Sorption Parameters Research Articles

Elimination of torasemide from aqueous medium: influence of sorption and photocatalytic processes parameters supported by DFT analysis.

The sorption and photocatalytic activity of pharmaceutical torasemide using an immobilized TiO2 photocatalyst were investigate. The experimental design included optimization of reaction conditions such as pH and initial pharmaceutical concentration in aqueous solution using the response surface modeling approach, scavenger tests to gain insight into the photocatalysis mechanism, and application of the process to more complex water matrices. TiO2 in the role of sorbent showed a low capacity for torasemide (12.23-29.83μg/g within 24h of contact), making this type of removal inefficient on its own. Investigating the sorption process influenced by different process parameters such as pH, temperature, ionic strength, and dosage of TiO2 applied, the low tendency to this kind of material was affirmed by low Kd values (0.70 to 6.78mL/g) obtained by linear isotherms. Photocatalysis proved to be the better choice for the removal of torasemide from water, with the best kinetics at pH 4 and concentration of 5mg/L with half-time for degradation of 34.83min. Computational DFT analysis identified the zwitterionic torasemide structure as predominant under neutral and acidic conditions. It also showed that negatively charged areas around nitrogen-containing fragments probably have the highest potential to promote the TiO2 sorption at low pH conditions, where it is highest, through electrostatic attractions and N-H∙∙∙∙∙OTiO2 hydrogen-bonding contacts.

Recovery of precious metals from aqua regia leachate of e-wastes using dithiocarbamate-modified cellulose and development of a novel kinetic model

The escalating demand and dwindling natural supplies of precious metals (PMs) necessitate innovative hydrometallurgical recovery approaches with rapid kinetics and reduced environmental impact. The current study investigated the sorption and recovery of PMs from electronic waste (e-waste) utilizing dithiocarbamate-modified cellulose (DMC) and its proline derivative with epoxy cross-linkage (DMC-Pro-Epo-6) in aqua regia (AR). The effects of various sorption parameters, such as sorbent dose in feed, HCl:HNO3 ratio, AR dilution times, etc., on PM recovery were explored. Equilibrium for AuIII and PtIV sorption by DMC and DMC-Pro-Epo6 was reached in less than an hour, which is significantly faster than most reported sorbents. The maximum sorption capacities in AR settings, calculated using the Langmuir equation, were 348.0 mg g−1 for AuIII and 34.7 mg g−1 for PtIV for DMC, while DMC-Pro-Epo6 achieved 350.3 mg g−1 for AuIII and 31.1 mg g−1 for PtIV. These capacities, particularly for the higher sorption capacity of AuIII by DMCs, are attributed to the relativistic effects of gold, soft–soft interactions, and strong sulfur binding. FT-IR, FE-SEM, and EDX analyses elucidated the chelation bonding and mechanisms involved in PM sorption onto DMCs. By utilizing AR-DMC integrated techniques, step-by-step protocols were established for Au recovery from diverse e-waste sources, such as smartphones and smart chip cards. The study also highlighted the importance of chemical pre-concentration of e-waste to remove base metals, facilitating efficient PM recovery. Finally, a key innovation of this work is introducing a new pseudo-mix order fractional model, based on the preference of active sites with fractional assumptions, which more accurately correlates the sorption kinetics observed in complex systems.

Selective extraction of lead from chelator-rich effluents using a biomass-based sorbent

The efficient removal of lead (Pb) from waste streams containing chelators presents a significant challenge due to the high stability and mobility of Pb-chelator complexes. This study investigates a novel approach utilizing a biomass-based sorbent, proline-incorporated dithiocarbamate-modified cellulose with epoxy-cross-linkage (DMC-Pro-Epo6), to extract Pb from effluents with excess chelators. DMC-Pro-Epo6 exhibited exceptional Pb(II) sorption performance under controlled and various chelator-rich conditions. The sorbent maintained high sorption efficiency even with 100-fold excess chelator concentration and competing metal ions. DMC-Pro-Epo6 also outperformed commercially-available ion-selective sorbents in terms of separation efficiency. The sorption kinetics followed a pseudo-second order model, demonstrating rapid sorption with equilibrium reached within 20 min. The maximum sorption capacities of DMC-Pro-Epo6 obtained from the Langmuir isotherm model were 1267 and 659 µmol g−1 in Pb(II)-containing aqueous solution and Pb(II)-containing EDTA solution, respectively. X-ray photoelectron and absorption spectroscopy analyses, along with sorption parameters, confirmed a chemisorption mechanism for Pb(II) sorption onto DMC-Pro-Epo6. Validation of the protocol using real waste samples with complex chelator and base metal ion matrices resulted in a quantitative and selective extraction of 92 to 99 % of Pb(II). This success suggests the potential for scaling up the developed process. Compared to conventional treatment methods, the proposed technique offers a more efficient and streamlined process for separating metal ions and chelators from effluents.

Modeling atrazine molecule dynamics in rhodic ferralsol: calibration and testing of the MACRO 5.2 model

Assessing the risks of pesticide use in the environment, especially in groundwater, requires predicting their movement. Pesticide leaching models represent an accessible and economical method to predict groundwater and surface water pollution and should be calibrated based on experimental data to better understand the dynamics of pesticides in soil and ensure their efficiency. This long-term study explored the ability of the MACRO model to describe water movement and atrazine distribution along the profile of a Rhodic Ferralsol cultivated with corn in western Paraná, Brazil, using data from a drainage lysimeter under high intensity simulated rainfall (150 mm h-1). The soil parameters analyzed in the laboratory were used as pedotransfer functions. The initial simulations showed significant differences, due to the particularities of the model and the complexity of the soil and its pore space, so the tests adjusted the retention curve and the sorption parameters. After final adjustments to the model, the simulated atrazine mass results were evaluated. Calibration of pesticide concentrations required small changes in sorption and degradation rates, and the results were compared to quantities measured at a specific depth. The simulation of atrazine transport was considered acceptable, estimating 0.71, 4.63, and 3.05% of the total mass of atrazine in percolate, runoff and retained in the profile, respectively.

Synthesis and Characterization of Low-Cost Zirconium Nanocomposites as Novel Adsorbents for Arsenazo III Pollutant

Removing contaminated Arsenazo III dye from contaminated effluent is a challenge and of great interest due to its hazard and environmental impact. Therefore, the biggest challenge was producing highly efficient, easy to recycle, and economically inexpensive adsorbent materials for the contaminated dye. Three chemically stable zirconium nanocomposites with unique properties were synthesized by gel-precipitation technology. The composition, chemical, and physical properties of zirconium molybdate, tungstate, and silicate nanocomposites have been extensively proven using many different and appropriate devices such as XRD, SEM–EDX, TEM, FT-IR, BET, DLS, TGA-DTA, and zeta potential. By utilizing the most effective adsorption techniques, Azo-dye was successfully bound to ZrMo-NPs, ZrW-NPs, and ZrSi-NPs composites. The uptake capacities for these composites were measured at 0.29, 0.79, and 1.61 mmol.g−1, respectively. The sorption parameters were optimized as follows: a feed solution pH of 3 for ZrMo-NPs, a pH of 2.3 for ZrW-NPs, and a pH of 2.3 for ZrSi-NPs. The stirring time was set at 30 min, the metal ion concentration was 1.64 mmol L−1, and the sorbent dose was 7.5 mg. The adsorption results agreed well with the Langmuir isotherm and the pseudo-second-order reaction models and demonstrated the endothermic nature and kinetic improvement by increasing temperatures. The three nanocomposites effectively eliminated tainted dye from lab wastewater, offering promise for their potential applications in the future.Graphical

Nano‐Enhanced Water Purification: Uncovering the Dye Adsorption Efficiency of Ni‐Zn‐S@Cyclodextrine Nanomaterial

AbstractThis research investigates the synthesis of a hybrid nanomaterial, denoted as Ni‐Zn−S@Cyclodextrine, through a cost‐effective and easy co‐precipitation method. The resulting nanomaterial has been thoroughly characterized and applied for the adsorptive removal of Crystal violet and Congo red dyes from their solutions. The study delves into the thermodynamics and kinetics of the sorption process, as well as helps to propose adsorption mechanism for both the dyes onto the Ni‐Zn−S@Cyclodextrine surface. A comprehensive analysis, encompassing techniques, such as XRD, FTIR, SEM‐EDX, TEM, TGA, Zeta potential, and XPS, have been conducted to explore the structural and morphological attributes of the prepared nanomaterial. Furthermore, key sorption parameters, including adsorbent's dosage, temperature, contact time, and solution pH, have been systematically optimized to achieve maximum efficiency. The TEM images of prepared nanomaterial indicated the particle size ranging between 60–80 nm. Moreover, it exhibited a strong affinity for both the dyes, with a maximum adsorption capacity of 138.20 mgg−1 for Congo red and 129.95 mgg−1 for Crystal violet dyes at 303 K. The thermodynamics of the adsorption process indicated an endothermic and spontaneous nature. Isotherm studies revealed that the data best aligned with the Freundlich isotherm, while the kinetics of the reaction adhered to a pseudo‐second order within the investigated temperature range.

Sorption experiments as efficient as possible: Mini-column experiments (MCE) using HPLC-ICP-MS coupling with a new data analysis approach to determine sorption parameters

To quantify retention and sorption parameters, diffusion-, batch- or column experiments are common practice. However, these are either not close to nature, extremely time-consuming or material intensive. A promising approach to eliminate these problems is the performance of mini-column experiments (MCE). Due to dynamic retention and realistic solid–liquid ratios, these are close to nature and resource-efficient. The aim of this work is to perform highly controllable MCE using a HPLC (high-performance liquid chromatography) system and HPLC-ICP-MS (inductively coupled plasma mass spectrometry) coupling. With this approach, ultra-fast sorption experiments are possible only using 100–150 mg adsorbent and 160 mL eluent. That means, sorption experiments are even more time- and cost-efficient and also more controllable than with conventional methods. The presented method is based on a newly developed MCE-HPLC-ICP-MS coupling, which was applied to investigate the sorption of Eu(III) on kaolinite and sand in 10 mM NaCl. With that it was possible to carry out dynamic sorption experiments in just 5–15 h and thus determine e.g. maximum loading capacity (qmax) in a very short amount of time. Furthermore, a quantification method for eluates of high ionic strength is presented. Here, the sorption of Cs(I) on calcium silicate hydrate (C-S-H) phases in 10 mM and 100 mM NaCl was investigated. For validation, the sorption distribution ratios (Rd) obtained were compared with those from batch experiments. These agreed very well with each other and with those from the literature. Overall, with MCE more sorption parameters can be determined much faster, more accurately and more efficient than with the conventional methods.

Effective and sustainable removal of Pb2+ ions from wastewater by a new synthetic bis-thiosemicarbazone derivative immobilized in amberlite XAD-2: Kinetic, isotherm and thermodynamic aspects

ABSTRACT A new composite material, named TSC/AXAD-2, was developed by incorporating a bis-thiosemicarbazone derivative (TSC) into Amberlite XAD-2 to extract Pb2+ ions from wastewater. The new composite was characterized using XPS, TGA, FTIR, BET, EDX, 1H-NMR, 13C-NMR, and GC-MS analyses. The sorption parameters, such as pH value of media, equilibrium time, initial Pb2+ ion concentration, composite dose, temperature, and eluting agents, were methodically optimized. The utmost adsorption capacity is 45.3 mg.g−1; it was achieved at pH value of of 5.5, 15 min of agitation, room temperature, and initial concentration of 200 mg.L−1 Pb2+ ions. The isotherm studies revealed that the adsorption process closely matches the Langmuir model, with a theoretical retention capacity of 46.12 mg.g−1. Furthermore, kinetic modeling using the pseudo-first-order accurately depicted the adsorption of Pb2+ ions. The thermodynamic study suggested that the adsorption process is exothermic, spontaneous, and more favorable at lower temperatures. The desorption of Pb2+ ions from the loaded composite was conducted with 1.0 M of either HCl or HNO3. The TSC/AXAD-2 composite successfully met WHO and FAO guidelines for removal of Pb2+ ions from wastewater before its discharge into the marine environment.

Numerical and Experimental Approach to Evaluate Microplastic Transport in Saturated Porous Media

Under varying flow rate conditions, the transport and retention of polydisperse microplastics (MPls), with an average particle size of 16 ± 6 µm, were investigated in saturated porous media. First-order reversible and irreversible kinetic sorption models were used to describe the sorption kinetics. Sensitivity analyses provided insight into the effects of each sorption parameter. Both numerical modeling and experimental measurements were utilized to evaluate the retention rates of sand filters. The influence of flow rate on sorption was reflected in variations in the distribution coefficient (Kd), the mass transfer coefficient (β), and the irreversible sorption rate (K1). Lower flow rates were associated with higher Kd and β values, indicating increased sorption and reduced mass transfer rates. An increase in Kd resulted in a more gradual sorption process, with a decrease in peak concentration, whereas changes in β had a comparatively smaller impact on sorption rate and peak concentration. Lower K1 values were linked to higher peak concentrations and decreased retention efficiency. Numerical modeling revealed retention rates of 28 ± 1% at a flow rate of 31 mL min−1 and 17 ± 1% at 65 mL min−1. The introduction of MPls into saturated sand environments modifies the transport dynamics within the medium. Consequently, these alterations affect the hydrological characteristics of porous media, impacting groundwater quality and agricultural output. The mean absolute error (MAE) of 6% between the modeled and observed retention rates indicated a high level of accuracy. This study underscores the importance of examining retention efficiency and the accuracy of numerical models in understanding MPl transport in porous media.

Self-powered electromodulated liquid chromatography with preliminary charging of porous graphitic carbon

Electromodulated liquid chromatography (EMLC) allows controlling the retention times of some ions on a carbon sorbent due to the application of electric potential. A simplified two-electrode setup was proposed for EMLC with standard columns. Instead of simultaneous application of constant potential with chromatographic measurements the possibility of working in zero-current mode after preliminary polarization has been shown. Potentiostatic charging of HypercarbTM under constant potential and the following measurement of open circuit potential (OCP) was suggested before recording the chromatogram. OCP appeared to be a more reliable parameter than the applied potential to control the sorbent state and its influence on the chromatographic parameters. Linear dependence of retention time on OCP was obtained as a proof of concept. The anodic charging of the sorbent resulted in the highest stability of the sorption parameters in self-powered regime: the retention of analytes in the absence of external potential is preserved for 3–4 h of chromatographic experiment.

Phosphorus Availability and Balance with Long-Term Sewage Sludge and Nitrogen Fertilization in Chernozem Soil under Maize Monoculture.

A continuous long-term field experiment with maize monoculture was conducted to evaluate the P availability and balance, DM yield, P uptake, and P sorption parameters in chernozem soil after 27 years. A total of 2 doses of nitrogen (120 and 240 kg ha-1) were applied as mineral nitrogen (N120 and N240) and sewage sludge (SS120 and SS240) and compared with unfertilized control (Con). The aboveground biomass (DM) yields significantly increased in the order of Con < SS120 < SS240 < N120 < N240 treatments and the maximum P uptake was recorded for both N240 and SS240 (25.1 kg P ha-1) according to the nutrient application gradient. The N120 and N240 treatments positively influenced the DM yield but negatively influenced the P balance (-648 and -678 kg P ha-1 27 years-1), gradually bringing a risk of P deficiency in the soil. On the other hand, applications of SS120 and SS240 positively influenced the P availability and pseudototal (PAR) content in the soil, which resulted in a buildup of legacy P or an increase in P saturation greater than the environmental threshold value. Aluminum was found to be a major controlling sorption factor for P in our chernozem soil.

Comparing the potential of benchtop and handheld mid-infrared spectrometers for predicting soil phosphorus (P) sorption capacity and evaluating the influence of sample preparation

Traditional soil phosphorus (P) sorption capacity is examined from a Langmuir isotherm batch technique, which is time-consuming, labour intensive and generates chemical waste. In this work, we provide an efficient and convenient technique with MIR spectroscopy to predict the Langmuir parameter of soil P sorption maximum capacity (Smax, mg·kg−1).Four spectral libraries from benchtop (Bruker) and handheld (Agilent) MIR spectrometers were built with samples in two particle size ranges, <0.100 mm (ball-milled) and <2 mm. respectively. Using an archive of samples with a database of sorption parameters, soils were classified into ‘low’ and ‘high’ sorption capacities. Chemometric regression models of partial least squares (PLS), Cubist, support vector machine (SVM) regression and random forest (RF) were evaluated for Smax prediction. Bruker spectral libraries with both soil particle sizes yielded ‘excellent models’, with SVM predicting Smax values with high accuracy (RPIQV = 4.50 and 4.25 for the spectral libraries of the ball-milled and <2 mm samples, respectively). In comparison, the Agilent handheld spectral libraries contained more noise and less resolution. For Agilent MIR spectroscopy, more homogeneous samples after ball milling resulted in a higher accurate Smax prediction. For Agilent libraries of ball-milled samples, an ‘approximate quantitative model’ (RPIQV = 2.74) was obtained from the raw spectra using the Cubist algorithm. However, for Agilent spectroscopy of <2 mm samples, the best performing Cubist algorithm can only achieve a ‘fair model’ (RPIQV=2.23) with the potential to discriminate between ‘low’ and ‘high’ Smax values.The results suggest that the benchtop spectrometer can predict the Langmuir Smax value with high accuracy without the need to ball mill samples. However, the handheld spectrometer can only make approximate quantitative predictions of Smax for ball-milled samples. For <2 mm samples, Agilent can only be used to classify ‘low’ and ‘high’ sorption capacity soils.

Studies on Sorption and Release of Doxycycline Hydrochloride from Zwitterionic Microparticles with Carboxybetaine Moieties.

The aim of this study was to examine the use of zwitterionic microparticles as new and efficient macromolecular supports for the sorption of an antibiotic (doxycycline hydrochloride, DCH) from aqueous solution. The effect of relevant process parameters of sorption, like dosage of microparticles, pH value, contact time, the initial concentration of drug and temperature, was evaluated to obtain the optimal experimental conditions. The sorption kinetics were investigated using Lagergren, Ho, Elovich and Weber-Morris models, respectively. The sorption efficiency was characterized by applying the Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. The calculated thermodynamic parameters (ΔH, ΔS and ΔG) show that the sorption of doxycycline hydrochloride onto zwitterionic microparticles is endothermic, spontaneous and favorable at higher temperatures. The maximum identified sorption capacity value is 157.860 mg/g at 308 K. The Higuchi, Korsmeyer-Peppas, Baker-Lonsdale and Kopcha models are used to describe the release studies. In vitro release studies show that the release mechanism of doxycycline hydrochloride from zwitterionic microparticles is predominantly anomalous or non-Fickian diffusion. This study could provide the opportunity to expand the use of these new zwitterionic structures in medicine and water purification.

Adsorption of arsenic and fluoride: Modeling of single and competitive adsorption systems

The elevated co-occurrence of arsenic and fluoride in surface and groundwater poses risks to human health in many parts of the world. Using single and competitive batch equilibrium adsorption studies, this research focuses on As(V) and F adsorption by activated carbon and its modeling. BET, XRD, FESEM, EDS, and FTIR analysis were used to discern the structural characteristics of activated carbon. The influence of dosage, pH, and contact time were also investigated in single and simultaneous adsorption systems. The maximum adsorption capacity of activated carbon for arsenic and fluoride were found to be 3.58 mg/g and 2.32 mg/g, respectively. Kinetics studies indicated that pseudo-second-order kinetic model fit better than pseudo-first-order, Elovich, and intraparticle diffusion kinetic models. The non-linear regression analysis of Langmuir, Freundlich, Toth, Redlich Petersons, and Modified Langmuir Freundlich models was used to determine single-component asorption model parameters. Additionally, the simultaneous adsorption was rigorously modeled and compared using the Extended Langmuir (EL), Extended Langmuir Freundlich (ELF), Modified Competitive Langmuir (MCL), and Jeppu Amrutha Manipal Multicomponent (JAMM) isotherm models, and competitive mechanisms were interpreted for the simultaneous adsorption system. Further, the model performances were evaluated by statistical error analysis using the normalized average percentage error (NAPE), root mean square errors (RMSE), and the correlation coefficient (R2). According to the modeling results, single equilibrium data fitted better with the Modified Langmuir Freundlich isotherm model, with a higher R2 of 0.99 and lower NAPE values of 3.8 % and 1.28 % for As(V) and F, than other models. For the binary adsorption, the Extended Langmuir Freundlich isotherm model demonstrated excellent fit with lowest errors. All the competitive isotherm models fit the As(V) and F simultaneous sorption systems reasonably well. Furthermore, the research unveiled a nuanced hierarchy of isotherm fitting, with ELF > EL > MCL > JAMM in varying arsenic at a constant fluoride concentration, and ELF > JAMM > EL > MCL in varying fluoride at a constant arsenic concentrations. In addition, competitive studies divulged crucial insights into selective adsorption, as As(V) exhibits a pronounced adsorption selectivity over F on activated carbon. In essence, As(V) showed a more pronounced antagonistic behavior over F, whereas F exhibited a much lesser competitive behavior in the adsorption of arsenic.

Flow rate and kinetics of trace organic contaminants removal in black carbon-amended engineered media filters for improved stormwater runoff treatment

Urban stormwater runoff is considered a key component of future water supply portfolios for water-stressed cities. Beneficial use of runoff, such as capture for recharge of drinking water aquifers, relies on improved stormwater treatment. Many dissolved constituents, including metals and trace organic contaminants (TrOCs) such as hydrophilic pesticides and poly- and perfluoroalkyl substances (PFASs), are of concern due to their toxicity, persistence, prevalence in stormwater runoff, and poor removal in conventional stormwater control measures. This study explores the operational flow rate limitations of black carbon (BC)-amended engineered media filters for removal of a wide suite of dissolved metals and TrOCs and provides validation for a previously developed predictive TrOC transport model. Column experiments were conducted with face velocities of 40 and 60 cm h−1 to assess Douglas Fir-based biochar and regenerated activated carbon (RAC) filter performance in light of media-contaminant removal kinetic limitations. This study found that increasing the face velocity in BC-amended filters to 40 and 60 cm h−1, which are representative of field conditions, decreased the removal of total suspended solids, turbidity, dissolved hydrophilic TrOCs, and PFASs when expressed as volume treated relative to previous studies conducted at 20 cm h−1. Dissolved metals and hydrophobic TrOCs removal were not substantially affected by the increased flow rates. A predictive 1-d intraparticle pore diffusion-limited sorption model with sorption and effective tortuosity parameters determined previously from experiments conducted at 20 cm h−1 was validated for these higher flow rates. This work provides insights to the kinetic limitations of contaminant removal within biochar and RAC filters and implications for stormwater filter design and operation.

Phosphorus release and distribution in sediment resuspension systems under disturbing conditions

The resuspension of phosphorus (P) in sediments has the most significant contribution to the overlying water. The PP release characterization during resuspension was investigated. The results indicated that the P in suspensions had more release risk compared to the sediments. The particulate P (PP) concentration (0.54 mg L−1) under high-intensity rotational speed (250 rad min−1) was about five times higher than others (0.11 mg L−1). The sorption parameters of zero equilibrium P concentration (EPC0F) and soluble reactive P (SRP) were significantly correlated with each other (p < 0.01, r = 0.73). Suspended solids expressed stronger P source than sediments. The values of EPC0F was highly significantly correlated with the sorption coefficient (KF) and native adsorbed P (NAP) (p < 0.01). The mean values of NAP were 0.0612 mg g−1 and 0.0604 mg g−1 in the Prophase and Metaphase, respectively, and 0.0586 mg g−1 at Anaphase. The values of P sorption index (PSI) ranged from 0.4359 to 0.6862 L g−1, with mean values of 0.5350 L g−1 (Prophase), 0.6061 L g−1 (Metaphase), and 0.4967 L g−1 (Anaphase). The degree of P saturation (DPS) decreased in the order of Anaphase (2.73%) > Prophase (2.53%) > Metaphase (2.12%). The release risk index of P (ERI) decreased in the order of Anaphase (5.47%) > Prophase (4.72%) > Metaphase (3.59%), with a range of 2.12%–8.56%. To fast and slow scale, the results of NaOH–P (V1<0, V2>0) contribution indicated that the persistent disturbance promoted the release of adsorbed dissolved PP from NaOH–P in suspended sediment to the overlying water. The contribution of HCl–P (V2 > 0) was positive in the Anaphase of the slow scale, and HCl–P was a PP source in the frequently disturbing conditions.

Rhenium sorption from simulated solution with AM-p-2 resin in dynamic mode

The article summarizes the research results on rhenium recovery with AM-p-2 strong-base macroporous styrene-divinyl benzene anion exchange resin with dimethylammonium functional groups from the simulated sulphuric medium and rhenium elution in dynamic mode attaining the recovery rate exceeding 90 % after approximately 1 500 bed volumes. Total dynamic exchange capacity 81.0 mg/g was measured, and column sorption parameters were evaluated using corresponding models. The authors denoted that the total dynamic exchange capacity values defined experimentally and calculated by Thomas fit were close. We studied rhenium elution with the solution containing ammonium nitrate 250 g/L and sulphuric acid 25 g/L yielding rhenium-rich solution that is ~63 times higher comparing to the initial solution. A clear peak in the elution profile allows getting rhenium-rich eluates. The research results will be necessary when defining mass-transfer parameters and designing equipment for processing industrial liquors and waste with rhenium recuperation.

Sorption of divalent metal ions from aqueous solutions on activated carbon with its further separation through electroflotation

Currently, there are multiple methods for wastewater treatment from metal ions. One of the leading methods is the sorption process. The advantage of sorption purification is its ability to extract substances from multi-component mixtures and its high efficiency with low concentrations of wastewater contamination. The purpose of this work was to study the sorption capacity of the “OU-B” activated carbon in relation to metal ions (Cu2+, Zn2+, Mn2+). The following tasks were set: establishing optimal parameters for sorption in a static mode, approximating the obtained data by linear forms of kinetic and adsorption equations, as well as obtaining the ability to separate coal particles from aqueous solutions by electroflotation. To study the patterns, we used the following research methods: low-temperature nitrogen adsorption, atomic absorption spectrometry, and nephelometry. The optimal parameters for sorption in a static mode (sample size of coal, process time, initial concentration of metal ions) were established experimentally. The maximum degree of extraction of metal ions in the course of sorption was achieved with a 1:133 ratio of coal to aqueous solution during 60 minutes and was 82% for Cu2+, 73% for Zn2+, and 63% for Mn2+. The obtained sorption results were analysed using the kinetic models of Zeldovich-Chen-Clayton of pseudo-first and pseudo-second order and adsorption models of Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Flory-Higgins. The analysis showed that the sorption of Cu2+, Zn2+, and Mn2+ on OU-B carbon occurred according to the mechanism of physical adsorption, which was described by the sorption models of Langmuir and Freundlich and the Zeldovich-Chen-Clayton kinetic model. The separation of used sorbents and the aqueous phase was a difficult task from a technological point of view due to the small size of carbon particles. The article showed the prospects of using electroflotation for extracting OU-B carbon from aqueous solutions: the degree of extraction of coal particles reached 97-99% when cationic or non-ionic SAS were added to the solution.

Kinetics and Thermodynamics Equilibrium of Nickel Metal Ions Sorption onto Carbon Nanofibers Irradiated by Ultrasonic Energy

In this work, we investigated the effects of the heavy metal initial concentration and the pH on the sorption of heavy metal ions onto carbon nanofibers using the liquid phase adsorption technique under ultrasonic energy irradiation. These data were then used to study thermodynamic aspects such as sorption capacity and energy and kinetic parameters such as kinetic model, reaction order, and rate constant of heavy metal sorption on carbon nanofibers. We found that the increase of the heavy metal (nickel) initial concentration was proportional to the amount of heavy metal adsorbed onto carbon nanofibers. The highest uptake of the heavy metal ions' amount onto carbon nanofibers in equilibrium (qe) was 244.00 mg.g-1, achieved at the pH of 8. Langmuir and Freundlich's isotherms were used to find the best-fitted isotherms model. The Langmuir isotherm best fits the sorption equilibrium of the heavy metal ions on Carbon nanofibers. Bothipseudo-first and pseudo-second orders studied the sorption and kinetic parameters of heavy metals on carbon nanofibers. The sorption kinetics model was fitted to the pseudo second-order. Based on the value of Gibbs free energy, the metal ions' sorption onto carbon nanofibers occurs spontaneously.

SORPTION ISOTHERM, PROXIMATE COMPOSITION AND SENSORY EVALUATIONS OF OVEN DRIED AND FRIED CHEESE PRODUCTS FROM LOCAL SOFT CHEESE

In this study, the sorption isotherm, proximate composition and sensory characteristics of oven dried and fried cheese were investigated. The understanding of the moisture sorption properties, nutrient composition and sensory properties of the oven dried and fried cheese can help quality, shelf-life prediction and overall acceptance. The experimental methodology for this study followed a standard procedure to determine the sorption isotherm of oven-dried and fried cheese samples. First, the raw milk samples were obtained from white Fulani cows at the Teaching and Research Farm, Ekiti State, University, Ado-Ekiti, Nigeria and processed into cheese. The cheese was divided into two portions: one group was oven-dried at 50 0C for 16 hours, while the other group was fried in pre-heated edible canola to internal temperature of 68oC. Sorption parameters, proximate and sensory characteristics were carried out according to standard methods. This study revealed that the monolayer moisture was higher in fried cheese than oven dried cheese. Oven-dried cheese had 0.299 water activity and 21.26 monolayer moisture while fried cheese had higher water activity of 0.32 and monolayer moisture of 29.67. Fitness of curve (R2) of 0.731 0.903 were computed for oven-dried and fried cheese. The results of proximate composition and sensory characteristics showed that processing methods influenced the sensorial properties and nutritional composition of oven-dried and fried cheese. In conclusion, oven-dried cheese can be predicted to be more stable than fried cheese. KEYWORDS: Adsorption, Equilibrium, GAB Equation, Monolayer, Salts.