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CN-122010361-A - Heterogeneous crystallization and anti-competitive adsorption coupled deep defluorination process

CN122010361ACN 122010361 ACN122010361 ACN 122010361ACN-122010361-A

Abstract

The invention relates to the technical field of water treatment, in particular to a heterogeneous crystallization and anti-competitive adsorption coupled deep defluorination process. According to the process, an initial calcium adding liquid and a citrate modifying liquid are sequentially added into fluorine-containing wastewater, the pH value of a system is regulated in stages, a secondary calcium adding liquid and a tertiary calcium supplementing liquid are sequentially added, mixing, standing and separating are carried out, then HC unit effluent and bottom sediment are obtained, supernatant liquid is discarded after the bottom sediment is resuspended and standing and separated, and seed crystal wet pulp is obtained, and deep defluorination is carried out on the HC unit effluent. The method can improve the heterogeneous nucleation order of the surface of the calcium fluoride seed crystal, obtain the seed crystal with concentrated granularity and excellent sedimentation performance, provide favorable water inlet conditions of low suspended matters and low residual calcium for the subsequent adsorption units, and realize stable deep defluorination of the fluorine-containing wastewater.

Inventors

  • GE XIANGYANG
  • LIU DONG
  • Xing Xiangfu
  • MAO YONGXIAN
  • HU QINGWEI

Assignees

  • 安徽泓济环境科技有限公司

Dates

Publication Date
20260512
Application Date
20260409

Claims (9)

  1. 1. A heterogeneous crystallization and anti-competitive adsorption coupled deep defluorination process is characterized by comprising the following steps of sequentially adding an initial calcium adding solution, a citrate modifying solution and a sodium hydroxide solution and a glacial acetic acid solution into a system to adjust the pH of the system, then adding a secondary calcium adding solution and a tertiary calcium supplementing solution, mixing, standing and separating to obtain HC unit effluent and bottom sediment, and discarding supernatant fluid after resuspension and standing and separation of the bottom sediment to obtain seed crystal wet slurry; the initial calcium adding liquid is calcium chloride aqueous solution, and the adding amount of calcium chloride in the initial calcium adding liquid is 0.72-0.76g based on 1000g of the total weight of the fluorine-containing wastewater; The secondary calcium adding liquid is calcium chloride aqueous solution, and the adding amount of calcium chloride in the secondary calcium adding liquid is 0.20-0.24g based on 1000g of the total weight of the fluorine-containing wastewater; The tertiary calcium supplementing liquid is calcium chloride aqueous solution, and the total weight of the fluorine-containing wastewater is 1000g, and the adding amount of calcium chloride in the tertiary calcium supplementing liquid is 2.25-2.31g; The citrate modified solution is sodium citrate aqueous solution, and the adding amount of sodium citrate in the citrate modified solution is 0.16-0.20g based on 1000g of the total weight of fluorine-containing wastewater.
  2. 2. The deep fluorine removal process of claim 1, wherein the fluorine-containing wastewater is derived from a wafer etching and cleaning process in the semiconductor, photovoltaic industry or a hydrofluoric acid etching and sanding process in the glass manufacturing industry.
  3. 3. The deep defluorination process according to claim 1, wherein the initial calcium solution is added within 18-22s, and the stirring is maintained for 1.5-2.5min after the addition is completed.
  4. 4. The deep defluorination process according to claim 1, wherein the stirring is maintained for 0.8-1.2min after the citrate modification solution is added.
  5. 5. The deep defluorination process according to claim 1, wherein the sodium hydroxide solution is added to adjust the pH of the system to 4.7-4.9.
  6. 6. The deep defluorination process according to claim 1, wherein the glacial acetic acid solution is added to adjust the pH of the system to 4.4-4.6.
  7. 7. The deep defluorination process according to claim 1, wherein the secondary calcium solution is added within 12-18s, and stirring is maintained for 2.5-3.5min after the addition.
  8. 8. The deep defluorination process according to claim 1, wherein the sodium hydroxide solution is added simultaneously during the three calcium supplement liquid additions and within 2.5-3.5min after the addition is completed to adjust the system pH to be maintained at 5.8-6.1.
  9. 9. The deep defluorination process according to claim 1, wherein the defluorination filler is obtained by using Lewatit MonoPlus TP 260,260 as matrix resin and preloading the matrix resin with zirconium salt solution.

Description

Heterogeneous crystallization and anti-competitive adsorption coupled deep defluorination process Technical Field The invention relates to the technical field of water treatment, in particular to a heterogeneous crystallization and anti-competitive adsorption coupled deep defluorination process. Background Fluorine-containing wastewater is widely generated in the fields of semiconductor manufacturing, photovoltaic industry, metal smelting, electroplating, chemical production and the like. If the fluoride ions are discharged to natural water without effective treatment, ecological balance can be destroyed, soil and underground water pollution can be caused, serious damage to bones and teeth of a human body can be caused by enrichment of food chains, and diseases such as fluoriosis and the like can be even caused. With the increasingly strict requirements of the nation on environmental protection, the limit value of the concentration of the fluoride ions in the industrial wastewater discharge standard is generally increased to be below 1.0 mg/L. Therefore, developing efficient, stable and economical deep fluorine removal technology has become a critical issue to be addressed in the related industry. At present, a chemical precipitation method is a common method for treating high-concentration fluorine-containing wastewater, and fluorine ions are separated from a liquid phase in the form of calcium fluoride by adding a precipitant such as calcium salt to the wastewater. However, the traditional precipitation method has obvious limitations that most of calcium fluoride precipitates generated by the traditional precipitation method are amorphous or fine crystals, the sedimentation performance is poor, the solid-liquid separation is difficult, and a large amount of suspended matters are often carried in the effluent, so that the fluoride ions are secondarily out of standard. In order to improve the treatment effect, calcium salt is often excessively added in engineering, but new calcium ion pollution is introduced, and the subsequent treatment cost and the sludge yield are increased. To overcome the deficiencies of homogeneous precipitation, techniques of induced crystallization (or heterogeneous crystallization) have evolved. According to the technology, seed crystals are added into a reaction system to provide a nucleation and growth carrier for calcium fluoride, so that precipitates epitaxially grow by taking the seed crystals as a core, and crystals with larger, denser and easier sedimentation are formed. However, the existing induced crystallization process still faces a series of challenges in practice, on one hand, the active sites on the surface of the seed crystal are limited, and as the number of times of recycling increases, the surface of the seed crystal can be covered by heterogeneous sediments, the activity gradually decreases, so that the fluorine removal efficiency is reduced, the seed crystal needs to be frequently updated, and the running cost is increased. In addition, the single crystallization process often has difficulty in stably reducing the concentration of the fluorine ions in the effluent to below 1.0mg/L, and is usually required to be combined with an advanced treatment unit such as adsorption. However, residual calcium ions, suspended particles and incompletely precipitated fluorinated colloid in the conventional crystallization effluent are very easy to block the pore canal of the adsorbent or occupy the active site of the adsorbent, so that the adsorption capacity is rapidly reduced, the regeneration is frequent, and the operation cost is high. Therefore, how to prepare the calcium fluoride crystal seed with excellent sedimentation performance, high surface activity and strong cycle stability through fine process regulation and control, and enable the calcium fluoride crystal seed to be efficiently cooperated with a subsequent advanced treatment unit is a technical problem which exists in the field for a long time but is not solved effectively. Disclosure of Invention Therefore, the invention aims to provide a heterogeneous crystallization and anti-competitive adsorption coupled deep defluorination process, which aims to solve the problems of low defluorination efficiency, difficult solid-liquid separation and difficult high-efficiency synergy with deep treatment caused by insufficient regulation and control of seed crystal surface activity and poor particle stability in the existing induced crystallization process. Based on the above object, the invention provides a heterogeneous crystallization and anti-competitive adsorption coupled deep defluorination process, comprising the following steps: Sequentially adding an initial calcium adding liquid and a citrate modifying liquid into fluorine-containing wastewater, sequentially adding a sodium hydroxide solution and a glacial acetic acid solution into a system to adjust the pH of the system, then adding a secondary calcium adding li