Adsorbent For Removal Of Anionic Dyes Research Articles

Enhanced Adsorptive Removal of Anionic Dyes by using Calcined Zinc Aluminium Layered Double Hydroxide CZA-LDH from Aqueous Solution

Removal of anionic dyes namely Acid Violet-17(AV-17) and Direct Red-7 (DR-7) from aqueous solution were investigated by calcined zinc aluminium layered double hydroxide (CZA-LDH). Batch adsorption studies were carried out by varying the parameters such as contact time, adsorbent dose, initial dye concentration, temperature and pH. The equilibrium adsorption capacity of AV-17 (adsorbent dose 0.5g/L) and DR-7(adsorbent dose 0.125g/L) dyes were increased from 48.08 mg/g to 172.55 mg/g and 200 mg/g to 683.33 mg/g respectively with increase of initial dye concentration from 25 mg/L to 100 mg/L at 30°C. Similarly the percentage of dye removal was decreased from 100% to 85.42% and 96.15% to 86.27% for DR-7 and AV-17 respectively with increase of initial dye concentration from 25 mg/L to 100 mg/L. The adsorption kinetics of both the anionic dyes AV-17 and DR- 7 by CZA-LDH followed the pseudo second order kinetic model with high correlation coefficient values (R2) than the pseudo first order. The experimental data were well fitted with Freundlich isotherm model rather than Langmuir model. The adsorption equilibrium was more favourable at acidic pH than alkaline pH for both dyes. The thermodynamic parameters like ΔGo and ΔHo calculated for AV-17 and DR-7 revealed that the adsorption process is spontaneous and endothermic in nature. The XRD pattern of CZA-LDH before and after the adsorption of AV-17 and DR-7 proved the intercalation of anionic dyes between the layers with memory effect by the reconstruction of its original layered structure. This was further evidenced by slight increase in the interlayer distance. The adsorption processes were further supported by Langmuir dimensionless separation factor RL and n value of the Freundlich Equation. Thermal regeneration and reusability of CZA-LDH was performed for the removal of AV-17 & DR-7. The recycling and reusability for the dye removal up to second cycle for both anionic dyes were remarkable and suggested that the CZA-LDH was an effective adsorbent for the removal of anionic dyes AV-17 and DR-7 from aqueous solution.

Anionic dyes removal from aqueous solution using TMU-16 and TMU-16-NH2 as isoreticular nanoporous metal organic frameworks

The adsorptive removal of anionic dyes were investigated over two isoreticular nanoporous Zn(II)-MOFs known as TMU-16 and TMU-16-NH2 in view of the influence of an amine group on the adsorption capacity. Adsorption isotherms, thermodynamics and kinetics parameters of the sorbents were studied and also effective factors on dye adsorption have been optimized. Thermodynamic and kinetic results revealed adsorption over two MOFs is spontaneous and pseudo-second order, as well as TMU-16-NH2 showed higher removal yield to TMU-16 because of forming hydrogen bonding between dyes and amine groups. These MOFs showed great adsorption uptakes for anionic dyes than other porous materials that reported previously. Adsorption mechanism could be explained by electrostatic and hydrogen bonding interactions. Importantly TMU-16 and TMU-16-NH2 due to high adsorption capacity and stability of structures could be employed as excellent sorbents to remove harmful dyes in contaminated water.

Polyethylenimine nanofibrous adsorbent for highly effective removal of anionic dyes from aqueous solution

We prepared a nanofibrous adsorbent for anionic dye removal from aqueous solution by electrospinning a modified polyethylenimine (m-PEI) and polyvinylidene fluoride (PVDF) blend. The electrospun nanofibrous adsorbent was confirmed to be a nanoscale, porous material with a positively charged surface; these characteristics are quite beneficial for anionic contaminant adsorption. Experimental adsorption of an anionic dye, methyl orange (MO), demonstrates that this adsorbent can rapidly remove MO from aqueous solution; its maximum adsorption capacity was 633.3 mg g−1, which is much higher than that of previously reported adsorbents. After immersion in a basic solution, the adsorbent was well regenerated and showed good recyclability. The adsorption performance of the nanofibrous adsorbent is greatly influenced by the temperature, initial MO concentration, and pH of the solution. We further found that MO adsorption onto the adsorbent can be described well by the pseudo-second-order kinetic model and Langmuir isotherm model. Weber-Morris plots suggested that the adsorption of MO onto the nanofibrous mat was affected by at least film diffusion and intraparticle diffusion. This study indicates that nanofibrous PEI composite mats could be promising for treatment of wastewater containing anionic dye.

Equilibrium and kinetic models on the adsorption of Reactive Black 5 from aqueous solution using Eichhornia crassipes/chitosan composite

New natural biopolymer composite was prepared using extracted cellulose from an environmentally problematic water hyacinth Eichhornia crassipes (EC). The extracted cellulose was functionalized by chitosan and TiO2 nanoparticles to form EC/Chitosan (EC/Cs) composite network. Surface characterization of EC/Cs natural biopolymer composite was examined by spectrum analysis FT-IR, specific surface area, micropore volume, pore width and SEM. Furthermore, the sorption experiments were carried out as a function of pH, various initial dye concentration and contact time. Experiment results showed that the EC/Cs composite have high ability to remove C.I. Reactive Black 5 from its dye-bath effluent.The equilibrium sorption evaluation of RB5 conformed and fitted well to Langmuir adsorption isotherm models and the maximum sorption capacity was 0.606mg/g. The kinetic adsorption models followed pseudo-second order model and the dye intra-particle diffusion may suggesting a chemical reaction mechanism. Further, it was obvious from the investigation that this composite could be applied as a promising low cost adsorbent for anionic dye removal from aqueous solutions.

Adsorptive removal of anionic dyes from aqueous solutions using microgel based on nanocellulose and polyvinylamine

A novel nanocomposite microgel based on nanocellulose and amphoteric polyvinylamine (PVAm) was fabricated via a two-step method. Firstly, cellulose nanocrystal was oxidized by sodium periodate to yield dialdehyde nanocellulose (DANC). DANC was then used as a crosslinker to react with PVAm to obtain a pH responsive microgel with high density of free amine groups. The microgel was characterized using FTIR, XRD, AFM and elemental analysis. AFM images revealed that the nanocomposite was microspherical particles with a diameter ranging from 200 to 300nm. The microgel was found to be effective in anionic dye removal at acidic conditions. The adsorption isotherms for congo red 4BS, acid red GR and reactive light yellow K-4G fit well with the Sips model, and the maximum adsorption capacities were 869.1mgg−1, 1469.7mgg−1 and 1250.9mgg−1, respectively. The adsorption for these three anionic dyes all followed pseudo second order kinetics, indicating a chemisorption nature.

Hierarchical Fe3O4 Core–Shell Layered Double Hydroxide Composites as Magnetic Adsorbents for Anionic Dye Removal from Wastewater

AbstractHierarchical core–shell Fe3O4@Mg3Al–CO3 layered double hydroxide (LDH) as an efficient magnetic adsorbent was prepared and investigated for the adsorption of anionic dye under ambient conditions. The material was thoroughly characterized by a variety of spectroscopic methods, which indicate that it was composed of spherical Fe3O4 (ca. 330 nm) core with a vertically aligned Mg3Al‐CO3 layered double hydroxide shell coating. Calcination of Fe3O4@Mg3Al–CO3 LDH at 400 °C gives a layered double oxide coated Fe3O4 nanoparticles (Fe3O4@Mg3Al–CO3 CLDH), which is shown to be an efficient magnetic adsorbent for removal of the anionic dye, C.I. Acid Yellow 219 (AY219) from aqueous solution under ambient conditions. The adsorption of AY219 from aqueous solution utilizes the “memory effect” of LDHs by which the calcined LDH can be reconstructed by intercalation of AY219 in water. During the multi‐cycling tests, a stable adsorption capacity of 1024 mg/g was achieved after 3 cycles, which is the highest value among all reported magnetic dye adsorbents. We also demonstrate that the core‐shell structure played a great role for the superior performance of Fe3O4@Mg3Al–CO3 CLDH, as its performance was much better than a control hybrid mixed phase Fe3O4/Mg3Al–CO3 LDH. This research suggests that Fe3O4@Mg3Al–CO3 LDH adsorbent is a promising candidate for the treatment of wastewater contaminated by anionic dyes.

Preparation and formation mechanism of porous polyurea by reaction of toluene diisocyanate with water and its application as adsorbent for anionic dye removal

A novel and easy one-step protocol for preparation of a new porous material, polyurea (PPU), is reported, which is accomplished through a precipitation polymerization of toluene diisocyanate (TDI) in mixed solvent of H2O-acetone without need for surfactant and porogen. Effects of TDI concentration, mechanical stirring, solvent composition and TDI addition rate on PPU structure are studied. Surface morphology and pore structure of PPU are characterized by scanning electron microscopy and Hg intrusion. Chemical structure of the PPU polymer is investigated using NMR, XRD and FTIR. Mechanism of pore formation is discussed. The obtained PPU is used as adsorbent for anionic dyes adsorption investigation. Two anionic dyes, remazol brilliant blue R and acid fuchsine, are tested. The results indicate that the as-prepared PPU is of high performance in dye adsorption and recycled use. This study provided therefore a facile route to the preparation of a novel and attractive adsorbent candidate for removal of anionic dyes from wastewaters.

Adsorptive removal of anionic dye from aqueous solutions by mixture of Kaolin and Bentonite clay: Characteristics, isotherm, kinetic and thermodynamic studies

Adsorption isotherms Modified adsorbent Kaolin-bentonite clay Thermodynamics; Kinetics Desorption A B S T R A C T The textile effluents are considered as potential source of water contaminations. Thus the effective methods were adopted for the removal of dyes and colorants from the textile effluents. In the present research, the removal of textile dye Congo red was carried out by bentonite clay blend with kaolin. The kaolin-bentonite clay (KBC) was used as adsorbent. The adsorption properties of KBC towards Congo red were investigated, at various temperatures 303-318 ±2 K under the optimized conditions. The adsorption equilibrium data were fitted in Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models and the values of the respective constants were evaluated by employing standard graphical method. From the graph, it was founded that Langmuir model is the best fitted isotherm. Feasibility of adsorption process (RL) and sorption energy (Es) was also determined. The pH of adsorbent was estimated by pH drift method. Kinetics of dye removal was investigated that it follows pseudo second order rate constant. The surface morphology of adsorbent was observed by the Scanning Electron Microscope (SEM).

Mechanism of adsorption of anionic dye from aqueous solutions onto organobentonite

Organobentonite is suggested as potential super-sorbents for the removal of dyes from wastewater. All kinds of organobentonites are synthesized to adsorb dyes; however, the mechanism of the adsorption is still unclear. In this paper, organobentonites were first modified with hexadecyltrimethylammonium bromide at various amounts to reveal the adsorption mechanism. Subsequently, four kinds of organobentonites were utilized to adsorb acid dyes. Results show that the main mechanism of the adsorption of acid dye is an anionic exchange. The counter-ion bromide in the organobentonite was replaced by the dye anion. The study reveals that the adsorption capacity of organobentonite is affected by the surfactant alkyl chain length. When the longer alkyl chain surfactant was modified, bentonite showed higher adsorption capacity. Specific surface areas had no effect on the adsorption. However, the XRD patterns show that interlamellar distance and lamellar distribution have some effects on the adsorption. High adsorption capacity and low residual concentration were obtained by the organobentonite adsorbents. The revelation of the adsorption mechanism makes it possible to obtain more novel and suitable organobentonite adsorbents for anionic dye removal from wastewater.

Silica grafted with a silsesquioxane containing the positively charged 1,4-diazoniabicyclo[2.2.2]octane group used as adsorbent for anionic dye removal

The present study reports the development of an alternative adsorbent, based on silica modified with a water soluble silsesquioxane containing a double charged 1,4-diazoniabicyclo[2.2.2]octane, employed for removal of the dye brilliant yellow from aqueous solution. The dye removal ability of this adsorbent was determined by batch adsorption procedure. Effects such as pH value and adsorbent dosage on the adsorption capacity were studied. Four kinetic models were applied. The adsorption was best fitted to a fractionary-order kinetic model. The kinetic data were also adjusted to an intra-particle diffusion model resulting three linear regions, indicating that the adsorption kinetics follows multiple sorption rates. The equilibrium data were fitted to Langmuir, Freundlich, Sips and Redlich–Peterson isotherm models. The maximum adsorption capacity was 54 mg g − 1.

Adsorptive removal of anionic dyes by modified nanoporous silica SBA-3

Batch sorption experiments were carried out to remove dyes, methyl orange (MO), orange G (OG) and brilliant red X-3B (X-3B), from their aqueous solutions using a mesoporous silica SBA-3 as an adsorbent. The effect of surfactant template in SBA-3 on the removal of OG, MO and X-3B was investigated. Experiments were carried out to investigate the influence of contact time, initial concentration, pH, and adsorbent dosage on the adsorption performance. The adsorption results of anionic dyes on the uncalcined SBA-3 (noted as SBA-3) were compared with those of the calcined SBA-3 (noted as C-SBA-3). The uncalcined SBA-3 adsorbent has a large adsorption capacity and a strong affinity for the anionic dyes. Langmuir, Freundlich and Temkin isotherms were employed to model the experimental results, from which the Freundlich isotherm exhibited the most appropriate to predict the same. Freundlich isotherm exhibited the most appropriate to predict the experimental results. The kinetic data were also analyzed through pseudo-first-order and pseudo-second-order models. The pseudo-second-order kinetic model well depicted the kinetics of dyes adsorption on mesoporous SBA-3.

Adsorptive removal of anionic dye by inorganic–organic hybrid anion-exchange membranes

Anion-exchange membranes with quaternary ammonium groups were prepared by coating a precursor with secondary amino groups (the product of N-[3-(trimethoxysilyl)propyl] ethylene diamine and 3-(triethoxysilyl)propyl isocyanate) on porous glass fiber membranes and further treated with bromoethane. The precursor coating and bromoethane treatment have been proved successful by membrane characterization such as Fourier-transform infrared (FTIR) spectrum, scanning electron microscopy (SEM) photo, contact angle, water content, and ion-exchange capacity. The optimal feed precursor/dimethyl formamide (DMF) ratio was found as 1:3 (w/w) based on the batch adsorption results of anionic dye Cibacron blue 3GA. The membrane ion-exchange capacity for this condition was 6.8 μmol/cm 2 (or 104.2 μmol/cm 3) and the maximum dye adsorption capacity was 2.12 mg/cm 3. Different desorption solutions were tested in batch desorption process, and the use of 1N KSCN in 60% methanol attained a better performance (70% desorption). In the chromatography process with two pieces of 47 mm modified anion-exchange membrane discs (loading at 1 mL/min; washing and elution at 8 mL/min), more than 92% of dye molecules could be recovered from a 20 mL feed aqueous solution with an initial dye concentration of 0.05 g/L. Moreover, the membrane performance remained unaltered over 10 successive cycles of dye adsorption, washing, and elution.

A novel color removal adsorbent from heterocoagulation of cationic and anionic clays

We report the preparation and characterization of a novel nanocomposite adsorbent for anionic dye removal. The nanocomposite adsorbent was prepared by heterocoagulation of delaminated bentonite and layered double hydroxide (LDH) colloids. The effects of preparation conditions, LDH loading, particle size, and calcination temperature of the modified material on the physicochemical properties of this composite adsorbent have been investigated. The optimal conditions for best Reactive Yellow 2 (RY2) dye removal efficiency are a weight ratio of LDH to bentonite of 1:1, LDH particle size 100 nm, and calcination temperature 673 K. The adsorption equilibrium data can be fitted well by the widely accepted adsorption isotherm models.