Langmuir Parameters Research Articles

Effect of Low Molecular Weight Organic Acids and Liming on Phosphorus Adsorption in Acidic Tea Soils in the Black Sea Region, Türkiye

ABSTRACT Agricultural productivity is significantly hindered by the limited availability of phosphorus in acidic soils due to the presence of aluminum and iron phosphates. Soil liming is commonly employed to enhance soil fertility. However, modifying the pH might also impact the interactions involving existing soil organic matter, leading to changes in the effective concentrations of competing low-molecular-weight acids (LMWOACs) participating in phosphorus adsorption. This study explored the impacts of citric, oxalic, and malic acids in acidic soils from tea cultivation regions within the Eastern Black Sea. These soils had undergone various levels of liming and were incubated for 15 months to assess their effects on phosphorus (P) adsorption in 7 acidic soils. The experimental sorption data were utilized to calculate the soil Langmuir and Freundlich adsorption parameters. In addition, the influences of organic acids and liming levels on the Freundlich and Langmuir model parameters were subjected to ANOVA analysis. The findings indicated that citric acid demonstrated the highest efficiency in diminishing phosphorus adsorption among the tested organic acids, followed by oxalic and malic acids. Three carboxyl groups (−COOH) in citric acid facilitated the formation of more complexes with adsorbed phosphorus on the soil surface. Furthermore, the 100% LR ratio of liming notably decreased phosphorus adsorption, especially in the lower end of the isotherms. Therefore, it can be concluded that the combination of LMWOACs and liming treatments could be used to overcome P deficiency in acid soils with very high P sorption ability.

Adsorption and estimation of As (III) from wastewater using cross linked Chitosan-STPP nanoparticles with voltammetric analysis computrace, isotherms, and kinetic study

Chitosan (CS) is a naturally occurring polycationic linear amino polysaccharide produced commonly through the deacetylation of chitin. This study describes the synthesis of Chitosan (CS) modified with sodium tripolyphosphate (STPP) using an efficient coated Cross-linked method. The study investigated the efficacy of chitosan-tripolyphosphate (CS-STPP) nanoparticles for the efficient adsorption of As (III) ions from a wastewater solution. The effect of initial Arsenic (III) ion concentration, solution pH, and temperature on adsorption efficiency was thoroughly investigated. The highest adsorption capacity of CS-STPP nano adsorbents for As (III) was found to be 39.8 mg/g and 39.6 mg/g, respectively, at pH 5.5, and a temperature of 30 °C. The FESEM, SEM, HRTEM, XRD, FTIR, DLS, and TGA results indicated that the adsorption process of As (III) was chemically dominating. As (III) Determine with the anodic linear sweep voltammetry 797 VA Computrace (Metrohm). The Langmuir parameters of 40.9 mg/g and 1000 L/mg were found for maximum adsorption capacity, which indicated monolayer adsorption on a homogeneous site, Freundlich isotherm is applicable for multilayer adsorption onto heterogeneous sites. The thermodynamic study showed that the adsorption of As (III) by CS-STPP was spontaneous, feasible, and exothermic at temperatures ranging from 30 °C to 50 °C. The kinetic model indicated that the adsorption processes persist well to the pseudo-second-order kinetics model. The reaction is suitable for a pseudo-second-order model, it indicates an inclination for chemisorption. Adsorption-desorption processes are determined efficiency of bio adsorbent by several physicochemical cycles. All results indicate that the prepared CS-STPP nanoparticles might be considered a cost-effective adsorbent for removing As (III) from wastewater.

Effects of humic acid and mineral Zn fertilizer on Zn uptake and maize yield in soils formed on limestone and marl parent materials

In this study, the effects of zinc (Zn) and humic acid (HA) applications on soils (12 Aridisol soil samples) formed on limestone and marl parent materials, which are very common in Türkiye, were tested by incubation, adsorption, and greenhouse experiments. Adsorption experiments were carried out using the batch sorption technique, and the Langmuir and Freundlich isotherm parameters were calculated. In the incubation, soils were incubated with control, HA, Zn, and HA+Zn, and the DTPA-Zn was tested in five different periods (1, 7, 15, 30, and 90th days). Maize was grown for eight weeks in pots in the greenhouse. The maximum Zn adsorption for all soils ranged between 3333 and 6250 mg kg-1 in marl soils and 1042 and 5263 mg kg-1 in limestone soils, which decreased to ranges between 2631 and 5555 mg kg-1 in marl soils and 1052 and 5000 mg kg-1 in limestone soils with HA appli-cation, respectively. The desorption rate (%) of adsorbed Zn increased as the initial Zn concentration increased in all soil series formed on marl (smectite clay mineral) and lime-stone (kaolinite clay mineral) parent materials. The effects of humic acid and Zn applica-tion on the fresh and dry weights of maize were found to be statistically significant at the 5% level for marl and limestone parent material. Humic acid application increased the fresh weight of maize compared with that of the control. The highest available Zn was determined in Başkuyu series (0.79 mg kg-1) formed on marl parent material, while the lowest available Zn was obtained in Saraççeşme series (0.60 mg kg-1) formed on limestone parent material. In the greenhouse, HA increased the fresh weight of maize in soils formed on both parent materials by 0.4 and 19.6%, respectively, compared to the control. Zn fertili-zation with HA further increased the fresh and dry yields, with 12 mg kg-1 performing bet-ter. Smax (maximum Zn adsorption of the soil) parameters of soils were negatively corre-lated with EC, Pav, Kav, organic matter, silt, clay, total N, and cation exchange capacity (CEC) of the samples. Although HA alone increases the availability of Zn in plants, HA + Zn appli-cations should be applied together to obtain higher yields.

Reactive Blue 19 Adsorption on Activated Carbon From Pumpkin (Cucurbita Pepo) Seed Waste: Kinetic, Isotherm and Thermodynamic Studies

In this study, the removal of Reactive Blue 19 dyestuffs in aqueous systems was investigated by adsorption method using activated carbon obtained from the pumpkin seed waste. Activated carbon obtained from pumpkin seed waste functionalized with ZnCl2 was used as an absorbent. Pumpkin seed hydrochar was characterized by FT-IR, SEM, TGA-DTA, BET, and XPS. In the experimental stages, the adsorption equilibrium time was determined as 45 minutes, the adsorbent dosage was 0.8 g and the optimum pH was 6.0. After this step, the adsorption parameters of Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms were investigated. It has been pointed out that the adsorption process fits better with the Freundlich isotherm model, and the adhesion occurs in a multilayered manner and on a heterogeneous surface. Freundlich and Dubinin-Radushkevich isotherms support that the bonding mechanism is realized by physical interactions. When the kinetic data were evaluated, it was found to be compatible with the pseudo-second-order kinetic model. The thermodynamic parameters of adsorption indicate that the system is endothermic, and the adsorption of Reactive Blue 19 on activated carbon is a spontaneous process.

Cu-ZSM-5 catalyst synthesis via ion-exchange with ammonia solution of copper hydroxysalts

The properties of dihydroxycarbonate (malachite) and trihydroxynitrate of copper were studied in order to apply their ammonia solutions for the synthesis of copper-substituted ZSM-5 zeolites. Copper concentration and NH4OH/Cu2+ ratio in the solutions varied 1–12 g/l and 6–30, respectively. The parameters of Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherms revealed the favorability of the chosen conditions and the chemical nature of [Cu(NH3)n]2+ ions sorption by zeolite. For both copper salts, the sorption capacity of H-ZSM-5 for Cu2+ ions was higher in the solutions having NH4OH/Cu2+ = 6–10 compared to 30. To identify the synthesis and structure – activity relationship correlations, the ammonia solution and Cu-ZSM-5 samples were characterized by EPR, UV–visible spectroscopy, temperature-programmed reduction by hydrogen (H2-TPR). The calcined Cu-ZSM-5 samples produced at NH4OH/Cu2+ = 6–30 contained two types of the isolated Cu2+ ions (bare Cu2+ and [Cu(OH)]+), differing in their Redox properties. Their reducibility improved with an increase in the copper loading and with a decrease in NH4OH/Cu2+. At NH4OH/Cu2+ = 6–10, the samples additionally comprised the structures of Cu2+ ions with extra-lattice oxygen (ELO), which were formed due to hydrolysis of [Cu(NH3)n(H2O)]2+ to [Cu(NH3)n(OH)]+ and then to [Cu(OH)2Cu]2+. Cu2+–ELO structures possessed a greater ability to complete reduction than both types of isolated Cu2+ ions. Correlations with DeNOx properties in selective catalytic reduction (SCR) of NO by propane and ammonia are discussed.

A facile one-pot synthesis of Ag2Te nanoparticles and the fabrication of nanocomposites for the removal of chromium (VI) in wastewater

The sol–gel method has been used successfully for the preparation of crystalline PVA-Ag2Te nanoparticles at room temperature using water as a solvent, PVA as a capping agent, sodium borohydride as a reducing agent, telerium, and silver nitrate as a source of silver. The synthesized PVA-Ag2Te were then incorporated with chitosan to form the nanocomposites for the removal of Cr(VI) ions from wastewater. A blue shift in the wavelength was observed with an energy band gab between 2.76 eV and 2.82 eV when the PVA was added into the nanoparticles. The morphology and structural studies of the particles were carried out using transmission electron microscopy (TEM) and powder-X-ray diffraction (XRD). The XRD patterns of the Ag2Te projected a pure monoclinic phase whereas TEM images showed agglomerated spherical shaped particles that were improved when the stabilizers was introduced into the nanomaterial with the average particle sized between 8.77 and 9.12 nm. The adsorption process was able to verify that the parameters such as pH, contact time, and initial concentration had a huge impact on water treatment processes. The essential parameters of Langmuir and Freundlich adsorption isotherms were successively utilized to analyze the adsorption mechanism. This was accomplished by combining the isotherms equation with mass conservation of solute before and after adsorption.

Investigation of Adsorption Isotherm Models for Interaction of P(AAm-ClAETA) and Carminic Acid, and Theoretical Approaches

In this study, the adsorption isotherm models for the sorption of carminic acid on P(AAm-ClAETA) hydrogels are explained by experimental and theoretical studies. The crosslinked hydrogels with ethylene glycol dimethacrylate were prepared by radical addition reaction of acrylamide (AAm) and 2-(acryloyloxy)ethyl trimethylammonium chloride (ClAETA) monomers in an aqueous solution. The spectral and morphological analyses of P(AAm-ClAETA) hydrogels were performed by FTIR/ATR and SEM, respectively. The adsorbed amounts of carminic acid on P(AAm-ClAETA) hydrogels were evaluated by Giles, Langmuir, and Freundlich adsorption isotherm models. Langmuir parameters were calculated for the adsorption of the dye on the hydrogels according to the L-type Giles isotherm. In addition, it was determined that its adsorption was appropriate from the RL values calculated for 500 mg L-1 carminic acid concentration. In addition, molecular electrostatic potential (MEP) mapping was performed to predict the reactive sites of P(AAm-ClAETA) hydrogels and carminic acid. The results showed that the theoretical and experimental data of the hydrogels were in agreement with each other. As a result, it can be said that P(AAm-ClAETA) hydrogels are suitable for the removal of anionic dyes such as carminic acid from aqueous solutions.

The Adsorption of Eriochrome Black T onto the Activated Carbon Produced from Pepper Stalks

The aim of this paper is to present the evaluation of the adsorption of Eriochrome Black T (EBT) on the activated carbon (trH-BS) produced from pepper stalk by activating with 50% phosphoric acid solution (H3PO4) and then by carbonizing at 650 oC for 30 min. in atmosphere of nitrogen (N2) was presented. The isotherm of trH-BS was Type IV, representing micro, meso and macroporous structures. The micropore volume and micropore surface area values of trH-BS were 0.39 cc/g and 1107.294 m2/g, respectively. Also, its meso and macropores had a volume of about 15-17 cc/g and an average surface area of 400 m2/g. The adsorption energy was 18.156 kJ/mol and the BET surface area was 756.257 m2/g. Depending on Langmuir parameters, monolayer capacity was determined as 55,56 mg/g. the enthalpy change was calculated as 30.78 kJ/mol. The structure of trH-BS was clarified structurally and morphologically and the formations like nano rod were seen at Scanning Electron Microscopy (SEM) images. By using trH-BS, the adsorption of EBT from the aqueous medium was investigated using 5 different parameters. As a result, it was found that the adsorbents obtained from pepper stalks are suitable for use in EBT adsorption with a ratio of about 50% under suitable conditions.

Equilibrium, kinetics, and thermodynamics of batch adsorption of Mn(II) ions on blast furnace slag (BFS) and kaolin (KGA)

This article describes the discontinuous adsorption of Mn(II) on kaolin from Guelma, Algeria (KGA), and blast furnace slag from Sider, Algeria (BFS), under the effect of various parameters, namely the contact time, the stirring speed, the pH of the medium, the solution temperature, the adsorbent dosage, the solid particle size, and the initial concentration. Also studied were the models of adsorption, namely the isotherms of adsorption, the kinetics of adsorption, and the thermodynamic study of Mn on the examined adsorbents. Characterization tests have indicated that kaolin consists essentially of hydrated aluminum silicate. The BFS is mainly composed of silicates, aluminates, lime, and magnesium oxide. The specific surface areas of kaolin and BFS calculated using the BET were defined at 134.2 and 238.6m2/g. The adsorption rate of Mn(II) on KGA and BFS is better after 50 and 60 min of contact at Vag: 150 rpm; pH: 5.2; Øs: 100 μm; T: 20 °C; Ms: 1 g, respectively. Maximum adsorption capacities are 36.76 mg/g (KGA) and 59.88 mg/g (BFS). Examination of the adsorption isotherms revealed that the Langmuir model is more appropriate to the experimental data (R2 = 0.99). The values of the Freundlich (n), Langmuir (RL), and Temkin (bt) parameters indicate that the adsorption is favorable. The kinetic examination demonstrated that the pseudo-second-order kinetic model is more adopted for the adsorption of Mn(II) on KGA and BFS (R2 = 0.99). Furthermore, the transfer of Mn(II) from the solution to the surfaces of the investigated adsorbents is controlled by external and internal diffusion. The thermodynamic study brought to light that the adsorption processes carried out were spontaneous, exothermic, and less entropic. This work showed that KGA and BFS can be used as low-cost adsorbents for the removal of Mn(II) ions in aqueous media, and BFS has higher affinities for manganese ion adsorption.

Temperature influence on layered double hydroxide tailored corncob biochar and its application for fluoride removal in aqueous media

Exposure to excess fluoride is a controversial public health concern as it can cause dental/skeletal fluorosis as well as renal toxicity. The study intended to evaluate the synergistic interaction of clay intercalation and thermochemical modification on corncob biochar to remove fluoride from aqueous solutions. Layered double hydroxide was assorted with thermally activated (torrefaction and pyrolysis) corncob biochar at 1:1 (w/w) ratio to obtain composites called LDH-CCBC250 and LDH-CCBC500. Physicochemically characterized adsorbents were assessed against the pH (3–9), reaction time (up to 12 h) and initial fluoride concentration (0.5–10 mg L−1) for defluoridation. The porous structure of biochar was found to be richer compared to biocharcoal. The adsorption performance of LDH-CCBC500 was 6-fold higher compared to LDH-CCBC250 signifying the pronounced effect of thermal activation. Fluoride adsorption was pH dependent, and the best pH was in the range of pH 3.5–5.0 and there was no ionic strength dependency. Fluoride uptake by LDH-CCBC500 follows pseudo-second order and Elovich kinetic models, which suggests a chemisorption process followed by physisorption. The most expected way to eliminate fluoride by LDH-CCBC500, which had a maximum adsorption capacity of 7.24 mg g−1, was cooperative chemical adsorption upon the Langmuir and Hills isotherm (r2 = 0.99) parameters. Layered double hydroxide intercalated corncob biochar derived from slow pyrolysis is best performing in acidic waters.

Cu(II) Removal from Aqueous Medium Using Blast Furnace Slag (BFS) as an Effective Adsorbent

The copper adsorption by blast furnace slag (BFS) in an aqueous medium was considered based on the influencing parameters, namely the agitation speed, pH, temperature, the particle size of the solid, and the initial concentration. Physicochemical studies have shown that BFS is consisted mainly from SiO2, CaO, Al2O3, and MgO with a specific surface area of 238 m2/g. Under the optimum parameters, the maximum adsorption amount at equilibrium (140 min) corresponds to 45.16 mg/g. Exploration of adsorption isotherms revealed that the Langmuir model is more consistent with the experimental data. The values of the Freundlich (n) and Langmuir (RL) parameters indicate that the adsorption is favorable. On the other hand, the values of Temkin (bt) and Redlich-Peterson (g) parameters show that adsorption is physical. Pseudo-second order of the adsorption process was confirmed using a kinetic study. Moreover, the diffusional study specified that the transfer of copper from the solution to BFS is successively controlled by external and intraparticle diffusion. The thermodynamic parameters showed that the adsorption of Cu(II) on BFS was feasible, spontaneous, exothermic, and less entropic. The desorption phenomenon has revealed that BFS can be reused for three consecutive cycles.

On the Binding Mechanisms of Calcium Ions to Polycarboxylates: Effects of Molecular Weight, Side Chain, and Backbone Chemistry.

We experimentally determined the characteristics and Langmuir parameters of the binding of calcium ions to different polycarboxylates. By using potentiometric titrations and isothermal titration calorimetry, the effects of side chain chemistry, pH value, and chain length were systematically investigated using the linear polymers poly(aspartic acid), poly(glutamic acid), and poly(acrylic acid). We demonstrate that for polymers with high polymerization degrees, the binding process is governed by higher-order effects, such as the change of apparent pKa of carboxyl groups, and contributions arising from the whole polymer chain while the chemistry of the monomer unit constituting the polymer plays a subordinate role. In addition, primary binding sites need to be present in the polymer, thus rendering the abundance and sequential arrangement of protonated and deprotonated groups important. The detection of higher-order effects contradicts the assumptions posed by the Langmuir model of noninteracting binding sites and puts a question mark on whether ion binding to polycarboxylates can be described using solely a Langmuir binding model. No single uniform mechanism fits all investigated systems, and the whole polymer chain, including terminal groups, needs to be considered for the interpretation of binding data. Therefore, one needs to be careful when explaining ion binding to polymers solely based on studies on monomers or oligomers.

Experimental investigation on different activated carbons as adsorbents for CO2 capture

The current research focuses on characterizing and comparing seven commercially available activated carbons (ACs) as adsorbents for CO2 capture in ambient conditions. Various physiochemical properties like BET surface area, pore-volume, pore diameter, surface morphology, and structural characteristics of the ACs are analyzed using the N2 adsorption/desorption technique, FE-SEM, EDAX and XRD. The equilibrium CO2 uptake capacities of the different activated carbons are estimated for sub-atmospheric to 1 bar pressure and 273 to 333 K. The N2 adsorption/desorption analysis revealed that the selected ACs are highly microporous (Microporosity = 50–81%, SBET = 924–1254 m2/g, pore diameter = 16.54–19.21 Å), with some ultra micropores (pore size <10 Å), which play a vital role in post-combustion CO2 capture. At 1 bar pressure and 273 K, AC CARB 6X12 55 showed maximum CO2 uptake of 4.53 mmol/g, whereas Norit RB 4 showed the least uptake of 3.02 mmol/g. Different parameters of Langmuir, Freundlich, Sips and Tóth isotherm models are estimated based on the experimental P-q-T data. In conjunction with the Vant Hoff’s and the Clausius Clapeyron equations, mentioned isotherm models are used to estimate important thermodynamic properties of adsorption such as change in enthalpy of reaction, entropy and Gibb’s free energy, and isosteric heat of adsorption (Qst). The Qst values for all ACs at different surface coverages varied from 15.20 to 43.33 kJ/mol, confirming the physisorption process. The study confirms that the selected ACs will be suitable for various gas sorption applications. Moreover, the estimated properties will be quite valuable for actual system design.

Calculating PFAS interfacial adsorption as a function of salt concentration using model parameters determined from chemical structure

Per- and polyfluoroalkyl substances (PFAS) are widely-detected environmental contaminants known to concentrate at surfaces and interfaces. Many of the most commonly-detected PFAS function as ionic surfactants under environmental conditions. The interfacial behaviors of ionic surfactants, including PFAS, are strongly dependent on salt concentration and composition, with interfacial affinity potentially varying by orders of magnitude for the same compound under different conditions. The work described here presents a tool for predicting the salt-dependent adsorption of PFAS compounds based entirely on chemical structure, something of great value for predicting the real-world environmental behavior of many of the large numbers of PFAS compounds for which experimental data are not available. The approach combines two different previously-developed models, one a mass-action model designed to predict the effects of salts on interfacial adsorption of ionic PFAS (the UNSW-OU salt model), and the second a group-contribution model designed to predict interfacial adsorption of PFAS in the absence of salt based on chemical structure. The challenge of combining the two models comes from the fact that both are based on different isotherms. The salt model can produce sigmoidal isotherms under salt-limited conditions (an isotherm shape that is supported by experimental evidence), while the group-contribution model can generate Langmuir parameters from calculations based on chemical structure. Equations were derived to determine salt model isotherm parameters from Langmuir parameters (either from the group-contribution model or experimental sources) by matching surface tension curves in the vicinity of the concentration of highest second derivative. Refined group-contribution model parameters were determined based on data from an additional 40 surface tension curves to allow improved structure-based predictions for important classes of PFAS that were not sufficiently well-represented in the original model. The resulting equations provide a tool allowing quantitative predictions of PFAS behavior under realistic environmental conditions for compounds for which little or no experimental data are available.

CAPTURE OF CARBON DIOXIDE FROM SEWAGE SLUDGE PYROLYSIS GASES IN A FIXED BED OF 13X ZEOLITE

Pyrolysis gases can be upgraded through CO2 adsorption. This work shows the pyrolysis of sewage sludge in a 1 kg h−1 rotating cylinder reactor. Non-condensable gases passed through a fixed bed of 13X zeolite at 40 ◦C. Prior to processing actual pyrolysis gases, the equilibrium adsorption capacity of the 13X was evaluated with synthetic CO2 in a magnetic suspension balance to estimate Langmuir, Freundlich and Toth isotherm parameters. Afterwards, a synthetic mixture with composition similar to that of sewage pyrolysis gases was tested in a bench-scale fixed-bed adsorption column to assess both the breakthrough curves for different adsorbent masses (10, 15, and 20 g) and the saturation time of the adsorbent. The dynamic adsorption in the column was modeled as a system of partial differential equations (PDEs), which was transformed into a system of Ordinary Differential Equations (ODEs) via the Method of Lines and, then, solved using DASSL. The ODEs were used to estimate adsorption parameters such as coefficient of axial dispersion, effective diffusivity within the particle, and external coefficient of mass transfer. The synthetic gases were replaced with actual sewage sludge pyrolysis gases in the adsorption column with 13X. The breakthrough curves revealed a quick saturation of the bed by pyrolysis aerosols. Despite its short lifetime in comparison with synthetic gases, the 13X proved effective in adsorbing pyrolysis CO2.

Sulfur Fractions, Distribution and Sorption Characteristics in Some Soils of Ogun State, Southwestern Nigeria

ABSTRACT Sulfur (S) fractions, distributions and sorption characteristics of some soils in Ogunstate, Southwestern Nigeria, were evaluated in ten different locations, the area lies with in the Derived Savannah and forest agro-ecological zone. Result showed available, adsorbed, organic and total S ranged from 3.9 to 19.8, 16.3 to 36.6, 214.9 to 412.9 and 248.8 to 446.6 mg kg−1 respectively. Organic S constituted 86.4 to 93.4% of total S. The mean status of available S was slightly above the critical limit of 10 mg kg−1. All fractions of S maintained significant positive correlation (p ≤ .05) with each other and total organic carbon, while available and adsorbed S had significant and negative correlation with soil pH, total nitrogen, available phosphorus and calcium. The S sorption behavior of the soils varied and increased with increase in S concentrations of equilibrium solution. The isotherm model for the ten locations was S-curved type. Sorption data were fitted to Langmuir and Freundlich sorption isotherms. Langmuir equation was best fitted to the S adsorption data in the ten locations except soils from Owode, Odeda and Ikenne. Langmuir and Freundlich parameters (sorption maxima, binding energy and maximum buffering capacity affinity constant and slope) were significantly correlated with some soil properties.

Adsorption of a cationic dye (Methylene bleu) by Typha Latifolia: Equilibrium, kinetic, thermodynamic and DFT calculations

In this work, the adsorption performance of methylene blue (MB) on rough R and Typha Latifolia RS was studied. On one hand, the effect of various parameters on the adsorption efficiency were studied knowing that the mass of the material, the adsorption time, the initial concentration and the pH of solution. All these different parameters influence the absorption capacity. The maximum amount of adsorption of the different materials studied are estimated at 21.01 mg g−1 and 54.73 mg g−1 at pH = 5. Under all optimal conditions, the relevant MB removal rates at R and RS were 69.62% and 91.09%, respectively. On the other hand, the mathematical modeling studied has shown that the S-type adsorption process and that the pseudo second order and Langmuir are the most suitable models to describe the adsorption of the cationic dye via R and RS. In fact, the study of Langmuir and Freundlich parameters has indicated that the removal of MB by R and RS is favorable. Moreover, Theoretical calculations were carried out using simulations of the (DFT) explored the interaction between the most reactive sites concerning the major biosorbent constituent Typha Latifolia which is the cellulosic polymer and the cationic dye MB. The comparative study of all experimental and theoretical results has confirmed the biosorption potential of the studied biosorbent for the removal of dyes.

Elucidating the mass transfer mechanism of CrVI adsorption by encapsulated chitosan-carbon nanotubes-iron beads in packed-bed columns

This study evaluates the CrVI breakthrough behaviors of a continuous-flow column packed with composite chitosan-MWCNTs‑iron beads under various operating conditions. Under the tested range of experimental parameters, a maximum of 54% of CrVI removal was achieved at: water flow rate, 1 mL/min, feed CrVI concentration, 30 mg/L; and packed bed height 8 cm. A homogeneous surface diffusion model (HSDM) involving convection-dispersion and diffusion equations was formulated, numerically solved, and experimentally validated. The high degree of conformity between the calculated and experimental breakthrough curves facilitated the determination of mass transfer parameters including axial dispersion DL, (1.30 × 10−8 to 1.56 × 10−7 m2/s) and surface diffusion Ds, (7.28 × 10−11 to 1.80 × 10−10 m2/s) via an error minimizing approach. The DL value was a function of molecular diffusion, which varied with the flow velocity, mass loading, and bed height. The Ds values were slightly higher than those previously reported, owing to the heterogeneous nature of the adsorbent. The external film diffusion coefficient (kf) was also determined by using Wilson-Geankoplis empirical correlation, which was recognized as a rate-controlling factor during CrVI mass transfer to the adsorbent beads. Furthermore, sensitivity analysis showed that a transition from diffuse- to shock-front occurred with a decreasing DL, while a decrease in the slope of breakthrough curves was observed by decreasing Ds and bed porosity, and increasing kf and Langmuir parameters. Lastly, the study demonstrated a high correlation between utilization of fractional bed capacity and axial Peclet number. This method is suitable for optimizing operating conditions to maximize the utilization of a fixed-bed columns.

ADSORPTION ISOTHERM MODELS AND KINETICS FOR PHOSPHATE ADSORPTION IN SEDIMENT

Phosphate ions in solution can be adsorbed using sediment. Phosphate adsorption by sediment was influenced by concentration, adsorbent dosage, and temperature. The research was carried out at pH 1 for 30 minutes. The optimum adsorption occurs at a concentration of 15 ppm with an adsorption capacity of 0.41 mg/g. The adsorbent dosage was used as 1 mg with a capacity of adsorption capacity of (0.6077 mg/g). The optimum temperature is obtained at 40oC with a capacity of adsorption (0.1250 mg/g). Adsorption isotherm follows the Langmuir and Freundlich model. The Langmuir parameters as R2 (0.7270) KL(6.1750 L/mg), qm (0.3329 mg/g). Freundlich parameters were obtained as follows: R2 (0.9741), 1/n (0.6059), and KF (0.5635 m/g (L/mg)1/n. Reaction kinetics based on pseudo-second-order kinetic with a value of R2 = 0.9717, K = 25.2554 gmol-1hour-1

Isothermal Modelling of the Adsorption of Chromium onto Calcium Alginate Nanoparticles

Because of its extensive usage in industrial applications such as leather tanning, metallurgy, electroplating, and refractory materials, chromium is one of the most dangerous trace elements introduced into surface and ground waters. The sorption isotherm of chromium sorption onto calcium alginate nanoparticles were analyzed using ten models—Henry, Langmuir, Dubinin-Radushkevich, Freundlich, BET, Toth, Sips, Fritz-Schlunder IV, Baudu and Fritz-Schlunder V, and fitted using non-linear regression. Only the Toth and Fritz-Schlunder V models were unable to fit the data. Statistical analysis based on root-mean-square error (RMSE), adjusted coefficient of determination (adjR2), bias factor (BF), accuracy factor (AF), corrected AICc (Akaike Information Criterion), BIC and HQC showed that the Langmuir model was the best model in terms of overall best criteria. The calculated evidence ratio was 7 with an AICc probability value of 0.87 indicating that the best model was at least 7 times better than the nearest best model, which was Freundlich. The calculated Langmuir parameters qmL value of 79.174 mg/g (95% confidence interval from 50.702 to 107.646) and bL value of 0.332 L/mg (95% confidence interval from 0.294 to 0.371) is not much different from the linearized published work for the qmL value of 145 mg/g but lower than the bL value of 0.34 L/mg. The nonlinear regression method allows for the parameter values to be represented in the 95% confidence interval range which can better allow comparison with published results.