Radke Prausnitz Research Articles

Quasi-isothermal (Q-TG), cryoporometric (DSC) and adsorption characterization of activated carbons

In the presented paper, the structural and energetic heterogeneities of the activated carbons (ACs) surfaces were investigated. The ACs of well-developed microporosity were obtained from the spent coffee grounds as a result of pyrolysis (N2 or CO2) with the chemical activation of H3PO4 (I = 1, 1.5 or 2 w/w). The low-temperature N2 adsorption, the quasi-isothermal thermogravimetry as well as the low-temperature differential scanning calorimetry were employed. Moreover, the selected materials adsorption properties were studied in relation to methylene blue (MB). The micro/mesoporous structure of the carbons was proved. The different types of water clusters on the surface indicated the carbons surface heterogeneity. The activated carbons are characterized by the high sorption capacity (qe,exp = 200.3–237.67 mg g−1) as for MB. The adsorption process was described by means of the Radke–Prausnitz isotherm model.Graphical abstract

Optimization of Binary Adsorption of Metronidazole and Sulfamethoxazole in Aqueous Solution Supported with DFT Calculations

Sulfamethoxazole [SMX] and metronidazole [MNZ] are emergent pollutants commonly found in surface water and wastewater, which can cause public health and environmental issues even at trace levels. An efficient alternative for their removal is the application of adsorption technology. The present work evaluated single and binary adsorption processes using granular activated carbon (CAG F400) for SMX and MNZ in an aqueous solution. The binary adsorption process was studied using a Box–Behnken experimental design (RSD), and the results were statistically tested using an analysis of variance. Density functional theory (DFT) modeling was employed to characterize the interactions between the antibiotics and the CAG F400 surface. For the individual adsorption process, adsorption capacities (qe) of 1.61 mmol g−1 for SMX and 1.10 mmol g−1 for MNZ were obtained. The adsorption isotherm model that best fit experimental data was the Radke–Prausnitz isotherm model. The adsorption mechanism occurs through electrostatic and π-π dispersive interactions. For the binary adsorption process, the total binary adsorption capacity achieved was 1.13 mmol g−1, evidencing competitive adsorption. The significant factors that determine the removal of SMX and MNZ from a binary solution were the solution pH and the initial concentration of antibiotics. From DFT studies, it was found that SMX adsorption on CAG F400 was favored with adsorption energy (Eads) of −10.36 kcal mol−1. Finally, the binary adsorption results corroborated that the adsorption process was favorable for both molecules.

Critical Review and Discussion of the Nonlinear Form of Radke–Prausnitz Model in Adsorption Solid–Liquid Phases

The Radke–Prausnitz model, a typical three-parameter model belonging to the Langmuir–Freundlich-type equation, is increasingly being used to correlate the equilibrium data of various adsorption processes. However, very few published works provide the correct information on (1) the nonlinear form of this model, (2) the units of its parameters, and (3) its original citation. This work provides a critical analysis of the Radke–Prausnitz model with special emphasis on promoting its proper application in adsorption research. The correct expression and citation of the models used in adsorption studies are provided. The correct units of its parameters aRP, bRP, and β are L/kg, (mol/kg)/(mol/L)β, and unitless when the solution phase concentration Ce is given in mol/L and the adsorbed phase concentration qe is defined in mol/kg. The Radke–Prausnitz model can be reduced to the Henry, Freundlich, Langmuir, or Redlich–Peterson model in some special cases. The Radke—Prausnitz model is valid when the exponent β is in the range of 0≤β≤1. A new adsorption equilibrium constant of this model is introduced. The feasibility of using the new equilibrium constant to calculate the thermodynamic parameters (ΔG°, ΔH°, and ΔS°) of adsorption processes is discussed herein.

Effective removal of hexavalent chromium from water by sustainable nano-scaled waste avocado seeds: adsorption isotherm, thermodynamics, kinetics, and error function

In the current investigation, an efficient low-cost nano-scaled material was prepared from waste avocado seeds (NASs) and employed as a sustainable nanosorbent for removal of hexavalent chromium ions. The adsorption and surface characteristics with respect to the availability of functional groups, basic component elements, and structural properties of NASs were achieved by different techniques. Analysis of NASs referred to the presence of carbon and oxygen contents providing 97.21%. The NASs particles were homogenously identified and ranged between 18.68 and 19.05 nm. The impact of various affecting adsorption parameters on hexavalent chromium ions removal was elaborated and optimized at pH 2.0, NASs dose 10 mg, contact time 30 min, and temperature 25 °C by the batch adsorption assay. Fifteen linear and nonlinear modeling tests were applied to evaluate the adsorption isotherms and arranged in the following fitting order: Tempkin < BET < Dubinin-Radushkevich < Generalized < Halsey ˂ Flory–Huggins < Freundlich < Harkins–Jura ˂ Langmuir for linear formulas and Weber-van Vliet < Langmuir < Generalized < Radke–Prausnitz (II) < Radke–Prausnitz (III) < Fritz-Schlunder IV < Baudu < Multilayer < Fritz-Schlunder V < Toth for nonlinear formulas with 2 to 5 parameters. Linear and nonlinear pseudo-second-order models, intraparticle diffusion, and Elovich models were also scrutinized, and both pore diffusion and film were similarly involved in the rate-limiting step. The values of ΔS° (0.21 kJ/mol), ΔH° (− 41.02 kJ/mol) and ΔG° (− 28.30 to − 19.97 kJ/mol) at high concentration of hexavalent chromium (50 mg L−1) and a temperature range of 20–60 °C reflected the disordering, spontaneously exothermic adsorption process. The activation energy (Ea) was also confirmed to include the diffusion process at the activation energy in the rate-limiting step. The potential application of NASs in hexavalent chromium removal from wastewater, seawater, and tap water as real aqueous matrices referred to excellent percentage removal values in the range from 98.44 to 98.86%. Based on the outlined results, one can deduce that excellent performance and efficiency for removal of high hexavalent chromium concentration at high temperature, low nanosorbent mass, and low pH from different aqueous matrices were accomplished by the evaluated NAS nanosorbent. Accordingly, the investigated NAS nanosorbent is recommended to apply in high stress industrial and wastewater treatment plants.

How to avoid mistakes in treating adsorption isotherm data (liquid and solid phases): Some comments about correctly using Radke-Prausnitz nonlinear model and Langmuir equilibrium constant

Two flaws in concepts were identified and discussed in the paper (“Removal of Pb(II) from contaminated waters using cellulose sulfate/chitosan aerogel: Equilibrium, kinetics, and thermodynamic studies”. J. Environ. Manag. 286, 112167; https://doi.org/10.1016/j.jenvman.2021.112167). In the literature, the Radke–Prausnitz model is expressed in different forms, but some of them are incorrect. The first flaw is related to the nonlinear form of the Radke–Prausnitz model. The nonlinear form of this three parameters model is expressed correctly as qe=ARPBRPCeβARP+BRPCeβ–1. The units of two parameters are ARP (L/kg) and BRP [(mol/kg)/(mol/L)β] by considering qe (mol/kg) and Ce (mol/L). The limitation for its exponent is 0≤ β ≤ 1. This model is developed by two authors (Radke and Prausnitz). The correct paper (DOI: 10.1021/i160044a003) cited as reference of this model is “Radke, C.J., Prausnitz, J.M., 1972. Adsorption of organic solutes from dilute aqueous solution of activated carbon. Ind. Eng. Chem. 11, 445–451”. The second is the misconception about the unit of the Langmuir constant (KL; L/mg). The correct unit of KL is litre per milligram of adsorbate (i.e., Pb ions), not litre per milligram of adsorbent (the cellulose sulfate/chitosan aerogel material as reported by Najaflou and co-workers. They proposed a new equation [KL (L/mg) × m/V (mg/L)] to convert the Langmuir constant and then applied it to calculate the thermodynamic parameters of the adsorption process. The m/V is a solid/liquid ratio (g/L or kg/L). However, this conversion and application are mistakes that were thoroughly discussed in this paper. The correction is KEqo=1γAdsorbate×KLLmol×ComolL, with C° (1 mol/L by definition) being the standard state of solute and γAdsorbate (dimensionless) being the activity coefficient of adsorbate in solution. To avoid unexpected mistakes, the present authors suggest that researchers should have a correct citation (citing the original reference instead of using secondary references) and check the consistency of units (i.e., the constants of adsorption models) carefully.

Adsorption of Crystal Violet Dye from Aqueous Solution using Industrial Pepper Seed Spent: Equilibrium, Thermodynamic, and Kinetic Studies

The economic viability of adsorbing crystal violet (CV) using pepper seed spent (PSS) as a biosorbent in an aqueous solution has been studied. A parametrical investigation was conducted considering parameters like initial concentration of dye, time of contact, pH value, and temperature variation. The analysis of experimental data obtained was carried out by evaluating with the isotherms of Freundlich, Sips, Tempkin, Jovanovic, Brouers–Sotolongo, Toth, Vieth–Sladek, Radke–Prausnitz, Langmuir, and Redlich–Peterson. The adsorption kinetics were studied by implementing the Dumwald-Wagner, Weber-Morris, pseudo-first-order, pseudo-second-order, film diffusion, and Avrami models. The experimental value of adsorption capacity ([Formula: see text]) was observed to be quite close to the Jovanovic isotherm adsorption capacity ([Formula: see text]) at ([Formula: see text]), coefficient of correlation of 0.945. The data validation was found to conform to that of pseudo-second-order and Avrami kinetic models. The adsorption process was specified as a spontaneous and endothermic process owing to the thermodynamic parametrical values of [Formula: see text], [Formula: see text], and [Formula: see text]. The value of [Formula: see text] is an indicator of the process’s physical nature. The adsorption of CV to the PSS was authenticated from infrared spectroscopy and scanning electron microscopy images. The interactions of the CV-PSS system have been discussed, and the observations noted suggest PSS as a feasible adsorbent to extract CV from an aqueous solution.

Thermodynamic parameters of liquid–phase adsorption process calculated from different equilibrium constants related to adsorption isotherms: A comparison study

Adsorption thermodynamics is an integral part of the study of adsorption and plays a vital role in estimating adsorption mechanism (i.e., physisorption and chemisorption). For the liquid-phase adsorption, the equilibrium constant of some adsorption isotherm models (Langmuir, modified Langmuir, Langmuir–Freundlich, modified Langmuir–Freundlich, Liu, Khan, Sips, Hill, Toth, Redlich–Peterson, Koble–Corrigan, and Radke–Prausnitz models) and the constant of Henry and Freundlich models have been directly or indirectly applied for calculating the corresponding thermodynamic parameters (∆G°, ∆H°, and ∆S°). This study explored the effects of the selection of (1) the unit of adsorption isotherm (qevs. Ce), (2) the equilibrium constant of adsorption isotherm model, and (3) the linear and nonlinear forms of the van’t Hoff equation on the value (sign and magnitude) of the thermodynamic parameters. A commercial activated carbon was selected as a typical adsorbent to adsorb methylene green dye (target adsorbate) in solution. Results indicated that the constants of the Henry and Freundlich models could not be applied for calculating the thermodynamic parameters. The equilibrium constants of the modified Langmuir and modified Langmuir–Freundlich models were not suitable for calculating the thermodynamic parameters in this study compared to the other equilibrium constants of the Langmuir, Langmuir–Freundlich, Khan, Liu, Sips, Redlich–Peterson, Toth, Hill, Radke–Prausnitz, and Koble–Corrigan models. The thermodynamic parameters were calculated from thermodynamic equilibrium constant derived from the equilibrium constant of the Redlich–Peterson model or the Radke–Prausnitz model (the van’t Hoff equation: adj-R2 = 0.9999).

Fabrication of chitosan/polyvinyl alcohol/amine modified carbon nanotube composite films for rapid chromate removal

AbstractComposite adsorbent films with amine and hydroxyl functionalities were synthesized from chitosan (CS), polyvinyl alcohol (PVA), and amine‐modified carbon nanotubes (a‐MWCNT) by solvent casting method. Weight proportions of CS to PVA and weight percent of a‐MWCNT were optimized to achieve highest chromate removal capacity. Structural characteristics of the composites were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and thermal gravimetric analysis. Accordingly, incorporation of a‐MWCNT to CS/PVA structure resulted in the generation of nanochannels, which enhanced adsorption capacity. Moreover, the composite comprising 0.4% wt. a‐MWCNT provided over 99% of Cr (VI) removal from 50 mg L−1 Cr (VI) solution within five minutes of contact time. Redlich–Peterson and Radke–Prausnitz isotherm models provided the highest conformity to adsorption data. Maximum chromate sorption capacity of CS/PVA/a‐MWCNT composite film was determined as 134.2 mg g−1 being 172% higher than that of CS/PVA. Regeneration was best achieved in 1.0 M NaOH and the composite was shown to retain at least 70% of its original capacity after five consecutive adsorption–desorption cycles.

Trapping synthetic dye molecules using modified lemon grass adsorbent

Physicochemical method was used to prepare lemongrass leaf activated carbon (LLAC) for removal of Remazol brilliant violet 5 R (RBV5R) dye from aqueous solutions. The surface area, mesopore surface area, total pore volume and average pore diameter of the LLAC are 836.04 m2/g, 598.6 04 m2/g, 0.472 04 cm3/g and 3.62 nm, respectively. The surface functional groups of LLAC before adsorption showed the existence of C–H, O–H, C-O, C = O, C = C, CH3, N–O and C–N; they are significantly altered after adsorption. The equilibrium data were fitted into Freundlich, Langmuir, Dubinin Radushkevich, Temkin, Koble Corrigan, Vieth Sladek, Radke Prausnitz and Brouers Sotolongo isotherm models. The Koble Corrigan and Freundlich models gave the best fit judging from the correlation coefficient (R2). The monolayer adsorption capacities (qm) obtained for Langmuir and Koble Corrigan isotherm models are 125 and 342.9 mg/g respectively. Kinetic data were fitted using pseudo-first order, pseudo-second order, intraparticle diffusion, Elovich, Boyd and Avrami models respectively. Thermodynamic parameters (ΔS0, ΔH0and ΔG0) were estimated. The mean adsorption energy Ea was 2.811 kJ/mol signifying that the adsorption is physically controlled. This study revealed that lemongrass leaf is effective in removing RBV5R dye from aqueous systems.

Sustainable Low-Concentration Arsenite [As(III)] Removal in Single and Multicomponent Systems Using Hybrid Iron Oxide-Biochar Nanocomposite Adsorbents-A Mechanistic Study.

Rice and wheat husks were converted to biochars by slow pyrolysis (1 h) at 600 °C. Iron oxide rice husk hybrid biochar (RHIOB) and wheat husk hybrid biochar (WHIOB) were synthesized by copyrolysis of FeCl3-impregnated rice or wheat husks at 600 °C. These hybrid sorbents were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), SEM–energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, physical parameter measurement system, and Brunauer–Emmett–Teller (BET) surface area techniques. Fe3O4 was the predominant iron oxide present with some Fe2O3. RHIOB and WHIOB rapidly chemisorbed As(III) from water (∼24% removal in first half an hour reaching up to ∼100% removal in 24 h) at surface Fe–OH functions forming monodentate ≡Fe–OAs(OH)2 and bidentate (≡Fe–O)2AsOH complexes. Optimum removal occurred in the pH 7.5–8.5 range for both RHIOB and WHIOB, but excellent removal occurred from pH 3 to 10. Batch kinetic studies at various initial adsorbate–adsorbent concentrations, temperatures, and contact times gave excellent pseudo-second-order model fits. Equilibrium data were fitted to different sorption isotherm models. Fits to isotherm models (based on R2 and χ2) on RHIOB and WHIOB followed the order: Redlich–Peterson > Toth > Sips = Koble–Corrigan > Langmuir > Freundlich = Radke–Prausnitz > Temkin and Sips = Koble–Corrigan > Toth > Redlich–Peterson > Langmuir > Temkin > Freundlich = Radke–Prausnitz, respectively. Maximum adsorption capacities, QRHIOB0 = 96 μg/g and QWHIOB0 = 111 μg/g, were obtained. No As(III) oxidation to As(V) was detected. Arsenic adsorption was endothermic. Particle diffusion was a rate-determining step at low (≤50 μg/L) concentrations, but film diffusion controls the rate at ≥100–200 μg/L. Binding interactions with RHIOB and WHIOB were established, and the mechanism was carefully discussed. RHIOB and WHIOB can successfully be used for As(III) removal in single and multicomponent systems with no significant decrease in adsorption capacity in the presence of interfering ions mainly Cl–, HCO3–, NO3–, SO42–, PO43–, K+, Na+, Ca2+. Simultaneous As(III) desorption and regeneration of RHIOB and WHIOB was successfully achieved. A very nominal decrease in As(III) removal capacity in four consecutive cycles demonstrates the reusability of RHIOB and WHIOB. Furthermore, these sustainable composites had good sorption efficiencies and may be removed magnetically to avoid slow filtration.

Fibrous adsorbent derived from sulfonation of cotton waste: application for removal of cadmium sulfide nanoparticles from aquatic media

In the present research, the performance of the cellulose sulfate microfibers (CSMFs) was investigated for the removal of cadmium sulfide nanoparticles (CdS NPs). At first, cotton waste was sulfonated by chlorosulfonic acid. The high sulfur content of the CSMFs (6.54%) and the absorbance bands appeared at 610 cm−1 (symmetric stretching vibrations) and 1205 and 1180 cm−1 (asymmetric stretching vibrations) in the FT-IR spectrum of CSMFs confirmed the successful modification of cotton microfibers. Optimizing the adsorption process was achieved using the response surface methodology. The impacts of the initial concentration of CdS NPs, contact time, total dissolved solids (TDS), and adsorbent concentration on the removal efficiency were assessed. The highest removal efficiency (about 100%) was obtained under optimum conditions. By increasing the TDS, the removal efficiency decreased slightly. University of Tehran, Radke–Prausnitz, and Redlich–Peterson models exhibited low error values. The high maximum adsorption capacity of 5533 mg g−1 was due to the high content of anionic surface groups. The kinetics data were consistent with the Elovich, intraparticle diffusion, and pseudo-second-order models. The rate constant of the pseudo-second-order model decreased by decreasing the concentration of CdS NPs. The adsorbent recovery decreased about 10% after four cycles of regeneration.

Lignin-chitosan blend for methylene blue removal: Adsorption modeling

In this work, a comprehensive comparative analysis of various approaches for the modeling of the adsorption process was carried out to understand the adsorption isotherm and kinetics. The evaluated isotherm models included Langmuir, Freundlich, Dubinin–Radushkevich, Tempkin, Flory–Huggins, Hill, Redlich–Peterson, Sips, Toth, Koble–Corrigan, Khan, Radke–Prausnitz, Brunauer–Emmett–Teller, Frenkel–Halsey–Hill, MacMillan–Teller, Harkins–Jura, Halsey, Henderson, Fritz–Schluender, Vieth-Sladek, Valenzuela-Myers, Jovanovic, Baudu and Elovich. The evaluated kinetic models included pseudo-first-order, pseudo-second-order, Avrami, Adsorption kinetic and Bangham. For a detailed comparison, the experimentally measured adsorption data of methylene blue from water effluent on a lignin and chitosan blend were used. It was demonstrated that current kinetic models and isotherms provide some correlative method and view to the adsorption data that are useless without prior experimental data. It was revealed that the best results were obtained for Langmuir-1 form isotherm and the worst one was obtained for Harkins–Jura isotherm. In terms of kinetics, the linearized Form 2 of the pseudo-second-order indicated better goodness of fit to the experimental kinetic data.

Experimental investigation of adsorption capacity of anthill in the removal of heavy metals from aqueous solution

AbstractIn the present work, the adsorption capacity of anthill was investigated as a low‐cost adsorbent to remove the heavy metal ions, lead (II) ion (Pb2+), and zinc (II) ion (Zn2+) from an aqueous solution. The equilibrium adsorption isotherms of the heavy metal ions were investigated under batch process. For the study we examined the effect of the solution's pH and the initial cations concentrations on the adsorption process under a fixed contact time and temperature. The anthill sample was characterized using a scanning electron microscope (SEM), X‐ray fluorescence (XRF), and Fourier transform infrared (FTIR) techniques. From the SEM analysis, structural change in the adsorbent was a result of heavy metals adsorption. Based on the XRF analysis, the main composition of the anthill sample was silica (SiO2), alumina (Al2O3), and zirconia (ZrO2). The change in the peaks of the spectra before and after adsorption indicated that there was active participation of surface functional groups during the adsorption process. The experimental data obtained were analyzed using 2‐ and 3‐parameter isotherm models. The isotherm data fitted very well to the 3‐parameter Radke–Prausnitz model. It was noted that Pb2+ and Zn2+ can be effectively removed from aqueous solution using anthill as an adsorbent.

Removal of ibuprofen from aqueous solution by functionalized strong nano-clay composite adsorbent: kinetic and equilibrium isotherm studies

The functionalized nano-clay composite adsorbent was prepared, and its properties were characterized using FT-IR, XRD and SEM techniques. The synthesized nano-clay composite was studied with regard to its capacity to remove ibuprofen under different adsorption conditions such as varying pH levels (5–9), initial ibuprofen concentrations (3, 5 and 10 mg L−1), contact time, and the amount of adsorbent (0.125, 0.25, 0.5 and 1 g). In order to evaluate the nanocomposite adsorption capacity, the adsorption results were assessed using nine isotherm models. The results showed that the optimum adsorption pH was 6 and that an increase or decrease in the pH reduced the adsorption capacity. The adsorption process was fast and reached equilibrium after 120 min. The maximum efficacy of ibuprofen removal was approximately 95.2%, with 1 g of adsorbent, 10 mg L−1 initial concentration of ibuprofen, 120 min contact time and pH = 6. The optimal adsorption isotherm models were the Freundlich, Fritz–Schlunder, Redlich–Peterson, Radke–Prausnitz, Sip, Toth and Khan models. In addition, four adsorption kinetic models were employed for adsorption system evaluation under a variety of experimental conditions. The kinetic data illustrated that the process is very fast, and the reaction followed the Elovich kinetic model. Therefore, this nano-clay composite can be used as an effective adsorbent for the removal of ibuprofen from aqueous solutions, such as water and wastewater.

Kinetic and isotherm studies for adsorption of Pb(II) from aqueous solution onto coconut shell activated carbon

Coconut shell (CS) was used as a neglected agricultural waste to produce the activated carbon through chemical activation process with phosphoric acid (activated coconut shell (ACS)). This process is easy and environmental friendly. The activated carbon (ACS) as biosorbent was evaluated for sorption of lead from wastewater using a series of batch adsorption experiments and compared with pyrolysis CS. The characterization results showed that this biosorbent (ACS) has high surface area and functional groups. The efficiency of adsorption process was studied at various parameters: pH, contact time, initial concentration, and competing ions for the removal of Pb(II) ions from aqueous solution. Adsorption equilibrium data were analyzed by the two parameters models (Langmuir, Freundlich, Temkin, and R–D) and the three parameters models (Generalized, Toth, Radke–Prausnitz, and Fritz–Sclunder models). The adsorption equilibrium data was well described by Langmuir and the monolayer adsorption capacities were found to be 49.92 and 26.14 mg/g onto ACS and CS, respectively, which are agreement with those obtained from the three-parameter isotherm models. The experimental kinetic data were best fitted with Bangham’s, Weber–Morris and pseudo-second-order models. The diffusion mechanism was controlled by both boundary layer and pore diffusion for the two adsorbents CS and ACS. It is noteworthy that the effect of Cd(II) and Fe(III) on the adsorption of Pb(II) is very weak, even with high concentration of Cd(II) or Fe(III), which means that the investigated adsorbents have higher affinity for sorption of Pb(II) than that of the other competing ions. The results showed that ACS can be used as a low-cost adsorbent for the removal of Pb(II) ions from aqueous solutions.

Application of taguchi L16 orthogonal array design to optimize hydrazine biosorption by Sargassum ilicifolium

In this work, Taguchi L16 experimental design was applied to optimize biosorption of hydrazine by Sargassum ilicifolium in a batch system. Biosorption tests were performed with four factors concentration, pH, biosorbent dosage, and agitation time at four different levels. Optimal experimental conditions were determined by calculated signal‐to‐noise ratios. The best conditions for biosorption of hydrazine were determined by the Taguchi method and desirability approach as initial hydrazine concentration of 135 mg/L, pH = 7.5, biosorbent dose of 0.1 g/L and time 90 min. Furthermore, thermodynamic, isotherm and kinetic studies were performed to explain the biosorption mechanism. The kinetic of hydrazine removal followed the pseudo‐second‐order model. A nonlinear regression was applied to fit the experimental data with several isotherm models. The Redlich–Peterson and Radke–Prausnitz isotherms showed the best concordance as equilibrium models. Nature of possible interactions between the functional groups of S. ilicifolium and hydrazine was confirmed by FTIR spectra of raw and hydrazin‐loaded alga. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1450–1457, 2016

Analysis of two-parameter and three-parameter isotherms by nonlinear regression for the treatment of textile effluent using immobilized Trametes versicolor: comparison of various error functions

The ability of the immobilized Trametes versicolor, as biosorbent, to degrade the textile effluent, in terms of chemical oxygen demand and color, was studied under batch conditions. The removal efficiencies were calculated for the effect of initial concentrations, biomass dosages, shaking, and nutrients. Equilibrium data were analyzed using, two-parameter isotherms: Langmuir, Freundlich, BET, Flory–Huggins, Temkin, Jovanovic, Harkins–Jura and Halsey. Three-parameter isotherms: Redlich–Peterson, Sips, Khan, Toth, Langmuir–Freundlich, Fritz–Schlunder, Koble–Corrigan, Hill, Brouers–Sotolongo, and Radke Prausnitz, using nonlinear regression. The model parameters were optimized using Microsoft Excel Solver Add-Ins function. The best isotherm was identified by error analysis, using nine different error functions: residual root mean square error, normalized standard deviation, average relative error, sum of the squares of the error, sum of the absolute errors, hybrid fractional error function, residual variance, Marquardt’s percent standard deviation, and chi-square test (χ2).

Tetracycline adsorption onto activated carbons produced by KOH activation of tyre pyrolysis char

Tyre pyrolysis char (TPC), produced when manufacturing pyrolysis oil from waste tyre, was used as raw material to prepare activated carbons (ACs) by KOH activation. KOH to TPC weight ratios (W) between 0.5 and 6, and activation temperatures from 600 to 800 °C, were used. An increase in W resulted in a more efficient development of surface area, microporosity and mesoporosity. Thus, ACs derived from TPC (TPC-ACs) with specific surface areas up to 814 m2 g−1 were obtained. TPC, TPC-ACs and a commercial AC (CAC) were tested for removing Tetracycline (TC) in aqueous phase, and systematic adsorption studies, including equilibrium, kinetics and thermodynamic aspects, were performed. Kinetics was well described by the pseudo-first order model for TPC, and by a pseudo second-order kinetic model for ACs. TC adsorption equilibrium data were also fitted by different isotherm models: Langmuir, Freundlich, Sips, Dubinin–Radushkevich, Dubinin–Astokov, Temkin, Redlich–Peterson, Radke–Prausnitz and Toth. The thermodynamic study confirmed that TC adsorption onto TPC-ACs is a spontaneous process. TC adsorption data obtained in the present study were compared with those reported in the literature, and differences were explained in terms of textural properties and surface functionalities. TPC-ACs had similar performances to those of commercial ACs, and might significantly improve the economic balance of the production of pyrolysis oil from waste tyres.

Kinetic and isotherm error optimization studies for adsorption of atrazine and imidacloprid on bark of Eucalyptus tereticornis L.

ABSTRACTThe aim of this study was to establish the bark of Eucalyptus tereticornis L. (EB) as a low cost bio-adsorbent for the removal of imidacloprid and atrazine from aqueous medium. The pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich and intra-particle diffusion (IPD) models were used to describe the kinetic data and rate constants were evaluated. Adsorption data was analysed using ten 2-, 3- and 4-parameter models viz. Freundlich, Jovanovic, Langmuir, Temkin, Koble–Corrigan, Redlich–Peterson, Sips, Toth, Radke–Prausnitz, and Fritz-Schluender isotherms. Six error functions were used to compute the best fit single component isotherm parameters by nonlinear regression analysis. The results showed that the sorption of atrazine was better explained by PSO model, whereas the sorption of imidacloprid followed the PFO kinetic model. Isotherm model optimization analysis suggested that the Freundlich along with Koble–Corrigan, Toth and Fritz-Schluender were the best models to predict atrazine and imidacloprid adsorption onto EB. Error analysis suggested that minimization of chi-square (χ2) error function provided the best determination of optimum parameter sets for all the isotherms.

Removal of 4-nitrophenol from aqueous solution by adsorption onto activated carbon prepared from Acacia glauca sawdust

The present paper deals with a complete batch adsorption study of 4-nitrophenol (4NP) from aqueous solution onto activated carbon prepared from Acacia glauca sawdust (AGAC). The surface area of the adsorbent determined by methylene blue method is found to be 311.20 m(2)/g. The optimum dose of adsorbent was found to be 2 g/l with 4NP uptake of 25.93 mg/g. The equilibrium time was found to be 30 minutes with the percentage removal of 96.40 at the initial concentration of 50 ppm. The maximum removal of 98.94% was found to be at pH of 6. The equilibrium and kinetic study revealed that the Radke-Prausnitz isotherm and pseudo second order kinetics model fitted the respective data well. In the thermodynamic study, the negative value of Gibbs free energy change (-26.38 kJ/mol at 30°C) and enthalpy change (-6.12 kJ/mol) showed the spontaneous and exothermic nature of the adsorption process.