CN-118635263-B - Method for synchronously removing lead, cadmium and arsenic in soil

Abstract

The invention relates to a method for synchronously removing lead, cadmium and arsenic in soil, belonging to the technical field of soil pollution treatment. The invention provides the method for efficiently treating the heavy metal contaminated soil by utilizing the lignosulfonate and the electrochemical process, and synchronously realizing the efficient and synchronous removal of pollutants such As Pb, cd, as and the like. The invention takes heavy metal contaminated soil as a treatment object, adds the treatment object into water, adds lignosulfonate, uniformly stirs the mixture to prepare slurry, takes iron material as an anode and takes inert material as a cathode, and performs electrolysis in a stirring state, wherein the control voltage is 0.4-0.6V during electrolysis, and the addition amount of the lignosulfonate is 0.1-1% of the mass of the treatment object. The method has the advantages of simple and controllable process, high efficiency, excellent synchronous removal effect and convenient popularization and application.

Inventors

• PING YANG
• ZHANG PING
• ZHANG ZHENZHOU
• XU HAO
• WANG QIMING
• YANG ZHIHUI
• YANG WEICHUN

Assignees

• 中电建生态环境集团有限公司
• 中南大学

Dates

Publication Date

20260505

Application Date

20240711

Claims (1)

1. 1. A method for synchronously removing Pb, cd and As in soil is characterized by comprising the following steps of taking heavy metal polluted soil As a treatment object, adding the treatment object into water, adding lignosulfonate, uniformly stirring to prepare slurry, then carrying out electrolysis in a stirring state by taking an iron material As an anode and taking an inert material As a cathode, wherein the control voltage is 0.49-0.51V, and the addition amount of the lignosulfonate is 0.49-0.51% of the mass of the treatment object; Adding the treatment object into the aqueous solution according to the mass ratio of water=1:9-15, and stirring; controlling the pH of the slurry to 7-8; the inert material used as the cathode is at least one selected from titanium, graphite and stainless steel; When electrolysis is carried out, the rotating speed is controlled to be 50-150 rpm; When electrolysis is carried out, the electrode spacing is 35-45 mm; when electrolysis is carried out, the treatment time is 100-150min; When electrolysis is carried out, the electrolytic tank is a circular tank; In the soil within 2 hours, the removal rate of water-soluble Pb is 100%, the removal rate of effective Pb is more than or equal to 72%, the removal rate of water-soluble Cd is 100%, the removal rate of effective Cd is more than or equal to 32%, the removal rate of water-soluble As is 100%, the removal rate of effective As is more than or equal to 78%, pb, cd and As are synchronously removed, and lignin sulfonate is at least one selected from calcium lignin sulfonate, potassium lignin sulfonate and sodium lignin sulfonate.

Description

Method for synchronously removing lead, cadmium and arsenic in soil Technical Field The invention relates to a method for synchronously removing lead, cadmium and arsenic in soil, belonging to the technical field of soil pollution treatment. Background Soil pollution is a global environmental hazard caused by factors such as industrial development, tailing exploitation, agricultural pesticide abuse, improper waste treatment and the like. The report of soil pollution investigation in China in 2014 shows that the pollution of lead (Pb), cadmium (Cd) and arsenic (As) accounts for 70% of the pollution of the national standard exceeding heavy metals. Heavy metal pollution (Pb, cd and As) in soil not only deteriorates water and food quality, but also reduces the usability of agricultural land, which may cause significant problems to human beings and ecosystems. Therefore, in order to solve the pollution problem of Pb, cd and As in soil, it is important to propose an efficient synchronous repair technology. The pollution of multicomponent heavy metals in soil is serious and ubiquitous to the ecosystem. Complex interactions exist among various heavy metals in soil, and as different heavy metals have different chemical properties, barriers exist in high-efficiency synchronous remediation of multiple metal pollution. Taking the pollution of Pb, cd and As in soil As an example, pb and Cd elements mainly exist in the form of cations, and As elements mainly exist in the form of oxyanions. With the change of pH value in the soil, the existence forms of Pb, cd and As can be correspondingly changed. The higher the pH, the stronger the electrostatic adsorption of Pb and Cd, and the Pb 2+ and Cd 2+ in the soil will precipitate, which will also result in a reduced exchangeable Pb and Cd content in the soil. And a decrease in the pH of the soil will cause Cd and Pb to dissociate, releasing it back into the soil. For As element, the negative charge in the soil (from anions or OH -) increases with increasing pH of the soil, rejecting the same negatively charged oxyanion. Thus, these negative charges compete with it for adsorption sites associated with As, which will lead to desorption of As, and the inflow of As element in the soil will also increase. The different oxygen-containing environments also have a significant impact on the effectiveness and form of presence of Pb, cd and As. In an oxygen limited environment, the soil pH tends to rise and the effectiveness of Cd and Pb will decrease. However, low-toxicity pentavalent As (H 2AsO4- and HAsO 42-) is mainly present in aerobic soil, while high-toxicity trivalent As (H 3AsO3 and H 2AsO3-) is commonly present under anaerobic conditions. These significant differences therefore present challenges for simultaneously addressing the contamination caused by these three heavy metals. At present, the soil heavy metal restoration technology mainly comprises a physical method, a chemical method, a biological restoration method and the like. While these strategies are universally applicable, they also have respective limitations. First, there is a need to further increase repair efficiency to meet the increasing need for rapid repair. Second, due to the different nature of individual metals, the treatment of multiple types of heavy metals in contaminated soil requires multiple technical combinations. Finally, certain soil remediation processes require the use of large amounts of chemicals, which can lead to secondary pollution. In recent years, electrochemical technology has become a treatment method for rapidly and efficiently removing aqueous solution and heavy metals in soil due to compact equipment structure, simple operation and high cost efficiency. Electrochemical treatment can mineralize metal ions in contaminated soil through a variety of processes such as electrolysis, electro-adsorption, and electro-deposition. Cu and Zn are removed from the contaminated soil by electrochemical adsorption deposition using an electrochemical treatment method as described in Qiu et al. In addition, cui and his co-workers developed an electrochemical remediation method through the concept of asymmetric alternating current electrochemistry, while achieving contaminant removal of various heavy metals (Cu, pb, cd) in the soil. However, the electrochemical process is mainly used for simultaneous treatment of pollutants in the form of single cations or anions, and less research and study are reported on simultaneous treatment of pollutants with opposite chemical properties such As Pb, cd and As. Disclosure of Invention Aiming at the defects existing in the prior art, the invention provides the method for efficiently treating the heavy metal contaminated soil by utilizing lignosulfonate and an electrochemical process, and synchronously realizing the efficient and synchronous removal of pollutants such As Pb, cd, as and the like. The method for synchronously removing Pb, cd and As in soil comprises the