Equilibrium Isotherms Research Articles

Adsorptive decolorization of brilliant green dye in aqueous media using various modified MOF-5 adsorbents

Dye pollution in environmental water is a serious problem worldwide, posing significant environmental and health concerns. To effectively address this problem, this study investigates the adsorptive decolorization of brilliant green (BG) dye in aqueous media by using various metal-organic frameworks (MOF-5)-based adsorbents modified with industrial wastes (coal fly ash (CFA) and rice husk ash (RHA)). The adsorption experiments were conducted to evaluate their performance under varying conditions, and the synthesized and spent adsorbents (selected) were characterized. The results showed that the adsorbent samples possessed the characteristics of a good adsorbent. MOF-5 coated with thermally treated RHA at 900 °C (MOF-5@ RHA900 – with BET surface area = 91.6810 m2 g−1) has the highest observed BG dye adsorption efficiency (92%) and adsorption capacity (30.22 mg g−1) at adsorbent mass of 1.4 g, contact time of 2 h, and initial dye concentration of 20 mg L−1. BG dye removal increased with an increase in contact time and adsorbent amount and decreased with an increase in initial dye concentration. The adsorption kinetics and isotherm equilibrium studies revealed that the adsorption data were best fitted to the pseudo-second-order kinetic model (R2 = 0.9507) and Langmuir isotherm model (R2 = 0. 0.9929), respectively. These findings highlight the potential of mesoporous MOF-5@ RHA900 as an effective adsorbent for BG dye decolorization in aqueous media, with implications for water treatment and the utilization of industrial waste materials.

The efficiency of Raphia hookeri adsorbent in indigo carmine dye removal: Economy depth via chemometrics

The remediation of dye pollutants remains a concern in contemporary water management practices. Hence, the need for efficient and cost-effective techniques for dye removal from wastewater. In this study, the epicarp of Raphia hookeri fruits was treated with orthophosphoric acid for enhanced porosity and efficiency in the uptake of Indigo carmine dye (ICD). Treated Raphia hookeri fruit waste (RHPW) presented morphologically distributed pores as well as high porosity with Branneur-Emmet-Teller (BET) surface area of 945.43 m2/g. RHPW displayed functional groups suitable for adsorption. The maximum ICD uptake was observed at pH 5 while the maximum uptake (qmax) was 20.41 mg/g in the concentration range of 2–10 mg/L. Freundlich isotherm and Pseudo-second order kinetics well-described equilibrium and kinetics data respectively. This indicated a multilayered adsorption. The Dubinin-Radushkecich model energy value was 40.82 kJ/mol, indicating chemical adsorption. The ridge regression, the Lasso and the Elastic net statistical models were used to establish a positive relationship between the various adsorption operational parameters studied. Lasso provided the best result based on the estimated mean squared error. The RHPW-ICD adsorption system was more favorable at room temperature, as the removal efficiency decreased with temperature rise. The findings established Raphia hookeri fruit epicarp as an economical and sustainable precursor for the preparation of potent adsorbent for Indigo carmine dye removal. This can find possible application in wastewater treatment.

Assessment of activated carbon/alginate for the concurrent removal efficiency of paracetamol and caffeine from wastewater in their binary solutions

The increasing amount of pharmaceutical chemicals in wastewater is a concern for both public health and the environment. This research investigates the effectiveness of a new composite material made of alginate-activated carbon in removing caffeine and paracetamol from wastewater simultaneously. The composite material, produced using a simple technique, demonstrates excellent removal rates and exceptional adsorption properties for both medicinal chemicals. The structural stability and integrity of the composite are confirmed through comprehensive characterization methods including scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction, energy dispersive X-ray (EDX), and BET surface area analysis. The study uses batch adsorption experiments to assess the impact of various factors, such as pH, initial concentration, and contact time, on the efficiency of caffeine and paracetamol removal. The highest values for the adsorption process were 89.63% for Paracetamol and 97.32% for Caffeine, achieved under optimal experimental conditions (pH 7, 0.1 g dose of adsorbent at elevated temperature). Additionally, Kinetic studies and thermodynamic parameters such as ΔS°, ΔGº, and ΔH° were calculated, indicating that the adsorption process was endothermic and spontaneous for paracetamol, and exothermic and non-spontaneous for caffeine. Seven non-linear equilibrium isotherm models were utilized to fit the experimental data for paracetamol and caffeine at pH 7 showing maximum adsorption capacities (qmax) of 606.80 and 725.05 mg/g for Paracetamol and Caffeine, respectively with a high regression coefficient (R2) of 0.99 using alginate-activated carbon as an adsorbent, The results demonstrate the potential of alginate-activated carbon as an effective adsorbent for the simultaneous removal of various pharmaceutical pollutants, highlighting the synergistic adsorption effects of the composite material. The study also examines the safety of the composite material, particularly in the context of potential medical applications. The study emphasizes the potential for sustainable and repeated use of the activated carbon/alginate composite, demonstrating that it maintains both its structural integrity and adsorption effectiveness after multiple cycles of use. This study evaluated the suitability of the suggested analytical method using BAGI, a metric with a unique formula. The BAGI is a complementary tool to GAPI, Complex GAPI, AGREE, AGREE prep, and ESA. A major focus is on the practical elements of white analytical chemistry centered around “blue”.

Comparative Study of the Local Vegetable Activated Carbon with Commercial Ones for Adsorption of Methylene Blue

Activated carbons have great applicability in the conditioning of wines: discoloration, removal of foreign taste and smell, correction of organoleptic parameters, etc. The purpose of this work was to compare the structural and sorption characteristics of local vegetal activated carbon obtained from apricot stones (AC-C, Republic of Moldova) with that of commercial activated carbons (Granucol® BI/GE/FA, Germany). The physico-chemical characteristics of studied activated carbons have been evaluated by standard methods (nitrogen sorption isotherms, IR spectroscopy, pH value of activated carbons suspension etc.) and the adsorption capacity by using methylene blue dye as a reference substance. Experimental data were analysed by theoretical models: Langmuir and Equilibrium isotherm models, and pseudo-first-order, and pseudo-second-order kinetic models. The adsorption capacity of the local activated carbon (AC-C, 690 mg/g) is higher by 30% than that of activated carbons from Granucol® series (approx. 535 mg/g).

Isotherm and kinetics study of Ni(II) ions adsorption from wastewater using carbon nanotubes decorated with ZnO nanoparticles

A zinc oxide/carbon nanotube hybrid (ZnO/MWCNT) was synthesized utilizing a straightforward precipitation technique based on the physical approach of pulsed laser ablation. Various techniques were employed to investigate the composition, morphology and optical of the synthesized nanocomposite. The techniques employed were X-ray diffraction, Raman spectroscopy, transmission electron microscopy, FT-IR and thermal gravimetric analysis (TGA) to confirm the compete decoration to be applicable for removal Ni(II) ions in an aqueous solution. ZnO have a hexagonal wurtzite structure connected to hexagonal graphite of MWCNT from XRD. The interaction between ZnO and CNTs resulted in a reduction in the domain of sp2 bonds, according to Raman. From TGA, we can attribute the reduction in thermal analysis to the oxidation of surface hydroxyl functional groups (-OH), the evaporation of surface solvent and the presence of ZnO’s inorganic oxide structure compared to pristine MWCNT. These findings confirmed that adding ZnO NPs to MWCNT caused more structural flaws and surface disorder, even though the structure of the CNTs stayed the same. We then investigated numerous factors affecting the extraction of Ni(II) ions, including pH, duration of extraction, amount of nanosorbent used and circumstances. We observed the optimal conditions at room temperature, pH of 5.9, nanoadsorbent dosage of 0.2 g/L and contact time of 1 h. Atomic absorption spectrometry easily monitored the kinetics of this reaction. The Langmuir, Freundlich and Redlich–Peterson isotherm models explain the mechanism underlying the adsorption equilibrium isotherm. Furthermore, regeneration experiments revealed that the adsorbent still maintained a high adsorption capacity after six cycles, demonstrating remarkable potential for use in environmentally friendly applications.

Functionalization of Strontium Ferrite Nanoparticles with Novel Chitosan–Schiff Base Ligand for Efficient Removal of Pb(II) Ions from Aqueous Media

Lead contamination in water poses significant health risks, making its removal imperative. In this study, magnetic strontium ferrite (SrFe12O19) nanoparticles were facilely synthesized by the Pechini sol–gel method and subsequently functionalized with a novel chitosan–Schiff base ligand to obtain a novel inorganic/organic nanocomposite for removing Pb(II) ions from aqueous solutions. The chitosan–Schiff base ligand was synthesized through the reaction of chitosan with 2,4,5-trihydroxybenzaldehyde. The presence of two X-ray diffraction (XRD) peaks at 2Ɵ = 10.5° and 2Ɵ = 20.5°, alongside the characteristic SrFe12O19 peaks, confirmed the functionalization of the nanoparticles with the ligand. Additionally, a significant decrease in the saturation magnetization value from 40.29 emu/g in pure SrFe12O19 nanoparticles to 17.32 emu/g in the nanocomposite further verified the functionalization. The presence of carbon (C) and nitrogen (N) atoms in the energy-dispersive X-ray (EDX) pattern of the nanocomposite, in addition to iron (Fe), strontium (Sr), and oxygen (O), also confirmed the functionalization. The nanocomposite’s maximum adsorption capacity for Pb(II) ions was 390.63 mg/g. Moreover, the adsorption process is endothermic, spontaneous, and chemical, occurring via complexation with -C=N and -OH groups, and it fits well with the Langmuir equilibrium isotherm and the pseudo-second-order kinetic equation.

Evaluation of gold adsorption on activated carbon from real cyanide and thiourea leachate solutions

The recovery of gold by adsorption using activated carbon from sodium cyanide and thiourea leached solutions are reported in this study. The leached solutions were obtained under real operating conditions from the beneficiation plant “Paz Borja”, Machala-Ecuador. Calgon Carbon DG-11 6X12 type, widely used in the local metallurgical industry was used as adsorbent material. The operational parameters varied during the adsorption process experiments included the concentration of leaching agent, agitation speed, dose of activated carbon and initial concentration of gold. The control parameters included density, percentage of solid, pH, temperature, and solution potential. The obtained results were adjusted to mass transfer model by diffusion through the interface and the Freundlich model for the equilibrium isotherms. The analysis of the results indicates a higher adsorption rate of the gold di-cyanide complex on activated carbon compared to gold-thiourea complexes.

Enhanced Hg(II) removal using thiourea-functionalized graphene oxide: Lab to pilot scale evaluation

Here, a thiourea-formaldehyde functionalized graphene oxide (G3DTF) is shown to effectively remove mercury (Hg) from various water sources, including ultrapure, bottled, and seawater. Over 99 % of the Hg in each water source is removed with only 10 mg/L of G3DTF resulting in a residual Hg concentration < 1 μg L−1. This concentration falls within the permissible limits established by the European drinking water guidelines. Notably, the presence of chlorocomplexes in seawater does not reduce the sorption efficiency of G3DTF. The sorption process across all water matrices can be accurately described by pseudo-second-order kinetics, with an R2 > 0.99 suggesting chemical interactions between Hg ions and G3DTF functional groups. The equilibrium isotherms demonstrate a remarkably high maximum adsorption capacity (qm) of 1039 mg g−1, exceeding the values reported in literature for the sorption of Hg on carbon-based materials. Remarkably, G3DTF retains its performance in the presence of other metal ions such as Cu, Cd, and Pb. Incorporating G3DTF into commercially activated carbon (AC) at a concentration as low as 2 wt % significantly enhances the efficiency of Hg(II) removal in fixed bed adsorption. The breakthrough curve exhibits enhanced absorption, attaining a 99.7 % removal of Hg(II) within a span of 2 h, surpassing the efficiency of AC. This relevant result represents a substantial advancement towards the adoption of graphene-based nanocomposites as effective commercial remediation materials.

Management of caffeine in wastewater using MOF and perovskite materials: optimization, kinetics, and adsorption isotherm modelling

Pharmaceuticals and personal care products (PPCPs) have been increasingly used all over the world and they have been reported on water cycle and cause contamination. Among these pharmaceuticals is caffeine (CAF). In this work, CAF removal from aqueous samples by metal–organic framework (UIO-66) and perovskite (La0.7Sr0.3FeO3) was achieved. Detailed studies on the preparation of MOFs and perovskite oxides compounds have been presented. Extensive characterizations such as X-Ray diffraction (XRD), field emission scanning electron microscope (FESEM), Fourier transform infrared spectra (FT-IR), N2 adsorption–desorption isotherms were also carried out to assure proper formation and to better understand the physico-chemical behavior of the synthesized samples before and after adsorption. Batch experiments of CAF adsorption onto both MOFs and perovskite were performed to compare the effectiveness of both materials on the removal competence of the CAF residue at different conditions including the effect of pH, initial concentration, and contact time. It was observed that the adsorption capacity of CAF by MOF increased with increasing acidity. On the other hand, the adsorption capacity of perovskite is stable in pH 4–10. The maximum adsorption capacities of UiO-66 and perovskite toward CAF are high as 62.5 mg g−1 and 35.25 mg g−1, respectively. Equilibrium isotherms were investigated by numerous models: Langmuir, Freundlich, Temkin, Redlich-Peterson, Sips, Langmuir-Freundlich, Toth, Kahn, Baudu, and Fritz Schlunder. Moreover, the kinetics of the CAF@MOF and CAF@Perovskite systems have been studied by five kinetic models (Pseudo-1st -order (PFO), Pseudo-2nd -order (PSO), Mixed 1st, 2nd-order, Intraparticle diffusion and Avrami). The best model described the adsorption of CAF onto both of MOF and perovskite was the mixed 1st, 2nd-order model. The metal–organic framework and perovskite were applied to quickly extract CAF from water samples successfully. The maximum removal percentage obtained for MOF and perovskite was 0.89% and 0.94% respectively within 30 min contact time which suggests that these materials are considered as promising adsorbents for CAF.

Adsorption of the rare earth elements cerium, lanthanum, and neodymium onto ZSM-5 zeolite: A statistical physics approach

The recovery of rare earth elements (REE) is essential to meet the growing demand for these resources and promote the reuse of available resources. This study investigated the potential of ZSM-5 zeolite in the recovery of trivalent ions of cerium, lanthanum and neodymium under conditions of pH 6 and temperatures between 298 and 328 K. REE equilibrium isotherms were analyzed using five statistical physics models. The results indicate that removing all REE occurs predominantly in monolayers, as these models showed better prediction performance (coefficient of determination > 0.97 and mean squared error < 18.0). The best model determined that lanthanum and neodymium have one adsorption energy, while cerium has two adsorption energies involved in the process. The predominant functional groups are those containing silicon. Increasing temperature causes an increase in the number of REE ions captured per functional group, which reduces the adsorption space available on the surface. The model parameters indicate that the adsorption of these ions implies a multi-ionic mechanism (number of ions adsorbed per site greater than 1) and is an exothermic process. Based on the calculated adsorption capacities at saturation, the order of preference in adsorption can be established: neodymium > cerium > lanthanum. The adsorption energies indicate that the process occurred mainly due to physical forces since all energy values are below 40 kJ mol−1. The study’s results led to the proposal of a mechanism for the adsorption of REE on ZSM-5 zeolite, which highlights the predominance of electrostatic interactions and complex formation, which result in the formation of a monolayer on the adsorbent’s surface.

Mechanistic Understanding of Sieving Lithium Ions Using a Biobased Sorbent Technology for Sustainable Lithium Reclamation and Cleansing Brines.

Low-cost environmentally benign materials that can be produced in a large scale to extract lithium from brine resources could drive the lithium market toward a clean technology with high lithium recovery and production. Herein, we have investigated the utilization of a novel, environmentally benign, and low-cost biobased sorbent for the extraction of lithium from lithium-rich solutions. This biobased molecular sieving sorbent, iron(III)-tannate (Fe(III)-TA), belongs to a novel class of coordination polymer frameworks derived from a natural polyphenol-tannic acid (TA)-coordinated with iron(III) metal cations. Its lithium adsorption and kinetic isotherm studies conducted using lithium-rich aqueous solutions confirm the sorbent's dual function for lithium sieving via physisorption, chemisorption, and mass transfer diffusion processes. The adsorption equilibrium and kinetic isotherm models combined with the external and internal mass transfer diffusion models reveal a mechanistic pathway for lithium-ion adsorption. Aiding by forming a fluid film for external mass transfer diffusion of lithium ions, analytes adsorb onto the sorbent surface via physisorption and chemisorption followed by the internal mass transfer diffusion, occupying lithium ions in the sorbent's pores. The lithium adsorption efficiency studies conducted for brines with different concentrations of interference alkali and alkaline cations evidence that the sorbent's affinity for lithium ions strongly depends on the analyte concentration. The results evidence that the sorbent has the ability to lower the brine's salinity and significantly reduces the ratios of Mg/Li and Ca/Li by 4-fold and 10-fold, respectively, yielding lithium-rich solutions. Thus, implementing this innovative biobased sorbent technology as an add-in step into traditional lithium extraction and refining processes, one can design a cost-effective pathway to yield lithium-rich leachate by reducing the Mg/Li and Ca/Li ratio. Nonetheless, the present work demonstrates that Fe(III)-tannate is an effective multifunctional sorbent for sieving lithium from lithium-rich aqueous solutions as well as for desalinating brine resources to recover usable water. Thus, this biobased sorbent offers the possibility of effective application of lithium reclamation and remediation of brine, mitigating the environmental impact of brine discharge and large volume of freshwater usage for lithium extraction and refining.

Efficient removal of heavy metal ions by modified cellulose prepared from rice husk: Equilibrium isotherms, Kinetics and desorption studies

The cellulose acetate was prepared from the naturally occurring cellulose extracted from rice husk. It was then characterized using FTIR, XRD, SEM/EDS, TEM and BET and the results were connected to their potential applications in the elimination of heavy metal ions. Differential pulse voltammetry was used for quantitative study of heavy metal ions. An adsorption experiment was conducted to study the effect of temperature, initial concentration, adsorbent dosage, pH and contact time on the adsorption capacity of cellulose acetate. The results of the adsorption experiment showed that the removal of metal ions from adsorbent was a pH-dependent, reaching its maximum adsorption capability at pH of 5-6. Adsorption process was effective with adsorbent dosage was 10±0.1 mg/mL and the temperature was kept at 303K. The adsorption properties of cellulose acetate can be effectively described by pseudo-second-order kinetic with lower error function value and adsorption isotherm such as Freundlich and Temkin adsorption model at 50 min contact time and 50±0.1 mg/L initial concentration. The thermodynamic parameters were investigated, they shows adsorption is favorable at low temperatures. Desorption and re-adsorption of the heavy metals were also studied. Cellulose acetate still retains its adsorption efficiency up to 6th cycles of adsorption.

A contribution to understanding ion-exchange mechanisms for lithium recovery from industrial effluents of lithium-ion battery recycling operations

Industrial effluents or process waters generated from spent lithium-ion battery recycling operations often contain high concentrations of lithium ions (Li+). This study characterizes the composition of process water obtained from pre-treatment and concentration operations of LIBs recycling. Ion-exchange experiments are conducted using synthetic lithium solutions (1 g/L) and industrial waters to understand Li+ recovery. Employing four commercial cationic resins, fast Li+ exchange kinetics are observed fitting the pseudo-second order model. The equilibrium isotherm data corresponds to the Langmuir adsorption model and reveals a Li capacity of 30–32 mg/g using Amberlite™ IRC 120 H, 70 mg/g using Lewatit® TP 308 H, 37–40 mg/g using Lewatit® TP 208 Na, and 37–41 mg/g using Lewatit® TP 260 Na. While the resins initially demonstrate moderate affinity for Li+, this can be significantly enhanced by increasing the Li+ concentration. Notably, as LIBs recycling operation effluents typically contain minimal competing ions, these results underscore the potential of employing ion exchange as a viable method to recover and concentrate lithium before precipitation into lithium salts.

Bioremediation potential of microalgae for copper ion from wastewater and its impact on growth and biochemical contents: equilibrium isotherm studies

The use of microalgae to remediate heavy metal-contaminated wastewater has attracted more and more interest. In this investigation, the green microalgae Chloroidium ellipsoideum and Desmodesmus subspicatus were used to study copper uptake from nutrient media and its effect on algal growth and metabolism. The growth of C. ellipsoideum and D. subspicatus generally decreased with increasing copper concentrations. There was a decrease in the carbohydrate content of C. ellipsoideum, but an increase was observed in D. subspicatus by treatment with various copper concentrations. Low concentrations of copper helped to increase the protein content of C. ellipsoideum, but a decline in protein content was reported for D. subspicatus. By increasing the copper concentrations, an increase in the free amino acids and a decrease in the total lipid content of C. ellipsoideum and D. subspicatus were recorded. At 0.1 mgl–1 copper concentration, pH of 6.8, and algal dose of 1 g L−1, the maximum biosorption capacity of C. ellipsoideum was 0.398 mg g−1, corresponding to the maximum reduction of 68.66% of Cu2+, and 0.396 mg/g for D. subspicatus, corresponding to the maximum reduction of 59.52%. The Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models were applied to describe the isothermal biosorption of Cu2+ ions in studied algae. The Dubinin–Radushkevich model indicated that the copper biosorption mechanism was physical in nature. Cu2+ has a greater affinity for D. subspicatus than C. ellipsoideum, suggesting that C. ellipsoideum was relatively more resistant to Cu2+ toxicity than D. subspicatus. Moreover, FT-IR analysis revealed that carboxyl, amide, amino, carbonyl, hydroxyl, methyl and alkyl groups were the key groups responsible for the biosorption process. Therefore, D. subspicatus and C. ellipsoideum are efficient biosorbents for Cu2+ and can be used as biosorbents for heavy metals removal from wastewater.

Evaluation of the CH4/CO2 separation by adsorption on coconut shell activated carbon: Impact of the gas moisture on equilibrium selectivity and adsorption capacity

Upgrading biogas to biomethane is of great interest to change the energy matrix by feeding the renewable fuel produced from biomass waste into natural gas grids or directly using it to replace fossil fuels. The study aimed to assess the adsorption equilibrium of CH4, CO2, and H2O on a coconut-shell activated carbon (CAC 8X30) to provide data for further studies on its efficiency in upgrading biogas by Pressure Swing Adsorption (PSA). The adsorbent was characterized, and equilibrium parameters were estimated from monocomponent CH4, CO2, and H2O equilibrium isotherms. Binary and ternary equilibrium isotherms were simulated, and the selectivity and adsorption capacity of the CAC 8X30 were calculated in dry and wet conditions and then compared with zeolite 13X as a reference material. Regarding characterization, Nitrogen and Hydrogen Physisorption results indicated that 94 % of the pore volume is concentrated in the region of micropores. The adsorption affinity with CAC 8X30 estimated from monocomponent isotherms was in the order KH20>KCO2>KCH4. IAST-Langmuir model simulations presented good agreement with experimental binary equilibrium data. Further simulations indicated equilibrium selectivity for CO2 over CH4 (e.g., 4.7 at 1 bar and 298 K for a mixture of CH4/CO2, 60/40 vol%), which increased in the presence of moisture, indicating its suitability for upgrading humid biogas. Simulations for zeolite 13X suggested that the material is unsuitable in the presence of water vapor but presents higher selectivity than the CAC 8X30 in dry conditions. Hence, the integration of both materials might be helpful for biogas upgrading.

Two step synthesis and application of porous carbon for removal of copper (II) from wastewater: Statistical optimization and equilibrium isotherm analysis

In this study, activated carbon (ACs) adsorbent was synthesized using the lignocellulosic waste (LCB) seed from Adansonia digitata L. (BSP) using two steps of hydrothermal carbonization (HTC) followed by activation. The hydrothermally produced char of BSP was activated to produce porous activated carbon BSPAC, where K2CO3 was used as a chemical activating agent. Box Behnken Design was used to optimize the input variables of pyrolysis temperature (A1), residence time (B1), and ratio (C1) for the pyrolysis process. Removal percentage (β1), percentage carbon yield (β2), and fixed carbon (β3) percentage were chosen as output responses. The analysis of variance was utilized to generate appropriate mathematical models with subsequent statistical analysis. Physiochemical characterizations were carried out for the hydrothermally carbonized sample (BSPC) and the optimized activated sample (BSPAC). Langmuir, Freundlich, and Temkin models were employed to estimate the isotherm model parameters. The results demonstrated that HTC with subsequent mild activation using K2CO3 can be considered as a greener route to obtain better-quality porous carbon having surface area of 599 m2/gm for removal of Cu(II) cations from wastewater.

Studying removal of anionic dye by prepared highly adsorbent surface hydrogel nanocomposite as an applicable for aqueous solution

In this study, a Sodium alginate-g-poly (acrylamide-clay)/TiO2 hydrogel nanocomposite [SA-g-p(AM-Bn)/TiO2] was synthesized using the biopolymer sodium alginate (SA), acrylamide (AM), and bentonite clay (Bn) as hybrid materials embedded with titanium dioxide nanoparticles (TiO2NPs) for the removal of toxic Congo Red (CR) dye from an aqueous solution. The [SA-g-p(AM-Bn)/TiO2] nanocomposite has been described on the basis of thermal stability, morphological analysis, estimation of functional group, and crystalline/amorphous character by TGA, EFSEM/EDX, TEM, FT-IR, and XRD analysis, respectively. The effects of operational parameters toward the CR dye adsorption on [SA-g-p(AM-Bn)/TiO2], including contact time, adsorbent dosage, initial concentration, initial pH, and temperature were investigated. The maximum adsorption efficiency was found to be 185.12 mg/g for [SA-g-p(AM-Bn)/TiO2] in 100 mg/L of solution CR at pH 6.0 within 1 h. The equilibrium isotherms, kinetics, and thermodynamics parameters of adsorption were examined, and results showed that the isotherm fitted the Freundlich model and the kinetics adsorption model of CR followed pseudo-first-order, thus indicating physisorption of anionic-CR onto the sorbent due to the development of an electrostatic attraction bond. Thermodynamic parameters for [SA-g-p(AM-Bn)/TiO2] have values (ΔG and ΔH) reflecting the spontaneous and endothermic nature of the adsorption processes. Moreover, [SA-g-p(AM-Bn)/TiO2] presented outstanding excellent reusability and recyclability with a relatively best removal percentage as compared to [SA-g-p(AM-Bn)] and suggested their applicability towards the textile industry and water purification purposes.

MnFe2O4-NH2-HKUST-1, MOF magnetic composite, as a novel sorbent for efficient dye removal: fabrication, characterization and isotherm studies

Dye in industrial wastewater is one of the most serious environmental concerns due to its potentially harmful effects on human health. Many industrial dyes are carcinogenic, toxic and teratogenic. Removal and recovery of hazardous dyes from the effluents requires efficient adsorbents. In this study, magnetic adsorbent MnFe2O4-NH2-HKUST-1 was synthesized to remove methylene blue and crystal violet dyes from aqueous solutions. The synthesized adsorbent was characterized using FTIR, XRD, BET, VSM, SEM, TGA and Zeta potential techniques. The effect of different parameters such as pH, contact time, and adsorbent dosage on the removal of dyes was investigated. The dye adsorption process was investigated by UV–Vis spectrophotometry. The maximum adsorbent capacity was obtained as 149.25 mg/g for methylene blue and 135.13 mg/g for crystal violet. The adsorption equilibrium isotherm and kinetic models were plotted and results showed that the adsorption process for both dyes is a collection of physical and chemical adsorption based on langmuir and freundlich isotherm models, and follows the pseudo-second-order adsorption kinetics. This study shows that magnetic adsorbent MnFe2O4-NH2-HKUST-1 has a good potential for removal of methylene blue and crystal violet dyes from water in a short time (5 min) and it is easily separated from the solution by a magnetic field due to its magnetic property.

Functionalization of Na2Ca2Si3O9/Ca8Si5O18 Nanostructures with Chitosan and Terephthalaldehyde Crosslinked Chitosan for Effective Elimination of Pb(II) Ions from Aqueous Media

Lead poses significant health risks to humans, including neurological and developmental impairments, particularly in children. Additionally, lead pollution in the environment can contaminate soil, water, and air, endangering wildlife and ecosystems. Therefore, this study reports the straightforward fabrication of Na2Ca2Si3O9/Ca8Si5O18 nanostructures (NaCaSilicate) utilizing a sol-gel technique. Additionally, the produced nanostructures underwent further modification with chitosan (CS@NaCaSilicate) and chitosan crosslinked with terephthalaldehyde (CCS@NaCaSilicate), resulting in new nanocomposite materials. These samples were developed to efficiently extract Pb(II) ions from aqueous media through complexation and ion exchange mechanisms. Furthermore, the maximum adsorption capacity for Pb(II) ions by the NaCaSilicate, CS@NaCaSilicate, and CCS@NaCaSilicate samples is 185.53, 245.70, and 359.71 mg/g, respectively. The uptake of Pb(II) ions was characterized as spontaneous, exothermic, and chemical, with the best description provided by the Langmuir equilibrium isotherm and the pseudo-second-order kinetic model. Furthermore, a 9 M hydrochloric acid solution effectively eliminated Pb(II) ions from the synthesized samples, attaining a desorption efficacy surpassing 99%. Additionally, the fabricated samples exhibited efficient reusability across five successive cycles of adsorption and desorption for capturing Pb(II) ions.

Numerical simulation of foam displacement impacted by kinetic and equilibrium surfactant adsorption

This study explores the effectiveness of foam in reducing gas mobility in porous media impacted by surfactant adsorption in highly heterogeneous porous media. The research focuses on assessing the influence of kinetic and equilibrium adsorption during foam displacement on reservoir sweep efficiency, considering co-injection and SAG (Surfactant Alternating Gas) injection strategies. Including the surfactant on the liquid phase and considering the surfactant adsorption effects fitted by experimental data, the mathematical modeling combines Darcy’s law, fluid phase conservation, surfactant transport equations, and a non-Newtonian foam model in local equilibrium. The simulations utilize FOSSIL (FOam diSplacement SImuLator), an in-house software composed of a stable and conservative numerical algorithm with reduced numerical diffusion. These properties are achieved by combining a hybrid mixed finite element method to solve the Darcy system with a central-upwind finite volume scheme to approximate the transport equations and adopting an implicit adaptive method in time. The results reveal that while omitting adsorption phenomena enhances sweep efficiency due to reduced surfactant loss, differences between equilibrium and kinetic adsorption models are minor (up to 0.3% in production). Consequently, these results suggest using simple adsorption models, such as equilibrium isotherms, rather than more complex models, such as kinetics. Additionally, the SAG approach outperforms co-injection (up to 19% in production), despite the fact that the adsorption is detrimental to both of them, aligning with literature results and previous findings.