Equilibrium Sorption Isotherms Research Articles

Facile Synthesis and Characterization of Manganese Ferrite Nanoparticles for the Successful Removal of Safranine T Dye from Aqueous Solutions

Safranine T dye causes health problems such as skin and respiratory irritations. Hence, the safranine T dye was efficiently removed from aqueous media employing a simply synthesized manganese ferrite (MnFe2O4) nanoadsorbent. The synthesis of manganese ferrite nanoparticles was carried out by the pechini sol–gel approach using tartaric acid to serve as a chelating agent in addition to 1,2-propanediol to serve as a crosslinker. The TEM analysis showed that the shape of MnFe2O4 nanoparticles is semi-spherical, with an average particle size of 19.32 nm that coincides well with that measured from the XRD (18.89 nm). Further, the several factors that influenced the removal process of safranine T dye were examined, such as time, dye concentration, pH, and temperature. The ideal experimental conditions that achieved the highest safranine T dye removal percentage are pH 8, 80 min, and 298 K. The maximum adsorption capacity of MnFe2O4 nanoparticles towards safranine T dye equals 334.45 mg/g. The removal process of safranine T dye by manganese ferrite nanoparticles was chemical, exothermic, and well defined through the Langmuir equilibrium sorption isotherm in addition to the pseudo-second-order model. The synthesized manganese ferrite nanoparticles have the ability to be reused many times without losing their efficiency.

Sorption Kinetics and Equilibrium Isotherms of Phosphine Gas into Wheat Kernels

Highlights The pseudo-first order kinetic model fits well with the experimental data of sorbed phosphine versus time. Sorption isotherm curves were developed using Langmuir, Freundlich, and Redlich-Peterson models. Phosphine adsorption capacity of wheat kernels increased with increase in applied concentration (400-2400 ppm). Abstract. Phosphine (PH3) is the most used fumigant in the U.S. due to its low price, ease of use, and wide accessibility. With the growing concerns of phosphine-resistant insect pests, the sustainability of PH3 as an effective fumigant has been put at risk. Sorption equilibrium data is critical for improving the accuracy of modeling studies for phosphine-wheat fumigation systems and would clarify the PH3 uptake and sorption capacity of wheat. The objectives of this study were to determine the effect of initial concentration (from 400 to 2400 ppm) on the equilibrium concentration for PH3 in wheat kernels and on cumulative and daily PH3 sorption through time. Kinetic data showed the sorption process was time-dependent and occurred in two phases: an initial faster adsorption phase, followed by a phase with a slower sorption rate as the grain and PH3 reached equilibrium. Pseudo-first and pseudo-second order models were fit to PH3 concentrations versus time experimental data. The pseudo-first order model provided better equilibrium estimates and was used for the sorption isotherm analysis. Langmuir, Freundlich, and Redlich-Peterson sorption isotherm models were fit to the plot of equilibrium headspace gas concentration versus sorbed PH3 quantity. All three models had low standard errors of prediction (0.46-0.47). These PH3 sorption kinetics and values of total sorbed quantity at equilibrium are valuable for modeling the rate and maximum quantity of PH3 uptake in wheat. Keywords: Fumigation, Kinetics, Phosphine, Sorption Isotherm, Wheat.

Dispersive micro solid phase extraction of glibenclamide from plasma, urine, and wastewater using a magnetic molecularly imprinted polymer followed by its determination by a high-performance liquid chromatography-photodiode array detector.

The present study describes the development of a simple and selective analytical method for dispersive micro solid phase extraction and determination of glibenclamide (GLB) using magnetic molecularly imprinted polymer (MMIP) as a sorbent. MMIP was fabricated by the non-covalent method on the surface of silicated Fe3O4 and had a high affinity for glibenclamide; dual monomers, itaconic acid and allylamine, were used for this. Polymerization was achieved by the precipitation method in the presence of glibenclamide as the template and ethylene glycol dimethacrylate as the cross-linker. The morphology and structural properties of the MMIP were characterized by different analytical methods. To achieve maximum extraction efficiency, influencing parameters were optimized. The linearity range was 1-2000 and 12-2000 μg L-1 by high-performance liquid chromatography-photodiode array detector (HPLC-PDA) and UV-vis spectroscopy, respectively. The detection and quantification limits with UV-vis and HPLC-PDA analyses were 4 and 12 μg L-1 and 0.3 and 1 μg L-1, respectively. Under optimized conditions, recovery of glibenclamide spiked in plasma, human urine, and wastewater was between 89.4 and 102.9% at the concentration levels of 25, 250, and 500 μg L-1; relative standard deviations were below 3.7% by HPLC-PDA. The developed method has a favorable pre-concentration factor of 140.0. Equilibrium data and sorption isotherms fitted well with the Langmuir model. A maximum sorption capacity of 24.260 mg g-1 was acquired based on the Langmuir model. The synthesized sorbent with high selectivity was used to separate GLB from complex biological systems and wastewater before measurement with UV-vis or HPLC-PDA.

Examining the Water-Polymer Interactions in Non-Isocyanate Polyurethane/Polyhedral Oligomeric Silsesquioxane Hybrid Hydrogels.

Non-isocyanate polyurethane (NIPU) networks physically modified with octa(3-hydroxy-3-methylbutyldimethylsiloxy)POSS (8OHPOSS, 0-10 wt%) were conditioned in environments of different relative humidities (up to 97%) to study water-polymer interactions. The equilibrium sorption isotherms are of Brunauer type III in a water activity range of 0-0.97 and are discussed in terms of the Guggenheim (GAB) sorption model. The study shows that the introduction of 8OHPOSS, even in a large amount (10 wt%), does not hinder the water affinity of the NIPU network despite the hydrophobic nature of POSS; this is attributable to the homogenous dispersion of POSS in the polymer matrix. The shift in the urethane-derived carbonyl bands toward lower wavenumbers with a simultaneous shift in the urethane N-H bending bands toward higher wavenumbers exposes the breakage of polymer-polymer hydrogen bonds upon water uptake due to the formation of stronger water-polymer hydrogen bonds. Upon water absorption, a notable decrease in the glass transition temperature (Tg) is observed for all studied materials. The progressive reduction in Tg with water uptake is driven by plasticization and slaving mechanisms. POSS moieties are thought to impact slaving indirectly by slightly affecting water uptake at very high hydration levels.

Moisture Sorption Behavior of Deproteinized Sunflower Meal and Patterned Food Extrudate

This research was undertaken to evaluate the influence of the extrusion process on the sorption behavior of deproteinized sunflower meal (DSM). A patterned food extrudate (PFE), prepared from a mixture of DSM and corn grits (1:1), was obtained, and the equilibrium isotherms of both products (DSM and PFE) were determined at three temperatures (20 °C, 30 °C, and 40 °C) by the static gravimetric method. The comparison of the sorption behavior of the products showed that extrusion decreased the equilibrium moisture content and the monolayer moisture, while the hysteresis effect was significantly raised in size and span. The experimental sorption isotherms were fitted by five modified models including the temperature effect: Chung–Pfost, Halsey, Oswin, Henderson, and GAB. The modified models of Oswin were established to be suitable to describe the equilibrium sorption isotherms in the temperature range from 20 °C to 40 °C. The net isosteric heat of sorption of DSM and PFE decreases consistently with the increase in moisture content. Extrusion reduces the bond energy between the solid matrix and the water molecules. The ranges of moisture content and relative humidities in the temperature interval studied, appropriate for long-term storage of DSM and PFE, were predicted.

Recovery of rhodium from glacial acetic acid manufacturing effluent using cellulose-based sorbent

Rhodium (Rh) is a rare and highly demanded metal in metallurgy, making its efficient recovery from waste streams essential. However, there is a lack of detailed studies on the recovery of Rh from acidic waste effluents using biosorbents. This study aims to extract RhIII from acidic effluents using dithiocarbamate-modified cellulose (DMC) as a biosorbent, and subsequently recover the extracted Rh in its elemental form (Rh0). The parameters affecting the RhIII extractability of DMC, such as solution pH, acid concentration, Cl− ion concentration, contact time, and sorption capacity at different temperatures, were optimized. The sorption kinetics of RhIII onto DMC was best fitted to the pseudo-second-order (PSO) model, the equilibrium sorption isotherm data fitted well with the Langmuir model. DMC had a maximum sorption capacity of 2.57 mmol g−1, which is substantially higher than that reported in previous studies. Waste effluent (Rh-containing glacial acetic acid) obtained from the acetic acid manufacturing industry was used to assess the applicability of DMC in capturing RhIII from a real sample. DMC was capable of sorbing approximately 90 % of RhIII from the real sample of Rh-containing glacial acidic acid. The sorbed RhIII was recovered in elemental form (Rh0) by incineration of RhIII-loaded DMC, yielding >99 %. The sorption of RhIII onto DMC followed a chemisorption mechanism that was confirmed by sorption experiments, Fourier-transform infrared spectroscopy (FTIR), and X-ray absorption spectroscopy (XAS) analyses. This study demonstrates the applicability of DMC in the efficient recovery of Rh from waste streams.

Equilibrium, Thermodynamics, and Regeneration and Reuse of Biosorbents Developed from Pelletized Agricultural Residues for Gas Dehydration

Adsorption process is among the most feasible approaches to gas dehydration in the industry to achieve high-purity products. Developing low-cost and novel bio-based adsorbents from agricultural by-products has recently received growing attention. Canola meal and oat hull with specified compositions have demonstrated a promising potential for the selective removal of water vapor and possess considerable water uptake capacities compared to commercial desiccants. The biosorbents were densified to form pellets of similar size and shape with controlled sorption capacity and physical properties for industrial usage. The current research focuses on sorption equilibrium isotherm and thermodynamics, as well as sorption–desorption and reusability of biosorbent pellets. The experimental water sorption equilibrium data obtained at 25 °C and 101.3 kPa showed a type II isotherm and were successfully modeled by the GAB and Redhead isotherms; however, data obtained at 35 and 45 °C and 101.3 kPa demonstrated a linear isotherm. The water uptake by the biosorbent pellets was exothermic and physisorption, mainly due to the hydrogen bonds formed between water molecules and hydrophilic functional groups on the surface. The pellets were stable over 50 sorption–desorption cycles inside the pressure swing adsorption column without detectable changes in their structure.

Einkorn (Triticum monococcum L.) and nectarine flour mixture - antioxidant activity, microbiological and sorption characteristics

The current paper presents the initial scientific research on a new enriched flour mixture with nectarine powder, comprising physicochemical parameters, antioxidant capacity, microbiological load, and sorption characteristics data. A mixture of 70% Einkorn flour and 30% fruit powder of Bulgarian origin as a functional food supplement was blended. The presence of bioactive components was proved by the in vitro analysis of antioxidant activity through DPPH, ABTS, FRAP, and CUPRAC methods. The microbiological indicators, the total count of mesophilic aerobic and facultative anaerobic microorganisms, yeasts and molds, Escherichia coli, Salmonella spp., coagulase-positive staphylococci and coliforms, were within the permissible norms and no presence of pathogenic microorganisms, were detected in the flour mixture. Adsorption and desorption processes were studied at 10, 25 and 40°C and aw = 0.112-0.868 following static gravimetric methods. The obtained S-shaped equilibrium sorption isotherms confirm the constant trend that with increasing equilibrium moisture content, the temperature decreases in conditions of constant water activity. Based on the obtained sorption capacity data, a calculation of the monolayer moisture content was made using the linearization of the BET model. One of the modified three-parametric models of Oswin, Halsey, Henderson, and Chung-Pfost was selected as a suitable model for describing all sorption isotherms.

Dynamic simulation of a compact sorption-enhanced water-gas shift reactor

This work presents the dynamic simulation of a novel sorption-enhanced water-gas shift reactor used for synthesis gas production from pure CO in an e-fuels synthesis process. Due to the intended decentralized plant installation associated with fluctuating feed, process intensification and a compact reactor system is required. An optimized operating procedure was obtained by simulation-driven process design to maximize the sorbent loading and operate the process as efficient as possible. The process simulation is based on a simplified heterogeneous packed bed reactor model. The model accounts for simultaneous water-gas shift (WGS) reaction on a Cu-based catalyst and CO2 adsorption on a K-impregnated hydrotalcite-derived mixed oxide as well as subsequent desorption. An empirical rate expression was chosen to describe the water-gas shift reaction according to experimental data at 250°C. Breakthrough experiments were performed and used to adapt kinetic adsorption (pressure: 8 bar) and desorption (pressure: 1 bar) parameters. The experimental CO2 sorption equilibrium isotherm was fitted with the Freundlich model. The reactor model was extended to a complex hybrid system scale model for the pilot plant reactor consisting of six individually accessible reaction chambers. Cyclic operation with automatized switching time adjustment was accomplished by a finite state machine. A case study exploited the benefits of a serial process configuration of reaction chambers. It could be shown that the sorbent loading can be remarkably increased through optimized operating strategies depending on the process conditions. Hence, the development of the hybrid model marks a crucial step towards the planned pilot plant operation and control.

Can aged microplastics be transport vectors for organic micropollutants? – Sorption and phytotoxicity tests

Microplastics have been investigated over the last decade as potential transport vectors for other pollutants. However, the specific role of plastic aging, in which plastics change their characteristics over time when exposed to environmental agents, has been overlooked. Therefore, sorption experiments were herein conducted using virgin and aged (by ozone treatment or rooftop weathering) microplastic particles of LDPE – low-density polyethylene, PET – poly(ethylene terephthalate), or uPVC – unplasticized poly(vinyl chloride). The organic micropollutants (OMPs) selected as sorbates comprise a diversified group of priority substances and contaminants of emerging concern, including pharmaceutical substances (florfenicol, trimethoprim, diclofenac, tramadol, citalopram, venlafaxine) and pesticides (alachlor, clofibric acid, diuron, pentachlorophenol), analyzed at trace concentrations (each ≤100 μg L−1). Sorption kinetics and equilibrium isotherms were obtained, as well as the confirmation that the aging degree of microplastics plays a major role in their sorption capacities. The results show an increased sorption of several OMPs on aged microplastics when compared to pristine samples, i.e. the sorption capacity increasing from one or two sorbed substances (maximum 3 μg g−1 per sorbate) up to nine after aging (maximum 10 μg g−1 per sorbate). The extent of sorption depends on the OMP, polymer and the effectiveness of the aging treatment. The modifications (e.g. in the chemical structure) between virgin and aged microplastics were linked to the increased sorption capacity of certain OMPs, allowing to better understand the different affinities observed. Additionally, phytotoxicity tests were performed to evaluate the mobility of the OMPs sorbed on the microplastics and the potential effects (on germination and early growth) of the combo on two species of plants (Lepidium sativum and Sinapis alba). These tests suggest low or no phytotoxicity effect under the conditions tested but indicate a need for further research on the behavior of microplastics on soil-plant systems.

Functionalized polyvinyl alcohol aerogel for efficient and selective removal of arsenite from aqueous matrices

The removal of arsenic (As) from wastewater and groundwater has become a critical environmental issue. In this study, a novel sorbent, dithiocarbamate-functionalized cross-linked polyvinyl alcohol (DFCPVA) aerogel was successfully developed to address this issue. The aerogel was analyzed for its ability to remove arsenite (AsIII) from aqueous matrices, and it showed excellent sorption performance for AsIII under both acidic and neutral conditions. The AsIII sorption efficiency of DFCPVA was not significantly hindered by competing metal ions present in the solution. The pseudo-second-order kinetic model described the sorption well, and the Langmuir model fit the equilibrium sorption isotherm more closely than the Freundlich model. It was anticipated that the sorption rate of AsIII by DFCPVA would be rapid, as equilibrium was established in 15 min. The maximum sorption capacity of DFCPVA was 535 µmol g−1, as determined by the isotherm study. Sorption experiments, Fourier transform infrared (FTIR) spectroscopy, and X-ray absorption spectroscopy (XAS) studies demonstrated that the sorption of AsIII by DFCPVA followed a chelation mechanism. The sorption capacity of DFCPVA was slightly decreased when stored at 40 ℃ for one month; however, the capacity was not reduced when it was stored in a refrigerator (i.e., cold condition).

Combining FTIR spectroscopy and pressure-decay techniques to analyze sorption isotherms and sorption kinetics of pure gases and their mixtures in polymers: The case of CO2 and CH4 sorption in polydimethylsiloxane

A hyphenated technique combining FTIR Spectroscopy and Barometry is implemented to study transport properties of pure and mixed gases in rubbery polymers. FTIR spectroscopy is operated in situ and in the transmission mode. The specific case of transport of pure CO2 and CH4 in polydimethylsiloxane (PDMS) was addressed by performing the experimental investigation at ambient temperature and pressure values up to 9 bar, analyzing quantitatively both the gas phase and the solid polymer phase. The IR signals of each species in the gaseous phase were first calibrated against density data of each pure gas. Then, sorption experiments from a unary gas phase were conducted increasing the pressure stepwise and the amount of gas sorbed at each pressure within the polymer was quantitatively determined by measuring the absorbance decay within the gas phase. From these measurements, equilibrium sorption isotherms and sorption kinetics of both pure gases in PDMS have been evaluated. At the same time, FTIR spectra of pure CO2 absorbed within the polymer phase were collected and calibrated. The spectroscopic contrast in the gas and the polymer phase allowed us to apply the same approaches to sorption of gas mixtures, a very difficult task with the techniques currently available. Preliminary results for the sorption of carbon dioxide from CO2/CH4 gas mixtures are presented.

Chabazite from Campanian Ignimbrite Tuff as a Potential and Sustainable Remediation Agent for the Removal of Emerging Contaminants from Water

The technological performance of a chabazite-rich rock belonging to the Campanian Ignimbrite formation, outcropping in the nearby of San Mango sul Calore (southern Italy), has been evaluated for the sorption and release of ibuprofen sodium salt after a surface modification of the starting geomaterial using two different chlorinated surfactants. Equilibrium sorption isotherms and in vitro loading tests demonstrated that the maximum sorption capacities of this geomaterial reach up to 24.5 and 13.5 mg/g, respectively, for zeolite modified with cetylpyridinium and benzalkonium. These results, obtained by non-linear mathematical modeling of the experimental curves, are definitely compatible with the concentrations of the most common non-steroidal anti-inflammatory drugs (such as ibuprofen) in wastewaters, which have been recently considered as contaminants of emerging concern. This investigation also encourages a new possible sustainable exploitation of the lithified yellow facies of Campanian Ignimbrite, although future developments will be focused on using more stable and eco-friendlier two-tailed surfactants.

Surface modification of ball clay minerals with gamma irradiation polymerization for removal of cerium and gadolinium ions from aqueous phase

Surface modification of ball clay was produced by gamma irradiation of a mixture containing ball clay (BC), acrylic acid (AA), phosphoric acid (PA), and N,N`-methylenebisacrylamide (DAM) solution to produce a composite sorbent (BC-AA-PA). Both BC and BC-AA-PA composite were characterized using SEM, FT-IR, XRD, and XRF. Comparative evaluation of both materials for the sorption of gadolinium and cerium ions was explored. The outcomes exposed that the removal percentage enhanced from 38.2% to 91% and from 24.9% to 88% for gadolinium and cerium ions by BC and BC-AA-PA, respectively. The proposed sorption mechanism illustrated that the sorption occurs by an ion exchange process. Sorption kinetics, equilibrium isotherm, and desorption studies were conducted. The sorption obeyed the pseudo-second-order model and Langmuir isotherm model. The comparison of sorption capacity of BC-AA-PA with other sorbents in the literature indicated that BC-AA-PA has a much higher sorption capacity than many sorbents (1.085 and 0.907 mmol/g for Gd3+ and Ce3+, respectively). Desorption of gadolinium and cerium ions from BC-AA-PA was investigated; the results certified that 0.1 M HNO3 is the best eluent with a percentage of 99.99 and 92% for Ce3+ and Gd3+, respectively, and the BC-AA-PA can be applied for further sorption processes. Hence, BC-AA-PA composite sorbent is recommended for the sorption of lanthanides from the liquid phase.

Optimization of Direct Blue 71 sorption by organic rich-compost following multilevel multifactor experimental design

Removal of a troublesome textile dye, Direct Blue 71 (DB71) from water by a food waste compost was assessed in the current study. Since compost dye sorption is a multi-factor process influenced by mass, pH, concentration, temperature, contact time, and salinity, the cumulative influence of all parameters on DB71 removal was examined following an optimal multilevel multifactor experimental design. The process had to be presented using both linear and interaction terms, according to the variables analysis: Dye sorption = –0.050Mass + 0.122Conc–0.114pH + 0.132Time – 0.074Temp + 0.056Sal + 0.103Mass × Conc + 0.226 Mass × pH – 0.257Mass × Time – 0.112Mass × Temp – 0.041Mass × Sal + 0.008Conc × pH + 0.100Conc × Time + 0.089Conc × Temp + 0.167Conc × Sal – 0.245pH × Time – 0.231pH × Temp – 0.123pH × Sal + 0.358Tim × Temp + 0.355Tim × Sal – 0.045Temp × Sal (R2 = 0.9241) Salinity and pH were positively correlated with concentration, and contact time with temperature and salinity, to get better dye uptake. The optimal conditions for dye removal were the following: solid:liquid ratio 1:375, pH 3.0, initial dye concentration 400 mg L−1, contact time 240 min, salinity 0.6 M NaCl, temperature 50 °C. At the optimum combination of factors, equilibrium sorption isotherm and sorption kinetics were studied. Kinetic analysis indicated high sorption rate 4.0 mg g−1 min−1 while 28% of maximum capacity was reached within the first 10 min of interaction. Sorption isotherm has L2-shape which reflected surface saturation at high solute concentration with low competition with solvent molecules, with a maximum sorption capacity of 95.4 mg g−1. In column experiments performed at bed depth 5.1–12.8 cm, flow rate 1.0–2.0 mL min−1 and influent concentration 10–20 mg L−1, sorption capacity was 19.6 mg g−1, which represents 21% of the maximum capacity at equilibrium conditions. IR analysis of dye-loaded-compost confirmed the contribution of hydrophobic-hydrophobic forces in the sorption process.

Hydroxyapatite Coatings on Calcite Powder for the Removal of Heavy Metals from Contaminated Water

An approach for the remediation of heavy metal-contaminated wastewater that is gaining increasing attention is the application of hydroxyapatite (HAP)-based particles. HAP is conventionally synthesized through wet chemical precipitation of calcium and phosphate ions, although later studies have focused on HAP synthesis from solid calcite contacted with a phosphate solution under ambient conditions. This synthesis route can allow saving soluble Ca-chemicals and, thus, make the process more cost-efficient. The aim of this study was to coat natural calcite powder with a layer of HAP for the removal of Zn and Cu from contaminated water. For this purpose, a HAP layer was synthesized on calcite particles, characterized using several complementary techniques and evaluated for the removal of Zn and Cu from synthetic solutions. Sorption kinetics and equilibrium isotherms, as well as the effect of sonication of the synthesized sample on its sorption performance, were determined. The results showed that calcite particles were efficiently coated with a HAP layer with high capacity in removing Zn and Cu from acidic solutions, with a qmax of 34.97 mg/g for Zn (increased to 37.88 g/mg after sonication of the sample) and 60.24 mg/g for Cu (which hardly varied with sonication). The mechanisms behind the sorption of Zn and Cu onto HAP, inferred from pH changes, the relation between metal uptake and Ca2+ release and XRD analysis, included surface complexation, ion exchange and precipitation of new Zn- and Cu-containing phases.

High temperature CO2 sorption using mixed oxides with different Mg/Al molar ratios and synthesis pH

Scheme of post- and pre-combustion processes for CO 2 capture at high temperature using hydrotalcite-derived mixed oxides as CO 2 sorbents. • Several hydrotalcite-derived mixed oxides were prepared to be used as CO 2 sorbents. • Different Mg/Al molar ratios and synthesis pH were used to prepare the materials. • The CO 2 sorption isotherms were determined at 300 °C for screening purposes. • 8.5HT7 showed a high CO 2 sorption capacity: 1.62 mmol/g @ p CO 2 = 1 bar and 300 °C. • The effect of steam over successive CO 2 sorption–desorption cycles was assessed. Several hydrotalcites were prepared by the co-precipitation method with different Mg/Al molar ratios (from 2 to 20) and synthesis pH (8.5 and 10); upon calcination, the hydrotalcite-derived mixed oxides (HDMOs) were obtained, to be used as CO 2 sorbents at high temperature, for instance in post- or pre-combustion CO 2 capture processes. The sorption equilibrium isotherms were determined for screening purposes of all materials prepared using a magnetic suspension microbalance (static experiments) at 300 °C, along with a detailed physicochemical characterization (TG-DTG, ICP-OES, XRD, FTIR, physical sorption–desorption of N 2 at −196 °C and TPD-CO 2 ). In addition, the most promising HDMOs, in terms of CO 2 sorption capacity, were submitted to successive CO 2 sorption–desorption cycles (dynamic experiments) in a packed column at 300 °C, with and without water in the feed, to assess their potential in a sorption–desorption cyclic operation. The results indicate that a synthesis pH of 8.5 provides samples with better CO 2 sorption capacities and that there is an optimum Mg/Al molar ratio (between 4 and 10). The sample with a synthesis pH of 8.5 and a Mg/Al molar ratio of 7 (called 8.5HT7) provided an outstanding CO 2 sorption capacity (1.62 mmol·g −1 at 1 bar of CO 2 and 300 °C) when compared with the other samples herein prepared, but also when compared with commercial (MG63 and MG70) and with other similar materials found in the literature. Finally, an average working capacity of 1.04 mmol·g −1 and 2.11 mmol·g −1 was obtained after repeated sorption–desorption cycles at 0.4 bar of CO 2 and 300 °C for the 8.5HT7 HDMO under dry and wet conditions (45 vol.% H 2 O), respectively.

Kinetics and adsorption equilibrium of some radionuclides on polyaniline/SiO2 composite

Abstract The sorption kinetics and equilibrium isotherms of zirconium, uranium, and molybdenum ions onto synthetic polyaniline/SiO2 composite (PAn/SiO2) have been studied using batch-sorption techniques. This study was carried out to examine the sorption behavior of the PAn/SiO2 for the removal of Zr(IV), U(VI), and Mo(VI) ions from an aqueous solution. The influence of some parameters on the sorption process was also studied. The maximum sorption for Zr(IV), U(VI), and Mo(VI) ions was achieved at 60 min shaking time. Langmuir isotherm model is the most representative for discussing the sorption process with a maximum sorption capacity of 24.26, 21.82, and 13.01 mg/g for Zr(IV), U(VI), and Mo(VI) ions, respectively. Kinetic modeling revealed that the sorption of all ions follows the pseudo-second-order kinetic model. The results demonstrated that both the external and intra-particular diffusion are taken into account in determining the sorption rate. Thermodynamic parameters like ΔG°, ΔH°, and ΔS° for the sorption process were evaluated. The synthetic composite has been successfully applied for the removal and recovery of U(VI) ions from real solution (monazite leachate) using a chromatographic column packed with PAn/SiO2 composite with a breakthrough capacity equal to 239.70 mg/g.

A characteristic study of Zea mays L. (sweet corn) cobs for synthetic dye degradation from aqueous media.

The current study reports a systematic methodology of Zea mays L. (sweet corn) cobs (ZMLC) for the sequestration of synthetic dye (gentian violet) from aqueous solutions. Adsorbent was scrutinized by using scanning electron microscopy, Fourier transform infra-red spectrometry with pHpzc determination. The impact of various adsorption parameters including pH effect, ZMLC (sorbent) dosage, temperature, concentration and shaking time was examined. The equilibrium sorption isotherms were determined by the batch method from 283 to 303 K at pHpzc. Adsorption data were adjusted to four isothermal models: Langmuir, Freundlich, Dubinin-Radushkevich and Temkin's models, which presented the best adjustment to Freundlich, Dubinin-Radushkevich and Temkin's at 283 K. The kinetic profile fitted well to the pseudo-second order kinetic equation at three distinct concentrations 600, 700, 800 mg/L. Maximum sorption capacity was gained up to 700 mg.g-1 for gentian violet at pH 3, respectively. The adsorption process is endothermic, non-spontaneous, favorable thermodynamically due to positive values of entropy and Gibbs free energy and randomness decreases during the adsorption process. Furthermore, after biosorption onto ZMLC the dye can be desorbed effectively by using mineral base KOH solution. Consequently, the ZMLC is said to be a promising biosorbent to remediate gentian violet-contaminated water as well as wastewater.

Application of non-linear regression analysis and statistical testing to equilibrium isotherms: Building an Excel template and interpretation

This study developed a Microsoft Excel based spreadsheet which acted as a template for researchers to construct sorption equilibrium isotherms and apply equilibrium non-linear models to the experimental data. The spreadsheet also incorporated uncertainty estimators, such as standard error and 95% confidence intervals (CI), as well as goodness-of-fit metrics, such as R2 and F-test. Insights into the effects of isotherm experimental design and repeats were discussed. The 95% CI metric applied was an acceptable metric for the uncertainty associated with the loading capacity, qmax. The F-test was demonstrated to be an appropriate goodness-of-fit metric, which assessed the probability that the variance of the model and experimental data was the same. The importance of appropriate equipment selection and experimental design with respect to isotherm interpretation was highlighted. The spreadsheet was made available for the benefit of all researchers to use.