Thermodynamic,kinetic, and equilibrium studies on phenol removal by use of cashew nut shell

Adsorption of phenol from aqueous solution onto cashew nut shell (CNS) was investigated to assess the possible use of this adsorbent. The influence of various parameters such as contact time, phenol concentration, adsorbent dose, pH, and temperature has been studied. Studies showed that the pH of aqueous solutions affected phenol removal as a result of decrease in removal efficiency with increasing solution pH. The experimental data were analysed by the Langmuir equation. Equilibrium data fitted well with the Langmuir model with maximum monolayer adsorption capacity of 5.405 mg/g. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° have also been evaluated and it has been found that the sorption process was feasible, spontaneous, and exothermic in nature. The pseudo‐first‐order and pseudo‐second‐order kinetic models were selected to follow the adsorption process. Kinetic parameters, rate constants, equilibrium sorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was shown that the adsorption of phenol could be described by the pseudo‐second‐order equation, suggesting that the adsorption process is presumable a chemisorption. The CNS investigated in this study showed good application potential for the removal of phenol from aqueous solution.     

Utilization of Raw and Activated Date Pits for the Removal of Phenol from Aqueous Solutions

Activated carbons prepared from date pits, an agricultural waste byproduct, have been examined for the adsorption of phenol from aqueous solutions. The activated carbons were prepared using a fluidized bed reactor in two steps; carbonization at 700 °C for 2 hours in N₂ atmosphere and activation at 900 °C in CO₂ atmosphere. The kinetic data were fitted to the models of intraparticle diffusion, pseudo‐second order, and Lagergren, and followed more closely the pseudo‐second‐order chemisorption model. The isotherm equilibrium data were well fitted by the Freundlich and Langmuir models. The maximum adsorption capacity of activated date pits per Langmuir model was 16 times higher than that of nonactivated date pits. The thermodynamic properties calculated revealed the endothermic nature of the adsorption process. The uptake of phenol increased with increasing initial phenol concentration from10 to 200 ppm and temperature from 25 to 55 °C, and decreased with increasing the solution pH from 4 to 12. The uptake of phenol was not affected by the presence of NaCl salt.     

Liquid Phase Adsorption of Phenol and Chloroform by Activated Charcoal

The adsorption equilibria of phenol and chloroform from aqueous solutions on four different particle sizes of activated charcoal were examined at different initial concentrations of the adsorbates. The experimental data were analyzed using the Langmuir and Freundlich isotherm models. Both models fit the adsorption data for phenol. The Freundlich model more accurately fits the adsorption data for chloroform than the Langmuir model. The sorption kinetics for phenol was studied using pseudo‐first‐order and second‐order kinetic models. The adsorption data better fit the second‐order model. The results of the study show that activated charcoal can be used as potential adsorbent for phenol and chloroform in drinking water.     

The use of Jatobá bark for removal of cationic dyes

In this work, the application of Jatobá bark (the waste product of medicinal plant processing) in removal of the cationic dyes Methylene Blue, Crystal Violet and Rhodamine B from aqueous solution was studied in a batch system. The effect of contact time, pH and temperature on dye removal was investigated. An increase in pH from 2 to 10 was accompanied by an increase in the amount of dye adsorbed. The equilibrium sorption data fitted to the Langmuir, Freundlich and Langmuir–Freundlich equations were investigated. The Langmuir–Freundlich isotherm exhibited the best fit with the experimental data and the maximum adsorption capacities at room temperature being 211.5, 89.5 and 69.4 for Rhodamine B, Methylene Blue and Crystal Violet, respectively. The kinetic sorption was evaluated by the pseudo‐first‐order, pseudo‐second‐order and intraparticle diffusion models. It was observed that sorption follows the pseudo‐second‐order kinetic model. The thermodynamic parameters for the sorption process were also determined. The spontaneous and endothermic nature of adsorption was obtained based on the negative value of free energy (ΔG) and the positive value of enthalpy (ΔH). The results indicate that Jatobá bark could be used as a low‐cost material for the removal of cationic dyes from wastewater.     

Methylamino‐group‐modified hypercrosslinked polystyrene resin for the removal of phenol from aqueous solution

Chemical modification was performed for macroporous crosslinked chloromethylated polystyrene. The obtained HJ‐K01 resin was used to remove phenol from aqueous solution, and its adsorption behaviors for phenol were compared with commercial Amberlite XAD‐4. The results indicate that methylamino groups were successfully uploaded onto the surface of the HJ‐K01 resin and the adsorption capacity of phenol onto the HJ‐K01 resin was much larger than that onto XAD‐4. Furthermore, the original phenol solution was suitable for the adsorption, the adsorption isotherms could be fitted by the Freundlich model, and its kinetic curves could be characterized by a pseudo‐second‐order rate equation. The fixed‐bed column adsorption demonstrated that the HJ‐K01 resin was an excellent resin for the removal of phenol. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of porous chitosan–tripolyphosphate beads for copper(II) ion adsorption

Porous chitosan–tripolyphosphate beads, prepared by the ionotropic crosslinking and freeze‐drying, were used for the adsorption of Cu(II) ion from aqueous solution. Batch studies, investigating bead adsorption capacity and adsorption isotherm for the Cu(II) ion, indicated that the Cu(II) ion adsorption equilibrium correlated well with Langmuir isotherm model. The maximum capacity for the adsorption of Cu(II) ion onto porous chitosan–tripolyphosphate beads, deduced from the use of the Langmuir isotherm equation, was 208.3 mg/g. The kinetics data were analyzed by pseudo‐first, pseudo‐second order kinetic, and intraparticle diffusion models. The experimental data fitted the pseudo‐second order kinetic model well, indicating that chemical sorption is the rate‐limiting step. The negative Gibbs free energy of adsorption indicated a spontaneous adsorption, while the positive enthalpy change indicated an endothermic adsorption process. This study explored the adsorption of Cu(II) ion onto porous chitosan–tripolyphosphate beads, and used SEM/EDS, TGA, and XRD to examine the properties of adsorbent. The use of porous chitosan–tripolyphosphate beads to adsorb Cu(II) ion produced better and faster results than were obtained for nonporous chitosan–tripolyphosphate beads. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Selective Adsorption of Phenol and Nitrobenzene by β‐Cyclodextrin‐Intercalated Layered Double Hydroxide: Equilibrium and Kinetic Study

The composite of carboxymethyl‐modified β‐cyclodextrin‐intercalated ZnAl‐layered double hydroxide (CMCD‐LDH) was investigated for selective adsorption of phenol (Ph) and nitrobenzene (NB). The Freundlich model can be used to describe satisfactorily the adsorption isotherms of Ph and NB. The adsorption capacity of CMCD‐LDH for Ph and NB increases with the increase of temperature, indicating the endothermic nature of this sorption process. CMCD‐LDH exhibits preferential adsorption for Ph over NB at pH 6.5 due to the selective recognition of the interlayer CMCD cavity. Pseudo‐first‐order and pseudo‐second‐order kinetic models were applied to simulate the kinetics of the adsorption process. The calculated q_e values based on the pseudo‐second‐order model are much closer to the experimental data q_e,exp. As a result, the pseudo‐second‐order kinetic model is more reasonable to describe the adsorption process of Ph and NB onto the CMCD‐LDH composite. CMCD‐LDH can be potentially applied in selective adsorption and separation of wastewater pollutants.     

Kinetic analysis of the sorption of copper(II) ions on chitosan

The removal of copper ions from aqueous effluents by chitosan was studied in equilibrium and agitated batch contacting systems. The sorption capacities of chitosan for copper ions are 1.26 and 1.12 mmol g^?1 at pH 3.5 and 4.5, respectively. The equilibrium experimental data were best correlated by the Langmuir equation. The kinetics of sorption were studied at an initial solution pH of 4.5 and a chitosan particle size of 355–500 µm. The kinetics were analyzed using four models: the pseudo‐first‐order, pseudo‐second‐order, modified second‐order and Elovich equations. The rate parameters for the four models were determined and the Elovich equation provided the best correlation of the experimental kinetic data. Copyright © 2003 Society of Chemical Industry     

Fixed‐Bed and Batch Adsorption of Pharmaceuticals from Aqueous Solutions on Ionic Liquid‐Modified Montmorillonite

Batch and column adsorption of four pharmaceuticals, namely, tetracycline (TC), sulfamethoxazole (SMZ), nalidixic acid (NAD), and chloramphenicol (CHL) on ionic liquid modified montmorillonite (Mt‐IL) was evaluated. The effects of variation in pH and contact time were analyzed and the data were fitted to kinetics and isotherm models. The equilibrium experimental data were best explained by the Freundlich model. A pseudo second‐order kinetic model described all pharmaceuticals adsorbed on Mt‐IL. In column studies, the exchange zone depth, adsorption capacity, the required time for the pharmaceuticals to move through the height of the adsorbent in the column, and adsorption rates were investigated by the Yoon‐Nelson and the Thomas and Adams‐Bohart models.     

Synthesis and characterization of glutaraldehyde‐crosslinked calcium alginate for fluoride removal from aqueous solutions

A novel biosorbent was developed by the crosslinking of an anionic biopolymer, calcium alginate, with glutaraldehyde. The glutaraldehyde‐crosslinked calcium alginate (GCA) was characterized by Fourier transform infrared spectroscopy and porosity and surface area analysis. The batch equilibrium and column flow adsorption characteristics of fluoride onto the biosorbent were studied. The effects of the pH, agitation time, concentration of adsorbate, and amount of adsorbent on the extent of adsorption were investigated. The experimental data were fitted to the Langmuir and Freundlich adsorption isotherms. The data were analyzed on the basis of the Lagergren pseudo‐first‐order, pseudo‐second‐order, and Weber–Morris intraparticle diffusion models. The maximum monolayer adsorption capacity of the GCA sorbent as obtained from the Langmuir adsorption isotherm was found to be 73.5 mg/g for fluoride. The χ² and sum of squares of the error analysis were used to correlate the equilibrium isotherm models and kinetics. In addition, breakthrough curves were obtained from column flow experiments. The experimental results demonstrate that the GCA beads could be used for the defluoridation of drinking water through adsorption. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The effect of dye chemical structure on adsorption on activated carbon: a comparative study

The effect of the molecular structure of dyes Eriochrome Black T and Bromophenol Blue on their adsorption on the surface of activated carbon manufactured from locally available biosorbent has been studied. Batch experiments were performed to investigate factors that may affect the adsorption process. The effect of stirring rate was investigated in the range 0–240 rpm, with an initial concentration of 4–100 mg/l and a stirring time of 0–400 min. The mechanism and rate of adsorption were investigated for both dyes using pseudo‐first‐order, pseudo‐second‐order, intraparticle diffusion, and liquid film diffusion models. The monolayer adsorption capacities for Eriochrome Black T and Bromophenol Blue were found to be 36.5 and 39.68 mg/g respectively. The difference in dye uptake was attributed to the presence of the electron‐withdrawing bromine group in Bromophenol Blue. Results showed that the Langmuir isotherm best fitted the adsorption of the two dyes on the prepared activated carbon. The pseudo‐second‐order model best fitted the experimental data, and liquid film diffusion and intraparticle diffusion were the controlling adsorption mechanisms.     

Study of uranium sorption using D2EHPA‐impregnated polymeric beads

The extractant‐impregnated polymeric beads (EIPBs), containing Di(2‐ethylhexyl) phosphonic acid (D2EHPA) as an extractant and polyethersulfone as base polymer, were prepared by phase‐inversion method. These beads were characterized by fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscope (SEM) analysis to gain insight into the composition and morphology of beads. The beads exhibited good acid stability as no significant structural deformation or leaching out of the extractant was observed in 6M HNO₃ solution, up to the studied equilibration time of 15 days. The synthesized EIPBs were evaluated, for their ability to absorb uranium from aqueous solution, at different concentration and pH values. The kinetics measurement showed that about 90 min of equilibration time was enough to remove saturation amount of uranium from the solution. Kinetic modeling analysis of the extraction results was carried out using pseudo‐first‐order, pseudo‐second‐order, and intraparticle diffusion equations and the corresponding rate constants were determined. The equilibrium data were fitted into different isotherm models and were found to be represented well by the Freundlich isotherm equation. Reusability of the beads was also established by multiple sorption–desorption experiments. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3355–3364, 2013     

Sorption of Cd(II), Co(II), and Zn(II) Complexes with MGDA on Anion Exchange Resins: A Study of the Influence of Various Parameters

The strongly basic polystyrene gel resins Amberjet 4200, Amberjet 4600, and the macroporous strongly basic polystyrene Purolite A 520E were investigated for their sorption properties towards Cd(II), Co(II), and Zn(II) complexes with MGDA. The object of the study was the sorption behavior of three metal ions on the above-mentioned anion exchangers, depending on the metal ions’ concentration, pH, contact time, and temperature. MGDA is an alternative, environmentally friendly complexing agent. The sorption data were fitted to the Langmuir and Freundlich models. Three different kinetic behaviors: pseudo first order, pseudo second order, and intraparticle diffusion were tested. The variations of thermodynamic functions were also calculated.     

Sorption of Zn(II) and Pb(II) ions in the presence of the biodegradable complexing agent of a new generation

The macroporous chelating ion exchangers containing different functional groups i.e. Purolite S-920, Purolite S-930 and Lewatit TP-208 have been used in the sorption process of Zn(II) and Pb(II) ions. The effect of the presence of biodegradable, environmentally friendly aminopolycarboxylate chelating agent, trisodium salt of methylglycinediacetic acid (MGDA) on its sorption capacity was also examined. The investigations were carried out by the static method. Besides the effect of initial concentration of Zn(II) and Pb(II) and the complexing agent the research concerns the influence of solution pH, phase contact time on effectiveness of sorption. The equilibrium and kinetics of Zn(II)–MGDA and Pb(II)–MGDA complexes sorption were obtained and fitted using the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) models as well as the pseudo first and pseudo second order kinetic models. The intraparticle diffusion model was also used. The results showed that the sorption processes of Zn(II) and Pb(II) complexes with MGDA on Purolite S-920, Purolite S-930 and Lewatit TP-208 followed well the pseudo second order kinetics.     

Adsorption of methylene blue on hemicellulose‐based stimuli‐responsive porous hydrogel

A stimuli‐responsive porous hydrogel was synthesized from wheat straw hemicellulose using CaCO₃ as the porogen, and its application for the removal of methylene blue was studied. The porous structure of the prepared hydrogel was confirmed by SEM analysis. The effects of pH and polyelectrolyte on the swelling of the hydrogels were discussed, and the porous hydrogels showed excellent sensitivity to pH and salt. The deswelling kinetic study indicated that the hydrogels exhibited rapid shrinking in NaCl aqueous solutions. The methylene blue adsorption on the hydrogels was investigated, and the obtained adsorption data was fitted to the pseudo‐first‐order, pseudo‐second‐order and intra‐particle diffusion kinetics models, and the pseudo‐first‐order kinetic model could describe the adsorption process, and the adsorption process of methylene blue on the hydrogels was controlled by external film diffusion. This study reported that the hemicellulose‐based porous hydrogel is promising for water treatment. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41606.     

Batch and fixed‐bed column adsorption of Cu(II), Pb(II) and Cd(II) from aqueous solution onto functionalised SBA‐15 mesoporous silica

Functionalised SBA‐15 mesoporous silica with polyamidoamine groups (PAMAM‐SBA‐15) was successfully prepared with the structure characterised by X‐ray diffraction, nitrogen adsorption–desorption, Fourier transform infrared spectra and thermogravimetric analysis. PAMAM‐SBA‐15 was applied as adsorbent for Cu(II), Pb(II) and Cd(II) ions removal from aqueous solution. The effects of the solution pH, adsorbent dosage and metal ion concentration were studied under the batch mode. The Langmuir model was fitted favourably to the experimental data. The maximum sorptive capacities were determined to be 1.74 mmol g^?1 for Cu(II), 1.16 mmol g^?1 for Pb(II) and 0.97 mmol g^?1 for Cd(II). The overall sorption process was fast and its kinetics was fitted well to a pseudo‐first‐order kinetic model. The mean free energy of sorption, calculated from the Dubinin–Radushkevich isotherm, indicated that the sorption of lead and copper, with E > 16 kJ mol^?1, followed the sorption mechanism by particle diffusion. The adsorbent could be regenerated three times without significant varying its sorption capacity. A series of column tests were performed to determine the breakthrough curves with varying bed heights and flow rates. The breakthrough data gave a good fit to the Thomas model. Maximum sorption capacity of 1.6, 1.3 and 1.0 mmol g^?1 were found for Cu(II), Pb(II) and Cd(II), respectively, at flow rate of 0.4 mL min^?1 and bed height of 8 cm, which corresponds to 83%, 75% and 73% of metallic ion removal, respectively, which very close to the value determined in the batch process. Bed depth service time model could describe the breakthrough data from the column experiments properly. © 2012 Canadian Society for Chemical Engineering     

Sorption of textile dye from aqueous solution by macroporous amino‐functionalized copolymer

Macroporous poly(glycidyl methacrylate‐co‐ethylene glycol dimethacrylate) (PGME) was synthesized by suspension copolymerization and functionalized with diethylene triamine (PGME‐deta). The effect of pH, contact time, and sorbent mass on sorption efficiency of initial and functionalized copolymer sample for removal of Acid Orange 10 dye from aqueous solutions was studied. No dye was sorbed by nonfunctionalized copolymer, indicating that sorption of Acid Orange 10 by PGME‐deta is specific, through amino groups. The isotherm data are best fitted by Langmuir model, indicating homogeneous distribution of active sites in PGME‐deta as well as monolayer sorption. Sorption kinetics study showed that the sorption of Acid Orange 10 by PGME‐deta obeys the pseudo‐second‐order kinetic model. It was shown that PGME‐deta selectively sorbs Acid Orange 10 from binary solution with Bezaktiv Rot reactive dye. The comparison of sorption characteristics of PGME‐deta with activated carbon showed that this functionalized copolymer might be used as an alternative sorbent for textile dyes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Use of chemically activated cotton nut shell carbon for the removal of fluoride contaminated drinking water:Kinetics evaluation☆

Chemically activated cotton nut shell carbons (CTNSCs) were prepared by different chemicals and they were used for the removal of fluoride from aqueous solution. Effects of adsorption time, adsorbent dose, pH of the solution, initial concentration of fluoride, and temperature of the solution were studied with equilibrium, ther-modynamics and kinetics of the adsorption process by various CTNSC adsorbents. It showed that the chemical y activated CTNSCs can effectively remove fluoride from the solution. The adsorption equilibrium data correlate well with the Freundlich isotherm model. The adsorption of fluoride by the chemical y activated CTNSC is spon-taneous and endothermic in nature. The pseudo first order, pseudo second order and intra particle diffusion kinetic models were applied to test the experimental data. The pseudo second order kinetic model provided a better correlation of the experimental data in comparison with the pseudo-first-order and intra particle diffusion models. A mechanism of fluoride adsorption associating chemisorption and physisorption processes is presented allowing the discussion of the variations in adsorption behavior between these materials in terms of specific surface area and porosity. These data suggest that chemically activated CTNSCs are promising materials for fluoride sorption.     

Preparation and characterization of polysulfone/graphite nanosheets composites capsules for the adsorption of phenol in aqueous solution

In this study, the polysulfone (PSF) capsules containing graphite nanosheets (GNS) were successfully prepared by a phase inversion precipitation method. Scanning electron microscopy and thermogravimetry were employed in the characterization of the as‐prepared PSF/GNS composites capsules. Meanwhile, the adsorption properties of the composites capsules for the phenol in aqueous solution were investigated by batch methods. The results showed that the phenol adsorption uptake would be increased with the enhancement of initial concentration and adsorption time, and the adsorption of phenol should be more favorable at pH value less than 9. The composites capsules would be a kind of promising alternative adsorbent with high adsorption capacity for the phenol from aqueous solutions at a low concentration. The adsorption kinetics of the capsules for phenol accorded with pseudo‐second‐order model, and the best fits of adsorption isotherms followed the Freundlich equation. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers