Speciation analysis of chromium after reduction of chromium (VI) by humic acid

Abstract

Chromium species after the reduction of Cr(VI) by humic acid (HA) were analyzed. Cr(VI) inorganic species were determined by a colorimetric method with diphenylcarbazide, and inorganic Cr(III) cationic and Cr(III)-HA complex species were determined by atomic absorption spectrometry after separation with a cation-exchanger. After the reduction of Cr(VI) by HA for 62 days, about 30 % of the total Cr existed in the Cr(III) complex bound with HA, and about 10 % of the total Cr was present as the inorganic Cr(III) form. The ratio of the concentration of Cr(III)-HA complex to reduced species of Cr(VI) increased with pH. It was found that the majority of chromium species after the reduction was present as complex form with HA. The results of the time-dependent speciation analysis showed that the concentration of inorganic Cr(III) cation dissociated from Cr(III)-HA complex increased with the reaction time in the acidified condition. The fate and hazardous of Cr species after the reduction were discussed by referring to the obtained kinetic results.

Soil humic acids may favour the persistence of hexavalent chromium in soil

“…Due to the very slow kinetics of complexation equilibria between Cr(III) and humate ligands (Fukushima et al, 1997), we carried out experiments up to 2 weeks after addition of HAs to Cr(VI) solutions. However, under our experimental conditions, the reaction appeared to be complete after 20 min, as the lmax Abs peak of chromate progressively decreased within 20 min after HAs addition, but remained stable for 2 weeks thereafter.…”

Gene induction studies and toxicity of chemical mixtures.

“…Organochlorine pesticides and inorganic chemicals used in these studies. (13,14). Specific details of chemical treatments for each metal or mixture are given in Table 3.…”

“…In the second study, four high-priority metals and a mixture were tested for their ability to induce 13 different gene promoters in a battery of recombinant HepG2 cells (Table 1). The organic pollutants and their Comprehensive Environmental Response, Compensation and Liability Act of 1980 (or Superfund) (Public Law 96510, 11 December 1980) priority rankings (indicated in square brackets) are p,p´-DDT [13], p,p´-DDD [26], p,p´-DDE [22], aldrin [25], dieldrin [18], and endrin [39]. The metals studied were arsenic (As) [1], lead (Pb) [2], cadmium (Cd) [7], Cr(VI) [16], and Cr(III) [69].…”

Adsorption of Chromium (VI) from Aqueous Solution Using Zeolit/Chitosan Hybrid Composite

“…It is well known that, Cr(III) is essential materials for living organisms, whereas, Cr(VI) is more toxic, carcinogenic and mutagenic, is considered as severe pollutant due to high water-solubility and toxicity [6][7][8][9][10]. The maximum levels permitted in wastewater are 5 mg·dm -3 for trivalent and 0.05 mg·dm -3 for hexavalent chromium [11].…”