Sorption studies of neutral red dye onto poly(acrylamide‐co‐maleic acid)‐kaolinite/montmorillonite composites

In this study, a procedure for preparation of organic–inorganic composite was established. The procedure was based on gamma irradiation polymerization of polyacrylamide (PAAm) in presence of maleic acid (MA), clay minerals [kaolinite (K)], or [montmorillonite (M)] and methylenebisacrylamide (NMBA) as a crosslinker. The functionality of the produced adsorbents were assayed using FTIR spectroscopy, SEM, and XRD and were evaluated for sorption of neutral red (NR) dye from aqueous solutions via batch sorption experiments. Various factors influencing the sorption behavior (e.g., pH, sorbent dose, and dye concentration) were studied. The sorption data fitted well with Langmuir isotherm model. Batch kinetic experiments showed that the adsorption followed pseudosecond‐order kinetic model with correlation coefficients greater than 0.999. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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.     

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.     

Synthesis of clay-supported nanoscale zero-valent iron using green tea extract for the removal of phosphorus from aqueous solutions

This study addresses the synthesis of nanoscale zero-valent iron (nZVI) in the presence of natural bentonite (B-nZVI) using green tea extract.The natural bentonite and B-nZVI were then applied for the removal of phosphorus from aqueous solutions at various concentrations,pH levels and contact time.The desorption of phosphorus (P) from adsorbents was done immediately after sorption at the maximum initial concentration using the successive dilution method.The characterization of FTIR,SEM,and XRD indicated that nZVI was successfully loaded to the surface of natural bentonite.The sorption of phosphorus on B-nZVI was observed to be pH-dependent,with maximum phosphorus removal occurring at the pH range of 2 to 5.The results demonstrate that the maximum sorption capacities of natural bentonite and B-nZVI were 4.61 and 27.63 mg·g-1,respectively.Langmuir,Freundlich,and Redlich-Peterson models properly described the sorption isotherm data.For either adsorbent,desorption isotherms did not coincide with their corresponding sorption isotherms,suggesting the occurrence of irreversibility and hysteresis.The average percentages of retained phosphorus released from natural bentonite and B-nZVI were 80％ and 9％,respectively.The results indicated that sorption kinetics was best described by the pseudo-second-order model.The present study suggests that B-nZVI could be used as a suitable adsorbent for the removal of phosphorus from aqueous solutions.     

Modification and characterization of poly (ethylene terephthalate)‐grafted‐acrylic acid/acryl amide fiber for removal of lead from human plasma and environmental samples

A new fibrous adsorbent was prepared by grafting acrylic acid/acryl amide (AA/AAm) comonomers onto poly (ethylene terephthalate) (PET) fibers. The resulting sorbent has been characterized by Fourier transform infrared (FT‐IR), elemental analysis, thermogravimetric analysis (TGA), FT‐Raman, and scanning electron microscopy (SEM) and studied for the preconcentration and determination of trace Pb (II) ion from human biological fluid and environmental water samples. The optimum pH value for sorption of the metal ion was 8. The sorption capacity of functionalized resin is 44.1 mg g^?1. The chelating sorbent can be reused for 20 cycles of sorption–desorption without any significant change in sorption capacity. A recovery of 100.2% was obtained for the metal ion with 0.5M nitric acid as eluting agent. Effect of grafting yield, shaking time, shape of sorbent, and pH of the medium on adsorption of the metal ion were investigated. Scatchard analysis revealed that the homogeneous binding sites were formed in the polymers. The equilibrium adsorption data of Pb (II) on modified fiber were analyzed by Langmuir, Freundlich, Temkin, and Redlich‐Peterson models. Based on equilibrium adsorption data, the Langmuir, Freundlich, and Temkin constants were determined as 0.236, 10.544, and 9.497 at pH 8 and 20°C, respectively. The method was applied for lead ions determination from human plasma and sea water sample. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Iminodiacetic acid‐containing polymer brushes grafted onto silica gel for preconcentration and determination of copper(II) in environmental samples

Silica gel has been modified by silylation with 3‐mercaptopropyltrimethoxysilane followed by graft polymerization of dimethylacrylamide and (N,N‐bis‐carboxymethyl)amino‐3‐allylglycerol‐co‐dimethylacrylamide, synthesized via the reaction of allyl glycidyl ether with iminodiacetic acid. The sorbent, poly(AGE/IDA‐co‐DMAA)‐grafted silica gel, has been characterized by FTIR, elemental analysis, thermogravimetric analysis (TGA), FT‐Raman, and scanning electron microscopy and studied for the preconcentration and determination of trace amounts of Cu(II) ion in environmental water samples. The optimum pH value for quantitative sorption of Cu(II) in batch mode was 5.5 and desorption was achieved, using 0.5 mol L^?1 nitric acid. The sorption capacity of functionalized sorbent is 32.3 mg g^?1. The chelating sorbent was reused for 15 sorption–desorption cycles without any significant change in sorption capacity. The profile of copper uptake by the sorbent reflected good accessibility of the chelating sites in the poly(AGE/IDA‐co‐DMAA)‐grafted silica gel. Scatchard analysis demonstrated homogeneous nature of binding sites. The equilibrium adsorption data of Cu(II) on modified sorbent were analyzed by Langmuir, Freundlich, Temkin, and Redlich–Peterson models. Based on equilibrium adsorption data, the Langmuir, Freundlich, and Temkin constants were determined as 0.0665, 4.26, and 8.34, respectively, at pH 5.5 and 20°C. Adsorption isotherms were analyzed at different temperatures to obtain free energy, enthalpy, and entropy of adsorption. The method was applied for Cu(II) determination in sea water samples. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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

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

Modification and characterization of amberlite XAD-2 with calcein blue for preconcentration and determination of copper(II) from environmental samples by atomic absorption spectroscopy

A chelating resin is produced by coupling a dye calcein blue to Amberlite XAD-2 through an azo spacer. The resulting resin has been characterized by FT-IR, elemental analysis, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) studied for the preconcentration and determination of trace Cu(II) from solution samples. The optimum pH for adsorption of copper ions was 6. The sorption capacity of functionalized resin is 27 mg·g⁻¹. The chelating resin can be reused for 10 cycles without any significant changes in sorption capacity. A recovery of 100% was obtained for Cu(II) when eluted with 0.5 M nitric acid. Scatchard analysis revealed that homogeneous binding sites were formed in the resin. The equilibrium adsorption data of Cu(II) on modified resin were analyzed by Langmuir, Freundlich and Temkin models. Based on equilibrium adsorption data the Langmuir, Freundlich and Temkin constants were determined 0.036, 2.196 and 0.348 at pH 6 and 20 °C, respectively. The method was applied for Cu(II) assay in environmental samples.     

Sequential competitive sorption and desorption of chlorophenols in organoclay

Single- and bi-solute sorption and desorption of 2-chlorophenol (2-CP) and 2,4,5-trichlorophenol (2,4,5-TCP) in montmorillonite modified with hexadecyltrimethyl-ammonium (HDTMA) were investigated by sequential sorption and desorption. Effect of pH on the sequential sorption and desorption was investigated. As expected by the magnitude of octanol: water partition coefficient (K_ow), both sorption and desorption affinity of 2,4,5-TCP was higher than that of 2-CP at pH 4.85 and 9.15. For both chlorophenols, the protonated speciation (at pH 4.85) exhibited a higher affinity in both sorption and desorption than the predominant deprotonated speciation (about 80% and 99% of 2-chlorophenolate and 2,4,5-trichlophenolate anions at pH 9.15, respectively). Desorption of chlorinated phenols was strongly dependent on the current pH regardless of their speciation in the previous sorption stage. Freundlich model was used to analyze the single-solute sorption and desorption data. No appreciable desorption-resistant (or non-desorbing) fraction was observed in organoclays after several sequential desorptions. This indicates that sorption of phenols in organoclay mainly occurs via partitioning into the core of the pseudo-organic medium, thereby causing desorption nearly reversible. In bisolute competitive systems, sorption (or desorption) affinity of both chlorophenols was reduced compared to that in its single-solute system due to the competition between the solutes. The ideal adsorbed solution theory (IAST) coupled with the single-solute Freundlich model was positively correlated with the bisolute sequential competitive sorption and desorption equilibria.     

有机蒙脱土对单宁酸的吸附性能

利用十六烷基二甲基羟乙基溴化铵对钠基蒙脱土（MMT）进行离子交换改性,制得有机蒙脱土（OMMT）,并通过FT-IR、XRD对MMT改性前后的结构进行表征。通过静态吸附试验,探究OMMT对单宁酸（TA）的吸附条件和吸附机理。结果表明,OMMT吸附TA对pH值有较大的依赖性,吸附最佳pH值在4.0左右;吸附平衡时间为6h,吸附动力学曲线符合准二级动力学模型;吸附等温线用Langmuir方程比Freundlich方程能更好地描述;在pH值为4.0、TA初始浓度为500 mg/L、温度为20℃时,最大吸附容量为181.6mg/g;热力学参数ΔG、ΔH均为负值表明吸附为自发的放热过程。在饱和吸附和解吸重复7次后,再生OMMT吸附容量下降不到20%。     

Synthesis,characterization, and application of amberlite XAD‐2‐ salicylic acid‐ iminodiacetic acid for lead removal from human plasma and environmental samples

A new chelating resin is prepared by coup‐ling Amberlite XAD‐2 with salicylic acid (SAL) through an azo spacer. Then the polymer support was coupled with iminodiacetic acid (IDA). The resulting sorbent has been characterized by FT‐IR, elemental analysis, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) and studied for the preconcentration and determination of trace Pb (II) ion from human biological fluid and environmental water samples. The optimum pH value for sorption of the metal ion was 5. The sorption capacity of functionalized resin is 67 mg g⁻¹. The chelating sorbent can be reused for 20 cycles of sorption–desorption without any significant change in sorption capacity. A recovery of 95% was obtained for the metal ion with 0.5M nitric acid as eluting agent. The profile of lead uptake on this sorbent reflects good accessibility of the chelating sites in the Amberlite XAD‐2‐SAL/IDA. Scatchard analysis revealed that the homogeneous binding sites were formed in the polymers. The equilibrium adsorption data of Pb (II) on modified resin were analyzed by Langmuir, Freundlich, Temkin, and Redlich‐Peterson models. Based on equili‐brium adsorption data the Langmuir, Freundlich, and Temkin constants were determined 0.428, 20.99, and 7 × 10⁻¹² at pH 5 and 20°C. The method was successfully applied for determination of lead ions in human plasma and sea water sample. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Removal of Basic Blue 3 from aqueous solution by <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis> biomass: Biosorption and precipitation mechanisms

The waste biomass generated from mono sodium glutamate fermentation process, Corynebacterium glutamicum, was evaluated as a biosorbent for the removal of Basic Blue 3 (BB 3), as a model cationic dye, from aqueous solution. A series of batch experiments to study pH edge, precipitation of dye, isotherms and kinetics were undertaken. The solution pH was found to be an important factor in biosorption of BB 3. With increasing the pH, the uptake of BB 3 increased, except at a pH below 2. At pH values below 2, the precipitation of BB 3 occurred rather than biosorption, which resulted in overestimation of the sorption performance. The sorption process could reach quickly to equilibrium after 1 min. The Langmuir and Freundlich models were used to fit the experimental data at different pH conditions. Between them, the Langmuir model described the experimental data very well with high correlation coefficients. Furthermore, C. glutamicum was easily eluted by shifting the solution pH, making repeated sorption/desorption cycle (up to 4 times) possible without significant performance decrease.     

Sorption of Azo Dyes onto a Mexican Surfactant‐Modified Clinoptilolite‐Rich Tuff

Abstract

The selectivity of a Mexican surfactant‐modified clinoptilolite‐rich tuff to retain azo dyes (red‐40, yellow‐5 and a mixture of them) from aqueous solutions has been investigated. The zeolitic material was modified with hexadecyltrimethylammonium bromide and then left in contact with azo dyes. The uptake was determined at different contact times and concentrations of dyes solutions. First order Elovich, and pseudo second order models as well as the lineal, Langmuir, and Freundlich isotherms were used to describe the experimental data. It was found that in single and binary solutions, under the experimental conditions, the modified zeolitic material retain preferentially the dye red‐40 in comparison to yellow‐5. The best models to describe the reaction rate and the sorption of azo dyes red‐40 and yellow‐5 by Mexican surfactant modified clinoptilolite‐rich tuff were pseudo‐second order and Langmuir models, respectively. These results show that surfactant modified clinoptilolite‐rich tuff from Villa de Reyes (San Luis Potosi, Mexico) could be considered as a potential adsorbent of azo dyes from aqueous solutions.     

Kinetics and thermodynamic studies of Cr(VI) adsorption using environmental friendly multifunctional zeolites synthesized from coal fly ash under mild conditions

Abstract

The Na-P1 zeolite was produced from coal fly ash and modified with different environmental friendly surfactants. The potential of these green modified zeolites was investigated as adsorbents for Cr(VI) ions in a batch system. XRD, SEM, XRF, and ICP-AES analyses were used for the characterization of raw materials and zeolite samples. The environmental friendly modified zeolites successfully immobilized different toxic elements in their framework inhibiting the transfer of these toxic elements to the surrounding liquid phase. The effects of various operational parameters on Cr(VI) removal were studied. The Hexamethylenediamine (HDTMA) and Ammonyx KP (KP) modified zeolites had larger chromium removal potential than the other samples at all temperatures. The effectiveness of Cr(VI) ions elimination became greater as the pH decreased and the adsorbent dose increased. The Freundlich, Langmuir, and Dubinin–Radushkevich isotherms were fitted to the equilibrium data. The Dubinin–Radushkevich and Langmuir models gave a better fitness to equilibrium data of HDTMA-Na-P1 and KP-Na-P1, respectively. The positive and high ΔH° values showed the endothermic nature of the total Cr(VI) sorption procedure and indicated that Cr(VI) adsorption onto HDTMA-Na-P1 and KP-Na-P1 is a chemisorption. The negative ΔS° values also showed that chromium ions were stable on the surface of adsorbents. The adsorption potential of the developed eco-friendly KP-Na-P1 was higher than those of other adsorbents reported in the literature.     

Performance of acrylic monomer based terpolymer/montmorillonite nanocomposite hydrogels for U(VI) removal from aqueous solutions

Acrylic monomer based terpolymer/montmorillonite nanocomposite hydrogels (NH-MMTs) synthesized using 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA), 2-acrylamido-2-methlypropane sulfonic acid (AMPS) and 2-hydroxyethyl methacrylate (HEMA) in the aqueous montmorillonite (MMT) suspension were employed as adsorbents for U(VI) removal from aqueous solutions. Adsorption efficiency of the NH-MMTs was strongly enhanced by increasing pH in the range of 3–6. Adsorption capacity of the NHs increased with the MMT weight ratio up to 1% and the complete removal of U(VI) from 1 mmol/L aqueous solutions was achieved by 2 g/L polymer but further increase of MMT up to 6% caused a gradual decrease in adsorption percentage up to 57%. Nearly 98% of U(VI) loaded on the adsorbents could be recovered by 0.1 M HNO₃. Consecutive adsorption/desorption cycles showed that the NH-MMTs are re-usable. Kinetic results were analyzed using Paterson's and Nernst Planck approximation's based on homogeneous solid phase diffusion (HSPD). Experimental data were fitted to equilibrium isotherm models, Langmuir, Freundlich, Dubinin–Radushkevich and Temkin. SEM, and FTIR analysis of bare and U(VI) loaded adsorbents were used to elucidate adsorption mechanisms. The results showed that the NH-MMTs tested in this study are very promising for the recovery of U(VI) from water.     

Synergistic removal of Cu(II) and nitrazine yellow dye using an eco‐friendly chitosan‐montmorillonite hydrogel: Optimization by response surface methodology

A comprehensive feasibility study on adsorption of Cu(II) and a water‐soluble nitrazine yellow (NY) dye by chitosan‐montmorillonite (CS‐MMT) hydrogel as the biosorbent was investigated as a function of biosorbent dosage, initial concentration, pH, temperature, and the presence of salts. Box–Behnken methodology was applied to optimize the adsorption experiments. Maximum adsorption values were determined as 132.74 mg/g and 144.41 mg/g at pH = 5.0, for Cu(II) and NY dye, respectively. Equilibrium isotherms of Langmuir and Freundlich were analyzed by the non‐linear regression model. The equilibrium data were well described by Freundlich model and the adsorption process well fitted pseudo‐second order kinetics. The enthalpy change of adsorption (ΔH°) were calculated as ?3.78 kJ/mol and ?5.75 kJ/mol for Cu(II) and NY dye, respectively, indicating that the adsorption processes were exothermic. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43664.     

Preconcentration and determination of chromium in water with flame atomic absorption spectrometry by thiourea-formaldehyde as chelating resin

Thiourea-formaldehyde chelating resin is synthesized simply and rapidly from thiourea and formaldehyde by condensation polymerization and characterized by IR spectra and studied for the preconcentration and determination of trace Cr(III) ion from solution samples. The optimum pH value for sorption of the metal ion was 6.5. The sorption capacity of resin for Cr(III) was determined. The chelating resin can be reused for 20 cycles of sorption-desorption without any significant change in sorption capacity. A recovery of 96% was obtained for the metal ion with 0.5M HNO₃ as eluting agent. The equilibrium adsorption data of Cr(III) on modified resin were analyzed by Langmuir, Freundlich and Temkin models. Based on equilibrium adsorption data the Langmuir, Freundlich and Temkin constants were determined as 0.016, 0.040 and 0.074 at pH 6.5 and 20°C. The method was applied for chromium ion determination from river water sample.     

Removal of Metanil Yellow from its Aqueous Solution by Fly Ash and Activated Carbon Produced from Different Sources

Abstract

The present study has been undertaken to observe the relative efficiency of removal of metanil yellow from its aqueous solution by using different adsorbents like fly ash and activated carbon produced from different sources i.e. coconut shell, mehagani saw dust, and rice husk. It has also been observed that the rate of adsorption is highly dependent on contact time, adsorbent dose, pH, and initial concentration of the dyestuff. Rate of removal has been observed to increase with increasing contact time and adsorbent dose but with decreasing initial concentration. Higher removal has been observed generally in acidic range. Adsorptions by the adsorbents under investigation follow the Freundlich and Langmuir isotherm models where Freundlich and Langmuir constants have also been determined at different temperatures. Isotherms have been used to obtain the thermodynamic parameters like free energy, enthalpy and entropy of adsorption. Kinetic studies showed that all the adsorbents follow first order adsorption rate model with respect to the dye solution concentration. Various kinetic parameters such as first order adsorption rate constant, mass‐transfer co‐efficient, pore‐diffusion constant, and activation energy of adsorption were evaluated to establish the mechanism. Adsorption processes were found to be endothermic, spontaneous, and pore‐diffusion controlled for all the adsorbents. Among the adsorbents used in this study, activated carbon produced from mehagani saw dust has been found to be the most effective, which remove almost 100% metanil yellow from its 1000 ppm aqueous solution.     

Removal of Fluoride from Contaminated Drinking Water using Unmodified and Aluminium Hydroxide Impregnated Blue Lime Stone Waste

Abstract

The adsorption of fluoride on lime stone (LS) and aluminium hydroxide impregnated lime stone (AlLS) was investigated using a batch adsorption technique. A series of experiments were under taken in an agitated batch adsorber to assess the effect of the system variables such as solution pH, dye concentration and temperature. Removal of fluoride was observed to be the most effective at pH 8. The langmuir and Freundlich isotherm models were applied to the equilibrium data. The results showed that the Freundlich equation fits better than the Langmuir equation. The maximum sorption capacities for the LS and AlLS adsorbents were found to be 43.10 mg/g and AlLS 84.03 mg/g respectively. The FTIR studies indicate that the adsorption of fluoride is physiorption. The adsorption of fluoride onto AlLS proceeds according to a pseudo-first-order model. The results reveal that the LS and AlLS can be economical for the removal of fluoride compared to many other expensive adsorbents.     

Synthesis, characterization and application of allyl phenol modified amberlite XAD-4 resin for preconcentration and determination of copper in water samples

A new chelating resin was prepared by coupling Amberlite XAD-4 with phenol through an azo spacer, then modified by allyl bromide and characterized (by elemental analysis and IR) and studied for preconcentration of Cu(II) using flame atomic absorption spectrometry (FAAS) for metal monitoring. The optimum pH value for sorption of the above mentioned metal ion was 4.5. The resin was subjected to chemical evaluation through batch binding and column chromatography of Cu(II). The chelating resin can be reused for 15 cycles of sorption-desorption without any significant change in sorption capacity. A recovery of 98% was obtained for the metal ion with 0.5 M HNO₃ as eluting agent. The equilibrium adsorption data of Cu(II) on modified resin were analyzed by Langmuir, Freundlich and Temkin models. Based on equilibrium adsorption data the Langmuir, Freundlich and Temkin constants were determined to be 0.061, 0.193 and 0.045 at pH 4.5 and 25 °C. The method was applied for the copper determination from industrial waste water sample.