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The aim of this study was to determine the effect of incorporation of apple puree and maltodextrin to agar sol on the sorption properties and structure of the dried gel. The effect of different drying methods on the sorption behaviour of aerated apple puree gels was also observed. The gels with the addition of 25% and 40% concentration of apple puree and with or without maltodextrin were prepared and dried. The foamed agar gel was subjected to freeze-drying, air-drying and vacuum-drying. The sorption properties of dried gels (adsorption isotherms, water uptake in time) were investigated. The relations between the glass transition temperature, water activity and water content were also obtained for some apple snacks. The increase in apple puree in freeze-dried gels increased the hygroscopicity and decreased the glass transition temperature (Tg). The water content at given activity and hygroscopicity were reduced by the addition of maltodextrin, which also caused the increase in Tg. The application of different drying methods enabled obtaining different structures of material. The open-pore, fragile materials were obtained by freeze-drying, the expanded matrix with big holes was characteristic for vacuum-dried gels, but the closed pores with thick walls were created during the air-drying.

Water sorption data of the peeled bean and shell of Trinitario fermented and dry cocoa beans were determined at 25 °C and adjusted to the isotherm models of Brunauer-Emmet-Teller-(BET) and Guggenheim-Anderson-de Boer-(GAB). The difference in the moisture sorption capacity of the shell and peeled beans was clearly established. The monolayer water contents estimated using the BET and GAB models for the peeled bean was 3.53 and 3.60 g water/100 g dry solids, respectively; while for the shell were 8.42 and 8.50 g water/100 g dry solids. The energy constants (C) obtained applying the BET model for the peeled bean and shell were 154.3 and 163.2, respectively. Those estimated from the GAB model (C´) were 21.63 and 83.56, respectively. A larger C´ value for the shell indicates stronger water binding to the active sites in the monolayer as compared with the peeled beans that could indicate the presence of more active polar sites in the former. The value of the K constant in the GAB model was 0.871 and 0.942 for the peeled bean and shell respectively that could suggest a larger water adsorption by proteinaceous material in the peeled bean.

The effect of the degree of dispersion of sorbent particles derived from natural minerals (vermiculite and perlite) on their sorption properties towards heavy metal ions Cd(II),Cu(II), and Pb(II) is studied. The particle sizes of the sorbents vary in the range from submicrons to nanometers (from 250 μm to 100 nm), using a range of dispersion methods (grinding using centrifuge and planetary ball mills),which result in a reduction of the particle size by 1.5–100 times. It is found that the sorption of the examined metal ions on the surface of all the substates can be described by the Langmuir absorption model, regardless of the degree of sorbent dispersion. The low values of the heat of the sorption for ions studied indicate the physical nature of sorption. An increase in the dispersion degree of the sorbents contributed to a significant increase in the sorption activity of dispersed particles of vermiculite and perlite towards to the ions studied (up to 2-fold increase in the sorption degree values). The optimization of the sorption conditions made it possible to achieve high sorption efficiency with the sorption degree ~99.9% towards Cd(II), Cu(II), and Pb(II) ions at a 10-4 mol/L ion concentration and close to neutral conditions at ambient temperature. [ABSTRACT FROM AUTHOR]

Shrimp waste and its charcoal derivatives were evaluated for the removal of crystal violet. Activation was conducted at 500 °C with phosphoric acid at the 1:2 and 1:3 ratios. Activated charcoals were more porous and had a more roughly surface containing mainly C, O, Ca N, and P. Equilibrium adsorption data were fitted using seven kinetic and six isotherms models. Activation created acidic moieties (>4700 µmol/g) and reduced the point of zero charge (<2.5). Freundlich isotherm best described the uptake of the dye onto the adsorbents suggesting a heterogeneous adsorption, whereas the Bangham and Avrami models best described the kinetics of adsorption process. An endothermic and spontaneous physisorption was responsible for the sorption phenomena in most adsorbents. The high removal of crystal violet was attributed to the high ionization capacity of the adsorbent coupled with the high external surface area (>44 m2/g). The best adsorption capacity (208 mg/g) was found for the activated and charred materials, whereas the lowest one (3.9 mg/g) was found for the pyrolyzed material. This research creates the possibility to deal with two environmental problems: (i) the reuse of shrimp waste and (ii) the removal of water pollutants such as crystal violet. [ABSTRACT FROM AUTHOR]

BACKGROUND: The recovery of metal ions from aqueous solutions for environmental preservation or resource saving requires the development of new sorbents with enhanced separation properties. A new process has been designed for the functionalization of magnetic chitosan microparticles with grafting of either amidoxime (AO‐AHC) or hydrazinyl amine (HZ‐AHC). Their sorption properties have been tested for the recovery of uranium(VI) and zirconium(IV) from aqueous solutions. RESULTS: A wide range of analytical tools is used for characterizing not only the chemical modifications but also the interaction mode between the sorbent and target metal ions; including elemental analysis and titration, Fourier‐transform infrared (FTIR) spectroscopy and X‐ray photoelectron spectroscopy (XPS) characterizations, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observations, energy‐dispersive X‐ray spectroscopy (EDX) analysis and textural characterization. The optimum pH values were found in the range 4–5. The maximum sorption capacities depend on the metal and the kind of functionalization: up to 1.38 mmol U g−1 for AO‐AHC and up to 1.96 mmol Zr g−1 for HZ‐AHC. The small size of magnetic particles limits the contribution of diffusion mechanisms in the overall control of uptake kinetics and the equilibrium is reached within 40–60 min. Metal desorption is highly effective (almost quantitative over five successive cycles of sorption and desorption) using 0.3 M hydrochloric acid solutions. CONCLUSION: AO‐AHC sorbent is more selective than HZ‐AHC in terms of separation of uranium(VI) from zirconium(IV), especially at pH close to 4. The results obtained in the treatment of acidic ore leachates confirm these trends. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The kinetics of Co ions sorption on CoTreat® was investigated in the 5–40 mg/L concentration range at a bulk temperature of 30 °C in HNO3 (pH 2.6). A pseudo-second order kinetic model best describes the sorption kinetics at low Co ion concentrations, while a pseudo-first order kinetic model was the best fit at higher concentrations. The equilibrium data were examined using the three models, viz. the Freundlich, Langmuir and Dubinin–Radushkevich (D–R) isotherms. The Langmuir and the D–R isotherms were the best fits to data from which the monolayer sorption capacity (Q0) and mean sorption energy (E) can be determined. The estimated values of Q0 and E were calculated to be 3.20 mg/g and 8.45 kJ/mol respectively at 30 °C. The thermodynamic parameters ∆H° and ∆S° were determined to be + 32.52 kJ/mol and 0.19 kJ/(mol K) in the temperature range 30–60 °C respectively, yielding negative values of the Gibbs free energy (∆G°), indicating the spontaneous nature of the process. The competitive sorption study of Co, Ce, Ru, Sb and Sr ions revealed that the CoTreat® exchanger can effectively remove all the elements concurrently. [ABSTRACT FROM AUTHOR]

Grafting of quaternary ammonium group is the main goal of this research for uranium recovery. The sorbent was investigated by FTIR, SEM–EDX, elemental analysis, thermogravemetric and XPS analyses, it shows high and fast loading performance (176.49 mg U g−1), the total equilibrium reached within 25 min, fitted by first order rate equation and Sips model for sorption kinetics and isotherms respectively. Complete desorption achieved after 30 min by 1.0 M NaCl in 0.1 M H2SO4. Sorption/desorption was measured after 10 cycles without significant loss in the capacity. Finally, the sorbent applied for uranium recovery of leaching solution from sulfuric acid on gibbsite bearing shale ore materials. [ABSTRACT FROM AUTHOR]

Nitrofurantoin is nitrofuran antibacterial drug that is most used as a veterinary pharmaceutic compound. This compound, as well as other pharmaceuticals can greatly affect the environment, the soil and organisms in it and pollute aquatic ecosystems. Since it has been used for only a few decades, knowledge of their fate and behaviour in the environment is still limited. Because of that, the aim of this study was to experimentally determine the K d values of nitrofurantoin in seven different natural soil and seven different sediment samples with different physico-chemical properties. Sorption phenomena were described with Linear, Freundlich and Dubinin-Radushkevich sorption isotherms. Obtained sorption coefficients (K d) ranged from 3.967 to 5.121 mLg−1 for sediment samples and 3.634–43.06 mL g−1 for soil samples. The influence of ionic strength and pH of the nitrofurantoin solution and kinetics of the sorption and desorption process were also investigated. Results show that an increase in ionic strength and pH reduces the values of sorption coefficient while the mechanism of nitrofurantoin sorption is the best described with the kinetic model of pseudo-second order. Unlabelled Image • The sorption of NFT in seven soils and seven sediments was investigated. • Sorption was tested with Linear, Freundlich and Dubinin-Radushkevich isotherms. • K d values indicated that NFT is moderately mobile/immobile in environment. • Physico-chemical properties of sediment/soil have great impact on NFT sorption. • Sorption of NFT is physical nature and follows pseudo-second-order kinetics. [ABSTRACT FROM AUTHOR]

Background: The wetting and hydration stage is the key step in manufacture process of several cereal‐based products. Knowledge of hydration properties of gluten‐free ingredients can contribute to improve the quality of gluten‐free products. The objective of the present work was to investigate hydration properties for a large variety of gluten‐free ingredients. Powders of tow gluten‐free cereals (rice and maize) and powders of tow legumes (chickpea and faba bean) in comparison with durum wheat semolina. The hydration properties were evaluated at 25°C by vapor and liquid water addition. Results: Legume powders had the highest sorption capacity and stronger interaction with vapor water. Rice showed the highest vapor water diffusion at all RH intervals. Water holding capacity, swelling kinetics, and immersion enthalpy in liquid water were higher for legume and maize powders. Conclusion: Gluten‐free cereal powders show hydration properties different from those of legumes. Different combinations of these gluten‐free materials can be made to approach the properties of wheat powders. [ABSTRACT FROM AUTHOR]

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An integrated approach is presented on wastewater treatment for power plants and the disposal of carbonate sludge—the waste forming at the make-up water pretreatment stage at power facilities. Usually, carbonate sludge accumulates on sludge waste sites located on the territory of power plants, which leads to an adverse impact on the environment. In addition to solid waste, the station also produces a large quantity of wastewater, which must be cleaned before being discharged into a waterbody. Concentrated wastewater is traditionally subjected to local treatment, which is associated with economic costs, while domestic and storm sewage is treated at general production wastewater treatment plants. The article proposes a wastewater biosorption technology at the Karmanovskaya GRES in which conditioned carbonate sludge is used as a sorption material. The sorption ability of carbonate sludge is confirmed by sorption isotherms of petroleum products and ammonium nitrogen. The kinetic curves obtained as a result of research confirm that biosorption wastewater treatment with carbonate sludge has a higher efficiency than conventional biological treatment. With the introduction of carbonate sludge into the aerotank for biosorption, the efficiency of wastewater treatment at the Karmanovskaya GRES increases significantly in terms of 5-day BOD, phosphate ion, chemical oxygen consumption (COD), ammonium nitrogen, and petroleum products. The use of carbonate sludge as a sorption material will improve the quality of treatment of all types of wastewater without their local treatment, which is equivalent to the wastewater's final biofiltration. When implementing the technology of biosorption cleaning with water treatment sludge, the prevented environmental damage to the Karmanovsky reservoir will amount to 1 463 000 rubles per year in the event of oil- and salt-containing wastewater discharge from the GRES into the inlet chamber. The economic calculation of the presented technology is performed: the payback period will be 3 years and 10 months and the economic effect will be 563 000 rubles per year. [ABSTRACT FROM AUTHOR]

The demand for plantain flour has increased in recent years due to its health benefits and industrial applications, however, there is dearth of information on the effect of drying methods on the sorption isotherm of plantain flour. In the present study, moisture sorption properties for unripe plantain flour using four drying methods at temperatures 27 °C, 37 °C and 42 °C were determined for water activity 0.10 to 0.80. The data generated were modelled using Peleg, GAB, Oswin, BET and Langmuir. The results revealed that the Equilibrium Moisture Contents decreased with an increase in temperature at all the water activities considered. Also, moisture isotherms of the plantain flour were not significantly (p>0.05) affected by temperature. The coefficient of determination (R2) for the used models ranged from 0.640 and 0.986 and Peleg was the most appropriate for the adsorption isotherm of plantain flour out of all the models. The monolayer moisture content of the flour also showed that all the unripe plantain flours could be stored for longer periods at all the temperatures studied, as their Mo falls within acceptable range for storage. [ABSTRACT FROM AUTHOR]

In this research work, the separation of Uranium from phosphate medium via adsorption prior to its fluorometric determination was carried out onto a newly synthesised adsorbent made via impregnation of urea onto cellulose (UIC). The full characterisation of the synthetic extractant (UIC) was carried out by various instrumental techniques such as elemental analysis, FTIR, TGA, XRD and SEM analysis. Various factors that may affect the quality of adsorbing U (VI) ions using synthesised Urea-impregnated cellulose had been investigated. The maximum adsorption capacity (82 mg/g) for U (VI) has been verified by the Langmuir isotherm model. The thermodynamics and kinetics of the adsorption process indicated that the uranium sorption onto synthesised Urea-impregnated cellulose was an exothermic and pseudo-second-order process. The tolerance limits for the common cations which are actually found with uranium in the phosphate solutions and may show sorption behaviour on the synthesised UIC resin were calculated and gave a high tolerance limit. Contrary to previously reported studies, several ameliorations have resulted including an elevated selectivity and adsorption capacity of uranium from phosphate medium. The optimised method was applied with good accuracy results for determination of uranium in reference and different phosphate rock types bearing uranium. [ABSTRACT FROM AUTHOR]

Eugenia uniflora L. leaves were dried in a conveyor-belt dryer to assess the influence of drying conditions (air temperature and number of passes/residence time in the dryer) on the yield, composition, antioxidant activity and concentration of phenolic compounds found in the extracts obtained from supercritical extraction. An analysis of leaf drying in the conveyor belt was carried out by investigation of sorption isotherms and drying curves obtained under air temperatures of 50, 60 and 70 °C. The sorption curves were fitted to the GAB thermodynamic model and the drying curves to a one-parameter empirical equation. The fitted equations were effective to predict the discharge moisture as function of the residence time under different temperatures. The samples for extraction were dried under 50°C/120min, 60 °C/60 min and 70 °C/60 min and their moisture levels were reduced respectively to 15 wt.%, 10wt.% and 6 wt.%. The extractions were carried out at 80 °C and 250 bar using as solvents either the pure supercritical CO2 or a mixture of ethanol and supercritical CO2 at a mass ratio of 0.5:1. The higher extraction yields (9.9 ± 0.1 wt.%), phenolic content (85 ± 2 mg GAE/g extract) were found in the extracts from samples dried under 60 °C/60 min using ethanol as a co-solvent in extraction. [ABSTRACT FROM AUTHOR]

Sustainable construction has become a real issue in Algeria and in the whole world. The compressed and cement stabilized earth blocks remain among the materials that contribute to a healthy, ecological and sustainable environment, as well as a source of interior comfort. In this work, an experimental investigation is performed on hygrothermal characterization of Compressed and cement Stabilized Earth Blocks with a moderate portion of 6%. The characterization of sorption isotherms was performed according to the "gravimetric" method in a temperature of 23 °C and relative humidity ranging from 9% to 99%.Twelve models were used to adjust the sorption isotherms of cement stabilized earth blocks. Therefore, only OSWIN model yielded a good result with a relative error experimented with a mean relative error less than 10%. In this work, the thermo-hydric characterization includes thermal conductivity, specific heat, and water vapor permeability [ABSTRACT FROM AUTHOR]

In this study, the role of lead [Pb(II)] in the sorption of arsenate [As(V)] by a Ca-polygalacturonate network (CaPGA), i.e. a model of root mucilage, was determined in acidic conditions (pH 4.5) commonly occurring at the soil–root interface. Sorption isotherms and kinetics showed that CaPGA was able to sorb As(V) (~0.89 mmol g−1 CaPGA) only in the presence of Pb(II). The concurrent sorption of Pb(II) by CaPGA (~2.30 mmol g−1), and the FT-IR spectra, suggested the formation of binuclear complexes involving one As(V) anion and two Pb(II) cations, which were in turn involved in bridging complexes with two carboxylate groups of CaPGA. The As(V) sorption by the Pb(II)-PGA system followed a pseudo-second-order kinetic model, while the sorption isotherms data fitted the Langmuir model better than the Freundlich one. The release of As(V) and Pb(II) from the As(V)-Pb(II)-PGA system, following treatment with environmentally relevant organic acids, i.e. citric and malic acids (0.0–24 mM concentration range), showed that As(V) was strongly retained and that both organic acids were able to mobilize similar As(V) and Pb(II) pools. Plant growth experiments showed that CaPGA was effective at reducing the As(V) phytotoxicity toward triticale plants (×Triticosecale Wittm.) in the presence of Pb(II), highlighting the environmental relevance of the interactions reported in this study. [ABSTRACT FROM AUTHOR]

In this research, the sportive removal of cerium ions (Ce (IV) from aqueous solution by rice husk (RH) has been studied in batch mode at ambient temperature. The effect of operational parameters such as contact time, amount of sorbent, initial concentration of metal ion and temperature on the percentage removal of Ce (IV) from aqueous solution was investigated. The Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray analysis techniques were used to confirm the sorption of Ce (IV) onto RH. Kinetics models including pseudo-first-order, pseudo-second-order, Elovich, liquid film diffusion, modified Freundlich equation and Bangham equation were used to study the sorption kinetics. Results showed that the sorption data fitted-well to the pseudo-second-order kinetic model. Experimental data was also subjected to Linear and Nonlinear forms of Langmuir, Freundlich, and Dubinin-Radushkevivh isotherms and attained results exhibited that the sorption data fitted well to nonlinear and linear sorption isotherms. Thermodynamic study indicated that the sorption of Ce (IV) onto RH was an endothermic process and spontaneous in nature. Moreover, the recovery of Ce (IV) and regeneration of sorbent (RH) was carried out by employing various desorbing media. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Efficient grafting of hydrazinyl amine on chitosan-coated magnetite. • High sorption capacity for divalent metals at near neutral pH. • Sorption isotherms are fitted by Sips equation. • Sorbent can be reused for at least 5 cycles using 0.5 M HCl as eluent. • Selectivity for Pb(II) for decontaminating multi-metal stormwater. Abstract The sorption properties of a functionalized magnetic chitosan sorbent have been investigated for the recovery of Ni(II) and Pb(II) from aqueous solutions. This material was prepared by one-pot co-precipitation of chitosan with formation of magnetic core, followed by a series of grafting steps to immobilize hydrazinyl amine derivative at the surface of chitosan layer. The physico-chemical characteristics of this composite material were investigated using FTIR, XRD, XPS, thermogravimetric, titration, elemental analyses. In a second step, the sorbent was tested for heavy metal sorption on synthetic solutions through the study of pH effect, sorption isotherms and uptake kinetics, selective sorption (in function of pH), metal desorption and sorbent recycling. Sorption isotherms were modeled using the Sips equation while the uptake kinetics was fitted by the pseudo-second order rate equation. The sorption capacity reached 4.3 mmol Ni g−1 and 2.5 mmol Pb g−1 but the sorbent was more selective to Pb(II) over Ni(II), especially in acidic conditions. The decrease in sorption capacity at the fifth cycle does not exceed 8%. In the final step of the study, the sorbents were successfully applied for metal recovery from multi-metal synthetic solution and from a contaminated stormwater collected in a local mining area. [ABSTRACT FROM AUTHOR]

Biodegradability and water resistance of cassava starch trays with different plasticizers [glycerol, sorbitol and polyvinyl alcohol (PVA)] were investigated. The degradability was tested by exposure at two amylolytic enzymes of microbial origin, one of them commercial (Termamyl®) and the other obtained in laboratory by the submerged cultivation of the fungus Penicilium echinulatum. The extent of degradation was analyzed by the percentage of weight loss and the concentration of released reducing sugars. The results showed that the packaging was sensitive to the action of the enzymes, because it was observed an increase in the concentration of reducing sugars in the first hours of reaction and percentages of weight loss near 90%. Water resistance was measured by solubility, contact angle and moisture sorption isotherms, with adjustment of the experimental data to mathematical models of Guggen-heim, Anderson de Boer (GAB), Brunauer-Emmet-Teller (BET), Oswin and Jaafar. Trays containing PVA addition showed less solubility, with greater contact angle and lower equilibrium moisture (in aw 0.98). The mathematical models of GAB and Oswin reproduced the best fit to the experimental data of the isotherms. The starch trays showed biodegradability independent of the material used as plasticizer. [ABSTRACT FROM AUTHOR]

The aim behind this work is to demonstrate and validate a predictive experimental model of the thermophysical behaviors of the three argan products, leaves, pulps and fruits, using the experimental determination of sorption isotherms. They constitute an important information source to establish the stability of the products of argan and their conditions of conservation. The use of a suitable model for the analysis of the experimental data of sorption is a crucial step in the optimization and the design engineering setting on the scale of drying processes which are considered to be among the largest energy consumers in the chemical industry and agro-foodstuffs. The medicinal herbs are complex mixtures of chemical product that make it difficult to determine mass and heat mechanism. Digital simulations of the isotherms by the model of GAB (Guggenheim-Anderson-Boer) could not only correlate the equilibrium moisture content in food systems but also explain the different properties of sorbed water. Indeed, they are deemed of as helpful tools that allow better thermophysical valorization and lasting conservation. Net isosteric heat of sorption, total heat of wetting, differential entropy and spreading pressure were determined from the isotherms to define the energy associated with the sorption processes. The paper also investigates the impact of both the ionization (food irradiation) and the instant controlled pressure drop processes on water activity of the argan products. [ABSTRACT FROM AUTHOR]

Results are presented of a study of the sorption properties of iron-manganese bog ores, aimed to assess the possibility of using these ores to purify natural drinking water from underground sources to remove ions of manganese and iron. The kinetic dependences of the sorption process were examined, and the sorption characteristics of bog ores with respect to manganese and iron ions were determined. It was found that the natural material under study is an effective sorbent for extraction of manganese and iron ions from ground water without use of additional reagents. [ABSTRACT FROM AUTHOR]

Highlights • Consolidated composites were prepared for desiccant coated heat exchanger. • Texture properties of consolidated composites were different from silica gels. • Sorption rate coefficients of consolidated composites were 2–3 times higher. • Consolidated composites had enhanced equilibrium water uptakes. Abstract Desiccant materials play a crucial role in the whole performance of novel desiccant coated heat exchanger based systems which can handle sensible and latent loads simultaneously and separately within one single component. To improve sorption performance of widely utilized coated desiccant, i.e., silica gel, this paper introduces a new type of consolidated composite desiccant, by mixing silica gel with expanded natural graphite treated with sulfuric acid (ENG-TSA) and impregnating with LiCl. Consolidated samples with different densities of ENG-TSA were developed. Microstructure, sorption kinetics and sorption isotherms were investigated and compared with loose parent and composite silica gels. Results showed that both ENG-TSA and LiCl had negative influence on surface areas and pore volumes of consolidated composites. With proper choice of the density of ENG-TSA, both dynamic water uptake quantities and sorption rate coefficients of consolidated composites can be greatly enhanced than those of parent and composite silica gels. Calculated theoretical water uptakes for consolidated composites were approx. 20% less than those of composite silica gel, while measured water isotherms showed that consolidated composites possesses better adsorption capacity than composite silica gel. Fitting equations were developed based on the Polanyi theory for further system modeling. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the adsorption and desorption isotherms of Tunisian clay product at different temperatures with a water activity varying from 10.95 to 97% using the statistic gravimetric method, which is an important step to evaluate its hygroscopic character. It was found that when temperature increases, clay material becomes less hygroscopic due to physical and/or chemical changes in product. Ten mathematical models were used to fit experimental data of sorption isotherms. The fitting of the model to experimental data was evaluated with the correlation coefficient (R2) and the root mean square error (RMSE). The Oswin model was determined to be the best model for describing experimental data of adsorption and desorption in the investigated ranges of temperature and water activity. The net isosteric heat of sorption determined from sorption isotherms estimated from Oswin model and using Clausius-Clapeyron equation decreased continuously with increasing the equilibrium moisture content. [ABSTRACT FROM AUTHOR]

With the target of recovering rare earth elements (REEs) from acidic leachates, a new functionalized hydrogel was designed, based on the phosphorylation of algal/polyethyleneimine beads. The functionalization strongly increased the sorption efficiency of the raw material for Pr(III) and Tm(III). Diverse techniques were used for characterizing this new material and correlating the sorption performances and mechanisms to the physicochemical structure of the sorbent. First, the work characterized the sorption properties from synthetic solutions with the usual procedures (study of pH effect, uptake kinetics, sorption isotherms, metal desorption and sorbent recycling, and selectivity from multi-element solutions). Optimum pH was found close to 5; sorption isotherms were fitted by the Langmuir equation (maximum sorption capacities close to 2.14 mmol Pr g−1 and 1.57 mmol Tm g−1). Fast uptake kinetics were modeled by the pseudo-second order rate equation. The sorbent was highly selective for REEs against alkali-earth and base metals. The sorbent was remarkably stable for sorption and desorption operation (using 0.2 M HCl/0.5 M CaCl2 solutions). The sorbent was successfully applied to the leachates of Egyptian ore (pug leaching) after a series of pre-treatments (precipitation steps), sorption, and elution. The selective precipitation of REEs using oxalic acid allows for the recovery of a pure REE precipitate.

The strong demand for rare-earth elements (REEs) is driven by their wide use in high-tech devices. New processes have to be developed for valorizing low-grade ores or alternative metal sources (such as wastes and spent materials). The present work contributed to the development of new sorbents for the recovery of rare earth ions from aqueous solutions. Functionalized mesoporous silica composite was synthesized by grafting diethylenetriamine onto composite support. The physical and chemical properties of the new sorbent are characterized using BET, TGA, elemental analysis, titration, FTIR, and XPS spectroscopies to identify the reactive groups (amine groups: 3.25 mmol N g−1 and 3.41 by EA and titration, respectively) and their mode of interaction with Nd(III) and Gd(III). The sorption capacity at the optimum pH (i.e., 4) reaches 0.9 mmol Nd g−1 and 1 mmol Gd g−1. Uptake kinetics are modeled by the pseudo-first-order rate equation (equilibrium time: 30–40 min). At pH close to 4–5, the sorbent shows high selectivity for rare-earth elements against alkali-earth elements. This selectivity is confirmed by the efficient recovery of REEs from acidic leachates of gibbsite ore. After elution (using 0.5 M HCl solutions), selective precipitation (using oxalate solutions), and calcination, pure rare earth oxides were obtained. The sorbent shows promising perspective due to its high and fast sorption properties for REEs, good recycling, and high selectivity.

Current study investigated the sorption proprieties of madder roots. Sorption isotherms were measured through a gravimetric static technique using chemical salts, to control the surroundings water activity in a range of 0.05–0.9. Sorption measurements were conducted in three temperature 20, 30, and 40 °C. Integral proprieties were evaluated through Clausius-Clapeyron equation for a constant value of spreading pressure. In this study the optimal conditions for storage of madder roots were discussed in the indicated interval of temperature. The study findings showed that the madder roots isotherms were type II and the moisture content of product increased with the increase of water activity. Peleg and GAB models showed highly performance in fitting the sorption data. Integral entropy exhibited a minimum value in the region of 6–7% db, and 0.34–0.38 for moisture content and relative humidity, respectively. These conditions were considered as the best to preserve the madder roots shelf-life. • For reason of active commercial movement, madder roots storage is a major problem. • Sorption characteristics of roots were determined by a gravimetric method. • Peleg and GAB models offers the best fitting of the obtained sorption isotherms. • Stability conditions of roots were extracted from the integral entropy. [ABSTRACT FROM AUTHOR]

Recently, much attention has been focused on the application of the Ionic Liquids (ILs) with herbicidal activity in agriculture. It has been suggested that through the appropriate selection of cations and anions, one can adjust the properties of ILs, particularly the hydrophobicity, solubility, bioavailability, toxicity. In practical agricultural conditions, it will be beneficial to reduce the mobility of herbicidal anions, such as the commonly applied 2,4-dichlorophenoxyacetic acid [2,4-D] in the soil. Furthermore, microplastics are becoming increasingly prevalent in the soil, potentially stimulating herbicidal sorption. Therefore, we investigated whether cations in ILs influence the mobility of anions in OECD soil supplemented with polystyrene microplastic (PS). For this purpose, we used the 2,4-D based ILs consisting of: a hydrophilic choline cation [Chol][2,4-D] and a hydrophobic choline cation with a C 12 chain [C 12 Chol][2,4-D]. Characterization of selected micropolystyrene was carried out using the BET sorption-desorption isotherm, particle size distribution and changes in soil sorption parameters such as soil sorption capacity and cation exchange capacity. Based on the batch sorption experiment, the effect of microplastic on the sorption of individual cations and anions in soil contaminated with micropolystyrene was evaluated. The results obtained indicate that the introduction of a 1–10% (w/w) PS resulted in an 18–23% increase of the soil sorption capacity. However, the sorption of both ILs' cations increased only by 3–5%. No sorption of the [2,4-D] anion was noted. This suggests that cations and anions forming ILs, behave independently of each other in the environment. The results indicate the fact that ILs upon introduction into the environment are not a new type of emerging contaminant, but rather a typical mixture of ions. It is worth noting that when analyzing the behavior of ILs in the environment, it is necessary to follow the fate of both cations and anions. [Display omitted] • Moderate increase in cation sorption in soil with polystyrene • Polystyrene in soil does not sorbed 2,4-D anion • Hydrophobic cation is quantitively sorbed in soil • The tested ionic liquids are independent mixture of ions • Ionic liquids do not form a stable ion pair in the environment • Ionic liquids are not a new type of contaminant in the environment [ABSTRACT FROM AUTHOR]

[Display omitted] • SnO 2 -diatomite Nano-composite was developed with a facile and cost-effective route for Nd(III) sorption. • Nd(III) sorption followed Langmuir model, with high sorption efficiency (q m,exp : 1.376 mmol Nd g−1), and excellent recyclability. • Efficient Nd(III) desorption using 0.2 M HCl solution was achieved. • Low cost nanocomposite sorbent showed great prospects in acidic monazite leachate. Mesoporous SnO 2 -decorated diatomite nanocomposite was synthesized via a facile and cost-effective route as a promising candidate for neodymium(III) sorption. SnO 2 -diatomite structure was elucidated and characterized using FTIR, XRD, SEM-EDX, BET, DLS, and XPS. Maximum sorption capacity reaches 1.376 mmol g−1 at optimum pH 0 4.7. Equilibrium occurred within 60 min and the half-sorption-time (t HST) was decreased from 4.97 min. Langmuir and pseudo-second-order equation adequately fits experimental data. Sorption is endothermic, spontaneous, and governed by entropy change. The sorption mechanism was discussed (via SEM-EDX, FTIR and XPS analyses). Mesoporous SnO 2 -diatomite has good durability and reproducibility over multiple-cycles with sorption and desorption efficiency (greater than 96 %) over six cycles using HCl. Finally, the sorbent was efficiently tested on ore leachate of Egyptian monazite. [ABSTRACT FROM AUTHOR]

Thermal modification of spruce wood (Picea abies L.) was conducted at three different temperatures (160, 200, and 240 °C) and treatment times (1, 3, and 5 h). The cyclic sorption experiments were performed for relative humidity changes of 30 to 85%. The equilibrium moisture content of the thermally modified wood was reduced up to 50% after treatment at 240 °C for 5 h. The sorption isotherms were described with the Guggenheim, Anderson, and De Boer (GAB) model. Cyclic sorption increased the monolayer capacity. Thus, the monolayer sorption was increased, while the multilayer sorption was limited. The dependence of the mass loss, hysteresis loop, and the maximum difference of equilibrium moisture content on the modification temperature and duration was modeled by response surface methodology. There was a very strong correlation between the modification temperature and mass loss, while the relationship between treatment time and mass loss was insignificant. The correlations between the modification parameters and the descriptors of sorption hysteresis were stronger after cyclic sorption. The sorption hysteresis decreased after cyclic sorption. This result was mainly caused by the increase of the monomolecular sorption for the adsorption processes.

Chemically-modified alginate (obtained by grafting urea on alginate, with different ratios; alginate-urea ( 1:1 ) and its new derivatives alginate-urea ( 1:2 ) with an exceed of the percent of amino group by 7 %) was successfully tested for mercury sorption in aqueous solutions. The influence of pH on metal sorption was first investigated: optimum pH was close to 5.5. Sorption isotherms were modeled using the Langmuir and the Sips equations, and sorption capacity slightly increased with the increased of the % of–NH _2 in the sorbent and the maximum sorption capacity exceeded 200 mg Hg l ^−1 (1.07 mmol Hg g ^−1 ; for alginate-urea (1:2)), this means two times the sorption capacity of reference material (i.e., non-modified alginate), and also has a capacity improved compared to alginate-urea (1:1). Under selected experimental conditions the equilibrium was reached with 6–8 h of contact and the kinetic profiles were modeled using the pseudo-first order equation (PFORE), the pseudo-second-order rate equation (PSORE) and the resistance to intraparticle diffusion (RIDE). Surface functional groups, notably; –NH _2 , –OH and –COOH, were involved in mercury sorption by alginate-urea, suggesting the ion exchange, complexation and/or electrostatic interaction of Hg(II) on the alginate-urea surface. The use of this material, environmentally friendly and simply obtained from a renewable resource, reveals promising for the treatment of low-metal concentration effluents: sorption capacities are comparable to alternative academic and commercials sorbents.

The aim of this study was to investigate selected physical and biochemical properties of four vegetable freeze-dried soups. The water content, water activity, pH, color parameters, antioxidant activity (EC50), total polyphenolic content of fresh tomato, pumpkin, beetroot, and cucumber, and freeze-dried soups were measured. Sensory analysis was applied to compare sensory attributes of fresh and rehydrated soups. The sorption isotherms of freeze-dried soups were obtained with the application of the static and dynamic vapor sorption (DVS) method. The application of the freeze-drying method enabled the obtaining of dry soups with a low water content of 2–3%. The drying caused a significant change of color of all soups. The redness of soups decreased after drying for the beetroot soups from +39.64 to +21.91. The lower chroma value of 25.98 and the highest total color change ΔE*ab = 36.74 were noted for freeze-dried beetroot soup. The antioxidation activity and total polyphenolic content were reduced after drying, especially for the cucumber and tomato soups. The Peleg model was selected to describe the sorption isotherms of dried soups. The sorption isotherm of freeze-dried cucumber and beetroot soups had a sigmoidal shape of type II. The shape of the moisture sorption isotherm for freeze-dried tomato and pumpkin soups corresponded more with type III isotherms. The DVS method can be used to characterize the moisture sorption isotherms of freeze-dried products.

Experimental and mathematical modeling of the moisture sorption isotherms for biomass pellets during storage is performed in this study. The tested pellets are a mixture of 50% wood: spruce or pine, and 50% switchgrass agricultural biomass. Storage conditions, i.e., temperature and humidity, are tested by varying the environment conditions in a conditioning chamber. The experimental results show that the moisture sorption isotherms are not affected by the temperature. Nevertheless, the equilibrium moisture content depends on the kind of the tested pellets. Mathematical modeling of the experimental isotherms is performed using four common models: the Oswin, GAB, Henderson and Peleg models. The Oswin model is defined as the most appropriate model to predict the moisture sorption isotherms of the spruce–switchgrass pellets. It presents a coefficient of determination equal to 0.998, a standard error around 0.049 and a chi-square approaching 0.007. On the other hand, Henderson and GAB models show the best results for pine–switchgrass pellets, with a coefficient of determination varying between 0.998 and 0.997, a standard error range 0.054–0.065 and chi-square error between 0.008 and 0.009. The thermodynamic properties, which include the net isosteric of heat and the entropy changes of sorption, are also determined for all tested samples.

Abstract The processing to which a material is subjected can affect its physical or chemical structures, resulting in products with different hygroscopic behaviours. The present work studied the water adsorption properties of sorghum subjected to different types of processing: raw flour (produced by milling whole grain), extrudates (obtained using a double screw extruder) and extruded flour (obtained by milling the extrudates). The isotherms were obtained using an automated instrumental method. The tests were run in duplicate at 25 °C with relative humidity values ranging between 11 and 84%. The water adsorption data fitted the GAB model well, showing high coefficients of determination. The estimated water contents of the adsorption monolayer ranged from 5.3 to 6.9 g of water per 100 g of dry material. The sorption isotherms were affected by the type of processing, extrusion cooking resulting in products with less water in the monolayer (less hygroscopic). The milling process yielded high water contents in the monolayer, probably due to the breakdown of some polymer-polymer interactions, which exposed the binding sites. To ensure microbiological stability, the water contents in the materials should not exceed 6.9 g of water per 100 g of dry material for raw sorghum flour, 5.3 g of water per 100 g for sorghum extrudates and 6.7 g of water per 100 g for extruded sorghum flour.

This study aimed to evaluate the thermodynamic properties of sorption isotherms and glass transition temperature (Tg) and the thermal properties of a dye powder obtained from turmeric extracts using spray drying. The sorption isotherms were evaluated at 15, 25 and 35 ºC using the dynamic gravimetric method, wherein the isotherm data of the experiment were fit to GAB and BET models. Likewise, the Tg was measured using differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) was used to determine the mass loss, and the thermal properties (heat capacity, diffusivity and thermal conductivity) were determined using transient flow method. The results demonstrated that the GAB model best fit the adsorption data. The DSC analysis presented a glass transition temperature of 65.35 ºC and a loss of volatiles at 178.07 ºC. The TGA analysis indicated a considerable mass loss starting at 193 ºC, resulting in degradation of the product. The thermal properties demonstrated a heat capacity of 2.45 J/g ºC, a thermal conductivity of 0.164 ±0.001 W/mK and a thermal diffusivity of 8.7x10-8 ± 0.000 m2/s

One way to improve the quality of food products is by conducting more thorough research on regional foods. This approach has several benefits, such as promoting human health, supporting the local economy, and preserving cultural food traditions. In this regard, our study investigated the potential of nectarine powder as a regional fruit product that could be developed into a global innovation. The present study examined: the physicochemical composition, antioxidant activity, microbiological load, and adsorption and desorption characteristics of the nectarine powder. The fruit powder was acquired through the use of a heat pump dryer, where drying took place at 42 °C for a duration of 8 h until achieving a moisture content ranging from 13.5 % to 14.5 %. The approximate physicochemical values are as follows: proteins, total carbohydrates, crude fiber, ash content and total lipids. Microbiological parameters, namely the total count of mesophilic aerobic and facultative anaerobic microorganisms, yeasts and molds, Escherichia coli , Salmonella spp., coagulase-positive staphylococci, and coliforms were checked and found to be within the acceptable limits as stipulated by the relevant state standards. Antioxidant activity was demonstrated through the utilization of various methods, including DPPH (33.19 ± 0.09mMTE/g extract), ABRS (2.55 ± 0.05mMTE/g extract), FRAP (1.43 ± 0.03mMTE/g extract) and CUPRAC (0.83 ± 0.01mMTE/g extract) methods. Investigation of the mass transfer sorption characteristics is performed using the gravimetric-static method. The conditions of the experiment were selected according to the usual conditions in which the food products are found in the commercial depot. The equilibrium and monolayer moisture data are investigated at 10 °C, 25 °C and 40 °C and relative air humidity in the wide range from 11 % to 87 %, achieved by the salts saturated solutions. To depict the adsorption and desorption isotherms, the modified models of Halsey, Chung-Pfost, Henderson, and Oswin were selected., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Adelina Lazarova Vasileva reports administrative support and equipment, drugs, or supplies were provided by Bulgarian National Science Fund. This study was supported by the Bulgarian National Science Fund №КП-06-М47/7, project title: “Investigation of the mass transfer sorption characteristics of Bulgarian fruit powder and flour mixtures”, principal investigator: Chief Assist. Prof. Adelina Lazarova Vasileva, PhD, Technical University of Sofia, branch Plovdiv, Bulgaria. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

A divinylbenzene cross-linked polystyrene resin with amine functional groups (Purolite A170) was grafted with glycidol and characterized as a novel sorbent, GLY-resin, for the oxoborate removal from model solutions and post-crystallization lye. The sorption behavior of GLY-resin was investigated using a batch system. The results showed that the sorption was maximal at pH=9.5. The equilibrium was achieved after 24 h. Calculations based on Langmuir model show the monolayer sorption capacity qm=1.3 mg/g and the fitted experimental data chemisorption as a dominating mechanism of boron sorption on GLY-resin. Boron removal from the solution containing 5 mg B/L and post-crystallization lye having a 9.1 mg B/L was 99% and 80% respectively. The thermodynamic calculations indicated the spontaneous and endothermic nature of the sorption process. The pseudo-second-order model adequately described the boron sorption on GLY-resin. Sorption−desorption efficiency was 100%, which means the boron sorption at next cycle did not decrease.

Cysteine-functionalized chitosan magnetic nano-based particles were synthesized for the sorption of light and heavy rare earth (RE) metal ions (La(III), Nd(III) and Yb(III)). The structural, surface, and magnetic properties of nano-sized sorbent were investigated by elemental analysis, FTIR, XRD, TEM and VSM (vibrating sample magnetometry). Experimental data show that the pseudo second-order rate equation fits the kinetic profiles well, while sorption isotherms are described by the Langmuir model. Thermodynamic constants (ΔG°, ΔH°) demonstrate the spontaneous and endothermic nature of sorption. Yb(III) (heavy RE) was selectively sorbed while light RE metal ions La(III) and Nd(III) were concentrated/enriched in the solution. Cationic species RE(III) in aqueous solution can be adsorbed by the combination of chelating and anion-exchange mechanisms. The sorbent can be efficiently regenerated using acidified thiourea.

From the examples of three and four-component polymer-polymer systems characterized by amorphous separation, an original technique for determining the pair parameters of interaction between components based on the sorption isotherms of common solvent vapor, particularly water vapor, has been developed. The possibility of calculating thermodynamic characteristics of multicomponent polymer compositions with specific interactions of functional groups from experimentally obtained sorption isotherms is shown. An algorithm for calculating pair interaction parameters, estimating concentration dependences of chemical potential and Gibbs free energy of mixing, and predicting the phase state of polymer mixtures was presented for the first time for such systems. The technique was tested on the example of systems poly(N-vinylpyrrolidone) (PNVP)-polyethylene glycol (PEG), PNVP-PEG-Poly(acrylic acid) (PAA), poly(N-vinylcaprolactam) (PNVCL)-PEG, and polyvinyl alcohol (PVA)-PEG.

Graphical abstract Highlights • The sequestration of As(III), Cr(VI) and competitive As(III)-Cr(VI) on/in nanostructured minerals was reinvestigated. • The minerals have high potential to remove As and Cr from water. • As and Cr sorption isotherms were modelled with a Langmuir and Hill models. • As(III) was partially oxidized (up to 22%) in the competitive system with Cr(VI). • As(III) sorbed on ferrihydrite and goethite adopted edge and corner sharing geometries. Abstract Sorption isotherms remain a major tool to describe and predict the mobility of pollutants in natural and anthropogenic environments, but they are typically determined by independent batch experiments. In the present study, the sequestration of As(III), Cr(VI) and competitive As(III)-Cr(VI) on/in 6L-ferrihydrite, siderite and goethite nanostructured minerals was reinvestigated using stirred flow-through reactor experiments. Herein, sorption isotherms were particularly determined from breakthrough curves for inert and reactive tracers monitored simultaneously in a single percolation experiment. In complement, X-ray absorption spectroscopy (XAS) was used to identify As sorption sites on 6L-ferrihydrite and goethite. As expected, the minerals have high potential to remove As and Cr from water (siderite = ferrihydrite (about 60 mg/g) > goethite (20 mg/g)). As and Cr sorption isotherms were modelled with a Langmuir model, and with a sigmoidal Hill model in the case of the competitive sorption. XAS measurements have revealed that As(III) was partially oxidized (up to 22%) in the competitive system with chromate oxyanion Cr(VI). As(III) sorbed on ferrihydrite and goethite adopted edge-sharing and corner sharing complex geometries. Nowadays, a new class of adsorbing phases is being developed for wastewater treatment, including engineered nanostructured materials and nanocomposites. The use of flow through reactor experiments as a high throughput method, combined with XAS, should be considered as efficient screening methods to test their sorbing properties on various contaminants. [ABSTRACT FROM AUTHOR]

Abstract Biochar is a highly efficient and attractive candidate for remediation of heavy metals in aqueous media, due to its immense porosity and surface functionalities. In this study farmyard and poultry manure were converted to biochars. The biochars' pre- and post-characterization was performed through various analytical techniques such as thermogravimetry, X-ray photon spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive spectroscopy. The contemporary batch adsorption work articulates the effect of biochars concentration, H+ ion concentration, contact time and temperature on sorption efficiency of Cr(III) ions from aqueous media. The sorption kinetics of Cr(III) was sound tailored to the pseudo-second-order equation which confirmed the chemisorption. The sorption isotherms suggested the well-fitting of Freundlich model due to the unfolding of multilayer adsorption. The Cr(III) sorption was assessed as 37.75 and 33.94 mg/g for farmyard manure and poultry manure-derived biochars, respectively. The thermodynamic values designated the spontaneous and exothermic nature of the reaction. Graphical abstract Unlabelled Image Highlights • Biochar showed the potential of Cr(III) removal from aqueous media. • Chemisorption and multi-layer sorption were the prevailing sorption mechanisms. • Cr(OH) 3 and Cr 2 O 3 stable complexes were confirmed by FTIR and XPS. • Manure could be a valuable feedstock for biochar production and metal sorption. [ABSTRACT FROM AUTHOR]