Ultrasound-assisted magnetic solid-phase extraction of polycyclic aromatic hydrocarbons and nitrated polycyclic aromatic hydrocarbons from water samples with a magnetic polyaniline modified graphene oxide nanocomposite.

A novel magnetic graphene oxide nanocomposite modified with polyaniline (Fe3O4@GO-PANI) was synthesized and applied for the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons (PAHs) (i.e. fluorene, phenanthrene and pyrene) and nitrated polycyclic aromatic hydrocarbons (N-PAHs) (i.e. 2-nitrofluorene, 9-nitroanthracene, 1-nitropyrene and 3-nitrofluoranthene) prior to their determination by gas chromatography-mass spectrometry. The prepared nanomaterial was characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform-infrared spectroscopy. The main experimental parameters affecting the extraction and desorption steps of the MSPE procedure were investigated and optimized. Under optimum conditions, coefficients of determination (r2) ranged between 0.9970 and 0.9995, limits of detection (LODs, S/N = 3) ranged between 0.04-0.05 ng mL-1 for PAHs and 0.01-0.11 ng mL-1 for N-PAHs, while the relative standard deviation for intra-day and inter-day repeatability were lower than 10.0% for PAHs and N-PAHs. The method was successfully applied to the analysis of tap, mineral and river water samples. Relative recoveries in spiked water samples ranged between from 91.6 to 114% and from 92.3 to 110% for PAHs and N-PAHs, respectively. The proposed method is simple, rapid, sensitive and the Fe3O4@GO-PANI sorbent can be reused for at least 15 times without significant decrease in extraction recovery.

Modeling the sorption of metal ions from aqueous solution by iron-based adsorbents.

The possibility of using iron-based adsorbents (i.e. akaganéite or goethite) to remove heavy metal ions from aqueous solutions was the aim of the present review paper. Synthesized material was used in two forms, i.e. in fine powder of nanocrystals and in the form of grains (as granular). The main examined parameters were the quantity of sorbent, the presence of ionic strength, the pH value of solution and the metals speciation, including the presence of complexing agents. The removal efficiency of the packed-bed column was examined and compared. Typical adsorption models were discussed and the bed depth-service time equation has been applied to the sorption results in order to model the column operation.

Removal of zinc ion from water by sorption onto iron-based nanoadsorbent.

Batch and column experiments were conducted to investigate zinc removal from dilute aqueous solution (i.e. effluent) by sorption onto synthetic nanocrystalline akaganéite. Due to favorite characteristics, this material was shown to be a promising inorganic adsorbent prepared in the laboratory, following a new method of synthesis-previously published. The effects of adsorbent amount, zinc concentration, solution pH value, ionic strength and temperature variation on the treatment process were mainly investigated during this study. Typical adsorption models were determined searching the mechanism of sorption while the bed depth-service time model was applied to column (with granular material) experiments.

Adsorptive removal of arsenites by a nanocrystalline hybrid surfactant-akaganeite sorbent.

Removal of toxic arsenite ions from aqueous solutions was investigated using an innovative hybrid nanocrystalline surfactant-modified akaganeite. This sorbent was prepared using ferric chloride as the precursor and a cationic surfactant, hexadecyltrimethylammonium bromide. From the experimental work, the material was found to be an effective adsorbent for the separation of arsenites. The chemical kinetics of the process was studied, described by a pseudo-second-order equation. The Freundlich adsorption isotherm was determined to examine the mechanism of sorption. FTIR measurements and XPS analysis gave useful information both on the sorbent synthesized and on the arsenite removal process.

Chromium(VI) sorptive removal from aqueous solutions by nanocrystalline akaganèite.

In this study, akaganeite (beta-FeO(OH)) an ironoxyhydroxide material, was used as a low-cost potential adsorbent for the removal of hexavalent chromium from aqueous solutions. The influence of agitation speed, solution pH, initial chromium concentration, sorbent concentration and temperature were evaluated at batch kinetic runs. It was shown that the solid diffusion model, in comparison to simple reaction kinetic models, described better the sorption kinetics. Freundlich and Frumkin isotherm best fitted the equilibrium results. Akaganeite presented a sorption capacity approximately 80 mg Cr(VI) g(-1), under the conditions studied. Flotation was used as a downstream process for the effective removal of the loaded material.

Sorption of As(V) ions by akaganéite-type nanocrystals.

A priority pollution problem, the removal of arsenate oxyanions from dilute aqueous solutions by sorption onto synthetic akaganéite (beta-FeO(OH)) was the aim of the present study. This is an innovative inorganic adsorbent material prepared in the laboratory, following a new method of preparation. The effect of akaganéite and arsenate concentration, the contact time, temperature, solution pH value, and ionic strength variation on the treatment process was mainly investigated during this study. Typical adsorption isotherms were determined, which were found to fit sufficiently the typical Langmuir equation. The mechanism of sorption was examined by electrokinetic, X-ray diffraction, Fourier transmission infrared and scanning electron microscopy measurements. Promising results were obtained, due to the favourite characteristics of the adsorbent applied.