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CN-122012099-A - Iron-carbon-based passivation material for cadmium-arsenic composite contaminated soil, and preparation method and application thereof

CN122012099ACN 122012099 ACN122012099 ACN 122012099ACN-122012099-A

Abstract

The invention belongs to the technical field of heavy metal contaminated soil remediation, and discloses an iron-carbon-based passivation material for cadmium-arsenic composite contaminated soil, and a preparation method and application thereof. The material is prepared by in-situ chemical synthesis, corn straw biochar is introduced into a Schneider mineral precursor, so that Schneider mineral particles are loaded on the surface and in pores of the Schneider mineral particles in situ, and the iron-carbon composite passivation material is obtained. The method has the advantages of simple process, low energy consumption and easily available raw materials, and is suitable for large-scale preparation. The obtained material has double functions of schiff mineral and biochar, the iron component has strong adsorption and coprecipitation capability on anion As (V), the carbon component has high-efficiency adsorption and complexation capability on cation Cd, and the synchronous stabilization of Cd and As is realized by the synergistic effect of the iron component and the carbon component. The soil culture experiment proves that the material can effectively reduce the bioavailability and mobility of Cd and As in the polluted soil, and is suitable for restoring and safely utilizing the Cd-As composite polluted farmland soil.

Inventors

  • WANG XIAOMING
  • LI ZAIWEN
  • CHEN JINDE
  • FENG XIONGHAN

Assignees

  • 华中农业大学

Dates

Publication Date
20260512
Application Date
20260130

Claims (10)

  1. 1. An iron-carbon-based passivation material for cadmium-arsenic composite contaminated soil, comprising the steps of: Mixing the Sch mineral precursor suspension with the biochar to enable the Sch mineral to grow and load on the surface and pores of the biochar in situ, and obtaining the iron-carbon-based passivation material after solid-liquid separation, washing, drying, grinding and sieving; The biochar is corn straw biochar, and the mass of the corn straw biochar accounts for 5% -15% of the mass of ferrous salt in the Schlemen mineral; In the cadmium-arsenic combined polluted soil, cadmium is Cd (II), and arsenic is As (V).
  2. 2. The iron-carbon-based passivation material for cadmium-arsenic composite contaminated soil according to claim 1, wherein the schner mineral precursor suspension is mixed with biochar for 2-4 hours at 20-28 ℃.
  3. 3. The iron-carbon-based passivation material for cadmium-arsenic composite contaminated soil according to claim 1, wherein the specific process of obtaining the schner mineral precursor suspension is as follows: And (3) adding an oxidant into the soluble ferrous salt solution under an acidic condition to perform an oxidation reaction to generate a Schlemen mineral precursor suspension.
  4. 4. The method for preparing the iron-carbon-based passivation material for cadmium-arsenic composite contaminated soil according to claim 3, wherein the soluble ferrous salt is ferrous sulfate heptahydrate; the molar ratio of the oxidant to the ferric ions in the soluble ferrous salt is 0.7-0.9:1.
  5. 5. The method for preparing the iron-carbon-based passivation material for the cadmium-arsenic composite contaminated soil, which is characterized in that the pH of the acidic condition is 1.8-2.2, the temperature of the oxidation reaction is 20-28 ℃, and the reaction time is 20-28 h.
  6. 6. The iron-carbon-based passivation material for cadmium-arsenic composite contaminated soil according to claim 1, wherein the sieving is through a 50-100 mesh screen.
  7. 7. An iron-carbon-based passivation material for cadmium-arsenic composite contaminated soil prepared by the preparation method of any one of claims 1-6.
  8. 8. Use of the iron-carbon based passivation material for cadmium-arsenic composite contaminated soil according to claim 7 in soil remediation, wherein the soil remediation is to remediate Cd (II) and As (V) in the soil.
  9. 9. The application of the iron-phosphorus-based passivation material for cadmium-arsenic composite contaminated soil remediation according to claim 8, wherein the application amount of the iron-phosphorus-based passivation material is 0.1% -5% of the dry mass of the soil.
  10. 10. The use of the iron-phosphorus based passivation material for cadmium-arsenic combined contaminated soil according to claim 8, wherein the repair process comprises a flooded culture stage and a drop dry culture stage for simulating farmland rice crop moisture management conditions.

Description

Iron-carbon-based passivation material for cadmium-arsenic composite contaminated soil, and preparation method and application thereof Technical Field The invention relates to the technical field of environmental pollution restoration and functional materials, in particular to an iron-carbon-based passivation material for cadmium-arsenic composite polluted soil, and a preparation method and application thereof. Background Cadmium (Cd) and arsenic (As) combined pollution in paddy field soil is a prominent problem faced by current farmland environment management. The complex root of the restoration is that Cd and As show remarkable geochemical antagonistic behavior in soil, cd activity is enhanced under acidic and anaerobic reduction conditions, and As (V) is more easy to migrate under alkaline and aerobic conditions. This opposite environmental behavior results in the fact that conventional single passivation materials often lose their ability to achieve synchronous and efficient immobilization of Cd and As. The schiff mineral (SCHWERTMANNITE) is a tunnel-shaped iron hydroxysulfate mineral with Fe 3+, and has rich surface hydroxyl groups, huge specific surface area and sulfate radical in the structure, and has extremely strong specific adsorption and coprecipitation capability for As (V). However, its surface properties, which are usually positively charged in the environment, result in a limited ability to fix the cation Cd. In addition, nanoscale schlieren mineral particles are easy to agglomerate, so that the reactivity of the nanoscale schlieren mineral particles is reduced, sulfate radicals can be released in the mineral transformation process, and the soil acidification and the migration of cadmium are potentially aggravated. Biochar, in particular to biochar prepared from corn stalks, is a porous carbon material with a hollow tubular structure, high specific surface area and rich oxygen-containing functional groups. These properties make it exhibit excellent adsorption capacity for cationic heavy metals such as Cd. However, biochar surfaces are typically negatively charged and have a weak adsorption capacity for As in anionic form. From this, the schner minerals and the corn stalk biochar are exactly complementary in chemical characteristics, wherein the schner minerals and the corn stalk biochar are ideal materials for fixing As, and the schner minerals and the corn stalk biochar are high-efficiency carriers for fixing Cd. Although there has been a preliminary search in the prior art for complexing schiff minerals with biochar, these studies have focused on the removal of single contaminants such As (III) or Cr (VI) in the aqueous phase, failing to fully consider the complexity of Cd-As complex contamination in practical paddy soil, especially the critical environmental factor of periodic oxidation-reduction dynamics. More importantly, the stable combination and synergy of the iron-carbon components on the microscopic scale can not be realized by simple physical mixing, and the synchronous fixation problem caused by the antagonism of the Cd and As behaviors can not be fundamentally solved. Disclosure of Invention In order to solve the problems, the invention provides a method for compositing Schrad mineral and corn straw biochar by an in-situ chemical synthesis method, and aims to construct an iron-carbon-based passivation material with dual-function active sites and stable microstructure. The design can simultaneously utilize the strong adsorption of iron components to As and the high affinity characteristic of biochar to Cd to realize synchronous, stable and long-acting passivation of Cd and As, and has important scientific value and application prospect for treating the Cd-As composite pollution of rice fields. In order to achieve the above purpose, the technical scheme of the invention is as follows. The invention provides an iron-carbon-based passivation material for cadmium-arsenic composite contaminated soil, which comprises the following steps: Mixing the Sch mineral precursor suspension with the biochar to enable the Sch mineral to grow and load on the surface and pores of the biochar in situ, and obtaining the iron-carbon-based passivation material after solid-liquid separation, washing, drying, grinding and sieving; the biochar is corn straw biochar, the mass of the corn straw biochar accounts for 5% -15% of the mass of ferrous salt in the Schneider mineral, and in the cadmium-arsenic combined contaminated soil, cadmium is Cd (II) and arsenic is As (V). The corn stalk biochar accounts for 5% -15% of the ferrous salt in the Schlemen mineral, if the weight of the corn stalk biochar is too low, the carrier effect is insufficient, the Schlemen mineral is easy to agglomerate, and the corn stalk biochar has too high weight proportion and insufficient iron content, so that the fixing capability of As is affected. In another preferred embodiment, the schiff mineral precursor suspension is mixed wi