In this study, poly(propylene carbonate) (PPC) and exfoliated graphite (PPC–EG) composites were prepared by the solution blending method and their selective extraction and detection of gold(III) were investigated. Specifically, a new effective adsorbent was developed for a selective extraction and determination of gold(III) by use of inductively coupled plasma optical emission spectrometry. The selectivity of PPC (PPC–EG 0.5, PPC–EG 1, PPC–EG 2, PPC–EG 3 and PPC–EG 5) was investigated toward several metal ions, including Au(III), Cd(II), Co(II), Cu(II), Hg(II), Pb(II), Pd(II) and Zn(II). Based on selectivity and pH studies, Au(III) was the most quantitatively adsorbed on PPC–EG 0.5 phase at pH 2, indicating that PPC–EG 0.5 was the most selective toward Au(III) among other metal ions. The adsorption isotherm followed the Langmuir model with adsorption capacity of 157.61 mg g⁻¹ of PPC–EG 0.5 for Au(III), which was in agreement with experimental data of adsorption isotherm study. The kinetic of adsorption for Au(III) was investigated by a pseudo-first- and second-order models. Results of kinetic models displayed that the adsorption of Au(III) on the PPC–EG 0.5 phase obeyed a pseudo-second-order kinetic model. In addition, results of thermodynamic investigation demonstrated that the adsorption mechanism of PPC–EG 0.5 toward Au(III) was a general spontaneous process and favourable.

In this study, an efficiently employed ionic liquid combined with commercially available silica gel (SG–ClPrNTf$_2$) was developed for selective detection of gold(III) by use of inductively coupled plasma–optical emission spectrometry (ICP-OES). The selectivity of SG–ClPrNTf$_2$ was evaluated towards seven metal ions, including Y(III), Mn(II), Zr(IV), Pb(II), Mg(II), Pd(II) and Au(III). Based on pH study and distribution coefficient values, the SG–ClPrNTf$_2$ phase was found to be the most selective towards Au(III) at pH 2 as compared to other metal ions. The adsorption isotherm of Au(III) on the SG–ClPrNTf$_2$ phase followed the Langmuir model with adsorption capacity of 59.48 mg g$^{−1}$, which was highly in agreement with experimental data of adsorption isotherm study. The kinetics study indicated that Au(III) adsorption kinetics data were well fit with the pseudo-second-order kinetic model on the basis of correlation coefficient fitting (0.996) and adsorption capacity agreement (62.26 mg g$^{−1}$). Furthermore, SG–ClPrNTf$_2$ phase was effectively performed for the determination of Au(III) in real water samples with satisfactory results.

The present study depicts the efficiency of cellulose acetate/manganese oxide thin films as adsorbents for selective extraction and detection of flavone in environmental waters. The selectivity of thin films (CA/Mn-1 and CA/Mn-2)was evaluated towards several organic compounds. Based on selectivity study results, CA/Mn-2 thin film was the most selective towards flavone among other compounds. In addition, the effect of other parameters such as contact time andinitial concentration of flavone was investigated to optimize adsorption conditions. The adsorption capacity of flavone was experimentally obtained as 57.96 mg g$^{−1}$ and theoretically calculated from Langmuir equation as 58.48 mg g$^{−1}$, which indicates the high agreement of the results. Moreover, data obtained from kinetic study suggested that the adsorption of flavone onto CA/Mn-1 phase followed a pseudo-second-order kinetic model. Finally, validation of this method has attained reasonable results for determination of flavone in real water samples.

This study describes an effective method developed for the removal of hexavalent chromium, Cr(VI), from anaqueous environment. In this study, the Ni–SiO$_2$ nanomaterial was synthesized by the sol–gelmethod and then characterizedby field emission scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy. The preparednanomaterial was then employed as an adsorbent with significant properties of high surface area and uptake capacity.Adsorption conditions of Cr(VI) onto the Ni–SiO$_2$ nanomaterial were optimized by altering different parameters (pH, initial Cr(VI) concentration and different periods of time). An amount of 100.75 mg g$^{−1}$ was estimated as the maximum uptakecapacity of the Ni–SiO$_2$ nanomaterial at pH 4.0. The experimental data of Cr(VI) adsorption onto the Ni–SiO2 nanomaterialwere fitted well to the Langmuir isotherm and pseudo second-order kinetic models.Moreover, the adsorption of Cr(VI) ontothe Ni–SiO$_2$ nanomaterial was not influenced even in the presence of different coexisting ions. Finally, the recommendedmethodology was applied on several environmental water samples.