In this article, Cr(OH) nanoparticle-modified cellulose nanocrystal (CNC) as a novel hybrid nanocomposite (Cr(OH)-NPs-CNC) was prepared by a simple procedure and used as a sorbent for adsorptive removal of methylene blue (MB) and malachite green (MG) from aqueous solution. Different kinetic models were tested, and the pseudo-second-order kinetic model was found more suitable for the MB and MG adsorption processes. The BET and Langmuir models were more suitable for the adsorption processes of MB and MG. Thermodynamic studies suggested that the adsorption of MB and MG onto Cr(OH)-NPs-CNC nanocomposite was a spontaneous and endothermic process. The maximum adsorption capacities for MB and MG were reached 106 and 104 mg/g, respectively, which were almost two times higher than unmodified CNC. The chemical stability and leaching tests of the Cr(OH)-NPs-CNC hybrid nanocomposite showed that only small amounts of chromium were leached into the solution.
A new approach was developed for sensitive determination of Fe(III) and Cu(II) ions using SnO 2 nanopowder in the micellar medium on the contrary conventional cloud point extraction studies. The presented method contains a combination of solid-phase extraction and cloud point extraction. According to this procedure, the metal ions were firstly retained on modified SnO 2 nanopowder and then passed to the surfactant-rich phase. The effect of experimental variables including pH, concentration of reagents, eluting solution, incubation time, equilibration temperature, sample volume, and effects of interfering ions have been investigated and optimized systematically. The calibration graphs were linear in the range of 0.23-100.00 μg L −1 and 0.30-110.00 μg L −1 for Fe(III) and Cu(II), respectively. Under optimized conditions, the limits of detections were 0.07 and 0.09 μg L −1 for Fe(III) and 0.09 μg L −1 for Cu(II). The proposed method offers satisfactory analytical features by means of combining two different and efficient preconcentration techniques. In addition, the method can be evaluated as an alternative and fast method according to only-surfactant-mediated extractions. The validation of method was carried out by recovery tests and certified reference material (CRM) analysis. The acceptable and compatible results were obtained in the analysis of CRM and real samples.
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