Non-biological reduction of Cr(vi) by reacting with humic acids composted from cattle manure

Abstract

Previous studies on reduction of Cr(VI) by humic acids (HAs) have seldom used the extracts from composted animal manure. For greater yields of HAs and resource reclamation of animal manure, cattle manure was used as the composting material in our study. The capacity of humic acids extracted from composted cattle manure (HAs cm ) to reduce Cr(VI) was tested under the influence of environmental factors (pH, illumination with light and dissolved oxygen). And the non-biological detoxification mechanism was investigated by using three-dimensional fluorescence, Fourier transform infrared spectroscopy (FTIR) and X-ray absorption near-edge structure (XANES) spectroscopy. The results indicated that Cr(III) after the reduction of Cr(VI) formed an outer sphere complex with -OH and inner sphere complex with carboxyl groups in HAs cm .

Influence of pH on Cr(VI) reduction by organic reducing substances from sugarcane molasses

“…Chromium pollution is the most common type of heavy metal pollution in groundwater pollution site. In general, chromium exists in groundwater with two stable oxidation states: hexavalent C(VI) and trivalent Cr(III) (Yurik and Pikaev 1999) , which are known to be toxic, carcinogenic and mobile, causing health problems such as liver damage, pulmonary congestion, vomiting and severe diarrhea, whereas Cr(III) is less toxic and can be precipitated out of solution in the form of Cr(OH) 3 (Wu et al 2017). In China, there were up to 7 million tons chromium wastes, and more than 400 million tons chromium wastes were released into the environment directly, which severely polluted surface water environment, groundwater environment and soil environment (Gu et al 2005).…”

Highly Efficient and Reusable Montmorillonite/Fe3O4/Humic Acid Nanocomposites for Simultaneous Removal of Cr(VI) and Aniline

“…Coating HA onto Fe 3 O 4 NPs greatly improved the stability and dispersity and further adsorbed more heavy metals and organic pollutants. Besides, HA also worked as reductant to reduce Cr(VI) to Cr(III) [ 29 , 30 , 31 ]. Therefore, the synergistic effects between Fe 3 O 4 NPs, Mt and HA contributed greatly to the improvement of adsorption ability and removal efficiency in MFH.…”

“…As the surface charge can be affected by pH, the surface of MFH will become more positively charged when pH decreases and thus will have stronger electrostatic attraction with Cr(VI) anions. Adsorption is often affected by electrostatic repulsion and attraction between adsorbent and adsorbate [ 30 ]. Stronger electrostatic repulsion due to higher pH will lead to less adsorption of Cr(VI) anions.…”

“…HA has strong complexation ability towards heavy metals and organic pollutants, which can restrict their mobility in water [ 28 ]. Besides, both Fe 3 O 4 and HA have been reported to effectively reduce Cr(VI) to less toxic Cr(III) in many studies, and HA coated magnetite has also been utilized for Cr(VI) adsorption and reduction (See References [ 29 , 30 , 31 ] for detailed mechanisms). Studies demonstrated that substituted phenols, α-hydroxyl carboxylic acids, oxalic acid, and α-carbonyl carboxylic acids in HA participated in the reduction reaction of Cr(VI) and lower pH can make Cr(VI) more easily reduced by improving the redox potential of Cr(VI)/Cr(III) [ 30 , 31 ].…”

Morphology analysis of hexavalent chromium reduction to trivalent chromium with syrup under different pH conditions

“…Most of the contaminated sites need to be remedied as soon as possible. The toxicity of Cr(III) is relatively small, and it is insoluble compared with Cr(VI) (Gao and Liu 2017;Kang et al 2017;Malik et al 2017;Wu et al 2017). Hence, the reduction of hexavalent chromium to trivalent chromium is considered an important remediation strategy.…”