous silica was synthesized and utilized for removal of organic pollutant. Highly crystalline nature of DyxMnFe2-xO4 nanoparticles and amorphous nature of material was confirmed by XRD (X-ray diffraction) technique. Infrared spectra of fabricated material before and after adsorption of dye molecules evidenced the successful adsorption of dye molecules by fabricated adsorbent. From field emission scanning electron microscopic (FESEM) images of Dy3+ substituted MnFe2O4 composite with mesoporous silica, it was clearly observed that ferrite particles of size 20−30 nm were decorated on the surface of mesoporous silica particles and distributed well over spherical silica balls homogeneously. Its magnificent mesoporous nature was revealed from BET (nitrogen adsorption-desorption measurements) analysis. Surface area, pore volume and average pore size was found 387.95 m2/g, 0.390 cm3/g and 4.02 nm respectively. Tri-modal pore size distribution showed its effective utilization in adsorption. The abundant (SiOH) hydroxyl groups of mesoporous silica, the broad diffraction hump of silica depicted its superior loading capacity of target molecular specie inside its porous network. From band gap analysis, a red shift of 2.43 eV exhibited semiconductor photocatalysis of DyxMnFe2-xO4 nanoparticles. Degradation efficiency of bare MnFe2O4, DyxMnFe2-xO4 and mesoporous silica-based composite was tested using crystal violet dye. Its explored adsorption-photocatalysis synergy, degradation mechanism, kinetic investigation, easily recovery and remarkable recycling ability suggested that the new fabricated composite is best for environmental remediation.

An anionic cadmium-organic framework with an uncommon 3,3,4,8-c network for efficient organic dye separation

A novel anionic metal–organic framework (MOF), {[Cd5(L)4·Na2·(H2O)]·2(CH3)2NH2·3DMF} (LYU-2, Linyi University) (H5L = 2,5-bis(3′,5′-dicarboylphenyl)-benzoic acid), has been solvothermally synthesized and characterized. LYU-2 contains microporous channels with a complicated 3D tetranodal 3,3,4,8-c network, uncoordinated carboxylate groups and coordinated H2O molecules, exhibiting excellent selective adsorption and separation of small cationic dyes through an ion-exchange process in aqueous solution. According to UV/Vis spectroscopy analysis of LYU-2, methylene blue (MB+) and crystal violet (CV+) can be rapidly adsorbed, whereas larger rhodamine B (RB+), anionic methyl orange (MO−), and neutral sudan II (SD0) can hardly be adsorbed. The results imply that the adsorption of dye molecules in LYU-2 displays not only a charge effect, but also a size- and shape-exclusive effect. Furthermore, the adsorbed MB+ can be gradually released in a NaCl-containing aqueous solution.

Highly efficient reusable Cashew Nut derived Activated Carbon-Loaded TiO nanomaterial, characterization and its multi application

Cashew nut is derived activated from a carbon-loaded-titanium dioxide (CNAC-TiO2) is a nanomaterial which has been synthesized by a hydrothermal method. This nanomaterial is characterized by HR-SEM and HR-TEM which shows that CNAC-TiO2 nanobundle is spherical-shaped structure. X-ray (EDX) analysis confirms the C, Ti, and O present in CNAC-TiO2 nanomaterial; XRD analysis reveals the average crystalline size of the prepared CNAC-TiO2 nanomaterial and as almost 36 nm. FT-Raman analysis shows anatase TiO2 and confirmed by the nanostructure. The PL analysis showed in CNAC-TiO2 is a recombination of electron-hole pairs by a transfer of electrons and the holes between TiO2. Brunaur-Emmett-Teller (BET) which shows the surface area and shows an increase in the adsorption of dye molecules on the nanomaterial surface. This will enhance the photocatalytic activity and the photocatalytic activity of CNAC-TiO2; the nanomaterial was studied from the photodegradation of malachite green (MAG). The rhodamine B (Rh B), methyl green (MEG), and methylene blue (MB) dye are under the UV-light irradiation at 365 nm. The hydroxyl radical formation was confirmed by the fluorescence quenching. An achievable mechanism is proposed for a higher activity of CNAC-TiO2 under the UV-light at 365 nm. The first-order kinetic study and quantum yield of evaluation were done and the catalyst was found to be stable and reusable and also having anti-bacterial activity.

Utilization of Biomass Fly Ash for Improving Quality of Organic Dye-Contaminated Water.

Development of innovative methodologies to convert biomass ash into useful materials is essential to sustain the growing use of biomass for energy production. Herein, a simple chemical modification approach is employed to functionalize biomass fly ash (BFA) with 3-aminopropyltriethoxy silane (APTES) to develop an inexpensive and efficient adsorbent for water remediation. The amine-functionalized BFA (BFA–APTES) was fully characterized by employing a range of characterization techniques. Adsorption behavior of BFA–APTES was evaluated against two anionic dyes, namely, alizarin red S (ARS) and bromothymol blue (BTB). In the course of experimental data analysis, the computation tools of data fitting for linear and nonlinear form of Langmuir, Freundlich, and the modified Langmuir–Freundlich adsorption isotherms were used with the aid of Matlab R2019b. In order to highlight the misuse of linearization of adsorption models, the sum of the squares of residues (SSE) values obtained from nonlinear models are compared with R2 values obtained from the linear regression. The accuracy of the data fitting was checked by the use of SSE as an error function instead of the coefficient of determination, R2. The dye adsorption capacity of BFA–APTES was also compared with the nonfunctionalized BFA. The maximum adsorption capacities of BFA–APTES for ARS and BTB dye molecules were calculated to be around 13.42 and 15.44 mg/g, respectively. This value is approximately 2–3 times higher than the pristine BFA. A reasonable agreement between the calculated and experimental values of qe obtained from the nonlinear form of kinetic models verified the importance of using equations in their original form. The experimentally calculated thermodynamic parameters including molar standard Gibbs free energy (ΔadGm0) and molar standard enthalpy change (ΔadHm0) reflected that the process of adsorption of dye molecules on the BFA–APTES adsorbent was spontaneous and exothermic in nature. Moreover, the used BFA–APTES adsorbent could be regenerated and reused for several cycles with significant dye adsorption capacity. The remediation capability of the BFA–APTES adsorbent against ARS dye was also demonstrated by packing a small column filled with the BFA–APTES adsorbent and passing a solution of ARS through it. Overall, we provide a simple and scalable route to convert BFA into an efficient adsorbent for water remediation applications.

Photocatalytic degradation of methylene blue using three-dimensional porous graphene-titania microparticles under UV light

Porous graphene and graphene-silica microparticles containing titania nanoparticles were synthesized by emulsion-assisted self-assembly for the photocatalytic decomposition of methylene blue in an aqueous medium. After the mixed dispersion of graphene nanosheets and titania nanoparticles with or without silicic acid was prepared, the complex fluid was emulsified in a continuous oil phase to form tiny droplets that act as micro-reactors for the synthesis of porous photocatalytic particles, the morphology of which was three-dimensional spherical shapes with a number of irregular-shaped macropores. The three dimensional conductive graphene scaffolds greatly enhanced the photocatalytic activity of the porous particles due to the suppression of the recombination of electron-hole pairs generated from titania under UV light irradiation, and adsorption of dye molecules on graphene-silica scaffolds caused rapid removal of aqueous contaminants. Unlike previous reports, the kinetics of the photocatalytic decomposition reaction could not be explained by Langmuir-Hinshelwood kinetics, but the experimental data could be fitted well by the second- or third-order kinetics. This indicates that the removal rate of the pollutant could be enhanced by the supporting material. The removal efficiency of methylene blue was estimated as more than 95% when sufficient amount of the photocatalytic particles was used, implying that application to water treatment process will be possible.

Self-cleaning, antibacterial mixed matrix membranes enabled by photocatalyst Ti-MOFs for efficient dye removal

Membrane separation technologies have been extensively implemented in wastewater polluted by dyes because of their eco-friendliness, superior separation efficacy, and energy-saving capacity. Despite impressive advances of membrane technologies, membrane fouling severely impairs the separation performance and lifespan, remaining a challenging task to be addressed. In this study, the MIL-125(Ti)/PVDF mixed matrix membrane with a superb self-cleaning merit was constructed through a wet phase inversion method. Interestingly, MIL-125(Ti) was commonly utilized for photocatalytic degradation of organic matters under UV light, but the hybrid membranes containing MIL-125(Ti) were able to effectively degrade the foulant RhB under natural light. This was due to the sensitization of MIL-125(Ti) caused by the physical adsorption of RhB dye molecules on MIL-125(Ti) during the rejection process, where they could promote electron transfer to produce hole (h+) and superoxide free radicals (•O2−). The optimal hybrid membranes exhibit ultrahigh water permeance (64.3 L m−2 h−1 bar−1) and remarkably high dye retention (RhB, 99.7%). Furthermore, due to superb photocatalytic degradation of the foulants, the flux of the treated membranes can almost be recovered to the initial state even after three cycles. More importantly, the mixed matrix membranes exhibit an ultra-high bacteriostatic rate of nearly 100%. The unique self-cleaning and antibacterial features render the MIL-125(Ti) modified membranes highly promising in the treatment of textile wastewater.

Walnut shell powder as a low-cost adsorbent for methylene blue dye: isotherm, kinetics, thermodynamic, desorption and response surface methodology examinations

The low cost, eco-friendly and potential biomass, i.e. walnut (Juglans regia) shell powder was deployed for the removal of toxic methylene blue dye from contaminated water solution. The important characterization of the waste material was conducted by using several techniques, i.e. Scanning electron microscope, Fourier-transform infrared spectroscopy, Energy-dispersive X-ray spectroscopy, X-ray powder diffraction, Brunauer-Emmett-Teller surface area analysis, and Thermogravimetric analysis. The marked impact of various operating conditions, i.e. dose, concentration, time, pH and temperature on the adsorption process was investigated. Increasing pH resulted in an increase of percent dye adsorption, and the adsorption mechanism was occurred by electrostatic attraction between negative adsorbent surface and positive dye molecules. The equilibrium data suited with Langmuir isotherm model while the adsorption practice followed the pseudo-second-order kinetic model. Higher temperature reduced the adsorption of dye molecules. The adsorption process was spontaneous, exothermic and chemical. The critical statistical analysis of the experimental results was directed by forming the design of the experiment, which was further, optimized by ANOVA, 3D and perturbation plots. The error and predicted values of both the studied responses as derived from the statistical model showed the agreeable results. 0.1 N HCl was found to be effective in complete desorption. The results are very practical and prove the effectiveness of walnut shell powder in the usage of decolorization for methylene blue.

Adsorptive removal of bulky dye molecules from water with mesoporous polyaniline-derived carbon.

Polyaniline-derived carbon (PDC) was obtained via pyrolysis of polyaniline under different temperatures and applied for the purification of water contaminated with dye molecules of different sizes and charge by adsorption. With increasing pyrolysis temperature, it was found that the hydrophobicity, pore size and mesopore volume increased. A mesoporous PDC sample obtained via pyrolysis at 900 °C showed remarkable performance in the adsorption of dye molecules, irrespective of dye charge, especially in the removal of bulky dye molecules, such as acid red 1 (AR1) and Janus green B (JGB). For example, the most competitive PDC material showed a Q0 value (maximum adsorption capacity) 8.1 times that of commercial, activated carbon for AR1. The remarkable adsorption of AR1 and JGB over KOH-900 could be explained by the combined mechanisms of hydrophobic, π–π, electrostatic and van der Waals interactions.