Dubinin-Radushkevich Isotherm Equations Research Articles

Removal of Th(IV) from groundwater by adsorption onto nano-Kaolin and nano-Kaolin/MnFe2O4 composite

ABSTRACT The adsorption of Th(IV) ions by nano-Kaolin and nano-Kaolin/MnFe2O4 composite were studied as a function of pH, sorbent mass, time, and temperature. Kinetic data was fitted to pseudo second-order model, and the maximum value of the adsorption capacity of the monolayer (qm) for nano-Kaolin and nano-Kaolin/MnFe2O4 was at pH 3. The Langmuir, Freundlich, and Dubinin–Radushkevich isotherm equations were fitted to the adsorption data and the proper constants were calculated. From adsorption isotherms at different temperatures, ΔH° (endothermic), ΔG° (favourable), and ΔS° (positive) were calculated.

Radionuclides' Recovery from Seawater Using FIC and FIC A Sorbents.

To solve radioecological and oceanological problems (estimate the vertical transport, flows of particulate organic carbon, phosphorus biodynamics, submarine groundwater discharge, etc.), it is necessary to determine the natural values of the radionuclides' activity in seawater and particulate matter. For the first time, the radionuclides' sorption from seawater was studied using sorbents based on activated carbon modified with iron(III) ferrocyanide (FIC) and based on activated carbon modified with iron(III) hydroxide (FIC A-activated FIC) obtained by FIC sorbent treatment with sodium hydroxide solution. The possibility of trace amounts of phosphorus, beryllium, and cesium recovery in laboratory conditions has been investigated. Distribution coefficients, dynamic, and total dynamic exchange capacities were determined. The physicochemical regularities (isotherm and kinetics) of sorption have been studied. The results obtained are characterized via Langmuir, Freindlich, and Dubinin-Radushkevich isotherm equations, as well as pseudo-first and pseudo-second-order kinetic models, intraparticle diffusion, and the Elovich model. Under expeditionary conditions, the sorption efficiency of 137Cs using FIC sorbent, 7Be, 32P, and 33P-using FIC A sorbent with a single-column method by adding a stable tracer, as well as the sorption efficiency of radionuclides 210Pb and 234Th with their natural content by FIC A sorbent in a two-column mode from large volumes of seawater was assessed. High values of efficiency of their recovery by the studied sorbents were achieved.

Phenol removal from aqueous environments by natural & chemically modified kaolin clay

AbstractNatural, acid and base modified kaolin clays were studied for the sake of phenol and 4‐chlorophenol removal from aqueous environments and their application to real ground and industrial wastewater samples. Scanning electron microscope (SEM), infrared spectroscopy (IR), X‐ray diffraction (XRD), Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA), and Surface area analysis were employed for characterization of the adsorbents microstructure. Operating factors such as adsorbent dose, solution pH, initial phenol concentration, and contact time were studied. The experimental data displayed that the increase of the adsorbent dose, contact time, and pH value from 2 to 7 increases the efficiency of the removal process. Optimal conditions for phenolic removal were; contact time of 300 min, primary phenol solution of 25 mg/L, pH 7 and 2.5 g/L as an appropriate adsorbent dose using crude (natural), acid modified and base modified kaolin clays. The higher phenolic removal efficiencies were obtained at 5 mg/L as 90, 97, 96.2%, respectively, for the adsorbents in the previously mentioned order. The adsorption capacity in the removal of phenol and 4‐chlorophenol were 7.481 and 4.195, 8.2942 and 3.211, and 8.05185 and 18.565 mg/g, respectively, for the adsorbents in the same mentioned order. The adsorption equilibrium data were fitted and analyzed with four isotherm models, namely, Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm equations. The adsorption process of phenol on studied adsorbents was exothermic, spontaneous and thermodynamically favorable proved by the negative values of their thermodynamic parameters ΔH° and ΔG°. The correlation coefficient (R2) for all concentrations was higher than 0.94, which indicates that in the studied system, the data suitably fit the first‐order kinetics. The % desorption capacity was amounted to 96%, 91.11%, and 87.06% of adsorbed phenol, respectively, for the adsorbents in the previous order using 0.1N NaOH and 10% V/V ethanol solutions as eluents at 25°C, indicating the reusability of the adsorbents. Kaolin and its modified forms can be introduced as eco‐friendly and low‐cost adsorbents in water remediation implementation.

A comparison of anionic and cationic dye removal efficiency of industrial bauxite waste red-mud

Sorption characteristics of the acid-activated bauxite waste red-mud for Nylomine-Blue and Methylene-Blue were investigated to predict its potential removal ability for anionic-di-anthraquinone and cationic-thiazine-dyes, respectively. Surface characteristics of the red-mud were examined using atomic-force-microscopy, diffuse-reflectance-Fourier-transform, and X-ray-diffraction spectroscopy techniques. Kinetic data obtained at four different temperatures fit well to the pseudo-second-order and homogeneous-surface-diffusion models. The experimental Nylomine-Blue sorption capacity (0.020 mmol/g) is higher than that of Methylene-Blue (0.012 mmol/g) at 288 K but they change oppositely with the temperature and attain 0.013 and 0.043 mmol/g at 318 K, respectively. Experimental equilibrium data for Methylene-Blue and Nylomine-Blue are well predicted by the Freundlich, Langmuir, and Dubinin-Radushkevich isotherm equations. The mean-sorption-energies fall into the ion-exchange range for Methylene-Blue but electrostatic-attraction-forces play a more important role in Nylomine-Blue sorption. These mechanisms were correlated to the pH changes in the sorption process and the differences in the diffuse-reflectance-Fourier-transform spectra of dye-loaded sorbents. The atomic-force-microscopy topography and phase images revealed that the hematite and sodalite appear as hills on the red-mud surface but gibbsite and calcite minerals cover the valleys. The Methylene-Blue molecules are sorbed by ion-exchange in the positively-charged-valleys in dilute solutions but Nylomine-Blue is sorbed specifically on overall surface in whole concentration range.

Effect of ionic strength on methylene blue sorption onto macroporous resins: a comprehensive study

In the current study, adsorption behaviors of amberlite XAD-7 and XAD-16 for the removal of methylene blue from its aqueous solutions have been reported with several respects. First, response surface approach (RSA) has been used to identify the optimum conditions (0.21 g resin/10 mL MTB solution under 149 rpm mixing speed of shaking bath) for the best adsorption process of methylene blue (MTB) removal (≈99%). The most significant process parameter was found to be solution volume, followed by resin amount and speed. Effects of fluoride and chloride on the MTB removal have been also investigated. Elevated concentration of ions in MTB solutions gave rise to decline the adsorption capacity regularly, while the adsorption yield enhanced by increase in pH. On the other hand, the concerned adsorption system was a chemisorption process based on the kinetic (pseudo-first order, pseudo-second order, intraparticle diffusion models) and equilibrium (Langmuir, Freundlich, Temkin, Dubinin–Radushkevich isotherm equations) parameters.

Removal of Pb (II) Ion and Safranin Dye from Aqueous Solution by Sheep Wool

The ability of sheep wool to remove Pb(II) ions and safranin dye from aqueous solutions through the adsorption process was investigated at room temperature. The metal ions concentration was determined by flame atomic absorption spectrophotometer method. The influence of pH, contact time, amount of adsorbent, temperature and initial metal ions concentration were examined by the batch method. The experimental data were analyzed using the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm equations. The correlation coefficients were determined by analyzing each isotherm. The results indicate that the experimental data show better correlation with the Freundlich isotherm for Pb(II) ion and Langmuir isotherm for safranin dye than other isotherms. Thermodynamic parameters such as Gibbs free energy enthalpy and entropy have also been evaluated and it has been found that the sorption process was feasible, spontaneous and exothermic. The maximum amounts of Pb(II) and safranin dye adsorbed (qm), that show in order of 12.787 mg/g for Pb(II) and 4.6533 mg/g for safranin of wool sheep. The morphological analysis of the wool sheep was performed by the Scanning Electron Microscopy (SEM).

Amine-functionalized magnetite-silica nanoparticles as effective adsorbent for removal of uranium(VI) ions

In our studies the Fe3O4/SiO2/C3H6NH2 (MSA) adsorbent was synthesized by the green-chemistry method based on hydrolysis and condensation of tetraethoxysilane and (3-aminopropyl)triethoxysilane. The obtained material was fully characterized by a wide range of instrumental techniques and employed as an adsorbent for removal of uranium(VI) ions which is considered as a hazardous metal. It was found that the adsorption process is very fast, and equilibrium is reached after about 4 h. The data was fitted with the pseudo-1st (PFO) and pseudo-2nd order (PSO) equations. It was turned out that better fit was obtained for the PSO kinetic model. The Freundlich, Langmuir–Freundlich and Dubinin–Radushkevich isotherm equations were used to calculate the equilibrium adsorption data. The static sorption capacity was 118 mg·g−1. The energy value En = 14.8 kJ·mol−1 (293 K) calculated based on the Dubinin–Radushkevich isotherm equation indicates that chemisorption is a dominant mechanism. The obtained data show that MSA material can be used as a promising adsorbent for radioactive metals removal.

Adsorptive Removal of Methylene Blue Using Magnetic Biochar Derived from Agricultural Waste Biomass: Equilibrium, Isotherm, Kinetic Study

Wastewater discharge from textile industries contribute much to water pollution and threaten the aqua ecosystem balance. Synthesis of agriculture waste based adsorbent is a smart move toward overcoming the critical environmental issues as well as a good waste management process implied. This research work describes the adsorption of methylene blue dye from aqueous solution on nickel oxide attached magnetic biochar derived from mangosteen peel. A series of characterization methods was employed such as FTIR, FESEM analysis and BET surface area analyzer to understand the adsorbent behavior produced at a heating temperature of 800[Formula: see text]C for 20[Formula: see text]min duration. The adsorbate pH value was varied to investigate the adsorption kinetic trend and the isotherm models were developed by determining the equilibrium adsorption capacity at varied adsorbate initial concentration. Equilibrium adsorption isotherm models were measured for single component system and the calculated data were analyzed by using Langmuir, Freundlich, Tempkin and Dubinin–Radushkevich isotherm equations. The Langmuir, Freundlich and Tempkin isotherm model exhibit a promising R2-correlation value of more than 0.95 for all three isotherm models. The Langmuir isotherm model reflectsan equilibrium adsorption capacity of 22.883[Formula: see text]mg[Formula: see text]g[Formula: see text].

Assessment of hydrothermally modified fly ash for the treatment of methylene blue dye in the textile industry wastewater

Dyes and pigments are one of the major water pollutants and if not discharged properly cause ecological disturbance. Considering this, the current study investigates the application of thermal power plant by-product, i.e., fly ash for the elimination of a hazardous methylene blue dye from its synthetic aqueous solution. Experiments were conducted in batch mode to study the effect of pH, temperature, adsorbent dose and contact time. Highest dye removal (94.3%) was achieved at pH 10 using adsorbent dose of 10 g/L in 90 min of contact time at 40 °C. However, for cost-effective operation at neutral pH and room temperature (30 °C), it yields 89.3% dye removal having similar dose and contact time. Equilibrium isotherms for adsorption were analyzed by Langmuir and Freundlich, Temkin and Dubinin–Radushkevich isotherm equations. The results revealed that the best fit model of adsorption closely followed Langmuir adsorption. Based on adsorption isotherm models, thermodynamics parameters ΔG, ΔH and ΔS were calculated. The negative value of ΔG and ΔH revealed that adsorption process was exothermic, spontaneous and physical. The present work suggests that through simple process hydrothermally modified fly ash has the potential to be used as cost-effective and efficient adsorbent for the treatment of wastewater from textile industries.

Biosorption of Cd(ll), Cu(ll) and Ni(ll) Ions from Aqueous Solution Using Jatropha Curcas Seed Pod

Batch adsorption studies were conducted to determine the extent and nature of adsorption of Ni(ll), Cu(ll) and Cd(ll) ions from aqueous solutions onto JatrophacurcasSeed pod. The effects of pH, initial metal ion concentration and presence of co-ions were studied. Results showed that the adsorption process was dependent on pH, having optimum pH for adsorption of Ni(ll) at 7.0 and with maximum amount adsorbed as 9.23 mg/g. That of Cu(ll) occurred at pH 8.0 with maximum amount adsorbed as 9.65 mg/g while for Cd(ll), the pH for optimum adsorption occurred at pH 6.0 with maximum amount of 9.99 mg/g adsorbed. Evaluation of percentage removal shows that the percentage of Ni(ll), Cu(ll) and Cd(ll) adsorbed at their optimum pH corresponded to 92.30%, 96.50% and 99.90% respectively. Increasing the initial concentration of the metal ions was also found to increase the adsorption capacity for the metal ions by the adsorbent. The experimental data were interpreted using three isotherm models viz; the Langmuir, Freundlich and Dubinin-RadushKevich isotherms. Results showed that the Freundlich isotherm provided the best fit to the experimental adsorption data. The mean free energy values, E (which ranged from 1.343 to 2.275 kJ mol-1) calculated from the Dubinin-RadushKevich (D-R) isotherm equation suggests weak interaction between the metal ions and the adsorbent, thus revealing that the mode of the adsorption process follows physisorption. Assessment of competitive adsorption of the metal ions from mixed metal ions solutions shows that the presence of foreign ions in the solution diminished the adsorption density of the metal ion under consideration. The results generally showed that the order of adsorption of the metal ions onto the biosorbent follows the trend Cd(ll) > Cu(ll) > Ni(ll).

Co-modified MCM-41 as an effective adsorbent for levofloxacin removal from aqueous solution: optimization of process parameters, isotherm, and thermodynamic studies.

Antibiotics are emerging contaminants due to their potential risks to human health and ecosystems. Poor biodegradability makes it necessary to develop effective physical-chemical methods to eliminate these contaminants from water. The cobalt-modified MCM-41 was prepared by a one-pot hydrothermal method and characterized by SAXRD, N2 adsorption-desorption, SEM, UV-Vis DR, and FTIR spectroscopy. The results revealed that the prepared 3% Co-MCM-41 possessed mesoporous structure with BET surface areas at around 898.5m2g-1. The adsorption performance of 3% Co-MCM-41 toward levofloxacin (LVF) was investigated by batch experiments. The adsorption of LVF on 3% Co-MCM-41 was very fast and reached equilibrium within 2h. The adsorption kinetics followed the pseudo-second-order kinetic model with the second-order rate constants in the range of 0.00198-0.00391gmg-1min-1. The adsorption isotherms could be well represented by the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm equations. Nevertheless, D-R isotherm provided the best fit based on the coefficient of determination and average relative error values. The mean free energy of adsorption (E) calculated from D-R model was about 11kJmol-1, indicating that the adsorption was mainly governed by a chemisorption process. Moreover, the adsorption capacity was investigated as a function of pH, adsorbent dosage, LVF concentration, and temperature with help of respond surface methodology (RSM). A quadratic model was established, and an optimal condition was obtained as follows: pH8.5, adsorbent dosage of 1gL-1, initial LVF concentration of 119.8mgL-1, and temperature of 31.6°C. Under the optimal condition, the adsorption capacity of 3% Co-MCM-41 to LVF could reach about 108.1mgg-1. The solution pH, adsorbent dosage, LVF concentration, and a combination of adsorbent dose and LVF concentration were significant factors affecting the adsorption process. The adsorption thermodynamic functions were also determined. The negative ΔH 0 (-33.50kJmol-1) and ΔS 0 (-43.57Jmol-1K-1) suggested that the adsorption was an exothermic process accompanied by decreasing disorder. This study may indicate that 3% Co-MCM-41 is a promising adsorbent for removing emerging pollutants of LVF from water.

Synthesis of europium metal–organic framework (Eu-MOF) and its performance in adsorptive desulfurization

Europium metal organic framework (Eu-MOF) was synthesized using Europium as metal ion center and 1,3,5-trimesic acid (H3BTC) as organic ligand under hydrosolvothermal conditions. The dynamic performance of the Eu-MOF material in adsorption desulfurization processes was investigated using a solution of thiophene/n-octane as sulfur containing quality model oil. The adsorption desulfurization kinetics equations and adsorption desulfurization isotherms of Eu-MOF were also studied. The results have shown that Eu-MOF catalyst has very good adsorption desulfurization abilities under optimum desulfurization conditions of madsorbent: mmodel oil ratio of 1:100 and reaction temperature of 303 K. After 4 h of desulfurization reaction, the adsorption rate and the adsorption desulfurization capacity has reached 64.70% and 24.59 mgS/gMOF respectively. The Eu-MOF adsorption desulfurization process of thiophene on Eu-MOF fits well the quasi two level dynamic model using Langmuir isotherm, Freundlich isotherm and Dubinin–Radushkevich isotherm equations. The Dubinin–Radushkevich isotherm can be a suitable description of adsorption process for Eu-MOF absorbent on thiophene/n-octane mode oil. However the Freundlich isotherm equation model with fitting R 2 value closer to 1, can be a better description for the adsorption of thiophene. The adsorption of thiophene over Eu-MOF absorbent has two types of adsorption that occur simultaneously. These are the monolayer physical adsorption and the multilayer chemical adsorption.

Removal of colorant from simulated wastewater by phyco-composite material: Equilibrium, kinetic and mechanism studies in a lab-scale application

The biosorption properties of a novel phyco-composite material composed of Spirogyra sp. and Rhizoclonium sp. filamentous green algal biomasses for a model colorant (Basic Red 46, Br46) from simulated wastewater were first explored with respect to medium pH, biomaterial quantity, colorant concentration and contact time. The pseudo-second-order model represented the biosorption kinetic data well. Among biosorption isotherm models, Sips model provided the best fit to the equilibrium data. The phyco-composite biosorbent exhibited best performance at pH9 with maximum biosorption capacity of 55.953mgg−1 for Br46. The mean free energy (E) from Dubinin–Radushkevich isotherm equation and the standard Gibbs free energy change (ΔG°) revealed a feasible, spontaneous and physical biosorption process. Thus, this novel composite material can be used as a promising biosorbent to remove such unsafe colorants from aqueous media.

Adsorption of copper(II) from aqueous solutions on activated carbon prepared from grape bagasse

Activated carbons were prepared from grape bagasse by chemical activation using phosphoric acid and the prepared activated carbons were used to remove copper(II) from aqueous solutions. The effects of impregnation ratio (IR) and activation temperature on activated carbon production were investigated. The produced activated carbons were characterized by N2 adsorption, scanning electron microscopy (SEM), Boehm titration and Fourier transform infrared (FTIR) techniques. The highest surface area (1455 m2/g) and total pore volume (0.88 cm3/g) were obtained at a carbonization temperature of 500 °C with an impregnation ratio of 5/1. The resulting activated carbon was used for removal of copper(II) from aqueous solution. The effects of initial pH, temperature and contact time were investigated. The adsorption isotherm studies were performed and the obtained data were analyzed using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) equations. The Langmuir and Dubinin–Radushkevich isotherm equations showed better fit for all temperatures and the maximum adsorption capacity of copper(II) was obtained as 43.47 mg/g at 45 °C. Pseudo first order, pseudo second order, Elovich and intraparticle diffusion kinetic models were used in this study to describe the adsorption process. The rate of adsorption was found to conform to the pseudo second-order kinetic model.

Isotherm, kinetic, and thermodynamic studies on the adsorption behavior of malachite green dye onto montmorillonite clay

ABSTRACTSystematic batch mode studies of adsorption of malachite green (MG) on montmorillonite clay were carried out as a function of process parameters which include pH, adsorbent dosage, agitation speed, ionic strength, initial MG concentration, and temperature. Montmorillonite was found to have excellent adsorption capacity. Equilibrium adsorption isotherms were measured for the single-component system, and the experimental data were analyzed by using Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm equations. It was found that the Langmuir equation appears to fit the equilibrium data. The monolayer (maximum) adsorption capacity (qm) was found to be 262.494 mg g−1 for montmorillonite. The experimental kinetic data were analyzed using the first-order, second-order, Elovich, and intraparticle kinetic models and the second-order kinetic model described the adsorption kinetics accurately for MG. Thermodynamic activation parameters such as ΔG*, ΔS*, and ΔH* of the adsorption of MG on montmorillonite were also calculated.

Removal of hexavalent chromium by chemical modification of 4,4′-((1Z,11Z)-2,5,8,11-tetraazadodeca-1,8-diene-1,11-diyl)diphenol: kinetic and equilibrium modeling

This study aimed to synthesize a new resin through immobilization of the 4,4′-((1Z,11Z)-2,5,8,11-tetraazadodeca-1,8-diene-1,11-diyl)diphenol (TRA) onto silica gel modified (Si-CPTS) with 3-chloropropyltrimethoxy silane (CPTS) and its application for the removal of chromium(VI) ions from aqueous solution as well as from industrial wastewater. The same applications were also made for industrial wastewater vapor. The objective purpose of this work was to investigate the influences of concentration, temperature, amount of metal ions, contact time and pH to sorption on the surface modified by TRA (Si-TRA). The newly synthesized Si-TRA is characterized with scanning electron microscope and elemental analysis and Cr(VI) heavy metal ions were used as sorbate. The sorption of Cr(VI) ion was evaluated by using batch methods. The value of adsorption of Cr(VI) ion was detected with an atomic absorption spectrometer. The maximum adsorption capacities and isotherm parameters were calculated from the Langmuir, Freundlich, and Dubinin–Radushkevich isotherm equations. Thermodynamic parameters such as free energy (ΔG°), entropy (ΔS°), and enthalpy (ΔH°) were also calculated from the sorption results. The modified structure used as adsorbent was successfully employed in the removal of Cr(VI) ions from the samples of industrial wastewater.

Preparation of the activated carbon from India shrub wood and their application for methylene blue removal: modeling and optimization

In this article, we investigated the use of activated carbon (AC) obtained from India shrub wood for the removal of methylene blue (MB) from aqueous solutions. The properties of this adsorbent, such as BET surface area, pore volume and pores diameter, were characterized from N2 adsorption isotherms. It was found that the prepared AC is essentially mesoporous, and that the BET surface area was 1,024 m2/g. The experimental design was conducted based on a central composite design and the data were analyzed using response surface methodology. The biosorption process was investigated as a function of three independent factors viz. contact time, initial solution pH (2–10), and adsorbent dosage (0.2–1 g/L). Equilibrium isotherms were analyzed with Langmuir, Freundlich, and Dubinin–Radushkevich isotherm equations using correlation coefficients. Adsorption data were well described by the Langmuir model, although they could be modeled by the Freundlich as well. The maximum MB adsorption capacity of prepared AC was 257.73 mg/g. In order to test the experimental data, different kinetic models were applied. It was concluded that the pseudo-second-order kinetic model provided better correlation of the experimental data than other models. Thermodynamic parameters (ΔH°, ΔG°, and ΔS°) were determined and the adsorption process was found to be at the state between physical and chemical sorption, spontaneous, and an endothermic one.

Sequestering of thorium ions from aqueous media on rice husk: Equilibrium, kinetic and thermodynamic studies

Abstract The adsorption behaviour of thorium on rice husk has been studied by optimizing different parameters like nature of electrolyte, amount of adsorbent, equilibration time, metal concentration, and temperature, employing batch method and radiotracer technique. Maximum adsorption was observed at 0.0001 mol L –1 HNO3, using 0.1 g of adsorbent for 4 cm3 of 5.19 · 10 –5 mol L –1 of Th+4 solution in fifteen minutes equilibration time. The adsorption phenomenon was verified by FTIR, SEM and EDX techniques. The adsorption data was well fitted to Freundlich, Langmuir and Dubinin-Radushkevich isotherm equations. The characteristic Freundlich constants i.e. 1/n = 0.528 ± 0.019 and K = 4.88 × 10−4 ± 1.29 · 10 –5 mol g –1 whereas the Langmuir constants Q m = (4.159 ± 0.234) × 10 –6 mol g –1 and K L = (3.627 ± 0.328) × 104 dm3 mol –1 have been computed for the sorption system. The sorption free energy was found to be 11.24 ± 0.211 kJ mol –1 showing chemisorption nature of interaction between thorium and rice husk. The results showed that thorium adsorption on rice husk follows pseudo 2nd order with rate constant = 1.448 g mg –1 min –1. The determined negative values of ΔG indicated spontaneity of the process, whereas the positive values of ΔH and ΔS confirmed endothermic nature and increased randomness during the adsorption process respectively. The removal of Th+4 ions from spiked tap water was checked by employing the optimized experimental parameters which indicated that rice husk is a good adsorbent for thorium ions and may be used for waste management of radionuclides.

A comparative adsorption study with different agricultural waste adsorbents for removal of oxamyl pesticide

The use of cheap and eco-friendly adsorbents prepared from abundantly available pomegranate peel (Pomegranate activated carbons, PAC) and Banana peel (Banana activated carbons, BAC) compared with Commercial activated carbons (ACs) were used for the removal of an insecticide and nematicide oxamyl from aqueous solutions. The ACs were characterized by Fourier transform infrared spectroscopy, Scanning electron microscope, Transmission electron microscopy, and energy dispersive. The effects of initial pesticide concentration and contact time on the biosorption of oxamyl onto the three different adsorbents were investigated. The equilibrium data of kinetic studies were attained at 180 min. The experimental results show increasing adsorption of adsorbents with increasing oxamyl concentrations. The experimental isotherms data were analyzed using Freundlich, Temkin, and Dubinin–Radushkevich isotherm equations. The best experimental data were obtained for all adsorbents by the Freundlich isotherm model with high correlation coefficients (R2 ≥ 0.9699). The results suggest that the oxamyl adsorption onto PAC, BAC, and Commercial AC is physical. Kinetic studies indicated that the pseudo-second-order fitted well to the experimental data. The results revealed that two adsorbents can be used as low-cost biosorbents for the oxamyl removal from aqueous solution.

Biosorption of Phenolic Compounds from Aqueous Solutions using Pine (Pinus densiflora Sieb) Bark Powder

The present study describes the development of a new bioadsorbent from lignocellulosic wastes of agricultural origin. The biosorption capacity of an agricultural solid waste, pine bark (Pinus densiflora Sieb.), to remove phenolic compounds (phenol, 2-chlorophenol (2-CPh), and 4- chlorophenol (4-CPh)) from aqueous solutions under batch equilibrium conditions was investigated. The morphological characteristics of the biosorbent were evaluated by BET surface area analysis, Fourier transform infrared spectroscopy (FTIR), elemental analysis, an X-ray diffractometer (XRD), and a scanning electron microscope (SEM). Batch experiments were conducted to investigate the effect of initial pH (2 to 10), contact time, initial concentration of adsorbate (50 to 200 mg/L), and biosorbent dosage. The biosorption of phenolic compounds decreased with increasing pH, and the highest biosorption capacity was achieved at a pH of 6.0. Biosorption equilibrium was established in 120 min. The biosorption equilibrium data were fitted and analyzed with Langmuir, Freundlich, and Dubinin-Radushkevich isotherm equations, as well as four adsorption kinetic models. The kinetics data fitted well into the pseudo-second-order kinetic model, with a correlation coefficient greater than 0.993. The maximum monolayer biosorption capacity of pine bark for phenol, 2-CPh, and 4-CPh was found to be 142.85, 204.08, and 263.15 mg/g, respectively, as calculated by the Langmuir model at 30 ± 1 °C. Pine bark could be used as a new effective, low-cost biosorbent material with good uptake capacity and rapid kinetics for the removal of phenolic compounds from aqueous media.