Non-linear Isotherm Models Research Articles

Pb (II) Recovery by Modified Tuffite: Adsorption, Desorption, and Kinetic Study

In this study, Pb (II) removal from wastewater was investigated using a modified vitric crystal tuffite with a BET surface area of 11.7 m2/g. For this purpose, tuffite was used in its natural and modified form with ethylenediaminetetraacetic acid (EDTA). Batch adsorption experiment was performed. The effects of contact time (0–90 min), adsorbent dosage (1–10 g/L), initial concentration (10–200 mg/L), and pH (2–12) on the removal of Pb (II) were investigated. The isotherm data were fitted to Langmuir, Freundlich, Temkin, and Redlich-Peterson isotherm models. Kinetic models such as pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used. In order to optimize the adsorption system and investigate the kinetic behaviour of adsorption, nonlinear isotherm and kinetic models were used as well as linearized models. Error analyses were made in order to express the obtained results more accurately. pH 5 was the optimum value for adsorption. According to nonlinear isotherm model calculations, Bayburt stone (BS) and its modified form (MBS) had [Formula: see text] values of 335 and 584 mg/g, respectively. The Freundlich model, with its high correlation coefficients of about 1.00, was found to be more suitable for the adsorption of Pb (II) to MBS. The pseudo-second-order kinetic model with mean [Formula: see text] and [Formula: see text] values of 0.997 and 0.0116 1/min, respectively, was found to be more appropriate. According to the regeneration studies, the maximum desorption efficiency was 97.8%. The thermodynamic equilibrium coefficients obtained at different temperatures and [Formula: see text], [Formula: see text], and [Formula: see text] values were observed as -21.4, 46.4, and 163 kJ/mol, respectively. These values indicate that the adsorption of Pb (II) on to MBS was endothermic and spontaneous process. BS and MBS were characterized by different instrumental analyses such as SEM, EDS, FTIR, and zeta potential measurements.

Kinetic and equilibrium adsorption study of anionic dyes using oil palm trunk-derived activated carbon

Oil palm trunk (OPT) was chemically activated to produce high surface area activated carbon (AC) in this work. The adsorption performances of OPT-derived AC in removing two different anionic dyes, i.e. acid blue 25 (AB 25) and sunset yellow (SY) from the aqueous solution, were evaluated individually and as a binary system. The effects of adsorbate concentration, pH, temperature, and duration were examined via batch adsorption studies. Both AB 25 and SY adsorption were most favourable at pH of 2, with the absence of electrostatic repulsion between AC and the dye components. The adsorption isotherm of AB 25 and SY can be well fitted using the non-linear Langmuir isotherm model, while the adsorption kinetics can be correlated well using the non-linear pseudo-second order model. The adsorption process of both anionic dyes was spontaneous and endothermic. The OPT-derived AC endured at least seven regeneration cycles during reusability tests with at least 80 % contaminant removal retained throughout.

Modeling and Simulation of Upstream and Downstream Processes for Monoclonal Antibody Production

We present a numerical case study for modeling and simulation of upstream and downstream processes for monoclonal antibody (mAb) production. We apply a systematic and intuitive modeling methodology for an existing upstream process and downstream process. The resulting models are based on differential mass balances and kinetic expressions for the reactions and adsorption. Mass balances for the fedbatch reactor yield a model consisting of five ordinary differential equations (ODEs). The downstream process is conducted batchwise in a chromatographic column for capture of mAbs. Mass balances of the chromatographic column yield a system of partial differential equations (PDEs). The chromatographic model applies the nonlinear shrinking core adsorption isotherm model for transition between the mobile phase and the stationary phase. We apply a high-order spectral nodal continuous Galerkin scheme for spatial discretization of the chromatographic column, which result in a semi-discrete ODE formulation. The resulting simulation model, coupling the upstream and downstream processes in batchwise mAb production, can be used as a benchmark for numerical estimation, control and optimization studies.

Sulfhydryl Functionalized Magnetic Chitosan as an Efficient Adsorbent for High-Performance Removal of Cd(II) from Water: Adsorption Isotherms, Kinetic, and Reusability Studies

In this study, dimercaptosuccinic acid-functionalized magnetic chitosan (Fe3O4@CS@DMSA) was synthesized via in situ coprecipitation process and amidation reaction, aiming to eliminate cadmium (Cd(II)) ions from an aqueous environment. The structure, morphology, and particle size of the Fe3O4@CS@DMSA adsorbent were investigated using FTIR, TEM, EDX, TGA, zeta potential, and XRD techniques, and the obtained results approved the successful synthesis of the Fe3O4@CS@DMSA nanocomposite. The influence of external adsorption conditions such as pH solution, adsorbent mass, initial Cd(II) concentration, temperature, and contact time on the adsorption process was successfully achieved. Accordingly, pH: 7.6, contact time: 210 min, and adsorbent mass:10 mg were found to be the optimal conditions for best removal. The adsorption was analyzed using nonlinear isotherm and kinetic models. The outcomes revealed that the adsorption process obeyed the Langmuir and the pseudo-first-order models. The maximum adsorption capacity of Fe3O4@CS@DMSA toward Cd(II) ion was 314.12 mg/g. The adsorption mechanism of Cd(II) on Fe3O4@CS@DMSA nanocomposite is the electrostatic interaction. The reusability test of Fe3O4@CS@DMSA nanocomposite exhibited that the adsorption efficiency was 72% after the 5th cycle. Finally, this research indicates that the Fe3O4@CS@DMSA exhibited excellent characteristics such as high adsorption capacity, effective adsorption-desorption results, and easy magnetic separation and thus could be an effective adsorbent for removing Cd(II) ions from aqueous solutions.

Fabrication of magnetically recyclable nanocomposite as an effective adsorbent for the removal of malachite green from water

Herein, a novel magnetic nanocomposite (Fe3O4@ATPA@AMPA) was successfully synthesized for the removal of malachite green (MG) from water. The FT-IR analysis confirmed successful modification of Fe3O4@ATPA with 2-Amino-3-mercaptopropionic acid (APMA). Based on TEM image and XRD pattern, the average particle size of Fe3O4@ATPA@AMPA nanocomposite was ∼ 12.3 nm. The specific surface area of Fe3O4@ATPA@AMPA nanocomposite was 35 m2/g. Elemental analysis exhibited the existence of S, O, C, and N on the surface of Fe3O4 nanoparticles. The influence of time (t: 5–240 min), dose (m: 0.010–0.050 g), pH (2–8.5), initial MG concentration (Co: 25–300 mg/L), and temperature (T: 298–318 K) on the MG adsorption was examined. Experimental results exhibit optimal MG uptake at pH: 6.7, t: 120 min, m: 20 mg, T: 298 K, and Co: 300 mg/L. The non-linear kinetics and isotherm models showed that the adsorption process obeyed pseudo-first-order kinetic and Langmuir isotherm models, respectively. According to Dubinin–Radushkevich (D–R) isotherm, the magnitude of activation energy (Ea) at varied temperatures was in range 0.0116−0.0905 kJ/mol, confirming physical interactions between MG molecules and Fe3O4@ATPA@AMPA nanocomposite dominates during adsorption. The maximum monolayer adsorption capacity for MG was 414.63 mg/g at 298 K. The adsorption process was exothermic, favorable, and spontaneous. Finally, the Fe3O4@ATPA@AMPA nanocomposite exhibited excellent adsorption potential for four consecutive regeneration cycles.

An innovative amino-magnetite@graphene oxide@amino-manganese dioxide as a nitrogen-rich nanocomposite for removal of Congo red dye

Design and assembly of a novel nanocomposite with efficient incorporated functional groups as well as superior adsorption behavior is a challenging aspect and generally aimed in the research and application fields which are focused on removal of organic, inorganic and biological pollutants. Appreciable amounts of colored wastewater are produced due to the existence of some dyes in water even at very low concentration levels which are known as highly toxic and undesirable pollutants. Therefore, the current study is devoted to assemble a novel nanocomposite for removal Congo red (CR) dye based on the intercalation of graphene oxide (GO) with amino-nanomagnetite (Fe3O4-NH2) and amino-nanomanganese dioxide (MnO2-NH2) for the fabrication of NH2-Fe3O4-GO-MnO2-NH2 by microwave assisted synthesis technique. The as-prepared NH2-Fe3O4-GO-MnO2-NH2 nanocomposite was explored for removal of Congo red (CR, anionic dye) from aqueous matrices. The produced NH2-Fe3O4-GO-MnO2-NH2 along with its constituent counterparts was investigated by FT-IR, SEM, BET, XRD and TGA for characterization and structure confirmation. Experimental studies were performed to figure out the impact of pH and CR dye was found to reach the maximum removal efficiency at pH 2. The variation in NH2-Fe3O4-GO-MnO2-NH2 dosage, shaking time, temperature and initial dye concentration were also optimized to achieve the maximum removal percentages of CR. The best fitting of kinetic model was referred to pseudo-second order. The linear and nonlinear isotherm models to evaluate the CR removal performance by NH2-Fe3O4-GO-MnO2-NH2 were examined and found to best fitted to Langmuir model. Thermodynamic parameters, viz., ΔHo, ΔGo, and ΔSo were also estimated to confirm spontaneous and endothermic adsorption behaviors. Excellent CR dye extraction percentages (96–100%) were achieved from various water samples by applying the optimum conditions. Consequently, NH2-Fe3O4-GO-MnO2-NH2 nanocomposite is believed to exhibit high potential in water remediation for dye removal.

Synthesis of carbon modified with polymer of diethylenetriamine and trimesoyl chloride for the dual removal of Hg (II) and methyl mercury ([CH3Hg]+) from wastewater: Theoretical and experimental analyses

A novel adsorbent was synthesized by modification of waste rubber tiers derived activated carbon (AC) with diethylenetriamine (DETA)-trimesoyl chloride (TMC) copolymer. The synthesized AC/DETA-TMC nanocomposite was characterized by FT-IR and SEM/EDX techniques. Dependency of the adsorption yield on the batch parameters was studied via factorial design method. From the non-linear Langmuir isotherm model, the adsorption capacity of the AC/DETA-TMC nanocomposite was determined as 317.3 and 263.6 mg g−1 for inorganic mercury (Hg2+) and organic mercury (methyl mercury; [CH3Hg]+, respectively. The adsorption kinetic mechanism of both mercury species was recognized well by the PSO model. The thermodynamic calculations verified that the adsorption processes progressed spontaneously and exothermically. The cycling adsorption/desorption treatments exposed that the produced nanocomposite showed still reusable performance in moderate level until seven cycles. The nanocomposite demonstrated high removal performance in case of wastewater samples. To investigate the power of the interactions between studied chemical species, DFT calculations were performed and adsorption energies were calculated. It is important to note that theoretical results support the experiments made.

Natural Clay as a Low-Cost Adsorbent for Crystal Violet Dye Removal and Antimicrobial Activity.

This investigation aimed at evaluating the efficiency of micro and nanoclays as a low-cost material for the removal of crystal violet (CV) dye from an aqueous solution. The impacts of various factors (contact time, pH, adsorbent dosage, temperature, initial dye concentration) on the adsorption process have been taken into consideration. Six micro and nanoclay samples were obtained by treating clay materials collected from different locations in the Albaha region, Saudi Arabia. Out of the six tested micro and nanoclays materials, two (NCQ1 and NCQ3) were selected based on the highest adsorption efficiency for complete experimentation. The morphology and structure of the selected micro and nanoclay adsorbents were characterized by various techniques: SEM-EDX, FTIR, XRF, XRD, and ICP-MS. The XRF showed that the main oxides of both nanoclays were SiO2, Al2O3, Fe2O3, K2O, CaO, and MgO, and the rest were impurities. All the parameters affecting the adsorption of CV dye were optimized in a batch system, and the optimized working conditions were an equilibrium time of 120 min, a dose of 30 mg, a temperature of 25 °C, and an initial CV concentration of 400 mg/L. The equilibrium data were tested using nonlinear isotherm and kinetic models, which showed that the Freundlich isotherm and pseudo-second-order kinetics gave the best fit with the experimental data, indicating a physico-chemical interaction occurred between the CV dye and both selected micro and nanoclay surfaces. The maximum adsorption capacities of NCQ1 and NCQ3 adsorbents were 206.73 and 203.66 mg/g, respectively, at 25 °C. The thermodynamic factors revealed that the CV dye adsorption of both micro and nanoclays was spontaneous and showed an exothermic process. Therefore, the examined natural micro and nanoclays adsorbents are promising effective adsorbents for the elimination of CV dye from an aqueous environment.

Using raw and thermally modified fibrous clay minerals as low concentration NH4+-N adsorbents.

Raw and modified fibrous clay minerals palygorskite (Pal) and sepiolite (Sep) were tested for their ability to remove ammonium from ammonium polluted water. Palygorskite and sepiolite underwent thermal treatment at 400°C (T-Pal and T-Sep respectively). Raw and thermally treated samples were characterized using XRD, SEM, BET, FTIR, TGA, zeta potential, and XRF. The techniques verified the effect of thermal treatment on sample structures and the enhancement of negative charge. Both raw and thermally activated materials were applied in batch kinetic experiments, and found to be efficient adsorbents in their raw forms, since Pal and Sep achieved 60 and 80% NH4+-N removal respectively within 20 min of contact for initial NH4+-N concentration of 4 mg/L. Similar removal rates were gained for other concentrations representative of contaminated aquifers that were examined, ranging from 1 to 8 mg/L. Results for the modified T-Pal and T-Sep minerals showed up to 20% higher removal rate. Saturation tests indicated the positive effect of thermal treatment on the minerals since T-Pal and T-Sep removal efficiency reached 85% and remained stable for 24 h. However, competitive ions in real water samples can influence the NH4+-N removal efficiency of the examined samples. At almost all the examined samples, the nonlinear Freundlich isotherm and linear pseudo-second kinetic models showed better fitted all examined samples thus indicating heterogeneous chemisorption.

Application of Non-Linear Kinetic and Isotherm Model for Investigation of Cod Removal from Tapioca Liquid Waste Onto Modified Lampung Natural Zeolite

The experimental data analysis of tapioca liquid waste onto modified Lampung natural zeolite using non-linear regression models is limited. The adsorption data were analyzed with nine kinetic models (the pseudo-first-order, the pseudo-second-order, the intraparticle diusion, fractional power, Bangham, Elovich, mixed-1.2-order, modification of pseudo-second-order, and Avrami) and eight isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich, Sips, Redlich-Peterson, Toth, Liu, and Khan). The percentage of adsorption was decreased from 61.29% to 13.66% with increasing Chemical Oxygen Demand (COD) concentration 310 mg/L to 9450 mg/L. The result showed that the power model (R2 : 0.98, X2 : 0.137), Avrami (R2 : 0.98, X2 : 0.141), Bangham (R2 : 0.98, X2 : 0.145) and modified pseudo-second-order (R2 : 0.98, X2 : 0.147) can be recommended as the best fied to experimental kinetic data. The Khan model (R2 : 0.99961, X2 : 0.03729) and Langmuir (R2 : 0.99478, X2 : 0.24902) was the most reliable for describing the isotherm model. Thus, the analysis of experimental adsorption data using a non-linear regression model is highly recommended.

Adsorption of Zn2+ from Synthetic Wastewater Using Dried Watermelon Rind (D-WMR): An Overview of Nonlinear and Linear Regression and Error Analysis

Sustainable wastewater treatment is one of the biggest issues of the 21st century. Metals such as Zn2+ have been released into the environment due to rapid industrial development. In this study, dried watermelon rind (D-WMR) is used as a low-cost adsorption material to assess natural adsorbents’ ability to remove Zn2+ from synthetic wastewater. D-WMR was characterized using scanning electron microscope (SEM) and X-ray fluorescence (XRF). According to the results of the analysis, the D-WMR has two colours, white and black, and a significant concentration of mesoporous silica (83.70%). Moreover, after three hours of contact time in a synthetic solution with 400 mg/L Zn2+ concentration at pH 8 and 30 to 40 °C, the highest adsorption capacity of Zn2+ onto 1.5 g D-WMR adsorbent dose with 150 μm particle size was 25 mg/g. The experimental equilibrium data of Zn2+ onto D-WMR was utilized to compare nonlinear and linear isotherm and kinetics models for parameter determination. The best models for fitting equilibrium data were nonlinear Langmuir and pseudo-second models with lower error functions. Consequently, the potential use of D-WMR as a natural adsorbent for Zn2+ removal was highlighted, and error analysis indicated that nonlinear models best explain the adsorption data.

Synthesize and application of magnetic molecularly imprinted polymers (mag-MIPs) to extract 1-Aminopyrene from the human urine sample

New magnetic molecularly imprinted polymers (mag-MIP) were developed for 1-Aminopyrene (1-Ap) detection in human urine samples. 1-Ap is a biomarker for exposure to the 1-Nitropyrenes (as a mutagenic compound) present in the particles emitted from various sources mainly the diesel engines. Fe3O4 (as a magnetic core), TEOS, 1-Ap (as a template), MAA (as a functional monomer), EGDMA (as a cross-linker), and AIBN (as an initiator) were utilized for mag-MIP fabrication in the three-stage processes. Polymer characterization was performed using FTIR, SEM, TEM, and VSM analysis. HPLC-Fl equipment was used for 1-Ap detection. The recoveries and limit of detection were obtained 0.25 µg/ L and 87.2–95.7%, respectively. The results of the nonlinear isotherm and kinetics models had shown maximum adsorption capacity of 51 µg/mg for mag-MIP at relatively short equilibrium time of 30 min for 1-Ap, which was 2.9 times more than magnetic molecularly non-imprinted polymers (mag-NIP). A rapid magnetic separation (13.70 emu/g, 30 s) was observed for mag-MIP applications. Therefore, the present mag-MIP can be successfully used for 1-Ap extraction and detection.

Evaluation of the Microsoft Excel Solver Spreadsheet-Based Program for Nonlinear Expressions of Adsorption Isotherm Models onto Magnetic Nanosorbent

The sorption of basic dyes onto magnetic nanosorbent is commonly used as a novel material to combat powdered activated carbon, which is difficult to handle and separate during water and wastewater treatment. This adsorption method is commonly implemented in water and wastewater treatment due to its low cost and high performance. To explore the feasibility of adsorption, six different nonlinear isotherm models were applied and introduced to evaluate the performance and adsorption mechanisms via Microsoft Excel, and they were then compared to those of MATLAB and OriginPro. The Langmuir best provided the sorption of methylene blue adsorbed for a two-parameter isotherm model. The three-parameter model Toth gave a goodness of fit indicating a heterogeneous sorbent surface. Error function analysis found that the Residual Sum of Squares Error, Chi-square, Coefficient of determination, Average Relative Error, Hybrid Fractional Error Function, Marquardt’s Percent Standard Deviation and Root Mean Square Error provided the best overall results. In comparison, it could be concluded that six isotherm models showed the confidence interval that is simply the best fit at all experimental data points provided by the three software tools. All error function results indicated that the Microsoft Excel Solver function spreadsheet method satisfied all the statistic measures to predict the real variance of the probability of experimental data for all six isotherm models of adsorption of basic dye removal. One added benefit of this Microsoft Excel software tool is the built-in function associated with the desired type of application, which designates the desired type of error/statistical functions not mentioned in this research to the adsorbent materials used.

As(III) adsorption on co-precipitated cobalt substituted ferrite nanoparticles

We synthesized CoxFe3-xO4 (x = 0, 0.5 and 1.0) nanoparticles (NPs) for aqueous As(III) adsorption trough pH 5–9. The ferrite NPs were characterized by XRD and SEM, determining that ~ 20 nm mean size was predominant in Fe3O4, Co0.5Fe2.5O4, and CoFe2O4. XPS was used to find what the Co0.5Fe2.5O4 NPs are enriched for Fe3+ ions in the octahedral sites in comparison to CoFe2O4 and Fe3O4 NPs. Magnetometry revealed that the Co0.5Fe2.5O4 NPs were magnetically harder. Adsorption of arsenite on ferrite NPs freshly synthesized was formerly examined for linear intraparticle diffusion model (IPD). Then the nonlinear Pseudo First Order (PFO), Pseudo Second Order (PSO), and Elovich models were applied for As(III) adsorption kinetics. Once the system reached equilibrium, adsorption results were fitted through the nonlinear isotherm models of Freundlich and Langmuir. IPD model revealed that mass transfer from the bulk As(III) solutions (0.5–12 mg/L) toward ferrite NPs occurred immeasurably rapid so that IPD determined the main course of the adsorption process. Unlike PFO and PSO, the Elovich model did not fit adsorption data; PSO was the model that described better adsorption kinetics. Freundlich and Langmuir isotherm models fitted in good agreement equilibrium adsorption data. Arsenic adsorption and removal were affected by the type of NPs, whereas no effect was recorded for pH from 5 to 9, with arsenic removal rates as high as 95%–92% through increasing As(III) nominal concentrations. Co0.5Fe2.5O4 NPs exerted the highest arsenic removal and adsorption capacity, which was strongly related to NPs properties.

Preparation and characterization of modified anion exchange resin for uranium adsorption: estimation of nonlinear optimum isotherm, kinetic model parameters, error function analysis and thermodynamic studies

In this study, a modified metal hydroxides on surface of Lewatit resin (HMO @LM500, where M indicates to Al, Fe, Mn or Zn) were designed and used as efficient adsorbents for uranium (U(VI)) ions capture from aqueous solution. The prepared materials were characterized by using transform infrared spectroscopy, scanning electron microscope, energetic dispersive x-ray techniques. Batch adsorption methods were done to investigate all factors affecting adsorption process such as the effect of pH, concentration, contact time and temperature. Optimum values of each parameter were calculated as pH of 1.8, temperature of 298 K (25 °C), contact time of 60 min for the removal of uranium ions. Analysis within the nonlinear isotherm models indicates that the Liu model offers the best description for the equilibrium data since it has the highest R 2 value and the lowest error analysis value when compared with the other models. The calculated adsorption capacity of Liu model is 217.06 mg g−1, whereas analysis within the nonlinear kinetic models indicate that pseudo-second-order behavior is involved. The thermodynamic examination of the equilibrium data proved that the adsorption process of U(VI) was found to be a spontaneous and exothermic process. The ΔH 0 and ΔS 0 parameters were calculated as −66.5827 kJ mol−1 and −0.2051 kJ mol−1 K−1, respectively. Therefore, the prepared adsorbent can be applied to capture of U(VI) ions from aqueous medium.

Effective adsorption of methylene blue dye from water solution using renewable natural hydrogel bionanocomposite based on tragacanth gum: Linear-nonlinear calculations

Today, hydrogels opened new windows to the high-tech due to their amazing features. Thus, we applied hydrogel nanocomposite (HNC) made of tragacanth gum (a kind of polysaccharide) and CaCO3 nanoparticles to remove methylene blue dye (MBD) from the water solution. We used nonlinear and linear isotherms and kinetics as well as thermodynamics to uncover the adsorption mechanism. The results showed that the hydrogel could remove 80% of MBD. Besides, the linear form of the pseudo-second-order kinetic model fits well with the results, showing chemical interactions. We found that this process follows both Sips and Redlich-Peterson models by applying nonlinear and linear isotherm models. The maximum adsorption capacities from nonlinear and linear Sips were 1401 and 2145 mg/g, respectively. Based on the thermodynamic equations, the adsorption of MBD onto HNC was physiochemical and exothermic. According to the phenomenological calculations, diffusion from the bulk (or film diffusion, Df = 1.2 × 10−8 cm2/s) is the primary mechanism.

Application of the Fe3O4/ alginate/ diatomite nano-adsorbent for the adsorption of palladium and cyanide from wastewater: optimisation, kinetic and equilibrium studies

ABSTRACT In this research, the adsorption rates of cyanide and palladium onto Fe3O4/alginate/diatomite nano-adsorbent (FADA) were evaluated. The co-precipitation technique was applied to synthesis of FADA. The response surface methodology (RSM) was employed to investigate the relation between input-independent factors (initial pollutant concentration, contact time, FADA dosage and pH) and one dependent output response (removal efficiency). The best model was selected based on the results of the ANOVA analysis.SO model due to R2 of 0.929 and the insignificant lack of fit (0.12) for cyanide and also R2 of 0.98 and the insignificant lack of fit (0.12) for palladium was selected as an appropriate model for adsorption of both pollutants. Therefore, prediction and optimisation of the adsorption of the pollutants onto FADAwere done based on SO model. The best conditions for the adsorption of cyanide (95.65%) and palladium (92.66%) onto FADA were obtainedat (pH, 5.45; palladium concentration, 15.13 mg L−1; contact time, 104.8 min and FADA dosage, 0.98 g L−1) and (pH,7.0; cyanide concentration, 4.88 mg L−1; contact time, 91.06 min and FADA dosage, 2.05 g L−1), respectively. Investigation of the non-linear isotherm models indicated adsorptions of cyanide (R2 = 0.995) and palladium (R2 = 0.999) ontoFADA have reasonably fit to the Sips model.The maximum adsorption capacities of cyanide and palladium per mass unit of FADA were 208.55 mg g−1 and 60.2 mg g−1, respectively.The pseudo-first-order (R2 = 0.99) and the intra-particle diffusion (R2 = 0.96) were found to agreement well with the adsorption experimental data obtained for cyanide and palladium, respectively. Results indicated the sorption reactions of cyanide and palladium onto FADA were endothermic and exothermic, respectively.The present study indicated diatomite magnano composite boosted with alginate polymer beads due to high operating groups and also a high surface-to-volume ratio and porosity can be applied as an efficient adsorbent for the removal of cyanide and palladium from aqueous solutions.

Kinetics, equilibrium and thermodynamic investigations of methylene blue dye removal using Casuarina equisetifolia pines

Casuarina equisetifolia pines are degradable biopolymeric substance with dye-sequestering property was utilized as biosorbent to expel a cationic dye; methylene blue dye from simulated wastewater. The prepared adsorbent material was characterized for their structural, morphological and elemental features to understand their suitability in augmenting in dye-wastewater remediation. The results infer that 0.5 g/L biosorbent was proficient in removing 100 mg/L methylene blue (pH 7.0 ± 0.2) when agitated at 150 rpm for 120 min. Isothermal behavior were evaluated using non-linear isotherm models like Temkin, Langmuir and Freundlich models while the rate-limiting steps were found using kinetic models. Temkin isotherm and pseudo-first order model explained the removal mechanism among the models evaluated, which infers that the biosorption followed physisorption with the maximum adsorption capacity of 41.35 mg/g. Thermodynamic behavior of methylene blue removal by C. equisetifolia pines powder described the feasibility of biosorption as well as the type of heat involved. Equilibrium sorption capacities, rate constants and correlation coefficients explains that MB dye removal by C. equisetifolia pines is presumably physisorption, spontaneous and endothermic in nature.

Adsorption of 4-Nitrophenol on calcium alginate-multiwall carbon nanotube beads: Modeling, kinetics, equilibriums and reusability studies

In this study calcium alginate-multiwall carbon nanotube (CA/MWCNTs) was synthesized using (CA) calcium alginate and multiwall carbon nanotube (MWCNTs), and its efficiency in adsorption of 4-Nitrophenol (4-NP) in aqueous solution was studied. The structure and properties of the synthesized adsorbent were investigated using scanning electron microscope (SEM), thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). The experimental design was performed using Box–Behnken design (BBD) in which variables pH, CA/MWCNTs, and temperature were examined. The results of the effect of temperature on the removal efficiency of 4-NP showed that the adsorption efficiency decreases with increasing temperature. The results of nonlinear isotherm and kinetics models showed that Langmuir and pseudo-second-order models were more consistent than other models. The maximum adsorption capacity of 4-NP in this study by CA, MWCNTs, and CA/MWCNTs was 136, 168.4, and 58.8 mg/g, respectively, which indicates that the use of MWCNTs on CA could increase the adsorption capacity. The results of reuse of the synthesized adsorbent at 4-NP removal also showed that after 5 reuse of the adsorbent, the removal of 4-NP using CA/MWCNTs is reduced by about 10%, which shows that the synthesized adsorbent can be used several times to adsorb contaminants without significant reduction in the efficiency.

Nonlinear Isotherm and Kinetic Modeling of Cu(II) and Pb(II) Uptake from Water by MnFe2O4/Chitosan Nanoadsorbents

Researchers are in continuous search of better strategies to minimize, if not prevent, the anthropogenic release of toxic heavy metals, such as Cu(II) and Pb(II), into drinking water resources and the natural environment. Herein, we report for the first time the low-temperature combustion synthesis of magnetic chitosan-manganese ferrite in the absence of toxic cross-linking agents and its removal of Cu(II) and Pb(II) from single-component metal solutions. The nonlinear Langmuir model best described the isotherm data, while the nonlinear pseudo-second order model best described the kinetic data, signifying monolayer Cu(II) or Pb(II) adsorption and chemisorption as the rate-determining step, respectively. Adsorption capacities by magnetic chitosan-manganese ferrite obtained for both metals were consistently higher than those by manganese ferrite, indicating that chitosan enhanced the performance of the magnetic adsorbent. The maximum adsorption capacities of magnetic chitosan-manganese ferrite for Cu(II) and Pb(II) were 14.86 and 15.36 mg g−1, while that of manganese ferrite were 2.59 and 13.52 mg g−1, respectively. Moreover, the adsorbents showed superior binding affinity and sorption for Pb(II) than Cu(II) owing to the stronger ability of the former to form inner-sphere complexes with manganese ferrite and magnetic chitosan-manganese ferrite. Finally, thermodynamic studies revealed that the uptake of either Pb(II) or Cu(II) by magnetic chitosan-manganese ferrite was spontaneous and endothermic. The as-prepared adsorbent was characterized for morphology, elemental composition, surface functional sites, and particle size using scanning electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, and dynamic light scattering technique, respectively.