Pseudo-second Order Rate Model Research Articles

Potentiality of lignin from the Kraft pulping process for removal of trace nickel from wastewater: Effect of demineralisation

An industrial raw Kraft lignin was investigated to ascertain its potential use for removal of trace Ni(II) ion from wastewater by using dilute solutions (0.34–1.7 mM) as models. The effect of demineralisation on its metal sorption ability was examined by employing acid pre-treated samples. Under fixed pre-established equilibrium conditions, the raw lignin exhibited a lower effectiveness than the demineralised one, with the latter attaining an almost complete removal of Ni(II) ions. For both lignins, sorption kinetics was properly described by a pseudo-second order rate model. Equilibrium isotherms were also determined and adequately represented by conventional two-parameter models. The higher nickel sorption capacity for the demineralised lignin compared to the raw sample was consistent with enhancements in the negative magnitude of zeta potential, sodium sorption capacity, and content of phenolic hydroxyl groups occasioned by the acid pre-treatment. Accordingly, demineralisation appears as a readily convenient strategy to improve the behaviour of industrial Kraft lignin for potential use as a biosorbent of trace nickel from polluted water.

Removal of total phenols from olive-mill wastewater using an agricultural by-product, olive pomace

The purpose of this study was to investigate the sorption of total phenols, which are contained in olive-mill wastewater (OMWW), on solid by-products of olive pomace processing mills. Preliminary batch experiments were conducted using three different types of olive pomace, dried olive pomace (OP-1), dried and solvent extracted olive pomace (OP-2) and dried, solvent extracted and incompletely combusted olive pomace (OP-3). According to the results, OP-3 showed high performance for total phenols sorption and stability. For sorbent concentration of 10 g L −1 and sorbate concentration of 50 mg L −1, more than 40% of initial total phenols concentration was removed. Sorption kinetics was well described by the pseudo-second order rate model ( R 2 > 0.99). Total phenols removal efficiency was improved by increasing sorbent concentration and solution's pH or decreasing particle size of the sorbent material. The Langmuir and Freundlich isotherms sufficiently described OP-3 sorption capacity for the concentration range studied (50–500 mg L −1). Fixed bed sorption experiments showed that lower flow rates and smaller particle size of sorbent resulted in longer column exhaustion time and higher initial removal efficiency. Experiments with thermally or chemically regenerated OP-3 showed that sorption capacity deteriorated after regeneration.

Fluoride removal from aqueous solution by Ca-pretreated macrophyte biomass

Environmental context. Fluoride concentrations in drinking water above 1.5 mg L–1 may be detrimental to human health. Many methods have been developed for removing excessive fluoride from drinking water. The use of an aquatic macrophyte biomass (Eleocharis acicularis) pretreated with Ca2+, a low-cost natural material, could be a technique for rural populations in developing countries that cannot afford treated or bottled water for daily consumption. Abstract. The use of an aquatic macrophyte biomass (Eleocharis acicularis) pretreated with Ca2+ as a low-cost natural material for the removal of fluoride from aqueous solution was studied. Batch experiments were carried out to determine fluoride sorption capacity and the efficiency of the sorption process under different pH, initial F– and macrophyte biomass doses. The experimental data showed good fitting to Langmuir and Freundlich isotherm models. The maximum F adsorption capacity was 0.110 mmol g–1 with an efficiency of 64.5% (pH 6.0; 5.0 g L–1 Ca-pretreated biomass). The binding of Ca2+ to the biomass increased the removal efficiency over 100%. The F– removal kinetics were rapid, less than 30 min, and best described by the pseudo-second order rate model. The rate constant, the initial sorption rate and the equilibrium sorption capacity were determined. These results may be useful for deprived rural population water supply schemes in Mexico and in other developing countries.

Removal of acid dyes from aqueous solutions using orange peel as a sorbent material

An agricultural by-product waste, orange peel, was tested for the removal of four acid dyes from aqueous solutions in batch conditions. As results obtained, kinetics of dyes sorption was time of contact, initial dyes concentration and dyes type dependent. The pseudo second-order reaction rate model adequately described the kinetics of dyes sorption with high correlation coefficients. A. Langmuir model gave a good fit to the experimental data. A high dyes sorption was observed by this sorbent material. For Nylosane Blue, a maximum sorption capacity about 65.88 mg/g was obtained followed by Erionyl Yellow (64.14 mg/g), Nylomine Red (62.07 mg/g) and Erionyl Red (40.72 mg/g) respectively.

Adsorption of copper(II) from aqueous solution by Beidellite

Beidellite was used as an adsorbent for the removal of copper ions from aqueous solutions. Batch mode studies were carried out by varying initial copper (II) concentrations (50–500 mg/l), initial pH (2.0–5.0), adsorbent particle size (0.095–0.890 mm) and temperature (293–333 K). A contact time of 60 min was required to reach equilibrium. Adsorption of the metal ion was highly pH dependent and the optimum pH for the removal was 5.0 at which the removal was maximum (25.3 mg/g). The result showed that the amount adsorbed of the metal ion increased with increasing initial copper (II) concentration and contact time. Three adsorption kinetic models, the pseudo first-order, second-order and intraparticle diffusion were applied to experimental data to predict the adsorption rate constants. A comparison of kinetic models on the overall adsorption rate showed that metal ion/adsorbent system was best described by the pseudo second-order rate model. The adsorption capacity (Qo) calculated from the Langmuir isotherm was 71.07 mg/g for at pH 5.0, 293 K for the particle size of 0.095–0.890 mm. The experimental data yielded excellent fits with Langmuir isotherm equation. Different thermodynamic parameters viz., changes in standard free energy, enthalpy and entropy were evaluated and it was found that the reaction was spontaneous and endothermic in nature.

Biosorption of nickel(II) ions by baker’s yeast: Kinetic, thermodynamic and desorption studies

In this study, the biosorption of nickel(II) ion on deactivated protonated yeast was investigated as a function of temperature at different initial metal ion concentrations. The effect of temperature on the sorption was more significant at lower nickel(II) ion concentrations compared to higher concentrations. The protonated yeast biomass exhibited the highest nickel(II) ion uptake capacity at 27 °C at an initial nickel(II) ion concentration of 400 mg/l and an initial pH of 6.75. The biosorption capacity decreased from 9.8 to 9.3 mg/g at an initial nickel(II) ion concentration of 400 mg/l, while at a lower initial concentration of 100 mg/l, it decreased from 8.2 to 4.9 mg/g, as the temperature was increased from 27 °C to 60 °C. The equilibrium data fit better to the Freundlich and Redlich–Peterson isotherm models compared to the Langmuir model in the concentration range studied (10–400 mg/l). Kinetic models applied to the sorption data at different temperatures showed that nickel(II) ion uptake process followed the pseudo-second order rate model and the adsorption rate constants decreased with increasing temperature. The activation energy of biosorption ( E a) was determined to be −13.3 kJ/mol using the pseudo-second order rate constants. The results indicated that the biosorption of nickel(II) ion on to baker’s yeast was spontaneous and exothermic in nature. Desorption studies revealed that the protonated yeast biomass can be regenerated using 0.1N HCl and reused.

Copper removal from wastewater using spent-grain as biosorbent

The removal of Cu(II) ions from aqueous solutions using spent-grain was studied. The experimental data fitted the Langmuir isotherm and the maximum adsorption capacity of spent-grain was determined to be 10.47 mg g −1 dry weight (pH 4.2). Kinetic studies showed the adsorption process followed pseudo second-order rate model. Column studies with synthetic Cu(II) solutions were used to investigate the effects of Cu(II) ion concentration, initial pH, flow rate and the presence of EDTA on the Cu(II) removal performance. When treating the spent-lees, the wastewater from the whisky distilling industry, the reduction of Cu(II) uptake capacity to 77.7% (solution pH adjusted to 4.5 with 1 N NaOH) and 31.6% (pH 3.8 without adjustment) was observed compared to Cu(II) uptake capacity when treating synthetic Cu(II) solution. On the basis of the results and that spent-grain is an abundant and by-product from the whisky distilling industry we suggest that it can be economically and effectively applied as a biosorbent for the removal of Cu(II) ions from distilling wastewaters.

Modelling the kinetics and equilibrium properties of cadmium biosorption by river green alga and water hyacinth weed

Cadmium biosorption properties of non-living, dried river green alga from a river source, and water hyacinth weed, Eichhornia crassipes from a lake in Zimbabwe have been investigated. The cadmium uptake was found to depend on initial pH, uptake being apparently minimal at low pH values and increasing with an increase in pH. Cadmium biosorption kinetics by both samples is fast, with 80% of total uptake occurring within 60 min. The effect of initial solution pH and initial cadmium concentration on cadmium biosorption from a cadmium solution has been studied. The data for algal biomass fitted the Langmuir monolayer adsorption isotherm, while the biosorption of the metal by water hyacinth weed fitted the Freundlich adsorption isotherm with 1/n values all less than 1. Maximum metal uptake capacities were recorded using 0.35 g of biomass and a 250 mg L−1 cadmium solution at pH 6.5 and at 25°C and these were about 85 and 50 mg L−1 for water hyacinth weed and green alga, respectively, showing that water hyacinth weed offered a greater potential for cadmium uptake. The absorption was described by pseudo-second order rate model and the rate constant and equilibrium sorption capacity are reported.

Removal of toxic chromium from wastewater using green alga Ulva lactuca and its activated carbon

Biosorption of heavy metals can be an effective process for the removal of toxic chromium ions from wastewater. In this study, the batch removal of toxic hexavalent chromium ions from aqueous solution, saline water and wastewater using marine dried green alga Ulva lactuca was investigated. Activated carbon prepared from U. lactuca by acid decomposition was also used for the removal of chromium from aqueous solution, saline water and wastewater. The chromium uptake was dependent on the initial pH and the initial chromium concentration, with pH ∼1.0, being the optimum pH value. Langmuir, Freundlich, Redlich-Peterson and Koble-Corrigan isotherm models were fitted well the equilibrium data for both sorbents. The maximum efficiencies of chromium removal were 92 and 98% for U. lactuca and its activated carbon, respectively. The maximum adsorption capacity was found to be 10.61 and 112.36 mg g −1 for dried green alga and activated carbon developed from it, respectively. The adsorption capacities of U. lactuca and its activated carbon were independent on the type of solution containing toxic chromium and the efficiency of removal was not affected by the replacing of aqueous solution by saline water or wastewater containing the same chromium concentration. Two hours were necessary to reach the sorption equilibrium. The chromium uptake by U. lactuca and its activated carbon form were best described by pseudo second-order rate model. This study verifies the possibility of using inactivated marine green alga U. lactuca and its activated carbon as valuable material for the removal of chromium from aqueous solutions, saline water or wastewater.

Removal of Astrazon Yellow 7GL from aqueous solutions by adsorption onto wheat bran

Adsorption kinetic and equilibrium of a basic dye (Astrazon Yellow 7GL) from aqueous solutions at various initial dye concentration (50–300 mg/l), pH (4–10), adsorbent dosage (2–8 g/l), particle size (354–846 μm) and temperature (30–50 °C) on wheat bran were studied in a batch mode operation. The result showed that the amount adsorbed of the dye increased with increasing initial dye concentration and contact time, whereas particle size and pH had no significant affect on the amount of dye adsorbed by the adsorbent. A comparison of kinetic models on the overall adsorption rate showed that dye/adsorbent system was best described by the pseudo second-order rate model. The removal rate was also dependent on both external mass transfer and intra-particle diffusion. The low value of the intraparticle diffusivity, 10 −11 cm 2/s, indicated the significant influence of intraparticle diffusion on the kinetic control. The adsorption capacity ( Q 0) calculated from the Langmuir isotherm was 69.06 mg/g for at pH 5.6, 303 K for the particle size of 354 μm. The experimental data yielded excellent fits with Langmuir and Tempkin isotherm equations. Different thermodynamic parameters showed that the reaction was spontaneous and endothermic in nature.

Physico-chemical method for ammonia removal from synthetic wastewater using limestone and GAC in batch and column studies

The purpose of the present study was to examine the removal of ammoniacal nitrogen (NH 4-N) from synthetic wastewater using limestone (LS) and granular activated carbon (GAC) mixture as low cost adsorbent. In batch study, optimum shaking and settling times were 150 and 120 min, respectively. The LS–GAC mixture ratio of 25:15 removed about 58% NH 4-N. The smaller particle size of medium yielded higher adsorption capacity. The equilibrium adsorption data followed the Freundlich isotherm ( R 2 > 0.98) but it showed weak bond. Adsorption kinetics were well described by the pseudo second-order rate model ( R 2 > 0.93). The upflow column showed that higher flow rate and initial concentration resulted in shorter column saturation time. The study showed that the usage of GAC could be reduced by combining GAC with LS for the removal of NH 4-N from wastewater; thus reducing the cost of treatment.

A comparison of low-cost biosorbents and commercial sorbents for the removal of copper from aqueous media

Three biosorbents, crab carapace, the macroalgae Fucus vesiculosus and peat were compared with two commercial materials, an activated-carbon and an ion-exchange resin for the removal of copper from aqueous media. Kinetic models of Lagergren first-order, pseudo-second order and intraparticular diffusion were used to model the data. The process for all materials is best represented by the pseudo-second order rate model. Langmuir and Freundlich isotherms were used to describe the sorption equilibrium data. Maximum uptake values were 79.4, 114.9 and 71.4mgg−1 for crab carapace, F. vesiculosus and ion-exchange resin, respectively. Langmuir and Freundlich isotherm models could not be fitted to the experimental data for peat and activated-carbon. Ion-exchange was calculated to contribute ∼75%, 77% and 44% to the total biosorption by crab carapace, F. vesiculosus and peat, respectively. The removal efficiencies of crab carapace and F. vesiculosus were >95% and comparable with those achieved using ion-exchange resin. Results from this study suggest that both crab carapace and F. vesiculosus are efficient and effective biosorbent materials for the removal of copper from aqueous solutions and given that they are also low-cost, may be considered viable alternatives to activated-carbon and ion-exchange resin.

Screening of new sorbent materials for cadmium removal from aqueous solutions

This study compares the abilities of four low-cost materials: peels of peas, broad bean, and medlar, respectively and fig leaves, to remove cadmium from aqueous solutions. Kinetic data and equilibrium sorption isotherms were measured in batch conditions. Kinetics of cadmium sorption was contact time, initial cadmium concentration and sorbent type dependent. The results also showed that the kinetics of cadmium sorption were described by a pseudo second-order rate model. The cadmium uptake of these low-cost materials was quantitatively evaluated using sorption isotherms. Results indicated that Langmuir model gave an acceptable fit to the experimental data. A high cadmium sorption was observed by these materials. The broad bean peel was the most effective to remove cadmium ions with a maximum sorption capacity about 147.71 mg/g followed by peas peel (118.91 mg/g), fig leaves (103.09 mg/g), and medlar peel (98.14 mg/g).

Copper removal from aqueous solution by marine green alga Ulva reticulata

The batch removal of copper (II) ions from aqueous solution under different experimental conditions using Ulva reticulata was investigated in this study. The copper (II) uptake was dependent on initial pH and initial copper concentration, with pH 5.5 being the optimum value. The equilibrium data were fitted using Langmuir and Freundlich isotherm model, with the maximum copper (II) uptake of 74.63 mg/g determined at a pH of 5.5. The Freundlich model regression resulted in high correlation coefficients and the model parameters were largely dependent on initial solution pH. At various initial copper (II) concentrations (250 to 1000 mg/L), sorption equilibrium was attained between 30 and 120 min. The copper (II) uptake by U. reticulata was best described by Pseudo-second order rate model and the rate constant, the initial sorption rate and the equilibrium sorption capacity were also reported. The elution efficiency for copper-desorption from U. reticulata was determined for 0.1 M HCl, H 2 SO 4 , HNO 3 and CaCl 2 at various Solid-to-Liquid ratios (S/L). The solution CaCl 2 (0.1 M) in HCl at pH 3 was chosen to be the most suitable copper-desorbing agent. The biomass was also employed in three sorption-desorption cycles with 0.1 M CaCl 2 (in HCl, pH 3) as the elutant.

Copper removal from aqueous solution by marine green alga Ulva reticulata

The batch removal of copper (II) ions from aqueous solution under different experimental conditions using Ulva reticulata was investigated in this study. The copper (II) uptake was dependent on initial pH and initial copper concentration, with pH 5.5 being the optimum value. The equilibrium data were fitted using Langmuir and Freundlich isotherm model, with the maximum copper (II) uptake of 74.63 mg/g determined at a pH of 5.5. The Freundlich model regression resulted in high correlation coefficients and the model parameters were largely dependent on initial solution pH. At various initial copper (II) concentrations (250 to 1000 mg/L), sorption equilibrium was attained between 30 and 120 min. The copper (II) uptake by U. reticulata was best described by Pseudo-second order rate model and the rate constant, the initial sorption rate and the equilibrium sorption capacity were also reported. The elution efficiency for copper-desorption from U. reticulata was determined for 0.1 M HCl, H 2 SO 4 , HNO 3 and CaCl 2 at various Solid-to-Liquid ratios (S/L). The solution CaCl 2 (0.1 M) in HCl at pH 3 was chosen to be the most suitable copper-desorbing agent. The biomass was also employed in three sorption-desorption cycles with 0.1 M CaCl 2 (in HCl, pH 3) as the elutant.

Sorption of Ni(II)-citrate complex from electroless nickel plating solutions onto chitosan

SUMMARYSpent electroless nickel plating solutions contain Ni(II)-citrate complexes which are hazardous to the environment. These complexes can be removed by using chitosan as a sorbent. Kinetic investigations indicate that Ni(II) sorption from complex solutions onto chitosan can be described by a pseudo-second order rate model. The experimental data of the adsorption under equilibrium conditions for both Ni(II) and citrate correlate well with the Freundlich isotherm equation. During the sorption of Ni(II)-citrate complex on chitosan competition between Ni(II) and citrate ions takes place. The citrate sorption prevails.Adipate, the additive used in electroless nickel plating solutions, is not sorbed by chitosan, but its presence in solutions has an increasing effect on citrate sorption from citrate solutions without Ni(II) and the increasing effect on Ni(II) sorption from Ni(II)-citrate complex solutions. The other components of electroless nickel plating solution, i.e. hypophosphite, sulphate, phosphite have no influence on sorption.

Collagen fiber immobilized Myrica rubra tannin and its adsorption to UO2(2+).

Tannins, which are rich in ortho-hydroxyl groups, have a high affinity for UO2(2+). In this paper, Myrica rubra tannin was immobilized on collagen fiber by an aldehydic cross-linking reaction to prepare a novel adsorbent for uranium (UO2(2+)) recovery from wastewater. The adsorption equilibrium, the adsorption kinetics, and the effects of temperature and pH on the adsorption equilibrium were investigated in detail. It was found that the Myrica rubra tannin immobilized on collagen fiber exhibits an excellent adsorption capacity for UO2(2+). The adsorption capacity at 293 K and pH 5.0 was as high as 1.19 mmol UO2(2+)/g (283.3 mgU/g) when the initial concentration of UO2(2+) in solution was 7.5 mmol/L. The adsorption isotherms could be described by the Freundlich equation, and the increase of temperature promoted the adsorption to UO2(2+) . The adsorption kinetics data were fitted very well by the pseudosecond-order rate model, and the equilibrium adsorption capacity calculated by the pseudo-second-order rate model was almost the same as that determined by the actual measurement with the error < or = 4%. The pH has a significant effect on the adsorption process. According to our experiments, the suitable pH scope should be 5-8.