Supercritical water/supercritical carbon dioxide combined treatment method for arsenic-contaminated soil

Abstract

The invention relates to a supercritical water / supercritical carbon dioxide combined treatment method for arsenic-contaminated soil, and belongs to the technical field of soil remediation. The supercritical water / supercritical carbon dioxide combined treatment method comprises: placing arsenic-contaminated soil in a high-temperature and high-pressure reaction kettle I, adding a metal binder, introducing carbon dioxide gas, carrying out heating pressurizing to achieve the supercritical state of the carbon dioxide, and carrying out contact extraction for 15-120 min to obtain repaired soil and the extracted product, wherein the temperature of the carbon dioxide in the supercritical state is 40-80 DEGC, and the pressure is 10-45 MPa; and adding the extracted product, water and an excess oxidant to a high-temperature and high-pressure reaction kettle II, uniformly mixing to obtain a reaction system, carrying out heating pressurizing on the reaction system in the high-temperature and high-pressure reaction kettle II under a closed condition until the reaction system achieves a water supercritical state, and carrying out a reaction for 5-45 min to obtain the reaction product system, wherein the temperature of the supercritical state is 380-650 DEGC, and the pressure is 23-55 MPa. According to the present invention, arsenic is gently extracted by supercritical carbon dioxide so as to repair contaminated soil while recover the arsenic in the form of arsenic trioxide.

Description

technical field [0001] The invention relates to a supercritical water / supercritical carbon dioxide combined treatment method for arsenic-contaminated soil, belonging to the technical field of soil remediation. Background technique [0002] Arsenic and its compounds are common environmental pollutants and are highly toxic carcinogens. If they are not controlled, they will easily pollute the environment, and once the pollution is formed, it will be difficult to eliminate. It has been recognized by the US Centers for Disease Control and National Defense. Cancer Research Institute identified as the first class of carcinogens. Arsenic will enter the human body through the food chain or surface water and groundwater, seriously damaging human health. In recent years, with the extensive development of metal mines and the wide application of arsenic in industry, the amount of arsenic-containing wastewater and waste residues has increased day by day. The diffusion of wastewater in th...

AI Technical Summary

Problems solved by technology

Chinese patent CN102504832A discloses a soil arsenic passivator. The raw materials used include biomass coke, red mud, and ferric chloride. Red mud and straw biomass coke are mixed, ferric chloride solution is added, and carbonized and cooled. The passivating agent obtained by sieving has a certain passivating effect on arsenic, but the passivating effect is not good for a long time

Although the arsenic has been harmlessly treated to a certain extent, the arsenic has not been recovered, resulting in a waste of arsenic resources