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A green and efficient dispersive liquid-liquid microextraction method based on a new deep eutectic solvent has been developed for the preconcentration and extraction of cobalt and nickel ions. The deep eutectic solvent is formed by mixing choline chloride (hydrogen bond acceptor) and 4-aminophenol (hydrogen bond donor). Then, it is used as a chelating agent as well as extraction solvent. Under the optimum experimental conditions, the linear ranges for Ni(II) and Co(II) were 0.80–50 and 0.50–50 µgL−1, respectively, by flame atomic absorption spectrometry. The obtained detection limits were 0.30 and 0.22 µg L−1 for Ni(II) and Co(II), respectively. ChCl: choline chloride; DES: deep eutectic solvent; DLLME: dispersive liquid-liquid microextraction; EF: enrichment factor; ER: extraction recovery; FAAS: flame atomic absorption spectrometry; LOD: limit of detection; LOQ: limit of quantification. [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]