Selective Separation Of Chromium Research Articles

Selective separation of Chromium (VI) from aqueous solutions by adsorption onto truffle peels as novel biomass

ABSTRACT The current quest develops a simple and highly selective spectrophotometric method for trace determination of Cr(VI) in water using truffle peels powder (TPPs) as solid-phase extractor. Adsorption of Cr(VI) onto TPPs from aqueous media reached equilibrium at pH ≈1.7 in 20 min and was independent of the initial concentration of Cr(VI). The results showed that the maximum Cr(VI) adsorption capacity was found as 0.2776 mg g−1 from the Langmuir model at 25°C. The sorption of Cr(VI) followed pseudo-second-order kinetic with rate constant k2 = 0.013 g mg−1min−1 (R2 = 0.9982). Furthermore, thermodynamic parameters (ΔH, ΔS and ΔG) of Cr(VI) retention by the sorbent were calculated and assigned. The positive values of ΔH (45.61 J mol−1) proved the endothermic nature of Cr(VI) retention on TPPs and ΔS (162.45 Jmol−1K−1) reflected good absorption and/or adsorption of the chromate [(CrO3Cl)]− as an ion associate with the bulky cations and the surface area available on TPPs. The negative value of ΔG (−48.6 kJ mol−1 at 298 K) indicates the spontaneous and chemical sorption nature of Cr(VI) uptake onto TPPs.

Selective separation of chromium from sulphuric acid leaching solutions of mixed electroplating sludge using phosphate precipitation

The selective separation of chromium (Cr) from sulphuric acid leaching solutions is necessary for the harmless disposal and resource recycling of electroplating sludge. A method using phosphate precipitation was investigated. First, the thermodynamic analysis of a Cr3+ − Fe3+ − PO43–−H2O system and a Cr3+ − Fe2+ − PO43–−H2O system was analysed to evaluate the feasibility of Cr recovery, and the optimal operating windows were identified. The corresponding experiments were carried out based on the thermodynamic calculations, and the results showed that Cr and Fe can be selectively separated using phosphate in the presence of excess sulfite. The major factors, including the PO43−/Cr3+ ratio, solution temperature, pH and impurity concentration, were evaluated. Under the best conditions, over 97.04% of Cr can be separated and recovered as phosphate precipitation, while the precipitation efficiency of Fe was only 14.75%. Thermogravimetric and infrared analyses showed that the finial precipitation was a xCr(OH)3·yCrPO4·zH2O complex. The surface morphology of the precipitation presented in the form of an agglomeration when Fe existed in the solution. The impurities in the precipitation could be removed through a dilute sulphuric acid cleaning process. The consequence of phosphate precipitation could provide a practical and yet easy-to-adopt perspective for selectively separating Cr from sulphuric acid leaching solutions.

Ratio primary reference measurement procedure (RPRMP) for the certification of chromium content in biological reference materials

Abstract Primary reference measurement procedure for Cr determination in biological samples by radiochemical neutron activation analysis (RNAA) has been elaborated. The procedure is based on quantitative and selective separation of chromium from neutron irradiated sample by column chromatography using MnO2-Resin and determination of 51Cr by γ-ray spectrometry. Quality components have been incorporated into the RNAA method which makes it possible to meet the requirements of the definition of ratio primary reference measurement procedure. The usefulness of the elaborated procedure to assign the certified values for Cr in new certified reference material (CRMs) based on animal tissues is demonstrated. The tentative certified values for Cr have been proposed for: MODAS M-4 Cormorant Tissue and M-5 Cod Tissue CRMs.

Selective separation of chromium (VI) from acidic solutions containing various metal ions through emulsion liquid membrane using trioctylamine as extractant

Chromium compounds have received considerable attention because of used extensively in such industrial applications as electroplating, tanning of leather goods, steelmaking, and corrosion inhibition. In this work, selective separation and concentration of Cr (VI) ions from acidic solutions containing various metal ions through emulsion liquid membrane (ELM) containing trioctylamine (TOA) as extractant was studied. The membrane phase consists of kerosene as diluent, ECA 4360J as surfactant, TOA as extractant and 0.5 M (NH 4) 2CO 3 solution as stripping phase. The effect of acid type and concentration of the feed solution, initial Cr (VI) concentration of the feed solution, mixing speed, type and concentration of the stripping solution, surfactant concentration, extractant concentration and phase ratio was examined and optimum conditions was determined. After the optimum conditions were determined, it was possible to selectively extract 99% of Cr (VI) from the feed solutions containing Cu, Zn, Co, Ni and Cd ions.

über den Einsatz von Anionenaustauschern bei der Analyse von VerchromungsbÄdern

A procedure is proposed for the selective separation of chromium(VI) from industrial chromium-plating solutions. Subsequently, Cr(III), Fe(III) and other cations are determined. The advantages of liquid ion exchangers (sec. amine in n-heptane as solvent) are discussed in comparison with tertiary amines, solid ion-exchangers and other separation procedures. The influence of several parameters, which are of importance for optimising the experimental conditions, is shown by means of test results.

Note on the selective separation of chromium from ferro-chrome alloys

Note on the selective separation of chromium from ferro-chrome alloys

Solvent extraction of chromium(VI) with tribenzylamine

The use of tribenzylamine as an extracting agent is recommended for a simple and selective separation of chromium(VI). Interferences from foreign elements were investigated by means of radioactive tracers and spectrophotometric techniques. The method is applied to neutron activation analysis of chromium traces in various materials.