Removal of Some Organic Dyes by Hexane-Extracted Spent Bleaching Earth

The removal of some organic dyes from aqueous solution by hexane-extracted spent bleaching earth, a waste material from the palm oil industry, was investigated. It was noted that the material had better affinity for basic than acid dyes. Various parameters affecting the removal process were studied. These were pH, initial dye concentration, sorbent dosage, temperature and agitation rate in the batch process. Experimental data show that both the boundary layer and intraparticle diffusion effect play important roles in the rate of dye removal. Maximum sorption capacities for some basic and acid dyes studied compare favourably with those reported using other low-cost sorbents. © 1997 SCI.     

Biosorption of Zinc on Palm Tree Leaves: Equilibrium,Kinetics, and Thermodynamics Studies

Abstract

The efficiency of using palm tree leaves to remove zinc ions from aqueous solution was studied. Adsorption isotherms, kinetics, and thermodynamics studies were conducted. The influence of different experimental parameters, such as equilibrium pH, shaking rate, temperature, and the presence of other pollutants such as chelating agents on the biosorption of zinc on palm tree leaves was investigated.

Batch biosorption experiments showed that palm tree leaves used in this study proved to be suitable for the removal of zinc from dilute solutions where a maximum uptake capacity of 14.7 mg/g was obtained at 25°C. Zinc biosorption on palm tree leaves was found to be highly pH dependent. The biosorption process was found to be rapid with 90% of the adsorption completed in about 10 min. Dynamics studies of the biosorption of zinc on palm tree leaves showed that the biosorption process followed the pseudo second‐order kinetics with little intraparticle diffusion mechanism contribution. The equilibrium results indicated that zinc biosorption on palm tree leaves could be described by the Langmuir, Freundlich, Gin et al., and Sips models. Using the Langmuir equilibrium constants obtained at different temperatures, the thermodynamics properties of the biosorption (ΔG⁰, ΔH⁰, and ΔS⁰) were also determined. The values of these parameters indicated the spontaneous and endothermic nature of zinc biosorption on palm tree leaves.     

Sorption of Brilliant Red HE-3B Reactive Dye from Aqueous Solution onto Seashells Waste: Equilibrium and Kinetic Studies

The potential of waste seashells powder, as a new adsorbent for Brilliant Red HE-3B reactive dye removal from aqueous solutions, was examined by the batch technique. The Freundlich, Langmuir, and Dubinin-Radushkevich adsorption models were applied to describe the equilibrium sorption data and to determine the corresponding isotherm constants. The values of the thermodynamic parameters, ΔG, ΔH, and ΔS, indicate that the sorption of reactive dye is a spontaneous and endothermic process. The kinetic data evaluated by pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models suggested that the sorption of reactive dye onto seashell is a complex process and both surface sorption and intraparticle diffusion contributes to the rate limiting step.     

Evaluation of Metal Antimonate Compounds for the Removal of Radiostrontium from Radioactive Liquid Waste: Characterization and Sorption Behavior

⁹⁰Sr having moderate half life (t1/2 = 30 yr) is of major concern for radioactive waste management. Metal antimonate compounds have been employed for the removal of ⁹⁰Sr from low level liquid waste stream (LLW). Antimonate compounds of tin, manganese, and zirconium were synthesized and their composite materials were prepared by coating with polymethyl metha acrylate beads (PMMA). The composite materials were evaluated for the removal of radiostrontium. The K_d value of about 1800–2000 was observed for all the three metal antimonate composite materials. Effect of pH, salt concentration, temperature, and strontium ion concentration on K_d value was studied. The sorption behavior was examined with various sorption isotherms like Langmuir, Freundlich, and Dubinin-Radushkevich. The thermodynamic parameters for the three composite materials were evaluated. The sorption was observed to be spontaneous and endothermic in nature. From the practical utilization point of view, the rate of uptake of radiostrontium by the composite material was investigated. Weber Morris diffusion model of the uptake studies suggested an intraparticle diffusion mechanism. The kinetics was found to follow pseudo first order pattern with intraparticle diffusion. However, intraparticle diffusion is not the rate controlling step.     

MODIFIED PLANTAIN PEEL AS CELLULOSE-BASED LOW-COST ADSORBENT FOR THE REMOVAL OF 2,6-DICHLOROPHENOL FROM AQUEOUS SOLUTION: ADSORPTION ISOTHERMS,KINETIC MODELING,AND THERMODYNAMIC STUDIES

In this study, the feasibility of using modified plantain peel to remove 2,6-dichlorophenol from iaqueous solutions was investigated under batch mode. The effects of physical factors such as initial 2,6-dichlorophenol concentration, contact time, biosorbent particle size, biosorbent dosage and temperature on the removal process were evaluated. The results showed that biosorption of 2,6-dichlorophenol was dependent on these factors. The equilibrium biosorption data were analyzed by the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) adsorption isotherm models. The four tested isotherm models provided good fits to the experimental data obtained at 30°C; however, the Freundlich isotherm model provided the best correlation (R² = 0.9874) of the experimental data. The maximum monolayer biosorption capacity (Q _max ) was found to be 14.25 mg/g. The biosorption kinetics data of 2,6-dichlorophenol were analyzed by pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion, and liquid film diffusion models. The five kinetic models fitted well to the biosorption kinetic data; however, the pseudo-second-order kinetic model gave the best fit when the biosorption mechanism was controlled by film diffusion. Thermodynamic quantities such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), standard entropy change of biosorption (ΔS°), and activation energy (E_a) were evaluated, and it was found that the biosorption process was spontaneous, feasible, endothermic in nature and of dual nature, physisorption and chemisorption; however, the physisorption process was dominant. Therefore, modified plantain peel has potential for application as an effective bioadsorbent for removal of 2,6-dichlorophenol from aqueous solution.     

Biosorption of methylene blue from aqueous solution by softstem bulrush (Scirpus tabernaemontani Gmel.)

BACKGROUND: The removal of methylene blue from aqueous solution was studied using softstem bulrush (Scirpus tabernaemontani Gmel.) as the biosorbent. The effects of various parameters including contact time, biosorbent dosage, ionic strength and solution pH on the biosorption were investigated. RESULTS: The sorption capacity increased with an increase in biosorbent dosage and a decrease in ionic strength. The equilibrium time was found to be 240 min for full equilibration. Pseudo‐first‐order, pseudo‐second‐order, Bangham equation and intraparticle diffusion models were applied to fit the kinetic data, and the results showed that the sorption process followed the pseudo‐second‐order model. Equilibrium data conformed to Langmuir and Redlich–Peterson isotherm models, with a maximum monolayer biosorption capacity of 53.8 mg g^?1 for the Langmuir isotherm at 18 °C. The value of ΔG was estimated to be ? 29.24 kJ mol^?1, indicating the spontaneous nature of the biosorption. The biosorption process was strongly pH‐dependent and favourable at alkaline pH. CONCLUSION: Softstem bulrush, which is readily available and inexpensive, could be employed as a promising biosorbent for the removal of dye. Copyright © 2008 Society of Chemical Industry     

The use of Jatobá bark for removal of cationic dyes

In this work, the application of Jatobá bark (the waste product of medicinal plant processing) in removal of the cationic dyes Methylene Blue, Crystal Violet and Rhodamine B from aqueous solution was studied in a batch system. The effect of contact time, pH and temperature on dye removal was investigated. An increase in pH from 2 to 10 was accompanied by an increase in the amount of dye adsorbed. The equilibrium sorption data fitted to the Langmuir, Freundlich and Langmuir–Freundlich equations were investigated. The Langmuir–Freundlich isotherm exhibited the best fit with the experimental data and the maximum adsorption capacities at room temperature being 211.5, 89.5 and 69.4 for Rhodamine B, Methylene Blue and Crystal Violet, respectively. The kinetic sorption was evaluated by the pseudo‐first‐order, pseudo‐second‐order and intraparticle diffusion models. It was observed that sorption follows the pseudo‐second‐order kinetic model. The thermodynamic parameters for the sorption process were also determined. The spontaneous and endothermic nature of adsorption was obtained based on the negative value of free energy (ΔG) and the positive value of enthalpy (ΔH). The results indicate that Jatobá bark could be used as a low‐cost material for the removal of cationic dyes from wastewater.     

Cysteine-Functionalized Chitosan Magnetic Nano-Based Particles for the Recovery of Uranium(VI): Uptake Kinetics and Sorption Isotherms

Magnetic-chitosan nanoparticles, functionalized with cysteine, were synthesized and characterized by element analysis, FT-IR, XRD, TEM, and vibrating sample magnetometry. The sorbent was tested for U(VI) recovery, considering:

• a. pH effect,

• b. sorption isotherms (fitted by Langmuir equation), and

• c. uptake kinetics (modeled using the PSORE).

Maximum sorption capacity approached 100 mg U g^?1. The nanometric size of sorbent reduces the impact of resistance to intraparticle diffusion; this may explain the fast kinetics (equilibrium within 50 min). The reaction is exothermic, spontaneous. The metal could be desorbed using acidified urea solution and the sorbent could be recycled for 5 cycles.     

Sorption of Acid Green 25 on chitosan: Influence of experimental parameters on uptake kinetics and sorption isotherms

Acid Green 25, which is a diazoic dye bearing two sulfonic groups, is efficiently sorbed on chitosan. The protonation of chitosan may explain the electrostatic attraction of this anionic dye and that its optimum pH is close to 3. Preliminary protonation of amine groups (obtained by contact with a sulfuric acid solution) reduced the variation of solution pH following sorbent addition but significantly reduced sorption performance: the maximum sorption capacity of raw chitosan, 525 mg dye/g (0.84 mmol dye/g), was halved by acidic preconditioning. The acidic conditioning also reduced the kinetic rate—the time necessary to reach equilibrium increased up to threefold depending on the experimental conditions. The size of sorbent particles influenced sorption kinetics and equilibrium because of resistance to intraparticle diffusion, but the sorption appeared to occur not only at the surface of the sorbent but also in the intraparticle network of the polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1073–1080, 2003     

Biosorption of Naphthalene from Refinery Simulated Waste-Water on Blank Alginate Beads and Immobilized Dead Algal Cells

Abstract

The potential use of blank alginate beads and immobilized dead algal cells for the removal of naphthalene from aqueous solutions was investigated in this study. The effects of contact time, solution pH, and naphthalene concentration on the sorption of naphthalene on blank alginate beads or immobilized dead algal cells were studied. The effect of the presence of other pollutants on the sorption of naphthalene on immobilized dead algal cells was also studied.

Batch adsorption experiments showed that the removal of naphthalene on both sorbents was pH dependent and significant removal of naphthalene was obtained at pH 4. Dynamic sorption experiments revealed that the biosorption of naphthalene on either sorbent was rapid where the equilibrium uptake occurred within 10 minutes, and the biosorption of naphthalene on either sorbent followed the pseudo-second order kinetics. Analysis of the equilibrium sorption data showed that naphthalene sorption on either sorbent could be fitted to the Langmuir, Freundlich, and Dubinin-Radushkevich (D–R) isotherm equations. Competitive biosorption experiments showed that biosorption of naphthalene on immobilized dead algal cells was adversely affected by the presence of either heavy metals such as copper and nickel, and chelating agents such as citric acid.     

Diffusion kinetic study of cadmium(II) biosorption by Aeromonas caviae

The removal of cadmium from aqueous solution by sorption on Aeromonas caviae particles was investigated in a well‐stirred batch reactor. Equilibrium and kinetic experiments were performed at various initial bulk concentrations, biomass loads and temperatures. Biosorption equilibrium was established in about 1 h and biosorption was well described by the Langmuir and Freundlich biosorption isotherms. The maximum biosorption capacity was found as 155.32 mg Cd(II) g^?1 at 20 °C. The obtained sorption capacity is appreciably high for most experimental conditions; so A caviae may be considered as a suitable biosorbent for the removal of cadmium. Moreover, the sorption rate of cadmium onto A caviae particles was particularly sensitive to initial bulk concentration and solid load. A detailed analysis was conducted, examining several diffusion (external and intraparticle) kinetic models in order to identify a suitable rate expression. The results are discussed and indicate that biosorption of cadmium is a complex process that is described more correctly by more than one model. Copyright © 2004 Society of Chemical Industry     

Sorptive sequestration of 2‐chlorophenol by zeolitic materials derived from bagasse fly ash

BACKGROUND: Water pollution by toxic organic compounds is of great concern and increasingly there are demands for effective sorbents to remove them. Bagasse fly ash, a sugar industry solid waste with disposal problems, was utilized as a source for the synthesis of zeolitic material. The efficiency of virgin and synthesized material was examined for the sorption of 2‐chlorophenol. RESULTS: Zeolitic materials have been synthesized by alkaline hydrothermal and fusion methods. Zeolite P and Analcime were the major components of the zeolitic material. These materials were characterized by XRF, PXRD, FTIR and SEM and were found to have improved morphology with new crystalline phases. Batch sorption experiments for the removal of 2‐chlorophenol by virgin and zeolitic materials were carried out to evaluate isotherm capacities and kinetics of sorption processes. The Langmuir isotherm better fits the equilibrium data which concur with physical sorption. Kinetic studies showed better correlation coefficients for pseudo‐second‐order and intraparticle diffusion model, confirming that the sorption rate was controlled by film diffusion followed by pore diffusion. Desorption studies were performed to regenerate the activity of the spent sorbents. The practical utility of sorbents was tested by column study. CONCLUSION: Bagasse fly ash, readily available at very low cost was successfully converted into zeolitic material. The synthesized zeolitic material showed enhanced capacities for the sorption of 2‐chlorophenol and can be utilized as a low cost sorbent for treatment of phenolic waste‐water. Copyright © 2011 Society of Chemical Industry     

Biosorption of Zinc from Aqueous Solutions by Rice Bran: Kinetics and Equilibrium Studies

Abstract

Rice bran, an agricultural by‐product, was used for the removal of zinc ions from aqueous solution. The work considered the determination of zinc‐biomass equilibrium data in batch system. These studies were carried out in order to determine some operational parameters of zinc sorption such as the time required for the Zinc‐biosorbent equilibrium, the effects of biomass particle size, pH, and temperature. The results showed that pH has an importance effect on zinc biosorption capacity. The biosorbent size also affects the zinc biosorption capacity. The sorption process follows pseudo‐second‐order kinetics. The intraparticle diffusion may be the rate‐controlling step involved in the adsorption zinc ions onto the rice bran up to 30 min. The equilibrium data could be best fitted by the Langmuir sorption isotherm equation over the entire concentration range (40–160 mg/dm³). Thermodynamic parameters, such as ΔG°, ΔH°, ΔS°, have been calculated. The thermodynamics of zinc ion/rice bran system indicate spontaneous and endothermic nature of the process.     

Biosorption of Zn(II) by orange waste in batch and packed‐bed systems

BACKGROUND: This research provides new insights into the biosorption of zinc on a waste product from the orange juice industry. Optimal operating conditions maximizing percentage zinc removal were determined in batch and fixed‐bed systems. Biomass was characterized by FTIR spectroscopy and by major cation content in order to better understand the biosorpion mechanism. Zn‐loaded orange waste was proposed to be used as an alternative fuel in cement kilns. RESULTS: Sorption capacity was strongly affected by biosorbent dose and solution pH, and was not strongly sensitive to particle size under the experimental conditions studied. Equilibrium data were successfully described by a Langmuir model and sorption kinetic data were adequately modelled with the pseudo‐second‐order and Elovich rate equation. The biomass was found to possess high sorption capacity (q_max = 0.664 mmol g^?1) and biosorption equilibrium was established in less than 3 h. Experimental breakthrough curves were adequately fitted to the Thomas model and the dose–response model, obtaining sorption capacities in continuous assays higher than those found in batch mode. Characterization of the biomass suggested the possible contribution of carboxyl and hydroxyl groups of biomass in Zn²⁺ biosorption and it also highlighted the important role of light metal ions in a possible ion‐exchange mechanism. CONCLUSIONS: Orange waste could be used as an effective and low‐cost alternative biosorbent material for zinc removal from aqueous solution. Copyright © 2010 Society of Chemical Industry     

CYPHOS IL 101 (Tetradecyl(Trihexyl)Phosphonium Chloride) Immobilized in Biopolymer Capsules for Hg(II) Recovery from HCl Solutions

Abstract

A composite polymer (made of gelatin and alginate) was used for the synthesis of Cyphos IL 101-immobilized resins. These resins (with varying size and different ionic liquid (IL) content) have been tested for the recovery of mercury from concentrated HCl solutions (0.1–5 M HCl concentrations). Prior to the study of sorption performance on resins, the reactivity of Cyphos IL 101 versus mercury was tested using solvent extraction methodology. These results showed that the extraction was hardly affected by the concentration of HCl and that an ion exchange mechanism was probably involved in metal recovery (binding of HgCl₄ ^2-). The performance of these resins for Hg(II) recovery was tested through sorption isotherms and uptake kinetics, investigating the effect of resin size, ionic liquid content, metal concentration, agitation speed, and resin state (dry state versus wet state). Sorption capacity (which was proportional to the IL content) can reached up to 150 mg Hg g^?1 in 1 M HCl; this sorption capacity was decreased by increasing chloride concentration. The kinetics were described well by the pseudo-second order equation and by the intraparticle diffusion equation (the so-called Crank's equation). The intraparticle diffusion coefficient was in the range of 10^?11–1.2 × 10^?10 m² min^?1. The kinetic profiles were controlled by the IL content, sorbent dosage, and the sorbent particle size. Drying of the resins significantly decreased diffusion rates in the resins. The presence of competitor metals did not affect sorption capacity except when stable chloro-anionic species such as in the case of Zn(II) were formed. Mercury can be desorbed using 6 M nitric acid solutions; and the sorbent can be recycled for at least six sorption/desorption cycles without significant decrease in the sorption performance.     

Removal of Copper (II) Ions from Aqueous Solutions using Na‐mordenite

Abstract

The potential to remove copper (II) ions from aqueous solutions using Na‐mordenite, a common zeolite mineral, was thoroughly investigated. The effects of relevant parameters solution pH, adsorbent dose, ionic strength, and temperature on copper (II) adsorption capacity were examined. The sorption data followed the Langmuir, Freundlich, and Dubinin‐Radushkevich (D‐R) isotherms. The maximum sorption capacity was found to be 10.69 mg/g at pH 6, initial concentration of 40 mg/dm³, and temperature of 40°C. Different thermodynamic parameters viz., changes in standard free energy (ΔG⁰), enthalpy (ΔH⁰), and entropy (ΔS⁰) have also been evaluated and the results show that the sorption process was spontaneous and endothermic in nature. The dynamics of the sorption process were studied and the values of rate constant of adsorption, rate constant of intraparticle diffusion were calculated. The activation energy (E_a) was found to be 11.25 kJ/mol in the present study, indicating a chemical sorption process involving weak interactions between sorbent and sorbate. The interaction between copper (II) ions and Na‐mordenite is mainly attributable to ion exchange. The sorption capacity increased with the increase of solution pH and the decrease of ionic strength and adsorbent dose. The Na‐mordenite can be used to separate copper (II) ions from aqueous solutions.     

Investigation on Purification of Saturated LiNO3 Solution Using Titanium Phosphate Ion Exchanger: Kinetics Study

Lithium compounds are of high interest to many industries. The presence of undesirable impurities in Li precursors leads to uncontrolled change in the functional properties of final compounds. Therefore, the development of reliable methods for lithium salt purification is considered a key factor for their application in various industries. This work focuses on the application of a titanium phosphate ion exchanger (Li-TiOP) toward Cu²⁺, Co²⁺, Mn²⁺, Ni²⁺, and Cr³⁺ ions in the purification of a saturated LiNO₃ solution. The sorption kinetics of the selected ions, considering external and internal mass transfer, as well as chemical interaction, were deeply studied. The kinetic study showed that the values of intraparticle diffusion rate and effective diffusion coefficients for the studied ions decreased in the following order: Cr(III) ˃ Cu(II) Mn(II) ˃ Co(II) ˃ Ni(II). For all the selected ions, chemical interaction was described with a pseudo-second-order reaction model. The sorption kinetics were controlled by the size of the solvated metal ion, its effective charge, the electronic structure of the adsorbed ion, and the interaction with the functional groups of the sorbent. Due to fast kinetics, the high degree of removal of trace quantities of the impurities this material gives it consideration as a promising sorbent for the deep purification of lithium salts.     

Removal of phosphate anions from aqueous solutions using polypyrrole‐coated sawdust as a novel sorbent

This work was focused on the removal of phosphate ions using polypyrrole‐coated sawdust as a novel cost‐effective sorbent. The phosphate uptake followed the Langmuir sorption isotherm, and the sorption capacity at 20, 35, and 50°C was found to be 17.33, 23.41, and 30.39 mg/g, respectively; this indicated favorable sorption at higher temperatures. The kinetic uptake data were modeled with the Lagergren equation, first‐order and second‐order kinetic models, and the simple Elovich model. The results indicated that the Lagergren model best described the uptake data. The intraparticle diffusion coefficient, as determined for 250–211‐ and 630–600‐μm sorbent particles at 20°C, was found to be 287.3 × 10^?2 and 228.3 × 10^?2 mg g^?1 min^?1, respectively. The intraparticle diffusion was also confirmed with the Bangham equation. The sorption mean free energy, calculated with the Dubinin–Radushkevich equation, was found to be 10.98 kJ/mol, thus confirming an ion‐exchange regulated sorption process. The positive value of the enthalpy change (i.e., 4.23 kJ/mol) confirmed the endothermic nature of the sorption process. The negative values of the change in the standard free energy were indicative of the spontaneous nature of the sorption process. Finally, the activation energy of the sorption process for 250–212‐μm particles, determined with the Arrhenius equation, was found to be 41.68 J/mol. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Removal of Basic Blue 3 by sorption onto a weak acid acrylic resin

A weak acid acrylic resin was used as an adsorbent for the investigation of Basic Blue 3 (BB3) adsorption kinetics, isotherms, and thermodynamic parameters. Batch adsorption studies were carried out to evaluate the effect of pH, contact time, initial concentration (28–100 mg/g), adsorbent dose (0.05–0.3 g), and temperature (290–323 K) on the removal of BB3. The adsorption equilibrium data were analyzed by the Langmuir, Temkin, and Freundlich isotherm models, with the best fitting being the first one. The adsorption capacity (Q_o) increased with increasing initial dye concentration, adsorbent dose, and temperature; the highest maximum Q_o (59.53 mg/g) was obtained at 323 K. Pseudo‐first‐order and pseudo‐second‐order kinetic models and intraparticle diffusion models were used to analyze the kinetic data; good agreement between the experimental and calculated amounts of dye adsorbed at equilibrium were obtained for the pseudo‐second‐order kinetic models for the entire investigated concentrations domain. Various thermodynamic parameters, such as standard enthalpy of adsorption (ΔH^o = 88.817 kJ/mol), standard entropy of adsorption (ΔS^o = 0.307 kJ mol^?1 K^?1), and Gibbs free energy (ΔG^o < 0, for all temperatures investigated), were evaluated and revealed that the adsorption process was endothermic and favorable. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009