Redlich-Peterson Isotherm Equations Research Articles

Removal of 4-Picoline from Aqueous Solution by Adsorption onto Bagasse Fly Ash and Rice Husk Ash: Equilibrium, Thermodynamic, and Desorption Study

This paper deals with the adsorption of 4-picoline (4Pi) from aqueous solutions onto bagasse fly ash (BFA) and rice husk ash (RHA) as adsorbents. We discuss the effect of several parameters, such as initial pH, adsorbent dose, contact time, initial concentration, and temperature, on the batch adsorption. We collected equilibrium sorption isotherm data, which could be well-represented by the Redlich-Peterson, Toth, and Radke-Prausnitz isotherm equations. The maximum removal of 4Pi was found to be 46% and 96% by BFA, and 55% and 95% by RHA for lower (50 mg/L) and higher (600 mg/L) concentration of 4Pi, respectively, with sorbent dosages of 5 g/L for BFA and 20 g/L for RHA. Adsorption was found to be very fast, and about 72–90% of 4Pi removal was achieved in the initial 5 min of contact time. We found the sorption of 4Pi on BFA and RHA to be endothermic in nature. The spent adsorbents can be dried and used as a cofuel in boiler furnaces/incinerators.

Physicochemical and geochemical characteristics of raw marine sediment used in fluoride removal

The study was directed to use raw marine sediment in the removal of fluoride. The sediment was mainly composed of calcite, magnesium-calcite and aragonite. The effect of the initial fluoride concentration, pH and the contact time was studied at room temperature to determine the adsorption capacity of the sediment. The optimum adsorption capacity was observed at pH values of 5 and 6.2. The adsorption process was fast and the equilibrium was reached within 60 min. For fluoride solutions of 10 and 15 mg/L, 100% removal was obtained onto 0.1 g of raw marine sediment. Pseudo–first-order, pseudo–second-order, Elovich and intra-particle diffusion equations were used to deduce the kinetic data. The adsorption mechanism was rather complex process, and the intra-particle diffusion was not the only rate-controlling step. The equilibrium data were tested using thirteen isotherm models (Langmuir, Freundlich, Tempkin, Dubinin-Radushkevich, Erunauer-Emmett-Teller, Flory-Huggins, Non-ideal competitive adsorption, Generalized, Redlich Peterson, Khan, Sips, Koble Corrigan and Toth isotherm equations). Five different error functions were applied. For the sorption of fluoride process, the calculated activation energy and the free energy were of 0.707 and −14.491 kJ /mol, respectively.

A new linear form analysis of Redlich–Peterson isotherm equation for the adsorptions of dyes

Many papers report that accuracy of the Redlich–Peterson (R–P) isotherm equation (three parameters) is higher than those of Langmuir and Freundlich isotherm equations (two parameters). This paper first explains why the accuracy of the R–P isotherm equation is equal to or higher than that of two parameters isotherm equations. This study suggests a new exponential linear equation with exponent variable α, and solves the most suitable α value with the aid of Microsoft Excel and Sigma Plot 9.0. This exponential method is quick, simple, and accurate for fitting the R–P isotherm equation to experimental data sets of adsorption systems compared with a logarithmical linear form frequently used previously. This investigation prepares four kinds of pistachio shell activated carbons with various doses of NaOH for studying isotherm equilibrium adsorptions of three dyes. The R–P isotherm equation best fit adsorption system data sets studied in this work.

Removal of a Binary Dye Mixture of Congo Red and Malachite Green From Aqueous Solutions Using a Bentonite Adsorbent

AbstractAn important application of clay is as a solid adsorbent for industrial dyes. The aim of the present work was to carry out an experimental—theoretical study of the adsorption of dye mixtures, namely malachite green (MG) and Congo red (CR), by bentonite. Adsorption studies were conducted after evaluation of the impact of several parameters, including pH, adsorbate dose, and contact time, on the removal of MG and CR. The pH of the dye solution is strongly affected by the chemistry of both the dye molecules and of the adsorbent in an aqueous solution. Where both dye molecules exist in solution, the optimum pH was found to be 8.2 in order to achieve the maximum adsorption of both MG and CR. Preliminary studies showed that 60 min of contact time is sufficient to reach adsorption equilibrium. The adsorption studies were carried out using 1.0 g samples of bentonite. The amount of dye adsorbed was found by application of classical least squares to the synthetic dye mixtures. Data from equilibrium adsorption on bentonite were analyzed by Freundlich, Langmuir, Redlich-Peterson, and Temkin isotherm equations using regression analysis for non-linear forms of those equations. For binary-mixture analysis, isotherm parameters were determined from single-component adsorption studies and the theoretical amount of dye adsorbed was calculated using an extended Langmuir isotherm. Non-linear error analysis showed that the Temkin and Redlich-Peterson isotherms gave the best fits to the equilibrium data for adsorptive removal of MG and CR by bentonite.

Equilibrium studies on sorption of an anionic dye onto acid activated water hyacinth roots

The inappropriate disposal of dyes in wastewater constitutes an environmental problem and can cause damage to the ecosystem. Present investigation deals with the utilization of water hyacinth roots (collected from the ponds) as adsorbent for the removal of anionic dye from its aqueous solutions. Batch studies were conducted to evaluate the adsorption capacity of the dye, Congo red on the sorbent with respect to the variations in initial pH, contact time and initial dye concentration and the adsorbent. The effective pH for better adsorption of Congo red on water hyacinth roots was found to be 6.0. Equilibrium was reached in about 3 h contact time. Equilibrium isotherms for the adsorption of Congo red on water hyacinth root were analyzed by the Freundlich, Langmuir and Redlich–Peterson isotherm equations. Results showed that Redlich–Peterson isotherm best-fits with the Congo red adsorption isotherm data on all initial dye concentrations. The Freundlich isotherm also showed comparable fit.

Adsorption of α-picoline onto rice husk ash and granular activated carbon from aqueous solution: Equilibrium and thermodynamic study

Abstract In the present study, the batch adsorption experiments were carried out to calculate the adsorption capacities of rice husk ash (RHA) and commercial grade granular activated carbon (GAC) for the adsorption of α-picoline (Pi) from aqueous solutions. The effect of various parameters like initial pH (pH0), adsorbent dose (m), contact time (t), initial concentration (C0) and temperature (T) on the adsorption of Pi from the aqueous solutions was studied. The maximum uptake of Pi was observed to be 2.34 mg g−1 at lower concentration (50 mg dm−3) and 15.46 mg g−1 at higher concentration (600 mg dm−3) using 20 kg m−3 of RHA and the maximum uptake of Pi by GAC was observed to be 4.55 mg g−1 at lower concentration (50 mg dm−3) and 36 mg g−1 at higher concentration (600 mg dm−3) using 10 kg m−3 of GAC at normal temperature. The equilibrium data can be best represented by Radke–Prausnitz isotherm equation. However, Toth and Redlich–Peterson isotherm equations also represent the equilibrium data adequately. The values of change in Gibb's free energy ( Δ G ° ), enthalpy (ΔH°) and entropy (ΔS°) were calculated. Thermodynamic study revealed that the adsorption of Pi onto RHA and GAC is an endothermic process. Isosteric heat of adsorption was found to be decreasing with an increase in surface loading. The acidic water and dilute acids showed higher desorption efficiency for Pi from RHA and GAC. Thus GAC can be regenerated by using acidic water and acids. However, RHA can be disposed off by using it as a fuel in furnaces to recover its energy value.

Removal of Cu(II) from aqueous solution by adsorption onto functionalized SBA-16 mesoporous silica

Functionalized SBA-16 mesoporous silica with –SH groups was synthesized using one-pot method. The resulting material was characterized by powder X-ray diffraction, nitrogen gas sorption, FT-Raman spectroscopy. The solid was employed as a Cu(II) adsorbent from aqueous solutions at room temperature. The effects of several variables (stirring time, pH, metal concentration and presence of other ions in the medium) were studied using the batch technique. The results showed that by controlling an optimum molar ratio of 3–4 between tetraethyl orthosilicate (TEOS) and 3-mercaptopropyltriethoxysilane (TMMPS), the synthesized material possessed high order and adsorption capacity for Cu(II) ions though the pore size decreased probably due to the attachment of the organic functional groups in the mesopore channels. The maximum Cu(II) adsorption on this adsorbent occurred in the range of pH 5–6 with an adsorption maximum of 36.38 mg/g. The adsorption of Cu(II) on functionalized SBA-16 mesoporous fitted well to the Redlich–Peterson isotherm equation ( r 2 = 0.9999) followed by the Langmuir equation ( r 2 = 0.9847). The involved mechanism might be the adsorption through ligand exchange with the –SH group. The adsorptive competing cations in the aqueous solution had a little effect on the adsorption of Cu(II) on this adsorbent. The presence of different anions (Cl −, NO 3 - , SO 4 2 - , OAc − and Cit −) influenced the Cu(II) adsorption in the order of NO 3 - < OAc - < SO 4 2 - < Cit - < Cl - . Even after seven regeneration cycles, functionalized SBA-16 mesoporous had a Cu(II) adsorption amount of over 23 mg/g and could be easily regenerated through acid washing, showing a promising application for the treatment of wastewater containing Cu(II) ions.

Biosorption of Rhodamine B and Malachite green from aqueous solutions by Tamarindus indica fruit shells

The removal of rhodamine B and malachite green from aqueous solutions was studied in batch adsorption systems using Tamarindus Indica fruit shells as sorbents. The well known Freundlich, Langmuir and Redlich-Peterson isotherm equations were applied to the equilibrium sorption data obtained. The sorption dynamics were found to obey the pseudo-second order rate equation and particle diffusions appear to control the overall rates. Increase of both pH and temperature resulted in increased sorption and the thermodynamic parameters like ΔG, ΔH and ΔS were evaluated.

STUDIES ON THE ADSORPTION OF FURFURAL FROM AQUEOUS SOLUTION ONTO LOW-COST BAGASSE FLY ASH

The present study deals with the sorptive removal of furfural from aqueous solution by carbon-rich bagasse fly ash (BFA). Batch studies were performed to evaluate the influence of various experimental parameters, namely, initial pH (p H 0), adsorbent dose, contact time, initial concentration, and temperature on the removal of furfural. Optimum conditions for furfural removal were found to be p H 0 ≈ 5.5, adsorbent dose ≈4 g/L of solution, and equilibrium time ≈4 h. The adsorption followed pseudo-second-order kinetics. The effective diffusion coefficient of furfural is of the order of 10−13 m2/s. Equilibrium adsorption data on BFA was analyzed by Freundlich, Langmuir, Dubnin-Radushkevich, Redlich-Peterson, and Temkin isotherm equations using regression and error analysis. The Redlich-Peterson isotherm was found to best represent the data for furfural adsorption onto BFA. Adsorption of furfural on BFA is favorably influenced by a decrease in the temperature of the operation. Values of the change in entropy (ΔS 0) and heat of adsorption (ΔH 0) for furfural adsorption on BFA were negative. The high negative value of change in Gibbs free energy (ΔG 0) indicates the feasible and spontaneous adsorption of furfural on BFA.

Pyridine sorption from aqueous solution by rice husk ash (RHA) and granular activated carbon (GAC): Parametric, kinetic, equilibrium and thermodynamic aspects

The present study deals with the adsorption of pyridine (Py) from synthetic aqueous solutions by rice husk ash (RHA) and commercial grade granular activated carbon (GAC) and reports on the kinetic, equilibrium and thermodynamic aspects of Py sorption. Batch sorption studies were carried out to evaluate the effect of various parameters, such as adsorbent dose ( m), initial pH (pH 0), contact time ( t), initial concentration ( C 0) and temperature ( T) on the removal of Py. The maximum removal of Py is found to be ∼96% and ∼97% at lower concentrations (<50 mg dm −3) and ∼79.5% and ∼84% at higher concentrations (600 mg dm −3) using 50 kg m −3 and 30 kg m −3 of RHA and GAC dosage, respectively, at 30 ± 1 °C. Adsorption of Py is found to be endothermic in nature and the equilibrium data can be adequately represented by Toth and Redlich–Peterson isotherm equations. Py can be recovered from the spent adsorbents by using acidic water and 0.1 N H 2SO 4. The overall adsorption of Py on RHA and GAC is found to be in the order of GAC > RHA. Comparative assessment of adsorbents used by various investigators available in literature showed the effectiveness of BFA and RHA over other adsorbents. Spent RHA can simply be filtered, dried and used in the boiler furnaces/incinerators. Thus, its heating value can be recovered.

Adsorption of 2-picoline onto bagasse fly ash from aqueous solution

Abstract The adsorption of 2-picoline from aqueous solutions onto bagasse fly ash (BFA), a solid waste collected from the particulate collection equipment attached to the stacks of bagasse fired boilers, is presented in this paper. The influence of various parameters like initial pH (pH 0 ), adsorbent dose ( m ), contact time ( t ), initial concentration ( C 0 ) and temperature ( T ) on the adsorption of 2-picoline from the aqueous solutions were studied using batch adsorption experiments. Equilibrium adsorption and kinetic studies for 2-picoline adsorption onto BFA were also carried out. Various adsorption isotherm equations, viz. Langmuir, Freundlich, Redlich–Peterson and Temkin equilibrium equations were used to test their suitability in describing experimental isotherm data. The adsorption of 2-picoline on bagasse fly ash follows second order kinetics and the equilibrium adsorption increases with increasing initial concentration. The equilibrium sorption isotherm data could be well represented by the Langmuir and Redlich–Peterson isotherm equations. The maximum removal of 2-picoline is found to be 98% at lower concentrations ( −3 ) and 49% at higher concentrations (600 mg dm −3 ) using 5 kg m −3 of BFA dosage at normal temperature and natural pH 0 (∼6.5). Thermodynamic studies revealed that the adsorption of 2-picoline on BFA is endothermic in nature and that the isosteric heat of adsorption decreases with the increase in the equilibrium uptake of 2-picoline on the BFA surface. Desorption of 2-picoline from the loaded BFA using water at different pH, and various other solvents showed that 2-picoline could be recovered by using acidic water and 0.1N H 2 SO 4 . Comparative assessment of BFA and activated carbon showed the superiority of BFA in terms of 2-picoline uptake, the rate of adsorption and the eventual cost of operation.

Lead removal from aqueous solution by natural and pretreated clinoptilolite: Adsorption equilibrium and kinetics

Adsorption of Pb(II) ions from aqueous solution onto clinoptilolite has been investigated to evaluate the effects of contact time, initial concentration and pretreatment of clinoptilolite on the removal of Pb(II). Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Temkin and Dubinin–Radushkevich), four three-parameter (Redlich–Peterson, Sips, Toth and Khan) isotherm models, and kinetic models including the pseudo-first order, the pseudo-second order and Elovich equations using nonlinear regression technique. Of the two-parameter isotherms, Temkin isotherm was the best to describe the experimental data. Three-parameter isotherms have higher regression coefficients (>0.99) and lower relative errors (<5%) than two-parameter isotherms. The best fitting isotherm was the Sips followed by Toth and Redlich–Peterson isotherm equations. Maximum experimental adsorption capacity was found to be 80.933 and 122.400 mg/g for raw and pretreated clinoptilolite, respectively, for the initial concentration of 400 mg/L. Kinetic parameters; rate constants, equilibrium adsorption capacities and related coefficients for each kinetic model were evaluated according to relative errors and correlation coefficients. Results of the kinetic studies show that best fitted kinetic models are obtained to be in the order: the pseudo-first order, the pseudo-second order and Elovich equations. Using the thermodynamic equilibrium coefficients, Gibbs free energy of the Pb(II)–clinoptilolite system was evaluated. The negative value of change in Gibbs free energy (Δ G°) indicates that adsorption of Pb(II) on clinoptilolite is spontaneous.

Removal of methylene blue from aqueous solution by dehydrated wheat bran carbon

Dyes are usually presents in the effluent water of many industries, such as textiles, leather, paper, printing and cosmetics. The effectiveness of dye adsorption from wastewater has made to get alternative different low cost adsorbent to other expensive treatment methods. The adsorption of methylene blue onto dehydrated wheat bran (DWB) was investigated at temperatures (25–45 °C), initial methylene blue (MB) concentrations (100–500 mg L −1) and adsorbent dosage at the given contact time for the removal of dye. The optimum adsorption conditions were found to be as medium pH of 2.5 and at the temperature of 45 °C for the varying adsorbent dosage. Equilibrium isotherms were analysed by Freundlich, Langmuir and Redlich-Peterson isotherm equations using correlation coefficients. Adsorption data were well described by the Langmuir model, although they could be modelled by the Freundlich and Redlich-Peterson model as well. The pseudo-first order and pseudo-second order kinetic models were applied to test the experimental data. It was concluded that the pseudo-second order kinetic model provided better correlation of the experimental data rather than the pseudo-first order model. The mass transfer model as intraparticle diffusion was applied to the experimental data to examine the mechanisms of rate controlling step. It was found that at the higher initial MB concentration, intraparticle diffusion is becoming significant controlling step. The thermodynamic constants of the adsorption process were also evaluated by using the Langmuir constants related to the equilibrium of adsorption at temperatures varied in the range 25–55 °C.

Characteristic features of Bacillus cereus cell surfaces with biosorption of Pb(II) ions by AFM and FT-IR

In order to elucidate the potential mechanisms involved in the biosorption of metal ions, atomic force microscopy (AFM) and Fourier transform infrared (FT-IR) spectroscopy were used to characterize the interaction between Pb 2+ and Bacillus cereus. AFM imaging of the biomass surfaces exposed to different concentrations of lead ions solution showed a major morphological change occurred after Pb 2+ biosorption. The FT-IR spectra indicated the binding characteristics of the lead ions involved the carboxyl, hydroxyl and amino groups in the biomass. Equilibrium biosorption experiments of Pb 2+ were carried out to investigate the effects of pH values and the initial metal concentrations. The experimental isotherm data were then modeled using Langmuir, Freundlich, and Redlich–Peterson isotherm equations. As a result, the Redlich–Peterson model yielded the best fit of experimental data. Kinetics experiments showed the biosorption was a rapid process and the pseudo-second-order model was successfully applied to predict the rate constant of biosorption.

Removal of cationic dyes from aqueous solution using an anionic poly-γ-glutamic acid-based adsorbent

Natural polymeric materials are gaining interest for application as adsorbents in wastewater treatment due to their biodegradable and non-toxic nature. In this study, a biopolymer, poly-γ-glutamic acid (γ-PGA) derived from bacterial sources (Bacillus species) was evaluated for its efficiency in removing basic dyes from aqueous solution. Sorption studies under batch mode were conducted using C.I. Basic blue 9 (BB9) and C.I. Basic green 4 (BG4) as test dyes. Equilibrium process conformed well with the Redlich-Peterson isotherm equation and the monolayer sorption capacity obtained from the Langmuir model was 352.76 and 293.32mg/g for BB9 and BG4 dyes, respectively. The kinetic studies of dye sorption on γ-PGA gave high coefficients of determination (>0.98) for a pseudo second-order equation. An ion-exchange model, which assumes adsorption as a chemical phenomenon, was also found to fit the kinetic data precisely. The dye sorption largely depended on the initial pH of the solution with maximum uptake occurring at pH above 5. About 98% of the dye adsorbed on γ-PGA could be recovered at pH 1, which facilitates the reuse of spent γ-PGA.

Sorption isotherm for safranin onto rice husk: Comparison of linear and non-linear methods

Comparison analysis of linear least-square method and non-linear method for estimating the isotherm parameters was made. Comparison analysis was made using the experimental equilibrium data of safranin onto rice husk at a solution temperature of 305 K. Sorption data were fitted to Freundlich, Langmuir and Redlich–Peterson isotherm equations. All the three isotherm equations showed a better fit to the experimental data. The results show that non-linear method could be a better way to obtain the isotherm parameters. Redlich–Peterson isotherm is a special case of Langmuir isotherm when the Redlich–Peterson isotherm constant g was unity.

Cobalt sorption onto anaerobic granular sludge: Isotherm and spatial localization analysis

This study investigated the effect of different feeding regimes on the cobalt sorption capacity of anaerobic granular sludge from a full-scale bioreactor treating paper mill wastewater. Adsorption experiments were done with non-fed granules in monometal (only Co) and competitive conditions (Co and Ni in equimolar concentrations). In order to modify the extracellular polymeric substances and sulfides content of the granules, the sludge was fed for 30 days with glucose (pH 7, 30 °C, organic loading rate = 1.2 g glucose l −1 day −1) in the presence (COD/SO 4 2− = 1) or absence of sulfate. The partitioning of the sorbed cobalt between the exchangeable, carbonates, organic matter/sulfides and residual fractions was determined using a sequential extraction procedure (modified Tessier). Experimental equilibrium sorption data for cobalt were analysed by the Langmuir, Freundlich and Redlich–Peterson isotherm equations. The total Langmuir maximal sorption capacity of the sludge fed with glucose and sulfate loaded with cobalt alone displayed a significantly higher maximal cobalt sorption ( Q max = 18.76 mg g −1 TSS) than the sludge fed with glucose alone ( Q max = 13.21 mg g −1 TSS), essentially due to an increased sorption capacity of the exchangeable (30–107%) and organic/sulfides fractions (70–30%). Environmental scanning electron microscopy coupled with an energy dispersive X-ray analysis of granular cross-sections showed that mainly iron minerals (i.e. iron sulfides) were involved in the cobalt accumulation. Moreover, the sorbed cobalt was mainly located at the edge of the granules. The sorption characteristics of the exchangeable and carbonates fractions fitted well to the Redlich–Peterson model (intermediate multi-layer sorption behaviour), whereas the sorption characteristics of the organic matter/sulfides and residual fractions fitted well to the Langmuir model (monolayer sorption behaviour). The organic matter/sulfides fraction displayed the highest affinity for cobalt for the three sludge types investigated.

Prediction of optimum sorption isotherm: Comparison of linear and non-linear method

Equilibrium parameters for Bismarck brown onto rice husk were estimated by linear least square and a trial and error non-linear method using Freundlich, Langmuir and Redlich–Peterson isotherms. A comparison between linear and non-linear method of estimating the isotherm parameters was reported. The best fitting isotherm was Langmuir isotherm and Redlich–Peterson isotherm equation. The results show that non-linear method could be a better way to obtain the parameters. Redlich–Peterson isotherm is a special case of Langmuir isotherm when the Redlich–Peterson isotherm constant g was unity.

Comparison of linear and non-linear method in estimating the sorption isotherm parameters for safranin onto activated carbon

Comparison analysis of linear least square method and non-linear method for estimating the isotherm parameters was made using the experimental equilibrium data of safranin onto activated carbon at two different solution temperatures 305 and 313 K. Equilibrium data were fitted to Freundlich, Langmuir and Redlich–Peterson isotherm equations. All the three isotherm equations showed a better fit to the experimental equilibrium data. The results showed that non-linear method could be a better way to obtain the isotherm parameters. Redlich–Peterson isotherm is a special case of Langmuir isotherm when the Redlich–Peterson isotherm constant g was unity.

Competitive Adsorption of Copper-Nickel and Copper-Cadmium Binaries on SMW

In this study, the technical feasibility of using a low-cost sorbent, sheep manure waste (SMW), for the removal of copper, nickel and cadmium ions from aqueous solutions containing Cu2+ --Cd2+ or Cu2+ --Ni2+ binaries is investigated. The scope of the study includes the investigation of the affinity of each metal ion in the presence of the other. Experimental results showed that the SMW has high affinity for the three studied heavy metals, and the affinity of the SMW for these metals is in the order copper > cadmium > nickel. The presence of copper in a solution containing Ni2+ or Cd2+ reduces significantly the percentage removal of both nickel and cadmium. On the other hand, the percentage removal of copper was not affected significantly by the presence of either nickel or cadmium. The equilibrium adsorption data were fit very well with Langmuir, Freundlich, Redlich-Peterson, and Sips isotherm equations. The prediction of the binary adsorption from single metal adsorption data was in fair agreement with the experimental results. The role of ion exchange and carboxyl groups in the adsorption process were also studied.