Cross-linked quaternary chitosan as an adsorbent for the removal of the reactive dye from aqueous solutions

Adsorption of reactive orange 16 by quaternary chitosan salt (QCS) was used as a model to demonstrate the removal of reactive dyes from textile effluents. The polymer was characterized by infrared (IR), energy dispersive X-ray spectrometry (EDXS) analyses and amount of quaternary ammonium groups. The adsorption experiments were conducted at different pH values and initial dye concentrations. Adsorption was shown to be independent of solution pH. Three kinetic adsorption models were tested: pseudo-first-order, pseudo-second-order and intraparticle diffusion. The experimental data best fitted the pseudo-second-order model, which provided a constant velocity, k₂, of 9.18 × 10⁻⁴ g mg⁻¹ min⁻¹ for a 500 mg L⁻¹ solution and a value of k₂, of 2.70 × 10⁻⁵ g mg⁻¹ min⁻¹ for a 1000 mg L⁻¹ solution. The adsorption rate was dependent on dye concentration at the surface of the adsorbent for each time period and on the amount of dye adsorbed. The Langmuir isotherm model provided the best fit to the equilibrium data in the concentration range investigated and from the isotherm linear equation, the maximum adsorption capacity determined was 1060 mg of reactive dye per gram of adsorbent, corresponding to 75% occupation of the adsorption sites. The results obtained demonstrate that the adsorbent material could be utilized to remove dyes from textile effluents independent of the pH of the aqueous medium.     

A novel agricultural waste adsorbent for the removal of cationic dye from aqueous solutions

In this paper, pineapple stem (PS) waste, an agricultural waste available in large quantity in Malaysia, was utilized as low-cost adsorbent to remove basic dye (methylene blue, MB) from aqueous solution by adsorption. Batch mode experiments were conducted at 30 degrees C to study the effects of initial concentration of methylene blue, contact time and pH on dye adsorption. Equilibrium adsorption isotherms and kinetic were investigated. The experimental data were analyzed by the Langmuir and Freundlich models and the isotherm data fitted well to the Langmuir isotherm with monolayer adsorption capacity of 119.05mg/g. The kinetic data obtained at different concentrations were analyzed using a pseudo-first-order and pseudo-second-order equation and intraparticle diffusion equation. The experimental data fitted very well the pseudo-second-order kinetic model. The PS was found to be very effective adsorbent for MB adsorption.     

Poly(acrylamide) functionalized chitosan: An efficient adsorbent for azo dyes from aqueous solutions

In the present communication we report on the optimization of persulfate/ascorbic acid initiated synthesis of chitosan-graft-poly(acrylamide) (Ch-g-PAM) and its application in the removal of azo dyes. The optimum yield of the copolymer was obtained using 16 × 10⁻² M acrylamide, 3.0 × 10⁻² M ascorbic acid, 2.4 × 10⁻³ M K₂S₂O₈ and 0.1 g chitosan in 25 mL of 5% aqueous formic acid at 45 ± 0.2 °C. Ch-g-PAM remained water insoluble even under highly acidic conditions and could efficiently remove Remazol violet and Procion yellow dyes from the aqueous solutions over a pH range of 3–8 in contrast to chitosan (Ch) which showed pH dependent adsorption. The adsorption data of the Ch-g-PAM and Ch for both the dyes were modeled by Langmuir and Freundlich isotherms where the data fitted better to Langmuir isotherms. To understand the adsorption behavior of Ch-g-PAM, adsorption of Remazol violet on to the copolymer was optimized and the kinetic and thermodynamic studies were carried out taking Ch as reference. Both Ch-g-PAM and Ch followed pseudo-second-order adsorption kinetics. The thermodynamic study revealed a positive heat of adsorption (ΔH°), a positive ΔS° and a negative ΔG°, indicating spontaneous and endothermic nature of the adsorption of RV dye on to the Ch-g-PAM. The Ch-g-PAM was found to be very efficient in removing color from real industrial wastewater as well, though the interfering ions present in the wastewater slightly hindered its adsorption capacity. The data from regeneration efficiencies for ten cycles evidenced the high reusability of the copolymer in the treatment of waste water laden with even high concentrations of dye.     

An effective adsorbent based on sawdust for removal of direct dye from aqueous solutions

Sawdust, SD, was reacted with Sandene 850 (polyamine) in alkaline medium to yield cationized sawdust. The latter was characterized through its Fourier Transform Infrared (FT-IR) spectra and nitrogen content. Thus, obtained cationized sawdust was harnessed for removal of Direct Red 23 from aqueous solutions. Adsorption studies were performed under different agitation time, adsorbent and adsorbate concentrations and the onset of this on the adsorption capacity of Direct Red 23 onto cationized sawdust. Langmuir and Freundlich models were applied in the adsorption studies. The study showed that the cationized sawdust is effectively used in adsorption of Direct Red 23 from aqueous solutions.     

Water-soluble magnetic-graphene nanocomposites: Use as high-performance adsorbent for removal of dye pollutants

In this study, the water-soluble magnetic-graphene nanocomposites (Fe₃O₄@GNs-SO₃H) were fabricated via a simple and efficient approach. The water-soluble magnetic-graphene nanocomposites were applied as an effective adsorbent for removal of organic dye, malachite green, from aqueous solution. It is noteworthy that the nanocomposites displayed good water-dispersibility, rapid absorption rate, high absorption capacity, and convenient magnetic separation. Furthermore, the novel adsorbent could be recovered and recycled for 15 consecutive trials without significant loss of its activity.     

Investigation of cationic starch/Na-montmorillonite bionanocomposite adsorbent prepared by vibration milling for acid dye removal

In this study, the low-cost powder bionanocomposite based on cationic starch (CS) and Na-montmorillonite (MMT) was obtained by the one-step procedure in a homemade vibration mill. The analysis of the bionanocomposite by x-ray diffraction (XRD) and thermogravimetric analysis (TGA) methods revealed that MMT had intercalated structure in CS matrix and the bionanocomposite possessed enhanced thermal stability as compared with that of pure CS. Adsorption capacity of CS/MMT bionanocomposite toward Acid Scarlet dye was evaluated as a function of initial dye concentration and contact time. The adsorption tests showed that the adsorption kinetics followed the pseudo-second order chemisorptions kinetic model. The adsorptions isotherms were best fitted using the three-parameter Sips model with the maximum adsorption capacity of 43.7 mg/g for CS/MMT bionanocomposite against 13.4 mg/g for CS.     

Simultaneous removal of chromium and leather dye from simulated tannery effluent by photoelectrochemistry

The feasibility of the photobleaching of a leather acid dye, acid red 151, simultaneously to degradation of anionic surfactant, Tamol^®, and reduction of Cr(VI) to the less toxic Cr(III) was investigated by photoelectrocatalytic oxidation. The best experimental conditions were found to be pH 2.0 and 0.1 mol L⁻¹ sodium sulfate when the nanoporous Ti/TiO₂ photo anode was biased at +1.0 V and submitted to UV-irradiation. The photoelectrocatalytic oxidation promotes 100% discoloration, reducing around 98–100% of Cr(VI) and achieving an abatement of 95% of the original total organic carbon. The effect of pH, the applied potential, the Cr(VI) concentration and the complexation reaction between Cr(VI) and acid red dye were evaluated as to their effect on the kinetics of the reaction.     

Spent tea leaves: a new non-conventional and low-cost adsorbent for removal of basic dye from aqueous solutions

In the present study, spent tea leaves (STL) were used as a new non-conventional and low-cost adsorbent for the cationic dye (methylene blue) adsorption in a batch process at 30 degrees C. Equilibrium sorption isotherms and kinetics were investigated. The experimental data were analyzed by the Langmuir, Freundlich and Temkin models of adsorption. The adsorption isotherm data were fitted well to the Langmuir isotherm and the monolayer adsorption capacity was found to be 300.052mg/g at 30 degrees C. The kinetic data obtained at different initial concentrations were analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion equations. The results revealed that the spent tea leaves, being waste, have the potential to be used as a low-cost adsorbent for the removal of methylene blue from aqueous solutions.     

Oxygen functionalized carbon nanocomposite derived from natural illite as adsorbent for removal of cationic and anionic dyes

Oxygen functionalized carbon nanocompositse (O-I@C) based on glucose and illite were obtained through mild hydrothermal process and surface oxidation. The surface properties of the prepared O-I@C were analyzed by Boehm titration, scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and Specific surface area (BET). The results showed that the surfaces of the prepared O-I@C nanocomposites were functionalized with abundant oxygen-containing functional groups (OFGs). The functionalized O-I@C nanocomposites were proven to be effective adsorbents for fast removal of congo red (CR) and methylene blue (MB) from aqueous solution within 10 min. It is demonstrated that the initial pH of dyes solution has an important influence on the adsorption process of both CR and MB, indicating that the OFGs created on the surfaces of the materials are responsible for the promoted adsorption ability. Furthermore, it is also proved that the adsorption isotherms of CR and MB obey the Langmuir model, with the maximum adsorption capacities of 238.40 mg/g and 215.28 mg/g, respectively. In addition, the used materials could be regenerated by washing with NaOH solution and reused at least four times, which exhibits potential applications as efficient and easily reusable adsorbents for the rapid removal of anionic dye CR and cationic dye MB from wastewater.     

One-step processing of low-cost and superb natural magnetic adsorbent: kinetics and thermodynamics investigation for dye removal from textile wastewater

A simple, one-step and dry hybridization technique was successfully implemented to fabricate superb and low-cost magnetic adsorbent for removal of organic dyes. The structural and textural properties of the prepared banded iron formation @bentonite (BIF@BEN) composite were clearly investigated using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS), Brunauer–Emmett–Teller surface area (BET) and porosity analysis (BJH) techniques. The dye removal efficiency was optimized by studying several parameters, namely, pH, temperature, contact time and initial dye concentration. The maximum adsorption capacity achieved for crystal violet (CV) and acid red (AR) dyes were about 117 and 91 mg/g, respectively at pH 7, 60 °C in 60 min. The equilibrium data of both dyes’ adsorption on the BIF@BEN composite showed better fitting to Langmuir isotherm. The thermodynamic studies revealed that the adsorption process is spontaneous, endothermic and favorable at high temperatures. The prepared magnetic adsorbent showed higher adsorption performance than activated bentonite for removal of anionic dye (AR) and the same performance for removal of cationic dye (CV). The magnetic adsorbent is actually reused and easily separated from textile wastewater with total removal efficiencies 81% and 74.5% for all inorganic and organic pollutants, respectively after two adsorption cycles.     

Sunflower seed shells: a novel and effective low-cost adsorbent for the removal of the diazo dye Reactive Black 5 from aqueous solutions

In this paper, the potential of two low-cost adsorbents such as sunflower seed shells (SS) and mandarin peelings (MP) in the removal of the synthetic anionic dye Reactive Black 5 (RB5) from aqueous solutions was investigated. SS led to a percentage of dye removal higher than MP (85% and 71% after 210min, respectively, for an initial RB5 concentration of 50mgL(-1) and an initial pH of 2.0). The rate of adsorption followed a pseudo-second-order kinetic model and the intra-particle diffusion was found to be the rate-controlling stage. In addition, the equilibrium data fitted well both the Freundlich and multilayer adsorption isotherm equations indicating the heterogeneity of the adsorbent surface. This was also corroborated by the SEM photographs. On the whole, the results in this study indicated that SS were very attractive materials for removing anionic dyes from dyed effluents.     

Environmentally stable adsorbent of tetrahedral silica and non-tetrahedral alumina for removal and recovery of malachite green dye from aqueous solution

The conventional adsorbents like activated carbon, agricultural wastes, molecular sieves, etc., used for dye adsorption are unstable in the environment for long time, and hence the adsorbed dyes again gets liberated and pollute the environment. To avoid this problem, environmentally stable adsorbent of silica and alumina should be employed for malachite green adsorption. The adsorbents were characterized by Fourier transformed infrared spectroscopy (FT-IR) to confirm the tetrahedral framework of silica and non-tetrahedral framework of alumina. The adsorption equilibrium of dye on alumina and silica were 4 and 5h, respectively, this less adsorption time on alumina might be due to the less activation energy on alumina (63.46 kJ mol(-1)) than silica (69.93 kJ mol(-1)). Adsorption increased with increase of temperature on silica, in alumina, adsorption increased up to 60 degrees C, and further increase of temperature decreased the adsorption due to the structural change of non-tetrahedral alumina in water. The optimum pH for dye adsorption on alumina was 5 and silica was 6. The dye adsorptions on both adsorbents followed pseudo-second-order kinetics. The adsorption well matched with Langmuir and Freundlich adsorption isotherms and found that adsorption capacity on alumina was more than silica. The thermodynamic studies proved that the adsorption was endothermic and chemisorptions (DeltaH degrees >40 kJ mol(-1)) on alumina and silica. Recovery of dye on alumina and silica were studied from 30 to 90 degrees C and observed that 52% of dye was recovered from alumina and only 3.5% from silica. The less recovery on silica proved the strong adsorption of dye on silica than alumina.     

Nanoalumina-supported Mn2O3 as efficient adsorbent for removal of fluoride and arsenic from water: a study from lab to field

Journal of Materials Science - Water pollution with heavy metals has been a problem for the environment and human health. The cohabitation of As(III) and fluoride in groundwater has gotten...     

Co3O4 doped over SBA 15: excellent adsorbent materials for the removal of methyleneblue dye Pollutant

Nanosized cobalt oxide particles are incorporated into SBA 15 mesoporous silica materials and are effectively used for the first time as adsorbent materials for aquatic dye pollutant removal. Cobalt is found to exist in its Co₃O₄ spinel structure as evident from FTIR and X-ray diffraction studies. The best weight ratio of metal loading to show excellent adsorption of methyleneblue is found to be 10 wt% Co over the support. There, Co₃O₄ spinel nanoparticles lie inside the pores of mesoporous silica. Further increase in the percentage of metal loading decreases the adsorption capacity which may be due to the agglomeration of nanoparticles over the silica support as evident from TEM photographs. Cobalt-doped systems of the present study, having good adsorption capacity of methyleneblue, are prepared via impregnation of cobalt nitrate over SBA 15 in aqueous medium. Here, we introduce a new SBA 15-based system for the fast removal of aquatic dye pollutants which is highly economical for industrial applications.     

Use of hen feathers as potential adsorbent for the removal of a hazardous dye, Brilliant Blue FCF, from wastewater

Waste material, hen feather, a biosorbent, was successfully utilized in removing a water-soluble hazardous triphenylmethane dye, Brilliant Blue FCF from wastewater. The paper incorporates effect of pH, temperature, amount of adsorbent, contact time, concentration of adsorbate, etc. The adsorption data validates Langmuir and Freundlich adsorption isotherms and on the basis of these isotherms thermodynamic parameters like Gibb's free energy, change in enthalpy and entropy were calculated. Kinetics of the ongoing adsorption was also monitored and specific rate constants for the involved process were calculated at different temperatures. Kinetic measurements suggest a first order adsorption kinetics and adsorption was found to be applicable via film diffusion process in the entire concentration range.     

Grape bagasse as an alternative natural adsorbent of cadmium and lead for effluent treatment

This work investigated the utilization of grape bagasse as an alternative natural adsorbent to remove Cd(II) and Pb(II) ions from laboratory effluent. X-ray diffractometry, Fourier transform infrared spectroscopy, scanning electron microscopy, nuclear magnetic resonance, thermogravimetric analyses, surface analysis, porosity and porous size were used for characterization of the material. Batch experiments were carried out to evaluate the adsorption capacity of the material. Parameters such as adsorption pH and contact time were optimized for the maximum accumulation onto the solid surface. The pH values found were 7 and 3 for Cd(II) and Pb(II), respectively, and contact time was 5 min for both metals. Adsorption capacity for metals were calculated from adsorption isotherms by applying the Langmüir model and found to be 0.774 and 0.428 mmol g(-1) for Cd(II) and Pb(II), respectively. The competition between metals for the same adsorption sites on grape bagasse was also evaluated, showing an increasing affinity for Pb(II) over Cd(II) when only these metals are present. The potential of this material was demonstrated by efficient metal removal from laboratory effluent using a glass column. The results indicate that the referred material could be employed as adsorbent for effluent treatment, especially due to its easy acquisition and low cost as well as the fast adsorption involved.     

Hydrated cement: a promising adsorbent for the removal of fluoride from aqueous solution

The present study was carried out to investigate the potential of cement hydrated at various time intervals for the removal of excess F- from aqueous solution by using batch adsorption studies. The influence of different adsorption parameters, viz. effect of adsorbent dose, initial concentration, pH, interfering ions and contact time were studied for their optimization. It was observed that the adsorbent exhibited reasonably significant F- removal over a wide range of pH. The presence of carbonate and bicarbonate ions in aqueous solution were found to affect the F- removal indicating that these anions compete with the sorption of F- on adsorbent. The equilibrium adsorption data were fitted well for both the Freundlich and Langmuir isotherms and the adsorption capacities were calculated. Comparative studies for F- removal in simulated and field water show relatively higher F- removal in simulated water. XRD and SEM patterns of the hydrated cement were recorded to get better insight into the mechanism of adsorption process. From the experimental results, it may be concluded that HC was an efficient and economical adsorbent for F- removal.     

Characterisation and environmental application of an Australian natural zeolite for basic dye removal from aqueous solution

An Australian natural zeolite was collected, characterised and employed for basic dye adsorption in aqueous solution. The natural zeolite is mainly composed of clinoptiloite, quartz and mordenite and has cation-exchange capacity of 120 meq/100g. The natural zeolite presents higher adsorption capacity for methylene blue than rhodamine B with the maximal adsorption capacity of 2.8 x 10(-5) and 7.9 x 10(-5)mol/g at 50 degrees C for rhodamine B and methylene blue, respectively. Kinetic studies indicated that the adsorption followed the pseudo second-order kinetics and could be described as two-stage diffusion process. The adsorption isotherm could be fitted by the Langmuir and Freundlich models. Thermodynamic calculations showed that the adsorption is endothermic process with Delta H(0) at 2.0 and 8.7 kJ/mol for rhodamine B and methylene blue. It has also found that the regenerated zeolites by high-temperature calcination and Fenton oxidation showed similar adsorption capacity but lower than the fresh sample. Only 60% capacity could be recovered by the two regeneration techniques.     

Heulandite/polyaniline hybrid composite for efficient removal of acidic dye from water; kinetic,equilibrium studies and statistical optimization

Heulandite/polyaniline (HU/PANI) composite was prepared by mechanical mixing from natural heulandite and synthesized polyaniline. HU/PANI was characterized by XRD, SEM, TEM, FT-IR, and UV–Vis spectroscopy. The product is of polycrystalline nature with an average crystallite size of 25.7?nm and optical band gap of 1.69?eV. HU/PANI shows higher efficiency in the removal of light green SF dye than natural HU or PANI in the dark and under artificial illumination. The equilibrium time was attained after 360 and 480?min in the dark and under illumination, respectively. The results fitted well with pseudo second order and Elovich kinetic models. The adsorption isotherm in the dark fitted well with Langmuir isotherm model and the calculated q_max was 44.6?mg/g. Using illumination, the data fitted better with the Freundlich and Temkin model than with the Langmuir model. Based on response surface analysis, the predicted conditions for maximum removal of light green SF dye in the dark (70.9%) were 5.5?mg/L, 24?mg, 3, and 430?min for dye concentration, HU/PANI dose, pH, and contact time, respectively. Whereas, under light illumination (97%) at operating conditions of 15?mg/L, 15?mg, 3, and 589?min, respectively. The composite also shows high efficiencies in the removal of other types of acidic and basic dyes.