Adsorption behavior of cationic dyes on citric acid esterifying wheat straw: kinetic and thermodynamic profile

The kinetic and thermodynamic behaviors of cationic dye adsorption onto citric acid esterifying wheat straw (EWS) from aqueous solution were investigated. Two cationic dyes, methylene blue (MB) and crystal violet (CV) were selected as adsorbates. The kinetic and thermodynamic parameters of dye adsorption were examined with a batch system by changing various experimental factors (e.g. initial pH, EWS dosage, dye concentration, contact time, temperature). The MB and CV removal ratios came up to the maximum value beyond pH 4. The 2.0 g/L or up of EWS could almost completely remove MB and CV from 250 mg/L of dye solution. The adsorption percentages of MB and CV kept above 95% over a range from 50 to 350 mg/L of dye concentration when 2.0 g/L of EWS was used. The isothermal data followed the Langmuir model. The adsorption processes could be described by the pseudosecond-order kinetic model. The dual linear plots of intraparticle diffusion indicated that two intraparticle diffusion steps occurred in the dye adsorption processes. The thermodynamic study indicated that the adsorptions of dyes were spontaneous and endothermic. High temperatures favored the adsorption processes.     

Application of Nano Surfactant Modified Biosorbent as an Efficient Adsorbent for Dye Removal

In the current study, sorption of methylene blue dye (MB) from aqueous solutions, using sawdust modified with sodium dodecyl sulfate (SDS/SD) has been investigated. Sorption experiments were performed using batch and fixed-bed column systems. The effects of important parameters, such as pH, initial dye concentration, flow rate, and bed depth on the sorption of MB dye have been studied. Thomas and the bed-depth service time model (BDST) were applied for analysis of sorption data and estimating of sorption capacity. In order to drive adsorption isotherms, sorption experiments were conducted in batch mode and the treatment of the obtained data were carried out using the Langmuir and Freundlich equations. Based on the breakthrough analysis obtained from continuous sorption experiments, the highest column capacity of 129.68 mg g^?1 was obtained for the SDS/SD adsorbent. The results of this study indicated that surfactant-modified sawdust is much more effective for basic MB dye removal compared to untreated sawdust (SD) and the exhausted SDS/SD column can be easily regenerated using dilute HCl solution with high performance (>95%). The results of this study also indicated the successful applicability of the introduced adsorbent as a very efficient and cost effective adsorbent for the removal of cationic dye molecules from aqueous wastes.     

Application of Modified Water Nut Carbon as a Sorbent in Congo Red and Malachite Green Dye Contaminated Wastewater Remediation

Batch and column adsorption experiments were conducted to investigate the removal of dyes from wastewater by water nut modified carbon (WNMC). Acidic pH was favorable for adsorption for Congo red dyes and basic pH was favorable for the adsorption for Malachite green dyes. The surface property of the sorbent was characterized by scanning electron microscopy and Fourier transform infrared techniques. The adsorption process was found to be endothermic and spontaneous. Different models of adsorption were used to describe the kinetics data and to calculate the corresponding rate constants of WNMC surfaces for dyes adsorption. A mechanism of dyes adsorption associating chemisorption processes is presented allowing the discussion of the variations in adsorption behavior of the material. These data suggested that WNMC are promising materials for dyes sorption. The data were in good agreement with bed depth service time model.     

Removal of plant poisoning dyes by adsorption on Tomato Plant Root and green carbon from aqueous solution and its recovery

The organic dyes directly pollute the soil, water, plants and all living systems in the environment. The dyes like cationic Methylene blue (MB) and Crystal violet (CV) adsorption has been studied on Tomato Plant Root powder (TPR) and green carbon from aqueous solution for identifying the plant poisoning nature of cationic dyes. TPR powder is a cellulose material and green carbon is prepared from TPR powder by an ecofriendly method. The dyes adsorption mechanism on basic surface of cellulose and neutral surface of green carbon are correlated to evaluate the plant poisoning nature of organic dyes. The adsorption parameters were optimized to maximum adsorption. The maximum uptake of both dyes on TPR was 97% at 15 min and on carbon is 18% (CV) & 20% (MB) at 30 min. The adsorptions of MB and CV on TPR powder followed Freundlich and Langmuir adsorption isotherms and pseudo second order kinetics. The ?S^o, ?H^o and ?G^o of adsorption on TPR are calculated. The dyes recovery has been studied from dyes adsorbed TPR and green carbon. The adsorption mechanism and dye recovery studies proved the plant poisoning nature of MB and CV.     

Removal of Selected Basic Dyes using Activated Carbon from Tannery Wastes

Activated carbon prepared from tannery leather waste (TLW-AC) has been studied for its efficiency of removal of basic dyes, namely rhodamine B (RB), methylene blue (MB), and malachite green (MG) from aqueous solutions. Factors influencing dye adsorption such as the concentration of dye, pH, contact time, and temperature were investigated. The adsorption was found to be strongly dependent on the pH and temperature. The maximum sorption capacity of RB was obtained at pH 3 and for MB and MG was obtained at pH 11. Various thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were calculated. The kinetic studies reveal that the adsorption process follows the pseudo second-order kinetic model. The equilibrium data have been well-described by the Langmuir and Freundlich models, and the data fitted well in both model equations. The study revealed that wastes from leather industry is an economically viable option for dye removal.     

Coniferous Wood Sawdust-based Activated Carbons as Adsorbents Obtained with the Use of Microwave Radiation

Activated carbons were prepared by physical and direct activation of sawdust pellets coming from coniferous trees, with the use of microwave radiation. The activated carbons obtained were used as adsorbents for the removal of methylene blue (MB) from aqueous solutions. Liquid-phase adsorption experiments were conducted and the maximum adsorption capacity of each activated carbon sample was determined. The effects of activation procedure as well as adsorption tests parameters i.e., temperature, pH, initial methylene blue concentration, and contact time on the sorption capacity of each activated carbon were investigated. The kinetic models for MB adsorption on the activated carbons were also studied. Better fit to the experimental data was obtained with the Langmuir isotherm than Freundlich one, for all samples.     

High-Efficiency Sorbent for Dyes Based on Cellulose Resin Crosslinked with Perylene Tetracarboxylic Diimides

The novel cellulose resin crosslinked with perylene tetracarboxylic diimides 3 was synthesized and its structure was characterized by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, and scanning electronmicroscopy (SEM), etc. Dyes adsorption experiments of polymer 3 suggested that it exhibited excellent adsorption capacities for tested four cationic and anionic dyes [Orange G sodium salt (OG), Brilliant ponceau 5R (BP), Methylene blue (MB), and Crystal violet (CV)]. The adsorption capacities for OG, BP, MB, CV were as high as 1.04, 1.21, 1.14, and 0.96 mmol/g, respectively. The adsorption processes obeyed the pseudo second-order model and followed the Langmuir isotherm equation. The adsorption processes were exothermic and spontaneous. The pH = 2 ? 12 made slight influences on adsorption capacities of polymer 3 for dyes. It was supposed that the adsorption mechanism was not only the electrostatic forces and hydrogen bond but also the π-π stacking interaction playing an important role in the adsorption processes.     

Strongly basic anion exchanger Lewatit MonoPlus SR-7 for acid,reactive, and direct dyes removal from wastewaters

The strongly basic anion exchanger Lewatit MonoPlus SR-7 (SR-7) of polystyrene matrix was applied for removal of the textile dyes such as C.I. Acid Orange 7 (AO7), C.I. Reactive Black 5 (RB5), and C.I. Direct Blue 71 (DB71). The dyes sorption on SR-7 was examined based on the initial dye concentration, phase contact time, type of additives and their concentrations, and solution pH. The equilibrium and kinetic characteristics of the dyes uptake by SR-7 followed the Langmuir isotherm model and the pseudo-second-order model. The dyes sorption in the column system was also investigated.     

Diffusion and sorption studies of dyes through PVA cryogel membranes

The capacity of poly(vinyl alcohol) (PVA) to crosslink through freeze/thaw method was used to obtain PVA hydrogel membranes (HG) that were subjected to sorption and diffusion experiments using three dyes: Congo red (CR), methylthymol blue (MTB), and crystal violet (CV). To study the sorption of dyes into the cryogenic membrane, dye solutions at different concentrations were used. After sorption, desorption of dyes from the PVA membrane was monitored to quantify the possible regeneration of the membrane (PVA HG). To have a deep insight on the mechanism behind the desorption process, dye‐release kinetics were studied. The diffusion experiments reveal the fact that CR and MTB do not permeate the PVA HG membrane making it a promising candidate in the advanced purification processes of wastewaters. The effect of the incorporation of dyes (CV, CR, and MTB) on the chemical properties of PVA cryogel matrices has been studied by using several techniques such as: differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of bis[2-(methacryloyloxy)ethyl] phosphate as a crosslinker on poly(AAm-co-AMPS)/Na-MMT hydrogel nanocomposite as potential adsorbent for dyes: kinetic,isotherm and thermodynamic study

In the present study, synthesis of poly(AAm-co-AMPS)/Na-MMT hydrogel nanocomposite with different amount of bis[2-(methacryloyloxy)ethyl] phosphate as a crosslinker was successfully carried out for the removal of crystal violet (CV), methylene blue (MB) and methyl red (MR) from aqueous solution. Hydrogel nanocomposite was characterized by FT-IR, SEM, EDS, XRD and TGA analysis. Several important parameters were investigated to obtain maximum adsorption capacity. Adsorption behavior of hydrogel nanocomposite was investigated for the adsorption of dyes and it was found to remove about 80% for CV, 89% for MB and 51% for MR in 50 mg/L of dyes solutions at pH 7 and about 86% for CV, 93% for MB and 23% for MR at pH 12. Kinetic studies revealed that the applicability of pseudo-first-order and pseudo-second-order model for the adsorption of CV, MB and MR. The adsorption isotherm was studied in 25, 35, 45 and 55 °C using Langmuir, Freundlich, Temkin and Jovanovic models and the adsorption data were well described by Freundlich isotherm model. Hydrogel nanocomposite showed 155, 176 and 113 mg/g maximum adsorption capacity for CV, MB and MR respectively. Negative values of ΔG⁰ for all three dyes suggested the feasibility of dyes removal and support for spontaneous adsorption of CV, MB and MR on hydrogel nanocomposite. Desorption of dyes from the dye loaded hydrogel nanocomposite was simply done in ethanol. The results indicate that the prepared poly(AAm-co-AMPS)/Na-MMT hydrogel nanocomposite is an efficient adsorbent with high adsorption capacity for the aforementioned dyes.

Open image in new window

Graphical abstract Graphical abstract illustrating the preparation and dye adsorption processes of the poly(AAm-co-AMPS)/Na-MMT hydrogel nanocomposite

     

The effect of pH and temperature on the dye sorption of wool powders

The sorption behavior of wool powders for three acid dyes (C. I. Acid Red 88, C. I. Acid Red 13 and C. I. Acid Red 18) and a basic dye (methylene blue) was investigated as a function of pH and temperature. The sorption capacity of wool powders depends on the pH of dye solution. The maximum uptake of acid dyes and methylene blue by wool powders occurred at pH 2.5 and pH 7.5, respectively. The effect of pH on the sorption of the hydrophilic dyes (C. I. Acid Red 13 and C. I. Acid Red 18) was more significant than that of the uptake of the hydrophobic dye (C. I. Acid Red 88). Increasing temperature enhanced the dye sorption ability of coarse wool powders, but did not impact that of fine wool powders. The dye‐absorption models of wool powders agree with the Langmuir isotherm. Comparison to activated charcoal and other sorbents indicates that fine wool powders have excellent dye sorption capacity even at room temperature, and may be used as a potential sorbent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Adsorption of Anionic and Cationic Dyes from Aqueous Solution on Non-Calcined Mg-Al Layered Double Hydroxide: Experimental and Theoretical Study

Non-calcined Mg-Al layered double hydroxide (LDH) with Mg/Al molar ratio of 3:1 was synthesized using the co-precipitation method. Sorption of anionic (acid blue 25 - AB25, reactive blue 4 - RB4), and cationic (methylene blue - MB) dyes by Mg-Al LDH form aqueous solution was investigated. The effect of solution pH, initial concentration, and contact time were investigated by batch adsorption experiments. The adsorbed amount increases with decrease in pH solution for AB25 and RB4. The cationic dye (MB) solution was insensitive to pH variation and also exhibited a low performance in the kinetic equilibrium studies. While anionic dyes were almost completely extracted from the solution, 90% of the methylene blue remained in solution. The equilibrium data were well described using the Langmuir-Freundlich model for RB4, AB25, and MB dyes with maximum adsorption capacity of 328.90, 246.10, and 43.48 mg/g, respectively. Finally, the mechanism of adsorption involving the dyes and LDH was evaluated using the Monte Carlo approach in the NVT ensemble. The results suggest that molecular simulation can be used to preview quantitatively the dye uptake. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the supplemental file.     

Synthesis and characterization of PET fibers grafted with binary mixture of 2-methylpropenoic acid and acrylonitrile by free radical: its application in removal of cationic dye

Grafting of binary vinyl monomer mixtures such as 2-methylpropenoic acid (MPA) and acrylonitrile (AN) onto poly (ethylene terephthalate) fibers (PET) was achieved in an aqueous medium with using benzoyl peroxide like free radical initiator. A new reactively fibrous adsorbent was used for removal of dye such as methylene blue (MB) from aqueous media through batch sorption method. Fibers adsorbent was swelled in solution to support the graft and the subsequent polymerization of MPA/AN onto polyester fibers. Optimum conditions for grafting were discovered and reactive fiber were characterized. Variations of graft yield with time, temperature, initiator concentration and monomer mixture ratio were investigated. The optimum initiator concentration was found to be 8 × 10^?3 mol/L. The percentage of grafting rose steadily with the vinyl monomer mixture monomer concentration (50 %). The optimum temperature and polymerization time were found to be 80 °C and 120 min, respectively. The use of AN and MPA monomers together in grafting produce a significant increased in the graft yield. Experimental studies showed that the percentage removal of MB was a great higher on the MPA/AN grafted PET (MPA/AN-g-PET) fibers than on the original PET fibers. The adsorbed quantity of MB improved with pH and basic pH was appropriate for the elimination of MB. MPA/AN-g-PET fibers removed 98 % of cationic dye when initial concentration diverse from 10 to 80 mg L^?1 at pH 9.0. Almost all of the adsorbed cationic dye was eluted by ethanoic acid in methanol. Ten removal–desorption cycles indicated that the reactive fibers were favorable for repetitive use without notable change in removal capacity. Consequently, the MPA/AN-g-PET fibers have demonstrated potential as an effective adsorbent for the extremely effective removal of cationic dyes from aqueous media.     

Effect of deacetylation on sorption of dyes and chromium on chitin

Deacetylated chitins (10.7–67.2%) were prepared by alkaline hydrolysis to determine an optimal degree of deacetylation (DD) which can effectively remove four dyes and chromium ions from textile effluent. Sorption isotherms were carried by varying the treatment time, pH, and initial concentration of dyes or chromium ions. Experimental results were analyzed in three ways: (1) equilibrium sorption capacity and sorption rate constant, (2) Langmuir isotherms, and (3) separation factor. Results indicated that except for the chitin with a 67.2% DD, rate and capacity of the dye sorption on the chitin increased with the increase of the DD in chitin for each pH but decreased with the increase of pH for each deacetylated chitin. This was mainly due to the increase of—NH⁺₃ groups in chitin with a high DD and the low pH of the system. On the contrary, dye desorption from the deacetylated chitin was highly effective at 80° and pH ≥ 10, which could facilitate the reduction of—NH⁺₃ ions and the increase of electrostatic repulsion. The number of chromium ions sorbed on the chitin also increased with the increase of the DD at a specific time. Therefore, by controlling the DD of the deacetylated chitin maximum efficiency can be achieved in the removal of dyes and metal ions from textile effluent.     

Saccharomyces cerevisiae for the biosorption of basic dyes from binary component systems and the high order derivative spectrophotometric method for simultaneous analysis of Brilliant green and Methylene blue

In this work, biosorption of Brilliant green (BG) and Methylene blue (MB) dyes in binary mixture onto Saccharomyces cerevisiae were studied. pH at which the biosorption capacity of biomass is maximum was found to be 6 which is close to the pH of natural aqueous solutions. This is a big advantage of S. cerevisiae which makes it applicable for the technology of dye removal from natural aqueous dye solutions. Note that the time for the applied biosorption process for the dye removal is considerably short (about 5 min) which is a big improvement for the adsorption processes. This proves that the S. cerevisiae is a promising adsorbent. The BG and MB dyes were simultaneously analyzed using the fifth and fourth order derivative spectrophotometric method, respectively. Several isotherm models were applied to experimental data and the isotherm constants were calculated for BG and MB dyes. Among the applied models, Freundlich isotherm model showed best fit to the biosorption equilibrium data.     

Weak base polystyrene anion exchangers II Relation between their structure and structure of sorbates

The influence of the structure of styrene-divinylbenzene copolymers, which make up the matrix of weak base anion exchangers with mono- and diethanolamine functional groups on their sorption properties in relation to acid dyes with increasing molecule size has been investigated. It has been found that the copolymer gel heterogeneity induced by the presence of an inert diluent has a marked effect on the degree of sorption and its course. The acid dyes with a higher sulfonic group content were found to be sorbed mainly by the formation of aggregates in the ion exchanger, and the homogeneity of their structure facilitates the process.     

Adsorption kinetics and mechanism of cationic methyl violet and methylene blue dyes onto sepiolite

The use of low-cost and ecofriendly adsorbents was investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. Sepiolite was used as an adsorbent for the removal of methyl violet (MV) and methylene blue (MB) from aqueous solutions. The rate of adsorption was investigated under various parameters such as contact time, stirring speed, ionic strength, pH and temperature for the removal of these dyes. Kinetic study showed that the adsorption of dyes on sepiolite was a gradual process. Quasi-equilibrium reached within 3 h. Adsorption rate increased with the increase in ionic strength, pH and temperature. Pseudo-first-order, the Elvoich equation, pseudo-second-order, mass transfer and intra-particle diffusion models were used to fit the experimental data. The sorption kinetics of MV and MB onto sepiolite was described by the pseudo-second-order kinetic equation. Intra-particle diffusion process was identified as the main mechanism controlling the rate of the dye sorption. The diffusion coefficient, D, was found to increase when the ionic strength, pH and temperature were raised. Thermodynamic activation parameters such as ΔG¹, ΔS¹ and ΔH¹ were also calculated.     

Removal of basic dyes from aqueous solution by low-cost adsorbent: Wood apple shell (Feronia acidissima)

The adsorption of two basic dyes, methylene blue (MB) and crystal violet (CV) on wood apple shell (WAS) were investigated using a batch adsorption technique. A series of experiments were undertaken in an agitated batch adsorber to assess the effect of the system variables such as solution pH, dye concentration and temperature. Removal of dyes was observed to be most effective at higher pH. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The results showed that Langmuir equation fits better than the Freundlich equation. It was observed that the WAS adsorbent showed higher adsorption capacity for crystal violet (130 mg/g) than methylene blue (95.2 mg/g). The FTIR studies indicate that the interaction of dye and WAS surface is via the nitrogen atoms of the adsorbate and oxygen groups of the adsorbent. The adsorption of dyes onto WAS proceeds according to a pseudo-second-order model. Thermodynamic parameters such as free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were also calculated. The studies show that WAS, a lignocellulosic inexpensive material, can be an alternative to other expensive adsorbents used for dye removal in wastewater treatment.     

竹屑基吸附材料的制备及吸附行为研究

以竹加工废屑为原料,采用汽爆碱煮法制备了一种竹屑基吸附材料（Bamboo-basedadsorbent-BA）。通过吸附实验研究了BA对三种碱性染料废水的吸附脱色效果并探究其吸附行为及其机理。吸附和解吸实验表明,BA对染料分子的吸附是基于分子间静电引力和氢键的共同作用,脱色效果随体系pH和温度的上升而提高。热力学参数显示该吸附是一个自发、吸热和熵增过程。吸附行为可以很好地用准二级动力学方程描述,而吸附等温线用Langmuir方程拟合效果最优。BA对亚甲基蓝、结晶紫和孔雀石绿三种染料的最大吸附量分别为135．9、129．2和83.3mg／g。     

Removal of cationic dye from aqueous solution by adsorption onto crosslinked poly(4-vinylpyridine/crotonic acid) and its N-oxide derivative

In this study, crosslinked poly(4-vinylpyridine/crotonic acid) [poly(4-VPy/CrA)] and its N-oxide derivative were synthesized to compare the adsorption of cationic methylene blue (MB) dye on these materials. The adsorptive removal of MB from aqueous solution onto adsorbents was studied by using column adsorption method. Experimental results showed that MB was removed more effective by poly(4-VPy/CrA)–N-oxide than poly(4-VPy/CrA) resins. The percentage removal of MB increased with pH, and it was observed that basic pH was favorable for the adsorption of MB. The adsorption capacity for poly(4-VPy/CrA)–N-oxide resin was found to 19.96 mg/g. It was found that the adsorption isotherm of the MB-fitted Langmuir-type isotherm. For the adsorption of MB, the pseudo-second-order chemical reaction kinetics provides the best correlation with the experimental data. Ten adsorption–desorption cycles demonstrated that the resins were suitable for repeated use without considerable change in adsorption capacity.