Free Energy Of Sorption Research Articles

Adsorption and detoxification of glyphosate and aminomethylphosphonic acid by montmorillonite clays.

The co-occurrence of mixtures of glyphosate (GLP) and aminomethylphosphonic acid (AMPA) in contaminated water, soil, sediment, and plants is a cause for concern due to potential threats to the ecosystem and human health. Major routes of exposure include contact with contaminated water and soil and through consumption of crops containing GLP and AMPA residues. Calcium montmorillonite (CM) and acid-processed montmorillonite (APM) clays were investigated for their ability to tightly sorb and detoxify GLP and AMPA mixtures. In vitro adsorption and desorption isotherms and thermodynamic analysis indicated saturable Langmuir binding of both chemicals with high capacities, affinities, enthalpies, and free energies of sorption and low desorption rates. In silico computational modeling indicated that both GLP and AMPA can be readily absorbed onto clay surfaces through electrostatic interactions and hydrogen bonding. The safety and efficacy of the clays were confirmed using well-established living organisms, including an aquatic cnidarian (Hydra vulgaris), a soil nematode (Caenorhabditis elegans), and a floating plant (Lemna minor). Low levels of clay inclusion (0.05% and 0.2%) in the culture medium resulted in increased growth and protection against chemical mixtures based on multiple endpoints. Results indicated that montmorillonite clays may be used to bind mixtures of GLP and AMPA in water, soil, and plants.

Dipicolinamide functionalized titania for highly efficient sorption of tetra and hexavalent actinide

Dipicolinamide functionalized titania particles have been synthesized for efficient decontamination of uranyl and thorium ions from aqueous acidic waste solution. Langmuir isotherm was found to be predominating with maximum sorption capacity of 125 mg/g for Th and 111 mg/g for U, respectively. The sorption was found to follow pseudo 2nd order kinetics predominately, with rate constant 8.6E−04 mg g−1 min−1 for Th and 6.1E−04 mg g−1 min−1 for U, respectively. Up to 200 kGy of gamma irradiation, not much deterioration in extraction performance of sorbent material was observed. Three contacts of 0.1 M aqueous solutions of oxalic acid and sodium carbonate were found to be effective in quantitative elution of Th4+ and UO22+ from the loaded sorbent, respectively. The sorption of U and Th on dipicolinamide functionalized titania was evidenced by SEM images, elemental mapping and the EDX. Theoretical investigation revealed that, the solution phase free energy of sorption (ΔGsol) was higher for Th4+ (−114.1 kcal mol−1) compared to UO22+ (−80.41 kcal mol−1).

Uranium (VI) Adsorbate Structures on Portlandite [Ca(OH)2] Type Surfaces Determined by Computational Modelling and X-ray Absorption Spectroscopy

Portlandite [Ca(OH)2] is a potentially dominant solid phase in the high pH fluids expected within the cementitious engineered barriers of Geological Disposal Facilities (GDF). This study combined X-ray Absorption Spectroscopy with computational modelling in order to provide atomic-scale data which improves our understanding of how a critically important radionuclide (U) will be adsorbed onto this phase under conditions relevant to a GDF environment. Such data are fundamental for predicting radionuclide mass transfer. Surface coordination chemistry and speciation of uranium with portlandite [Ca(OH)2] under alkaline groundwater conditions (ca. pH 12) were determined by both in situ and ex situ grazing incidence extended X-ray absorption fine structure analysis (EXAFS) and by computational modelling at the atomic level. Free energies of sorption of aqueous uranyl hydroxides, [UO2(OH)n]2–n (n = 0–5) with the (001), (100) and (203) or (101) surfaces of portlandite are predicted from the potential of mean force using classical molecular umbrella sampling simulation methods and the structural interactions are further explored using fully periodic density functional theory computations. Although uranyl is predicted to only weakly adsorb to the (001) and (100) clean surfaces, there should be significantly stronger interactions with the (203/101) surface or at hydroxyl vacancies, both prevalent under groundwater conditions. The uranyl surface complex is typically found to include four equatorially coordinated hydroxyl ligands, forming an inner-sphere sorbate by direct interaction of a uranyl oxygen with surface calcium ions in both the (001) and (203/101) cases. In contrast, on the (100) surface, uranyl is sorbed with its axis more parallel to the surface plane. The EXAFS data are largely consistent with a surface structural layer or film similar to calcium uranate, but also show distinct uranyl characteristics, with the uranyl ion exhibiting the classic dioxygenyl oxygens at 1.8 Å and between four and five equatorial oxygen atoms at distances between 2.28 and 2.35 Å from the central U absorber. These experimental data are wholly consistent with the adsorbate configuration predicted by the computational models. These findings suggest that, under the strongly alkaline conditions of a cementitious backfill engineered barrier, there would be significant uptake of uranyl by portlandite to inhibit the mobility of U(VI) from the near field of a geological disposal facility.

Artificial neural network modelling for biodecolorization of Basic Violet 03 from aqueous solution by biochar derived from agro-bio waste of groundnut hull: Kinetics and thermodynamics

In this study, Levenberg Marquardt back propagation algorithm was used to train the Artificial Neural Network (ANN) and to predict the adsorptive removal of cationic dye Basic Violet 03 (BV03) by biochar derived from biowaste of groundnut hull. The experimental conditions such as solution pH, biochar dose, initial dye concentration, contact time and temperature were used as input variables and BV03 percentage removal as target. The hidden and the output layer of the network was trained by tangent sigmoid and liner transfer functions. The feasibility of the adsorption process is evaluated by the kinetic studies and it exhibited that pseudo-second order kinetic models fit well with experimental data. The adsorbent stability and adsorption mechanism has been discoursed by the thermodynamic characteristics and sorption free energy. The predicted target values were compared with the experiment resulted in a better correlation coefficient of 0.9920. Thus, the results attained from this ANN model was found to be effective in predicting the percentage removal of BV03 dye at any given operating condition.

Equilibrium, kinetics and thermodynamics studies of Cd sorption onto a dithizone-impregnated Amberchrom CG-300m polymer resin

Amberchrom CG-300m, a styrene acrylic ester polymer resin, was studied for the first time as sorbent for metal ion sorption in a solid-phase extraction system. The polymer sorbent was modified via impregnation with dithizone to improve its efficiency. Efficiency of the modified sorbent improved by more than 47%. The loading capacity of the resin is 3.2 mg dithizone per gram of sorbent. The mechanisms of Cd(II) sorption from aqueous solutions are presented. Capacity of the modified resin for Cd(II) was investigated in batch experiments as a function of pH, initial metal ion concentration, temperature and time. Maximum capacity of 0.551 mg Cd(II) per gram of sorbent was achieved. The dimensionless separation factor, 0 < RL < 1, associated with the Langmuir isotherm (at T = 294 K) signifies sorption of Cd(II) was favorable, as do negative values of free energy of sorption (ΔG) at temperatures exceeding 293 K. Sorption was endothermic (ΔH > 0) while ΔS > 0 reflects the affinity of the sorbent towards Cd(II). The pseudo-second order model proved to be the best fit model for Cd(II) sorption kinetics data. Particle-diffusion models suggest sorption follows film as well as pore diffusion mechanisms.

Mathematical modeling and stimulation of thermodynamic parameters for the removal for Cr6+ from wastewater using chitosan cross-linked glutaraldehyde adsorbent

The presence of heavy metals such as chromium within water sources are considered as one of the most vital problem to the environment. Accumulating of chromium within the human body, can cause various diseases and disorders. Chitosan cross-linked glutaraldehyde adsorbent (formed from the acetyl group of chitin from alkaline solution) is widely a well-known adsorbent fore chromium metal removal present in solution. In the current study, mathematical modelling and the stimulation of thermodynamic parameters were done on crab chitosan cross-linked glutaraldehyde adsorbent for chromium (VI), Cr6+ removal. This was obtained through the prepared dichromate wastewater solution of 0.81 mg/L of Cr6+ per litre of distilled water. Adsorption experiments were also conducted in a bath system and the effect of stirring speed, chitosan cross-linked glutarladehyde dosages, contact time and temperature on the adsorption of Cr6+ were in investigated. The effectiveness of the cross-linked adsorbent at an optimum dosage (0.16 mg/L) for Cr6+) removal, from wastewater solution which was 82.3% of the initial concentration (0.81 mg/L) was found to be 0.8 g at 30 °C. The time required for the latter adsorption process to attain equilibrium was 80 min. For the thermodynamic study of the process of adsorption, properties such as Gibbs free energy (ΔGads), entropy (ΔSads) and enthalpy (ΔHads) values in the temperature ranges from 25 to 65 °C were also calculated in order to characterize the process. The free sorption energy was −47.56 kJ/mol which suggests the process was physical. The enthalpy of adsorption was −18.09 kJ/mol and the Gibbs free energies were all negative, thus the process was spontaneous and exothermic. The observed results in the current study indicated strange behavior that could not be depicted using the classical decay mathematical model. We concluded that only fractional differential operators with different kernels including the exponential decay, the power law and the generalized Mittag-Leffler function could be used to depict such observations.

KINETIC CHARACTERISTICS OF THE SORPTION PROCESS OF IONS LANTHANUM BY METALLURGICAL SLAG

The patterns of sorption of lanthanum ions from model nitrate solutions by metallurgical slag were investigated. It was shown that slag is a rather effective sorbent of lanthanum ions. The kinetics of sorption of lanthanum ions from model nitrate solutions by granulated blast furnace slag Zaporozhstal was studied. Based on the processing of integral kinetic sorption curves by the equations of diffusion kinetics, it was found that the sorption process proceeds in a mixed diffuse mode. The use of chemical kinetics models has shown that the stage of the chemical interaction of lanthanum ions with the functional groups of the sorbent also contributes to the overall speed of the process. According to Giles’ classification, isotherms of adsorption of lanthanum ions by slag belong to L-type isotherms. To obtain quantitative characteristics of the sorption of lanthanum ions on slag, the experimental results were processed using the sorption models of Langmuir, Freindlich, and Dubinin – Radushkevich. It has been established that experimentally the isotherm of sorption of lanthanum from model nitrate solutions by slag is well described by all models in the same range of equilibrium concentrations. The obtained value ΔG 0 sorb = -25.83 kJ/mol indicates a rather high affinityof the sorbent for the sorbate and the advisability of using granular slag for the extraction of lanthanum compounds from model nitrate solutions. Using the Dubinin-Radushkevich model, which indicates the nature of sorbate sorption on the sorbent, the average free sorption energy was calculated. Calculations showed that the value of the free energy of sorption E = 7.18-8.33 kJ/mol indicates the physical nature of the interaction of the sorbate with the sorbent.

SORPTION OF IONS LANTHANUM BY CLINOPTILITE

The patterns of sorption of lanthanum ions from model nitrate solutions by the natural sorbent clinoptilolite were investigated. It was shown that clinoptilolite is a rather effective sorbent of lanthanum ions. The kinetics of adsorption of lanthanum ions by clinoptilolite was studied. Based on the results obtained, it was established that the external and internal diffusion is the limiting stage of the process. Along with this, a certain contribution to the overall rate of the process is introduced and the stage of interaction of the adsorbed ions with the functional groups of clinoptilolite. According to Giles’s classification the isotherms of adsorption of lanthanum ions by clinoptilolite belong to L-type isotherms. To obtain quantitative characteristics of the sorption of lanthanum ions on clinoptilolite, the experimental results were processed using sorption models of Langmuir, Freindlich, and Dubinin – Radushkevich. It has been established that experimentally the isotherm of sorption of lanthanum from model nitrate solutions by the natural sorbent clinoptilolite is well described by all models in the same range of equilibrium concentrations. The obtained value ΔG 0sorb = -36.87 kJ/mol indicates a rather high affinity of the sorbent for the sorbate and the advisability of using clinoptilolite to extract lanthanum compounds from model nitrate solutions. Using the Dubinin-Radushkevich model, which indicates the nature of sorbate sorption on the sorbent, it was calculated average free energy of sorption. Calculations showed that the value of the free energy of sorption E = 12 kJ/mol indicates the chemical nature of the interaction of the sorbate with the sorbent. Thus, the process of sorption of lanthanum ions on the surface of clinoptilolite proceeds according to the ion-exchange mechanism, and the fixation of lanthanum ions has a chemical nature.

Defluoridation of water using a new biosorbent developed from Ficus glomerata Roxb. bark

Defluoridation of water through adsorption using biosorbents is currently attracting attention. A thermo-chemically developed biosorbent derived from Ficus glomerata bark was used in the present study. The adsorption data were analysed using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models at varying initial adsorbate concentrations (2–25 mg/l). It was found that the adsorption of fluoride onto F. glomerata biosorbent followed the Langmuir isotherm and the Langmuir isotherm constants a and b obtained were 2·27 mg/g and 0·651 l/mg, respectively, at an adsorbent dose of 5 g/l and temperature of 26 ± 1°C. The mean free sorption energy was found to be 8·770 kJ/mol, indicating that the adsorption of fluoride onto F. glomerata bark adsorbent was by a chemisorption mechanism. The kinetic study also supported chemisorption, with the adsorption data fitting well with pseudo-second-order kinetic model. The thermodynamic study indicated the spontaneous and endothermic nature (ΔH° = 15 430·78 J/mol) of fluoride adsorption onto F. glomerata adsorbent. Field scanning electron microscopy and energy dispersive spectroscopy, Brunauer–Emmett–Teller analysis and Fourier transform infrared spectroscopy were used to analyse the surface morphology of the adsorbent before and after the fluoride adsorption process. Practical application of F. glomerata Roxb. biosorbent to a fluoride-contaminated groundwater sample showed encouraging results.

Synthesis of magnetite-based nanocomposites for effective removal of brilliant green dye from wastewater.

The present study aims at evaluating the batch scale potential of cotton shell powder (CSP), Moringa oleifera leaves (ML), and magnetite-assisted composites of Moringa oleifera leaves (MLMC) and cotton shell powder (CSPMC) for the removal of brilliant green dye (BG) from synthetic wastewater. This is the first attempt to combine biosorbents with nanoparticles (NPs) for the removal of BG. The surface properties of ML, CSP, and their composites were characterized with Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX). The impact of dosage of the adsorbents (1-4g/L), initial concentrations of BG (20-320mg/L), pH (6-12), and contact time (15-180min) on BG removal was evaluated. The BG removal was in order of CSPMC > MLMC > CSP > ML (98.8-86.6% > 98.2-82.0% > 92.3-70.7% > 89.0-57.4%) at optimum dosage (2g/L) and pH (8). Moreover, maximum adsorption (252.17mg/g) was obtained with CSPMC. The experimental results showed better fit with Freundlich adsorption isotherm model and kinetic data revealed that sorption followed pseudo-second-order kinetic model. The values of Gibbs free energy and mean free energy of sorption showed that physical adsorption was involved in the removal of BG. FTIR results confirmed that -O-H, -C-OH, =C-H, -C-H, =-CH3, HC ≡ CH, C=C, -C=O, -C-N, and -C-O-C- groups were involved in the removal of BG. The results revealed that application of low-cost biosorbents combined with NPs is very effective and promising for the removal of textile dyes from wastewater.

Особенности сорбционного извлечения метаналя волокнистым ионообменником ФИБАН А-5W

Определены кинетические и равновесные характеристики сорбции метаналя волокнистымионообменником ФИБАН А-5W, имеющим в структуре вторичные и третичные аминогруппы, в ста-тических условиях. Установлено время достижения равновесия в системе раствор метаналя – сорбент.На основе подхода Бойда-Адамсона проведен анализ кинетических кривых сорбции, осуществленаоценка лимитирующей стадии процесса поглощения альдегида. Получены изотермы сорбции метана-ля при разных температурах и проведена их интерпретация с привлечением ряда известных моделей.Рассчитаны значения свободной энергии Гиббса процесса поглощения с использованием константысорбционного равновесия уравнения Ленгмюра.

Optimization of Samarium(III) Sorption using Nano-Zirconium Oxide by Taguchi Method

Sorption of samarium on nano zirconium oxide was carried out as a function of pH, contact time, initial metal ion concentration and temperature. Taguchi’s L-25 orthogonal array was adopted to identify the most influential factors accountable for enhanced sorption of Sm(III). In Taguchi analysis the sorption amounts (Qt) of Sm(III) ions were directed into an precise S/N ratio for a “high is better” response. By examining signal-to-noise ratio (S/N) the quality trail can be determined. The experiment performed under optimum conditions as predicted by Taguchi method resulted in enhanced Sm(III) sorption by zirconium oxide with minimum error. Analysis of variance indicated that the pH of Sm(III) is the most influential factor for high amount of sorption (Qt). Maximum sorption of 21.3 mg/g (Qe) was noticed from the solution of initial metal [samarium] ion concentration 0.5 ppm, temperature of 323 K, pH 6.9 and contact time of 50 min [Taguchi optimized factors]. Sorption followed both Dubinin- Radushkevich and Langmuir isotherms. The free energy of sorption was found to be 18.3 kJ mol-1. Pseudo second-order equation well fitted for the sorption kinetics. Sorption increased with increase in temperature. Sorption was endothermic in nature. Reichenburg equation was used to explain the diffusion process. The value of ΔG° was also evaluated. X-ray diffraction and high resolution transmission electron microscopy data supported that the size of the sorbent as 15.5 nm.

Simultaneous Adsorption and Incorporation of Sr2+ at the Barite (001)–Water Interface

Ionically bonded minerals are ubiquitous and play a determinative role in controlling the mobility of toxic metals in natural environments. However, little is known about the mechanism of ion uptake by these mineral surfaces. Here, the sorption of strontium ions (Sr2+) to the barite (001)–water interface was studied using a combination of synchrotron X-ray scattering and three types of computational simulations (density functional theory, classical molecular dynamics (CMD), and CMD-metadynamics). In situ resonant anomalous X-ray reflectivity (RAXR) revealed that Sr2+ adsorbed on the barite surface as inner-sphere surface complexes and was incorporated within the outermost barite atomic layers. Density functional theory combined with CMD simulations confirmed the thermodynamic stability of these species, demonstrating almost equal magnitudes in the free energy of sorption between these species. Metadynamics simulations showed a more detailed feature in the free energy landscape for metal adsorption where a...

Water sorption kinetics of acrylonitrile-butadiene rubber/poly(ethylene-co-vinyl acetate)/organoclay nanocomposites

Nanocomposites based on acrylonitrile-butadiene rubber (NBR) and poly(ethylene-co-vinyl acetate) (EVA) with several weight ratios (20, 40 and 60 wt% NBR) and 1, 3, 5 and 7 wt% organocaly (OC) were fabricated in an internal mixer. The diffusion of water through the specimens made of the unfilled blends and their nanocomposites was studied with special reference to the blend composition and OC content at three temperatures of 25, 40 and 55 °C using a gravimetric method. It was found that the transport coefficients, namely, diffusion coefficient (D), sorption coefficient (S) and permeation coefficient (P) increased with increasing of NBR content. In addition, while S and P increased systematically with the OC content, D decreased to some extent with the increase in the nanofiller concentration. The results revealed that the diffusion happened mainly through the polymeric materials. It was also found that the sorption process for all the materials studied was dominated by a Henry sorption mode giving an endothermic process. The change in entropy, enthalpy and free energy of sorption were also calculated using the experimental data. Schematic models were also proposed for water uptake of the blend and its nanocomposite counterpart.

Fabrication of Engineered Silica-Functionalized-Polyanilines Nanocomposites for Water Decontamination of Cadmium and Lead

In this study, two novel functionalized silica nanocomposites were synthesized via covalent bonding with nanopolyaniline (NPANI) and crosslinked nanopolyaniline (CrossNPANI) to produce [NSi-NPANI] and [NSi-CrossNPANI], respectively. The two nanocomposites were portrayed by SEM, FT-IR, HR-TEM, BET-surface and TGA. The HR-TEM images of [NSi-NPANI] and [NSi-CrossNPANI] confirmed the particle size in the range 14.28–21.43 and 26.19–35.71 nm, respectively and these two nanocomposites were successfully applied to remove divalent cadmium and lead from solutions. As compared to nanosilica [NSi] sorbent, the maximum capacity values of the two nanocomposites for divalent cadmium and lead were identified to increase from 100–250 µmole g−1 (pH 1.0) to 750–800 µmole g−1 (pH 7.0) and from 400–1050 µmole g−1 (pH 1.0) to 650–1350 µmole g−1 (pH 6.0), at the optimum conditions. The adsorption data were compared using two and three parameter equations based on Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Redlish-Peterson and sips models. The kinetic study of [NSi-NPANI] and [NSi-CrossNPANI] revealed that the pseudo-second order kinetic was the best model to explain the kinetic data for cadmium(II) and lead(II). The free energy of sorption (ΔGo), enthalpy (ΔHo), and entropy (ΔSo) changes were calculated to portend the nature of adsorption. Adsorptive extraction of toxic lead and cadmium from tap water and wastewater was successfully accomplished with the range of percentage recovery values 98.5–100.0 and 91.9–93.0%, respectively.

Analysis of equilibrium, kinetic, and thermodynamic parameters for biosorption of fluoride from water onto coconut (Cocos nucifera Linn.) root developed adsorbent

Abstract Drinking water with higher fluoride levels results in serious irremediable health problems that have attained a startle all over the world. Researches focused towards deflouridation through the application of biosorbents prepared from various plants are finding greater scope and significance. Present research is done on Cocos nucifera Linn. (coconut tree) one of the very commonly available plants throughout Kerala and around the globe. An adsorbent developed from the root portion of C. nucifera Linn. is used in the present study. Equilibrium study revealed that the fluoride uptake capacity is quite significant and linearly increases with initial adsorbate concentration. The adsorption data is analyzed for Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models at varying initial adsorbate concentrations (2–25 mg·L− 1). It is found that the adsorption of fluoride onto C. nucifera Linn. root adsorbent follows Langmuir isotherm. Langmuir isotherm constants “a” and “b” obtained are 2.037 mg·g− 1 and 0.823 L·mg− 1 at an adsorbent dose of 8 g·L− 1 and temperature (26 ± 1) °C. The mean free sorption energy, E obtained, is 9.13 kJ·mol− 1 which points out that the adsorption of fluoride onto C. nucifera Linn. root adsorbent is by chemisorption mechanism. The kinetic study also supports chemisorption with adsorption data fitting well with a pseudo-second-order kinetic model with an estimated rate constant K2 of 0.2935 g·mg− 1 min at an equilibrium contact time of 90 min. The thermodynamic study indicated the spontaneous and endothermic nature (ΔH = 12.728 kJ·mol− 1) of fluoride adsorption onto the C. nucifera Linn. root adsorbent. Scanning Electron Microscopy (SEM), BET, FTIR, and EDX methods were used to analyze the surface morphology of adsorbent before and after fluoride adsorption process. Experiments on deflouridation using C. nucifera Linn. root adsorbent application on fluoride contaminated ground water samples from fields showed encouraging results.

Optimized formulation of NiFe2O4@Ca-alginate composite as a selective and magnetic adsorbent for cationic dyes: Experimental and modeling study

This paper reports a data-driven modeling methodology undertaken to establish the optimal formulation of NiFe2O4@Ca-alginate composite designed for adsorption applications. Adsorbents were produced as anisotropic plate-like particles that were applied for removal of Rhodamine-6G (Rh6G) and Methylene Blue (MB) cationic dyes from aqueous solutions. Data-driven models were developed to establish the composition-performance relationships and to optimize the formulation of the composite adsorbent. The optimal formulation of NiFe2O4@Ca-alginate composite implied a content of 16% (w/w) NiFe2O4 nanoparticles into the alginate matrix. Likewise, kinetics, isotherms and thermodynamics studies were carried out and reported in this paper. The optimal adsorbent (NiFe2O4@Ca-alginate) yielded a remarkable maximal sorption capacity equal to 1243 mg/g (for MB uptake) and 845 mg/g (for Rh6G) at the room temperature (298 K). Dubinin-Radushkevich (D-R) isotherms revealed the mean free energy of sorption ranging from 7.23 to 9.26 (kJ/mol) suggesting that the mechanism of adsorption was based on both physical interactions and ion exchange. This evidence was also corroborated by the molecular docking simulations that highlighted valuable insights regarding the intermolecular interactions between alginate chains and cationic dyes.

Sorption studies of yttrium(III) ions on surfaces of nano-thorium(IV) oxide and nano-zirconium( IV) oxide

Sorption of yttrium on nano-thorium oxide and zirconium oxide was carried out as a function of pH, contact time, concentration, temperature and co-ions. The effect of initial yttrium ion concentration has been investigated in the range of 0.5–50 ppm for 1.0 mg of sorbent dosages. Maximum sorption of 10.5 mg/g in case of nano-thorium oxide and 18.0 mg/g in case of nano-zirconium oxide was noticed from the solution of initial metal ion concentration 0.5 ppm, temperature of 298 K, pH 6.9, shaking time of 120 min (nano-thorium oxide) and contact time of 50 min (nano-zirconium oxide) for the yttrium ion sorption. Sorption followed both Dubinin–Radushkevich and Langmuir isotherms. The free energy of sorption was found to be 8.77 kJ/mol (yttrium(III) vs nano-thorium dioxide) and 18.4 kJ/mol (yttrium(III) vs nano-zirconium oxide) using Dubinin–Radushkevich isotherm. Sorption increased with increase in temperature in the studied temperature range. Sorption was endothermic. And the values of ∆H°, ∆S° and ∆G° were also evaluated. Pseudo-second-order equation fitted for the sorption kinetics. Reichenberg equation was used to explain the diffusion process. The effects of co-ions on sorptions were also investigated. BET surface areas of sorbent particles were 33 m2/g for nano-zirconium oxide and 25 m2/g for nano-thorium oxide. X-ray diffraction and high-resolution transmission electron microscopy data revealed that the size of the sorbent particles was 4.7 and 15.5 nm for nano-thorium dioxide and nano-zirconium dioxide, respectively.

Sorption of Hg(II) and Zn(II) ions using lignocellulosic sorbent (date pits)

AbstractThis work focuses on the study of Hg(II) and Zn(II) sorption using pristine date pits. The effect of pH is evaluated before considering the influence of both temperature and contact time on sorption efficiency. Sorption isotherms are also determined and modelled using conventional models such as Langmuir, Freundlich, and Dubinin‐Radushkevich (D‐R) equations. The best fit was obtained with the Langmuir equation and maximum sorption capacities reached 38.5 and 52.6 mg · g−1, for Hg(II) and Zn(II), respectively. An analysis of the temperature effect by the Gibbs equation showed that the sorption is exothermic and spontaneous. The mean free energy of sorption (obtained from D‐R equation) confirms that metal binding occurs through a chemical ion‐exchange mechanism. The kinetic profiles can be accurately fitted with the pseudo‐second order rate equation. Complementary analyses (using FTIR spectrometry and SEM‐EDX analysis) confirm that ion‐exchange is the main binding mechanism, though a contribution of surface complexation cannot be neglected.

Organic Solvents Transport Through Alkali-Treated Agro-waste Microfibre Incorporated with Low Density Polyethylene Composites

We report the transport behaviour of low density polyethylene composites containing both untreated and alkali-treated agro-waste microfibre in three aromatic organic solvents (benzene, toluene, and xylene) at 40, 60 and 80°C by the conventional weight-gain method. The effects of fibre content, alkali treatment, and filler particle size on solvent sorption were analysed. Transport parameters such as diffusion coefficient, sorption coefficient, and permeation coefficient have been calculated in terms of microfibre content, particle size, nature of the solvent, and temperature. It was observed that all the systems follow the Fickian mode of transport on increasing temperature. The van’t Hoff’s relationship was used to determine the thermodynamic parameters and was found that the estimated free energies of sorption were all positive, indicating non-spontaneity of the solubility of micro fibre/LDPE composites. The first order kinetic rate constant and swelling parameters were also evaluated.