Temperature effected sorption of europium(III) onto 1-(2-pyridylazo)-2-naphthol impregnated polyurethane foam

Summary The sorption of Eu(III) ions onto PAN loaded PUF has been optimized and investigated under the influence of various temperatures, i.e., 303, 313 and 323 K. Maximum retention (>96%) of Eu(III) ions (1.79^. 10^-5M) onto PAN loaded PUF (7.75 mg^. ml^-1) was achieved after 30-minute equilibration time from pH 7 buffer solution. The variation of sorption with temperature yields the thermodynamic parameters ΔH=79±2 kJ^. mol^-1, ΔS=276±7 kJ^. mol^-1. K^-1and ΔG=-1.4±0.1 kJ^. mol^-1at 298 K. The positive value of enthalpy and negative free energy show endothermic and spontaneous nature of sorption, respectively. The sorption data followed Freundlich, Dubinin-Radushkevich (D-R) and Langmuir isotherms at all the three given temperatures. The Freundlich constant 1/n=0.70, 0.62 and 0.55 and sorption capacities C_m=10.8 mmol^. g^-1, 6.1 mmol^. g^-1and 4.4 mmol^. g^-1, respectively, decreased with increasing temperature. Similarly, the sorption capacities of D-R isotherm X_m=197.6 μmol^. g^-1, 201.2 μmol^. g^-1and 137.4 μmol^. g^-1, also decreased with temperature. However, the sorption free energy E=10.2 kJ^. mol^-1, 11.2 kJ^. mol^-1and 12.7 kJ^. mol^-1, increased with temperature. The monolayer coverage (Q) computed from Langmuir isotherm was 11.1±0.6 μmol^. g^-1and remains constant at all the three temperatures investigated. However, the binding energy constant bincreased with temperature. The relationship of bwith temperature and differential heat of adsorption (ΔH_diff) have been evaluated and discussed.     

Sorption and thermodynamic behavior of zinc(II)-thiocyanate complexes onto polyurethane foam from acidic solutions

The uptake of Zn(II)-SCN complex onto polyurethane foam (PUF) has been investigated in detail with respect to different composition and variable concentration of electrolyte, zinc, thiocyanate ions and PUF, and equilibration time. The sorption data followed both Langmuir and Dubinin-Radushkevich (D-R) sorption isotherms over the entire concentration range of zinc investigated whereas Freundlich sorption isotherm is obeyed upto 13.6^.10^-3M concentration. The Langmuir constants Q = 202±7 mmole^.g^-1 and of b = (1.78±0.31.10⁴ dm^3.mole^-1 and of D-R paraneter X _m = 493±1 mmole^.g^-1, b = activity coefficient = -0.028±0.0002 and of sorption energy E = 13.2±0.5 kJ^.mole^-1 and Freundlich constants 1/n = 0.42±0.03 and c _m = 6.47±1.7 mmole^.g^-1 were evaluated. The influence of temperature variation on sorption have yielded DH = -77.5±2.9 kJ^.mole^-1, DS = -5±0.09 J^.mole^-1.K^-1 and DG = -6.67±0.05 kJ^.mole^-1. The effect of common anions and cations on the sorption has been examined. Sulphate, ascorbate and bromide ions enhances the sorption to some extent whereas nitrite, Pb(II), Fe(III), Al(III), Cu(II) and Co(II) decrease to sorption significantly. A possible mechanism has been envisaged for Zn(II)-SCN sorption onto PUF.     

Uptake of Tm(III) ions onto polyurethane foam from H2O - ethanol mixture containing 1-(2-pyridylazo)-2-naphthol (PAN)

Summary The sorption of microquantities of Tm(III) ions on washed polyurethane foam (PUF) from a mixture of aqueous solution and ethanol containing PAN was examined. The maximum sorption of 3.18^. 10^-6M solution of Tm(III) ions was observed at pH 8 with 30-minute equilibration time. The optimum ratio of aqueous-ethanol phase for the sorption of Tm(III) ions was found to be 3:1 v/v, respectively. The sorption rate of metal ions on PUF is followed a first order kinetics and obeyed the equation for an intra particle diffusion process. The equilibrium concentration data of Tm(III) ions could be described satisfactorily by several adsorption isotherms. The Freundlich adsorption isotherm constants 1/nand K_Fare 0.66±0.02 and (5.7±0.3)^. 10^-3mol^. g^-1, respectively. The Langmuir isotherm constants for monolayer coverage (Q) and binding strength of sorption (b) are (2.5±0.7)^. 10^-5mol^. g^-1and (1.6±0.1)^. 10⁴l^. mol^-1, respectively. The sorption capacity derived from Dubinin-Radushkevich (D-R) isotherm is (1.7±0.2)^. 10^-4mol^. g^-1and the sorption free energy (E) is 9.8±0.2 kJ^. mol^-1indicating chemisorption phenomena. The thermodynamic parameters indicate that the sorption of Tm(III) ions onto PUF is endothermic, entropy driven and spontaneous in nature.     

Adsorption modeling of antimony(V) on diphenylthiocarbazone loaded polyurethane foam

The uptake behavior of Sb(V) onto diphenylthiocarbazone (H2DZ) loaded polyurethane foam (PUF) from aqueous solutions of different acids in the presence of KI have been studied. The maximum adsorption was found from 0.5N HNO₃ containing 0.2M KI. The maximum equilibrium was achieved within twenty minutes shaking time. The sorption behavior followed the Freundlich and Langmuir adsorption isotherms. The Freundlich constants 1/n and K_f are 0.57 and 3.26^.10^-2 mol^.g^-1, respectively. The Langmuir constants M and b are 2.18^.10^-4 mol^.g^-1 and 2.4^.10⁴ l^.g^-1, respectively. The value of sorption free energy (E) evaluated from D-R isotherm is 10.8 kJ^.mol^-1 indicating the ion exchange type chemisorption of Sb(V) on H2DZ loaded PUF. The thermodynamic parameters of enthalpy (H), entropy (S) and Gibbs free energy (G) have also been investigated and found to be -51.8 kJ^.mol^-1, -127.3 J^.mol^-1.deg^-1 and -13.8 kJ^.mol^-1, respectively. The negative values of (H) and (G) indicate that the sorption is exothermic and spontaneous in nature. The effect of anions and cations and sorption mechanism are discussed.     

Kinetic and thermodynamic parameters of 99Mo sorption on thermally treated hydrotalcite

Summary Thermally treated hydrotalcite was synthesized and its ability to sorb ⁹⁹Mo from aqueous solutions was studied under static conditions as a function of initial concentration, amount of sorbent and pH. X-ray diffraction was used to characterize synthesized calcined hydrotalcite. The values of sorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) sorption isotherms. The mean energy of sorption was calculated as 5.24 kJ^. mol^-1from D-R sorption isotherm. The Lagergren equation has been used for the study of the kinetic process. The rate constants of ⁹⁹Mo sorption on calcined hydrotalcite were calculated at various temperatures (293-323 K). The thermodynamic constans have been calculated and the standard enthalpy of the system was found to be<span style='font-size:12.0pt; font-family:Symbol;mso-bidi-font-family:Symbol'>DH°=11.5±0.3 kJ^. mol^-1. The values of calculated<span style='font-size:12.0pt;font-family:Symbol;mso-bidi-font-family: Symbol'>DG° and<span style='font-size:12.0pt;font-family: Symbol;mso-bidi-font-family:Symbol'>DS° were</o:p>-13.9±2.0 kJ^. mol^-1and (8.7±0.2)^. 10^-2kJ^. K^-1. mol^-1, respectively. These results show that the sorption process is endothermic, spontaneous in nature and the degree of freedom of ions is increased by sorption.     

Evaluation of sorption affinity of cadmium(II) on Haro river sand from aqueous solutions

The sorption of Cd(II) on Haro river sand from deionized water is reported. The sorption system obeyed according to the Freundlich and Dubinin–Radushkevich (D-R) isotherms. The Freundlich parameters 1/n = 0.67±0.05 and of A = 1.38±1.14 mmole·g^-1 have been ascertained. D-R isotherm yields the values of = -0.003741±0.000321 kJ²·mole^-2, X _m = 0.23±0.21 mole·g^-1 and of E = 11.6±0.5 kJ·mole^-1. The influence of common anions and cations on the sorption was examined. Trivalent Bi enhances the sorption whereas Fe, Cr, Al and chromate ions reduce the sorption significantly. Hf(IV) and Ag(I) indicate substantial sorption (61–98%) whereas Gd(III), Re(VII) and Sc(III) show low sorption (<5%). The elements having low sorption can be separated from elements indicating higher sorption using Haro river sand column.     

Removal of Zn(II) Ions from Aqueous Solution Using BPHA‐Impregnated Polyurethane Foam

Zn(II) ions sorption onto N‐Benzoyl‐N‐Phenylhydroxylamine (BPHA) impregnated polyurethane foam (PUF) has been studied extensively using radiotracer and batch techniques. Maximum sorption (～98%) of Zn(II) ions (8.9 × 10^?6 M) onto sorbent surface is achieved from a buffer of pH 8 solution in 30 minutes using 7.5 mg/mL of BPHA‐impregnated polyurethane foam at 283 K. The sorption data follow Langmuir, Freundlich and Dubinin‐Radushkevich (D‐R) isotherms. The Langmuir constants Q = 18.01 ± 0.38 μ mole g^?1 and b = (5.39 ± 0.98) × 10³ L mole^?1 have been computed. Freundlich constants 1/n = 0.29 ± 0.01 and C_m = 111.22 ± 12.3 μ mole g^?1 have been estimated. Sorption capacity 31.42 ± 1.62 μ mole g^?1, β = ?0.00269 ± 0.00012 kJ² mole^?2 and energy 13.34 ± 0.03 kJ mole^?1 have been evaluated using D‐R isotherm. The variation of sorption with temperature yields ΔH = ?77.7 ± 2.8 k J mole^?1, ΔS = ?237.7 ± 9.3 J mole^?1 K^?1 and ΔG = ?661.8 ± 117.5 k J mol^?1 at 298 K reflecting the exothermic and spontaneous nature of sorption. Cations like Fe(III), Ce(III), Al(III), Pb(II) and Hg(II) and anions, i.e., oxalate, EDTA and tartrate, reduce the sorption significantly, while iodide and thiocyanate enhanced the sorption of Zn(II) ions onto BPHA‐impregnated polyurethane foam.     

Retention, kinetics and thermodynamics profile of cadmium adsorption from iodide medium onto polyurethane foam and its separation from zinc bulk

The sorption behaviour of 2.5 × 10⁻⁵ M solution of Cd(II) on polyurethane foam (PUF) from iodide medium have been investigated. The conditions were optimized from aqueous solutions of different pH (1-10) and of acids of varied concentration (0.01-1.0 M). The maximum concentration of KI was found to be 0.24 M and equilibration time was established to be 20 min. The data successfully followed the Freundlich and Dubinin-Radushkevich (D-R) isotherms at low metal ion concentration while Langmuir isotherm followed at higher metal ion concentration. The Freundlich parameter 1/n = 0.66 ± 0.02 have been evaluated whereas D-R isotherm yields the sorption free energy E = 10.5 ± 0.1 kJ mol⁻¹ indicating ion exchange type chemisorption. The monolayer coverage (XL) constant of Langmuir isotherm was found to be 23.7 ± 0.4 mg g⁻¹. The numerical values of thermodynamics parameters enthalpy (ΔH), entropy (ΔS) and Gibbs free energy (ΔG) indicated the endothermic and spontaneous nature of sorption. The Scatchard plot analysis was tested to evaluate the binding sites of the PUF and stability constants of sorption were determined. On the basis of these parameters, the sorption mechanism was discussed. Among the foreign ions tested, Pb(II), Hg(II), cyanide and nitrite should be absent. The clean separation of Cd(II) from Zn(II) ions in the ratio 1:250, respectively, was achieved by column chromatography.     

Sorption behavior of Sn(II) onto Haro river sand from aqueous acidic solutions

The sorption behavior of Sn(II) onto Haro river sand has been examined with respect to nature of electrolyte, agitation time, dosage of sorbent and concentration of sorbate. Maximum sorption (95.5%) has been achieved from 0.034M hydrochloric acid solution after equilibrating sorbate (2·10⁻⁵M) and sorbent (50 mg) for 120 minutes at aV/W ratio of 90 cm³·g⁻¹. The kinetic data have been subjected to Morris-Weber and Lagergren equations. The kinetics of sorption proceeds a two stage process consisting of a relatively slow initial uptake followed by a much rapid increase in the sorption. The rate constant of intraparticle transport, K_d, comes out to be 8.75·10⁻⁸ mol·g⁻¹·min^−1/2 and the first order rate constant for sorption is 0.0416 min⁻¹. The sorption data of Sn(II) onto Haro river sand followed Langmuir, Freundlich and Dubinin-Radushkevich (D-R) type isotherms. The Langmuir constant,Q, related to sorption capacity and,b, related to sorption energy are computed to be 10.6±1.1 μmol·g⁻¹ and 1123±137 dm³·mol⁻¹, respectively. The D-R isotherm yields the values ofC _m=348±151 μmol·g⁻¹ and β=−0.01044±0.0008 mol²·kJ⁻² and ofE=6.9±0.3 kJ·mol⁻¹. In all three isotherms correlation factor (γ) is ≥0.99. The influence of common anions and cations on the sorption has been investigated. Zn(II), Mg(II), oxalate, Pb(II), Mn(II) and tartrate reduce the sorption significantly whereas Fe(II) causes substantial increase in the sorption. It is essential that all ions causing a decrease in the sorption of Sn(II) must be absent from the sorptive solution otherwise low sorption yields would result.     

Sorptive potential of sunflower stem for Cr(III) ions from aqueous solutions and its kinetic and thermodynamic profile

The sorptive potential of sunflower stem (180-300 μm) for Cr(III) ions has been investigated in detail. The maximum sorption (≥85%) of Cr(III) ions (70.2 μM) has been accomplished using 30 mg of high density sunflower stem in 10 min from 0.001 M nitric and 0.0001 M hydrochloric acid solutions. The accumulation of Cr(III) ions on the sorbent follows Dubinin-Radushkevich (D-R), Freundlich and Langmuir isotherms. The isotherm yields D-R saturation capacity X_m = 1.60 ± 0.23 mmol g⁻¹, β = −0.00654 ± 0.00017 kJ² mol⁻², mean free energy E = 8.74 ± 0.12 kJ mol⁻¹, Freundlich sorption capacity K_F = 0.24 ± 0.11 mol g⁻¹, 1/n = 0.90 ± 0.04 and of Langmuir constant K_L = 6800 ± 600 dm³ mol⁻¹ and C_m = 120 ± 18 μmol g⁻¹. The variation of sorption with temperature (283-323 K) gives ΔH = −23.3 ± 0.8 kJ mol⁻¹, ΔS = −64.0 ± 2.7 J mol⁻¹ K⁻¹ and ΔG_298k = −4.04 ± 0.09 kJ mol⁻¹. The negative enthalpy and free energy envisage exothermic and spontaneous nature of sorption, respectively. Bisulphate, Fe(III), molybdate, citrate, Fe(II), Y(III) suppress the sorption significantly. The selectivity studies indicate that Cr(III), Eu(III) and Tb(III) ions can be separated from Tc(VII) and I(I). Sunflower stem can be used for the preconcentration and removal of Cr(III) ions from aqueous medium. This cheaper and novel sorbent has potential applications in analytical and environmental chemistry, in water decontamination, industrial waste treatment and in pollution abatement. A possible mechanism of biosorption of Cr(III) ions onto the sunflower stem has been proposed.     

Sorption behavior of germanium(IV) on titanium dioxide nanoparticles

Titanium dioxide nanoparticles were employed for the sorption of Ge(IV) ions from aqueous solution. The process was studied in detail by varying the sorption time, pH, and temperature. The sorption process was found to be fast, equilibrium was reached within 3 min. A maximum sorption could be achieved from solution when the pH ranges between 4.0 and 11.0. Sorbed Ge(IV) ions can be completely desorbed with 2 mL of 0.3 mol L⁻¹ K₃PO₄-1.0 mol L⁻¹ H₂SO₄ mixture solution. The kinetic experimental data properly correlate with the second-order kinetic model (k ₂ = 0.88 g mg⁻¹ min⁻¹ (25°C)), Reichenberg equation and Morris-Weber model. The estimated E _a for Ge(IV) adsorption on nano-TiO₂ was 19.66 kJ mol⁻¹. The overall rate process appears to be influenced by intra-particle diffusion. The sorption data could be well interpreted with the Langmuir and Dubinin-Radushkevich (D-R) type sorption isotherms. The D-R parameters were calculated to be K = −0.00321 mol₂ kJ⁻², q _m = 0.59 mmol g⁻¹ and E = 12.48 kJ mol⁻¹ at room temperature. Furthermore, the thermodynamic parameters were also determined, and the ΔH ⁰ and ΔG ⁰ values indicated a spontaneous exothermic behavior.     

Investigation of the Removal of Lead by Adsorption onto 1‐(2‐Thiazolylazo)‐2‐Naphthol (TAN) Imbedded Polyurethane Foam from Aqueous Solution

A new preconcentration method is presented for lead on TAN‐loaded polyurethane foam (PUF) and its measurement by differential pulse anodic stripping voltammetry (DPASV). The optimum sorption conditions of 1.29 × 10^?5 M solution of Pb(II) ions on TAN‐loaded PUF were investigated. The maximum sorption was observed at pH 7 with 20 minutes equilibrated time on 7.25 mg mL^?1 of TAN‐loaded foam. The kinetic study indicates that the overall sorption process was controlled by the intra‐particle diffusion process. The validity of Freundlich, Langmuir and Dubinin ‐ Radushkevich adsorption isotherms were tested. The Freundlich constants 1/n and K_F are evaluated to be 0.45 ±0.04 and (1.03 +0.61) × 10^?3 mol g^?1, respectively. The monolayer sorption capacity and adsorption constant related to the Langmuir isotherm are (1.38 ± 0.08) × 10^?5 mol g^?1 and (1.46 ± 0.27) × 10⁵ L mol^?1, respectively. The mean free energy of Pb(II) ions sorption on‐TAN loaded PUF is 11.04 ± 0.28 kJ mol^?1 indicating chemisorption phenomena. The effect of temperature on the sorption yields thermodynamics parameters of ΔH, ΔS and ΔG at 298 K that are 15.0 ± 1.4 kJ mol^?1, 74 ±5 J mol^?1 K^?1 and ‐7.37 ± 0.28 kJ mol^?1, respectively. The positive values of enthalpy (ΔH) and entropy (ΔS) indicate the endothermic sorption and stability of the sorbed complexes are entropy driven. However, the negative value of Gibb's free energy (ΔG) indicates the spontaneous nature of sorption. On the basis of these data, the sorption mechanism has been postulated. The effect of different foreign ions on the sorption and desorption studies were also carried out. The method was successfully applied for the determination of lead from different water samples at ng levels.     

Sorption of traces of silver ions onto polyurethane foam from acidic solution

The sorption of traces of silver ions onto polyurethane foam (PUF) has been investigated in detail. Maximum sorption of silver (K(d)=6109 cm(3) g(-1), %sorption>97.5%) has been achieved from 1 M nitric acid solution after equilibrating silver ions with approximately 29 mg PUF for 20 min. The kinetics and thermodynamics of the sorption of silver ions onto PUF have also been studied. The sorption of silver ions onto PUF follows a first-order rate equation, which results as 0.177 min(-1). The variation of sorption with temperature yields the values of DeltaH=-56.1+/-3.2 kJ mol(-1), DeltaS=-159.7+/-10.5 J mol(-1) K(-1) and DeltaG=-8.68+/-0.09 kJ mol(-1) at 298 K with a correlation factor gamma=0.9919. The sorption data were subjected to different sorption isotherms. The sorption follows Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The values of Langmuir isotherms Q=65.4+/-1.5 mumol g(-1) and b=(4.79+/-1.16)x10(4) dm(3) mol(-1) have been evaluated for Langmuir sorption constants, whereas the Freundlich sorption isotherm gives the value 1/n=0.12+/-0.02 and A=0.15+/-0.03 mmol g(-1). The D-R parameters computed were beta=-0.000817+/-0.000206 mol(2) kJ(-2), X(m)=76.8+/-8.7 mumol g(-1) and E=24.7+/-3.2 kJ mol(-1). The influence of common ions on the sorption was also examined. It is observed that Hg(II), thiourea, Al(III), thiocyanate and thiosulphate reduce the sorption, whereas Cu(II), citrate and acetate ions enhance the sorption significantly. It can be concluded that PUF may be used to remove traces of silver ions from its very dilute solutions or for its preconcentration from aqueous acidic solutions.     

Adsorption syntax of Au(III) on unloaded polyurethane foam

The nature of adsorption behavior of Au(III) on polyurethane (PUR) foam was studied in 0.2M HCl aqueous solution. The effect of shaking time and amount of adsorbent were optimized for 3.16·10⁻⁵M solution of Au(III) in 0.2M HCl. The classical Freundlich and Langmuir adsorption isotherms have been employed successfully. The Freundlich parameters 1/n and adsorption capacityK are 0.488±0.016 and (1.40±0.22)·10⁻² mol·g⁻¹, respectively. The Langmuir constants of saturation capacityM and binding energyb are (1.66±0.08)·10⁻⁴mol·g⁻¹ and 40294±2947 l·g⁻¹, respectively, indicating the monolayer chemical sorption. The mean free energy (E) of adsorption of Au(III) on PUR foam has been evaluated using D-R isotherm and found to be 11.5±0.16 kJ·mol⁻¹ reflecting the ion exchange type of chemical adsorption. The effect of temperature on the adsorption has also been studied. the isosteric heat of adsorption was found to be 44.03±1.66 kJ·mol⁻¹. The thermodynamic parameters of ΔG, ΔH, ΔS and equilibrium constantK _c have been calculated. The negative values of ΔG, ΔH and ΔS support that the adsorption of Au(III) on PUR foam is spontaneous, exothermic and of ion exchange chemisorption. The nature of the Au(III) species sorbed on PUR foam have been discussed.     

Modeling of iron adsorption on HTTA-loaded polyurethane foam using Freundlich,Langmuir and D-R isotherm expressions

The sorption of Fe(III) at low pH range from 1 to 4.5 on open cell polyether type HTTA-loaded polyurethane foam has been carried out using batch technique. The optimum shaking time for 2.5· 10^–4M solution of Fe(III) was found to be 30 minutes. The concept of macropore and micropore nature of polyurethane foam sorbent offers unique advantages of adsorption. Freundlich and Langmuir adsorption isotherms are followed at low concentration range from 1·10^–4 to 3·10^–4M solution of Fe(III). The Freundlich constant (1/n=0.46±0.013 andK=9.16±1.39 mg·g^–1) and Langmuir isotherm constants(M=21.78 mg·g^–1 andb=88.41±9.731·g^–1) were established. The sorption mean free energyE=12.22±0.09 kJ·mol^–1 and loading capacityC _m =145.21±6.1 mg·g^–1 were evaluated using Dubinin-Radushkevich isotherm, which suggested that the adsorption mechanism was chemisorption.     

Adsorption profile and thermodynamic parameters of the preconcentration of Eu(III) on 2-thenoyltrifluoroacetone loaded polyurethane (PUR) foam

The adsorption studies of Eu(III) was investigated on 2-thenoyltrifluoroacetone (HTTA) loaded PUR foam. The adsorption conditions were optimized with respect to pH, shaking time, loading capacity and adsorbent weight. The adsorption data followed the classical Freundlich and Langmuir type isotherms successfully. The Freundlich constant (1/n) is estimated to be 0.35±0.02, reflects a surface heterogeneity of the PUR foam. Langmuir isotherm gives a saturated capacity of 0.082±0.002 mmol^.g^-1 suggests a monolayer coverage of the surface. The Dubinin-Radushkevich (D-R) isotherm is applied and the sorption mean free energy (E) is calculated and found to be 13.36±0.12 kJ^.mol^-1 suggesting that chemisorption involving chemical bonding is responsible for the adsorption process. The thermodynamic parameters such as enthalpy (H), entropy (S) and Gibbs free energy (G) were calculated and interpreted. The positive value of H indicates that the adsorption of metal ions on HTTA-loaded PUR foam is an endothermic process. A possible explanation of this endothermicity has been given. The selectivity and sensitivity of the adsorbent was also studied. The sorption of Eu(III) is greatly affected in the presence of oxalate and fluoride. The sorptive affinity of different cations towards HTTA loaded PUR foam was also discussed.     

Thermodynamic parameters and sorption of U(VI) on ACSD

This paper discusses the sorption properties for U(VI) by alginate coated CaSO₄·2H₂O sepiolite and calcined diatomite earth (Kieselguhr) (ACSD). The removal of U(VI) from aqueous solution by sorption onto ACSF in a single component system with various contact times, pH, temperatures, and initial concentrations of U(VI) was investigated. The sorption patterns of uranium on the composite adsorbent followed the Langmuir, Freundlich and Dubinin-Radushkhevic (D-R) isotherms. The Freundlich, Langmuir, and D-R models have been applied and the data correlated well with Freundlich model and that the sorption was physical in nature (sorption energy, E _a = 17.05 kJ/mol). The thermodynamic parameters such as variation of enthalpy ΔH, variation of entropy ΔS and variation of Gibbs free energy ΔG were calculated from the slope and intercept of lnK ₀ vs. 1/T plots. Thermodynamic parameters (ΔH _ads = 31.83 kJ/mol, ΔS _ads = 167 J/mol·K, ΔG ^o _ads (293.15 K) = −17.94 kJ/mol) showed the endothermic heat of sorption and the feasibility of the process. The thermodynamics of U(VI) ion/ACSD system indicates the spontaneous and endothermic nature of the process. It was noted that an increase in temperature resulted in a higher uranium loading per unit weight of the adsorbent.     

Sorption studies of europium(III) on hydrous silica

Summary Sorption behavior of europium, Eu³⁺, on SiO₂ ^. xH₂O (silica gel) has been investigated as a function of time, the amount of silica gel, Eu³⁺ concentration, the ionic strength, and pH (in absence and in presence of carbonate). The sorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. The sorption capacity of silica gel was determined to be in the range of (2.62-8.00) ^. 10^-7 mol/g at pH 5.30±0.05 and 0.20M NaClO₄. The mean energy of sorption was calculated to be 13.50±0.05 kJ/mol from the D-R isotherm, suggesting the involvement of ion-exchange reactions in the sorption process. Sorption of Eu³⁺ decreased with increased ionic strength. A gradual decrease in pH with increased ionic strength supports the involvement of an ion-exchange mechanism in the sorption process. The diffusion coefficient of Eu³⁺ ion on silica gel was calculated as (3.98±0.12) ^. 10^-13 m^{2 .} s^-1 under the particle diffusion-controlled conditions.     

Adsorption of cesium on a composite inorganic exchanger zirconium phosphate - ammonium molybdophosphate

The applicability of zirconium phosphate-ammonium molybdophosphate (ZrP-AMP) for the efficient removal of cesium from aqueous acidic solutions by adsorption has been investigated. The adsorption data analysis was carried out using the Freundlich, Dubinin-Raduskevich (D-R) and Langmuir isotherms for the uptake of Cs in the initial concentration range of 3.75^.10^-5-7.52^.10^-3 mol^.dm^-3 on the ZrP-AMP exchanger from nitric acid medium. The mean free energy (E) values for the adsorption of Cs were obtained from the D-R isotherm. Equilibrium adsorption values at different temperatures have been utilized to evaluate the change in enthalpy, entropy and free energy (ΔH°, ΔS°, ΔG°). The adsorption of cesium on the ZrP-AMP exchanger was found to be endothermic. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermodynamics of the System HNO3-UO2(NO3)2-H2O at 298.15 K

The sorption of ⁶⁰Co, ⁶⁵Zn, ⁷⁵Se, ¹⁰³Pd, ¹¹⁰Ag and ²⁰³Hg radionuclides by polyurethane foam (PUF) was investigated and optimized with respect to the selection of appropriate sorptive medium, metal, thiocyanate ions (except for ¹¹⁰Ag) and PUF concentration and equilibration time. The influence of common anions and cations on the sorption of each metal was examined. The sorption data subjected to different sorption isotherms have shown that the sorption of all the radionuclides followed Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The sorption capacity intensity and energy were evaluated for each element studied. The variation of sorption with temperature was monitored for all radionuclides except zinc and selenium. The values of H, S and G were estimated and found to be negative indicating exothermic and spontaneous nature of sorption. It was found that PUF is an effective and economical sorbent for traces of metal ions which can be used for the separation/preconcentration of these ions from their very dilute solutions and has useful applications in radioanalytical and environmental chemistry and in radioactive and industrial liquid waste management.