Double-anode electric flocculation arsenic removing method

Abstract

The invention provides a double-anode electric flocculation arsenic removing method. The method is used for treating polluted groundwater in an in-situ treatment mode or a pumping-out treatment mode. The method comprises the following steps of: performing electric flocculation treatment on the polluted groundwater by using double anodes or one cathode; supplying direct current to the three electrodes; and regulating the size of the total current and the distribution proportion of the total current between the double anodes, thereby oxidizing the arsenic (III) into the arsenic (V) and a bivalent iron precipitate into a ferric iron precipitate so as to remove the arsenic from the polluted groundwater, wherein one anode is an iron anode while the other anode is an inert anode. According to the method, dissolved oxygen and divalent iron are supplied into the groundwater by utilizing the double anodes, so that the oxidation of the trivalent arsenic and the adsorption removal of the trivalent arsenic on the iron precipitate are promoted. The method has the advantages of high restoring efficiency, short treatment time, low operation cost, environment friendliness, flexibility, controllability and the like. The method has great economic and social benefits in the treatment field of the groundwater polluted by the arsenic. As a result, the method has a board market prospect.

Description

technical field [0001] The invention relates to an electrochemical treatment method for arsenic-contaminated groundwater, in particular to a method for removing arsenic by double-anode electric flocculation technology, which realizes the purification treatment of arsenic-contaminated groundwater and belongs to the technical field of groundwater restoration. Background technique [0002] Arsenic pollution of groundwater is a common problem faced by the whole world. It is threatening more than 50 million people in at least 22 countries and regions, most of them are Asian countries, and Bangladesh, India and China are the most serious. Groundwater is an important part of drinking water, and about 70% of the population in my country drinks groundwater. According to WHO standards, the exposed population in my country's arsenic poisoning hazard areas is as high as 15 million. This poses a great threat to the protection of water resources in my country's strategic water sources, a...

AI Technical Summary

Problems solved by technology

However, unlike surface water, groundwater is an anoxic environment, and there is a problem of difficult supply of dissolved oxygen.

The lack of dissolved oxygen will cause the following obstacles to the implementation of electrocoagulation technology: ① Arsenic in water usually exists in two valence states of +3 and +5. In anoxic reducing water bodies such as groundwater, it mainly exists in the form of arsenic (Ⅲ), and the toxicity of arsenic (Ⅲ) is much higher than that of arsenic (Ⅴ) (60:1).

Since the electroflocculation technology only uses two electrodes, the iron anode and the cathode, the oxidation of arsenic(Ⅲ) cannot be achieved, so the iron sludge containing highly toxic arsenic(Ⅲ) after adsorption still has the problem of safe handling and disposal. The environment is still at high risk

② The lack of dissolved oxygen in groundwater makes the iron products in electrocoagulation mainly stay in the stage of ferrous iron precipitates, and its adsorption efficiency is much lower than that of ferric iron precipitates, so its adsorption of arsenic does not achieve the best effect, and at the same time Fe(OH) with higher solubility product constant 2 The treated effluent will contain a certain concentration of Fe 2+ , causing environmental risks

[0005] Filling the groundwater with air or oxygen can solve the above problems. No matter in the in-situ remediation or "extraction and treatment" method, the injection of air has the problem of poor economy or uncontrollable effect

For example, the cost of injecting air tens of meters underground in in-situ remediation is high, and the injection volume is difficult to control, which may have a great impact on the occurrence conditions of groundwater

In the post-extraction treatment method, it is difficult to control the amount of oxygen charged, and the oxygen bubbles charged are relatively large and the utilization rate is low.

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