Radke Prausnitz Research Articles

Experimental and modeling studies of methylene blue adsorption onto particles of peanut shell

ABSTRACTIn this study, adsorption of methylene blue from aqueous solution onto peanut shell has been investigated. Experimental data obtained from dye adsorption have been studied by five two-parameter (Langmuir, Freundlich, Dubinin–Radushkevich, Temkin, and Frumkin) and five three-parameter (Redlich–Peterson, Sips, Toth, Radke–Prausnitz, and Koble–Corrigan) isotherm models. Eight nonlinear error functions (sum squares errors, hybrid fractional error function, Marquardt’s percent standard deviation, average relative error, sum of absolute error, the coefficient of determination, nonlinear chi-square test, and standard deviation of relative errors) were examined for isotherm equations. In order to explain the adsorption kinetics fit of pseudo-first-order, pseudo-second-order, Elovich, and intraparticle kinetic models were used. The best fitting isotherm model was the Radke–Prausnitz and kinetics model was pseudo-second-order. Adsorption experiment showed that the maximum capacity of agricultural waste for methylene blue was 67.57 L · g−1 at 25°C.

Adsorption of acid dyes from aqueous solution by CTMAB modified bentonite: Kinetic and isotherm modeling

Adsorption of four acid dyes onto cetyltrimethyl ammonium bromide (CTMAB) modified organobentonite from aqueous solution was studied, and effects of the parameters like adsorbent dosage, solution pH, contact time and dye concentration were investigated. The adsorption onto CTMAB-Bent attained equilibrium quickly within 10min for Acid Blue 93 (AB93), Acid Turquoise Blue A (ATBA), Acid Golden Yellow G (AGYG) and 50min for Acid Blue 25 (AB25). The adsorption capacity decreased slightly along with the increasing solution pH of 7.0. Four adsorption kinetics equations (pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich) were employed to evaluate experimental kinetics data. The rates of the acid dyes adsorption conformed to the pseudo-second-order equation well. The adsorption equilibrium data were analyzed with six models. Both linear and nonlinear regression methods were implemented to calculate isotherm parameters, and the nonlinear regression was more favorable. Regarding to the results of nonlinear analysis, the most applicable adsorption isotherm models were found to be Freundlich, Langmuir, Radke–Prausnitz, Fritz–Schlunder, and Sips equations. The removal ratios of the acid dyes by CTMAB-Bent were all above 88% at the experimental conditions, suggesting that CTMAB-Bent was an excellent adsorbent for acid dyes removal from aqueous solution.

Sorptive removal of salicylic acid and ibuprofen from aqueous solutions using pine wood fast pyrolysis biochar

Pine wood biochar, prepared at 698K with a residence time of 20–30s in an auger-fed reactor, was used as a 3-dimensional adsorbent to remove salicylic acid and ibuprofen from aqueous solutions. This biochar was characterized by FT-IR spectroscopy, scanning electron microscopy, transmission electron microscopy, surface area determination, and zero point charge measurements. Batch sorption studies were carried out at pH values from 2 to 10, adsorbate concentrations from 25 to 100mg/L and temperatures from 298 to 318K. The adsorption of both adsorbates was highest at low pH values, dropped as pH increased and then exhibited a second increase related to the pKa of these carboxylic acid adsorbates. This was followed by a further drop at high pH. Conjugate acid/base equilibria of the adsorbates and the phenolic hydroxyl and carboxylic acid biochar sites versus pH dominated the mechanism. Sorption followed pseudo-second order kinetics. Sorption was evaluated from 298 to 318K using the Freundlich, Langmuir, Redlich–Peterson, Toth, Sips, and Radke–Prausnitz adsorption isotherm models. Langmuir adsorption capacities for both salicylic acid and ibuprofen were 22.70 and 10.74mg/g, respectively. This low surface area pinewood biochar (1.35m2/g) can adsorb far more adsorbate compared to commercial activated carbons per unit of measured surface area. Methanol stripping achieved 93% and 88% desorption of salicylic acid and ibuprofen, respectively, from the spent biochar, and 76% and 72% of the initial salicylic acid and ibuprofen adsorption capacity, respectively, remained after four full capacity equilibrium recycles.

Modified durian seed as adsorbent for the removal of methyl red dye from aqueous solutions

Mesoporous-activated carbon from durian seed (DSAC) was prepared; it was used as adsorbent for the removal of methyl red (MR) dye from aqueous solution. Textural and adsorptive characteristics of activated carbon prepared from raw durian seed (DS), char durian seed (char DS) and activated durian seed (DSAC) were studied using scanning electron microscopy, Fourier transform infra red spectroscopy, proximate analysis and adsorption of nitrogen techniques, respectively. Acidic condition favors the adsorption of MR dye molecule by electrostatic attraction. The maximum dye removal was 92.52 % at pH 6. Experimental data were analyzed by eight model equations: Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, Radke–Prausnitz, Sips, Vieth–Sladek and Brouers–Sotolongo isotherms and it was found that the Freundlich isotherm model fitted the adsorption data most. Adsorption rate constants were determined using pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion and Avrami kinetic model equations. The results clearly showed that the adsorption of MR dye onto DSAC followed pseudo-second-order kinetic model. Both intraparticle and film diffusion were involved in the adsorption process. The mean energy of adsorption calculated from D–R isotherm confirmed the involvement of physical adsorption. Thermodynamic parameters were obtained and it was found that the adsorption of MR dye onto DSAC was an endothermic and spontaneous process at the temperatures under investigation.

Adsorptive Removal of Malachite Green Dye Using Durian Seed-Based Activated Carbon

Chemically prepared activated carbon derived from durian seed (DSAC) was used as adsorbent to adsorb Malachite green (MG) dye. The prepared DSAC was characterized using Brunauer–Emmet–Teller (BET), Fourier transform infrared (FTIR), scanning electron microscope (SEM), and proximate analysis, respectively. Batch adsorption studies were carried out for the removal of MG dye from aqueous solutions by varying operational parameters like contact time, initial MG dye concentration, solution temperature, and initial solution pH. Maximum dye removal of 97 % was obtained at pH 8. Experimental data were analyzed by eight model equations—Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, Radke–Prausnitz, Sips, Vieth–Sladek, and Brouers–Sotolongo isotherms—and it was found that the Freundlich isotherm model fitted the adsorption data the most. Adsorption rate constants were determined using pseudo-first-order and pseudo-second-order rate equations, Elovich, intraparticle diffusion, and Avrami kinetic model. The results clearly showed that the adsorption of MG dye onto DSAC followed the pseudo-second-order model, and the mechanism of adsorption was controlled both by film diffusion and intraparticle diffusion. Thermodynamic parameters such as ∆G, ∆H, and ∆S were also calculated for the adsorption process. The process was found to be spontaneous and endothermic in nature. This work provided an attractive adsorbent for the removal of MG dye from wastewaters.

Synthesis and characterization of resorcinol formaldehyde carbon cryogel as efficient sorbent for imidacloprid removal

AbstractCarbon cryogel (CC) has been prepared through sol gel polycondensation of resorcinol with formaldehyde in basic aqueous solution followed by freeze-drying and carbonization. Porous properties of CC analyzed by gravimetric McBain method confirmed the expected surface area and degree of mesoporosity. Obtained powdered material was used for the removal of pesticide imidacloprid from aqueous solutions under regular batch adsorption procedure. A set of several isotherm models including Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, Brouers–Sotolongo, Redlich–Peterson, Sips, Toth, Jovanovic, Hurkins–Jura, Halsey and Radke–Prausnitz model was used for nonlinear fitting of equilibrium data. Several models fitted with quite high correlation coefficients. Bangham and Elovich model fitted suitably for kinetic study indicating that pesticide diffusion into carbons pores is important step which dictates the process rate. Suitability of kinetic models decreased with the increase in adsorbent dosage. Imidac...

Adsorption of basic red 9 onto activated carbon derived from immature cotton seeds: isotherm studies and error analysis

The activated carbon produced from immature cotton seeds via sulphuric acid activation was utilized for adsorption of the basic red 9 from the aqueous solution. Adsorbent possessed a larger surface area (495.96 m2/g), methylene blue number (42) and iodine number (510). The process parameters of the sorption system, such as pH of the solution (2–12), temperature (20–40°C) agitation time (1–5 h) and initial BR9 concentration (50–250 mg/l), were studied to understand their effects on BR9 removal. The optimized parameters are found to be pH: 12, temperature: 40°C, agitation time: 3 h and initial concentration: 150 mg/l. The experimental equilibrium data were analysed using a single-parameter model (Henry’s law), six two-parameter models (Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, Smith, and Javanovic), eleven three-parameter models (Redlich–Peterson, Sips, Toth, Hill, Khan, Brunauer–Emmett–Teller (BET), Fritz–Schluender-III, Vieth–Sladek, Radke–Prausnitz, Brouers–Sotolongo, and Unilin), five four-parameter models (Baudu, Parker, Marczewski–Jaroniec, Fritz–Schlunder-IV and Weber–van Vliet) and a five-parameter model (Fritz–Schlunder-V). Non-linear regression analysis was employed to identify the best-fit isotherm based on the error functions: sum of the square error, derivative of hybrid fractional error function, derivative of Marquardt’s percentage standard deviation, average relative error, the sum of absolute errors and statistical comparison values: coefficient of determination (R2), root-mean-square error (RMSE) and non-linear chi-square test (χ2). Among the all adsorption isotherms considered, Fritz–Schlunder-V was found to be a perfect representation of the experimental equilibrium data (R2: 0.9998081, RMSE: 0.1018119, χ2: 0.0023423). The goodness of the models to explain the equilibrium data was in the order: Fritz–Schlunder-V ##xgt; Fritz–Schlunder-IV ##xgt; Brouers–Sotolongo ##xgt; Unilin ##xgt; Marczewski–Jaroniec ##xgt; Baudu ##xgt; Sips ##xgt; Hill ##xgt; Vieth–Sladek Fritz–Schluender-III ##xgt; Redlich–Peterson ##xgt; Khan ##xgt; Radke–Prausnitz ##xgt; BET ##xgt; Weber–van Vliet ##xgt; Langmuir ##xgt; Parker ##xgt; Jovanovic ##xgt; Freundlich.

Use of papaya seeds as a biosorbent of methylene blue from aqueous solution

In this study papaya seeds were used to remove methylene blue dye from aqueous solution. Papaya seeds were characterized as possessing a macro/mesoporous texture and large pore size. Studies were carried out in batches to evaluate the effect of contact time and pH (2-12) on the removal of dye. It was observed that the adsorption of dye was better in the basic region (pH 12). The equilibrium data were analyzed using Langmuir, Freundlich, Dubinin-Raduschkevich, Tempkin, Jovanovich, Redlich-Peterson, Sips, Toth and Radke-Prausnitz isotherms. The equilibrium data were best described by the Langmuir isotherm with a maximum adsorption capacity of 637.29 mg g(-1). Adsorption kinetic data were fitted using the pseudo-first-order and pseudo-second-order model. The adsorption kinetic is very fast and was best described by the pseudo-second-order model.

Investigation of Kinetics and Isotherm Models for the Acid Orange 95 Adsorption from Aqueous Solution onto Natural Minerals

Adsorption of Acid Orange 95 (AO 95) from aqueous solution onto natural bentonite, zeolite, and sepiolite was studied, and the effects of the parameters like pH, contact time, temperature, and concentration of dye were investigated. The AO 95 adsorption onto bentonite, sepiolite, and zeolite was favorable at pH 1.5. It was found that temperature does not affect the adsorbed amount of dye significantly. Among the adsorbents, the highest adsorption capacity is that of bentonite. The pseudo-first-order and pseudo-second-order models were employed to analyze the experimental kinetic data. The adsorption experimental equilibrium data were analyzed with two- (Langmuir, Freundlich, Dubinin–Radushkevich, Harkins–Jura, Temkin, and Jovanovic) and with three- or four-parameter models (Redlich–Peterson, Radke–Prausnitz, Toth, Sips, and Fritz–Schlünder). Both linear and nonlinear regression methods were applied to calculate the kinetic and isotherm parameters, and the nonlinear regression was found as a more suitable method. Regarding to the results of the nonlinear analysis, the rates of adsorption conformed to the pseudo-first-order kinetics, and the most suitable adsorption models were found to be the Toth, Harkins–Jura, and Freundlich isotherms for sepiolite, bentonite, and zeolite, respectively.

Strengthening adsorption characteristics of non-steroidal anti-inflammatory drug onto microwave-assisted mesoporous material: Process design, mechanism and characterization

Ibuprofen (iBu) is one of the most prescribed and consumable global non-steroidal anti-inflammatory drugs (NSAIDs). Consequently it has been ranked as one of the most noticed pharmaceuticals in the environment, having distressing concentrations up to microgram per litre in water. A gas chromatography–mass spectrometry method was performed to analyze acidic pharmaceutical iBu quantification and were enriched with liquid–liquid extraction followed by derivatisation with N, O-bis(trimethylsilyl) trifluoroacetamide. The fundamental perspective of ibuprofen adsorption was evaluated by isotherm, thermodynamic and kinetic details. Equilibrium profile was discussed by two-parameter and three-parameter isotherm models. The best fitting model was chosen according to the statistical criteria. The experimental results substantiated the correctness of the Radke–Prausnitz model and reinforced the conclusion of correlated thermodynamic parameters for iBu binding. Adsorption of iBu was increased with an increase in temperature. Reaction pathways to attain equilibrium were in good correlation with pseudo second order rate kinetics. The excellent mesoporosity and high surface area of microwave-assisted developed adsorbent was one of the key contributors for iBu uptake apart from coulombic attraction between adsorbate–adsorbent system at acidic pH value. Adsorption mechanism was plausibly explained by spectroscopic techniques.

Adsorption of methylene blue on activated carbon produced from flamboyant pods ( Delonix regia): Study of adsorption isotherms and kinetic models

The adsorption of methylene blue (MB) onto activated carbon produced from flamboyant pods ( Delonix regia) and obtained under optimized conditions (AC op) was carried out in this work. The experimental equilibrium data were analyzed using the isotherms of Langmuir, Freundlich, Jovanovic, Harkins–Jura, Tempkin, Redlich–Peterson, Toth, Radke–Prausnitz, Sips, Vieth–Sladek, and Brouers–Sotolongo. The adsorption kinetics of pseudo-first order, pseudo-second order, and Avrami were used for the kinetic studies. For the Toth isotherm, the value of maximum adsorption capacity ( Q m = 889.58 mg g −1) was close to the experimental value ( Q m = 890 mg g −1), and the correlation coefficient ( R 2) was 0.9836. The experimental data fitted very well to Avrami kinetic model. The Fourier-transform infrared spectroscopy spectra and the scanning electron microscopy images showed the presence of MB adsorbed onto AC op. Several possible mechanisms of interaction that can occur in the MB–AC op system are discussed. AC op is a fast and effective adsorbent for removing MB from aqueous solutions.

Application of cupuassu shell as biosorbent for the removal of textile dyes from aqueous solution

The cupuassu shell (Theobroma grandiflorum) which is a food residue was used in its natural form as biosorbent for the removal of C.I. Reactive Red 194 and C.I. Direct Blue 53 dyes from aqueous solutions. This biosorbent was characterized by infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption/desorption curves. The effects of pH, biosorbent dosage and shaking time on biosorption capacities were studied. In acidic pH region (pH 2.0) the biosorption of the dyes were favorable. The contact time required to obtain the equilibrium was 8 and 18 h at 298 K, for Reactive Red 194 and Direct Blue 53, respectively. The Avrami fractionary-order kinetic model provided the best fit to experimental data compared with pseudo-first-order, pseudo-second-order and chemisorption kinetic adsorption models. The equilibrium data were fitted to Langmuir, Freundlich, Sips and Radke–Prausnitz isotherm models. For both dyes the equilibrium data were best fitted to the Sips isotherm model.

Continuous fixed bed adsorption of C.I. Acid Blue 92 by exfoliated graphite: An experimental and modeling study

Removal of C.I. Acid Blue 92(AB92) dye by exfoliated graphite (EG) was investigated. Batch adsorption test results proved that EG can remove the dye with a minimum removal efficiency of 70%. Equilibrium isotherm was analyzed by Freundlich, Langmuir, and Radke–Prausnitz models and the related parameters were estimated. It was found that both Langmuir and Radke–Prausnitz models fit the experimental data satisfactorily. A comprehensive series of column tests were performed to determine the breakthrough curves, and the effects of the feed flow rate, initial dye concentration, and adsorbent dosage on adsorption process were studied. The results showed that the breakthrough time increased in proportion to the increase in the dose of adsorbent, but decreased with increase in flow rate and initial dye concentration. The total uptake of AB92 was found 5.02 (gdye/gEG) at 27±2°C for the initial concentration of 30mg L−1 at 9.6mL min−1 feed flow rate. An axial dispersion mathematical model implementing nonlinear isotherm and linear driving force mass transfer assumption were developed for predicting the dynamic behavior of the adsorption column. The results obtained from the mathematical model were in good agreement with the experimental data, which proved the success of the model in predicting the process.

Activated carbon obtained by pyrolysis of potato peel for the removal of heavy metal copper (II) from aqueous solutions

Activated carbons (ACs) were prepared by pyrolysis of potato peel in presence of zinc chloride (chemical activities). Potato peel from Colombian cultives were impregnated with aqueous solutions of ZnCl 2 following a variant of the incipient wetness method. Different concentrations were used to produce impregnation ratios of 40, 70, 110 and 160 wt.%. Activation was carried out under argon flow by heating to 823 K with 4 h soaking time. The porous texture of the obtained ACs was characterized by physical adsorptions of N 2 at 77 K and CO 2 at 273 K. The impregnation ratio had a strong influence on the pore structure of these ACs, which could be easily controlled by simply varying the proportion of ZnCl 2 used in the activation. Thus, low impregnation ratio led to essentially microporous ACs. At intermediate impregnation ratios, ACs with wider pore size distribution (from micropores to mesopores) were obtained. Finally, high impregnation ratios yielded essentially mesoporous carbons with high surface area and pore volume. The four best-fit three-parameter isotherms Sips, Toth, Radke–Prausnitz and Vieth–Sladek suggest that the sorption capacity of activated carbon of potato peel to uptake copper ions to be 74 mg/g.

Adsorption of copper from aqueous solution by activated carbons obtained by pyrolysis of cassava peel

Activated carbons (ACs) were prepared by pyrolysis of cassava peel in presence of chloride zinc (chemical activities). Cassava peel from Colombian cassava cultives were impregnated with aqueous solutions of ZnCl 2 following a variant of the incipient wetness method. Different concentrations were used to produce impregnation ratios of 40, 70, 110 and 160 wt.%. Activation was carried out under argon flow by heating to 823 K with 1 h soaking time. The porous texture of the obtained ACs was characterized by physical adsorptions of N 2 at 77 K and CO 2 at 273 K. The impregnation ration had a strong influence on the pore structure of these ACs, which could be easily controlled by simply varying the proportion of ZnCl 2 used in the activation. Thus, low impregnation ratio led to essentially microporous ACs. At intermediate impregnation ratios, ACs with wider pore size distribution (from micropores to mesopores) were obtained. Finally, high impregnation ratios yielded essentially mesoporous carbons with high surface area and pore volume. The four best-fit three-parameter isotherms Sips, Toth, Radke–Prausnitz and Vieth–Sladek suggests that the sorption capacity of activated carbon of cassava peel to uptake copper ions to be 55 mg/g.

Decolorization and COD reduction of paper industrial effluent using electro-coagulation

Electro-coagulation is an effective technique for treatment of pulp and paper industrial effluent. The influence of electrolysis time, applied charge density, electrolyte pH and supporting electrolyte on electro-coagulation efficiency for the treatment of pulp and paper industrial effluent has been attempted in the present investigation. It has been observed from the present experimental results that the effluent can be effectively treated using electro-coagulation. The maximum color removal efficiencies were recorded as 92% and 84% for mild steel and aluminum electrode respectively. The maximum COD reduction has been recorded as 95% and 89%. Experiments were also carried out coupling electro-coagulation with sequential batch reactor (SBR) to improve the efficiency of biochemical treatment by increasing the biodegradability index through electro-coagulation. The electro-coagulation was modeled using various adsorption isotherms and observed that the Langmuir and Radke–Prausnitz isotherm models predictions match satisfactorily with the experimental observations.

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.

Development of parthenium based activated carbon and its utilization for adsorptive removal of p-cresol from aqueous solution

The activated carbon was prepared from carbonaceous agriculture waste Parthenium hysterophorous by chemical activation using concentrated H 2SO 4 at 130 ± 5 °C. The prepared activated carbon was characterized and was found as an effective adsorbent material. In order to test the efficacy of parthenium based activated carbon (PAC), batch experiments were performed to carryout the adsorption studies on PAC for the removal of highly toxic pollutant p-cresol from aqueous solution. The p-cresol adsorption studies were also carried out on commercial grade activated carbon (AC) to facilitate comparison between the adsorption capabilities of PAC and AC. For PAC and AC, the predictive capabilities of two types of kinetic models and six types of adsorption equilibrium isotherm models were examined. The effect of pH of solution, adsorbent dose and initial p-cresol concentration on adsorption behaviour was investigated, as well. The adsorption on PAC and on AC was found to follow pseudo-first order kinetics with rate constant 0.0016 min −1 and 0.0050 min −1, respectively. The highest adsorptive capacity of PAC and AC for p-cresol solution was attained at pH 6.0. Further, as an adsorbent PAC was found to be as good as AC for removal of p-cresol upto a concentration of 500 mg/l in aqueous solution. Freundlich, Redlich–Peterson, and Fritz–Schlunder models were found to be appropriate isotherm models for PAC while Toth, Radke–Prausnitz and Fritz–Schlunder were suitable models for AC to remove p-cresol from aqueous solution.

Kinetic and equilibrium models for biosorption of Cr(VI) on chemically modified seaweed, Cystoseira indica

The biosorption data of hexavalent chromium by marine brown algae Cystoseira indica, which was chemically modified by crosslinking with epichlorohydrin (CB1, CB2), or oxidized by potassium permanganate (CB3), or only washed with distilled water (RB), has been used for kinetic studies based on fractional power, Elovich, pseudo-first order and pseudo-second order rate expressions. Five three parameter biosorption isotherm models, viz. Redlich–Peterson, Sips, Khan, Radke–Prausnitz and Toth are tested for their applicability apart from 6 two-parameter models. Non-linear curve fitting procedure was adopted for fitting the kinetic as well as equilibrium data in the kinetic and isotherm models and for the determination of parameters. The time-dependent Cr(VI) biosorption data were well-described by pseudo-second-order kinetic model. The intraparticle diffusion study revealed that film diffusion might be involved in Cr(VI) biosorption in the present case. Among the two-parameter models, the Langmuir model produces the best fit, while, among the three-parameter models, the best fit is produced by the Khan model, for the biosorption of Cr(VI) on all the four biosorbents studied.

Numerical study of the adsorption of dyes from textile effluents

The textile industry is one of the greatest generators of liquid effluents, due to the high quantities of water used in the dyeing process. Fixed bed adsorption columns using activated carbon have been widely used in industrial processes for the removal of contaminants from textile effluents. In this study we present the modelling of an adsorption process applied to textile dyes, using fixed bed columns. This model permits the prediction of the dye concentration at the adsorption column outlet, considering the influence of various operational parameters. The adsorption isotherms of the dye Basic Green 4, over granular activated carbon at 25 °C in an aqueous solution, were determined experimentally through a comprehensive series of tests. The Langmuir and Radke–Prausnitz models gave the best results for the adsorption isotherms. Tests were carried out in fixed bed columns to determine the breakthrough curves, with variations in feed rate, feed concentration, diameter of the column and mass transfer coefficient. The experimental conditions were simulated using a transient mathematical model. The data obtained numerically and experimentally were compared to validate the mathematical model proposed.