Maximum Adsorption Values Research Articles

Adsorption of heavy-metal ions from aqueous solution onto chitosan-modified polyethylene terephthalate (PET)

A novel chitosan-modified polyethylene terephthalate (PET) composite (CCP) adsorbent was specifically fabricated using a dip-padding method for removal of toxic metal ions (Zn2+, Cu2+, and Pb2+) from aqueous solution, especially during emergency treatment of river pollution. The fabricated CCP sample was investigated by scanning electron microscopy, static contact angle measurement, and X-ray photoelectron spectroscopy to confirm successful coating of chitosan onto PET fibers. Adsorption experiments demonstrated that the adsorption process of metal ions onto the surface of CCP was well fit by the Langmuir isotherm model and pseudo-second-order kinetic model. Maximum adsorption values (q max) of 18.69, 23.70, and 31.25 mg g−1 were obtained from the Langmuir isotherm model for Zn(II), Cu(II), and Pb(II), respectively.

Removal of Cd2+ ions from aqueous solution using cassava starch–based superabsorbent polymers

ABSTRACTA comprehensive feasibility study on the adsorption of Cd2+ ions by cassava starch–based superabsorbent polymers (CST‐SAPs) as the biosorbent was investigated as a function of adsorbent dosage, pH, initial concentration, contact time, and temperature. An orthogonal experiment and range analysis were applied to optimize the adsorption conditions. Adsorbent dosage and initial concentration were the most sensitive variables for adsorption capacity. The maximum adsorption value of Cd2+ ions was determined as 347.46 mg/g at pH 6.0, initial concentration of 200 mg/L, and contact temperature and time of 323 K and 6 h, respectively, with 0.1 g adsorbent dosage. The equilibrium data were well described by a Langmuir model, and the adsorption process was well fitted by pseudo‐second‐order kinetics. The Fourier transform infrared spectroscopy (FTIR) data confirmed that acrylic acid and acrylic amide grafted onto the cassava starch. The X‐ray diffraction and FTIR results for the Cd2+‐absorbed CST‐SAP (CST‐SAP‐Cd2+) samples showed that the CST‐SAP could effectively adsorb Cd2+ ions and that the characteristic groups were translocated by chelation. The scanning electron microscopy results for the CST‐SAP revealed that the surface of the polymer was rough, and the layered structure that was full of folds caused an enhanced specific surface; such conditions were beneficial to Cd2+ ion adsorption. It was concluded that the CST‐SAP was an excellent adsorbent for Cd2+ ion removal from aqueous solution. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44758.

Surface tension and adsorption of lithium in bismuth-based alloys

Temperature and concentration dependences of the surface tension of 11 alloys of the Bi–Li system in the interval of compositions with up to 10.46 at % Li content are determined for the first time. A shallow sloping minimum is observed on the surface tension isotherm in the region with small lithium additives in bismuth. Lithium adsorption with liquid bismuth is calculated with the obtained data. It is shown that the maximum value of lithium adsorption is obtained with compositions with 0.8 at % Li content, and the adsorption isotherm has its minimum value in alloys with about 4 at % Li content.

Competitive Adsorption and Subsequent Desorption of Sulfate in the Presence of Various Anions in Soils

In this experiment we investigated the influence of various anions including oxalic acid encountered as solution phase in soil on the adsorption and desorption of sulfate in Chungwon Bt soil. The effect of chloride and nitrate on the adsorption of sulfate was not significant, suggesting that sulfate was better able to compete for adsorption sites at concentrations studied, in contrast to the large reduction in the amount of chloride adsorbed in the presence of sulfate. The results of competition for sorption sites between sulfate and anion showed that the simultaneous presence of two anions in solution was effective in reduction of competing anion at a maximum value of adsorption, due to the similar adsorption mechanism for anion competition. Therefore, the variation in the buffer power of the acids will produce a change in the strength and amount of adsorption and the competitive ability.

Graphene oxide (GO)/polyacrylamide (PAM) composite hydrogels as efficient cationic dye adsorbents

Composite hydrogels were prepared in the mixtures of graphene oxide (GO) and polyacrylamide (PAM) in water. The gelation behavior of the hydrogels was studied in detail. The formation of GO/PAM composite hydrogels were induced by various kinds of noncovalent interactions between GO sheets and PAM, including hydrogen bonding, electrostatic interaction, hydrophobic interaction, van der Waals force, the π-π stacking of GO sheets, and etc. Microstructures determined by TEM and SEM demonstrated that GO/PAM hydrogels displayed three-dimensional network structures, and the network of the gels gradually changed regular with the increasing concentration of GO at a fixed concentration of PAM (cPAM), conversely, with the increase in PAM concentration at a fixed concentration of GO (cGO), the hole-structures of gels become irregular. Similarly, at the fixed molar ratio of GO to PAM of 1:1, with the increasing total concentration, the hole-structures of gels also become irregular. The cationic dye molecules, i.e., Methylene Blue (MB) and Rhodamine 6G were efficiently entrapped to the xerogels within 20 and 60min with the maximum adsorption value of 292.84 and 288mgg−1, respectively. The xerogels exhibited excellent adsorption efficiency and capability for the cationic dyes and were promising to act as toxic materials adsorbents. The adsorption kinetics of dye followed the pseudo-second order model and the dye adsorption isotherm follows both Langmuir and Freundlich adsorption isotherms model.

Comparisons of two chelating adsorbents prepared by different ways for chromium(VI) adsorption from aqueous solution

Poly(catechol-diethylenetriamine-p-phenylenediamine) (PCEA1) and Poly(catechol-diethylenetriamine-melamine) (PCEA2), two kinds of similar chelating adsorbents with analogous structures, were used for the comparative study on Cr(VI) removal from aqueous solution. Many methods were employed to characterize these adsorbents, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometer (EDS). Batch experiments were carried out to investigate the adsorption performance of Cr(VI), such as pH value, adsorbent dosage, initial concentration, contact time and temperature. Furthermore, adsorption isotherm, intra-particle diffusion, kinetics and thermodynamics were studied completely and systematically. XPS technique confirmed that the reduction from toxic Cr(VI) to nontoxic Cr(III) existed in the adsorption process. After that, the removal of Cr(VI) in simulative wastewater caused by both adsorbents was nicely fitted with the Langmuir isotherm model and pseudo-second-order kinetic model. The maximum adsorption values of the PCEA1 and PCEA2 were 200mg/g and 175.4mg/g, respectively. The intra-particle diffusion study further demonstrated that adsorption processes all had two portions. The negative ΔG and positive ΔH indicated that the adsorption was spontaneous and endothermic. Tests on Cr(VI) removal indicated the potential applicability of the two adsorbents with a similar adsorption mechanism.

Evaluation of phosphorus sorption characteristics of soils from the Bambouto sequence (West Cameroon)

The evaluation of phosphorus sorption characteristics of soils and their relation to soil properties from the Bambouto sequence of Baranka 1, Baranka 2, Femock 1 and Femock 2 has been studied. Phosphorus, an essential plant nutrient, is often not readily available to plants and this deficiency tends to limit plant growth. It is thus, necessary to investigate the quantity that is readily available to plants in order to avoid excesses and reduce water pollution by fertilizers. The Freundlich, Langmuir, Temkin, Van Huay and Linear adsorption isotherms were used to describe the P adsorption processes. Phosphorus adsorption capacity decreased in the order Femock 2 > Femock 1 > Baranka 2 > Baranka 1 with maximum adsorption values of 3464.21, 3112.17, 2866.00 and 2758.38 mg kg-1 respectively. Accuracy of fitness of data of the four soil series into the adsorption equations increased in the order Langmuir, Linear, Van Huay, Temkin and Freundlich isotherm. The capacity of each soil sample to adsorb phosphorus was significantly correlated with the clay content (r = 0.949*) of the soils. The use of organic materials and liming as a basis for phosphorus sorption reduction will be useful for crop production in the Bambouto sequence.© 2016 International Formulae Group. All rights reserved.Keywords: Phosphorus fixation, volcanic soil, free aluminium, clay, soil pH

Sorption of plutonium to bacteria and fungi isolated from groundwater and clay samples

Preliminary studies of Pu(V) sorption to site-specific microorganisms isolated from the Triassic clay selected as an engineered barrier for the near surface low and intermediate level radioactive waste repository and from groundwater at the expected site were carried out. Adsorption of Pu(V) by bacteria attained the maxima values of 82–84 % at pH 6–7. The maximum adsorption values of Pu of about 100 % were found for Penicillium chrysogenum at pH 4.1. Bioreduction of Pu(V) to Pu(IV) by Bacillus cereus was observed, while any Pu(III) was not found in the system.

Adsorption of polyhydroxy fullerene on polyethylenimine-modified montmorillonite

The environmental behaviors and potential ecotoxicity of carbon nanomaterials, such as fullerene and its derivatives, are gaining ever-increasing concerns at present. This work attempts to develop an adsorbent for the effective removal of polyhydroxy fullerene (PHF) from aqueous solution, which was synthesized by modifying montmorillonite (Mt) with a branched polymer polyethylenimine (PEI). The adsorption results showed that the obtained adsorbent (i.e., PEI-Mt) could effectively remove PHF over a wide range of solution pH; both the electrostatic attraction and hydrogen-bond interaction between PHF and PEI-Mt contributed to the strong adsorption. Decreasing solution pH and rising PEI loading amount on Mt could both increase the adsorption amounts of PHF on PEI-Mt. The adsorption isotherms could be well fitted with the Langmuir model, and the calculated maximum adsorption value of PHF on 10%PEI-Mt reached ~213mg/g, much higher than that on the original Mt (~16mg/g). The adsorbents after PHF adsorption were further characterized using Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. The results suggested that the adsorbed PHF primarily existed on the outer surfaces of PEI-Mt. This work showed that PEI-Mt can be a potentially efficient adsorbent for the removal of PHF from aqueous solution.

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

ABSTRACTA 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.

Adsorption properties of Ni, Cu, and Zn in young alkaline lake sediments in south Hungary (Lake Fehér, Szeged)

Halmos L., Bozso G., Pal-Molnar E. (2015): Adsorption properties of Ni, Cu, and Zn in young alkaline lake sediments in south Hungary (Lake Feher, Szeged). Soil & Water Res., 10: 244–251. Adsorption properties of Cu, Ni, and Zn in alkaline sediments of Lake Feher at Szeged (Hungary) were inves tigated. The effects of pollution of these three chosen phytotoxic elements in sodic sediments were primarily examined. These elements are strongly adsorbed in the soils and sediments with relatively high pH values for a long time without any influence on the geochemical processes. However, the salinization (indicated by the global climate change) of soils and sediments can strongly change the original geochemical status. For the adsorption experiments, the horizons with the highest organic matter contents were selected from two profiles. The pH, electrical conductivity (EC), particle size distribution, carbonate content, quality and quantity of organic matter, and clay mineral content of the selected samples were also determined. Efficiency of the adsorption is reduced in Cu >> Zn > Ni and Cu > Ni >> Zn order based on the calculated maximum and specific adsorption values. The adsorption properties of heavy metals are dependent on the content of soil constituents. The results showed that Cu has the highest but not the same affinity to each of the sorbent materials. Ni is strongly while Zn is less bounded to the organic matter. In most cases the results showed that the most effective fixative soil constituent is carbonate, followed by clay minerals and, last, organic matter regarding to the investigated elements.

Phosphorus Adsorption of Some Brazilian Soils in Relations to Selected Soil Properties

A major nutritional problem to crops grown in highly weathered Brazilian soils is phosphorus (P) deficiencies linked to their low availability and the capacity of the soils to fix P in insoluble forms. Our studies examined factors that might influence P behavior in soils of the Amazon region. This study was conducted to evaluate the maximum phosphate adsorption capacity (MPAC) of the soils developed from mafic rocks (diabase), their parent materials and other factors resulting in the formation of eutrophic soils having A chernozemic horizon associated with Red Nitosols (Alfisol) and Red Latosols (Oxisol) of the Amazonian environment. The MPAC was determined in triplicates as a function of the remnant P values. The different concentrations used to determine the MPAC allowed maximum adsorption values to be reached for all soils. The Latosol (Oxisol) and Nitosol (Alfisol) soils presented higher phosphate adsorption values that were attributed to the oxidic mineralogy and high clay texture while the Chernosol (Mollisol) soils presented the lowest phosphate adsorption values.

Treatment of Cr(VI) in aqueous solution by Ni–Al and Co–Al layered double hydroxides: Equilibrium and kinetic studies

Ni–Al layered double hydroxide (Ni–Al LDH) and Co–Al LDH were prepared using a coprecipitation method. Ni–Al LDH and Co–Al LDH were found to remove Cr(VI) from aqueous solution through anion exchange of Cr2O72− with Cl− intercalated in the interlayer of the LDHs. Ni–Al LDH and Co–Al LDH were both found to be superior to Mg–Al LDH for removal of Cr(VI). This excellent behavior is attributed to the buffering effect of Ni–Al LDH and Co–Al LDH that results in a lower amount of OH− in solution and allows Cr2O72− to be more easily intercalated in the LDH interlayer. The Cr(VI) removal process was consistent with a Langmuir-type adsorption, indicating that the removal of Cr(VI) proceeded via chemical adsorption involving the anion exchange of Cr2O72− with intercalated Cl−. The maximum adsorption and equilibrium adsorption constant values were 2.0mmolg−1 and 2.4, respectively, for Ni–Al LDH, and 1.9mmolg−1 and 1.5, respectively, for Co–Al LDH. The kinetics of Cr(VI) removal by Ni–Al LDH and Co–Al LDH were consistent with a pseudo-second-order reaction, and the rate-determining step for Cr(VI) removal was found to be the anion exchange. The apparent rate constants at 10, 30, and 60°C for Ni–Al LDH were 2.2×10−3, 2.4×10−3, and 3.2×10−3gmmol−1min−1, respectively. The apparent rate constants at 10, 30, and 60°C for Co–Al LDH were 1.2×10−3, 1.6×10−3, and 1.9×10−3gmmol−1min−1, respectively. The Arrhenius plot of the rate constants yielded apparent activation energies of 6.1 and 6.6kJmol−1 for Ni–Al LDH and Co–Al LDH, respectively.

Kinetics and thermodynamics studies of pentachlorophenol adsorption on covalently functionalized Fe3O4@SiO2–MWCNTs core–shell magnetic microspheres

Abstract A novel core–shell covalently functionalized Fe 3 O 4 coated SiO 2 decorated multi-walled carbon nanotubes (Fe 3 O 4 @SiO 2 –MWCNTs) adsorbent was synthesized and characterized by scanning electron microscopy, transmission electron microscopy, Fourier Transform Infrared Spectrum (FTIR), Thermogravimetry, X-ray diffraction and magnetic measurements. The pentachlorophenol (PCP) adsorption effect factors of initial concentration, contact time, solution pH and temperature were investigated in detail. It was found the absorption capacity was strongly depended on pH, and the maximum adsorption value for PCP (96.4 mg/g) was obtained at pH 2.5. The equilibrium was attained within 30 min, and the adsorption kinetics was better described by pseudo-second-order kinetic model. The data pointed out excellent fit to Freundlich isotherm model. Thermodynamic parameters such as standard enthalpy (Δ H θ ), standard entropy (Δ S θ ) and standard free energy (Δ G θ ) showed that the adsorption of PCP onto Fe 3 O 4 @SiO 2 –MWCNTs was spontaneous, endothermic and random within the temperature range of 288–318 K. The results indicate that the Fe 3 O 4 @SiO 2 –MWCNTs adsorbent is a potential low-cost effective material for PCP removal from contaminated wastewater.

Peculiarities of the Adsorption of Heavy-Metal Ions from Aqueous Media by Modified Cellulose

Chemical modification of cotton cellulose with the formation of hydroxamic and aldehyde-bisulphite derivatives has been carried out. Sorption properties of initial and modified sorbents are investigated. It is established that a-hydroxycarboxyl groups, which are present in all three kinds of sorbents, form colourless chelate complexes due to the replacement of their protons with an equivalent amount of metal ions. Because of the charge transfer during metal-ligand interactions, coloured chelate complexes are formed. In the aldehyde-bisulphite groups, two singly charged ions (Na+ and H+) are consequently replaced with two equivalents of metal ion resulting in the formation of colourless chelate complexes. Sorption isotherms of metal ions by the samples of native and modified cellulose are well described by the Langmuir model. The maximum adsorption values and Henry's constants are in good agreement with the quantity and nature of cellulose acidic groups.

New Polysiloxane Surfaces Modified with <i>ortho-, meta-</i> or <i>para</i>-Nitrophenyl Receptors for Copper Adsorption

Porous SiO2 has been chemically modified with functional ortho-, meta- or para-nitrophenyl moieties using the heterogeneous route. This synthetic route involved the reaction of carbaldehyde derivatives with 3-aminopropyl trimethoxysilane prior to immobilization on the support. The new modified surfaces have been characterized by elemental analysis, FT-IR, 13C NMR of the solid state, nitrogen adsorption-desorption isotherm, BET surface area, B.J.H. Pore sizes, thermogravimetry curves (TGA) and scanning electron microscope (SEM). The new materials exhibit good chemical and thermal stability. These products were employed as a Cu(II) adsorbent from aqueous solutions at room temperature using the batch technique. Flame atomic absorption spectrometry was used to determine the Cu(II) concentration in the filtrate after the adsorption process. The results indicate that under the optimum conditions, the maximum adsorption value for Cu(II) was 20.0 mg Cu(II) g-1 modified silica, whereas the adsorption capacity of the unmodified silica was only 1.0 mg Cu(II) g-1 silica. On the basis of these results, it can be concluded that it is possible to modify chemically SiO2 with functional groups and use it as adsorbents for metals in aqueous media.

New Amine-Modified Silicas: Synthesis, Characterization and Its Use in the Cu(II)-Removal from Aqueous Solutions

Porous silica has been chemically modified with conjugated phenylamine and phenyldiamine moieties using the homogeneous route. This synthetic route involved the reaction of carbaldehyde derivatives with 3-aminopropyltrimethoxysilane prior to immobilization on the support. The resulting materials have been characterized by elemental analysis, FT-IR, 13 C NMR of the solid state, nitrogen adsorption-desorption isotherm, BET surface area, B.J.H. Pore sizes, thermogravimetry analyser (TGA) curves, X-ray diffraction (XRD) and scanning electron microscope (SEM). The new chelating surfaces exhibit good chemical and thermal stability. The solids were employed as Cu(II) adsorbents from aqueous solutions at room temperature. The effects of pH and adsorption kinetics have been studied using the batch technique. Flame atomic absorption spectrometry was used to determine the Cu(II) concentration in the filtrate after the adsorption process. The results indicate that under the optimum conditions, the maximum adsorption value for Cu(II) was 24.5 mg Cu(II) g −1 modified silica, whereas the adsorption capacity of the unmodified silica was only 1 mg Cu(II) g −1 silica. On the basis of these results, it can be concluded that it is possible to modify chemically silica with amine derivatives and to use the resulting modified porous silica as an effective adsorbent for Cu(II) in aqueous media.

Comparison Study on Adsorption and Removal of Antimony from Acidic Aqueous Solution by Activated Carbons and Machine-Made Charcoal

Adsorption effects of three kinds of activated carbons and a type of machine-made charcoal on the removal of antimony from acidic aqueous solution were investigated and compared. With an initial antimony solution concentration of 1000 μgL-1, the antimony adsorption by selected adsorbents were found to descend in the following order: machine-made charcoal (52.4%) > coconut activated carbon (42.6%) > coal based activated carbon (31.1%) > apricot stone based activated carbon (24.6%). The machine-made charcoal has the best adsorption capacity with a maximum adsorption values of 523.76 μgL-1. Five kinetic models were used for the fitting of the process of antimony adsorption, including Elovich, parabola diffusion, second order, first order and double-constant. Results showed that parabola diffusion and double-constant rate equation were the most suitable models in describing the relationship of antimony adsorption with time in acidic aqueous solution, implying that the adsorption kinetics of the antimony by the selected adsorbents in water might be a surface diffusion. Three adsorptive capacity indicators (iodine number, methylene blue number and phenol number) were determined in this paper. However, machine-made charcoal, which has a relatively high adsorption capacity, is of the lowest levels of the adsorptive capacity indicators. Thus, some complex mechanisms might be involved for the antimony adsorption by the machine-made charcoal, consequently considering the mechanism for the adsorption of antimony by the charcoal has not been verified, a further study still needs to be done.

Optimization of ultrasonic synthesis of N-succinyl-chitosan and adsorption of Zn2+ from aqueous solutions

N-succinyl-chitosan (N-NSC) was prepared by reacting chitosan (CS) with succinic anhydride (SA) under an ultrasonic radiation. The influences of three parameters (ultrasonic radiation power, mass ratio of SA to CS, and ultrasonic radiation time) on the degree of substitution (DS) of N-NSC were discussed and optimized with a response surface modeling. The optimum values of the above parameters for maximum value of DS were 118 W, 1.8:1, and 108 min, respectively. The adsorption performance of N-NSC for removing Zn2+ from aqueous solution was investigated in a batch system. Kinetic experiments data of that adsorption of Zn2+ onto N-NSC were fitted by pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models and the equilibrium isotherm data were described by six different isotherm equations. The adsorption follows pseudo-second-order kinetic model. The results demonstrate that the Langmuir equation is the best-fit model to describe the adsorption process with a maximum monolayer adsorption value of 135.41 mg/g, and Sips equation to predicit experimental value at an initial concentration of 100–700 mg/L, pH 5.0, and temperature 298 K.

The Characterization and Application of Polycarboxylate as a Superplasticizer in Concrete

Polycarboxylate was synthesized and the structure of the superplasticizer was characterized by FTIR. The water reducing effect of the synthesized copolymers was studied in terms of stirring time, the surface tension of superplasticizer and the adsorption on cement particles of superplasticizier. For all the samples tested in this research, increase in stirring time caused an increase in fluidity. The surface tension of the product solution (1wt%, w/w) is 51.2536 mN/m and the maximum value of adsorption was at about 2.6 mg/g at the concentration of 6wt%.