Method for producing carbon dioxide anionic free radicals and method for treating hexavalent-chromium-containing waste water

Abstract

The invention provides a method for producing carbon dioxide anionic free radicals and a method for treating hexavalent-chromium-containing waste water. Formic acid is activated via ultraviolet radiation to produce carbon dioxide anionic free radicals, which are used for treating Cr(VI) waste water. It is shown from the result that carbon dioxide anionic free radicals can fast reduce Cr(VI) to Cr(III). Compared with conventional activation technology, the method is low in treatment cost, mild in reaction system, and free of any secondary pollution since the reaction products are H2O and CO2. The method is particularly suitable for fast efficiently treating low-concentration chromium-containing waste water, and has high commercial application value.

Description

technical field [0001] The invention relates to the field of wastewater treatment, in particular to a method for producing carbon dioxide anion radicals and a method for treating wastewater containing hexavalent chromium. Background technique [0002] Hexavalent chromium (Cr(VI)) is a highly toxic substance that is carcinogenic, teratogenic, and mutagenic. It is listed as one of the most toxic pollutants by the US Environmental Protection Agency (USEPA), and it is also one of the five types of heavy metal pollutants under national key control. First, therefore, the mass concentration of hexavalent chromium must be strictly controlled in chromium-containing wastewater, and discharge can only be allowed after reaching the standard. According to the comprehensive sewage discharge standard (GB 8978-1996), Cr(VI) belongs to the first category of pollutants, and its maximum allowable discharge concentration is 0.5mg / L. At present, there are many chromium-related industries in my ...

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Problems solved by technology

[0004] 1. Separate Cr(VI) from the system through physical and chemical means, specifically including the following technologies: (a) Reverse osmosis (RO): Water molecules pass through a semi-permeable membrane by pressurization to achieve the concentration of Cr(VI), To achieve the purpose of separation, reverse osmosis generally does not involve secondary pollutants, but the membrane oxidation caused by membrane fouling is still an important factor restricting the wide application of current commercial reverse osmosis membranes; (b) ion exchange method: using anion exchange The anions in the resin are exchanged with Cr(VI) in the water to achieve the purpose of separation. Cr(VI) exists in the form of chromate in the wastewater, which involves the regeneration of the resin; (c) electrodialysis: electrodialysis refers to Under the action of direct current, the anions and cations in the water can selectively pass through the anion and cation membrane, and the concentration of Cr(VI) can be realized, but it is not suitable for electrodialysis treatment of high-quality Cr(VI)-containing wastewater. , large power consumption; (d) Adsorption method: use adsorbent to adsorb Cr(VI) to achieve the purpose of separation. At present, widely used adsorbents include activated carbon, zeolite and other inorganic adsorbents, wood chips, corncobs and their modified For biologically active organisms such as products, the only disadvantage of the adsorption method is the problem of economic investment. Treating waste with waste is the best solution currently sought.

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