Adsorption of phenol and p-chlorophenol from their single and bisolute aqueous solutions on Amberlite XAD-16 resin

Removal of phenol and p-chlorophenol from synthetic single and bisolute aqueous solutions at 303.15 K through adsorption on Amberlite XAD-16 resin under batch equilibrium and dynamic column experimental conditions was investigated. The equilibrium adsorption data from single component solutions were fitted to Langmuir and Freundlich adsorption isotherm models to evaluate the model parameters and the parameters in turn were used to predict the extent of adsorption from bisolute aqueous solutions using Ideal Solution Adsorption (IAS) model. The effect of pH on removal of phenol and p-chlorophenol from single and bisolute systems was studied. The breakthrough capacity and total capacity of the resin for the adsorbates at different concentrations were evaluated through column adsorption studies. Attempts were made to regenerate the resin by solvent washing using methanol as an eluent. The limited number of adsorption-desorption cycles indicated that the adsorption capacity of the resin remained unchanged.     

Adsorption of 4-chlorophenol from aqueous solutions by xad-4 resin: isotherm, kinetic, and thermodynamic analysis

Removal of 4-chlorophenol (4-CP) from synthetic aqueous solutions through adsorption on Amberlite XAD-4 resin, a non-ionic macroreticular resins, under batch equilibrium experimental conditions at 298, 308 and 318K was investigated. It is necessary to propose a suitable model to a better understanding on the mechanism of 4-CP adsorption. For this purpose, Langmiur, Freundlich, Toth, and Redlich-Peterson (RP) isotherm models were compared. The two and three parameters in the adopted adsorption isotherm models were determined by the help of MATLAB package program. It was determined that best fitted adsorption isotherm models were obtained to be in the order: Redlich-Peterson>Langmuir>Toth>Freundlich isotherms. The pseudo-second-order kinetic model provided the best correlation to the experimental results. Results of the intra-particle diffusion model show that the pore diffusion is not the only rate limiting step. The lower correlation of the data to the Bangham's equation also represents that the diffusion of the adsorbate into pores of the sorbent is not the only rate-controlling step. The thermodynamic constants of adsorption phenomena; DeltaG degrees, DeltaH degrees, and DeltaS degrees were found as -4.17 (at 298K) kJ/mol, -42.01 kJ/mol, and -0.127 kJ/(mol K), respectively. The results showed that adsorption of 4-CP on Amberlite XAD-4, a nonionic polymeric resin was exothermic and spontaneous.     

Removal of nickel from aqueous solution by the bacterium Bacillus thuringiensis

The biosorption of the toxic metal (nickel) from aqueous solutions on dried vegetative cell and spore-crystal mixture of Bacillus thuringiensis var. thuringiensis was tested under laboratory conditions as a function of pH, initial metal ion concentration and temperature. The characteristics of the adsorption process were investigated using Scatchard analysis. Scatchard analysis of the equilibrium binding data for metal ions on vegetative cell and spore-crystal mixture of B. thuringiensis gave rise to a linear plot, indicating that the Langmuir model could be applied successfully. Adsorption behaviour of nickel(II) ion on B. thuringiensis is expressed by both Langmuir and Freundlich isotherms. The adsorption data with respect to the metal provided an excellent fit to both isotherms. Ni(II) ion uptake of B. thuringiensis's spore-crystal mixture at 250 mg l(-1) was 15.7%, whereas its vegetative cell metal uptake was 10%. The best temperature for ion uptake was found to be at 35 degrees C.     

Adsorptive removal of Methylene blue and Methyl orange from aqueous media by carboxylated diaminoethane sporopollenin: on the usability of an aminocarboxilic acid functionality-bearing solid-stationary phase in column techniques

The adsorption phenomena of Methylene blue (MB) and Methyl orange (MO) on a carboxylated diaminoethane sporopollenin (CDAE-S) solid phase were investigated in a column arrangement by using breakthrough technique. The adsorption phenomena were evaluated using some common adsorption isotherm models and Scatchard plot analysis, and obtained results were interpreted for evaluating the usability of CDAE-S for removal, recovery and preconcentration of the studied dyes both at the laboratory and industrial scales. On the basis of Scatchard plot analysis, the interaction types between the CDAE-S and the studied dyes were criticized in terms of affinity phenomena. Thus, the usability of a biomacromolecule-derived material, CDAE-S, as a cheap, environmentally-friendly and effective solid-stationary phase exhibiting both cation-exchange and anion-exchange characteristics at the same time, is discussed through the present study. Besides, from the obtained results, the protonated CDAE-S, which functionally resembles an amino acid structure, are presented as a two-in-one solid-stationary phase, and its adaptability to common processes performed under column conditions is also drawn in detail.     

Synthesis of urea-modified MnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> for aromatic micro-pollutants adsorption from wastewater: Mechanism and modeling

Amine-terminated MnFe₂O₄, using urea solution (UMF-MNPs) fabricated by a combined ultrasonic/microwave technique, was characterized and applied as a magnetic adsorbent to remove catechol, phenol, and benzene micro-pollutants from wastewater solutions. The simultaneous effect of solution pH, TDS, micro-pollutants concentrations, UMF-MNPs dose, and temperature was investigated and optimized using D-optimal design in a batch experiment. The quadratic regression, as the best-structured simulated model, predicted the maximum adsorption rates at pH 6.0, TDS 1855 mg/l, UMF-MNPs dose of 0.73 g/l, and temperature 320 K for 50 mg/l micro-pollutant concentrations. Kinetic and isotherm models, through linear and nonlinear regression methods, reflected an excellent correlation (R ² ≈ 0.83 to 1) to simulate the adsorption data. The column breakthrough curves were tested using the equivalent length of the unused bed approach, which well fitted the Thomas model equation. The film diffusion, consequently with Lewis acid–base, is the major rate-controlling adsorption mechanism, and recovered by alkali ethanolic solution.     

Copper(II) and lead(II) removal from aqueous solution in fixed-bed columns by manganese oxide coated zeolite

The ability of manganese oxide coated zeolite (MOCZ) to adsorb copper and lead ions in single- (non-competitive) and binary- (competitive) component sorption systems was studied in fixed-bed column. The experiments were applied to quantify particle size, bed length, influent flow rate and influent metal concentration on breakthrough time during the removal of copper and lead ions from aqueous solutions using MOCZ column. Results of fixed-bed adsorption showed that the breakthrough time appeared to increase with increase of the bed length and decrease of influent metal concentration, but decreased with increase of the flow rate. The Thomas model was applied to adsorption of copper and lead ions at bed length, MOCZ particle size, different flow rate and different initial concentration to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design. The model was found suitable for describing the adsorption process of the dynamic behavior of the MOCZ column. The total adsorbed quantities, equilibrium uptakes and total removal percents of Cu(II) and Pb(II) related to the effluent volumes were determined by evaluating the breakthrough curves obtained at different conditions. The results suggested that MOCZ could be used as an adsorbent for an efficient removal of copper and lead ions from aqueous solution. The removal of metal ion was decreased when other additional heavy metal ion was added, but the total saturation capacity of MOCZ for copper and lead ions was not significantly decreased. This competitive adsorption also showed that adsorption of lead ions was decreased insignificantly when copper ions was added to the influent, whereas a dramatic decrease was observed on the adsorption of copper ions by the presence of lead ions. The removal of copper and lead ion by MOCZ columns followed the descending order: Pb(II) > Cu(II). The adsorbed copper and lead ions were easily desorbed from MOCZ with 0.5 mol l(-1) HNO3 solution.     

Treatment of high-strength phenolic wastewater by a new two-step method

Treatment of high-strength phenolic wastewater by a novel two-step method was investigated in the present study. The two-step treatment method consisted of chemical coagulation of the wastewater by metal chloride followed by further phenol reduction by resin adsorption. The present combined treatment was found to be highly efficient in removing the phenol concentration from the aqueous solution and was proved capable of lowering the initial phenol concentration from over 10,000 mg/l to below direct discharge level (1mg/l). In the experimental tests, appropriate conditions were identified for optimum treatment operation. Theoretical investigations were also performed for batch equilibrium adsorption and column adsorption of phenol by macroreticular resin. The empirical Freundlich isotherm was found to represent well the equilibrium phenol adsorption. The column model with appropriately identified model parameters could accurately predict the breakthrough times.     

Adsorption characteristics of aniline and 4-methylaniline onto bifunctional polymeric adsorbent modified by sulfonic groups

In this paper a new bifunctional polymeric resin (LS-2) was synthesized by introducing sulfonic groups onto the surface of the resin during the post-crossing of chloromethyl low crosslinking macroporous poly-styrene resin, and the comparison of the adsorption properties of LS-2 with Amberlite XAD-4 toward aniline and 4-methylaniline in aqueous solutions was made. The study focuses on the static equilibrium adsorption behaviors, the adsorption thermodynamics, and the column dynamic adsorption and desorption profiles. Freundlich model gives a perfect fitting to the isotherm data. Although the specific surface area of LS-2 is lower than that of Amberlite XAD-4, the adsorbing capacities for these two adsorbates on LS-2 are higher than those on Amberlite XAD-4 within the temperature range 288-318 K, which is contributed to microporous structure and the polar groups on the network of LS-2 resins. The adsorption for aniline or 4-methylaniline on LS-2 was proved to be an endothermic process and increasing temperature was favorable. From the studies on the adsorption thermodynamics, static equilibrium adsorption, and the desorption conditions, an important conclusion can be drawn that the adsorption for aniline or 4-methylaniline on the LS-2 is a coexistence process of physical adsorption and chemical transition.     

Removal of Pb(II) using the modified lawny grass: Mechanism,kinetics, equilibrium and thermodynamic studies

A series of new chemical-modified lawny grass adsorbents were prepared and the feasibility of absorbents to remove Pb(II) ion from aqueous solution was examined. The absorbents were characterized by FTIR spectra and elemental analysis. Kinetics, equilibrium, thermodynamics, column adsorption and mechanism were studied. The optimum pH is in the range of 5.0–5.8 for all adsorbents. The sorption system follows pseudo-second-order kinetic model and equilibrium time is obtained after 60 min. The maximum adsorption capacities obtained from Langmuir–Freundlich model are 1.55 and 1.26 mol/kg by using 1 CG and 0.6 CG (lawny grass modified by 1 mol/L or 0.6 mol/L citric acid, respectively). Thermodynamic parameters such as ΔG, ΔH and ΔS are evaluated for the adsorption process. The results indicates that the adsorption of Pb(II) is spontaneous and endothermic. The breakthrough point is achieved at 100 BV (bed volume) by a column of 0.6 CG. Desorption of Pb(II) and regeneration of the column is achieved by 0.1 mol/L HCl elution. After 3 adsorption/desorption cycles, the breakthrough point remains around 100 BV, which shows that grass adsorbent is regenerated easily and used repeatedly. Above results indicates that lawny grass have a good potential for removal of lead from dilute aqueous solution in the future.     

Studies on adsorptive removal of Co(II), Cr(III) and Ni(II) by IRN77 cation-exchange resin

The adsorption of cobalt, chromium and nickel from aqueous solutions on IRN77 cation-exchange resin has been studied comparatively. The percentage removal of cobalt, chromium and nickel was examined by varying experimental conditions, viz. dosage of adsorbent, pH of the solution and contact time. It was found that more than 95% removal was achieved under optimal conditions. The adsorption capacity (k) for cobalt, chromium and nickel were calculated from the Freundlich adsorption isotherm. The adsorption of cobalt, chromium and nickel on this cation-exchange resin followed the Lagergren kinetic model. Also the competitive adsorption of multi-metals onto the IRN77 resin was studied. The studies showed that this cation-exchange resin can be used as an efficient adsorbent material for the removal of cobalt, chromium and nickel from water and nuclear power plant coolant water.     

Adsorption of trichloroethylene and benzene vapors onto hypercrosslinked polymeric resin

In this research, the adsorption equilibria of trichloroethylene (TCE) and benzene vapors onto hypercrosslinked polymeric resin (NDA201) were investigated by the column adsorption method in the temperature range from 303 to 333 K and pressures up to 8 kPa for TCE, 12 kPa for benzene. The Toth and Dubinin–Astakov (D–A) equations were tested to correlate experimental isotherms, and the experimental data were found to fit well by them. The good fits and characteristic curves of D–A equation provided evidence that a pore-filling phenomenon was involved during the adsorption of TCE and benzene onto NDA-201. Moreover, thermodynamic properties such as the Henry's constant and the isosteric enthalpy of adsorption were calculated. The isosteric enthalpy curves varied with the surface loading for each adsorbate, indicating that the hypercrosslinked polymeric resin has an energetically heterogeneous surface. In addition, a simple mathematic model developed by Yoon and Nelson was applied to investigate the breakthrough behavior on a hypercrosslinked polymeric resin column at 303 K and the calculated breakthrough curves were in high agreement with corresponding experimental data.     

Arsenic removal from an aqueous solution by modified A. niger biomass: batch kinetic and isotherm studies

Batch studies were conducted to examine the adsorption kinetics and adsorption capacity of iron oxide-coated biomass (IOCB) for As(III) and As(V). The optimum pH for As(V) and As(III) removal was found to be 6. The equilibrium time for removal of arsenic was found to be approximately 7 h. The adsorption of As(V) on IOCB was rapid compared to that of As(III) adsorption. An increase in temperature (from 5 to 30 °C) was found to increase As(III) removal, whereas in the case of As(V), the removal increased with temperature from 5 to 10 °C, but remained relatively constant thereafter up to 30 °C. The pseudo-second order rate equation was found to describe better the kinetics of arsenic adsorption than other equations. The isotherm data for As(V) removal fitted better with the Langmuir equation compared with other tested models and the isotherm data for As(III) removal fitted better with Redlich–Peterson equation than other tested models. Iron oxide-coated fungal biomass (A. niger) was found to be efficient in removing arsenic from an aqueous solution.     

Methylene blue biosorption from aqueous solutions by yellow passion fruit waste

The yellow passion fruit (Passiflora edulis Sims. f. flavicarpa Degener) (YPFW) a powdered solid waste, was tested as biosorbent for the removal of a cationic dye, methylene blue (MB), from aqueous solutions. Adsorption of MB onto this low-cost natural adsorbent was studied by batch adsorption at 25 °C. The effects of shaking time, biosorbent dosage and pH on adsorption capacity were studied. In alkaline pH region the adsorption of MB was favorable. The contact time required to obtain the maximum adsorption was 48 h at 25 °C. Four kinetic models were tested, being the adsorption kinetics better fitted to pseudo-first order and ion exchange kinetic models. The ion exchange and pseudo-first order constant rates were 0.05594 and 0.05455 h⁻¹, respectively. The equilibrium data were fitted to Langmuir, Freundlich, Sips and Redlich–Peterson isotherm models. Taking into account the analysis of the normal distribution of the residuals (difference of q_measured − q_model), the data were best fitted to Sips isotherm model. The maximum amount of MB adsorbed on YPFW biosorbent was 44.70 mg g⁻¹.     

Structural and ionization effects on the adsorption behaviors of some anilinic compounds from aqueous solution onto high-area carbon-cloth

The adsorption of anilinic compounds; aniline, p-toluidine, 1-napthylamine and sodium salt of diphenylamine-4-sulfonic acid from solutions in H₂O, in 1 M H₂SO₄ or in 0.1 M NaOH onto activated carbon-cloth was studied by in situ UV spectroscopy. A specially designed adsorption cell was used for this purpose. The adsorption processes were found to follow first-order kinetics and the rate constants were determined. The pH at the point of zero charge of the carbon-cloth surface was measured as 7.4. The highest rates and extents of adsorption were observed from H₂O solutions for aniline, p-toluidine and 1-napthylamine and from solution in 1 M H₂SO₄ for the sodium salt of diphenylamine-4-sulfonic acid. The adsorption behaviors of these four anilinic compounds in the three solutions (in H₂O, in 0.1 M NaOH and in 1 M H₂SO₄) were explained in terms of electrostatic and dispersion interactions between carbon-cloth surface and the anilinic species. The adsorption isotherm data for the anilinic compounds were derived at 30 °C and treated according to Langmuir and Freundlich models. The Freundlich model was found to represent the experimental isotherm data better than Langmuir model.     

Application of an effective method in predicting breakthrough curves of fixed-bed adsorption onto resin adsorbent

Removal of many organic pollutants including phenolic compounds from industrial wastewater can always be achieved by fixed-bed adsorption onto the polymeric resin adsorbent, and the relevant breakthrough curves would provide much valuable information to help to design a fixed-bed adsorption process in field application. In the present study, a model developed based on the constant-pattern wave approach theory and the Freundlich model was adopted to describe the breakthrough curves of phenol and p-nitrophenol adsorption onto a macroreticular resin adsorbent NDA-100 from aqueous solution. Column experiments were performed at different conditions to verify the model and the results proved that the model would describe the breakthrough curves well. Effect of the operation parameters on breakthrough curves was also discussed to get helpful information in choosing the adsorption process.     

Removal of hexavalent chromium from aqueous solution using activated carbon prepared from walnut shell biomass through alkali impregnation processes

Walnut (Juglans regia) is a commonly used nutrient industrial crop but the shell of the walnut has no economic value. Hence to revamp the waste walnut shell biomass to useful product, activated carbon (AC) was prepared from J. regia shells by impregnating with NaOH. Different ACs were prepared by varying the impregnation ratio of char:NaOH as 1:1 (AC1), 1:3 (AC2), and 1:5 (AC3). The effect of impregnation ratios on the adsorptive properties of ACs for the adsorption of hexavalent chromium [Cr(VI)] was studied. The ACs were characterized by SEM, surface functionality, and zero point charge. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevitch isotherm were used to interpret the batch equilibrium data. The adsorption of Cr(VI) onto ACs followed Langmuir isotherm model. Kinetic data followed pseudo second-order rate equation. Intraparticle diffusion model and Boyd plot were used to study the mechanism of the adsorption reaction. The adsorption was both by film diffusion and intraparticle diffusion. The rate-controlling step was predicted as external mass transfer. Thermodynamic parameters were also estimated. Overall, AC with higher impregnation ratio (AC3) possessed better adsorption properties compared to AC2 and AC1.     

Equilibria and dynamics of liquid-phase trinitrotoluene adsorption on granular activated carbon: effect of temperature and pH

Environmental regulations for removal of trinitrotoluene (TNT) from wastewater have steadily become more stringent. This study focuses on the adsorption equilibrium, kinetics, and column dynamics of TNT on heterogeneous activated carbon. Adsorption equilibrium data obtained in terms of temperature (298.15, 313.15 and 323.15K) and pH (3, 8 and 10) were correlated by the Langmuir equation. In addition, the adsorption energy distribution functions which describe heterogeneous characteristics of porous solid sorbents were calculated by using the generalized nonlinear regularization method. Adsorption breakthrough curves were studied in activated column under various operating conditions such as temperature, pH, concentration, flow rate, and column length. We found that the effect of pH on adsorption breakthrough curves was considerably higher than other operating conditions. An adsorption model was formulated by employing the surface diffusion model inside the activated carbon particles. The model equation that was solved numerically by an orthogonal collocation method successfully simulated the adsorption breakthrough curves.     

Adsorption of hydrazoic acid from aqueous solution by macroreticular resin

Sodium azide is a key component in the automobile air bag. When dissolved in aqueous solution, it reacts rapidly with water to form hydrazoic acid which is a highly toxic chemical and is strongly regulated by government. In the present study, adsorption of hydrazoic acid from aqueous solution by macroreticular resin is investigated. This method can provides a convenient means for dealing with the toxic hydrazoic acid. Experimental tests of batch equilibrium adsorption and continuous column adsorption of hydrazoic acid were conducted and the test results were employed to establish adsorption isotherm and to evaluate the column adsorption efficiency. The test results revealed that the multilayer adsorption isotherms, like the modified Langmuir or Jossens model, are needed to adequately describe the hydrazoic acid adsorption equilibrium between the liquid and solid (resin) phases. In the column adsorption process, a theoretical model was adopted for representing the hydrazoic acid change in the aqueous solution exiting the column and the verified theoretical model significantly facilitates prediction of adsorption breakthroughs and column design. Regeneration of exhausted resin was investigated. Solution of 10% (w/w) NaCl was found to be a very efficient regenerant.     

Removal of lead (II) ions from synthetic and real effluents using immobilized Pinus sylvestris sawdust: adsorption on a fixed-bed column

The purpose of this work was to evaluate the potential of Pinus sylvestris sawdust, in a continuous flow removal of lead (II) ions from synthetic and industrial aqueous effluents. The kinetic parameters obtained in a batch process were used to scale-up the process on a mini-column and to choose the breakthrough model. The column experimental data concerning the volumes treated were correlated using the bed depth service time model. These experimental data closely fitted the bed depth service time model at 10% of the breakthrough curve. The results from the bed depth service time model on the mini-column were then used to design a pilot plant adsorption unit. The performance of the pilot plant column accurately agreed with that obtained from the mini-column. The experiments carried out in a dynamic reactor allowed to bring out the influence of various parameters on the efficiency of the P. sylvestris sawdust. In addition, the process was checked for the treatment of industrial aqueous effluents on a pilot plant scale and the results were in accordance with those obtained from synthetic effluents.     

Adsorption of Acid Blue 193 from aqueous solutions onto DEDMA-sepiolite

The adsorption of Acid Blue 193 (AB193) onto dodecylethyldimethylammonium (DEDMA)-sepiolite was investigated in aqueous solution in a batch system with respect to contact time, pH and temperature. The surface modification of DEDMA-sepiolite was examined by the FT-IR technique. The pseudo-first-order, pseudo-second-order kinetic models and the intraparticle diffusion model were used to describe the kinetic data and the rate constants were evaluated. The experimental data fitted very well with the pseudo-second-order kinetic model and also followed the simple external diffusion model up to initial 10 min and then by intraparticle diffusion model up to 75 min, whereas diffusion is not only the rate-controlling step. The adsorption capacities of natural sepiolite and DEDMA-sepiolite at pH 1.5 and 20 degrees C were (1.19 and 2.57) x 10(-4) mol g(-1), respectively. The above results indicate that DEDMA-sepiolite has around two times higher adsorption capacity than natural sepiolite. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were also determined. The Freundlich model agrees with experimental data well. The activation energy, change of Gibbs free energy, enthalpy and entropy of adsorption were also evaluated for the adsorption of AB193 onto DEDMA-sepiolite.