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The sorption behavior of 3.18×10 -6 mol l -1 solution of Tm(III) metal ions onto 7.25 mg l -1 of 1-(2-pyridylazo)-2-naphthol (PAN) loaded polyurethane foam (PUF) has been investigated at different temperatures i.e. 303 K, 313 K, and 323 K. The maximum equilibration time of sorption was 30 minutes from pH 7.5 buffer solution at all temperatures. The various rate parameters of adsorption process have been investigated. The diffusional activation energy (?E ads ) and activation entropy (?S ads ) of the system were found to be 22.1±2.6 kJ mol -1 and 52.7±6.2 J mol -1 K -1 , respectively. The thermodynamic parameters such as enthalpy (?H), entropy (?S), and Gibbs free energy (?G) were calculated and interpreted. The positive value of ?H and negative value of ?G indicate that sorption is endothermic and spontaneous in nature, respectively. The adsorption isotherms such as Freundlich, Langmuir, and Dubinin–Radushkevich isotherm were tested experimentally at different temperatures. The changes in adsorption isotherm constants were discussed. The binding energy constant (b) of Langmuir isotherm increases with temperature. The differential heat of adsorption (?H diff ), entropy of adsorption (?S diff ) and adsorption free energy (?G ads ) at 313 K were determined and found to be 38±2 kJ mol -1 , 249±3 J mol -1 K -1 and –40.1±1.1 kJ mol -1 , respectively. The stability of sorbed complex and mechanism involved in adsorption process has been discussed using different thermodynamic parameters and sorption free energy. [ABSTRACT FROM AUTHOR]

The sorption of iodine on polyurethane foam (PUF) has been investigated. The maximum sorption of 0.01 N of iodine solution on PUF was found to be >95% from 0.2 N HCl aqueous solution. The maximum equilibration was attained with 30 min agitation time. The iodine number was found to be 436±15 mg g-1. The average pore diameter of PUF was 8.3 nm and total surface area was 67 m2 g-1. The kinetic data indicates that the intraparticle diffusion rate of adsorption (Rd) and rate of mass action (k1) of iodine sorption on PUF were 0.48±0.03 mmole g-1 min-1/2 and 52±8 mmole g-1 min-1, respectively. The sorption data followed both Freundlich and Langmuir adsorption isotherms in the concentration range 0.03 N to 0.15 N of iodine. The Freundlich constants Cm=11.2±1.7 mmole g-1 and 1/n=0.57±0.05, and Langmuir constants M=4.9±0.6 mmole g-1 and b=12.9±1.3 L g-1 were established. The sorption free energy (E)=5.3±0.2 kJ mole-1 and loading capacity Xm=5.15±0.45 mmole g-1 were evaluated using D–R isotherm. The sorption energy reflects the physiosorption of iodine on PUF. The effect of temperature on the sorption yields the thermodynamic parameters ΔH=50±2 kJ mole-1 and ΔS=170±4 J mole-1 K-1. The Gibbs free energy (ΔG) ranges from 3.72 to -2.15 kJ mole-1, suggesting the endothermic nature of sorption of iodine, but is favorable at higher temperatures (>313K). The effect of different anions and cations on the sorption of iodine on PUF have been evaluated and discussed. [ABSTRACT FROM AUTHOR]

Sorption of cobalt(II)–thiocyanate complex onto polyurethane foam (PUF) has been investigated in detail with respect to the equilibrating time between Co(II)-thiocyanate complex in solution and foam, and concentrations of cobalt(II) and sorbent. The sorption was optimized with respect to the composition of electrolyte. Maximum sorption has been achieved from 0.1 M HCl solution containing 0.5 M SCN after 10 minutes of shaking time. The kinetics and thermodynamics of sorption are studied in detail. The kinetics follow a first-order rate equation with the rate constant, k, equal to 9.57 × 10-2 min.-1 The variation of equilibrium constant Kc with temperature (15–50°C) yields values of ΔH = -64 ± 4.6 kJ·mol-1, ΔS = -192.6 ± 15.6 J·mol-1·K-1, and ΔG = -8.71 kJ·mol-1 at 298 K. The sorption of Co(II)-thiocyanate onto PUF in the presence of common anions and cations has also been measured. The sorption data studied in the concentration range of Co(II) 1.12 × 10-4 to 1.20 × 10-3 M follow Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms. Freundlich parameters 1/n = 0.35 ± 0.02 and A = 0.85 ± 0.2 mmol·g-1, Langmuir constants Q = (5.54 ± 0.12) × 10-5 mol·g-1 and b = (3.55 ± 0.74) × 104 dm3·mol-1 and D–R isotherms β = -0.002999 ± 0.000189 kJ2·mol-2, Cm = 10.66 ± 0.16 × 10-4 mol·g-1 and E = 12.9 ± 0.4 kJ·mol-1 have been evaluated. The possible sorption mechanism of cobalt–thiocyanate complex onto PUF is also discussed. [ABSTRACT FROM AUTHOR]

Mercury sulfide was prepared and characterized by measuring average pore size and surface area. The sorption of mercury onto mercury sulfide was investigated in detail with respect to sorptive medium, agitation time, sorbent and sorbate concentration, and temperature. The maximum sorption of mercury (>99.8) was achieved from 10-3 M hydrochloric acid solution using 50 mg mercury sulfide for 10 minutes. The sorption data of mercury followed the Langmuir isotherm over the entire concentration of mercury investigated whereas the Freundlich and Dubinin–Radushkevich isotherms were obeyed only up to low and moderate concentrations. Useful parameters like sorption capacity and energy have been evaluated using these isotherms. The variation of the equilibrium constant with temperature has the results ΔH=23.8 ± 3.2 kJ·mol-1, ΔS = 130 ± 10 J·mol-1, and ΔG = -13.5 ± 0.4 kJ·mol-1 at 298 K. Among the ions tested, tartrate, fluoride, and citrate increase the sorption whereas Cu(II), Ba(II), Zn(II), Ni(II), Fe(II), and Cr(III) reduce the sorption significantly. Except for Y(III) (∼91%), all the metal ions showed a lower affinity toward HgS, especially trivalent Ho, Fe, Sc, Tm, Ga, Dy, As, and Pr which showed sorption >1 and >10%. The mercury sulfide column can be used to separate Hg(II) from these trivalent metal ions. [ABSTRACT FROM AUTHOR]