Nickel and cobalt sorption on anaerobic granular sludges: kinetic and equilibrium studies

The kinetics and equilibria of sorption of the divalent metal ions cobalt and nickel onto anaerobic granular sludge are described. Single component and binary equimolar systems were studied at different pH values (pH 6, 7 and 8). The kinetic modelling of metal sorption by anaerobic granular sludge has been carried out using Lagergren equations. On fitting the experimental kinetic data both in first‐ and pseudo‐second‐order equations, the regression analysis of a pseudo‐second‐order equation gave a higher r² value, indicating that both external mass transfer and intra‐particle diffusion are involved in the sorption process. The experimental isotherm data were analysed using the Langmuir, Freundlich and Redlich–Peterson equations. The Redlich isotherm, a combination of the Langmuir and Freundlich equations, was found to have the highest regression correlation coefficients at pH 7. At pH 8, the Langmuir mechanism dominated for cobalt and nickel adsorption. In contrast, at pH 6, the Freundlich equation gave a better correlation coefficient which suggests a more heterogeneous adsorption at that pH. The maximal adsorption capacity of the granular sludge, as determined by the Langmuir equation, for cobalt or nickel in single systems (8.92 mg g^?1 Co TSS; 9.41 mg g^?1 Ni TSS, pH 7) compared with binary systems (8.06 mg g^?1 Co TSS; 8.43 mg g^?1 Ni TSS, pH 7) showed no great difference in the accumulation of these metals onto granular sludge. Copyright © 2004 Society of Chemical Industry     

Biosorption of heavy metals from aqueous solution using modified activated carbon: comparison of linear and nonlinear methods

BACKGROUND: Biosorption of heavy metals from aqueous solution by modified activated carbon with Phanerochaete chrysosporium immobilised in Ca‐alginate beads was investigated using a batch system and comparison of linear and nonlinear methods. RESULTS: The amount of Cu(II), Zn(II) and Pb(II) ion sorption by the beads was as follows: activated carbon with P. chrysosporium immobilised in Ca‐alginate beads (ACFCA) (193.4, 181.8, 136.6 mg g^?1) > activated carbon immobilised in Ca‐alginate beads (ACCA) (174.8, 162.0, 130.7 mg g^?1) > P. chrysosporium (F) (148.8, 125.6, 120.4 mg g^?1) > activated carbon (AC) (138.8, 112.3, 109.3 mg g^?1) > plain Ca‐alginate beads (PCA) (125.4, 105.2, 98.2 mg g^?1). The widely used Langmuir and Freundlich isotherm models were utilised to describe the biosorption equilibrium process. CONCLUSION: The results of this study suggest that the immobilisation of modified activated carbon with P. chrysosporium in Ca‐alginate beads is suitable for a batch system. The isotherm parameters were estimated using linear and nonlinear regression analyses. The surface charge density of the biosorbents varied with the pH of the medium; the maximum biosorption of heavy metal ions on the biosorbents was obtained when the pH was between 5.6 and 7.4. Copyright © 2008 Society of Chemical Industry     

Biosorption of Pb(II) and Ni(II) ions by chemically modified Eclipta alba stem powder: Kinetics and equilibrium studies

Biosorption of Pb(II) and Ni(II) ions onto the Eclipta alba stem powder (EAS) was investigated in a batch system. The biosorbent was characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), transmission electron microscopy (TEM) and elemental analysis. Adsorption influencing factors like pH, adsorbent dose, initial metal ion concentration and contact time were investigated. The adsorption mechanism of Pb(II) and Ni(II) followed the pseudo-second-order kinetic model (R² > 0.998). The Langmuir isotherm model fitted well and the maximum monolayer adsorption capacity of the sorbent for Pb(II) and Ni(II) was found to be 66.2 ± 1.9 mg g^?1and 62.5 ± 1.8 mg g^?1, respectively. Desorption and recovery were carried out using dilute HCl solution.     

Biosorption of Strontium Ions by Magnetically Modified Yeast Cells

The sorption of Sr²⁺ ions from aqueous solutions on magnetically modified fodder yeast (Kluyveromyces fragilis) cells and their subsequent desorption were studied. The Sr²⁺ sorption increased with increasing pH and reached a plateau between pH 4.0 and 7.0. The changes of temperature slightly influenced the sorption process. The sorption values were 19.5 mg g^?1 and 53.5 mg g^?1 for 10 mg L^?1 and 40 mg L^?1 Sr²⁺ solutions respectively after 20 min incubation at a pH higher than 4. The Langmuir isotherm was successfully used to fit experimental data; the maximum adsorption capacity was 140.8 mg g^?1 under optimal conditions. The adsorbed Sr²⁺ ions can be desorbed with nitric acid (0.1 mol L^?1).     

Highly Efficient Adsorption of Anionic Dyes from Aqueous Solutions Using Sawdust Modified by Cationic Surfactant of Cetyltrimethylammonium Bromide

In the present study, the adsorption behavior of Congo Red (CR) dye from aqueous systems onto sawdust modified by cetyltrimethylammonium bromide, CH₃(CH₂)₁₅N(CH₃)₃Br (CTAB) was attempted. Adsorption experiments were carried out using both batch and column modes under various operating conditions. The effects of some important parameters such as solution pH, adsorbent dosage, initial dye concentration and contact time were investigated. Treatment of the equilibrium data obtained in batch experiments was carried out using Langmuir and Freundlich isotherm equations. Based on the isotherm analysis, it was found that the adsorption of CR dye onto SD fits well to the Langmuir model and the adsorption pattern on CTAB modified sawdust (CTAB/SD) followed the Freundlich isotherm which is indicative of heterogeneity of the adsorption sites on the surfactant-modified sawdust. The maximum adsorption capacity of SD and CTAB/SD were found to be 5.2 and 9.1?mg?g^?1, respectively, according to the Langmuir model. However, much higher differences in sorption capacities were observed for CTAB/SD and SD in the column system (66.73?mg?g^?1). In order to find out the possibility of the exhausted column for frequent use, a regeneration study was also carried out. It was found that the dye uploaded column can be easily regenerated with a high performance using ethanol as the washing solution.     

Adsorption equilibrium,thermodynamics, kinetics,mechanism and process design of zinc(II) ions onto cashew nut shell

Cashew nut shell (CNS) is an agricultural waste was investigated as a new adsorbent for the removal of zinc(II) from aqueous environment. Effects of solution pH, CNS dose, contact time, initial zinc(II) concentration and temperature on removal efficiency were tested and optimum conditions were evaluated. The equilibrium data were fitted well with Langmuir isotherm model and pseudo‐second‐order kinetic model. Langmuir monolayer adsorption capacity of CNS was examined as 24.98 mg/g. Changes in standard Gibbs free energy (?G°), standard enthalpy (?H°) and standard entropy (?S°) showed that the sorption of zinc(II) ions onto CNS are spontaneous and exothermic at 303–333 K. Sorption process was found to be controlled by both surface and pore diffusion. A batch adsorber was designed for different CNS dose to effluent volume ratios using Langmuir equation. Effective diffusivity values were found to be 1.927 × 10^?11 (10 mg/L), 2.135 × 10^?11 (20 mg/L), 2.267 × 10^?11 (30 mg/L), 2.305 × 10^?11 (40 mg/L) and 2.362 × 10^?11 (50 mg/L) m²/s. © 2011 Canadian Society for Chemical Engineering     

Biosorption of phenolic compounds from aqueous solutions onto chitosan–abrus precatorius blended beads

BACKGROUND: This research focuses on understanding the biosorption process and developing a cost‐effective technology for the treatment of water contaminated with phenolic compounds (phenol, 2‐chlorophenol and 4‐chlorophenol), which are discharged into the aquatic environment from a variety of sources and are highly toxic. In order to remove phenolic compounds from water, a new biobased sorbent is developed, blending chitosan with abrus precatorius, both naturally occurring biopolymers. The resulting chitosan–abrus precatorius blended beads (CS/Ab) were characterized by Brunauer, Emmett and Teller (BET) analysis, Fourier Transform Infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques under batch equilibrium and column flow experimental conditions. The binding capacity of the biosorbent was investigated as a function of initial pH, contact time, initial concentration of adsorbate and dosage of adsorbent. RESULTS: The percentage removal of phenol, 2‐CP and 4‐CP increased with increasing adsorbent dose, while the adsorption capacity at equilibrium, q_e (mg g^?1) (amount of phenol, 2‐CP and 4‐CP loaded per unit weight of adsorbent) decreased. The equilibrium time was found to be 240 min for full equilibration of all adsorbates. Adsorption kinetic and isotherm studies showed that the pseudo‐first‐order model and the Langmuir isotherm were the best choices to describe the adsorption behaviors. The maximum monolayer adsorption capacity of phenol, 2‐CP and 4‐CP on to the (CS/Ab) beads was found to be 156 mg g^?1, 204 mg g^?1 and 278 mg g^?1, respectively. CONCLUSION: The experimental results suggested that (CS/Ab) blended beads are effective in the removal of phenolic compounds from aqueous medium. Copyright © 2009 Society of Chemical Industry     

Polymeric superabsorbing composite prepared using a glow‐discharge electrolysis plasma for the removal of divalent heavy metal ions from aqueous solutions and its swelling properties

A novel polymeric superabsorbing composite was prepared using the graft copolymerization of acrylic acid (AANa, 70% neutralization with NaOH) and 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS) onto the hydroxyethyl cellulose (HEC) [HEC‐g‐P(AANa‐co‐AMPS)], which was initiated by means of a glow‐discharge electrolysis plasma rather than a chemical initiator. The composite material was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA). We obtained absorbencies of 2490 g g^?1 for distilled water and of 109 g g^?1 for 0.9 wt% NaCl solution. Results show that the maximum adsorption capacities for Ni(II), Cu(II), Cd(II), Pb(II), and Hg(II) from aqueous solution were 974.84, 975.43, 1535.52, 1970.47, and 1879.53 mg g^?1, respectively. The adsorption isotherm followed the Langmuir isotherm model very well. Adsorption kinetics results indicate that the fast adsorption rate followed the pseudo‐second‐order kinetics equations. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

L-cystein modified bentonite-cellulose nanocomposite (cellu/cys-bent) for adsorption of Cu2+, Pb2+, and Cd2+ ions from aqueous solution

In this study, L-cystein modified bentonite-cellulose (cellu/cys-bent) nanocomposite was synthesized and characterized by XRD, FTIR, SEM with EDS, TGA, and TEM techniques. In order to optimize the process the effect of various operational parameters such as pH, adsorbent dosage, contact time, and temperature were also investigated. The adsorption experiments were carried out in initial concentrations range of 20-100 mg L^?1and the adsorbent affinity for metal ions was found to be in order of Cu²⁺ > Pb²⁺ > Cd²⁺. The optimum pH for adsorption of Cu²⁺ and Cd²⁺ was observed at 5 while for Pb²⁺ it was pH 6. Based on the Langmuir model, the maximum adsorption capacity of Cu²⁺, Pb²⁺, and Cd²⁺ at 50^?C was found to be 32.36, 18.52, and 16.12 mg g^?1, respectively. The Langmuir isotherm and pseudo-second order model were found to be better fitted than the other isotherms and kinetic models. The results of thermodynamic parameters confirmed the process to be endothermic and spontaneous in nature.     

Equilibrium,kinetic, diffusion and thermodynamic applications for dye adsorption with pine cone

ABSTRACT

In the present study, the adsorption of methylene blue onto pine cone was investigated. Adsorbent was characterized by XRD and SEM. The adsorption data follow the Langmuir isotherm model. Maximum adsorption capacity was calculated 125 mg.g^?1 . It was determined that the pseudo-second-order model was the best choice among all the available kinetic models to describe the adsorption behaviour. E_a was found to be 19.57 kJ mol^?1. This confirms the fact that the adsorption was a physical process. The negative free energy values indicate the feasibility of the adsorption process and its spontaneous nature.     

Kinetics and Equilibrium Studies for the Removal of Cobalt,Manganese, and Silver in Ethanol using Dowex 50W-x8 Cation Exchange Resin

Organic solvents such as ethanol, find a wide range of applications in fuel, pharmaceutical industries, food industries, and paint formulations, among others. The removal of Ag(I), Co(II), and Mn(II) ions in ethanol by cation exchange resin, Dowex 50W-x8, was investigated. The adsorption characteristics of metal ions onto Dowex 50W-x8 resin were described by Langmuir isotherms. The maximum sorption exchange capacities at 298 K were obtained as 47.4 mg g^?1, 52.6 mg g^?1, and 58.5 mg g^?1 for Ag(I), Co(II), and Mn(II), respectively. The data was also fitted to Temkin and Dubinin-Radushkevich adsorption isotherm models to evaluate other adsorption properties. The ion exchange of silver, cobalt, and manganese on cation exchange resin followed pseudo-second-order kinetics, and the intraparticle diffusion was rate-determining step. The thermodynamic parameters indicated that the sorption of metal ions onto Dowex 50W-x8 resin was spontaneous (negative ΔG°) and endothermic in nature (positive ΔH°) implying that the adsorption capacity increased with increasing temperature. The resin can be regenerated by eluting metal ions with 3.0 mol L^?1 HNO₃ followed by washing it with 10 mL of Millipore water and 10 mL of 2.0 M NaOH, respectively. The proposed method was applied for metal ion removal in real ethanol samples.     

Removal of Reactive Dyes using Magnetically Separable Trametes versicolor Cells as a New Composite Biosorbent

Magnetically modified Trametes versicolor cells were used for biosorption of Reactive Blue 13 (RB13), Reactive Yellow 85 (RY85) and Reactive Violet 1 (RV1). Percent biosorption values and maximum adsorption capacities of 98.30% and 135.35 mg g^?1 for RB13, 96.02% and 125 mg g^?1 for RY85, and 98.56% and 227.27 mg g^?1 for RV1 were observed under optimal conditions. The biosorption of all dyes was exothermic in nature. The biosorbent was characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and magnetic force microscopy. The Langmuir model was found to be most suitable for describing the biosorption of all dyestuffs. The experimental data fitted very well the pseudo second order kinetic model.     

Sorptive removal of methylene blue from aqueous solutions by polymer/activated charcoal composites

In this study, a new sorbent, a poly(acrylamide‐co‐itaconic acid) [P(AAm‐co‐IA)]/activated charcoal (AC) composite, was prepared by the aqueous polymerization of acrylamide and itaconic acid in the presence of AC with N,N′‐methylene bisacrylamide as a crosslinker and potassium persulfate as an initiator. The P(AAm‐co‐IA)/AC composite sorbent showed a fair capacity to adsorb the cationic dye methylene blue. The maximum sorption capacity, as studied at 23, 37, and 50°C and determined with the Langmuir isotherm model, was found to be 909.0, 312.5, and 192.3 mg/g, respectively. For an initial concentration of 5 mg/L, the kinetic uptake data were studied with various kinetic models. The pseudo‐second‐order equation was found to fairly fit the uptake data with a regression value of 0.999. The dye uptake increased with the pH of the sorbate solution, and the optimum pH was found to be in the range of 7–10. Intraparticle diffusion was also observed to take place, and the coefficient of intraparticle diffusion was evaluated to be 26.51 × 10^?2 mg g^?1 min^?1/2. The various thermodynamic parameters were also determined to predict the nature of the uptake process. The sorption process was found to be spontaneous, as indicated by a negative standard free energy change. The negative standard enthalpy change suggested an exothermic nature for the uptake. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Adsorptive removal of anionic and non‐ionic surfactants from aqueous phase using Posidonia oceanica (L.) marine biomass

BACKGROUND: In this study, the capability of low‐cost, renewable and abundant marine biomass Posidonia oceanica (L.) for adsorptive removal of anionic and non‐ionic surfactants from aqueous solutions have been carried out in batch mode. Several experimental key parameters were investigated including exposure time, pH, temperature and initial surfactant concentration. RESULTS: It was found that the highest surfactant adsorption capacities reached at 30 °C were determined as 2.77 mg g^?1 for anionic NaDBS and as 1.81 mg g^?1 for non‐ionic TX‐100, both at pH 2. The biosorption process was revealed as a thermo‐dependent phenomenon. Equilibrium data were well described by the Langmuir isotherm model, suggesting therefore a homogeneous sorption surface with active sites of similar affinities. The thermodynamic constants of the adsorption process (i.e. ΔG°, ΔH° and ΔS°) were respectively evaluated as ? 8.28 kJ mol^?1, 48.07 kJ mol^?1 and ? 42.38 J mol^?1 K^?1 for NaDBS and ? 9.67 kJ mol^?1, 95.13 kJ mol^?1 and ? 174.09 J mol^?1 K^?1 for TX‐100. CONCLUSION: Based on this research, valorization of highly available Posidonia oceanica biomass, as biological adsorbent to remove anionic and non‐ionic surfactants, seems to be a promising technique, since the sorption systems studied were found to be favourable, endothermic and spontaneous. Copyright © 2007 Society of Chemical Industry     

Biosorption of methylene blue from aqueous solution by softstem bulrush (Scirpus tabernaemontani Gmel.)

BACKGROUND: The removal of methylene blue from aqueous solution was studied using softstem bulrush (Scirpus tabernaemontani Gmel.) as the biosorbent. The effects of various parameters including contact time, biosorbent dosage, ionic strength and solution pH on the biosorption were investigated. RESULTS: The sorption capacity increased with an increase in biosorbent dosage and a decrease in ionic strength. The equilibrium time was found to be 240 min for full equilibration. Pseudo‐first‐order, pseudo‐second‐order, Bangham equation and intraparticle diffusion models were applied to fit the kinetic data, and the results showed that the sorption process followed the pseudo‐second‐order model. Equilibrium data conformed to Langmuir and Redlich–Peterson isotherm models, with a maximum monolayer biosorption capacity of 53.8 mg g^?1 for the Langmuir isotherm at 18 °C. The value of ΔG was estimated to be ? 29.24 kJ mol^?1, indicating the spontaneous nature of the biosorption. The biosorption process was strongly pH‐dependent and favourable at alkaline pH. CONCLUSION: Softstem bulrush, which is readily available and inexpensive, could be employed as a promising biosorbent for the removal of dye. Copyright © 2008 Society of Chemical Industry     

Studies on the removal of Cobalt(II) from aqueous solutions by adsorption with Ficus benghalensis leaf powder through response surface methodology

Suitability of Ficus benghalensis leaf powder for the adsorptive removal of Cobalt(II) from aqueous solutions is exhaustively studied and is reported in this article. Experimentation based on response surface methodology is conducted to understand the interaction among the variables—metal ion concentration, adsorbent dosage, initial solution pH and temperature that are of significance in the treatment. A 20?mg?L^?1 of Cobalt(II) solution, treated with 25?g?L^?1 of adsorbent at a pH of 5.0 and a temperature of 303?K, yielded 98.73% removal of Cobalt(II). Langmuir isotherm proved to be a better model representation of the equilibrium. Adsorption kinetics is of pseudo second rate form. Maximum sorption capacity of F. benghalensis leaf powder, q_max, is found to be 5.65?mg?g^?1. Adsorption is endothermic and spontaneous in nature. Study on surface morphology is included in the study.     

Removal of chromium (VI) from aqueous solutions using poly(4‐vinyl pyridine) beads

Sorption of hexavalent chromium ions from aqueous solution by poly 4‐vinyl pyridine [Poly(4‐VP)] was studied. The batch method was applied for adsorption processes. The effects of initial ion concentration, time, pH and temperature on adsorption were investigated. A treatment time of 60 min was found to be sufficient to reach equilibrium. pH 3.0 was found as the optimum pH value for the process. The maximum adsorption performance was achieved at 86.7 mg g^?1 using 500 mg L^?1 Cr (VI) solutions. The process of adsorption of Cr (VI) was explained by Langmuir isotherm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2865–2870, 2006     

Magnetite‐loaded calcium‐alginate (MLCA) particles as potential sorbent for removal of Ni(II) from aqueous solution

This work is focused on the removal of Ni(II) from aqueous solutions by sorption onto newly developed magnetite‐loaded calcium alginate particles. The uptake of Ni(II) by these magnetite particles, with their mean geometrical diameter 84 and 508 μm, is best described by the Freundlich isotherm and the constants K_F and 1/n were found to be 3.491 mg g^?1, 0.731 and 0.793 mg g^?1 and 0.907, respectively. The mean sorption energy, as determined by Dubinin‐Radushkevich isotherm for 508‐ and 84‐μm sized particles was evaluated to be 8.9 and 8.0 kJ mol^?1, respectively, thus, suggesting the ion‐exchange mechanism for uptake process. Of the various kinetic models proposed, the kinetic Ni(II)‐uptake data were best interpreted by “Simple Elovich” and “Power function” as suggested by their higher regression values. The almost linear nature of plots of log(% sorption) versus log(time) was indicative of intraparticle diffusion. The values of intraparticle diffusion coefficients K_id were found to be 63.49 × 10^?2 and 94.35 × 10^?2 mg l^?1 min^0.5. The intraparticle diffusion was also confirmed by Bangham equation. Finally, various thermodynamic parameters were evaluated. The negative ΔG° indicated spontaneous nature of uptake process while positive ΔH° value suggested exothermic nature of the sorption process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Removal of Lead(II) from Aqueous Solutions using Pre-boiled and Formaldehyde-Treated Onion Skins as a New Adsorbent

The adsorption characteristics of Pb²⁺ on pre-boiled treated onion skins (PTOS) and formaldehyde-treated onion skins (FTOS) were evaluated. The effects of Pb²⁺ initial concentration, agitation rate, solution pH, and temperature on Pb²⁺ adsorption were investigated in batch systems. Pb²⁺ adsorption was found to increase with increase in initial concentration. The point of zero net charge (PZC) was 6.53. The optimum pH for the maximum removal of Pb²⁺ was 6.0. The adsorption equilibrium data was best represented by the Langmuir isotherm model for FTOS and the Freundlich isotherm model for PTOS. The maximum amounts of Pb²⁺ adsorbed (qm), as evaluated by the Langmuir isotherm, was 200 mgg^?1 for FTOS. The efficiencies of PTOS and FTOS for Pb²⁺ removal were 84,8.0% and 93.5% at 0.15 g/200 mL^?1 adsorbent dose, respectively. (C ₀ = 50 mg L^?1). Study concluded that onion skins, a waste material, have good potential as an adsorbent to remove toxic metals like Pb²⁺ from water. Boehm titration analysis was conducted to determine the surface groups. It was found that the adsorption kinetics of Pb²⁺ obeyed pseudo-first-order kinetic model as based on Δq (%) values. FTIR and SEM images before and after adsorption was recorded to explore changes in adsorbent-surface morphology. Activation energy (Ea) was obtained as 25.596 kJ/mol.