Method for removing trivalent arsenic

Abstract

The invention provides a method for removing trivalent arsenic, comprising the following steps: (1), oxidizing trivalent arsenic in an arsenic solution into pentavalent arsenic at pH of 0.9-1.5 by using ozone to obtain pentavalent arsenic solution; (2), adding a soluble divalent iron source into the pentavalent arsenic solution, oxidizing divalent iron at a temperature higher than 70 DEG C at pH less than 1.5 into trivalent iron, and reacting the pentavalent arsenic with trivalent iron to obtain a solution containing scorodite crystal precipitate, goethite precipitate and divalent iron; (3), adjusting pH of the solution obtained in step (2), oxidizing the divalent iron in the solution to form iron peroxide gel, and carrying out solid-liquid separation to obtain a purified solution.The method enables low-concentration arsenic in waste water to be removed, arsenic content of the purified solution is lower than 0.05 mg / L, the precipitates generated in the arsenic removal process are easy to remove, and the method is simple to perform and is widely applicable to purifying waste water containing low-concentration arsenic.

Description

technical field [0001] The invention belongs to the technical field of pollutant treatment, and relates to a method for removing trivalent arsenic, in particular to a method for removing trivalent arsenic in a solution by using ozone. Background technique [0002] Arsenic is a highly toxic element, and a small amount of ingestion can cause death. Chronic arsenic poisoning can cause cancer and other diseases. On the other hand, arsenic is a relatively abundant element in nature, and it is one of the 20 most abundant elements in the earth's crust, and there are more than 200 arsenic-containing minerals. Mine development and natural weathering can lead to the dissolution of arsenic-containing minerals, resulting in arsenic-containing wastewater, resulting in large-scale arsenic pollution. Such arsenic-containing wastewater usually has a low arsenic concentration, ranging from tens of milligrams per liter to several grams per liter, but arsenic mainly exists in the form of high...

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Problems solved by technology

However, the rate of oxidation of trivalent arsenic in water to pentavalent arsenic under acidic conditions is very slow, so scorodite can only be produced by pressurized oxidation in the existing industrial process, which requires high equipment investment and great difficulty in production. GordonM. Ritcey. mentioned in the article (Tailingsmanagementingoldplants.Hydrometallurgy, 2005, 78, 3–20) that the scorodite arsenic fixation method is only applied in a few gold smelting enterprises that adopt the pressure leaching process route

G.P.Demopoulos et al. from McGill University in Canada proposed a method to convert arsenic into scorodite under normal pressure , air is introduced into the mixed solution of ferrous iron and pentavalent arsenic to keep the pH of the solution at about 1.0 and the reaction temperature at 95°C, adding seeds can generate scorodite under normal pressure, but this method requires The concentration of arsenic is relatively high, usually above 10g / L, and only part of the arsenic can be converted into scorodite, and the rate of arsenic precipitation at one time is low. , not suitable for direct treatment of low-concentration arsenic-containing wastewater

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