Polyamine Functionalized Magnetite Nanoparticles as Novel Adsorbents for Cu(II) Removal from Aqueous Solutions

Three novel magnetic adsorbents were synthesized through the immobilization of di-, tri-, and tetraamine onto the surface of silica coated magnetite nanoparticles. The adsorbents were characterized by XRD patterns, FTIR spectroscopy, elemental and thermogravimetric analysis, magnetic measurements, SEM/TEM, EDX spectroscopy, and N₂ adsorption/desorption isotherms. Their capacity to remove copper ions from aqueous solutions was investigated and discussed comparatively. The equilibrium data were analyzed using Langmuir and Freundlich isotherms. The kinetics was evaluated using the pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. The best interpretation for the equilibrium data was given by the Langmuir isotherm for the tri- and tetraamine functionalized adsorbents, while for the diamine functionalized adsorbent the Freundlich model seemed to be better. The kinetic data were well fitted to the pseudo-second-order model. The overall rate of adsorption was significantly influenced by external mass transfer and intraparticle diffusion. It was observed that the adsorption capacity at room temperature decreased as the length of polyamine chain immobilized on the adsorbent surface increased, the maximum adsorption capacities being 52.3 mg g^?1 for 1,3-diaminopropan functionalized adsorbent, 44.2 mg g^?1 for diethylenetriamine functionalized adsorbent, and 39.2 mg g^?1 for triethylenetetramine functionalized adsorbent. The sorption process proved to be highly dependent of pH. The results of the present work recommend these materials as potential candidates for copper removal from aqueous solutions.     

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.     

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.     

Activated carbon derived from macadamia nut shells: an effective adsorbent for phenol removal

In this study, activated carbon based on the waste macadamia nut shells (MAC) was investigated for potential use as an adsorbent for phenol removal. The pseudo second-order kinetic model best described the adsorption process. The extent of the phenol adsorption was affected by the pH solution and the adsorbent dosage. Equilibrium data fitted well to the Langmuir model with a maximum adsorption capacity of 341 mg g^?1. The calculated thermodynamic parameters suggested that the phenol adsorption onto MAC was physisorptive, spontaneous and exothermic in nature. Phenol desorption from loaded adsorbent was achieved by using 0.1 mol L^?1 NaOH, ethanol (100 %) and deionized water.     

Palladium,silver, and zinc oxide nanoparticles loaded on activated carbon as adsorbent for removal of bromophenol red from aqueous solution

The adsorption of bromophenol red (BPR) onto three adsorbents including palladium, silver and zinc oxide nanoparticles loaded on activated carbon (Pd-NP-AC, Ag-NP-AC and ZnO-NP-AC) in a batch system has been studied and the influence of various parameters has been optimized. The influence of time on removal of BPR on all adsorbent was investigated and experimental data were analyzed by four kinetic models including pseudo first and second-order, Elovich and the intraparticle diffusion equations. Following fitting the experimental data to these models, the respective parameters of each model such as rate constants, equilibrium adsorption capacities and correlation coefficients for each model were investigated and based on well known criterion their applicability was judged. It was seen that the adsorption of BPR onto all adsorbents sufficiently described by the pseudo second-order equation in addition to interparticle diffusion model. The adsorption of BPR on all adsorbent was investigated at various concentration of dye and the experimental equilibrium data were analyzed and fitted to the Langmuir, Freundlich, Tempkin, Dubinin, and Radushkevich equations. A single stage in batch process was efficient and suitable for all adsorbents using the Langmuir isotherm with maximum adsorption of 143 mg g^?1 for Pd-NP-AC, 250 mg g^?1 for Ag-NP-AC and 200 mg g^?1 for ZnO-NR-AC. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° for Pd-NP-AC adsorbent were calculated.     

Starch/rice husk ash based superabsorbent composite: high methylene blue removal efficiency

Superabsorbent hydrogels composites based on the biopolymer starch (ST) and rice husk ash (RHA) were successfully developed and tested towards the removal of methylene blue (MB), a cationic dye. RHA content hit the morphology, mechanical and water uptake properties of the composite. Batch adsorption experiments, carried out under pH 5 at 33 °C and with 2000 mg L^?1 as the initial concentration of MB, showed that at 5 wt% RHA the composite exhibited a remarkable adsorption capacity reaching up to 1906.3 mg g^?1 within 60 min. The adsorption kinetics followed the pseudo-second-order model and intraparticle diffusion was involved in this process. The Langmuir adsorption isotherm suggested a monolayer formation and spontaneous process. Thermodynamic parameters confirmed the spontaneity of the adsorption and suggested electrostatic interaction among the cationic dye molecules and the anionic adsorption sites on the adsorbent surface. FTIR analysis confirmed the adsorption process occurs via electrostatic mechanism associated with hydrophobic interactions. The adsorbents showed reusability with slight loss of adsorption capacity in five consecutive adsorption/desorption cycles. These results demonstrate ST/RHA superabsorbent composite as a low-cost, eco-friendly, robust and powerful adsorbent material for wastewater remediation.     

Methylene Blue Adsorption on Natural and Modified Clays

Toxic methylene blue dye is removed from water by accumulating it on the surface of clay minerals. Clay adsorbents are obtained from kaolinite, montmorillonite, and their acid activated forms. The adsorption experiments are carried out in a batch process in environments of different pH, initial dye concentration, amount of clay, interaction time, and temperature. Adsorption of dye is best described by second order kinetics. In the temperature range of 303 to 333 K, the Langmuir monolayer capacity for three kaolinite species increased from 45.5 to 56.5 mg g^?1, 45.9 to 57.8 mg g^?1, 46.3 to 58.8 mg g^?1, and for three montmorillonites species from 163.9 to 181.8 mg g^?1, 166.7 to 188.8 mg g^?1, and 172.4 to 192.3 mg g^?1. The interaction is an endothermic process driven by entropy increase and spontaneous adsorptive accumulation is ensured by favorable Gibbs energy decrease. It is found that acid activation enhances the adsorption capacity of kaolinite and montmorillonite.     

Sodic and Acidic Crystalline Lamellar Magadiite Adsorbents for the Removal of Methylene Blue from Aqueous Solutions: Kinetic and Equilibrium Studies

The present study reports the feasibility of two synthetic crystalline lamellar nano-silicates, sodic magadiite (Na-mag) and its converted acidic form (H-mag), as alternative adsorbents for the removal of the dye methylene blue (MB) from aqueous solutions. The ability of these adsorbents for removing the dye was explored through the batch adsorption procedure. Effects such as the pH and the adsorbent dosage on the adsorption capacities were explored. Four kinetic models were applied, the adsorption being best fitted to a fractionary-order kinetic model. The kinetic data were also adjusted to an intra-particle diffusion model to give two linear regions, indicating that the kinetics of adsorption follows multiple sorption rates. The equilibrium data were fitted to Langmuir, Freundlich, Sips, and Redlich-Peterson isotherm models. The maxima adsorption capacities for MB of Na-mag and H-mag were 331 and 173 mg g^?1, respectively.     

Investigation of Cationic Dye Adsorption from Water onto Acetic Acid Lignin

An adsorbent was prepared from acetic acid lignin (AAL) to investigate the adsorption mechanism of methylene blue (MB) from water. AAL was first deacetylated in NaOH aqueous solution and then fractionated by methanol to prepare adsorbents with various acidic hydroxy groups. The adsorption capacities of MB increased with the increase in initial pH and with the decrease in adsorbent dosage. The results of adsorption kinetics indicated the dye uptake process is a chemisorption. The adsorption capacity of lignin for MB adsorption increased from 18.2 to 63.3 mg g^?1 as AAL was deacetylated and fractionated.     

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.     

Adsorptive removal of congo red dye (CR) from aqueous solution by Cornulaca monacantha stem and biomass-based activated carbon: isotherm,kinetics and thermodynamics

Cornulaca monacantha stem (CS) and biomass stem-based activated carbon (CS^AC) were explored for the removal of congo red (CR) dye from water system. The biomaterial was characterized using Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) and field emission scanning electron microscope (FESEM). The BET surface area of biomass stem-based activated carbon (CS^AC) was recorded to be 304.27 m²/g. The influence of different parameters such as initial CR concentration, adsorbent dosage, contact time, adsorbate pH and temperature onto CR adsorption were studied.The maximum adsorption of CR dye 97.19% and 86.43% were achieved at 55°C using CS^AC and CS adsorbents, respectively. The isotherm, kinetics and thermodynamic study were also investigated to explore the adsorption mechanism. The adsorption isotherm closely follow the Langmuir model (R² = 0.99) suggesting the monolayer adsorption of CR dye. Kinetic results indicated that pseudo second-order and Elovich model provide the better regression coefficient. Thermodynamic study revealed the feasible, spontaneous and endothermic nature of adsorption process. The regeneration study implies that adsorbent was efficiently recovered from CR dye with 0.01 mol/L NaOH solution. The CS^AC adsorbent possesses 75.75% uptake for CR dyes after 6th cycles of desorption-adsorption, respectively. .     

Adsorptive removal of cationic dye from aqueous solutions by ZnO/ZnMn2O4 nanocomposite

The ZnO/ZnMn₂O₄ nanocomposite (ZnMn) was used as adsorbent for the removal of cationic dye Basic Yellow 28 (BY28) from aqueous solutions. The adsorbent was characterized by X-ray diffraction, scanning electron microscope, TEM, Fourier transform infrared ray, BET, particle size distribution and zeta potential measurements. The adsorption parameters, such as temperature, pH and initial dye concentration, were studied. Kinetic adsorption data were analyzed using the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. The Langmuir and Freundlich isotherm models were applied to fit the equilibrium data. The maximum adsorption capacity of BY28 was 48.8 mg g^?1. Various thermodynamic parameters, such as ΔG°, ΔH° and ΔS°, were calculated.     

EFFECT OF TEMPERATURE ON THE ADSORPTION OF METHYLENE BLUE DYE ONTO SULFURIC ACID–TREATED ORANGE PEEL

The present study explains the preparation and application of sulfuric acid–treated orange peel (STOP) as a new low-cost adsorbent in the removal of methylene blue (MB) dye from its aqueous solution. The effects of temperature on the operating parameters such as solution pH, adsorbent dose, initial MB dye concentration, and contact time were investigated for the removal of MB dye using STOP. The maximum adsorption of MB dye onto STOP took place in the following experimental conditions: pH of 8.0, adsorbent dose of 0.4 g, contact time of 45 min, and temperature of 30°C. The adsorption equilibrium data were tested by applying both the Langmuir and Freundlich isotherm models. It is observed that the Freundlich isotherm model fitted better than the Langmuir isotherm model, indicating multilayer adsorption, at all studied temperatures. The adsorption kinetic results showed that the pseudo-second-order model was more suitable to explain the adsorption of MB dye onto STOP. The adsorption mechanism results showed that the adsorption process was controlled by both the internal and external diffusion of MB dye molecules. The values of free energy change (ΔG ^o) and enthalpy change (ΔH ^o) indicated the spontaneous, feasible, and exothermic nature of the adsorption process. The maximum monolayer adsorption capacity of STOP was also compared with other low-cost adsorbents, and it was found that STOP was a better adsorbent for MB dye removal.     

Novel type of alginate gel‐based adsorbents for heavy metal removal

Various alginate gel‐based adsorbents were investigated for the removal of heavy metals: alginate beads, alginate capsules, and alginate gel‐coated adsorbent. Of these, alginate capsules showed the greatest Pb²⁺ uptake capacity of 1560 mg g^?1 of dry sodium alginate, and the alginate gel‐coated adsorbent, prepared simply by forming a thin alginate film on an inert matrix, achieved rapid adsorption equilibrium within 10 min. Adsorbed metals were readily removed from the alginate gel‐based adsorbents using eluents such as HNO₃ and could be reused for up to 10 adsorption–desorption cycles without marked loss of metal uptake capacity. Alginate gel‐coated adsorbents could be prepared in a dried state and have great application potential for the removal of heavy metals from contaminated water. Copyright © 2004 Society of Chemical Industry     

Powdered Activated Carbon-Microfiltration for Waste-Water Reuse

A range of activated carbon adsorbents have been assessed as pretreatment for microfiltration-based indirect potable reuse (IPR) pilot plant to evaluate the impact on combined membrane fouling and organics removal. Isotherm adsorption analysis showed wide variation between the different adsorbent materials with regards to organics removal and kinetics, and the removal for most of the reagents tested was found to be significantly influenced by temperature. The two commercial adsorbents with the highest removal rates and fastest kinetics were then each evaluated as pretreatment at pilot scale over a six hour period at two doses (5 and 25 mg/l) and operational fluxes (40 and 50 L m^?2 h^?1), based on a hollow fibre membrane module. One of the adsorbents provided a reduction in the irreversible fouling rate, and both were found to significantly improve the removal of organics.     

Removal of Tartrazine From Water by Adsorption with Electrochemical Regeneration

An innovative process has been developed at University of the Manchester in order to remove organic contaminants from wastewater using graphite intercalation compounds (GICs) as adsorbents with electrochemical regeneration. The present study has demonstrated the removal of tartrazine, from water by adsorption and electrochemical regeneration. The adsorption of tartrazine onto GIC adsorbent was shown to be a quick process, however, with extremely low adsorption capacity compared to porous adsorbents. Low adsorption capacity of the adsorbent is being compensated by rapid electrochemical regeneration associated with low energy consumption that makes the process cost-effective. Regeneration efficiency of around 100% could be obtained in an electrochemical cell by passing a charge of 18 C g^?1 for 18 min through a 10-mm thick adsorbent bed. A series of adsorption and regeneration cycles showed that there was little loss in adsorbent capacity, demonstrating that tartrazine loaded GIC adsorbent could be effectively regenerated electrochemically.     

Synthesis of High Surface Area MgAl2O4 Nanopowder as Adsorbent for Leather Dye Removal

Abstract

MgAl₂O₄ nanopowder has been prepared by alkoxides hydrolysis with further calcination at temperature of 700°C. The adsorption of a leather dye, Direct Black 38, onto this material was investigated. The sample was characterized by X-ray-diffraction (XRD), N₂ adsorption–desorption isotherm and Fourier transform infrared spectroscopy. The results showed that sample present a pure phase, and the average nanocrystal size of 8 nm, the BET surface area is about 206.5 m² · g^?1 and total pore volume is about 1.44 cm³ · g^?1. Adsorption kinetics data were modeled by film and pore diffusion model. The experimental isotherm was described by the Langmuir model. MgAl₂O₄ nanopowder presented a great removal efficiency of leather dye by adsorption process, with a maximum adsorption capacity of 833 mg of dye per gram of adsorbent.     

Adsorption of Cu2+ Cations from Aqueous Solution by S-doped TiO2

S-doped TiO₂ as a novel adsorbent for Cu²⁺ cations removal from aqueous solutions was synthesized by simple sol-gel process. Removal of Cu²⁺ cations from aqueous solutions was investigated with particular reference to the effects of initial Cu²⁺ cations concentration, pH-value, adsorbent dosage, and temperature on adsorption. It was found that the maximum adsorption capacity was 96.35 mg g^?1 at 328 K. The adsorption equilibrium isotherms and the kinetic data were well described by the Langmuir and pseudo-second-order kinetic models, respectively. The high uptake capability of S-doped TiO₂ makes it a potentially attractive adsorbent for the removal of heavy metal pollutants from aqueous solution.     

Uptake of anionic and cationic dyes by highly effective porous carbon adsorber based on industrial processing residues

In this work, we investigated the performance of porous carbon prepared from carob (Ceratonia siliqua L.) processing residues at optimized conditions for the removal of the Basic Green 4 (BG4) and Direct Red 28 (DR28) dyes from aqueous solutions. The influence of several parameters such as adsorbent dose, initial dye concentration, contact time and temperature was evaluated in batch adsorption experiments. Maximum adsorption capacities were observed as 769 mg g^?1 and 323 mg g^?1 for BG4 and DR28, respectively. These results suggest that BG4 and DR28 could be removed using a novel porous carbon from carob processing residues.