Three-parameter Isotherm Models Research Articles

Nonlinear Isotherm Adsorption Modelling for Copper Removal from Wastewater by Natural and Modified Clinoptilolite and Glauconite

The paper presents the results of the Cu2+ adsorption on natural and thermally/microwave-treated clinoptilolite and glauconite. XPS experiments were performed. The relationship between the adsorbed matter and the equilibrium concentration in wastewater is described by four two-parameter isotherm models and four three-parameter adsorption isotherm models.

Insights into isotherms, kinetics, and thermodynamics of adsorption of acid blue 113 from an aqueous solution of nutraceutical industrial fennel seed spent

Research studies have been carried out to accentuate Fennel Seed Spent, a by-product of the Nutraceutical Industry, as an inexpensive, recyclable and operational biosorbent for bioremediation of Acid Blue 113 (AB113) in simulated water-dye samples and textile industrial effluent (TIE). The physical process of adhesion of AB113 on the surface of the biosorbent depends on various parameters, such as the initial amount of the dye, amount and expanse of the biosorbent particles, pH of the solution and temperature of the medium. The data obtained was analyzed using three two-parameter and five three-parameter adsorption isotherm models to glean the adsorbent affinities and interaction mechanism of the adsorbate molecules and adsorbent surface. The adsorption feature study is conducted employing models of Weber-Morris, pseudo 1st and 2nd order, diffusion film model, Dumwald-Wagner and Avrami model. The study through 2nd order pseudo and Avrami models produced complementary results for the authentication of experimental data. The thermodynamic features, ΔG0, ΔH0, and ΔS0 of the adsorption process are acclaimed to be almost spontaneous, physical in nature and endothermic in their manifestation. Surface characterization was carried out using Scanner Electron Microscopy, and identification and determination of chemical species and molecular structure was performed using Infrared Spectroscopy (IR). Maximum adsorption evaluated using statistical optimization with different combinations of five independent variables to study the individual as well as combined effects by Fractional Factorial Experimental Design (FFED) was 236.18 mg g−1 under optimized conditions; pH of 2, adsorbent dosage of 0.500 g L−1, and an initial dye concentration of 209.47 mg L−1 for an adsorption time of 126.62 min with orbital shaking of 165 rpm at temperature 49.95 °C.

Designing novel perlite-Fe3O4@SiO2@8-HQ-5-SA as a promising magnetic nanoadsorbent for competitive adsorption of multicomponent VOCs

Volatile organic compounds (VOCs), which emerge as multicomponent pollutants through many industrial processes, pose a serious threat to human health and the eco-environment due to their volatility, toxicity and dispersion. Hence, the study of competitive adsorption of multicomponent VOCs is of practical and scientific importance. Herein, the perlite-supported Fe3O4@SiO2@8-hydroxyquinoline-5-sulfonic acid (perlite-Fe3O4@SiO2@8-HQ-5-SA) was designed as a novel magnetic nanoadsorbent by a simple strategy and employed for the competitive adsorption of multicomponent toluene, ethylbenzene and xylene in the vapor-phase targeted as VOCs. The successfully prepared perlite-Fe3O4@SiO2@8-HQ-5-SA was characterized by means of SEM, EDX, FT-IR, VSM and BET analyses. Adsorption capacities of 558 mg/g, 680 mg/g and 716 mg/g were achieved for single component toluene, ethylbenzene and xylene, respectively. It was concluded that the adsorption capacities for both binary and ternary components were significantly decreased compared to single component adsorption. The competitive adsorption capacity order of the binary and ternary component VOCs was xylene > ethylbenzene > toluene due to their competitive dominance. The rate-limiting kinetic analysis indicated that the adsorption rates were determined by both the film diffusion and intraparticle diffusion. The analysis of the error metrics demonstrated that the three-parameter isotherm models better described the adsorption data compared to the two-parameter models. In particular, the Toth model provided the closest fit to the experimental equilibrium data. The thermodynamic analysis indicated the spontaneous nature and probability (ΔG° <0), exothermic (ΔH° <0), physical (ΔH° <20 kJ/mol) and a declination in the degree of randomness (ΔS° <0) of the adsorption processes. The reuse efficiency of perlite-Fe3O4@SiO2@8-HQ-5-SA for toluene, ethylbenzene and xylene decreased to only by 88.91%, 88.07% and 87.16% after five recycles. The perlite-Fe3O4@SiO2@8-HQ-5-SA has a significant adsorptive potential compared to other adsorbents reported in the literature, thus it could be recommended as a promising nanoadsorbent for VOCs in industrial processes.

Investigation of adsorption of Basic Orange 2 dye on montmorillonite and error analysis

ABSTRACT. In this study, isotherm studies were investigated for the removal of basic orange 2 (BO2) dye on the montmorillonite surface. Two-parameter isotherm models such as Langmir, Freundlich, and Temkin isotherms and Three-parameter isotherm models such as Sips, Toth, and Khan isotherms were calculated by non-linear analysis method. The adsorption capacity at equilibrium was calculated by adding 0.035 g of adsorbent at 10-300 mg/L concentrations to 100 mL of synthetic dyestuff solution at room temperature. According to the results obtained, it was determined that the isotherm data matched the Langmuir isotherm with a regression coefficient of 0.995 from the Two-parameter models, and the Sips isotherm with a regression coefficient of 0.998 from the Three-parameter isotherm models. In addition, according to the results of error analysis, it was determined that the lowest error value fit the HYBRID model. SNE values support the HYBRID model.&#x0D; &#x0D; KEY WORDS: Adsorption, Basic orange 2, Isotherm models; Error analyses, Hybrid&#x0D; Bull. Chem. Soc. Ethiop. 2023, 37(1), 47-58. &#x0D; DOI: https://dx.doi.org/10.4314/bcse.v37i1.5

Mathematical modelling of moisture sorption isotherms of some fruits

The moisture sorption isotherms of some fruits namely pear and quince were determined at 15, 30, 45 and 60oC over a range of water activity from 0.110 to 0.920 using the standard, static-gravimetric method. The experimental sorption data were fitted with generated three-parameter sorption isotherm models on Mitrevski et al., and the referent Anderson model known in the scientific and engineering literature as Guggenheim-Anderson-de Boer (GAB) model. In order to find which models give the best results, large number of numerical experiments was performed. After that, several statistical criteria for estimation and selection of the best sorption isotherm model was used. The performed statistical analysis shows that the generated three-parameter model from Mitrevski et al. gave the best fit to the sorption data of pear and quince than the referent three-parameter Anderson model. Keywords: Sorption isotherms Pear Quince Statistical criteria

Adsorption of copper, and zinc onto novel Ca-alginate-biochar composite prepared by biochars produced from pyrolysis of groundnut husk

Alginate-based composites have been studied for adsorption technology as adsorbents due to their biocompatible, non-toxic, and cost-effective properties. In this work, groundnut husk biochar (GHB), calcium alginate (CA), and groundnut husk biochar/calcium alginate novel composites (%10) (CA-GHB1) and (% 20) (CA-GHB2) are synthesized and characterized using BET, SEM, EDX, FTIR, TGA. Adsorption performance is compared among GHB, CA, CA-GHB1, and CA-GHB2 composites to remove Cu(II), Zn (II) from aqueous solutions. Factors affecting adsorption, as well as kinetics, equilibrium, and thermal properties of adsorption, were studied using conventional equations. Adsorption isotherm models were used for two and three-parameter isotherm models to understand the interaction between the adsorbent and the adsorbate. 24.3, 44.6, 45.6, and 40.73 mg g−1 for removal of Cu(II) on GHB, CA, CA-GHB1, and CA-GHB2 and 32.16, 25.07, 36.09, and 40.55 mg g−1 for removal of Zn(II) on GHB, CA, CA-GHB1, and CA-GHB2 found maximum adsorption capacity (Qm) calculated from Langmuir isotherm. According to D-R isotherm data, the adsorption process is classified as physical adsorption. Thermodynamically, the adsorption process is non-spontaneous and endothermic.

The Preparation of Eco-Friendly Magnetic Adsorbent from Wild Water Hyacinth (Eichhornia crassipes): The Application for Removing Lead Ions from Industrial Wastewater

Water hyacinth ( Eichhornia crassipes) is a wild floating plant that can be found widely in pond or river areas. The plant grows fiercely and causes many harmful issues to the ecosystem around its covered area. This work provides a utilization method that converts wild water hyacinth to reliable magnetic biochar which can be used as a very effective adsorbent for the removal of lead ion Pb(II) in industrial wastewater. The mentioned magnetic biochar can be prepared via a modified pyrolysis process at 550°C with the support of cobalt sulfates as magnetite precursors and limited oxygen from the sweeping gas (the gas mixture ratio is 4 : 1 nitrogen/oxygen). The produced samples were hydrophobic biochar with high oxygen-containing functional groups that are suitable for the removal of inorganic contaminants. The impregnation of cobalt (II, III) oxides provided high magnetic separation performance and additional adsorption sites on the produced magnetic biochar. As indicated by the obtained result, the WHB-Co2M sample possesses a highly porous structure (0.126 cc/g), higher thermal stability (thermal durability reaches 900°C), relatively stable magnetic properties (14.74 emu/g), and a larger surface area (192 m2/g). These beneficial properties led to its suitability to serve as an adsorbent in removing lead ions in the contaminated effluent, recording 95% of removal efficiency and adsorption capacity of 67.815 mg/g. As indicated in the result, all prepared magnetic biochar samples were fitted to two-parameter (Langmuir models) and three-parameter (Sips model) isotherm models. Therefore, the adsorption process in this work could be carried out on both homogeneous and heterogeneous adsorbent surfaces. The adsorption kinetics of the removal process also was described by the pseudo-first-order, pseudo-second-order, and Elovich models to reveal the adsorption and desorption rate of the as-prepared magnetic biochar. This work indicates a successful waste refinery route of converting lignocellulosic biomass such as water hyacinth into value-added material for use as promising heavy metal adsorbents.

Fabrication of silica aerogel and carbon–silica composite for dynamic adsorption of benzene from dry and wet gas streams

ABSTRACT In the present study, the white kaolin-derived silica (SA) and silica-carbon aerogel composite (CSA) were successfully synthesised as useful adsorbents for the effective removal of benzene from dry and wet gas streams. The physicochemical features of the adsorbents were characterised using SEM, BET, XPS, and TGA, and the adsorption properties of benzene were investigated through breakthrough time curves and equilibrium study. The specific surface areas of SA and CSA were 628 and 783 m2 g−1, respectively, demonstrating the high porosity of the synthesised adsorbents. The dynamic adsorption and isotherm performances of SA and CSA confirmed that both adsorbents have superior adsorption properties and Khan isotherm for both developed adsorbents were the fittest model among the two- and three-parameter isotherm models studied and provided a maximum adsorption capacity of 366.2 and 224.4 for SA and CSA mg g−1, respectively. Furthermore, the reusability tests revealed that the SA and CSA could be efficiently recovered at 180°C. Our experimental outcomes indicated that the prepared SA and CSA can be applied as efficient and inexpensive adsorbents for the removal of benzene from gaseous streams.

Nanofibrous membrane of polyacrylonitrile with efficient adsorption capacity for cadmium ions from aqueous solution: Isotherm and kinetic studies

The nanofibrous membrane of polyacrylonitrile (NMP) was successfully synthesized after NaOH and NaHCO3 treatment aiming its functionalization using electrospinning for cadmium ion (Cd2+) adsorption. Field emission scanning electron microscopy (FE-SEM) revealed that small particles attached to the surface of functionalized PAN nanofibers. Equilibrium was attained after 60 min following a rapid uptake of Cd2+ with maximum adsorption capacity and percentage removal at an optimum solution pH of 7.0. The adsorbent dose of 0.3 g and 90 mg L−1 of initial Cd2+ concentration yielded the maximum adsorption capacity. The pseudo-second-order kinetic model was the best fitted to the adsorption data, indicating that the chemisorption is the controlling mechanism of adsorption. The physisorption was proposed based on the calculated values of the mean free energy of adsorption from the D–R isotherm (E < 8 kJ mol−1). Furthermore, three-parameter isotherm models indicated the homogeneous and heterogeneous Cd2+ adsorption onto NMP adsorbent.

Highly Efficient Adsorption of Cd(II) onto Carboxylated Camelthorn Biomass: Applicability of Three-Parameter Isotherm Models, Kinetics, and Mechanism

A series of malonic acid treated camelthorn (MATC) sorbents were produced via the reaction of camelthorn biomass with malonic acid, and factors affecting the extent of modification were investigated, including malonic acid concentration, dehydration time and temperature. The optimum sorbent, by carboxylic acid content, was subsequently characterised for surface charge behaviour (pHPZC), surface chemical functionalities (FTIR), morphological structure (SEM), and available surface area. The sorbent was subsequently utilised for adsorption of Cd(II) ions from aqueous media, and parameters influencing adsorption at 30 °C, such as sorbent dose, initial solution pH, exposure time, metal concentration, were investigated. Isothermal analyses were performed using eight models, including two and three parameter equations, with appropriateness of fit assessed via non-linear regression analysis. The adsorption data indicated that the Langmuir model gives the most appropriate fit to experimental curves, with the models ordered as Langmuir > Hill > Toth > Sips > Jossens > Khan > Redlich-Peterson > Freundlich. The highest uptake (qmax) of 582.6 mg g−1 was determined at pH 6. The Freundlich constants, KF and n, at 30 °C were found to be 24.94 mg g−1 and 2.33, respectively. The value of n (2.33), being in the range 0–10, indicates that adsorption of Cd(II) ions onto malonic acid treated camelthorn biomass is favourable. Evaluation of a series of kinetic models, allowed elucidation of the adsorption mechanism, as a pseudo-second order model gave the most appropriate fit, indicating that chemisorption processes are involved. Cd(II) ions adsorption onto MATC is enhanced by a higher level of active surface sites but was show to be independent of surface area. The work presented here indicates that this sorbent offers effective adsorption potential for Cd(II) ions from water, with potential in wastewater processing.

Batch and flow-through column adsorption study: recovery of Pt4+ from aqueous solutions by 3-aminopropyl(diethoxy)methylsilane functionalised zeolite (APDEMSFZ)

The recovery of platinum from waste is of high importance since significant concentrations are lost during processing, but the current methods are not economically effective. The removal of Pt4+ from aqueous solutions at different conditions using zeolite functionalised with 3-aminopropyl(diethoxy)methylsilane (APDEMS) was investigated. The adsorbent was used to assess the effect of adsorbent mass, pH, concentration, time and competing ions on the removal of Pt4+ so that optimum working conditions could be determined. The two- and three-parameter isotherm models as well as kinetic models were fitted using the experimental data. Effect of adsorbent bed height (2 and 5 cm), pH (2–7) and initial concentration (2 and 5 mg L−1) was determined with column experiments. Significant adsorption capacity was achieved with 100 mg adsorbent at pH 2, within 180 min. Adsorption capacity of Pt4+ significantly decreased at pH > 2. Higher bed depth increased the exhaustion and breakthrough times. The adsorption capacity of Pt4+ increased as bed height and concentration increased. The highest breakthrough and exhaustion times were achieved at pH 2. Strong Pt4+-adsorbent interaction concluded from the experiments, adsorption kinetics and isotherms models indicates that APDEMSFZ is suitable for Pt4+ recovery from mining wastewater.

One-pot synthesis of sodium lauryl sulfate-loaded polyacrylonitrile solid-phase extractor for investigating the adsorption behavior of radioactive strontium(II) from aqueous solutions

Sodium lauryl sulfate-loaded polyacrylonitrile (SLSLPAN) was synthesized in the present investigation using an in-situ one step process through gamma radiation-induced polymerization. The structure, composition, surface area and pore size and volume of the employed adsorbent were investigated by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and nitrogen adsorption-desorption measurements. Adsorption of radioactive strontium(II) onto SLSLPAN was studied in the pH range 3–13. Batch kinetic data showed that the equilibrium was attained at 840 min and the pseudo-first-order was the best kinetic model for describing the kinetic data of the present adsorption process. The diffusion of strontium(II) into SLSLPAN was deeply studied using four diffusion models, namely, Bangham, Boyd, Weber-Morris and Mathewas-Weber models. Two-parameter (Freundlich, Langmuir and Temkin) and three-parameter (Redlich-Peterson, Toth and Generalized) isotherm models were used to analyze the adsorption equilibrium data of strontium(II) onto SLSLPAN. The maximum adsorption capacity calculated by the Generalized isotherm model is found to be 0.391 mmol strontium(II) per gram of SLSLPAN. The estimated mean free energy (E = 2.151 kJ/mol) indicated that strontium(II) radionuclides were physically adsorbed onto SLSLPAN. The value of enthalpy change (ΔHo = 35.325 kJ/mol) and those of free energy change (ΔGo = −15.278, −16.948, −18.619 and −20.288 at 303, 313, 323 and 333 K, respectively) confirmed that adsorption of strontium(II) radionuclides on SLSLPAN was endothermic and spontaneous process.

Non-linear adsorption characteristics of modified pine wood sawdust optimised for adsorption of Cd(II) from aqueous systems

Abstract The facile modification of pinewood sawdust, with maleic acid, to produce a sorbent aimed at metal ion adsorption, was tested via the batch adsorption of Cd(II) ions from aqueous solution. The sorbent was characterized for the pH of zero point charge (pHZPC), spectroscopic evaluation of the surface functionalization, structural and morphological features. Factors affecting adsorption behavior, such as adsorbent dose, pH of solution, contact time and Cd(II) ion concentration were investigated. Results obtained show the adsorption rate to be comparatively fast, with equilibrium achieved after ∼35 min. Subsequent analysis, showed Langmuirian behavior and a monolayer adsorption capacity of 180.4 mg g−1, at pH 6; while data derived from two-parameter and three-parameter isotherm models was evaluated using non-linear regression methods, with error analysis, to determine the most appropriate model and allow prediction of optimum parameters. The Sips isotherm model proved the most appropriate in describing the experimental data obtained in the study; with a low level of heterogeneity in the adsorption sites occupied suggesting the interaction of the metal ions is preferential with the added carboxylate moieties only. Additionally, the rate of adsorption was analysed using a range of kinetic models (pseudo-first-order, pseudo-second-order, Bangham and Elovich) in their non-linear forms to provide insight into the adsorption mechanism and showing pseudo-second order behavior is observed, indicating two processes are key in the adsorption process, likely diffusion to the surface and subsequent adsorption on the carboxylate moieties incorporated by chemical modification. In conclusion, the sorbent produced in this study offers high potential for the removal of Cd(II) ions from aqueous solution due to the carboxylic functionalities incorporated into the material, which is optimized by solution pH and adsorbent dose.

Comparative assessment of raw and acid-activated preparations of novel Pongamia pinnata shells for adsorption of hexavalent chromium from simulated wastewater.

Current study deals with the comparative assessment for efficient adsorption of Cr(VI) from simulated wastewater using raw (NPP), phosphoric acid-activated (PPP) and sulphuric acid-activated (SPP) Pongamia pinnata shells. Physico-chemical alterations of the adsorbent were characterised by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), zeta-potential analysis, energy-dispersive X-ray spectroscopy (EDS) and total pore analysis using Brunauer-Emmett-Teller (BET). Parameters influencing the efficient biosorption of Cr(VI) species viz. initial pH of Cr(VI) solution, dosage of biosorbent, biosorbent-Cr(VI) contact period, initial concentration of Cr(VI) ions and reaction temperature were optimised. Various two-parameter and three-parameter isotherm models, kinetic models and thermodynamic studies were performed using equilibrium data. Langmuir adsorption capacity for NPP (raw biomass), PPP (phosphoric acid-activated biomass) and SPP (sulphuric acid-activated biomass) was found to be 96.2, 152 and 192mg/g, respectively. All the biosorbents gave best fit for pseudo-second-order model. Thermodynamic studies suggest spontaneous and endothermic interaction with increased degree of randomness. Effect of co-existing cations and anions on Cr(VI) biosorption onto the biosorbents implied that minimal competition and the biosorption capacity of the biosorbents for Cr(VI) species remained unaffected. Regeneration studies suggest that activated biosorbents can be used up to three times with continuous desorption.

Amidoxime Modified Polymers of Intrinsic Microporosity (PIM-1); A Versatile Adsorbent for Efficient Removal of Charged Dyes; Equilibrium, Kinetic and Thermodynamic Studies

Polymers of Intrinsic Microporosity (PIMs) are recognized as promising polymers for active separation of organic pollutants. These highly porous and solution-processable polymers could be tailored to remove specific targets from an aqueous system. In this study, PIM-1 powder was modified to amidoxime PIM-1 powder and adsorption of charged dyes which are Methylene Blue (MB, cationic) and Methyl Orange (MO, anionic) from an aqueous system was explored to evaluate the influence of contact time, initial concentration, solution pH and temperature on the removal of dyes. The adsorption reached the equilibrium within three hours in a batch adsorption process for both dyes. Experimental adsorption capacity (qe, exp) of Amidoxime PIM-1 was found as 79.8 mg g−1 and 69.8 mg g−1 for MO and MB, respectively at pH 6 and 298 K. The Amidoxime PIM-1 was also able to remove a mixture of anionic and cationic dyes simultaneously from aqueous system. The removal ability is dependent on the solution pH and the selectivity can be tuned by shifting solution pH such as at low pH (pH 3) anionic dye adsorption is more favourable, while at high pH (pH 10) cationic dye adsorption is preferable. Equilibrium data acquired from batch adsorption experiments have been examined by four two-parameter (Langmuir, Freundlich, Temkin and Dubinin–Radushkevich), four three-parameter (Redlich–Peterson, Sips, Khan and Liu) isotherm models, and by kinetic models such as the pseudo-first-order, the pseudo-second-order, Elovich equation and intraparticle diffusion using non-linear regression technique. Combination of several errors analysis techniques was applied to find the best fitting isotherm and kinetic models. Liu isotherm was the best to define the experimental data and the maximum adsorption capacities (qm) were calculated as 86.7 mg g−1 and 81.3 mg g−1 for MO and MB, respectively at pH 6 and 298 K. Adsorption data have the best consistency with the pseudo-second-order kinetic model. Furthermore, thermodynamic parameters were determined and the experiments suggested that the adsorption of MB and MO onto Amidoxime PIM-1 is a physical, spontaneous and exothermic.

Behavior of Ag species in presence of aquatic sediment minerals – In context of aquatic environmental safety

In recent years, there has been a growth in the number of products containing Ag nanoparticles (AgNPs) in many areas and their use suggests that the water-soil environment may be exposed to the contaminant with different Ag species.Therefore, the sorption of two Ag forms (i.e. Ag(I) ions and nanoparticles – AgNPs) on clay minerals (montmorillonite and kaolinite) and iron (oxyhydr)oxides (ferrihydrite) as a function of solution:mineral ratio (100:1, 250:1, 500:1), solution pH (3.0, 5.5 and 7.0) and initial Ag concentration (0.1–100 mg/dm3) was studied using batch method. In addition the binding strength/mobility of the bonded Ag species was researched. The results show a great sorption potential of clay minerals for both Ag forms and lower sorption capacity of ferrihydrite, in particular for Ag(I) ions. The maximum sorption capacities of montmorillonite, kaolinite and ferrihydrite estimated from three-parameter isotherm model of Sips were 94.39 mg/g, 117.8 mg/g and 26.48 mg/g for AgNPs and 17.92 mg/g, 21.14 mg/g and 3.072 mg/g for Ag(I) ions, respectively. Aggregation process plays an important role in sorption and mobility of AgNPs.The sequential extraction study indicated different binding mechanisms of the Ag forms onto the clay minerals and ferrihydrite, which depended on the active sites of minerals as well as the Ag species nature in the solution. Ag(I) was weakly bound by clay minerals but presence of iron (oxyhydr)oxides decreased the Ag(I) mobility and bioavailability. On the other hand, AgNPs bound with the active centers of minerals in a very strong way and were not able to release into water.The study of the binding of Ag forms by clay minerals and (oxyhydr)oxides allows to determine the influence of their physicochemical and structural properties, including e.g. pore size on Ag sorption. These results allow these properties to be taken into account in the study of environmental samples, including waters and soils.Moreover, the results showed that in the study of behavior of Ag forms in contact with the minerals, in addition to the sorption capacity, the susceptibility to their release is very important.Studies on sorption/desorption of AgNPs and Ag(I) ions as a form of oxidation of AgNPs is important for understanding the transport and fate of the Ag species in soil, sediments and surface water because of different their behavior in contact with the minerals.

Kinetic and isotherm modeling for acid blue 113 dye adsorption onto low-cost nutraceutical industrial fenugreek seed spent

The present study reports about the use of fenugreek seed spent as a new and efficient biosorbent for the removal of acid blue 113 dye from aqueous media and textile industrial effluent. The spent is a low-cost by-product of nutraceutical industry. The effects of various process parameters of adsorption, such as pH, initial dye concentration, adsorbent dose, adsorbent particle size, contact time and temperature onto nutraceutical industrial fenugreek seed spent (NIFGS) have been studied. Four numbers of two-parameter and six numbers of three-parameter isotherm models were used in the analysis of adsorption equilibrium data. Kinetic studies data conformed to pseudo-second-order model. Molecular diffusion studies were carried out using Weber–Morris, Dumwald–Wagner and film diffusion models. Change in enthalpy (ΔH°), entropy change (ΔS°) and Gibbs free energy change (ΔG°) of adsorption system indicated that the process is physisorption. Scanning electron microscopy, Fourier transform infrared spectroscopy and point of zero charge were used in characterizing the adsorbent. Fractional factorial experimental design and analysis of variance along with statistically developed model for adsorption helped to predict for a maximum adsorption of 661.5 mg g−1 using NIFGS. Application of NIFGS to textile industrial effluent and scaling up of the experimental process by three orders gave encouraging results.

Sugarcane Bagasse as an Efficient Biosorbent for Methylene Blue Removal: Kinetics, Isotherms and Thermodynamics.

Adsorption in biomass has proven to be a cost-effective option for treatment of wastewater containing dyes and other pollutants, as it is a simple and low cost technique and does not require high initial investments. The present work aimed to study the adsorption of methylene blue dye (MB) using sugarcane bagasse (SCB). The biomass was characterized by scanning electron microscopy (SEM). Adsorption studies were conducted batchwise. Kinetics, adsorption isotherms, and thermodynamics were studied. The results showed that SCB presented a maximum adsorption capacity of 9.41 mg g−1 at 45 °C after 24 h of contact time. Adsorption kinetics data better fitted the pseudo-second order model, indicating a chemical process was involved. The Sips’s three-parameter isotherm model was better for adjusting the data obtained for the adsorption isotherms, indicating a heterogeneous adsorption process. The process showed to be endothermic, spontaneous, and feasible. Therefore, it was concluded that SCB presented as a potential biosorbent material for the treatment of MB-contaminated waters.

Adsorption of Eu(III) onto bentonite and phyllite: A comparative study

Disposal of radioactive wastes in underground repositories necessitates knowledge on adsorption and mobility of radionuclides in host rocks (geologic barrier) and in engineered barriers, including clay barrier. The batch adsorption of Eu(III) (a homologue for trivalent radionuclides) onto phyllite compared to bentonite was studied as a function of solution pH (4.5 and 7.0), solution to clay rock ratio (10:1, 100:1, 500:1 and 1000:1), and various Eu(III) concentrations (0.01–190 mg/L; 0.658 × 10−7–1.25 × 10−3 M). The experimental data were interpreted using the isotherm models of Langmuir, Freundlich, Dubinin-Radushkevich, Tóth, and Sips. Adsorption/desorption experiments and bonding strength calculations showed that the adsorption behavior depends on the mineral composition of sorbents, solution pH, the initial concentration of Eu(III), and liquid: solution ratio (L:S). The cation exchange within the interlayer space of montmorillonite is the main adsorption mechanism in bentonite. Cation exchange on the minerals surface, chemical reactions leading to the precipitation of new phases, the electrostatic effect at a low initial concentration of Eu (III), and pH > pHPZC are adsorption mechanisms in phyllites. Solution pH has a pronounced effect on the Eu(III) adsorption onto phyllite due to surface protonation. Fe-oxides and hydroxides play a significant role in the adsorption/desorption of Eu(III) on phyllites. The best fitting was obtained for three-parameter isotherm models of Sips and Tóth. The mechanism of Eu(III) binding is complex and does not follow the ideal monolayer adsorption. While the maximum adsorption capacity of phyllite is 2.5 to 6.6 times lower than of bentonite, depending on the solution pH, it is high enough to guarantee efficacious and durable removal of actinides from the contaminated solutions, particularly at their low concentrations. Phyllites adsorption and mechanical properties make them suitable additives to bentonite in a clay barrier.

Thermodynamic, kinetic and equilibrium isotherm studies of As(V) adsorption by Fe(III)-impregnated bentonite

Arsenic removal has received much attention all over the world because of its toxicity and carcinogenicity. In the current research, the adsorption behavior of As(V) from aqueous solution onto Fe(III)-impregnated bentonite (Fe-Bent) was examined. Adsorption experiment results showed that the adsorption capacity of initial bentonite clay (Bent) was increased by Fe(III)-impregnation method. In Fe-Bent, the mononuclear Fe(III) cations, small oligomeric cluster and bulky FexOy particles were made such active sites identified by UV–Vis spectroscopy. X-ray diffraction results showed that Fe(III) species presented mainly in both crystalline and amorphous forms on the external surface of Fe-Bent. In an experimental study, the effect of different parameters such as contact times, arsenic concentrations, adsorbent dosages, pH and temperature conditions was investigated. Fe-Bent sample represented the maximum adsorption capacity of 10.06 mg L−1 to remove 5–20 mg L−1 of As(V) at pH = 6 and ambient temperature. In this experiment, the residual As(V) concentration decreased to less than 0.01 mg/L with the adsorption efficiency of 99% (i.e., below the limit of the WHO). The two- and three-parameter isotherm models revealed the best fit to the Freundlich, Sips, Toth, Temkin and Langmuir models, respectively. The isotherm models indicated the strong adsorption between arsenic and Fe-Bent. The adsorption kinetics was also considered by first-order, second-order and Elovich rate equations. It was noticed that the Fe-Bent adsorption followed the external surface reaction such as ligand exchange and surface complexation. The thermodynamics studies exposed that the process was spontaneous and endothermic for Fe-Bent.