Papers by Keyword: Dyes

Abstract: This study evaluates the potential of hemp shives (HS) as candidate for two basic dyes removal, namely Azure B (AB) and Malachite Green (MG), from aqueous solutions. The biosorption tests were conducted in batch mode. The influence of experimental variables, including pH, dye concentration, adsorbent dosage, and contact time, was evaluated. Under optimal biosorption conditions, equilibrium and kinetic studies were conducted in order to gain further insight into the process. Hemp shives, without any additional treatment, exhibited the highest value of the maximum Langmuir adsorption capacity reported in the literature for AB (q_max = 364.4 mg/g). Furthermore, HS has demonstrated superior MG removal efficiency compared to other biosorbents previously reported, reaching a value of q_max = 91.0 mg/g. The biosorption of both dyes can be described by a pseudo-second-order kinetic model. The formation of chemical bonds between the dye molecules and the active sites of the biosorbent represents the rate-limiting step in the process. Moreover, it has been demonstrated that the spent hemp shives can be partially regenerated. The AB biosorption capacity of the recycled material (q₂ = 23.60 mg/g), which had been washed with HCl, was approximately half that of the adsorption capacity of the fresh HS (q₁ = 44.80 mg/g). Following the washing of spent hemp shives with acetic acid, it was observed that the recycled material retained in excess of 40% of its original biosorption capacity for AB (q₂ = 18.72 mg/g). The desorption of MG from HS is a more challenging process than that of AB.

Abstract: The present study utilized high-impact polystyrene, a polymer with good mechanical, thermal and chemical stability, for its potential as a filter material and matrix for nanozeolite – a well-known adsorbent for wastewater treatment. Different concentrations of nanozeolite (0.25%, 0.5%, and 0.75%) were added to the high-impact polystyrene matrix and were fabricated intocomposite membranes via hand-casting method. The membranes were characterized using Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, and Contact Angle Goniometer to discuss their functionality in the removal of nanocontaminants from wastewater like dyes. Results showed that nanozeolite can control the porosity and pore size of the High-impact polystyrene polymer while also improving its hydrophilicity; these are important considerations in the removal of organic dyes from wastewater.

Abstract: In this work, a low-cost method to produce ZnO nanostructured materials for the treatment of water polluted with model organic pollutants (e.g. dyes) is presented. Zinc and silver-coated Zn (Ag/Zn) films, fabricated via sputtering method were naturally oxidized via a simple, low-temperature, scalable thermal process. During oxidation, Ag/ZnO nanorods were grown on Zn foils after treating their surface with various agents (e.g. acids) and annealing in an oven at temperatures 385-400 °C. The ZnO and Ag/ZnO films on Zn were characterized by X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy. The cationic dye Methylene Blue (MB) was selected as model pollutant dissolved in water, and a batch photo-reactor was fabricated and used to to study the adsorption capacity and photocatalytic performance of films. The transient varation of MB concentration in aqueous solutions was measured with UV-Vis spectroscopy. Ag/ZnO demonstrated a strong MB adsorbion capacity in dark conditions, and a satisfactory MB photocatalytic degradation under UV light irradiation.The optimized doping of Ag in Ag/ZnO film enhanced its photocatalytic activity, and seems well-promising for the potential scale-up of Ag/ZnO films, and use in large-scale systems for water purification under UV light irradiation.

Abstract: Recycling is promising to dispose the wasted Poly (ethylene terephthalate) (PET) fibers currently. However, high temperature and oxygen in the recycling process may accelerate the degradation of PET and residual dyes, resulting in the volatile organic compounds (VOCs) emissions, which will do serious harm to the environment and human health. Exploring the source of VOCs is significant to remove VOCs and keep products safety. This study was carried out to investigate the influence of high temperature on the release of four VOCs (formaldehyde (CH₂O), acetaldehyde (C₂H₄O), benzene (C₆H₆) and toluene (C₇H₈)) during the recycling process of PET fibers, utilizing thermogravimetric analysis and differential thermal analysis coupled with mass spectrometric (TGA-DTA/MS). The atmospheres and heating conditions of esterification, polycondensation and melt spinning were simulated by TGA with various atmospheres and programmed heating processes (heating from 50 °C to 240 °C in Ar, 280 °C in Ar and 280 °C in air, respectively, and then maintaining for 30min). Bis (2-hydroxyethyl) terephthalate (BHET) (esterification product) and virgin PET (VPET) were used to explore the thermal degradation of PET. White PET popcorn, black PET popcorn and dyes were used to explore the effect of dyes on the release of VOCs. The results indicated that: (1) Aldehydes including formaldehyde and acetaldehyde are generated during the manufacturing process of PET, mainly due to its thermal oxidation;(2) Aromatic compounds including benzene and toluene are originated from the disperse dyes. So the degree of dye removing has a great influence on the production safety; (3) Thermal oxidation causes more VOCs than nonoxidative thermal degradation. So in the stages of melt spinning and slightly alcoholysis, usually in O₂ containing atmosphere, devolatilization should be developed further.

Abstract: In this work, the heat-activated persulfate (PS) in the presence of Fe₇₈Si₉B₁₃ metallic glasses (MGs) shows an extremely difference in degradation of azo dye and triarylmethane dye, where Fe₇₈Si₉B₁₃ MGs exhibits a superior activation ability for PS with assistance of heat leading to the fast removal of two dyes. The structural features of Fe₇₈Si₉B₁₃ MGs are firstly characterized by X-ray diffraction (XRD) and differential scanning calorimetry (DSC), following analysis of surface topography by scanning electron microscope (SEM). The results show that with the addition of Fe₇₈Si₉B₁₃ MGs, the recalcitrant azo dye is completely removed within 5 min while only 6% of removal rate can be achieved without adding MGs, indicating that the refractory azo dye can be easily degraded by sulfate radical (SO₄•^–) from heat/MGs/PS. On the other hand, no big variation occurs between PS and MGs/PS under heat activation in degrading triarylmethane dye. Sole PS activated by heat results in a fast removal rate, indicating that triarylmethane dye can be easily degraded by PS itself compared to azo dye. The findings in this work present an in-depth understanding of heat/MGs/PS system in dyes degradation.

Abstract: We have reported on the fluorescence behaviors of Rhodamine 6G with the palladium-coat gold nanorods in dichlormethane solution and in polymethylmethaceylate thin film. By monitoring the emission intensity of these samples, they show the enhancement of fluorescence intensity through the optical effect known as a plasmon resonance energy transfer. The enhancement intensity of fluorescence is enhanced up to 1.6 fold for the sample solution and 1.4 fold for the sample thin film.

Abstract: Synthesis and characterization of a new hybrid ion exchange material Zirconiumresorcinol Phosphate (ZrRP) is reported in this study. Synthetic conditions such as reactant concentrations and mixing volume ratio were varied to optimize the ion exchange properties of this material. The material has Na⁺ ion exchange capacity equal to 1.7 meq/g (dry). X-ray diffraction spectra suggest that it is amorphous in nature. This ion-exchanger was also characterization by SEM, IR and TGA-DTG. Various studies such as determination of ion exchange capacity, elution behaviour and pH titration has been performed for different metal ions such as K⁺, Ca²⁺, Sr²⁺, Mg²⁺, Ni²⁺, Cd²⁺. This material has potential application for removal of these ions from the aqueous systems. Effect of anionic (SDS) and nonionic (TX-100) surfactants has also been studied on the adsorption behavior of ZrRP. The material has been found to be selective for Mg²⁺and Cd²⁺. We also found that the material showed remarkable adsorption behavior towards some dyes like malachite green and methylene blue.

Abstract: One of the most pervasive problems affecting people throughout the world is inadequate access to clean water and sanitation. Problems with water are expected to grow worse in the coming decades, with water scarcity occurring globally. Many recent studies have been reported on the photodegradation of the organic compounds in industrial wastewater in the presence of TiO₂ semiconductor as photocatalyst. Heterogeneous photocatalysts using iron as a dopant metal, so far, have been reported for various environmental applications. This paper highlights the recent advances and applications of Fe-TiO₂ photocatalysis for the degradation/photodegradation of various pollutants, alkanolamines and other organic pollutants like phenols and dyes.

Abstract: Magnetite-silica nanocomposites (Fe₃O₄/SiO₂) have been synthesized and characterized and were used as an effective sorbent material for dyes removal from environmental water samples. They were prepared by a simple procedure via a co precipitation of iron (II) and iron (III) ion mixture in ammonium hydroxide and then was impregnated by a sodium silicate. The prepared samples were characterized using Zeta potential, XRD, VSM, TEM, EDS, and porosity analysis. The result of characterization showed that Fe₃O₄ nanoparticles have been coated by silica. The composite have been superparamagnetic behaviour at room temperature and contain both meso-and microporosity system. Mesoporosity contributes dominantly to the pore volume. Adsorption performance of magnetic-silica nanoparticles were examined its ability to adsorp methylene blue dye in aqueous solution. The 20 mg/L of initial concentration of methelene blue, 1 gr/L adsorbent in solution and under shakker for 5 hour, the remain of methylene blue in solution was 13,3% for Fe₃O₄/SiO₂ (3:1), 30,2% for Fe₃O₄/SiO₂ (2:1) and 24,2 % for Fe₃O₄/SiO₂ (1:1). The composite was effective to adsorb dyes in water and can be easily recovered from treated water with helping of magnetic bar.

Abstract: Ethylenediamine-modified magnetic chitosan microspheres (EMCS) were prepared and used for the adsorption of Reactive Brilliant Red X-3B (RBR), Reactive Light Yellow K-6G (RLY) and Reactive Brilliant Blue X-BR (RBB). The EMCS has good adsorption performance for RBR and RLY. When the pH was 5.3 and 5.8 at 298K, initial concentration was 200mg/L, the adsorption capacity for RBR and RLY reached 98% and the maximum adsorption quantity achieve 198.99 and 122.2mg/g respective. The adsorption capacity of RBB on EMCS was unideal (<10%). The adsorption isotherm of RBR was fitted by both Langmuir and Freundlich equation, and the adsorption isotherm of RLY turned out to be more agree with Langmuir equation. The adsorption process follows a pseudo-second-order kinetic model for both RBR and RLY.