Equilibrium sorption of C.I.Basic Red 18 by carboxymethyl cellulose membranes

The equilibrium sorption of a cationic dye, C.I.Basic Red 18, by a partially carboxymethylated cellulose membrane at pH 4.2 was investigated. The sorption isotherm was interpreted by considering a cooperative mode of binding of the dye by the polymer. The intrinsic binding constantK, the number of consecutive polymer residues occupied by a single dye moleculen, and the cooperativity parameter were determined. In the case of the polymer with high content of carboxylate groups an additional mode of dye binding was presumed.     

Adsorption of Bismarck Brown by Iron Oxide Nanosphere and Its Modified Form

In the present study, adsorption of Bismarck Brown (BB) dye onto iron oxide nanospheres (IONs) and modified IONs by HCl from aqueous solution was investigated. The IONs was synthesized by solvothermal method and then modified by HCl. The high magnetic properties of both adsorbents lead to facial separation from aqueous solution by an external magnet. The results show that the modification of adsorbent cause higher adsorption capacity for removal of BB from aqueous solution. The prepared adsorbents were characterized by SEM, XRD, FTIR, and ATR-IR techniques. The adsorption kinetic and equilibrium data were fitted with different models. The results show that the equilibrium and kinetic data were best fitted with Langmuir–Freundlich isotherm and fractal-like pseudo-second-order kinetic model, respectively. The effects of pH and temperature have also been investigated.     

Removal of reactive dye brilliant red HE-3B from aqueous solutions by hydrolyzed polyacrylonitrile fibres: equilibrium and kinetics modelling

A cheap and efficient fibrous hydrolyzed polyacrylonitrile (HPAN) sorbent was obtained by alkaline hydrolysis of Romanian polyacrylonitrile fibres. Scanning electronic microscopy and infrared spectroscopy were used to characterize the hydrolyzed product and to confirm its functionalization. The adsorptive potential of the proposed sorbent for reactive dye Brilliant Red HE-3B removal from aqueous solutions of pH=2 was examined by the batch technique as a function of dye concentration, temperature solution and contact time. The Freundlich, Langmuir and Dubinin-Radushkevich adsorption models were applied to describe equilibrium sorption data and to determine the corresponding isotherm constants. The thermodynamic parameters ΔG, ΔH and ΔS were also determined; the values obtained show that sorption of reactive dye on HPAN fibres is a spontaneous, endothermic and entropy-driven process. The kinetics of sorption of the reactive dye were analyzed using pseudo-first order and pseudo-second order kinetic models. The kinetic data fitted well to pseudo-second order kinetics, indicating the chemisorption of reactive dye onto the fibrous sorbent. The sorption mechanism of the dye onto hydrolyzed fibres was confirmed by FTIR spectroscopy. The dye-loaded HPAN sorbent can be regenerated by treatment with 0.1M NaOH and the regenerated sorbent may be reused in several adsorption-desorption cycles. The results of this study provided evidence that the HPAN fibres are effective for removing reactive dye Brilliant Red HE-3B from aqueous effluents.      

Adsorption of Cd(II) by Sol-Gel Silica Doped with N-(dipropylcarbamothioyl)thiophene-2-carboxamide

Sol-gel silica was doped with N,N-(dipropylcarbamothioyl) thiophene-2-carboxamide to investigate the sorption of cadmium (Cd) ions from aqueous media. In doped sol-gel silica, the large reagent molecules entrap into pores, whereas, small metal ions diffuse into pores where they make complex with doped reagent. This complexation can be accomplished by either ion exchange or chelation. Doped sol-gel sorbent was applied for removal of Cd(II) from aqueous solution in our study. Adsorption kinetics, adsorption isotherm, equilibration time, effect of initial concentration of adsorbate, and pH effect on the metal removal were studied to optimize the conditions. The prepared adsorbent shows rapid equilibrium and high stability toward high temperature and applied medium. In addition, desorption of metal ions was carried out by 1 M HCl and, thereafter, sol-gel silica adsorbent was regenerated and reused periodically.     

Equilibrium, kinetic, and thermodynamic studies of Basic Blue 9 dye sorption on agro-industrial lignocellulosic materials

The sorptive potential of some lignocellulosic agro-industrial wastes (sunflower seed shells and corn cob) for Basic Blue 9 cationic dye removal from aqueous solutions was examined using the batch technique. The Freundlich, Langmuir, and Dubinin-Radushkevich isotherm models were used in order to determine the quantitative parameters of sorption. The Langmuir isotherm model indicated a maximum sorption capacity for these materials in the range of 40–50 mg dye per g (25°C), slightly higher for corn cob than for sunflower seed shells. The values of the thermodynamic parameters showed that the retention of cationic dye is a spontaneous and endothermic process. The application of pseudo-first order and pseudo-second order intraparticle diffusion models, and a Boyd — Reichenberg model for kinetic data interpretation suggested that sorption of Basic Blue 9 dye onto the studied materials is a process where both surface sorption and intraparticle diffusion contributed to the rate-limiting step. These lignocellulosic wastes can be used with good efficiency for dye removal from aqueous effluents.      

Study of Removal of Cationic Dye from Waste Aqua Using Chromatographic Grade Silica as Adsorbent

The adsorption of cationic dye, Basic Red 13 from aqueous solution onto silica has been studied. The time growth adsorption as a function of the amount of adsorbent, pH, initial dye concentration as well as the temperature was measured of the system. Adsorption was found to follow a first-order process. Various isotherm and thermodynamic parameters for the adsorption of dye have been calculated. Isotherms were used to identify formation of either monolayer or multilayer formation whereas thermodynamic and other parameter indicated that the dye adsorption process was physisoption as well as spontaneous and exothermic in nature.     

Diffusion Mechanisms of Biosorption of Cr(VI) onto Powdered Cotton Stalk

The present study investigates biosorption diffusion mechanism for the removal of toxic hexavalent chromium from aqueous solution using powdered cotton stalk an agricultural waste biomass. The effects of pH, temperature, adsorption isotherms, adsorption kinetics, and thermodynamic on chromium biosorption were investigated. The results showed that a maximum removal efficiency of 95% was achieved at pH 2. The pH at zero point charge (pH_zpc) on biosorbent surface was 4.3. The adsorption kinetics showed that the pseudo-second order rate expression fitted well the biosrption process. The equilibrium isotherm was measured experimentally and results were analyzed by Langmuir, Freundlich, and Temkin isotherms using linearized correlation coefficients. The significant parameters for isotherms were determined. The Langmuir adsorption isotherm relative to two other isotherms was found to fit the equilibrium data best for chromium adsorption. Thermodynamic studies reveal that the biosorption of Cr(VI) on cotton stalk was endothermic, spontaneous and occurs with increase in disorder at solid-liquid interface. Adsorption diffusion kinetic was further analyzed and showed that biosorption mechanism was totally controlled by intraparticle diffusion mechanism.     

Efficient Sorption of Basic Organic Dyes from Aqueous Solution Using Green Synthesized Silver Nanoparticles Beads

In this article, the potential of alginate stabilized silver nanoparticles beads for efficient sorption of methylene blue, malachite green, and rhodamine B from aqueous solutions was investigated. The adsorption data have been correlated with both Freundlich and Langmuir adsorption models. The kinetic studies for dyes adsorption showed rapid sorption dynamics by second-order kinetic model. The common problem of classical adsorbents towards efficient recyclability was overcome when alginate stabilized silver nanoparticles beads was used. The alginate stabilized silver nanoparticles beads were successfully recycled for 25 successive adsorption-desorption cycles indicating its high reusability.     

Dried Biomass of Activated Sludge for Cu2+ Adsorption: Behaviors and Mechanisms

Activated sludge was tested for its ability to remove Cu²⁺ from aqueous solution. The effects of various experimental parameters (initial pH, initial Cu²⁺ concentration, adsorbent dosage, and temperature) on Cu²⁺ adsorption were evaluated. The Langmuir isotherm model well described the adsorption of Cu²⁺ onto activated sludge. The pseudo-second-order kinetic equation was appropriate for describing the kinetic performance of the sorption. Furthermore, Webber–Morris models indicated that the sorption of Cu²⁺ was generally found to involve with the intraparticle diffusion process. Parameters of adsorption thermodynamic suggested that the interaction of Cu²⁺ adsorbed by sludge was spontaneous and exothermic. Activated sludge was characterized by Fourier transform infrared spectroscopy analysis and results showed that active groups such as –OH, –COOH, –NH₂ were involved in Cu²⁺ adsorption. Zeta potential analysis demonstrated inner-sphere adsorption for Cu²⁺ adsorption on sludge.     

Preparation of Magnetic-Activated Carbon Nanocomposite and Its Application for Dye Removal from Aqueous Solution

A nanocomposite of activated carbon and iron oxide was prepared and characterized by x-ray diffraction and scanning electron microscopy methods. The prepared magnetic nanocomposite can be separated easily from water by an external magnet. The prepared magnetic nanocomposite was used as adsorbent for removal of Bismarck Brown (B.B.) as a dye pollutant from water. The adsorption studies include both equilibrium and kinetic aspects, and the results were modeled with different equations. The obtained results indicate that the prepared magnetic nanocomposite of iron oxide and activated carbon is one of the best adsorbents for the removal of B.B. from aqueous solution.     

Comparison Between Long- and Short-Chain Organoclays for Oil Removal from Salty Waters

Two commercial powdered organoclays, Cloisite 15A and Cloisite 30B, as long-chain organoclays, and two organically modified clays with tetramethylammonium chloride (TMA-clay), as short-chain organoclays were used in this study to investigate their potentials for crude oil removal from salty waters. Batch experiments were performed to examine the effect of contact time and pH on the adsorption process. The results showed that the equilibrium time was reached within 25–30 and 50–55 minutes of contact time for long and short-chain organoclays, respectively. In addition, adsorption isotherms were obtained at an optimum pH value of 11.73 and temperature of 19°C for which initial oil contents varied in the range of 100 to 2000 ppm. Experimental results indicated that the sorption of oil onto Cloisite 15A, Cloisite 30B and the organically modified clays can be described by Freundlich isotherm and oil sorption followed the order of modified Cloisite Na > Cloisite 30B > Cloisite 15A > a modified local clay.      

Sorption Studies of Acid Dye by Mixed Sorbents

The sorption of Acid Blue 9 onto the mixture of activated clay and activated carbon has been studied in terms of pseudo-first order and pseudo-second order chemical sorption processes. The batch sorption model, based on the assumption of a pseudo-second order mechanism, has been developed to predict the rate constant of sorption and the equilibrium capacity with the effect of initial dye concentration, mass of mixed sorbent, temperature and initial solution pH. The rates of sorption were found to conform to pseudo-second order kinetics with good correlation. Batch isotherm studies showed that the sorption of Acid Blue 9 by the mixed sorbent from aqueous solution was described by the Langmuir isotherm equation. A comparison of the evaluated equilibrium capacity of sorption has been made by the pseudo-second order rate equation as well as by the Langmuir isotherm and operating line method. In addition, an activation energy of sorption has also been determined based on the pseudo-second order rate constants.     

Adsorptive Removal of Thorium(IV) from Aqueous Solutions Using Synthesized Polyamidoxime Chelating Resin: Equilibrium,Kinetic, and Thermodynamic Studies

In this study, an amidoximated chelating ion exchange resin was prepared by poly-acrylonitrile (PAN) grafted potato starch. The adsorbent characterizations such as specific surface area, pore volume, average pore radius, and Fourier transform infrared (FTIR) spectrum of the resin were measured. The effects of pH, adsorbent dosage, contact time, initial concentration of thorium ion, and temperature on adsorption of thorium ion from aqueous solutions were investigated. Four isotherm models including Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin were applied to analyze the equilibrium isotherm data. The results showed that Langmuir and Temkin models had a good agreement with experimental data. The maximum capacity of the adsorbent using the Langmuir isotherm model was 227.27 mg · g^?1. The kinetic models like pseudo-first-order, pseudo-second-order, Elovich, and intraparticle were examined to describe the adsorption process. The kinetics of the adsorption process was found to follow the pseudo-second-order kinetic model. The thermodynamic parameters (ΔG°, ΔH°, ΔS°) were also calculated using equilibrium constant values at various temperatures (25, 35, 45, 55°C) and the positive value for ΔH° showed an endothermic adsorption process. The study suggests that the prepared adsorbent has promising potential for the removal of thorium from wastewaters.      

Adsorption of Lead Ion Using Polymer-Modified Wheat Straw Carboxymethylcellulose

The wheat straw carboxymethylcellulose (WSC), a typical natural polymer, was modified by functional poly(acrylic acid) (PAA) with in situ polymerization, which afforded natural and synthetic polymer composite (WSC/PAA). The polymer (WSC/PAA) was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis techniques. WSC/PAA was used as polymer adsorbent for removing Pb(II) ions in wastewater. The removal rate of 99.8% was obtained when the experimental conditions were chosen as follows: initial Pb(II) ion concentration; 600 mg/L, WSC/PAA concentration; 0.1 g/100 mL, pH; 5.0, contact time; 60 minutes at 20°C. Adsorption dynamics were consistent with pseudo-second-order kinetic model and the isotherm model can meet the Langmuir isotherm.     

Competitive Sorption of Copper and Nickel Ions from Aqueous Solution Using Peat

Bicomponent aqueous solutions of copper and nickel ions have been used to investigate the sorption of metal ions onto peat. Peat, a low cost sorbent, has shown a high capacity for the sorption of single component metal ions attributed to extensive carboxylic acids within its structure. Copper and nickel ions were selected as typical metals in the effluents of electroplating industries. The effects of competitive sorption in batch systems were studied at various metal ion concentrations. In this study the Butler and Ockrent model was modified using a coefficient, . Two models were developed based on the interaction coefficient . The first model incorporates a constant fixed factor for each metal ion into the Butler-Ockrent equation. The second model incorporates a variable factor into the Butler-Ockrent equation; this interaction factor varies as a function of sorbent surface coverage. Predicted equilibrium data are found to be in excellent agreement with experimental values using both modified models for various mole ratios of copper and nickel ions in competitive sorption.     

Dynamic and Rheological Properties of Span 80 at Liquid–Liquid Interfaces

The adsorption characteristics of Span 80 at liquid/liquid interfaces were investigated. The equilibrium interfacial tension values were successfully fitted with a Langmuir isotherm resulting in the determination of a mean molecular area from 25 to 35 Å²/mol. The measured interfacial tension values and deduced adsorption parameters depend on the experimental technique used to obtain them, either Du Noüy ring or profile analysis tensiometry. Two possible explanations to such phenomenon are provided. Adsorption kinetics of Span 80 at liquid/liquid interfaces were studied, and it was concluded that the diffusion of Span 80 molecules from the bulk is the rate determining step of the adsorption. Finally the interfacial rheology properties were investigated and compared to the Lucassen–van den Tempel model. A good match was obtained when the isotherm parameters determined by profile analysis tensiometry were used.