Chromium In Wastewater Samples Research Articles

Modification of graphene for speciation of chromium in wastewater samples by suspension solid phase microextraction procedure

In this study, the surface modification of graphene (SMG) was developed for efficient speciation and determination of chromium in water and wastewater samples. By procedure, the chromium ions were extracted from water/wastewater samples based on sulfonated and amine graphene (S-NG, N-NG) by suspension solid-phase microextraction procedure (SMSPE). Hydrophobic ionic liquid ([HMIM] [PF6]) was used for separation graphene from 10 mL of water. After shaking and centrifuging, the phase of Cr→ S-NG, Cr→N-NG was back-extracted by 0.2 mL of HNO3 (0.4 mol L-1) and finally chromium concentration determined with ET-AAS. The results showed the sulfonated and amine graphene can successfully extract Cr(III) and Cr(VI) from water and wastewater samples at pH=3.5-5.5 and pH<3, respectively. Also, the most Cr(VI) extracted by N-graphene at pH=2(NH3+→Cr2O7─). Under the optimal conditions, the linear range, LOD, and preconcentration factor were obtained 0.02–2.4 µg L−1, 5.0 ng L−1 and 20.2, respectively for Cr(III, VI) (%RSD<5%).

Utilization of modified corn silk as a biosorbent for solid-phase extraction of Cr(III) and chromium speciation.

The ues of corn silk modified with diluted nitric acid (HNO3-MCS) as a novel biosorbent has been established for solid-phase extraction of Cr(III) and chromium speciation in water samples. The functional groups of the HNO3-MCS surface are favorable for the adsorption of Cr(III). Effective extraction conditions were optimized in both batch and column methods. At pH 3.0 - 6.0, a discrimination of Cr(III) and Cr(VI) is achieved on the HNO3-MCS surface. Cr(III) ions are retained onto the HNO3-MCS surface, however, the adsorption of Cr(VI) is negligible under the same conditions. The adsorption isotherm of HNO3-MCS for Cr(III) has been demonstrated in accordance with a linear form of the Langmuir equation, and the maximum adsorption capacity is 35.21 mg g(-1). The well fitted linear regression of the pseudo-second order model showed the indication of a chemisorption mechanism for the entire concentration range. Thermodynamic studies have shown that the adsorption process is spontaneous and endothermic. The adsorbed Cr(III) was quantitatively eluted by a nitric acid solution with detection by flame atomic absorption spectrometry (FAAS). With a sample volume of 30 mL, a detection limit (3σ) of 0.85 μg L(-1) and a precision of 2.0% RSD at the 40 μg L(-1) level were achieved. The concentration of Cr(III) could be accurately quantified within a linear range of 3 - 200 μg L(-1). After Cr(VI) has been reduced to Cr(III) with hydroxylamine hydrochloride, the total amount of chromium was obtained, and the content of Cr(VI) was given by subtraction. The procedure was validated by analyzing chromium in a certified reference material (GBW (E) 080039). It was also successfully applied for the speciation of chromium in wastewater samples.

Field speciation of chromium with a sequential injection lab-on-valve incorporating a bismuthate immobilized micro-column

A fully automated and portable analyzer for field speciation of inorganic chromium in wastewater was developed. The instrument consists of a micro-sequential injection lab-on-valve (LOV) system and a miniature USB2000 spectrophotometer. A multi-purpose flow cell was incorporated on one side of the main body of the LOV, which offers vast potentials and versatilities in its compatibility with various detection modes. On-line oxidation of trivalent chromium was performed on a bismuthate immobilized silica micro-column reactor integrated in the LOV. When determining Cr(VI), its chromogenic reaction with 1,5-diphenylcarbazide (DPC) was facilitated in the flow cell and the absorbance was monitored in situ at 548 nm via optical fibers. While for the quantification of total chromium, Cr(III) was oxidized on-line by aspirating sample solution through the oxidizing column reactor, followed by chromogenic reaction with DPC and the absorbance was monitored in the flow cell. With a sampling volume of 200 μl, the detection limits of 5.6 μg l −1 for Cr(VI) and 6.8 μg l −1 for total chromium were achieved along with a sampling frequency of 60 h −1. A R.S.D. value of 2.0% was recorded at 32 μg l −1 of Cr(VI). The practical applicability of the speciation analyzer was validated by analyzing Cr(VI) and total chromium contents in two certified reference materials. The feasibility of performing rapid field speciation of chromium in wastewater samples was also demonstrated.

Use of 6-Mercapto Purinylazo Resin in Chromium Speciation

The present work describes a procedure of preconcentration, separation and determination of the two forms of chromium, viz. Cr(III) and Cr(VI), in waste water by using 6-mercaptopurine anchored by azo function to a polymeric styrene divinylbenzene (8%) matrix as solid phase extractor. The maximum exchange capacity for Cr(III) at pH 6.5 is 0.44 mmol g−1 and that for Cr(VI) at pH 1.0 is 1.06 mmol g−1. In the column operation, the recoveries of both Cr(III) and Cr(VI) in the presence of various foreign ions which are generally present in waste water were examined; it was observed that no such interferences occur in the sorption step. Flow rate optimization studies show that the column is efficient for the separation of both forms of chromium at a flow rate of 1.2 mL min−1. The metal ion concentration was measured by flame atomic absorption spectrometry. The method has been applied for the separation and speciation of chromium in waste water samples.

Round robin tests for the spectrophotometric determination of chromium in waste water samples according to the JIS method

Round robin tests for the spectrophotometric determination of chromium in waste water samples according to the JIS method