Search

CN-122010509-A - Low-alkalinity phosphogypsum composite heavy metal curing agent and preparation method and application thereof

CN122010509ACN 122010509 ACN122010509 ACN 122010509ACN-122010509-A

Abstract

The invention discloses a low-alkalinity phosphogypsum composite heavy metal curing agent, and a preparation method and application thereof. The low-alkalinity phosphogypsum composite heavy metal curing agent comprises, by mass, 5-8 parts of low-alkalinity gelling agent, 3-6 parts of activated crystal form regulator, 2-5 parts of chelating dispersant, 3-7 parts of enhanced chelating agent, 6-10 parts of efficient adsorbent and 63-84 parts of carrier. According to the invention, an aluminate cement-superfine slag powder-metakaolin compound system is initiated to replace the traditional high-alkali gelatinization agent, the pH of the system is reduced from 10.3-11.5 to 7.2-8.0, and meanwhile, the 3d compressive strength is improved by more than 60% by virtue of the hydration promotion effect of the superfine slag powder, so that the technical contradiction of low alkalinity and high gelatinization activity is thoroughly solved.

Inventors

  • HE GUOKAI
  • HE LIGANG
  • ZOU JING
  • SHI PIAN
  • CHEN WEIWEN
  • PAN ZHIGUO
  • CHEN YOUSHUN
  • FENG LU
  • WANG LIZHANG
  • SHI XIA

Assignees

  • 湖北海力环保科技股份有限公司

Dates

Publication Date
20260512
Application Date
20251231

Claims (10)

  1. 1. The low-alkalinity phosphogypsum composite heavy metal curing agent is characterized by comprising, by mass, 5-8 parts of low-alkalinity gelling agent, 3-6 parts of activated crystal form regulator, 2-5 parts of chelating dispersant, 3-7 parts of strengthening chelating agent, 6-10 parts of high-efficiency adsorbent and 63-84 parts of carrier; The low-alkali cementing material is a mixture composed of CA-50 aluminate cement, superfine slag powder and metakaolin according to the mass ratio of 2:3:2; the activated crystal form regulator is a mixture composed of tributyl phosphate and absolute ethyl alcohol according to the mass ratio of 1:1; the chelating dispersant is a mixture composed of polyepoxysuccinic acid and amino trimethylene phosphonic acid according to the mass ratio of 3:2; The strengthening chelating agent is a mixture composed of sodium dimethyl dithiocarbamic acid and sodium trithiocarbonate according to the mass ratio of 1-4:1; the efficient adsorbent is a mixture composed of hydrochloric acid activated diatomite and superfine slag powder according to the mass ratio of 2:1, or a mixture composed of iron modified diatomite and superfine slag powder according to the mass ratio of 7:3; The carrier is pretreated phosphogypsum.
  2. 2. The low-alkalinity phosphogypsum composite heavy metal curing agent according to claim 1, wherein the alkali content of the CA-50 aluminate cement is less than or equal to 0.5%, the specific surface area of the superfine slag powder is more than or equal to 500m2/kg, and the activity index of metakaolin is more than or equal to 95%.
  3. 3. The low-alkalinity phosphogypsum composite heavy metal curing agent of claim 1, wherein the polyepoxysuccinic acid has a molecular weight of 1000-3000.
  4. 4. The method for preparing the low-alkalinity phosphogypsum composite heavy metal curing agent according to any one of claims 1 to 3, which is characterized by comprising the following steps: Mixing phosphogypsum and water according to a liquid-solid ratio of 3-4:1, uniformly stirring, filtering, calcining a filter cake at 550-600 ℃ for 1.5 hours, and ball-milling a calcined product to 200 meshes of fineness to obtain pretreated phosphogypsum; mixing diatomite and hydrochloric acid according to a liquid-solid ratio of 5:1, stirring and activating under water bath heating, filtering, washing a filter cake to be neutral, drying, mixing with superfine slag, ball milling to 300 meshes of fineness, and preparing the efficient adsorbent, or mixing diatomite and ferric chloride solution according to a liquid-solid ratio of 5:1, stirring and activating under water bath heating, filtering, washing the filter cake to be neutral, drying, mixing with superfine slag, ball milling to 300 meshes of fineness, and preparing the efficient adsorbent; Dry-mixing the chelating dispersant and the intensified chelating agent uniformly to obtain a compound chelating agent; firstly, uniformly stirring and mixing the pretreated phosphogypsum and the low-alkali cementing material, then sequentially adding an activated crystal form regulator, a composite chelating agent and a high-efficiency adsorbent, and fully stirring after each addition to finally obtain a mixture; and (3) carrying out vacuum drying on the mixture, and carrying out jet milling and grinding to 350-400 meshes to obtain the low-alkalinity phosphogypsum composite heavy metal curing agent.
  5. 5. The method for preparing a low alkalinity phosphogypsum composite heavy metal curing agent according to claim 4, wherein in the preparation step of the efficient adsorbent, the hydrochloric acid concentration is 3wt%, the temperature of the water bath addition is 60+ -5 ℃, the stirring rate of stirring activation is 200r/min, the drying temperature is 105+ -5 ℃, the drying time is 4h, and/or When activated by ferric chloride, the concentration of the ferric chloride solution is 0.2mol/L, the heating temperature of the water bath is 60+/-5 ℃, the stirring speed of stirring and activation is 200r/min, the drying temperature is 105+/-5 ℃, and the drying time is 4 hours.
  6. 6. The method for preparing a low-alkalinity phosphogypsum composite heavy metal curing agent according to claim 4, wherein in the step of preparing the mixture, the activated crystal form modifier is added within 5-8 min.
  7. 7. The method for preparing a low-alkalinity phosphogypsum composite heavy metal curing agent according to claim 4, wherein in the step of preparing the low-alkalinity phosphogypsum composite heavy metal curing agent, the vacuum drying temperature is 60 ℃ and the vacuum degree is-0.08 MPa.
  8. 8. The application of the low-alkalinity phosphogypsum composite heavy metal curing agent in preparing roadbed materials according to any one of claims 1-3.
  9. 9. The use according to claim 8, wherein the mixing amount of phosphogypsum in the roadbed material is more than or equal to 80%.
  10. 10. The application of claim 9, wherein the addition amount of the low-alkalinity phosphogypsum composite heavy metal curing agent is 8-12 wt% of the phosphogypsum doping amount in the roadbed material.

Description

Low-alkalinity phosphogypsum composite heavy metal curing agent and preparation method and application thereof Technical Field The invention belongs to the technical field of phosphogypsum harmlessness, and particularly relates to a low-alkalinity phosphogypsum composite heavy metal curing agent, a preparation method and application thereof. Background Phosphogypsum is a large amount of industrial byproducts generated in the wet-process phosphoric acid production process, and about 4-5 tons of phosphogypsum is generated per 1 ton of phosphoric acid produced. Heavy metal ions (such as Cd, pb, cr, as and the like) and soluble phosphorus and fluorine contained in phosphogypsum can cause soil and water pollution by leaching, and if the phosphogypsum is directly piled up or simply treated, the soil and underground water are easily polluted by leaching of rainwater, so that huge environmental hidden trouble is formed. To reduce the effect of impurities on phosphogypsum performance, pretreatment is needed. However, although the water washing method can remove impurities, the water washing method has high cost, high energy consumption and secondary pollution, and is not suitable for large-scale application. Biological and adsorption processes also face the practical problems of high cost and low efficiency. Meanwhile, the low utilization rate (less than 40%) of phosphogypsum has become a core bottleneck for restricting green transformation in the phosphorus chemical industry. In the existing phosphogypsum heavy metal curing technology, traditional curing agents such as cement, lime and the like are mostly adopted, but the problems of expansion, heavy metal dissolution risk and the like caused by a high-alkali environment exist. The curing agent is dependent on a single chelating agent or a high-alkali gelation system, and has the defects of low pertinence of heavy metal curing, uneven curing efficiency of complex multi-component heavy metal, easiness in causing the pH value of a cured body to exceed the standard and causing alkali aggregate reaction in building material application due to high-alkali components, disordered self crystal form of phosphogypsum, insufficient mechanical strength after curing and limitation of high-value utilization of phosphogypsum, and poor bonding stability of the chelating agent and heavy metal ions and high long-term leaching risk. Therefore, development of a composite curing agent which has low alkalinity and can efficiently cure heavy metals in phosphogypsum is imperative. Disclosure of Invention Aiming at the defects of the prior art, the invention aims to provide a low-alkalinity phosphogypsum composite heavy metal curing agent, and a preparation method and application thereof. The invention integrates all components in a synergistic way, develops a composite curing agent with low alkalinity, high strength and high stability, and solves the bottleneck of the prior art. The aim of the invention is achieved by the following technical scheme: The low-alkalinity phosphogypsum composite heavy metal curing agent comprises, by mass, 5-8 parts of low-alkalinity gelling agent, 3-6 parts of activated crystal form regulator, 2-5 parts of chelating dispersant, 3-7 parts of enhanced chelating agent, 6-10 parts of efficient adsorbent and 63-84 parts of carrier; The low-alkali cementing material is a mixture composed of CA-50 aluminate cement, superfine slag powder and metakaolin according to the mass ratio of 2:3:2; The activated crystal form regulator is a mixture composed of tributyl phosphate (TBP) and absolute ethyl alcohol according to the mass ratio of 1:1; The chelating dispersant is a mixture of polyepoxysuccinic acid (PESA) and amino trimethylene phosphonic Acid (ATMP) according to the mass ratio of 3:2; the strengthening chelating agent is a mixture composed of sodium dimethyl dithiocarbamic acid and sodium trithiocarbonate (TTC-Na) according to the mass ratio of 1-4:1; the efficient adsorbent is a mixture composed of hydrochloric acid activated diatomite and superfine slag powder according to the mass ratio of 2:1, or a mixture composed of iron modified diatomite and superfine slag powder according to the mass ratio of 7:3; The carrier is pretreated phosphogypsum. Preferably, the alkali content of the CA-50 aluminate cement is less than or equal to 0.5 percent, the specific surface area of the superfine slag powder is more than or equal to 500m <2 >/kg, and the activity index of the metakaolin is more than or equal to 95 percent. Preferably, the molecular weight of the polyepoxysuccinic acid is 1000-3000. In the invention, the low-alkali cementing material has low alkali characteristic and high gelation activity, aluminate cement provides early strength, superfine slag powder improves compactness through micro aggregate effect and hydration gelation, metakaolin exerts pozzolanic activity to generate stable hydration product, the pH of the system can be stabilized at 7.2-8.0, and me