Investigation of equilibrium and kinetic parameters of methylene blue adsorption onto MCM-41

Mesoporous MCM-41 was synthesized at room temperature using tetraethoxysilane (TEOS) with cetyltrimethylammonium bromide (CTAB) and employed as an effective adsorbent for the adsorption of methylene blue dye from aqueous solution. The as-synthesized MCM-41 was calcined at 250 and 550°C to study the relation between the surface area and pore volume with surfactant removal. The synthesized MCM-41 was characterized using thermo gravimetric analysis (TGA), X-ray diffraction (XRD) patterns, nitrogen adsorption/desorption isotherms and Fourier transform infrared (FT-IR) spectroscopy. The MCM-41 calcined at 550°C showed higher surface area (1,059 m² g^?1) with pore volume of 0.89 ml g^?1 and was used for the investigation of adsorption isotherms and kinetics. The experimental results indicated that the Freundlich and Redlich-Peterson models expressed the adsorption isotherm better than the Langmuir model. In addition, the influence of temperature and pH on adsorption was also investigated. The decrease in temperature or the increase in pH enhanced the adsorption of dye onto MCM-41. A maximum adsorption capacity of 1.5×10^?4 mol g^?1 was obtained at 30°C. The kinetic studies showed that the adsorption of dye on MCM-41 follows the pseudo-second-order kinetics.     

Sorption of copper by a highly mineralized peat in batch and packed‐bed systems

BACKGROUND: The performance of peat for copper sorption was investigated in batch and fixed‐bed experiments. The effect of pH was evaluated in batch experiments and the experimental data were fitted to an equilibrium model including pH dependence. Hydrodynamic axial dispersion was estimated by tracing experiments using LiCl as a tracer. Six fixed‐bed experiments were carried out at copper concentrations between 1 and 60 mg dm^?3 and the adsorption isotherm in dynamic mode was obtained. A mass transport model including convection–dispersion and sorption processes was applied for breakthrough curve modelling. RESULTS: Maximum uptake capacities in batch mode were 22.0, 36.4, and 43.7 mg g^?1 for pH values of 4.0, 5.0, and 6.0, respectively. Uptake capacities in continuous flow systems varied from 36.5 to 43.4 mg g^?1 for copper concentrations between 1 and 60 mg dm^?3. Dynamic and batch isotherms showed different shapes but a similar maximum uptake capacity. Sorbent regeneration was successfully performed with HCl. A potential relationship between dispersion coefficient and velocity was obtained with dispersion coefficients between 5.00 × 10^?8 and 2.95 × 10^?6 m² s^?1 for water velocities ranging between 0.56 × 10^?4 and 5.03 × 10^?4 m s^?1. The mass transport model predicted both the breakpoints and the shape of the breakthrough curves. CONCLUSIONS: High retention capacities indicate that peat can be used as an effective sorbent for the treatment of wastewater containing copper ions. Copyright © 2009 Society of Chemical Industry     

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.     

Two-resistance mass transfer model for the adsorption of various dyestuffs onto chitin

The kinetics of the adsorption of various dyestuffs onto chitin have been studied. The dyestuffs used are Neoland Blue 2G, Eriochrome Flavine A, and Solophenyl Brown 3RL and a number of process variables were considered, such as adsorbent mass and dye concentration. The mass transfer model is based on the assumption of a pseudoirreversible isotherm and two resistances to mass transfer. These are external mass transfer and internal pore diffusion mass transfer. The rate of adsorption of dyestuffs onto chitin can thus be described by an external mass transfer coefficient and a pore diffusion coefficient. The external mass transfer coefficients are 5.0 × 10^?5, 5.0 × 10^?5, and 1.0 × 10^?5 m·s^?1 and the pore diffusivities are 3.0 × 10^?10 and 4.0 × 10^?11 m²·s^?1 for Neolan Blue 2G, Eriochrome Flavine A, and Solophenyl Brown 3RL, respectively.     

Removal of Rhodamine B Dye Using Activated Carbon Prepared from Palm Kernel Shell and Coated with Iron Oxide Nanoparticles

The efficacy of activated carbon prepared from Palm Kernel Shell (PKSAC) from agriculture biomass and coated with magnetic nanoparticle (Fe₃O₄) in the removal of Rhodamine B dye was investigated. Adsorption experiments were carried out at various initial pH, adsorbent dosage, initial dye concentration, particle size, and temperature. Kinetic analyses were conducted using pseudo first order, pseudo second order and intra particle diffusion models. However, the regression results showed that the adsorption kinetics was represented more accurately by the pseudo second order model. The pseudo second order kinetic constant obtained was 1.7 × 10^?4 min^?1 at 323 K when 200 mg L^?1 dye concentration was used. The equilibrium data were well described by both Langmuir and Freundlich isotherm models. The Langmuir adsorption capacity was 625 mgg^?1. The rate of adsorption improved with increasing temperature and the process was endothermic with ΔH value assessed at 80 kJmol^?1. Results obtained reveal that activated carbon prepared from Palm Kernel Shell coated with magnetic nanoparticle from agriculture biomass can be an attractive option for dye removal from industrial effluent.     

Removal of Crystal Violet Dye from Aqueous Solution Using Calcined and Uncalcined Mixed Clay Adsorbents

In this work, calcined and uncalcined mixed clays containing kaolin, ball clay, feldspar, pyrophyllite, and quartz are examined as a potential adsorbent for the removal of crystal violet dye from aqueous solution. These clays are characterized by nitrogen adsorption/desorption isotherms, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and thermo gravimetric analysis (TGA). The kinetics and thermodynamic parameters as well as the effects of the pH, the temperature, and the adsorbent dosage have also been investigated. The experimental results indicate that the Langmuir model expresses the adsorption isotherm better than the Freundlich model. The obtained result showed a tremendous increase in the crystal violet adsorption capacity (1.9 × 10^?3 mol g^?1) after calcination, which is one order greater than that of the uncalcined mixed clay. The mechanism of the adsorption process is elucidated on the basis of experimental data. The percentage removal of crystal violet dye increases with increasing the pH, the temperature, and the adsorbent dosage. The investigation of kinetic studies indicates that the adsorption of crystal violet on calcined and uncalcined mixed clays could be described by the pseudo-second-order model. The negative Δ G ⁰ values obtained from the thermodynamic investigation confirm that the adsorption is spontaneous in nature. The adsorption results suggest that the calcined and uncalcined mixed clays can also be used as low cost alternatives to the expensive activated carbon for the removal of dyes from aqueous solution.     

Kinetics and diffusion processes in colour removal from effluent using wood as an adsorbent

The rates of adsorption of a basic dye, Astrazone Blue, and an acidic dye, Telon Blue, on wood have been studied. The rate controlling step is mainly intraparticle diffusion, although a small resistance due to a boundary layer is experienced. The activation energies for the adsorption of Astrazone Blue and Telon Blue on wood are 16.8 kJ mol^?1 and 9.6 kJ mol^?1, respectively. The diffusion coefficients vary from 6×10^?13 cm² s^?1 to 18×10^?13 cm² s^?1 for Astrazone Blue at 18°C and from 3 × 10^?13 cm² s^?1 to 8 × 10^?13 cm² s^?1 for Telon Blue at 18°C. The variation in diffusivities is attributed to boundary layer effects.     

Preparation and Characterization of Activated Carbon from Eucalyptus Sawdust I. Activated by NaOH

Eucalyptus sawdust was used as a precursor to prepare activated carbon using NaOH as a chemical activation agent. The effect of preparation conditions on the characteristics of the produced activated carbon used as an adsorbent was investigated. The performance of the activated carbon was characterized by N₂ adsorption–desorption isotherms, Brunauer–Emmett–Teller equation, Barett–Joyner–Halenda equation, scanning electron microscopy and Fourier transform infrared analysis. When the eucalyptus sawdust mass was 30.00 g, with particle sizes between 0.25 and 0.42 mm, and the sawdust was heated and charred before activation by NaOH, the optimized conditions for the preparation of activated carbon was found to be as follows: mass ratio of NaOH to eucalyptus sawdust, 1:2; activation time, 30 min; and activation temperature, 700 °C. The Iodine number and BET surface area of the produced activated carbon was 899 and 1.12 × 10³ m² g^?1, respectively, with a 13.3 % yield. Activated carbon exhibits adsorption isotherms of type IV. The total pore volume, micropore volume and average pore diameter were recorded as 0.636, 0.160 cm³ g^?1 and 2.27 nm, respectively. The pore structure of the activated carbon is mainly mesoporous. Carbonyl and hydroxyl groups may also exist on the activated carbon surface.     

Sorption Potential of Styrene‐Divinylbenzene Copolymer Beads for the Decontamination of Lead from Aqueous Media

Abstract

The decontamination of lead ions from aqueous media has been investigated using styrene‐divinylbenzene copolymer beads (St‐DVB) as an adsorbent. Various physico‐chemical parameters such as selection of appropriate electrolyte, contact time, amount of adsorbent, concentration of adsorbate, effect of foreign ions, and temperature were optimized to simulate the best conditions which can be used to decontaminate lead from aqueous media using St‐DVB beads as an adsorbent. The atomic absorption spectrometric technique was used to determine the distribution of lead. Maximum adsorption was observed at 0.001 mol L^?1 acid solutions (HNO₃, HCl, H₂SO₄ and HClO₄) using 0.2 g of adsorbent for 4.83×10^?5 mol L^?1 lead concentration in two minutes equilibration time. The adsorption data followed the Freundlich, Langmuir, and Dubinin‐Radushkevich (D‐R) isotherms over the lead concentration range of 1.207×10^?3 to 2.413×10^?2 mol L^?1. The characteristic Freundlich constants i.e. 1/n=0.164±0.012 and A=2.345×10^?3±4.480×10^?5 mol g^?1 have been computed for the sorption system. Langmuir isotherm gave a saturated capacity of 0.971±0.011 mmol g^?1, which suggests monolayer coverage of the surface. The sorption mean free energy from D‐R isotherm was found to be 18.26±0.75 kJ mol^?1 indicating chemisorption involving chemical bonding for the adsorption process. The uptake of lead increases with the rise in temperature. Thermodynamic parameters i.e. ΔG, ΔH, and ΔS have also been calculated for the system. The sorption process was found to be exothermic. The developed procedure was successfully applied for the removal of lead ions from real battery wastewater samples.     

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.     

Removal of victoria blue from aqueous solution by fly ash

The use of fly ash for the removal of victoria blue (C126, 44045) from aqueous solution at different concentrations and pH has been investigated. The process follows first order adsorption rate expression and the rate constant was found to be 1.70 × 10^?2 min^?1 at a victoria blue concentration of 1.0 × 10^?4 M and 25°C. The uptake of victoria blue by fly ash is diffusion controlled and the value of mass transfer coefficient is 1.25 × 10^?5 cm sec^?1. The equilibrium data fit well in the Langmuir model of adsorption. Maximum removal was noted at pH 8.0. Low desorption of dye from adsorbent surface indicates that the process may not be essentially a reversible one.     

p-Sulphonatocalix[8]arene functionalized silica resin for the enhanced removal of methylene blue from wastewater: equilibrium and kinetic study

ABSTRACT

The present investigation represents the synthesis of new p-sulphonatocalix[8]arene-based silica resin, p-SC8SR (5) and its application for the enhanced removal of methylene blue (MB) dye from contaminated water. The new p-SC8SR (5) resin was characterized by FT-IR, SEM, and EDX spectroscopy. The adsorption of MB on p-SC8SR (5) was investigated systematically by evaluating the effects of adsorbent dosage, initial pH, contact time, dye concentration, and ionic strength. Excellent adsorption (94%) of MB on p-SC8SR (5) was achieved at pH 9.5, contact time 10 min by using 0.2 mol L^?1 ionic strength and 2 × 10^?5 M initial MB dye concentration. Kinetic behavior of MB dye adsorption process on the newly synthesized p-SC8SR (5) adsorbent follows the pseudo-second-order rate model (R² = 0.998 and 0.999 for 2 × 10^?5 M and 1 × 10^?4 M, respectively). Adsorption isotherms were fitted well by the Freundlich model with excellent value of coefficient of determination (R²) = 0.995 which demonstrated that the adsorption of MB follows multilayer mechanism. Wastewater samples contaminated with MB were used to assess efficiency of the p-SC8SR (5) adsorbent. Results indicated that newly synthesized p-SC8SR (5) was found to be efficient adsorbent. During the removal process, the role of different functional groups’ cyclic structure was scrutinized and found that the ionic property as well as π–π interaction of host molecules played imperative role in the extent of adsorption.     

Adsorption of dyestuffs onto chitin. External mass transfer processes

The effect of several variables on the adsorption rate of four dyestuffs onto chitin was studied. A model is proposed enabling the film mass transfer coefficients to be determined. The coefficients were independent of initial dye concentration, chitin mass, chitin particle size, and temperature; a slight dependence with agitation was obtained. The film mass transfer coefficients at 400 rpm were 2.8×10^?3, 2.9×10^?3, 3.9×10^?3, and 0.9×10^?3 cm/s for Acid Blue 25, Acid Blue 158, Mordant Yellow 5, and Direct Red 85, respectively.     

Adsorption of different dyes from aqueous solution using Si-MCM-41 having very high surface area

Adsorption characteristics of four different dyes Safranin O (cationic), Neutral Red (neutral), Congo Red (anionic) and Reactive Red 2 (anionic) on Si-MCM-41 material having very high surface area are reported. The surface morphology of Si-MCM-41 material before and after adsorbing dye molecules are characterised by FTIR, HRXRD, nitrogen adsorption–desorption isotherms, FESEM, and HRTEM. The adsorption capacities of Si-MCM-41 for the dyes followed a decreasing order of NR > SF > CR > RR2. The adsorption kinetics, isotherm and thermodynamic parameters are investigated in detail for these dyes using calcined Si-MCM-41. The kinetics and isotherm data showed that both SF and NR adsorb more rapidly than CR and RR2, in accordance with pseudo-second-order kinetics model as well as intraparticle diffusion kinetics model and Langmuir adsorption isotherm model respectively. The thermodynamic data suggest that the dye uptake process is spontaneous. The high adsorption capacities of dyes on Si-MCM-41 (q_m = 275.5 mg g^?1 for SF, q_m = 288.2 mg g^?1 for NR) is explained on the basis of electrostatic interactions as well as H-bonding interactions between adsorbent and adsorbate molecules. Good regeneration capacity is another important aspect of the material that makes it potent for the uptake of dyes from aqueous solution.     

Synthesis and characterization of fluorescent PEG-polyurethane with free carboxyl groups

An innovative spherical poly(vinyl alcohol)(PVA)/peat/clay porous composite bead was prepared and shown to be suitable for use as an adsorbent. The mass transport process for the adsorption of metal ions onto this composite bead in an aqueous system was investigated. In the external mass transport process, the diffusion coefficient (D₁) of Cu⁺² and Zn⁺² ions increased with increasing initial metal ion concentration and the increasing effect was more pronounced in the initial metal ion concentrations range of 18?×?10^-3 to 22?×?10^-3?M. The diffusion rate of Zn⁺² ions was faster than that of Cu⁺² ions. In the intraparticle diffusion process, the diffusion coefficient (D₂) decreased with increasing initial metal ion concentration in the initial concentration range of 1?×?10^-3 to 4?×?10^-3?M, and the value of D₂ maintained an almost constant value in the initial concentration range of 8?×?10^-3 to 22?×?10^-3?M. The rate of ion diffusion within the adsorbent for Cu⁺² ions was faster than that for Zn⁺² ions. The adsorption mechanism was controlled by the intraparticle diffusion process. The adsorption followed the Langmuir adsorption isotherm model. The maximum amount of adsorbed metal ions for Cu⁺² and Zn⁺² ions were 22.57 and 13.62?mg/g composite bead, respectively.     

Allene adsorption isotherms and active site determination on various titanium trichloride catalysts

The techniques of gas-solid chromatography and temperature programmed desorption have been applied to the problem of evaluating the number of active polymerizing centres in variously prepared titanium trichloride catalysts. Using gas-solid chromatography the adsorption isotherms of allene on (i) hydrogen reduced TiCl₄ (Stauffer H), (ii) aluminium reduced TiCl₄ (Stauffer AA), (iii) Et₂AlCl activated Stauffer AA and (iv) Et₃Al activated Stauffer AA, have been obtained. The non-linear isotherms so derived have been analysed in terms of a two site Langmuir model from which the heats of adsorption and the number of adsorption sites have been evaluated. The number of surface sites is virtually identical on all four materials having values of 4.2 × 10¹³, 5.3 × 10¹³, 4.8 × 10¹³ and 4.9 × 10¹³ sites cm^?2 respectively ($\text{～200}\text{A}\text{?}{}^2$ per site), the majority of these sites (> 90%) having heats of adsorption of 8 kcal mol^?1. Since these catalysts have different surface areas which varied from 2.5 m²g^?1 to 8.7 m²g^?1 the near identity of the site densities suggests that a fundamental property of the solid is being measured. The only observed effect of the aluminium alkyl activator on Stauffer AA was to reduce the heat of adsorption of the high energy site from 16.5 kcal mol^?1 to 12.7 kcal mol^?1 (Et₂AlCl) and to 9.3 kcal mol^?1 (Et₃Al). Temperature programmed desorption experiments on Stauffer AA and Stauffer H confirmed the heat of adsorption and the site densities of the high energy sites showing coverages of 2.9 × 10¹² and 2.6 × 10¹² sites cm^?2 respectively for these sites (identical to those predicted by the two site Langmuir adsorption model) and desorption activation energies of 18.8 and 17.8 kcal mol^?1 respectively, inferring no activation energy to adsorption on to these sites.     

Adsorption of Textile Dye on Zinc Stannate Oxide: Equilibrium,Kinetic and Thermodynamics Studies

Zn₂SnO₄ powder was prepared by hydrothermal process at 200°C for 12 h. The material was characterized by X-ray-diffraction and surface area. The synthesized sample presented a pure phase and a surface area of 48.8 m² · g^?1. It was used as adsorbent to remove the Reactive Red 141 that is a azo textile dye. The adsorption kinetics of the textile dye on Zn₂SnO₄ followed the pseudo-second-order model. The adsorption process was found to be controlled by both external mass transfer and intraparticle diffusion. The equilibrium data were in good agreement with both Langmuir and Freundlich isotherms. Thermodynamic parameters were calculated, and the results revealed that the adsorption process is endothermic in nature, with weak forces of the Van der Walls acting.     

Drying Kinetics of a Porous Spherical Particle and the Inversion Temperature

A model is presented for drying of a single porous particle with superheated steam and humid air. Experimental data for spherical porous ceramic particle reported in the literature were used for the validation of the model. An inversion temperature at which the evaporation rates within superheated steam and humid air are equal was predicted. The effect of thermophysical properties of the particle (permeability 10^?14 ? 10^?17 m², diameter 3 × 10^?3 ? 10 × 10^?3 m) and operating variables (gas mass flux 0.26 ? 0.78 kg m^?2 s^?1, drying agent temperature 120–200°C) is tested. The inversion temperature is shown to be affected by the thermophysical properties of the porous particle and of the drying agent.     

Review od ADVANCES IN DRYING,Vol. 3,

RF hydrogels were synthesized by the sol-gel polycondensation of resorcinol with formaldehyde and RF cryogels were prepared by freeze drying of the hydrogels with t-butanol. The cryogels were characterized by nitrogen adsorption, density measurements, and scanning electron microscope. Their porous properties were compared with those of the aerogels prepared by supercritical drying with carbon dioxide. RF cryogels were mesoporous materials with large mesopore volumes >5.8× 10^?4m³/kg. Although surface areas and mesopore volumes of the cryogels were smaller than those of the aerogels, the cryogels were useful precursors of mesoporous carbons. Aerogel-like carbons (carbon cryogels) were obtained by pyrolyzing RF cryogels in an inert atmosphere. The carbon cryogels were mesoporous materials with high surface areas >8.0× 10⁵m²/kg and large mesopore volumes >5.5× 10^?4m³/kg. When pyrolyzed, micropores were formed inside the cryogels more easily than inside the aerogels.     

Effect of high pressure on mass transfer kinetics of granny smith apple

The mass transfer kinetics during osmotic dehydration of granny smith apple slices in 60 Brix fructose and sucrose solution was studied at atmospheric pressure and at elevated pressure of 200–600?MPa at 40°C. The moisture and solute fractions in apple slices during osmotic dehydration under high pressure were predicted by Weibull frequency distribution model. The calculated effective moisture diffusivity values of apple slices suspended in fructose and sucrose solution during high-pressure treatment (0.1–600?MPa) were in the range of 6.35?×?10^?10 to 3.60?×?10^?9?m²/s and 7.96?×?10^?10 to 4.32?×?10^?9?m²/s, respectively.