Adsorption characteristics of natural zeolites as solid adsorbents for phenol removal from aqueous solutions: Kinetics, mechanism, and thermodynamics studies

In this study, the adsorption kinetic, equilibrium and thermodynamic parameters of phenol from aqueous solutions by nano-size hydroxyapatite (n-HAp) powders were investigated at various temperatures and concentrations. The first-order kinetic model, pseudo-second-order kinetic model and intraparticle diffusion model were used to describe the kinetic data, and the data constants were evaluated. The results showed that the pseudo-second-order model was the best choice among the three kinetic models to describe the adsorption behavior of phenol onto n-HAp powders, suggesting that the adsorption mechanism might be a physisorption process. Adsorption isotherms and equilibrium adsorption capacities were determined by the fittings of the experimental data to the well-known Freundlich and Langmuir adsorption models. It was found that the Freundlich isotherm model provided the better correlation for phenol adsorption onto HAp nanopowders. The equilibrium constants were used to calculate the thermodynamic parameters, such as the change of Gibbs free energy (DeltadegGdeg), enthalpy (DeltaHdeg) and entropy (DeltaSdeg). The thermodynamic parameters suggested that the adsorption of phenol onto n-HAp was physisorption, spontaneous and endothermic in nature.

Phenol removal from aqueous phase by adsorption on activated carbon prepared from paper mill sludge

Soluble starch-functionalized graphene oxide composite (GO-starch) was prepared by a facile esterification reaction. And the composite was used as a novel adsorbent for the removal of Cd(II) from aqueous solution. The chemical composition and morphology of the GO-starch was investigated by fourier transform infrared spectroscopy, scanning electron microscopy and Raman spectroscopy. To evaluate the effects of the adsorption of Cd(II) by GO-starch, batch adsorption studies were performed to optimize the major parameters such as contact time, pH, initial concentration and temperature. The maximum uptake capacity of Cd(II) was 43.20 mg/g under the optimal conditions. Furthermore, the adsorption kinetics, isotherms and thermodynamics of Cd(II) on GO-starch were also investigated. The experimental data indicated that the adsorption kinetics and adsorption isotherms of Cd(II) on GO-starch were well fitted by pseudo-second-order kinetic model and Langmuir isotherm model, respectively. The adsorption thermodynamic parameters were calculated as ΔG 0 < 0, ΔH 0 > 0 and ΔS 0 > 0, respectively. The thermodynamic parameters indicated that the adsorption process was endothermic, feasible and spontaneous. Due to its high adsorption capacity for Cd(II), the GO-starch might have considerable potential for the aqueous removal of metal ions. Soluble starch-functionalized graphene oxide composite (GO-starch) was prepared and used as a novel adsorbent for the aqueous removal of Cd(II). The chemical composition and morphology of the GO-starch was characterized by fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Raman spectroscopy. Batch adsorption experiments were performed to optimize the major parameters such as contact time, pH, initial concentration and temperature. The maximum uptake capacity of Cd(II) was 43.20 mg/g under the optimal conditions. The adsorption kinetics and adsorption isotherms were well fitted by pseudo-second-order kinetic model and Langmuir isotherm model, respectively. The adsorption thermodynamic parameters were ΔG 0 < 0, ΔH 0 > 0 and ΔS 0 > 0, indicating that the Cd(II) adsorption process was spontaneous, endothermic and feasible.

Biodegradation of phenol by Pseudomonas putida (NICM 2174), a potential biodegradent of phenol has been investigated for its degrading potential under different conditions. Pseudomonas putida (NICM 2174) cells immobilized in chitosan were used to degrade phenol. Adsorption of phenol by the chitosan immobilized matrix played an important role in reducing the toxicity of phenol. In the present work, results of the batch equilibrium adsorption of phenol on chitosan from its aqueous solution at different particle sizes (0.177 mm, 0.384 mm, 1.651 mm) and initial concentration of phenol (20, 40, 60, 80, 100, 120, 140, 160, 180, 200 mg/l) have been reported. The adsorption isotherms are described by Langmuir, Freundlich and Redlich-Peterson types of equations. These indicate favourable adsorption with chitosan. From the adsorption isotherms, the adsorption capacity, energy of adsorption, number of layers and the rate constants were evaluated. In batch kinetic studies the factors affecting the rate of biodegradation of phenol, were initial phenol concentration (0.100 g/l, 0.200 g/l, 0.300 g/l), temperature (30 °C, 34 °C, 38 °C) and pH (7.0, 8.0, 9.0). Biodegradation kinetic data indicated the applicability of Lagergren equation. The process followed first order rate kinetics. The biodegradation data generally fit the Lagergren equation and the intraparticle diffusion rate equation from which adsorption rate constants, diffusion rate constants and diffusion coefficients were determined. Intraparticle diffusion was found to be the rate-limiting step. Cell growth contributed significantly to phenol removal rates especially when the degradation medium was supplemented with a utilizable carbon source.

Adsorption of phenols on reduced-charge montmorillonites modified by bispyridinium dibromides: Mechanism, kinetics and thermodynamics studies

Adsorption of phenol, bisphenol A and nonylphenol ethoxylates onto hypercrosslinked and aminated adsorbents

Characterization of the pristine barite mineral was established using a scanning electron microscope (SEM) and Fourier Transform Infra-Red (FTIR). Barite was applied for sodium oleate and sodium palmitate adsorption in aqueous solutions. Equilibrium adsorption data were fitted into two adsorption isotherms, three kinetic models and thermodynamic study. The concentration of the ion and pH in the solution proved to be a controlling factor in the adsorption process. Sodium oleate and sodium palmitate soaps adsorbed strongly onto the barite mineral at pH 9 and a temperature of 293k. They result was affected by the high bulk density and chemical resistance nature of barite indicated by successive increase in dosage amount. The effect of concentration and time typically gave a C-type adsorption isotherm. Adsorptive isotherm showed that sodium palmitate adsorption over natural barite was better described by the Langmuir adsorption isotherm while oleate desorption gave a good fitting with Freundlich isotherm. The adsorptive kinetics of sodium palmitate fitted well into pseudo 1 st order and 2nd order kinetics. Intra particle diffusion was not the rate-determining step. Thermodynamic study showed a physio-sorption that was exothermic. Hence the findings showed that pristine barite absorbs at optimum pH and temperature of 9 and 293K.

Adsorption of phenols by magnetic polysulfone microcapsules containing tributyl phosphate

In the present study, methylene blue (MB) removal has been studied from its aqueous solution, using Ficcus palmata leaves (FPL)-based plant material. The effect of different parameters such as contact time (10-100) minutes, initial concentration (5-25) mg/L, pH (4-13), temperature (298-318K), and adsorbent dosage (0.15-0.45g/0.05L) was investigated. The maximum removal efficiency was calculated to be 98% for sample having initial concentration 15mg/L along with 0.45g of adsorbent agitated for 80min at 318K and pH=7. The data were fitted to adsorption isotherm models (Langmuir and Freundlich) and kinetic models (pseudo-first order, pseudo-second order, and intra-particle diffusion). The data were found to be best fitted with Freundlich adsorption isotherm (R2 =0.99) and pseudo-second-order (R2 =0.991). Thermodynamic parameters (free energy change, enthalpy change, and entropy change) were also estimated. The Gibbs free energy values were found to be -1.808, -5.139, and -5.991kJ/mol at 298, 308, and 318K, respectively. The decrease in free energy with increasing temperature has indicated spontaneity of adsorption process, and positive enthalpy change (35.75kJ/mol) showed that the adsorption process was endothermic. 0.1M HCl was found to be most effective desorbing agent with percent desorption 53.51%. PRACTITIONER POINTS: FP leaves are low cost and easily available biomass for removal of MB from aqueous solution. The adsorption capacity was obtained to be 6.89mg/g at (15mg/g dye concentration, pH=7, and contact time 80min). The maximum removal efficiency for MB was 98%. The thermodynamic studies indicated the endothermic adsorption process. The 0.1M HCl was found as best desorbing agent for MB loaded on FP leaves.

Study of adsorption kinetic, mechanism, isotherm, thermodynamic, and design models for Cu(II) ions on sulfuric acid-modified Eucalyptus seeds: temperature effect

Pyrolyzed mesoporous activated carbon preparation from natural rubber common effluent biosludge: Characterization, isotherms, kinetics, thermodynamics, and ANN modeling during phenol adsorption

In this study, the adsorption performance of powdered activated carbon (PAC) on phenol was investigated in aqueous solutions. Batch adsorption studies were performed to evaluate the effects of various experimental parameters like PAC type, PAC dose, initial solution pH, temperature and pre-oxidation on the adsorption of phenol by PAC and establish the adsorption kinetics, thermodynamics and isothermal models. The results indicated that PAC adsorption is an effective method to remove phenol from water, and the effects of all the five factors on adsorption of phenol were significant. The adsorption rate of phenol by PAC was rapid, and more than 80% phenol could be absorbed by PAC within the initial 10 min. The adsorption process can be well described by pseudo-second-order adsorption kinetic model with rate constant amounted to 0.0313, 0.0305 and 0.0241 mg·μg−1·min−1 with coal, coconut shell and bamboo charcoal. The equilibrium data of phenol absorbed onto PAC were analyzed by Langmuir, Freundlich and Tempkin adsorption isotherms and Freundlich adsorption isotherm model gave the best correlation with the experimental data. Thermodynamic parameters such as the standard Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) obtained in this study indicated that the adsorption of phenol by PAC is spontaneous, exothermic and entropy decreasing.

The highly efficient removal of tetracycline (TC) from an aqueous solution was accomplished by using the raw shrimp shell waste (SSW) as an environmentally friendly adsorbent. The SSW without any treatment removed TC more efficiently than the SSW after being treated with HCl and NaOH solutions. The SSW was characterized using nitrogen adsorption–desorption isotherms, scanning electron microscopy alongside energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, a thermogravimetric-derivative thermogravimetry analyzer, and a ζ-potential analyzer. The maximum adsorption capacity of 400 mg/L SSW was 229.98 mg/g for 36 h at 55 °C. Both the Langmuir isotherm model and the pseudo-second-order kinetic model well described the experimental data. According to the values of the Gibbs free energy and enthalpy changes, the TC adsorption by SSW proved to be spontaneous and endothermic. The TC adsorption process was controlled by intraparticle diffusion and liquid film diffusion.

The adsorption of pentachlorophenol (PCP) from aqueous solutions using pristine multi-walled carbon nanotubes (MWCNTs) was studied kinetically and thermodynamically. The results showed that MWCNTs are good adsorbents for the elimination of PCP from aqueous solutions in a very short time compared with activated charcoal. The kinetics study showed that the adsorption of PCP is mainly due to the diffusion of PCP from the aqueous phase to the solid phase beside intra-particle diffusion. This intra-particle diffusion was more significant for activated charcoal compared with MWCNTs. The equilibrium adsorption of PCP at different temperatures was studied, and the adsorption isotherms were well described using different adsorption models. Thermodynamics study showed that the adsorption process was product-favored (enhanced) as the temperature decreased.

The adsorption of copper ions onto the surface modified Strychnos potatorum seeds (SMSP) in a batch adsorption system has been studied. Kinetics, mechanism, isotherm, and thermodynamic parameters have been estimated. Adsorption kinetics of copper ions onto the SMSP follows a pseudo‐second order kinetic model. Adsorption mechanism was explained with the intraparticle diffusion model, Boyd kinetic model (BKM), and Shrinking core model (SCM). Adsorption process was found to be controlled by both intraparticle diffusion and film diffusion. The diffusivity values were estimated from the BKM and SCM. Adsorption isotherm data agreed well with the Freundlich adsorption isotherm model, which indicates the multilayer adsorption of copper ions onto the SMSP. The maximum monolayer adsorption capacity of the SMSP was found to be 248 mg of copper ions/g of SMSP. Adsorption thermodynamic studies show that the adsorption of copper ions onto the SMSP was spontaneous and exothermic in nature. © 2012 American Institute of Chemical Engineers Environ Prog, 33: 28–37, 2014