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In the present article, adsorption experiments of phosphate ions from their aqueous solutions were conducted with the use of five different materials (zeolite, bentonite, goethite, and systems I and II). The adsorption of phosphate ions were examined after mixing 2 g of each of these materials with 10 different phosphate concentrations (1.6, 3.2, 4.8, 6.5, 32.3, 193.5, 322.6, 483.9, 645.2, and 871.0 μmol L−1). The experimental equilibrium adsorption data were analyzed using the Langmuir, Freundlich, and Temkin equations. Results indicate the following order to fit the isotherms equations: Freundlich > Temkin > Langmuir. Moreover, the five materials were used as soil amendments to soils that were cultivated with wheat, maize, and cotton. Forty days after germination, the plants were collected, the morphological characteristics were identified, and the available phosphorus in soil and the total phosphorus in plants were determined. Comparing the experimental results, goethite and system I present the best impact in the root length, leaf area index, and dry weight of each plant. The adsorbed amount of phosphorus per g of dry weight of plants increases as follows: bentonite < system I < zeolite < system II < goethite (for wheat), goethite < system II < zeolite < bentonite < system I (for cotton), and system I < system II < bentonite < zeolite < goethite (for maize). Maize can be cultivated to soils contaminated with phosphorus with the simultaneous use of system I or II as soil amendments. Wheat can be used as phytoaccumulator crop for the phytoremediation of soils contaminated with phosphorus. [ABSTRACT FROM AUTHOR]

The ability of iron oxides (goethite) and natural zeolite (clinoptilolite) to adsorb copper from its aqueous solutions was extensively studied in the past. In this paper, the production of modified zeolites (systems I and II) from raw materials of zeolite and goethite was investigated compared to the initial materials. These two systems presented higher adsorption than goethite or clinoptilolite. Comparing the two systems, system II presented higher adsorption than system I. Isotherm studies showed that the adsorption data from all materials were best described by Freundlich isotherm. According to thermodynamic study, the values of ΔG° became more negative with the increase of temperature, indicating that the adsorption process was more favorable to higher temperature. The positive values of ΔH° indicated endothermic nature of adsorption. The use of all adsorptive materials as soil improvements was also investigated. Goethite, zeolite, and systems I and II were mixed separately with three different soils (clay loam, sandy loam, and loamy sand). Lettuces were cultivated, and the combination of system II with the loamy sand soil led to the best morphological characteristics of lettuces with the minimum adsorption of copper. Consequently, modified zeolites could be considered as two satisfactory detergents of highly copper concentration in soil and water. [ABSTRACT FROM AUTHOR]

Zeolite, hematite, modified zeolite and commercial activated charcoal were examined for their ability to remove methylene blue (MB) and methyl red (MR) from their aqueous solutions. Modified zeolite and hematite were produced according to the Schwertmann and Cornell method while zeolite and commercial activated charcoal were obtained from S&B and Fluka AG companies, respectively. Adsorption experiments were conducted at three different adsorbent-to-solution ratios, namely 8, 16 and 24 g/L under environmental conditions and continuous stirring. Equilibrium isotherms of MB and MR were studied at different initial concentrations (from 5 × 10-4 to 5 × 10-3 g/L). MB adsorption kinetics were also studied. The maximum adsorption of MB and MR from their aqueous solutions was achieved at 24 g/L (adsorbent-to-dye solution ratio) after 1 h and was equal to 100% (MB) on modified zeolite and 99% (MR) on commercial activated charcoal, respectively. All the other materials achieved intermediate values of dye adsorption. From the applied kinetic models, the pseudo-second-order equation best described the adsorption of MB and MR. Consequently, modified zeolite showed the highest adsorption capacity for MB, while commercial activated charcoal showed the highest adsorption capacity of MR. The studied adsorbents can be used as filters to remove dyes from wastewaters. [ABSTRACT FROM AUTHOR]

The present paper examines the phosphate adsorption from aqueous solutions onto goethite, bentonite, and bentonite-goethite system. The properties of the materials were studied by X-ray diffraction (XRD), attenuated total reflectance (ATR), and NMR spectra and by the measurement of the specific surface area, the point of zero charge (p.z.c.) and the pore-specific volume. ATR and NMR spectra of bentonite and bentonite-goethite system show peaks which correspond to tetrahedrally and octahedrally coordinated Al. The specific surface area of the system differs according to the appropriate method used, while system's p.z.c. is higher than bentonite and lower than goethite. The pore-specific volume of bentonite-goethite system is higher than that of bentonite or goethite. According to XRD spectrum of bentonite-goethite system, goethite coats the (001) spacing of bentonite while the coating of (010) plane of bentonite is limited. The crystallinity of the system decreases and the negative permanent charge increases. Phosphate adsorption experiments took place at different pH (3.8-9.0) and concentrations (40.3-443.5 μmol L) and constant capacitance model was applied to describe adsorption. A ligand exchange mechanism characterizes the model because the charge is divided among adsorbate and adsorbent. The constant capacitance model describes the adsorption mechanism in all examined pH. This model can be utilized in such systems using the surface protonation-dissociation constant of goethite and showing the exact shape of the adsorption isotherms for different pH values. Τhe produced low-cost bentonite-goethite system presents the highest adsorption of P per kilogram of goethite. [ABSTRACT FROM AUTHOR]

Abstract: Carbonaceous adsorbents based on novolac resin (N) and olive stone biomass (B) in a proportion of 20/80 and 40/60w./w. N/O were produced. The specimens were cured (c) and pyrolyzed/carbonized (C) up to 1000°C under a continuous countercurrent flow type pyrolysis operation (N20B-cC, N40B-cC). Commercial activated carbon (AC) was used for comparison reasons. Methylene blue adsorption from its aqueous solutions onto the adsorbents and kinetic analysis were investigated. The specific surface area of adsorbents and the gross calorific values (GCV) of cured materials were determined. The results show that N40B-cC presents lower weight loss and shrinkage but higher methylene blue adsorption than N20B-cC. Pseudo-second order mechanism describes better methylene blue adsorption onto all adsorbents. The specific surface area of carbonaceous and the gross calorific values of cured materials follow the order: AC>N20B-cC>N40B-cC and N100-c>N40B-c>N20B-c>B respectively. Olive stone biomass may constitute a suitable precursor for the production of carbonaceous materials. [Copyright &y& Elsevier]

In this research, a new porous organic polymer based on triazine and cyclohexanone rings was synthesized via Schiff base condensation, and its performance as an adsorbent for the removal of Methyl Red dye from aqueous solution was investigated. The synthesized polymer was characterized by FT-IR, XRD, SEM, EDS, TEM, TGA, and BET analyses. Five important parameters of pH (4–10), contact time (10–120 min), adsorbent dose (5–10 mg), initial dye concentration (10–70 mg/L), and temperature (25–45 °C) were investigated to optimize the adsorption conditions. Solution pH of 4, contact time of 80 min, adsorbent dose of 8 mg, initial dye concentration of 50 mg/L, and temperature of 45 °C were obtained as the best conditions for the adsorption of methyl red dye. Two widely used Langmuir and Freundlich models were employed to investigate the adsorption isotherm, and the obtained data showed that the adsorption process follows the Langmuir isotherm with a correlation coefficient (R2 = 0.9784) which indicates monolayer adsorption. The achieved maximum adsorption capacity was 178.57 mg/g. Also, the results of kinetic studies indicate that the adsorption process follows the pseudo-second-order kinetic, which suggests that chemical interactions play an important role in dye removal. Furthermore, the results showed that the adsorption process of methyl red dye by polymer is endothermic. [ABSTRACT FROM AUTHOR]

In this study, the removal of acid violet 7 (AV7) and basic violet 10 (BV10) synthetic dyes was investigated using fly ash alone, ultrasound (40 kHz) alone, and combined ultrasound/fly ash with various experimental parameters such as fly ash dose, contact time, and initial concentration of dye. The adsorption capacity of the ultrasound/fly ash process increased from 5.10 to 7.43 mg g-1 for AV7, and increased from 5.16 to 7.51 mg g-1 for BV10 compared with using fly ash alone. The sono-assisted adsorption process was successful in improving the dye uptake capacity with cavitation bubbles and acoustic waves, and thus AV7 and BV10 were removed with a shorter contact time and lower fly ash dose. Obtained regeneration and reuse experiment results showed that the fly ash could be reused for four consecutive cycles of the sono-assisted adsorption process, while fly ash could be reused for two consecutive cycles of the adsorption process. The adsorption kinetics for AV7 and BV10 onto fly ash fitted Lagergren's first-order adsorption kinetic model well. The Langmuir isotherm best described the adsorption with fly ash alone and ultrasound/fly ash process for AV7 and BV10. [ABSTRACT FROM AUTHOR]

Poly(acrylamide)-rice husk biochar [p(AAm)-RHB] hydrogel composites (HBC-RH) were used to eliminate phenols. The characterization of prepared composite was investigated by using SEM, TEM, TGA DSC, and FTIR. Based on our findings, the highest removal of phenol and p-nitrophenol (PNP) was found as 82.2% and 84.6% in 50 mg/L solution at pH = 7, respectively. The results revealed that the kinetic data were best fitted by pseudo-first-order for phenol and pseudo-second-order for PNP. To be concluded that the Temkin model perfectly described the removal of phenol and HBC-RH can be widely applied for various containments. [ABSTRACT FROM AUTHOR]

Two treatments, sodium hydroxide and hydrogen peroxide, were applied to enhance the capacity of fir tree(Abies alba)sawdust to adsorb Cd(II). Fourier transform infrared spectroscopy (FTIR) analysis and atomic force microscopy (AFM) were used to characterize untreated and treated fir tree sawdust. The removal of Cd(II) ions by treated sawdust was dependent on the initial Cd(II) concentration, initial pH, and temperature. Kinetics (pseudo-first-, pseudo-second-order, intra-particle, and film diffusion models) and isotherm models (Langmuir and Freundlich) of the considered biosorption process were examined. The pseudo-second-order model was found to better model the kinetics of Cd(II) adsorption. Maximum adsorption capacities calculated using the Langmuir model are 8.84 and 2.67 mg/g for NaOH and H2O2treated sawdust, respectively, and 2.20 mg/g for untreated sawdust. The results indicate that the two treatments enhanced the adsorption capacity of the studied sawdust. [ABSTRACT FROM PUBLISHER]

ABSTRACT The electropolymerization of 4-phenoxybenzoic acid (4-PBA) onto carbon fibers (CFs) was studied as a way to synthesize coated CFs with grafted poly(para-phenyl ether ketone) (p-PEK) and enhance their wettability by matrices such as PEK or PEEK. Since the pristine CFs were not electrochemically active enough, a proper electrochemical oxidation treatment using sulfuric acid was applied, capable of creating oxygen-containing groups onto their surface. The groups formed in the oxidized CFs were electron acceptors and their amount was quasi-quantitatively evaluated based on their ability to absorb dye from aqueous solutions. The graft electropolymerization of 4-PBA onto the CFs electrode was achieved at anodic potentials using cyclic voltammetry (CV). The grafted coating had a thickness of up to 0.35 μm. The materials were characterized using FTIR, NMR, SEM, and TGA. A possible reaction mechanism is proposed, for the grafting of 4-PBA units onto the carboxyl groups of the treated CFs. The coated CFs were more thermally stable compared to the treated CFs without grafting. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1466-1478, 2013 [ABSTRACT FROM AUTHOR]

The aim of the present research is to develop economic, fast, and versatile method for the removal of toxic organic pollutant phenol from wastewater using eggshell. The batch experiments are conducted to evaluate the effect of pH, phenol concentration, dosage of adsorbent, and contact time on the removal of phenol. The paper includes in-depth kinetic studies of the ongoing adsorption process. Attempts have also been made to verify Langmuir and Freundlich adsorption isotherms. The morphology and characteristics of eggshell have also been studied using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray fluorescence analysis. At ambient temperature, the maximum adsorption of phenol onto eggshells has been achieved at pH 9 and the contact time, 90 min. The experimental data give best-fitted straight lines for pseudo-first-order as well as pseudo-second-order kinetic models. Furthermore, the adsorption process verifies Freundlich and Langmuir adsorption isotherms, and on the basis of mathematical expressions of these models, various necessary adsorption constants have been calculated. Using adsorption data, various thermodynamic parameters like change in enthalpy (∆ H), change in entropy (∆ S), and change in free energy ∆ G have also been evaluated. Results clearly reveal that the solid waste material eggshell acts as an effective adsorbent for the removal of phenol from aqueous solutions. [ABSTRACT FROM AUTHOR]

Periodic mesoporous titanium phosphonate (PMTP-1) materials were synthesized and used as an adsorbent for the removal of a cationic dye, methylene blue (MB), from aqueous solutions. The PMTP-1 powder has a uniform mesopore size of 2.9 nm with high surface area of 606 m2/g. The batchdye adsorption experiments were performed under various conditions including contact time, adsorbent dose, initial MB concentration, solution pH and temperature. The adsorption equilibrium was achieved after 30 minutes of contact time, and the adsorption of MB on PMTP-1 was best fitted to the Langmuir isotherm model with the maximum monolayer adsorption capacity of 617.28 mg/g. Thermodynamic parameters such as ΔG, ΔH and ΔS were calculated. Results of kinetic studies indicated that the adsorption process followed the pseudo-second-order model, which suggests that the process might be a chemisorption. The study results indicate that the PMTP-1 powder could be used as an efficient adsorbent for the removal of textile dyes from effluents. [ABSTRACT FROM AUTHOR]

A number of industries currently produce varying organic pollutant-laden waste streams, which is a serious environmental prblem owing to their potential human toxicity. Amongst all the treatments proposed, adsorption is one of the more popular methods for the removal of pollutants from wastewater. In particular, considerable work has been carried out on the use of natural materials, nonconventional adsorbents, and their modifications. These natural materials and nonconventional materials in many instances are relatively cheap, abundant in supply, or thrown away as waste and have significant potential for modification that ultimately leads to enhancement of their adsorption capabilities. The authors review and evaluate literature dedicated to the preparation of adsorbents such as activated carbon and clays and their modifications/activation by recycling different types of waste materials and also to their application in organic pollutant containing aqueous-phase treatments. It should be noted that the reported adsorption capacities of the adsorbents vary, depending on the characteristics of the individual adsorbent, the extent of chemical modifications, the concentration of solutes, and the ionic strength and pH of the medium. Thus characterization of the adsorbents for their functional groups and their nature using IR, XRD, and pHZpchas been discussed. The authors further discuss how several key factors such as pH, competitive adsorption, and temperature influence the adsorption taking instances from literature. The authors also provide a summary of recent information obtained using batch studies and deals with the various adsorption mechanisms involved. [ABSTRACT FROM AUTHOR]