Wet-dispersed cement chrome removal agents and wet dispersants and methods for their preparation

Abstract

A wet dispersible cement chromium removal agent, raw material components of which include: 5-10 parts of wet dispersible agent, 30-50 parts of reducing agent B, 20-30 parts of reducing agent C, 1-3 parts of emulsifier, 2-5 parts of antioxidant, and the balance is water. The wet dispersible agent is a finished product, raw material components of which include: 300-340 parts of epoxide, 30-60 parts of alcohol small monomer, 0.1-0.3 parts of catalyst, 13-20 parts of acid small monomer, 5-8 parts of sulfonic acid small monomer, 2-6 parts of oxidizing agent, 0.6-1.2 parts of reducing agent A, 2-3 parts of chain transfer agent, 10-15 parts of neutralizing agent, and the balance is water. The wet dispersible agent contained in the chromium removal agent not only has good wetting effect, but also has good dispersing splitting effect, so that the chromium removal agent can better penetrate into the interior of cement particles.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of cement admixtures, and relates to a wet dispersing type cement chromium removal agent and a wet dispersing agent and a preparation method thereof. BACKGROUND

[0002] Cement, as one of the most commonly used building materials in modern construction, is irreplaceable. As a powdery inorganic cementitious material, cement can be hardened in air or in water after being stirred with water, and can firmly cement sand, stone and other materials together. Cement is a resource-based material, which is mainly obtained by calcining cement clinker prepared from lime raw materials, clay raw materials and a small amount of correction raw materials after being ground into powder in a certain proportion. In the whole process of cement production, the dependence on resources is very high. With the rational control of ecological resources and the strict requirements on environmental protection by the state, the resources available for cement production are becoming increasingly scarce. Therefore, various materials with certain performance defects and construction waste are gradually used in cement production, which may also cause some control indicators in cement to exceed the standard. However, in order to build a new environmentally friendly society, waste recycling is also a trend of energy utilization.

[0003] Water-soluble hexavalent chromium is a heavy metal that is harmful to human health and the environment, and can be easily absorbed by the human body through the skin or the gastrointestinal tract. Long-term contact of the skin with chromium compounds can cause contact dermatitis or eczema. Chromium is widely distributed in the earth's crust, and hexavalent chromium and trivalent chromium are common valence states in nature. Hexavalent chromium is also a highly toxic carcinogen, which is the main reason for the toxicity of chromium. Hexavalent chromium has strong oxidizing properties, and when the content of hexavalent chromium in cement exceeds a certain level, it can cause strong corrosion of the skin of cement operators, resulting in skin burns and ulcers. According to a survey by the U.S. Environmental Protection Agency on 2357 workers exposed to chromate from 1950 to 1974, long-term exposure to hexavalent chromium increased the risk of lung cancer. There is a certain correlation between hexavalent chromium and the occurrence of gastric cancer. In addition, hexavalent chromium can interact with DNA, affecting normal cell metabolism and causing DNA damage or mutation. Furthermore, cement products will inevitably come into contact with water, soil and other media during use or after being discarded. Hexavalent chromium in cement products dissolves in water through rain, then enters surface water or seeps into the ground, polluting water sources and soil, and even causing the surrounding ecological environment to be unable to recover for decades. Therefore, hexavalent chromium in cement and its products not only seriously threatens the health of operators, but also potentially affects the ecological environment of human life.

[0004] Sources of hexavalent chromium in cement: (1) Cement raw materials, such as marl, limestone, clay, iron tailings, etc., often contain trace amounts of chromium. These chromium elements do not disappear during clinker calcination and grinding, and thus remain. (2) Chromium-containing crushing and grinding equipment. During the crushing of raw materials, grinding of raw meal and cement, chromium is introduced into cement products due to the wear of crushing and grinding media in chromium-containing equipment. (3) Chromium-containing refractory bricks. Due to the large-scale use of chromium-containing refractory bricks in the high-temperature zone of cement rotary kilns, under the conditions of high temperature, high wind pressure and high alkalinity of furnace charge in rotary kilns, chromium is oxidized and incorporated into clinker, resulting in water-soluble hexavalent chromium in cement clinker. (4) Industrial waste residue. The large-scale utilization of industrial waste residue has become an important way for the sustainable development of the cement industry. The use of chromium-containing waste as a substitute filler or raw material will inevitably bring chromium into cement products.

[0005] Therefore, hexavalent chromium reducing agents must be added during the cement manufacturing or use process in order to effectively control the hexavalent chromium content in cement.

[0006] Existing hexavalent chromium reducing agents mainly include ferrous salts, stannous salts, divalent manganese salts, sulfides, aldehydes, and slag. Ferrous sulfate is the most widely used due to its low price and significant reducing effect. However, it also has several drawbacks, such as weak binding of water of crystallization, affecting the reducing effect; easy oxidation and poor chemical stability; and the need for large dosages. Stannous sulfate has a better reducing effect than ferrous sulfate and better long-term stability, but its high cost limits its widespread use as a hexavalent chromium reducing agent. Currently, ferrous sulfate-based hexavalent chromium reducing agents offer the best cost-effectiveness.

[0007] Chinese patent application CN115231847A discloses a cement chromium removal agent and its preparation method. This invention provides a cement chromium removal agent and its preparation method, wherein the raw materials for the cement chromium removal agent, by weight, include: 0.1-1 parts emulsifier, 1-5 parts stabilizer, 10-30 parts reducing agent, 10-30 parts curing agent, and 30-60 parts water; the reducing agent is FeSO4·7H2O, and the curing agent is a mixture containing a trivalent aluminum salt compound and an organic acid. This invention uses ferrous sulfate as a base additive and adds other compounds in combination, thereby coupling the advantages of each component to obtain a composite chromium removal agent with good reduction effect, stable reduction ability, and reasonable cost. However, the chromium removal efficiency of this invention is limited; the chromium removal agent cannot penetrate into the interior of cement particles and can only act on the surface of cement particles, which will affect the chromium removal effect. In addition, the possibility of the hexavalent chromium content exceeding the standard in the later stage is relatively high with a single ferrous sulfate chromium removal agent.

[0008] Chinese patent application CN115259739A discloses a high-efficiency cement chromium removal agent and its preparation method. This invention discloses a high-efficiency cement chromium removal agent and its preparation method. It is composed of 30-40% reducing agent, 1-2% complexing agent, 1-2% dispersant, 4-8% reinforcing agent, and 10-20% grinding aid. The reducing agent is prepared from sodium hydroxide, ethanol solution, and ethyl nitrite. The high-efficiency cement chromium removal agent prepared by this invention has a wide range of applications, suitable for cements of various grades with excessive water-soluble hexavalent chromium; it has good durability and stability, can be used under different working conditions, and the hexavalent chromium content in cement does not change with the storage time of the cement after adding the chromium removal agent; it is cost-effective, has a guaranteed treatment effect, and is easy to operate; it is green and environmentally friendly, non-toxic, harmless, and a non-hazardous chemical, making it easy to store and transport; it is beneficial to improve the early and late strength of cement; and it is also beneficial to improve the grinding aid effect. However, the chromium removal agent prepared by this invention cannot wet and penetrate into the interior of cement particles, and therefore cannot completely remove hexavalent chromium from cement. Summary of the Invention

[0009] In view of the above-mentioned problems in the existing technology, the technical problem to be solved by the present invention is to provide a wetting and dispersing cement chromium removal agent.

[0010] Unlike the above patents, this invention prepares a wetting and dispersing cement chromium removal agent. The wetting and dispersing agent contained in the chromium removal agent prepared by this invention is a low molecular weight polymer synthesized through chemical structure design. It not only has a good wetting effect, which allows the chromium removal agent to better penetrate into the interior of cement particles, but also has a good dispersing and splitting effect, which improves the encapsulation effect of the chromium removal agent on cement particles. It has a strong dispersing effect on cement particles, and the combination of internal and external effects can achieve a thorough chromium removal effect.

[0011] This invention employs a two-step method to prepare a wetting and dispersing cement chromium removal agent.

[0012] The first step is to synthesize low molecular weight oligomers as wetting and dispersing agents. The total mass of raw materials is 1000 parts, of which the materials used to synthesize the oligomers include 300-340 parts of epoxide, 30-60 parts of alcohol monomers, 0.1-0.3 parts of catalyst, 13-20 parts of acid monomers, 5-8 parts of sulfonic acid monomers, 2-6 parts of oxidant, 0.6-1.2 parts of reducing agent A, 2-3 parts of chain transfer agent, 10-15 parts of neutralizing agent, and the remainder is water.

[0013] The second step involves mixing 5-10 parts of the synthesized wetting and dispersing agent, 30-50 parts of reducing agent B, 20-30 parts of reducing agent C, 1-3 parts of emulsifier, 2-5 parts of antioxidant, and the remainder being water, based on a total raw material mass of 100 parts. By combining optimized proportions and scientific feeding methods, a wetting and dispersing cement chromium removal agent is finally prepared.

[0014] Preferably, the epoxide is ethylene oxide.

[0015] Preferably, the alcohol monomer is one or more of methyl allyl alcohol, allyl alcohol, and isopentenol.

[0016] Preferably, the catalyst is one or more of sodium metal, sodium cyanide, sodium hydroxide, and potassium hydroxide.

[0017] Preferably, the acid monomer is one or more of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid.

[0018] Preferably, the sulfonic acid monomer is one or more of sodium methpropylene sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and sodium allyl sulfonate.

[0019] Preferably, the oxidant is one or more of hydrogen peroxide, ammonium persulfate, and azobisisobutyronitrile.

[0020] Preferably, the reducing agent A is one or more of vitamin C, sodium formaldehyde sulfoxylate, sodium sulfite, sodium metabisulfite, ferrous sulfate, and sodium dithionite.

[0021] Preferably, the chain transfer agent is one or more of mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol, mercaptothiol, sodium hypophosphite, and sodium methylpropenesulfonate.

[0022] Preferably, the neutralizing agent is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, and potassium hydroxide.

[0023] Preferably, the wetting and dispersing agent is a raw material synthesized in the first step.

[0024] Preferably, the reducing agent B is ferrous sulfate.

[0025] Preferably, the reducing agent C is one or more of sodium bisulfite, sodium metabisulfite, sodium thiosulfate, vitamin C, and sodium formaldehyde sulfoxylate.

[0026] Preferably, the emulsifier is one or more of nonylphenol polyoxyethylene ether and fatty alcohol polyoxypropylene ether.

[0027] Preferably, the antioxidant is vitamin C.

[0028] This invention can be achieved through the following technical solutions:

[0029] (1) Preparation of unsaturated intermediates

[0030] At room temperature, add 30–60 parts of alcohol monomers and 0.1–0.3 parts of catalyst to the reactor, start stirring, and evacuate the reactor to -0.07 MPa. After closing the vacuum valve, immediately add 80–100 parts of ethylene oxide to initiate the reaction, maintaining the reactor pressure (internal pressure) at 0–0.05 MPa while simultaneously raising the temperature. When the reactor pressure decreases and the temperature increases, it indicates that the reaction has been initiated, and the feed can be continuously and steadily increased, gradually and slowly raising the reactor pressure. During normal reaction, the reactor temperature (maximum temperature) should be controlled at 105±5℃, and the reactor pressure at 0.2–0.4 MPa.

[0031] The remaining 120–240 parts of ethylene oxide were added gradually, and the reaction was maintained at 110±5℃ for 1–1.5 hours. After maturation, the temperature was lowered to 100±5℃, the reactor was purged with N2 gas, and the pressure was maintained at approximately 0.2 MPa. The post-processing reactor was evacuated, and after evacuation, the pressure was reduced to -0.05 MPa. The vacuum valve was closed, and the mixture was stirred for 5 minutes. Then, the vacuum valve was opened again, and the pressure was reduced to above -0.09 MPa and maintained for 10 minutes. The temperature was lowered to 70–90℃, the vacuum valve was closed, and N2 gas was purged until the reactor pressure was zero. The product was discharged to obtain an unsaturated intermediate with a molecular weight of 300–800.

[0032] (2) Preparation of wetting and dispersing agents

[0033] Add 330-400 parts of the unsaturated intermediate prepared in step 1 and 200 parts of water to the reactor, heat to 40 degrees Celsius, and stir thoroughly for 30 minutes to allow it to dissolve completely. Then add 2-6 parts of oxidant to the reactor and stir thoroughly for 10 minutes.

[0034] Prepare a solution by using 13-20 parts of acidic monomers, 5-8 parts of sulfonic acid monomers and 40 parts of water as component A, and 2-3 parts of chain transfer agent, 0.6-1.2 parts of reducing agent A and 100 parts of water as component B.

[0035] Add component A and component B dropwise to the reactor simultaneously. Component A is added over 2 hours, and component B is added over 2.5 hours. After components A and B have been added evenly, continue aging for 1 hour. Add 10-15 parts of neutralizing agent to adjust the pH value to approximately 7. Add water to a final volume of 1000 parts, and discharge to obtain a wetting and dispersing agent with a molecular weight of 1000-1200.

[0036] (3) Preparation of wetting and dispersible chromium removal agent

[0037] Add 5-10 parts of wetting and dispersing agent, 30-50 parts of reducing agent B, 20-30 parts of reducing agent C, 1-3 parts of emulsifier, 2-5 parts of antioxidant, and water to a reaction vessel to make up to 100 parts. Heat to 30 degrees and stir thoroughly to obtain a wetting and dispersing chromium removal agent.

[0038] Compared with the prior art, the advantages of the present invention are as follows:

[0039] (1) This invention uses ferrous sulfate as the main base material for reducing hexavalent chromium, combined with other auxiliary reducing agents, to achieve the effect of chromium removal. To prevent the ferrous sulfate and other reducing agents in the system from being oxidized, an antioxidant is added. To prevent the chromium removal solution from precipitating, an emulsifier is added.

[0040] (2) This invention utilizes the principles of polymer chemical structure design and employs the theory of redox free radical polymerization to rationally control its chemical spatial structure, thereby synthesizing a wetting and dispersing agent. This agent is then uniformly compounded with other components in the chromium removal agent to prepare a wetting and dispersing cement chromium removal agent. This chromium removal agent can uniformly coat and penetrate the cement particles, achieving efficient chromium removal.

[0041] (3) The manufacturing process of this invention is simple, highly controllable, and the reaction parameters are clear, enabling the production of a stable wetting and dispersing chromium removal agent. The resulting product is green, environmentally friendly, and cost-effective. Detailed Implementation

[0042] The following are specific embodiments of the present invention, along with figures and tables, to further describe the technical solution of the present invention. However, the present invention is not limited to these embodiments. In the present invention, "parts" refers to "parts by mass".

[0043] A two-step method was used to prepare a wetting and dispersing cement chromium removal agent.

[0044] The formulation of the wetting and dispersing agent is as follows: the total mass of raw materials is 1000 parts, of which the materials used to synthesize oligomers include 300-340 parts of epoxide, 30-60 parts of alcohol monomers, 0.1-0.3 parts of catalyst, 13-20 parts of acid monomers, 5-8 parts of sulfonic acid monomers, 2-6 parts of oxidant, 0.6-1.2 parts of reducing agent A, 2-3 parts of chain transfer agent, 10-15 parts of neutralizing agent, and the remainder is water.

[0045] The formulation of the wetting and dispersing cement chromium removal agent of the present invention is as follows: based on a total mass of 100 parts of raw materials, 5-10 parts of the above-mentioned wetting and dispersing agent, 30-50 parts of reducing agent B, 20-30 parts of reducing agent C, 1-3 parts of emulsifier, 2-5 parts of antioxidant, and the remainder is water.

[0046] The epoxide is ethylene oxide. The alcohol monomer is one or more of methyl allyl alcohol, allyl alcohol, and isopentenyl alcohol. The catalyst is one or more of sodium metal, sodium cyanide, sodium hydroxide, and potassium hydroxide. The acid monomer is one or more of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid. The sulfonic acid monomer is one or more of sodium methpropylene sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and sodium allyl sulfonate. The oxidizing agent is one or more of hydrogen peroxide, ammonium persulfate, and azobisisobutyronitrile. The reducing agent A is one or more of vitamin C, sodium formaldehyde sulfoxylate, sodium sulfite, sodium metabisulfite, ferrous sulfate, and sodium dithionite. The chain transfer agent is one or more of mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol, mercaptothiol, sodium hypophosphite, and sodium methpropylene sulfonate. The neutralizing agent is sodium hydroxide. The wetting and dispersing agent is the raw material synthesized in the first step. The reducing agent B is ferrous sulfate. The reducing agent C is one or more of sodium bisulfite, sodium metabisulfite, sodium thiosulfate, vitamin C, and sodium formaldehyde sulfoxylate. The emulsifier is one or more of nonylphenol polyoxyethylene ether or fatty alcohol polyoxypropylene ether. The antioxidant is vitamin C.

[0047] The preparation method of a wetting and dispersing cement chromium removal agent includes the following steps:

[0048] (1) Preparation of unsaturated intermediates

[0049] At room temperature, add 30–60 parts of alcohol monomers and 0.1–0.3 parts of catalyst to the reactor, start stirring, and evacuate the reactor to -0.07 MPa. After closing the vacuum valve, immediately add 80–100 parts of ethylene oxide to initiate the reaction, maintaining the pressure inside the reactor at 0–0.05 MPa, and simultaneously raise the temperature. When the pressure decreases and the temperature increases, it indicates that the reaction has been initiated, and the feed can be continuously and steadily increased, gradually and slowly raising the reaction pressure. During normal reaction, the reactor temperature (maximum temperature) should be controlled at 105±5℃, and the reactor pressure at 0.2–0.4 MPa.

[0050] The remaining 220–240 parts of ethylene oxide were added gradually, and the reaction was maintained at 110±5℃ for 1–1.5 hours. After maturation, the temperature was lowered to 100±5℃, the reactor was purged with N2 gas, and the pressure was maintained at approximately 0.2 MPa. The post-processing reactor was evacuated, and after evacuation, the pressure was reduced to -0.05 MPa. The vacuum valve was closed, and the mixture was stirred for 5 minutes. Then, the vacuum valve was opened again, and the pressure was reduced to above -0.09 MPa and maintained for 10 minutes. The temperature was lowered to 70–90℃, the vacuum valve was closed, and N2 gas was purged until the reactor pressure was zero. The product was discharged, yielding an unsaturated intermediate with a molecular weight of 300–800.

[0051] (2) Preparation of wetting and dispersing agents

[0052] Add 330-400 parts of the unsaturated intermediate prepared in step 1 and 200 parts of water to the reactor, heat to 40°C, and stir thoroughly for 30 minutes to allow it to dissolve completely. Then add 2-6 parts of oxidant to the reactor and stir thoroughly for 10 minutes.

[0053] Prepare a solution by using 13-20 parts of acidic monomers, 5-8 parts of sulfonic acid monomers and 40 parts of water as component A, and 2-3 parts of chain transfer agent, 0.6-1.2 parts of reducing agent A and 100 parts of water as component B.

[0054] Add component A and component B dropwise to the reactor simultaneously. Component A is added over 2 hours, and component B is added over 2.5 hours. After components A and B have been added evenly, continue aging for 1 hour. Add 10-15 parts of neutralizing agent to adjust the pH value to approximately 7. Add water to a final volume of 1000 parts, and discharge to obtain a wetting and dispersing agent with a molecular weight of 1000-1200.

[0055] (3) Preparation of wetting and dispersible chromium removal agent

[0056] Add 5-10 parts of wetting and dispersing agent, 30-50 parts of reducing agent B, 20-30 parts of reducing agent C, 1-3 parts of emulsifier, 2-5 parts of antioxidant, and water to a reaction vessel to make up to 100 parts. Heat to 30°C and stir thoroughly to obtain a wetting and dispersing chromium removal agent.

[0057] Example 1

[0058] This embodiment uses a two-step method to prepare a wetting and dispersing cement chromium removal agent.

[0059] The first step is to synthesize a low molecular weight oligomer as a wetting and dispersing agent. The total mass of the raw materials is 1000 parts, of which the materials used to synthesize the oligomer include 300 parts of ethylene oxide, 30 parts of allyl alcohol, 0.1 parts of sodium metal, 13 parts of acrylic acid, 5 parts of sodium methacrylate sulfonate, 2 parts of ammonium persulfate, 0.6 parts of vitamin C, 2 parts of mercaptopropionic acid, 10 parts of sodium hydroxide, and the remainder is water.

[0060] The second step involves taking 100 parts of raw materials, including 5 parts of the synthesized wetting and dispersing agent, 40 parts of ferrous sulfate, 20 parts of sodium bisulfite, 1 part of nonylphenol polyoxyethylene ether, 2 parts of vitamin C, and the remainder being water. The mixture is heated to 30°C and stirred thoroughly to obtain a wetting and dispersing chromium removal agent.

[0061] This invention relates to the preparation of a wetting and dispersing cement chromium removal agent, comprising the following steps:

[0062] (1) Preparation of unsaturated intermediates

[0063] At room temperature, add 30 parts allyl alcohol and 0.1 parts metallic sodium to the reactor, start stirring, and evacuate the reactor to -0.07 MPa. After closing the vacuum valve, immediately add 80 parts ethylene oxide to initiate the reaction, maintaining the pressure inside the reactor at 0–0.05 MPa, and simultaneously raise the temperature. When the pressure decreases and the temperature increases, it indicates that the reaction has started, and the feed can be continuously and steadily increased, gradually and slowly increasing the reaction pressure. During normal reaction, the reactor temperature (maximum temperature) should be controlled at 105±5℃, and the reactor pressure at 0.2–0.4 MPa.

[0064] The remaining 220 parts of ethylene oxide were added gradually, and the reaction was maintained at 110±5℃ for 1–1.5 hours. After maturation, the temperature was lowered to 100±5℃, the reactor was purged with N2 gas, and the pressure was maintained at approximately 0.2 MPa. The post-processing reactor was evacuated, and after evacuation, the pressure was reduced to -0.05 MPa. The vacuum valve was closed, and the mixture was stirred for 5 minutes. Then, the vacuum valve was opened again, and the pressure was reduced to above -0.09 MPa and maintained for 10 minutes. The temperature was lowered to 70–90℃, the vacuum valve was closed, and N2 gas was purged until the reactor pressure was zero. The product was discharged, yielding an unsaturated intermediate with a molecular weight of 300–800.

[0065] (2) Preparation of wetting and dispersing agents

[0066] Add 330 parts of the unsaturated intermediate prepared in step 1 and 200 parts of water to the reactor, heat to 40°C, and stir thoroughly for 30 minutes to allow it to dissolve completely. Then add 2 parts of ammonium persulfate to the reactor and stir thoroughly for 10 minutes.

[0067] Prepare a solution using 13 parts acrylic acid, 5 parts sodium methacrylate sulfonate and 40 parts water as ingredient A, and 2 parts mercaptopropionic acid, 0.6 parts vitamin C and 100 parts water as ingredient B.

[0068] Add component A and component B dropwise to the reactor simultaneously. Component A is added over 2 hours, and component B over 2.5 hours. After components A and B have been added evenly, continue aging for 1 hour. Add 10 parts of sodium hydroxide to adjust the pH value to approximately 7. Add water to a final volume of 1000 parts, yielding a wetting and dispersing agent with a molecular weight of 1000–1200.

[0069] (3) Preparation of wetting and dispersible chromium removal agent

[0070] Add 5 parts of wetting and dispersing agent obtained in step 2, 30 parts of ferrous sulfate, 20 parts of sodium bisulfite, 1 part of nonylphenol polyoxyethylene ether, 2 parts of vitamin C, and water to a reaction vessel to make up to 100 parts. Heat to 30°C and stir thoroughly to obtain a wetting and dispersing chromium removal agent.

[0071] Example 2

[0072] This embodiment employs a two-step method to prepare a wetting and dispersing cement chromium removal agent. First, a low molecular weight oligomer is synthesized as a wetting and dispersing agent. The total mass of the raw materials is 1000 parts, comprising 320 parts ethylene oxide, 40 parts allyl alcohol, 0.2 parts metallic sodium, 18 parts acrylic acid, 7 parts sodium methacrylate sulfonate, 3 parts ammonium persulfate, 0.8 parts sodium formaldehyde sulfoxylate, 2.5 parts mercaptopropionic acid, 10 parts sodium hydroxide, and the remainder being water. Second, based on a total mass of 100 parts, 6 parts of the synthesized wetting and dispersing agent, 50 parts ferrous sulfate, 30 parts sodium bisulfite, 1.5 parts nonylphenol polyoxyethylene ether, 3 parts vitamin C, and the remainder being water are heated to 30°C and thoroughly stirred to obtain the wetting and dispersing chromium removal agent.

[0073] This embodiment prepares a wetting and dispersible cement chromium removal agent, including the following steps:

[0074] (1) Preparation of unsaturated intermediates

[0075] At room temperature, add 30 parts allyl alcohol and 0.1 parts metallic sodium to the reactor, start stirring, and evacuate the reactor to -0.07 MPa. After closing the vacuum valve, immediately add 100 parts ethylene oxide to initiate the reaction, maintaining the pressure inside the reactor at 0–0.05 MPa, and simultaneously raise the temperature. When the pressure decreases and the temperature increases, it indicates that the reaction has been initiated, and the feed can be continuously and steadily increased, gradually and slowly raising the reaction pressure. During normal reaction, the reactor temperature (maximum temperature) should be controlled at 105±5℃, and the reactor pressure at 0.2–0.4 MPa.

[0076] The remaining 220 parts of ethylene oxide were added gradually, and the reaction was maintained at 110±5℃ for 1–1.5 hours. After maturation, the temperature was lowered to 100±5℃, the reactor was purged with N2 gas, and the pressure was maintained at approximately 0.2 MPa. The post-processing reactor was evacuated, and after evacuation, the pressure was reduced to -0.05 MPa. The vacuum valve was closed, and the mixture was stirred for 5 minutes. Then, the vacuum valve was opened again, and the pressure was reduced to above -0.09 MPa and maintained for 10 minutes. The temperature was lowered to 70–90℃, the vacuum valve was closed, and N2 gas was purged until the reactor pressure was zero. The product was discharged, yielding an unsaturated intermediate with a molecular weight of 300–800.

[0077] (2) Preparation of wetting and dispersing agents

[0078] Add 360 parts of the unsaturated intermediate prepared in step 1 and 200 parts of water to the reactor, heat to 40°C, and stir thoroughly for 30 minutes to allow it to dissolve completely. Then add 2 parts of ammonium persulfate to the reactor and stir thoroughly for 10 minutes.

[0079] Prepare a solution using 18 parts acrylic acid, 7-methylpropenesulfonate sodium and 40 parts water as component A, and 2.5 parts mercaptopropionic acid, 0.8 parts sodium formaldehyde sulfoxylate and 100 parts water as component B.

[0080] Add component A and component B dropwise to the reactor simultaneously. Component A is added over 2 hours, and component B over 2.5 hours. After components A and B have been added evenly, continue aging for 1 hour. Add 10 parts of sodium hydroxide to adjust the pH value to approximately 7. Add water to a final volume of 1000 parts, yielding a wetting and dispersing agent with a molecular weight of 1000–1200.

[0081] (3) Preparation of wetting and dispersible chromium removal agent

[0082] Add 6 parts of wetting and dispersing agent, 40 parts of ferrous sulfate, 20 parts of sodium bisulfite, 1.5 parts of nonylphenol polyoxyethylene ether, 3 parts of vitamin C, and water to a reactor, and heat to 30°C. Stir thoroughly to obtain a wetting and dispersing chromium removal agent.

[0083] Example 3

[0084] This embodiment employs a two-step method to prepare a wetting and dispersing cement chromium removal agent. First, a low molecular weight oligomer is synthesized as a wetting and dispersing agent. The total mass of the raw materials is 1000 parts, comprising 340 parts ethylene oxide, 40 parts methyl allyl alcohol, 0.3 parts sodium metal, 20 parts acrylic acid, 8 parts methacrylic acid, 4 parts ammonium persulfate, 0.9 parts vitamin C, 2.5 parts mercaptopropionic acid, 10 parts sodium hydroxide, and the remainder being water. Second, based on a total mass of 100 parts of the raw materials, 10 parts of the synthesized wetting and dispersing agent, 50 parts ferrous sulfate, 10 parts sodium bisulfite, 1.5 parts nonylphenol polyoxyethylene ether, 4 parts vitamin C, and the remainder being water are heated to 30°C and thoroughly stirred to obtain the wetting and dispersing chromium removal agent.

[0085] This embodiment prepares a wetting and dispersible cement chromium removal agent, including the following steps:

[0086] (1) Preparation of unsaturated intermediates

[0087] At room temperature, add 40 parts of methyl allyl alcohol and 0.3 parts of metallic sodium to the reactor, start stirring, and evacuate the reactor to -0.07 MPa. After closing the vacuum valve, immediately add 100 parts of ethylene oxide to initiate the reaction, maintaining the pressure inside the reactor at 0–0.05 MPa, and simultaneously raise the temperature. When the pressure decreases and the temperature increases, it indicates that the reaction has been initiated, and the feed can be continuously and steadily increased, gradually and slowly raising the reaction pressure. During normal reaction, the reactor temperature (maximum temperature) should be controlled at 105±5℃, and the reactor pressure at 0.2–0.4 MPa.

[0088] The remaining 240 parts of ethylene oxide were added gradually, and the reaction was maintained at 110±5℃ for 1–1.5 hours. After maturation, the temperature was lowered to 100±5℃, the reactor was purged with N2 gas, and the pressure was maintained at approximately 0.2 MPa. The post-processing reactor was evacuated, and after evacuation, the pressure was reduced to -0.05 MPa. The vacuum valve was closed, and the mixture was stirred for 5 minutes. Then, the vacuum valve was opened again, and the pressure was reduced to above -0.09 MPa and maintained for 10 minutes. The temperature was lowered to 70–90℃, the vacuum valve was closed, and N2 gas was purged until the reactor pressure was zero. The product was discharged, yielding an unsaturated intermediate with a molecular weight of 300–800.

[0089] (2) Preparation of wetting and dispersing agents

[0090] Add 380 parts of the unsaturated intermediate prepared in step 1 and 200 parts of water to the reactor, heat to 40°C, and stir thoroughly for 30 minutes to allow it to dissolve completely. Then add 4 parts of ammonium persulfate to the reactor and stir thoroughly for 10 minutes.

[0091] Prepare a solution using 20 parts acrylic acid, 8 parts sodium methyl propylene sulfonate, and 40 parts water as ingredient A, and 2.5 parts mercaptopropionic acid, 0.9 parts vitamin C, and 100 parts water as ingredient B.

[0092] Add component A and component B dropwise to the reactor simultaneously. Component A is added over 2 hours, and component B over 2.5 hours. After components A and B have been added evenly, continue aging for 1 hour. Add 10 parts of sodium hydroxide to adjust the pH value to approximately 7. Add water to a final volume of 1000 parts, yielding a wetting and dispersing agent with a molecular weight of 1000–1200.

[0093] (3) Preparation of wetting and dispersible chromium removal agent

[0094] Add 10 parts of wetting and dispersing agent, 50 parts of ferrous sulfate, 10 parts of sodium bisulfite, 1.5 parts of nonylphenol polyoxyethylene ether, 4 parts of vitamin C, and water to a reactor, and heat to 30°C. Stir thoroughly to obtain a wetting and dispersing chromium removal agent.

[0095] Example 4

[0096] This embodiment uses a two-step method to prepare a wetting and dispersing cement chromium removal agent.

[0097] The first step is to synthesize a low molecular weight oligomer as a wetting and dispersing agent. The total mass of the raw materials is 1000 parts, of which the materials used to synthesize the oligomer include 330 parts of ethylene oxide, 40 parts of isopentenyl alcohol, 0.2 parts of sodium metal, 19 parts of methacrylic acid, 7 parts of 2-acrylamido-2-methylpropanesulfonic acid, 3 parts of ammonium persulfate, 1.2 parts of vitamin C, 3 parts of mercaptopropionic acid, 10 parts of potassium hydroxide, and the remainder is water.

[0098] The second step involves taking 10 parts of the synthesized wetting and dispersing agent, 45 parts of ferrous sulfate, 20 parts of sodium bisulfite, 2 parts of fatty alcohol polyoxypropylene ether, 5 parts of vitamin C, and the remainder of water as a total of 100 parts. The mixture is heated to 30°C and stirred thoroughly to obtain a wetting and dispersing chromium removal agent.

[0099] This embodiment prepares a wetting and dispersible cement chromium removal agent, including the following steps:

[0100] (1) Preparation of unsaturated intermediates

[0101] At room temperature, add 40 parts isopentenol and 0.2 parts metallic sodium to the reactor, start stirring, and evacuate the reactor to -0.07 MPa. After closing the vacuum valve, immediately add 100 parts ethylene oxide to initiate the reaction, maintaining the pressure inside the reactor at 0–0.05 MPa, and simultaneously raise the temperature. When the pressure decreases and the temperature increases, it indicates that the reaction has started, and the feed can be continuously and steadily increased, gradually increasing the reaction pressure. During normal reaction, the reactor temperature (maximum temperature) should be controlled at 105±5℃, and the reactor pressure at 0.2–0.4 MPa.

[0102] The remaining 230 parts of ethylene oxide were added gradually, and the reaction was maintained at 110±5℃ for 1–1.5 hours. After maturation, the temperature was lowered to 100±5℃, the reactor was purged with N2 gas, and the pressure was maintained at approximately 0.2 MPa. The post-processing reactor was evacuated, and after evacuation, the pressure was reduced to -0.05 MPa. The vacuum valve was closed, and the mixture was stirred for 5 minutes. Then, the vacuum valve was opened again, and the pressure was reduced to above -0.09 MPa and maintained for 10 minutes. The temperature was lowered to 70–90℃, the vacuum valve was closed, and N2 gas was purged until the reactor pressure was zero. The product was discharged, yielding an unsaturated intermediate with a molecular weight of 300–800.

[0103] (2) Preparation of wetting and dispersing agents

[0104] Add 370 parts of the unsaturated intermediate prepared in step 1 and 200 parts of water to the reactor, heat to 40°C, and stir thoroughly for 30 minutes to allow it to dissolve completely. Then add 3 parts of ammonium persulfate to the reactor and stir thoroughly for 10 minutes.

[0105] Prepare a solution using 19 parts methacrylic acid, 7 parts 2-acrylamido-2-methylpropanesulfonic acid and 40 parts water as ingredient A, and 3 parts mercaptopropionic acid, 1.2 parts vitamin C and 100 parts water as ingredient B.

[0106] Add component A and component B dropwise to the reactor simultaneously. Component A is added over 2 hours, and component B is added over 2.5 hours. After components A and B have been added evenly, continue aging for 1 hour. Add 10 parts of potassium hydroxide to adjust the pH value to approximately 7. Add water to a final volume of 1000 parts, and discharge to obtain a wetting and dispersing agent with a molecular weight of 1000–1200.

[0107] (3) Preparation of wetting and dispersible chromium removal agent

[0108] Add 10 parts of wetting and dispersing agent, 45 parts of ferrous sulfate, 20 parts of sodium bisulfite, 2 parts of fatty alcohol polyoxypropylene ether, 5 parts of vitamin C, and water to a reaction vessel to make up to 100 parts. Heat to 30°C and stir thoroughly to obtain a wetting and dispersing chromium removal agent.

[0109] Comparative Example 1

[0110] The formulation and preparation method of the comparative chromium removal agent are as follows:

[0111] Add 30 parts ferrous sulfate, 20 parts sodium bisulfite, 1 part nonylphenol polyoxyethylene ether, 2 parts vitamin C, and water to a reaction vessel to a final volume of 100 parts. Heat to 30°C and stir thoroughly to obtain a wetting and dispersing chromium removal agent. The difference from Example 1 is that no synthetic wetting and dispersing agent was added.

[0112] Comparative Example 2

[0113] This comparative example uses ferrous sulfate heptahydrate chromium removal agent manufactured by Wuhan Jingneng Technology Co., Ltd. as a comparison. The chromium removal agent model is GN-1008.

[0114] Furthermore, experiments were conducted to compare the chromium removal agents and their effects on the physical properties of cement with the finished products of Examples 1 to 4 and Comparative Examples 1 and 2.

[0115] Table 1 Grinding ratio:

[0116] Cement clinker Volcanic rock Limestone Gypsum Grinding time 76.5％ 12.5％ 7.0％ 4.0％ 28 min

[0117] Table 2 Comparison of chromium removal effects (GB31893-2015) of each embodiment and comparative example, and their impact on cement physical properties.

[0118] (The four strength test items in the table refer to the standard GB / T7671-2021)

[0119]

[0120]

[0121] Table 2 shows that the hexavalent chromium content in the blank sample was 14.9 ppm. After incorporating Examples 1 to 4, and Comparative Examples 1 and 2, the hexavalent chromium content decreased. Among them, Examples 1 to 4 showed a much larger reduction than Comparative Examples 1 and 2, indicating that the wetting and dispersing cement chromium remover prepared according to the present invention has a superior chromium removal effect.

[0122] Compared to Example 1, Comparative Example 1 did not add a wetting and dispersing agent, but all other ingredients were the same. However, its chromium removal effect was lower than that of Example 1. This is mainly because, without the action of a wetting and dispersing agent, the reducing component cannot fully penetrate into the interior of the cement particles, and the dispersion ability is also insufficient, making it impossible to avoid local cement particle agglomeration. Therefore, its chromium removal ability is slightly insufficient.

[0123] Compared with Examples 1 to 4, Comparative Example 2, which is a single ferrous sulfate heptahydrate, has a low reduction effect, only reducing it to 7.8 ppm. Compared with the composite reducing agent, it has no reduction superposition effect.

[0124] As shown in Table 2, the hexavalent chromium content in Comparative Example 2 gradually increased over time. Unlike Examples 1 to 4 and Comparative Example 1, no antioxidant was added. In Comparative Example 2, after the hexavalent chromium was reduced to trivalent chromium, both ferrous sulfate heptahydrate and trivalent chromium were oxidized due to the lack of added antioxidant. Therefore, as the reducing agent became ineffective and hexavalent chromium was generated, the hexavalent chromium content gradually increased in the later stages, even exceeding the 10 ppm limit set by the national standard (GB31893-2015).

[0125] Furthermore, the wetting and dispersing cement chromium remover prepared by this invention has no adverse effects on cement setting time or compressive and flexural strength at various ages, and can be widely used in various types of cement.

[0126] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A wetting and dispersing cement chromium removal agent, characterized in that... The raw material components include: total mass based on 100 parts, 5-10 parts of wetting and dispersing agent Reducing agent B 30-50 parts Reducing agent C 20-30 parts 1-3 parts emulsifier Antioxidant 2-5 parts, The remainder is water; Wherein: the reducing agent B is ferrous sulfate; The reducing agent C is one or a mixture of sodium bisulfite, sodium metabisulfite, sodium thiosulfate, vitamin C, and sodium formaldehyde sulfoxylate. The emulsifier is one or a mixture of nonylphenol polyoxyethylene ether and fatty alcohol polyoxypropylene ether; The antioxidant is vitamin C; The wetting and dispersing agent is a finished product, and it is a low molecular weight oligomer with a molecular weight of 1000-1200; its raw material components include: a total mass of 1000 parts, Epoxide 300-340 parts 30-60 parts of alcohol monomers Catalyst 0.1-0.3 parts, 13-20 parts of acidic small monomers 5-8 parts of sulfonic acid monomers 2-6 parts of oxidant Reducing agent A: 0.6–1.2 parts 2-3 parts of chain transfer agent 10-15 parts of neutralizing agent The remainder is water; Wherein: the epoxide is ethylene oxide; The alcohol monomer is one or a mixture of methyl allyl alcohol, allyl alcohol, and isopentenol; The catalyst is one or a mixture of sodium metal, sodium cyanide, sodium hydroxide, and potassium hydroxide; The acid monomers are one or more of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid; The sulfonic acid monomer is sodium methpropylene sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, or sodium allyl sulfonate, or a mixture thereof. The oxidant is one or a mixture of hydrogen peroxide, ammonium persulfate, and azobisisobutyronitrile; The reducing agent A is one or a mixture of more of the following: vitamin C, sodium formaldehyde sulfoxylate, sodium sulfite, sodium metabisulfite, ferrous sulfate, and sodium dithionite; The chain transfer agent is one or a mixture of mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol, mercaptothiol, sodium hypophosphite, and sodium methacrylate sulfonate. The neutralizing agent is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, and potassium hydroxide.

2. The wetting and dispersing cement chromium removal agent according to claim 1, characterized in that... The preparation method of the wetting and dispersing cement chromium removal agent includes the following steps: adding 5-10 parts of wetting and dispersing agent, 30-50 parts of reducing agent B, 20-30 parts of reducing agent C, 1-3 parts of emulsifier, 2-5 parts of antioxidant, and water to 100 parts into a reaction vessel, heating to 30°C, and stirring thoroughly to obtain the wetting and dispersing chromium removal agent.

3. A wetting and dispersing agent, characterized in that... The raw material components include: total mass based on 1000 parts, Epoxide 300-340 parts 30-60 parts of alcohol monomers Catalyst 0.1-0.3 parts, 13-20 parts of acidic small monomers 5-8 parts of sulfonic acid monomers 2-6 parts of oxidant Reducing agent A: 0.6–1.2 parts 2-3 parts of chain transfer agent 10-15 parts of neutralizing agent The remainder is water; Wherein: the epoxide is ethylene oxide; The alcohol monomer is one or a mixture of methyl allyl alcohol, allyl alcohol, and isopentenol; The catalyst is one or a mixture of sodium metal, sodium cyanide, sodium hydroxide, and potassium hydroxide; The acid monomers are one or more of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid; The sulfonic acid monomer is sodium methpropylene sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, or sodium allyl sulfonate, or a mixture thereof. The oxidant is one or a mixture of hydrogen peroxide, ammonium persulfate, and azobisisobutyronitrile; The reducing agent A is one or a mixture of more of the following: vitamin C, sodium formaldehyde sulfoxylate, sodium sulfite, sodium metabisulfite, ferrous sulfate, and sodium dithionite; The chain transfer agent is one or a mixture of mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol, mercaptothiol, sodium hypophosphite, and sodium methacrylate sulfonate. The neutralizing agent is sodium hydroxide; The wetting and dispersing agent is a low molecular weight oligomer with a molecular weight of 1000~1200.

4. A method for preparing a wetting and dispersing agent, characterized by the following steps: include: 1) Preparation of unsaturated intermediates 1.1) At room temperature, add 30-60 parts of alcohol monomers and 0.1-0.3 parts of catalyst to the reactor, start stirring, and immediately add 80-100 parts of ethylene oxide to initiate the reaction after the reactor is evacuated to -0.07 MPa. Keep the pressure inside the reactor at 0-0.05 MPa and immediately raise the temperature. 1.2) When the pressure decreases and the temperature increases, it indicates that the reaction has been initiated. Continue to feed the material steadily and gradually increase the reaction pressure. Control the reactor temperature at 105±5℃ and the reactor pressure at 0.2~0.4Mpa. Gradually add the remaining 120~240 parts of ethylene oxide. 1.5) Maintain the reactor temperature at 110±5℃ and allow the reaction to mature for 1 to 1.5 hours; 1.4) After the ripening reaction is completed, the temperature of the reactor is lowered to 100±5℃; during the cooling process, the reactor is purged with N2 gas to maintain a pressure of 0.2±0.02Mpa; 1.5) After evacuating the reactor to -0.05 MPa, stir; then evacuate to no higher than -0.09 MPa and maintain for 10 minutes; then lower the reactor temperature to 70-90°C, stop evacuating, and then purge with N2 gas until the reactor pressure is zero. Discharge the material to obtain an unsaturated intermediate with a molecular weight of 300-800. 2) Preparation of wetting and dispersing agents 2.1) Add 330-400 parts of unsaturated intermediate and 200 parts of water to the reactor, heat to 40°C, and stir to allow the unsaturated intermediate to dissolve completely; 2.2) Add 2-6 parts of oxidant to the reactor and stir thoroughly; 2.3) Add material A and material B dropwise to the reactor simultaneously; material A is added over 2 hours, and material B is added over 2.5 hours. Component A is a solution prepared by mixing 13-20 parts of acidic small monomers, 5-8 parts of sulfonic acid small monomers and 40 parts of water; Component B is a solution prepared by mixing 2-3 parts of chain transfer agent, 0.6-1.2 parts of reducing agent A and 100 parts of water. 2.4) After materials A and B have been evenly added, continue aging for 1 hour; 2.5) Add 10-15 parts of neutralizing agent to adjust the pH value to 6-7; add water to 1000 parts and discharge to obtain a wetting and dispersing agent with a molecular weight of 1000-1200; The unit "parts" refers to the number of parts by weight.

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