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CN-121991694-A - Iron-phosphorus-based passivation material for cadmium-arsenic composite contaminated soil, and preparation method and application thereof

CN121991694ACN 121991694 ACN121991694 ACN 121991694ACN-121991694-A

Abstract

The invention relates to the technical field of environmental functional materials and soil pollution restoration, and discloses an iron-phosphorus-based passivation material for cadmium-arsenic composite polluted soil, a preparation method and application thereof. The material is prepared by carrying out in-situ chemical modification on a Schlegel mineral precursor by phosphate. Phosphate is added into the schner mineral precursor suspension to carry out in-situ chemical modification reaction, and the iron-phosphorus-based passivation material is obtained after washing, drying and grinding. The phosphate radical in the material partially replaces sulfate radical in a Schlegel mineral structure in a chemical bonding mode, so that the material has the functions of iron-based solid As and phosphorus-based solid Cd, the effective state content and mobility of Cd and As in soil can be obviously reduced, synchronous and long-acting passivation of the Cd and As in the soil can be realized, and the material is particularly suitable for repairing and safely utilizing Cd-As composite polluted farmland soil. The preparation process has mild conditions, easily obtained raw materials, uniform and stable product structure, and good economical efficiency and application prospect.

Inventors

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

Assignees

  • 华中农业大学

Dates

Publication Date
20260508
Application Date
20260130

Claims (10)

  1. 1. The preparation method of the iron-phosphorus-based passivation material for the cadmium-arsenic composite contaminated soil is characterized by comprising the following steps of: Mixing a Schneider mineral precursor suspension with phosphate for reaction for 1-3 hours to load and embed phosphate on the surface of the Schneider mineral to obtain slurry, wherein phosphorus in the phosphate accounts for 5-30% of iron in the Schneider mineral precursor suspension; Centrifuging the slurry, taking and washing the precipitate, drying, grinding and sieving to obtain the iron-phosphorus-based passivation material.
  2. 2. The method for preparing an iron-phosphorus-based passivation material for cadmium-arsenic composite contaminated soil according to claim 1, wherein the phosphate is sodium dihydrogen phosphate or disodium hydrogen phosphate.
  3. 3. The method for preparing the iron-phosphorus-based passivation material for cadmium-arsenic composite contaminated soil according to claim 1, wherein the specific obtaining process of 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-phosphorus-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-phosphorus-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 method for preparing the iron-phosphorus-based passivation material for the cadmium-arsenic composite contaminated soil according to claim 1, wherein the sieving is performed through a 50-100 mesh screen.
  7. 7. An iron-phosphorus-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-phosphorus-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 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-phosphorus-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 functional materials and soil pollution restoration, in particular to an iron-phosphorus-based passivation material for cadmium-arsenic composite polluted soil, a preparation method and application thereof. Background Soil heavy metal pollution is an important environmental problem restricting agricultural sustainable development, wherein the restoration difficulty of the combined pollution of cadmium (Cd) and arsenic (As) is extremely high due to the obvious geochemical antagonism. Arsenic has enhanced activity under flooded reduction conditions, while cadmium has increased mobility under oxidizing and acidic conditions. Due to the diametrically opposite chemical behaviors of the two materials in the soil, the synchronous and efficient passivation of Cd and As is difficult to realize by the traditional single-function repair material. For example, lime materials can effectively fix cadmium by increasing the pH, but tend to cause activation leaching of arsenic, while iron-based materials have good adsorption performance for arsenic, but generally have limited passivation effect for cadmium. The schner mineral (SCHWERTMANNITE) is a ferric hydroxysulfate mineral formed by ferrous salt oxidation, has larger specific surface area, abundant surface hydroxyl sites and higher sulfate radical content, and has excellent adsorption and coprecipitation capability for arsenic. However, schlieren minerals are generally positively charged at ambient pH conditions and have a weak adsorption fixing capacity for the cation Cd 2+. In addition, it may transform and release sulfate in the environment, resulting in local microenvironment acidification, which may instead increase the bioavailability and migration risk of cadmium, severely limiting its direct application in the remediation of Cd-As complex contamination. To improve the fixing ability of the material to cadmium, the introduction of phosphate is considered as an effective modification strategy. Phosphate radical can not only enhance electronegativity of mineral surface to promote electrostatic attraction to Cd, but also can carry out strong coordination with Cd and even form insoluble cadmium phosphate precipitate. In the prior art, there have been attempts to modify the phosphate by physical mixing with the donor mineral by mechanical ball milling. Although the method can increase the specific surface area of the material to a certain extent and expose more active sites, the modification nature of the material depends on physical mixing, the bonding strength of phosphate radical and mineral surface is insufficient, and desorption loss easily occurs in a complex soil/water environment. In addition, the intense high-speed ball milling process risks destroying the self-crystal structure of the schlieren mineral, which may impair its core fixing ability to As. Disclosure of Invention In order to solve the problems, the invention provides the iron-phosphorus-based passivation material for the cadmium-arsenic composite polluted soil, the preparation method and the application thereof, and the stable and efficient combination of phosphate radical and schner minerals is realized through a chemical approach, so that the synchronous fixing capability of the composite system to cadmium and arsenic is essentially synergistically improved, and the long-acting and stable iron-phosphorus-based passivation material is obtained. The invention provides a preparation method of an iron-phosphorus-based passivation material for cadmium-arsenic composite contaminated soil, which comprises the following steps: Mixing a Schneider mineral precursor suspension with phosphate for reaction for 1-3 hours to load and embed phosphate on the surface of the Schneider mineral to obtain slurry, wherein phosphorus in the phosphate accounts for 5-30% of iron in the Schneider mineral precursor suspension; Centrifuging the slurry, taking and washing the precipitate, drying, grinding and sieving to obtain the iron-phosphorus-based passivation material. The invention carries out in-situ chemical modification on the Schlemen mineral precursor by phosphate, the phosphate radical is introduced in a chemical bonding mode, and partially replaces sulfate radical in the Schlemen mineral structure, and the invention obviously enhances the surface electronegativity on the basis of retaining the amorphous or weak crystal structure characteristics of the Schlemen mineral. According to the invention, the phosphorus in the phosphate accounts for 5-30% of the mole percentage of iron in the Schlemen mineral precursor suspension, so that the obtained passivation material has a good fixing effect on cadmium and arsenic. If the molar percentage of iron is too low, the phosphate is not loaded enough and the Cd