A solidification treatment method for hazardous waste containing high-arsenic sulfide slag

Abstract

This invention belongs to the technical field of safe solidification treatment of hazardous solid waste, specifically disclosing a solidification treatment method for high-arsenic arsenic sulfide slag hazardous waste: 1) Pretreatment and pH adjustment of high-arsenic arsenic sulfide slag. Using high-arsenic arsenic sulfide slag produced by sulfidation of arsenic-containing wastewater from smelting as raw material, the arsenic sulfide slag is pretreated with a pH adjuster to approximately pH 5-7; 2) Stabilization and arsenic solidification treatment of high-arsenic arsenic sulfide slag. The stabilizer, adsorbent, additive, and gelling material of the pretreated arsenic sulfide slag are weighed according to the ratio, and after initial mixing and forced stirring, the mixture is fully reacted for about 1 hour. The amount of reagents added is adjusted according to the arsenic content; 3) Solidification and coating of high-arsenic arsenic sulfide slag. A solidifying agent is added, and the mixture is forcibly stirred, extruded, and pressed into a solidified body. It is then naturally cured for 3 days. A toxicity leaching test is conducted according to GB5085.3-2007. If the arsenic and heavy metal ion leaching of the solidified body is less than the relevant standard requirements, it can be stockpiled or landfilled.

Description

Technical Field

[0001] This invention belongs to the field of safe solidification treatment technology for hazardous solid waste, specifically relating to a solidification treatment method for hazardous waste containing high-arsenic sulfide slag. Background Technology

[0002] Arsenic is mostly found in various metal ores as sulfides, occurring in varying concentrations. In non-ferrous metallurgical processes, large quantities of arsenic-containing wastewater and arsenic-containing dust are generated. The arsenic-containing wastewater, after sulfidation treatment, produces a large amount of arsenic sulfide slag. In addition to arsenic, arsenic sulfide slag also contains various heavy metal ions such as copper, lead, and chromium. It is classified as hazardous solid waste and must undergo harmless treatment to ensure safe landfill disposal.

[0003] Currently, there are two main methods for treating arsenic sulfide slag: 1. Arsenic slag stabilization and solidification for landfilling. This involves using one or more processes to incorporate suitable solidifying agents and chemical additives into the solid waste, transforming the toxic and hazardous waste into a more physically and chemically stable substance, thus meeting national standards for stabilization and solidification for landfilling. Commonly used stabilization / solidification technologies both domestically and internationally include cement solidification, organic polymer solidification, plastic material solidification, and melt solidification; 2. Arsenic extraction and resource utilization. Extracting and recovering arsenic from arsenic sulfide slag for resource utilization is challenging, complex, and requires significant investment. Therefore, the non-ferrous metals industry and solid waste treatment industry primarily use the former method of stabilization and solidification for harmless treatment.

[0004] Currently, with the continuous development of the smelting industry, the supply of high-quality, low-arsenic metal ores is clearly insufficient. The proportion of high-arsenic metal ores used is also increasing with the continuous advancement of smelting technology, resulting in a continuous increase in the amount of high-arsenic slag produced. The problems of using traditional stabilization treatment technology have become increasingly prominent, mainly including: 1. A significant increase in reagent usage, even reaching several times that of arsenic slag; 2. A significant increase in the amount of stabilized and solidified slag produced, reducing the service life of the landfill; 3. A significant increase in landfill costs. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings in the stabilization and solidification treatment of high-arsenic sulfide slag by providing a simple and low-cost technology for stabilizing and solidifying high-arsenic sulfide slag. This technology achieves efficient and stable treatment of arsenic-removed sulfide slag, enabling safe storage or landfilling and solving the environmental pollution problem caused by arsenic sulfide slag.

[0006] A method for solidification treatment of hazardous waste containing high-arsenic sulfide slag, the specific steps of which are as follows:

[0007] (1) Using high-arsenic sulfide slag produced by sulfidation of arsenic-containing wastewater as raw material, the high-arsenic sulfide slag and pH adjuster are reacted solid-solid for 0.5 h at a mass ratio of 1:0.15 to 0.2, and the pH is controlled to about 5-7 to obtain pretreated high-arsenic sulfide slag.

[0008] (2) Add arsenic-fixing and stabilizing agents such as stabilizers, adsorbents, additives, and gelling materials to the pretreated high-arsenic sulfide slag, mix and control the moisture content of the mixture to 16-22 wt%, wherein the stabilizer is 45-60% of the high-arsenic sulfide slag, the adsorbent is 4-10% of the high-arsenic sulfide slag, the gelling material is 5-10% of the high-arsenic sulfide slag, and the additive is 10-20% of the gelling material;

[0009] (3) Place the mixed materials from step (2) into a closed forced high-speed mixer to carry out forced mixing and reaction between the materials. The reaction time is controlled at about 1 hour to achieve full reaction and homogenization between the materials.

[0010] (4) Add curing agent to the uniform material in step (3) according to the proportion and stir at high speed. Control the reaction time to about 0.5h. Extrude by continuous kneading extruder, cut into test blocks of a certain size, cure naturally for 3 days, and conduct toxicity leaching test according to GB5085.3-2007. The arsenic and heavy metal ion leaching of the solidified body is less than the relevant standard requirements, and it can be stacked and landfilled.

[0011] Furthermore, the high-arsenic sulfide slag is a high-arsenic acidic wastewater generated during copper smelting, lead-zinc smelting, and pyrite-to-acid production processes. It is formed by sulfidation and heavy metal removal processes and is characterized by high arsenic content and varying amounts of heavy metals. It is classified as hazardous solid waste.

[0012] Furthermore, the pH adjuster is one or more of limestone, magnesite, and quicklime, and the limestone powder, magnesite powder, and quicklime powder are all industrial grade and have a fineness greater than 80 mesh.

[0013] Furthermore, the stabilizer is one or more of ferrous sulfate, ferric chloride, ferric sulfate, limestone powder, quicklime powder, and magnesium oxide powder, wherein the fineness of the ferrous sulfate, ferric chloride, ferric sulfate, limestone powder, and quicklime powder is greater than 80 mesh.

[0014] Furthermore, the adsorbent is one or more of PAC, PFS, and activated clay, and all of PAC, PFS, and activated clay are industrial grade.

[0015] Furthermore, the gel material is one or more of dispersible adhesive powder, cellulose, gelatin, instant silicate, and potassium methylsilicate, and the dispersible adhesive powder, cellulose, gelatin, instant silicate, and potassium methylsilicate are all industrial grade.

[0016] Furthermore, the additive is either a PAM cation or an anion, and both the PAM cation and anion are industrial grade.

[0017] Furthermore, the curing agent is industrial-grade ordinary silicate cement.

[0018] The main technical solutions in this invention are: 1) pH adjustment of high-arsenic sulfide slag pretreatment. High-arsenic sulfide slag produced from the sulfidation of arsenic-containing wastewater is used as raw material. The sulfide slag is pretreated with a pH adjuster to approximately pH 5-7; 2) Arsenic stabilization and solidification treatment of high-arsenic sulfide slag. Stabilizer, adsorbent, additives, and gelling material of the pretreated sulfide slag are weighed according to the specified ratio, initially mixed, and forcibly stirred to react fully for about 1 hour. The amount of reagents added is adjusted according to the arsenic content; 3) Solidification and coating of high-arsenic sulfide slag. A solidifying agent is added, and the mixture is forcibly stirred, extruded, and pressed into a solidified body. It is then naturally cured for 3 days. A toxicity leaching test is conducted according to GB5085.3-2007. If the arsenic and heavy metal ion leaching of the solidified body is less than the relevant standard requirements, it can be stockpiled or landfilled.

[0019] Advantages and technical effects of this invention:

[0020] 1. The high-concentration sulfide arsenic removal slag stabilization and solidification treatment method of the present invention involves pretreatment to neutralize the acidic high-arsenic slag, followed by efficient stirring and stabilization agent to fully react and solidify arsenic. The synergistic effect among the components of the agent is significant, effectively fixing arsenic in the high-concentration sulfide arsenic removal slag. Finally, a cement solidification agent is used to solidify and form blocks of the stabilized arsenic-fixed slag. The leaching concentration of the treated high-concentration sulfide arsenic removal slag is less than 2.5 mg / L.

[0021] 2. This invention employs a dual-stabilization solidification coating technology. First, a stabilizing agent is used to effectively fix and chemically coat the arsenic in the high-concentration sulfide arsenic removal slag. Then, a cement curing agent is used to further solidify and form the stabilized arsenic-fixed slag into blocks. Compared with existing agents for treating high-arsenic slag, this method uses less reagent and produces less treated slag, significantly increasing the service life of the landfill plant.

[0022] 3. The high-concentration sulfide arsenic removal slag agent of the present invention is neutral, and the iron arsenate, aluminum arsenate and calcium arsenate generated during the stabilization process can exist stably, and have a good arsenic removal effect. It has the advantages of simple equipment, convenient operation and easy industrialization.

[0023] 4. The solidified block prepared by this invention has strong weather resistance and corrosion resistance, and can be treated by traditional stacking and landfill methods. Detailed Implementation

[0024] The present invention will be further described in detail below through embodiments, but the scope of protection of the present invention is not limited to the content described.

[0025] Example 1:

[0026] 1. Raw materials and raw material pretreatment

[0027] (1) The main elemental composition of the arsenic removal slag from the arsenic-containing wastewater of a copper smelting plant is shown in Table 1.

[0028] Element name Cu% Ni% Pb% Zn% Cd% As% content 7.43 0.086 0.51 0.12 1.31 35.42

[0029] (2) Preparation of pH adjuster for high arsenic sulfide slag: Limestone, magnesite and quicklime raw materials are mixed in a ratio of 6:2:1 and ball milled. The particle size requirement is that the residue on a 180-mesh square hole sieve is less than 5wt%.

[0030] (3) Pretreatment of high arsenic sulfide slag: The dry base of high arsenic sulfide slag and pH adjuster are stirred in a mixer at a mass ratio of 1:0.15. The solid-solid reaction time is controlled at 0.5h and the pH is controlled at about 5-7 to obtain pretreated high arsenic sulfide slag.

[0031] 2. Stabilization and Arsenic Fixation of High-Arsenic Sulfide Slag

[0032] (1) Preparation of high arsenic sulfide slag stabilizer: Mix ferric chloride, ferrous sulfate, limestone and magnesium oxide powder in a certain proportion and set aside for use;

[0033] (2) Preparation of high arsenic sulfide slag adsorbent: PAC, PFS and activated clay are mixed evenly in a certain proportion and set aside for use.

[0034] (3) Preparation of high arsenic sulfide arsenic slag gel material: DDR adhesive powder, cellulose and fast-dissolving sodium silicate are mixed evenly in a certain proportion and set aside for use.

[0035] (4) PAM cationic admixture is selected.

[0036] Take 50g of wet high-arsenic sulfide slag (35g dry basis) with an analysis showing a moisture content of 30wt%. Add 25g of stabilizer, 3g of adsorbent, 4g of gelling material, and 0.5g of additive. Force mix and react the materials in a closed, high-speed mixer for approximately 1 hour to ensure thorough homogenization and reaction.

[0037] 3. Solidification and coating of high-arsenic sulfide arsenic slag

[0038] Add 5g of 42.5% silicate cement to the fully reacted stabilized arsenic-fixed material and force-mix and react it in a high-speed mixer for about 0.5 hours. The homogeneous material is then extruded by a continuous kneading extruder, cut into test blocks of a certain size, and naturally cured for 3 days.

[0039] The test specimens were subjected to leaching analysis for relevant toxic substances according to B5085.3-2007. The leaching concentration of arsenic ions was 2.3 mg / L, which is lower than the control limit for hazardous waste allowed to enter landfill areas in the "Standard for Pollution Control of Hazardous Waste Landfill", which is less than 2.5 mg / L.

[0040] Example 2:

[0041] 1. Raw materials and raw material pretreatment

[0042] (1) The main elemental composition of the arsenic removal slag from the arsenic-containing wastewater of a copper smelting plant is shown in Table 1.

[0043] Element name Cu% Ni% Pb% Zn% Cd% As% content 8.43 0.091 0.57 0.11 1.51 38.21

[0044] (2) Preparation of pH adjuster for high arsenic sulfide slag: Limestone, magnesite and quicklime raw materials are mixed in a ratio of 5:3:2 and ball milled. The particle size requirement is that the residue on a 180-mesh square hole sieve is less than 5wt%.

[0045] (3) Pretreatment of high arsenic sulfide slag: The dry base of high arsenic sulfide slag and pH adjuster are stirred in a mixer at a mass ratio of 1:0.17. The solid-solid reaction time is controlled at 0.5h and the pH is controlled at about 5-7 to obtain pretreated high arsenic sulfide slag.

[0046] 2. Stabilization and Arsenic Fixation of High-Arsenic Sulfide Slag

[0047] (1) Preparation of high-arsenic sulfide slag stabilizer: Mix ferrous sulfate, ferric chloride and quicklime powder in a certain proportion and set aside for use;

[0048] (2) Preparation of high arsenic sulfide slag adsorbent: PAC, PFS and activated clay are mixed evenly in a certain proportion and set aside for use.

[0049] (3) Preparation of high arsenic sulfide arsenic slag gel material: DDR adhesive powder, cellulose and fast-dissolving sodium silicate are mixed evenly in a certain proportion and set aside for use.

[0050] (4) PAM cationic admixture is selected.

[0051] Take 50g of wet high-arsenic sulfide slag (35g dry basis, analysis showed a moisture content of 32wt%), add 28g of stabilizer, 3.5g of adsorbent, 4.5g of gelling material, and 0.6g of additive. Force mix and react the materials in a closed, high-speed mixer for approximately 1 hour to achieve thorough homogenization and reaction.

[0052] 3. Solidification and coating of high-arsenic sulfide arsenic slag

[0053] Add 5g of 42.5% silicate cement to the fully reacted stabilized arsenic-fixed material and force-mix and react it in a high-speed mixer for about 0.5 hours. The homogeneous material is then extruded by a continuous kneading extruder, cut into test blocks of a certain size, and naturally cured for 3 days.

[0054] The test blocks were subjected to leaching analysis for relevant toxic substances according to B5085.3-2007. The leaching concentration of arsenic ions was 2.2 mg / L, which is lower than the control limit for hazardous waste allowed to enter the landfill area in the "Standard for Pollution Control of Hazardous Waste Landfill", which is less than 2.5 mg / L.

Claims

1. A method for solidification treatment of hazardous waste containing high-arsenic sulfide slag, characterized in that, The specific steps of the method are as follows: (1) Using high-arsenic sulfide slag produced by sulfidation of arsenic-containing wastewater as raw material, the high-arsenic sulfide slag and pH adjuster are reacted in a solid-solid reaction for 0.5 h at a mass ratio of 1:0.15 to 0.2, and the pH is controlled to about 5-7 to obtain pretreated high-arsenic sulfide slag; the pH adjuster is one or more of limestone powder, magnesite powder, and quicklime powder, and the limestone powder, magnesite powder, and quicklime powder are all industrial grade and have a fineness greater than 80 mesh. (2) Add an arsenic-fixing stabilizing agent to the pretreated high-arsenic sulfide slag, mix and control the moisture content of the mixture to 16-22 wt%. The arsenic-fixing stabilizing agent includes a stabilizer, an adsorbent, an additive, and a gelling material. The stabilizer accounts for 45-60% of the high-arsenic sulfide slag, the adsorbent accounts for 4-10% of the high-arsenic sulfide slag, the gelling material accounts for 5-10% of the high-arsenic sulfide slag, and the additive accounts for 10-20% of the gelling material. The stabilizer is one or more of ferrous sulfate, ferric chloride, ferric sulfate, limestone powder, quicklime powder, and magnesium oxide powder. The fineness of ferrous sulfate, ferric chloride, ferric sulfate, limestone powder, and quicklime powder is greater than 80 mesh; the adsorbent is one or more of PAC, PFS, and activated clay, wherein PAC, PFS, and activated clay are all industrial grade; the gel material is one or more of dispersible colloid powder, cellulose, gelatin, readily soluble silicate, and potassium methylsilicate, wherein dispersible colloid powder, cellulose, gelatin, readily soluble silicate, and potassium methylsilicate are all industrial grade; the additive is one of PAM cation or PAM anion, wherein both PAM cation and PAM anion are industrial grade. (3) Put the mixed materials from step (2) into a closed forced high-speed mixer to carry out forced mixing and reaction between the materials. The reaction time is controlled at about 1 hour to achieve full reaction and homogenization between the materials. (4) Add curing agent to the homogenized material in step (3) according to the proportion and stir at high speed. The reaction time is controlled at about 0.5h. The material is extruded by a continuous kneading extruder, cut into test blocks of a certain size, and naturally cured for 3 days. The curing agent is industrial grade ordinary silicate cement.

2. The solidification treatment method for hazardous waste containing high-arsenic sulfide slag according to claim 1, characterized in that: The high-arsenic sulfide slag is formed from high-arsenic acidic wastewater generated during copper smelting, lead-zinc smelting, and sulfuric acid production from pyrite, through a sulfidation and heavy metal removal process.