Comparison of Basic Dye Crystal Violet Removal from Aqueous Solution by Low-Cost Biosorbents

Abstract

The removal of basic dye crystal violet by low-cost biosorbents was investigated in this study using a batch experimental system. The adsorption of crystal violet onto various adsorbents was solution pH-dependent and the maximum removal occurred at basic pH 10.0. The kinetic experimental data were analyzed using pseudo-first-order and pseudo-second-order equations to examine the adsorption mechanism and the intraparticle diffusion model to identify the potential rate controlling step. These results suggested that the adsorption of crystal violet onto various adsorbents was best represented by the pseudo-second-order equation. The suitability of the Langmuir and Freundich adsorption isotherms to the equilibrium data was also investigated at various temperatures for all four sorbents and the adsorption isotherms exhibited Freundlich behavior. The Freundlich constant K_f was 1.55 for alligator weed, 2.33 for Laminaria japonica, 9.59 for rice bran and 5.38 (mg/g)/(mg/L)^1/n for wheat bran, respectively at adsorbent concentration 5 g/L, pH 10.0 and 20°C. The thermodynamic parameters (ΔH, ΔG, and ΔS) were calculated and the results showed that the adsorption process for various adsorbents was spontaneous, endothermic, with an increased randomness, respectively. The particle size and the reaction temperature exhibited an insignificant impact on the adsorption equilibrium of crystal violet. The adsorbents investigated could serve as low-cost adsorbents for removing the crystal violet from aqueous solution.     

Comparative study of methylene blue dye adsorption onto activated carbon,graphene oxide,and carbon nanotubes

Three different carbonaceous materials, activated carbon, graphene oxide, and multi-walled carbon nanotubes, were modified by nitric acid and used as adsorbents for the removal of methylene blue dye from aqueous solution. The adsorbents were characterized by N₂ adsorption/desorption isotherms, infrared spectroscopy, particle size, and zeta potential measurements. Batch adsorption experiments were carried out to study the effect of solution pH and contact time on dye adsorption properties. The kinetic studies showed that the adsorption data followed a pseudo second-order kinetic model. The isotherm analysis indicated that the adsorption data can be represented by Langmuir isotherm model. The remarkably strong adsorption capacity normalized by the BET surface area of graphene oxide and carbon nanotubes can be attributed to π–π electron donor acceptor interaction and electrostatic attraction.     

Use of CaCl2 modified bentonite for removal of Congo red dye from aqueous solutions

CaCl₂ modified bentonite (BCa²⁺), a clean and cost-effective adsorbent with a basal spacing of 15.43 Å, was prepared for the removal of Congo red dye from water. It was effective for the removal of Congo red with a high adsorption capacity, and the adsorption was favored over a broad pH range (5-10). The pseudo-second-order kinetic model provided the best correlation of the experimental data. Adsorption isotherms indicated that sorption took place at specific homogeneous sites within the adsorbent. Furthermore, BCa²⁺ showed higher sorption capacity compared with other common materials used as adsorbents for Congo red dye. The results showed that BCa²⁺ could be employed as a low-cost material for the removal of Congo red from aqueous solutions.     

Adsorption Isotherms for Bleaching Soybean Oil with Activated Attapulgite

Activated attapulgite was characterized and used as bleaching clay (adsorbent) for soybean oil. Adsorption isotherms for bleaching soybean oil were determined to investigate the applicability of the Langmuir and Freundlich equations and to elucidate the adsorption characteristics of oil on activated attapulgite. The Freundlich model was found to provide a better fit with the experimental data than the Langmuir model. The larger Freundlich constant, K _F at higher temperature indicated more effective adsorption. The heat evolved for oil bleaching increased as the levels of activated attapulgite increased from 0.5 to 3%, due to the increase in adsorptive sites with increasing attapulgite levels as well as multilayer adsorption driven by van der Waals’ forces at smaller amounts of adsorbents. There are enough adsorptive sites with 3% attapulgite to adsorb the pigments associated with soybean oil bleaching. The amount of attapulgite has no effect on ΔH _a when it is >3%, and ΔH _a is about 32 kJ/mol.     

Various carbon-based MgAl2O4 adsorbents and their removal efficiency of CR dye and antibiotics in aqueous media: High selective adsorption capacity,performance prediction and mechanism insight

Various carbon -based MgAl₂O₄ (MAO) adsorbents were synthesized by a simple ultrasound irradiation technology with the activated carbon (AC), carbon quantum dots (CQDs), C₃N₄ (CN) and graphene oxide (GO) as carbon sources. The optimum synthesis conditions for the carbon -based MAO adsorbents were determined by the study of the addition of different types of carbon and different mass ratios of m_{Various carbon}: m_MAO = 2.5%, 5.0%, 7.5% and 10%. The carbon -based MAO adsorbents were used for the adsorption of Congo red (CR) dye, tetracycline hydrochloride (TCH), oxytetracycline hydrochloride (OCH), ciprofloxacin (CIP), naproxen sodium (NPS) and tetrabromobisphenol A (TBBPA) and the seven factors affecting the adsorption behavior were discussed, including the type of carbon, AC content, initial dye concentration (C_CR), adsorbent dosage (C_{carbon -based MAO adsorbents}), adsorption time (A_t), pH value and reaction temperature (T). The corresponding adsorption isotherm models such as Langmuir, Tempkin, Koble-Corrigan, Toth and Freundlich models and thermodynamics of carbon -based MAO adsorbents for the adsorption of CR dye were also studied. When pH = 7.8, C_CR = 200 mg/L, A_t = 90 min, T = 287 K and C_{AC 5.0 wt%-MAO} = 1 g/L, the removal rate of CR dye reaches 89.7%. The back propagation (BP) neural network model was used to predict the adsorption percentage of carbon-based MAO adsorbents, which was consistent with the experimental results. The high adsorption capacity of AC 5.0 wt%-MAO adsorbents for the adsorption of CR dye can be assigned to the synergistic effects of electrostatic interaction, intermolecular force, n-π interaction and hydrogen bonding, while for the adsorption of TCH, OCH and CIP can be ascribed to the electrostatic interaction. This study demonstrated a huge potential of carbon -based MAO adsorbents as an eco-friendly adsorbent for the adsorption of dyes and drugs.     

Influence of Fe3O4 nanoparticles decoration on dye adsorption and magnetic separation properties of Fe3O4/rGO nanocomposites

Magnetite (Fe₃O₄) nanoparticles were prepared by solvothermal method and its composites with reduced graphene oxide namely FG1, FG2, and FG3 (changing magnetite precursor loading 0.1, 0.5, and 1 respectively) were used as adsorbents for the removal of methyl violet (MV) dye. The structural and morphological results confirm that rGO sheets were decorated with Fe₃O₄ and it ensures the variation of active sites toward dye removal property. The maximum adsorption capacity obtained for FG2 was 196 mg/g. The adsorption isotherms and kinetics better fit Langmuir and pseudo-second-order kinetic model for FG1 and FG2. Increasing of Fe₃O₄ loading on rGO reduces the dye adsorption sites and too low Fe₃O₄ loading affects the magnetic separation. The optimal loading of Fe₃O₄ on rGO is important parameter for the adsorption process and fast separation of adsorbent.     

Adsorption of Methyl Chloride on Molecular Sieves,Silica Gels,and Activated Carbon

Adsorption of methyl chloride (CH₃Cl or MeCl) on five different types of adsorbents was investigated experimentally at increasing pressures and room temperature. Prior to adsorption, all adsorbents were analyzed to assess their physical and chemical characteristics. The experimental data was then used to determine the adsorption isotherms, heats of adsorption, adsorption rates, and their respective theoretical models. The MeCl adsorption capacity was found to reasonably correlate with the adsorbent's surface area. The MeCl adsorption isotherm and adsorption rates were fitted for the first time to a Freundlich isotherm model and pseudo first-/second-order kinetic models, respectively. The range of heat of adsorption indicated a physisorption type of bonding; hence, the investigated adsorbents can potentially be regenerated for cyclic adsorption.     

Adsorption studies of methylene blue onto ZnCl2-activated carbon produced from buriti shells (Mauritia flexuosa L.)

The present study reports the preparation of an activated carbon produced from buriti shells (AC_b) using ZnCl₂ as activating agent and its ability to remove methylene blue dye (MB) from aqueous solutions. The obtained AC_b was characterized by N₂ adsorption–desorption isotherms, SEM and FT-IR. The results show that AC_b presents microporous features with BET surface area (S_BET) of 843 m² g⁻¹ and functional groups common in carbonaceous materials. Adsorption studies were carried out and experimental data were fitted to three isotherm models (Langmuir, Freundlich, and Redlich–Peterson) and four kinetic models (pseudo-first order, pseudo-second order, Elovich, and intraparticle diffusion). The isotherm model which best fitted to experimental data was Redlich–Peterson. However, the g parameter of this model indicated that the adsorption of MB onto AC_b occurs according to the mechanism proposed by Langmuir, which showed maximum monolayer adsorption capacity of 274.62 mg g⁻¹. Kinetic studies demonstrated that the Elovich model is suitable to describe the experimental data. Moreover, it was found that the intraparticle diffusion is the limiting step of adsorption process.     

ADSORPTION KINETICS AND EQUILIBRIA OF BASIC DYES ONTO ZEOLITE IN SINGLE AND BINARY COMPONENT SYSTEMS

Adsorptive removal of Basic Blue 3 (BB 3) and Basic Red 18 (BR 18) by a clinoptilolite-type natural zeolite from their single-component solutions has been studied in the temperature range of 298–328 K. Experimental equilibrium results are well described by the Freundlich and the Langmuir isotherm models. The model parameters obtained for single-solute systems at 298 K have been used for the prediction of adsorption isotherms in binary dye solutions using multicomponent isotherm models. Competitive adsorption results between BB 3 and BR 18 in binary solutions satisfactorily fit the extended Freundlich, extended Langmuir, and modified Langmuir models. A site distribution function that gives information about affinity of adsorption sites for competing species in binary systems has been mathematically calculated using the Freundlich parameters. Time-dependent results for single and binary dye solutions have been analyzed according to a pseudo-second-order kinetic model based on chemisorption and a McKay model assuming two resistance diffusion processes, respectively. The diffuse reflectance FT-IR spectra indicate that the dyes are adsorbed via electrostatic interactions in external rings of clinoptilolite by replacing the zeolitic water in a single system, and they diffuse through the liquid associated with zeolitic water in TO₄ tetrahedra (T: Al, Si) in a mixed solution.     

Removal of Acid Dyes from Aqueous Solutions using Chemically Activated Carbon

Abstract

Textile dyes (Acid Yellow 17 and Acid Orange 7) were removed from its aqueous solution in batch and continuous packed bed adsorption systems by using thermally activated Euphorbia macroclada carbon with respect to contact time, initial dye concentration, and temperature. The activated carbon was prepared using a cheap plant-based material called Euphorbia macroclada, which was chemically modified with K₂CO₃. Lagergren-first-order and second-order kinetic models were used to fit the experimental data. Equilibrium isotherms were analyzed by Langmuir and Freundlich isotherms. Equilibrium data fitted well the Langmuir model in the studied temperature (25–55°C) ranges. The maximum adsorption capacity of AY17 and AO7 onto activated carbon was found to be 161.29 and 455 mgg^?1, respectively by Langmuir isotherm at 55°C. Breakthrough curves for column adsorption have also been studied. The desorption of dyes has been experimentally investigated using NaOH solution of pH 11.     

Activated carbon/CoFe2O4 composites: Facile synthesis,magnetic performance and their potential application for the removal of malachite green from water

Activated carbon/CoFe₂O₄ composite (AC/CFO) was synthesized by a simple one-step refluxing route and was used as adsorbent for the removal of malachite green (MG) dye from water. The structure, morphology and magnetic properties of as-prepared composite were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The results indicated that CoFe₂O₄ particles deposited on the surface of activated carbon in the composite were uniform with the particle size in the range of 14–20 nm. The composite adsorbents exhibited a clearly hysteretic behavior under applied magnetic field, which allowed their magnetic separation from water. Batch experiments were carried out to investigate adsorption isotherms and kinetics of MG onto the composite. The experimental data fitted well with the Langmuir model with a monolayer adsorption capacity of 89.29 mg g^?1. The adsorption kinetics was found to follow pseudo-second-order kinetic model. It was indicated that the as-prepared composite could be used as a promising and effective adsorbent for the removal of MG from water.     

Adsorption equilibrium of copper ion and phenol by powdered activated carbon, alginate bead and alginate-activated carbon bead

The adsorption equilibrium characteristics for single and binary components of copper ion and phenol onto powdered activated carbon, alginate bead and alginate-activated carbon (AAC) bead were studied. Adsorption equilibrium data of phenol and copper ion onto the adsorbents could be represented by Langmuir equation. The adsorption capacity of Cu²⁺ onto different adsorbents was in the following order: alginate bead > AAC bead > powdered activated carbon (PAC). On the other hand, that of phenol was: PAC > AAC bead > alginate bead. Multi-component equilibrium data were correlated by three different models. Among them the ideal adsorbed solution theory (IAST) gave the best fit to our data. And the adsorption amount of Cu²⁺ onto AAC bead was greater than that of phenol in the binary components.     

Equilibrium and Kinetic Studies on Lithium Adsorption from Geothermal Water by λ-MnO2

The adsorption equilibria of lithium from geothermal water were investigated by using both powdery and granulated forms of λ-MnO₂ derived from spinel-type lithium manganese dioxide. Optimum amounts of adsorbents were 1.0 g adsorbent/L-geothermal water for powdery λ-MnO₂ and 6.0 g adsorbent/L-geothermal water for granulated λ-MnO₂. The adsorbents exhibited the promising adsorption capacities and their adsorption equilibria of lithium agreed well with the Langmuir adsorption isotherm model. The kinetic data of lithium adsorption have been evaluated using pseudo-first-order, pseudo-second-order kinetics models, as well as Elovich kinetic model. In addition, intra-particle diffusion model has been used for evaluating the kinetic data to evaluate the adsorption mechanism. The adsorption kinetic process was attributed to the gradual adsorption stage where intra-particle diffusion was found as the rate-controlling step.     

ADSORPTION,KINETICS, AND EQUILIBRIUM STUDIES ON REMOVAL OF 4,4-DDT FROM AQUEOUS SOLUTIONS USING LOW-COST ADSORBENTS

The removal of a chlorinated pesticide (4,4-DDT) from aqueous solutions by a batch adsorption technique using different low-cost adsorbents was investigated. Two adsorbents, wood sawdust (A) and cork wastes (B), were used to determine adsorption efficiency. The influence of the adsorbent particle size and the organic matter of water (humic acids) on the removal process was studied. The obtained results were compared to those obtained with a commercial powdered activated carbon (PAC, F400, Chemviron) (C). Kinetic studies were performed to understand the mechanistic steps of the adsorption process. The rate of the adsorption kinetics of 4,4-DDT on the low-cost adsorbents was found best fitted with a pseudo-second-order kinetic model. This is in contrast to the rate of the adsorption kinetics of the PAC F400, which was best fitted with the Lagergren model. The application of the Morris-Weber equation showed that the adsorption process of 4,4-DDT on these adsorbents was complex. Both the adsorption on the surface and the intraparticle diffusion were the rate-controlling mechanisms. Langmuir and Freundlich adsorption isotherms were applicable to the adsorption process and their constants were evaluated. The adsorption capacity (q_m) calculated from the Langmuir isotherm (69.44 mg·g^?1, 19.08 mg·g^?1, and 163.90 mg·g^?1, respectively, for A, B, and C) showed that the process is highly particle size dependent, that the organic matter influenced the adsorption process negatively, and that wood sawdust is the most effective adsorbent for the removal of 4,4-DDT from aqueous solutions. The adsorbents studied exhibited a possible application in water decontamination, as well as in treatment of industrial and agricultural waste waters.     

Synthesis of hydrogels from fractionated proteins of Moringa oleifera Lam. seeds for the treatment of water contaminated with black reactive dye 5

As has been portrayed in the literature, the main proteins extracted from the seeds of Moringa oleifera Lam. have coagulant and clarifying potential in water treatment. However, when using them as coagulant agents, sludge formation occurs, which is an environmental problem. Thus, it was proposed to synthesize hydrogels from the main Moringa seeds proteins and use them as adsorbents. This work aimed to synthesize albumin hydrogels and globulin hydrogels and evaluate their efficiency as adsorbents to remove the reactive black 5 dye. Through FTIR spectrum it was possible to confirm that the synthesis of hydrogels occurred successfully. The kinetic data fit the pseudo-second order model for both hydrogels. The equilibrium isotherms showed that adsorption occurs in multilayers, due to Freundlich fitting. The maximum adsorption capacity occurred at 298 K and was 1.19 mg g⁻¹ for the albumin hydrogel and 10.06 mg g⁻¹ for the globulin hydrogel. Through the results it is possible to state that globulin hydrogel was more favourable for adsorption since it has a more porous morphology and requires less mass compared to albumin hydrogel.     

Kinetics,Thermodynamics, and Isothermic Evaluation in Sorption Study of Hazardous Dye Using Sodium Dodecylsulfate Physically Impregnated in Polyester‐Type Polyurethane Foam

Use of polyester‐type polyurethane foam (PUF) is an effective adsorbent for the removal of hazardous dye: crystal violet (CV) from an aqueous solution. In this adsorption study, the formation of hydrophobic ion pair (opposite charge attraction) between the charged species, i.e., cationic (basic) dye CV and anionic surfactant sodium dodecylsulfate (SDS) sorbed onto PUF. Chemical calculations were performed using quantum simulation to understand ion‐pair formation for CV–SDS at the semiempirical PM6 level. Adsorption studies were performed using 200 mg cylindrical PUF with an overhead stirrer in solutions containing varying compositions of the dye–surfactant mixture. The equilibrium thermodynamics and kinetics of the adsorption process were studies by measuring CV dye removal as a function of time and temperature. Results show that the formation of the dye–surfactant ion pair is necessary for effective adsorption onto PUF. Various adsorption isotherms, viz., Langmuir, Freundlich, Temkin, Dubinin–Radushkevich (DRK), Harkin‐Jura, and several kinetic models, viz., pseudo‐first order, pseudo‐second order, Elovich, and Intraparticle diffusion were used to fit the spectrophotometric result. The equilibrium adsorption data fit to the Langmuir isotherm gives the maximum adsorption of PUF as 33.39 mg g^?1 from 200 mL 5.0 × 10^?5 mol L^?1 CV solution at 298.15 K. The kinetics study showed that the overall adsorption process follows pseudo‐second‐order kinetics. The Morris–Weber model suggests that an intraparticle diffusion process is active in controlling the adsorption rate. The Freundlich, Temkin, DRK adsorption isotherms showed that solute dye transfers from solution to the PUF adsorbent surface through physical adsorption. The Langmuir and Harkin‐Jura adsorption isotherms suggest that the adsorbent surface is homogeneous in nature. The thermodynamic data showed that the adsorption process is spontaneous and endothermic with a positive enthalpy change and a negative change in Gibb's energy.     

Modelling of adsorption of textile dyes over multi-walled carbon nanotubes: Equilibrium and kinetic

The paper deals with the application of multiwall carbon nanotubes (CNTs) to the adsorption of dyes from wastewater. Textile dyes are dangerous and diffused pollutant in wastewater, and the paper results confirmed the good adsorption ability of CNTs, with respect to classic active carbon, even for different dye types. The effect of surface treatments of CNTs was primarily investigated, revealing that neither the presence of residual catalyst nor common surface treatment (oxidation) affects the CNT's performances. Therefore less expensive nonpurified CNTs were assessed as good and economically convenient alternative for the process. In order to gain in generality in adsorption kinetic modelling, the parameters of the "best fitting" pseudo-second order model have been correlated to the main process variables (the dye initial concentration and the specific mass of CNTs.) setting-up a predictive kinetic model useful design new application of these materials in currently operating industrial operations for adsorption. In addition, isothermal data were used to screen all the relevant adsorption isotherms models and the Temkin model was confirmed as the more effective to accurately fit equilibrium data for any of the considered different dye types.     

Removal of Congo Red dye from aqueous solution using Amberlite IRA-400 in batch and fixed bed reactors

Removal of Congo Red (CR) azo dye by adsorption process using Amberlite IRA-400 resin was evaluated in both batch and fixed bed system. From the batch adsorption results, maximum loading efficiency (99.99%) of CR dye was obtained at the conditions pH 4.5, temp. 303?K, contact time 180?min., Amberlite IRA-400 dose 0.5?g. The isotherm study ascertained on favorability of adsorption process as the value of separation factor (K_L?=?0.88) and Freundlich constant (1/n?=?0.96?R²?=?0.99) than Freundlich model (R²?=?0.97). The kinetic data studied at three different CR dye concentration (50, 75, 100?mg) and results were fitted with both pseudo-first-order and second-order model equations. The values of R² obtained are of 0.95 and 0.99 for former and later one, respectively, ensuring on best fitting of pseudo-second-order kinetics and also suggesting about the chemisorptions type of adsorption. The bed depth service model was applied for competitive analysis of the CR dye adsorption in column variables indicating mass transfer from aqueous solution to Amberlite IRA-400 phase. Fourier transform infrared analysis of CR-loaded resin Amberlite IRA-400 showed a band shifted from 1057 to 1130?cm^?1 confirming CR adsorption with Amberlite IRA-400. Scanning electron microscope analysis of resin before and after adsorption was well evident from the phase patterns. Selective separation of CR dye from waste effluent of a textile industry bearing CR dye along with other trace heavy metal was achieved.     

Adsorption of C.I. Basic Blue 9 on cyclodextrin-based material containing carboxylic groups

Cyclodextrin-based materials containing carboxylic groups (CD/CMC adsorbents) are used for the removal of C.I. Basic Blue 9 (BB 9) from aqueous solutions. Studies concerning the sorption kinetics (i.e. the effects of contact time, dye concentration and mass of sorbent) are presented and discussed. Results of adsorption experiments showed that these adsorbents exhibited high sorption capacities toward C.I. Basic Blue 9. The adsorption capacity of BB 9 on CD/CMC material increased as the dosage of the material increased and the adsorption kinetics followed a pseudo-second order model. However, the sorption was dependent on the presence of carboxylic groups. Four isotherm equations have been tested in the present study, namely Freundlich, Langmuir, Temkin and generalized. The characteristic parameters for each isotherm have been determined. The monolayer adsorption capacity was 56.5 mg g⁻¹. The Freundlich equation represented the best fit of experimental data than the other isotherm equations.     

Modeling of Adsorptive Filtration of a Leather Dye in a Fixed Bed Column

Abstract

Activated carbons offer an efficient option for the removal of organic and inorganic contaminants from water. However, due to its high costs and difficulty in the regeneration, other low cost adsorbents have been used. In this work, the adsorption capacity of an adsorbent carbon with high iron oxides concentration was compared with that of a commercial activated carbon in the removal of a leather dye from an aqueous solution. The adsorbents were characterized using SEM/EDAX analysis and BET surface area. The capacity of adsorption of the adsorbents was evaluated through the static method at 25°C. The results showed that the color removal was due to the adsorption and precipitation of the dye on the surface of the solids. The adsorption equilibrium was described according to the linear model for the adsorbent carbon and the equilibrium constant was 0.02 L g^?1. The equilibrium of adsorption on activated carbon exhibited a behavior typical of the Langmuir isotherm and the monolayer coverage was 24.33 mg g^?1. A mathematical model was proposed to describe the dynamics of the color removal using a fixed bed considering that the color removal is due to the adsorption and the precipitation of the dye on the adsorbent.