Method for producing a magnesium oxide-containing composition and method for utilizing calcium and magnesium ion-containing wastewater

Abstract

A method for producing a magnesium oxide composition and a method for utilizing calcium and magnesium ion-containing wastewater, the method for producing a magnesium oxide composition, comprising modifying a magnesium oxide with a solution containing magnesium ions and / or calcium ions, and mixing and beating a dispersion of the modified magnesium oxide with a precursor of another component. The solution containing magnesium ions and / or calcium ions is preferably calcium and magnesium ion-containing wastewater. The method can reduce the generation of a hardened mass.

Description

Technical Field

[0001] This invention relates to a method for preparing magnesium-containing compositions using active magnesium oxide and to the industrial preparation of decationized water containing Ca. 2+ Mg 2+ Methods for utilizing wastewater containing impurity ions. Technical Background

[0002] In some magnesium and aluminum-containing material preparation processes, such as the production of catalytic cracking sulfur transfer aids and metal scavengers using magnesium oxide as an SO2 adsorbent carrier, the mixing and spray drying of active magnesium oxide and alumina-containing slurries can lead to "caking" when the temperature after mixing and pulping exceeds 40°C. This results in a large amount of waste residue, sometimes exceeding 10% of the total dry basis, especially during high-temperature production where the temperature after mixing typically reaches over 60°C. Currently, large pieces of waste residue are filtered out using vibrating screens, but even smaller particles can clog the precision filter before spray drying, requiring frequent cleaning of the precision filter during production, severely impacting production stability and reducing product wear performance. While adding heat exchangers can lower the mixture temperature to some extent, it significantly increases production costs, and due to the large volume of the reaction vessel and the resulting temperature gradient, significant "caking" still occurs.

[0003] In the production of catalytic cracking catalysts, industrial water is prepared into decationized water through hydrochloric acid ion exchange, which also generates a large amount of water containing Ca. 2+ Mg 2+ Ionized wastewater. Direct discharge of this wastewater will cause excessive salt discharge. When it enters the water treatment plant and mixes with alkaline wastewater, it will form precipitates and eventually form catalyst residue. The residue contains calcium and magnesium, which will also affect the subsequent utilization of the residue. Summary of the Invention

[0004] One of the technical problems to be solved by this invention is to provide a method for preparing a composition using activated magnesium oxide and alumina and / or alumina precursor slurry, which can reduce the formation of caking. Another technical problem to be solved by this invention is to provide a method for producing a water treatment product containing Ca... 2+ Mg 2+ Methods for utilizing wastewater containing impurity ions.

[0005] The present invention provides a method for preparing a composition containing alumina and magnesium oxide, comprising modifying magnesium oxide, preferably active magnesium oxide, with a solution containing magnesium ions and / or calcium ions to obtain modified magnesium oxide, and mixing the modified magnesium oxide with a dispersion containing alumina and slurrying.

[0006] According to the above technical solution, in one embodiment, the alumina-containing dispersion is a slurry formed by a substance capable of forming γ-alumina after calcination and water. The alumina-containing dispersion is, for example, a slurry containing boehmite and / or aluminum sol.

[0007] According to any of the above technical solutions, the solid content of the alumina-containing dispersion is preferably 5-20% by weight.

[0008] According to any of the above technical solutions, the alumina-containing dispersion is acidified, and the acid-aluminum ratio (molar ratio of acid to aluminum) is 0.2 to 0.7. The acid is, for example, one or more of hydrochloric acid, nitric acid, sulfuric acid, and organic acids.

[0009] According to any of the above technical solutions, in one embodiment, the pH value of the alumina-containing dispersion is preferably 1 to 3.

[0010] According to any of the above technical solutions, preferably, the pH value of the solution containing magnesium ions and / or calcium ions is 0.5 to 2, wherein Ca 2+ Ion concentration of 0–5% by weight, Mg 2+ The ion concentration is 0–5% by weight, and Ca 2+ and Mg 2+ The total concentration is not less than 0.2% by weight, for example, 0.2-5% by weight or 0.4-2% by weight.

[0011] According to any of the above technical solutions, in one manner, the solution containing magnesium ions and / or calcium ions is acidic wastewater containing calcium and magnesium ions, wherein Ca... 2+ The ion concentration is 0.1–5 wt%, for example 0.2–5 wt% or 0.2–1 wt%, Mg 2+ The ion concentration is 0.1–5% by weight, for example 0.5–5% by weight or 0.2–1% by weight, and the pH value is 0.5–2.0. The acidic wastewater containing calcium and magnesium ions may also contain one or more other impurity ions, the content of which preferably does not exceed 1% by weight, such as one or more of Fe, Cu, Co, and Zr.

[0012] In one embodiment, the total content of calcium ions, magnesium ions, and other ions in the acidic wastewater containing calcium and magnesium ions can be 0.4-5% by weight, for example, 0.5-2% by weight.

[0013] According to any of the above technical solutions, the magnesium oxide is preferably active magnesium oxide, and the active magnesium oxide has a citric acid value of 100-500s measured at 30°C. -1 .

[0014] In one embodiment, the magnesium oxide, preferably active magnesium oxide, has a particle size distribution (D(V, 0.5)) of no more than 10 micrometers, for example, 2 to 5 micrometers, and the particle size can be measured using laser particle size distribution method.

[0015] According to any of the above technical solutions, the magnesium oxide, preferably active magnesium oxide, is modified with a solution containing magnesium ions and / or calcium ions, comprising mixing the magnesium oxide, preferably active magnesium oxide slurry, with the solution containing magnesium ions and / or calcium ions. Preferably, the mixture is stirred for at least 5 minutes, for example, 10 to 120 minutes. The solid content of the magnesium oxide, preferably active magnesium oxide slurry, is 20 to 45% by weight.

[0016] According to any of the above technical solutions, the amount of the solution containing magnesium ions and / or calcium ions is such that the pH value of the mixture obtained by mixing the solution containing magnesium ions and / or calcium ions with the magnesium oxide slurry is 8 to 11.

[0017] The method according to any of the above technical solutions is characterized in that the modification of magnesium oxide, preferably active magnesium oxide, with a solution containing magnesium ions and / or calcium ions is carried out at 5-60°C, for example, room temperature to 50°C, wherein the room temperature is, for example, 15-35°C.

[0018] According to any of the above technical solutions, magnesium oxide, preferably active magnesium oxide, is surface modified. The modification process is as follows: first, magnesium oxide is slurried in deionized water to prepare a slurry with a solid content of 20-45%. Then, it is added to acidic wastewater under stirring conditions, and the pH value is controlled to be 8-11. After being added to the acidic wastewater, it is stirred at room temperature to 50°C for 10-120 minutes.

[0019] In one embodiment, the modified magnesium oxide is mixed with an alumina-containing dispersion and pulped at room temperature to 60°C. For example, the temperature of the slurry formed by mixing the modified magnesium oxide and the alumina-containing dispersion is between 40°C and 55°C. Preferably, the modified magnesium oxide slurry is mixed with the alumina-containing dispersion.

[0020] This invention provides a method for utilizing wastewater containing calcium and magnesium ions. The method includes: mixing acidic wastewater containing calcium and magnesium ions with a pH of 0.5 to 2 with activated magnesium oxide slurry according to any of the above technical solutions; controlling the temperature of the mixture to be room temperature to 50°C; adjusting the pH of the activated magnesium oxide slurry to 8 to 11 to perform surface metal modification on the activated magnesium oxide; and then using the modified activated magnesium oxide slurry to prepare sulfur transfer aids or adsorbents for adsorbing sulfur oxides.

[0021] A method for preparing a magnesium-containing composition using magnesium oxide includes modifying magnesium oxide with a solution containing magnesium ions and / or calcium ions to form a modified magnesium oxide slurry, and then mixing the modified magnesium oxide slurry with a dispersion of other component precursors of the magnesium-containing composition. The dispersion of the other component precursors may be, for example, a dispersion of a silica precursor, a zirconium oxide precursor, or a titanium oxide precursor; the silica precursor dispersion may be, for example, an acidic silica sol; the zirconium oxide precursor dispersion may be, for example, an acidic zirconium sol; and the titanium oxide precursor dispersion may be, for example, an acidic titanium sol. The pH value of the other component precursor dispersion is preferably 1 to 3. The magnesium oxide is preferably active magnesium oxide. This method can reduce the formation of caking during the preparation of the magnesium-containing composition.

[0022] The method for preparing a composition containing alumina and magnesium oxide provided by the present invention can modify the surface of active magnesium oxide, reduce or eliminate the caking phenomenon of the reaction between active magnesium oxide and alumina dispersion, and solve the problem of easy caking and waste residue generation when magnesium oxide slurry is directly mixed with acidified boehmite at higher temperatures, such as 40-60℃.

[0023] The method for preparing the alumina and magnesium oxide composition can be used to prepare magnesium and aluminum-containing catalytic cracking catalysts or catalytic cracking aids. Examples of such catalytic cracking aids include magnesium and aluminum-containing sulfur transfer agents, magnesium and aluminum-containing denitrification aids, and anti-metal contamination aids.

[0024] The method for utilizing calcium and magnesium ion-containing wastewater provided by this invention involves first modifying activated magnesium oxide with the wastewater, and then using it for the preparation of a sulfur transfer agent. This method can reduce or eliminate caking, reduce clogging of the slurry precision filter, and improve the yield. Simultaneously, the introduction of Ca... 2+ Mg 2+ After calcination, impurity ions form alkali metal oxides, which can be used as sulfur adsorption components in sulfur transfer agents and will not adversely affect the sulfur transfer performance of sulfur transfer aids. Detailed Implementation

[0025] The present invention provides a method for utilizing wastewater containing calcium and magnesium ions, wherein the wastewater containing calcium and magnesium ions is used to modify the surface of active magnesium oxide to form a modified magnesium oxide slurry, and then the modified active magnesium oxide slurry is used to prepare a sulfur transfer agent.

[0026] In one embodiment, the acidic wastewater containing calcium and magnesium ions contains Ca... 2+ The ion concentration is 0.1–0.5% by weight, Mg 2+ The ion concentration is 0.1–0.5% by weight, and the pH value of the wastewater is 0.8–2.0. Acidic wastewater containing calcium and magnesium ions may also contain one or more other ions such as Fe, Cu, Co, and Zr, with the content of other ions being 0–1% by weight.

[0027] Currently, the sulfur transfer agent compositions used in industry mainly consist of alkaline earth metal compounds, primarily magnesium oxide, and alumina, or a mixture of rare earth elements and alumina, followed by spray drying, calcination, and rare earth impregnation to obtain the final sulfur transfer aid. Therefore, the application of compounds containing Ca... 2+ Mg 2+ Wastewater containing ions can convert these alkali metal ions into sulfur carriers without affecting the performance of sulfur transfer aids. At the same time, the presence of Fe, Cu, Co, Zr and other ions will also promote the redox reaction of sulfur transfer aids.

[0028] In one embodiment, the sulfur transfer agent comprises: magnesium oxide, aluminum oxide, optionally vanadium oxide, and rare earth oxide.

[0029] In one embodiment, the method for preparing a sulfur transfer agent using modified active magnesium oxide slurry includes: mixing boehmite, optionally a vanadium compound, an acid, water, and the modified active magnesium oxide slurry to form a colloidal slurry, and spray drying; wherein the rare earth compound can be introduced into the colloidal slurry before spray drying, or it can be introduced into the spray-dried particles by impregnation after spray drying.

[0030] In one embodiment, the pseudoboehmite is acid-modified to form a modified pseudoboehmite colloid, and then a modified active magnesium oxide slurry and an optional vanadium compound are mixed. In another embodiment, the modified pseudoboehmite acidic colloid is prepared as follows: pseudoboehmite with a solid content of 5-20% by weight is added to acidic water, and hydrochloric acid is added. The acid-to-aluminum ratio (HCl to Al molar ratio) is 0.2-0.7, preferably, and the pH is adjusted to 1-3.

[0031] The method for preparing the sulfur transfer agent may further include a calcination step, which is well known to those skilled in the art, for example, calcination can be carried out at 600-800°C in an air atmosphere for 2-5 hours.

[0032] The following examples are used to illustrate the present invention, but are not intended to limit the possible implementations of the present invention.

[0033] The method for measuring the citric acid value is as follows: Q / SH 361750.

[0034] Method for measuring the degree of hardening: After gelation, the colloid is passed through a 20-mesh sieve, and the residue on the sieve is weighed and recorded as m. (筛余物) And analyze the solid content w of the residue on the sieve. (筛余物) The total dry weight of the product obtained by gelation is denoted as m. (成胶总干基) ,

[0035] Content of compacted material (or degree of compaction) = m (筛余物) ×w (筛余物) ÷m (成胶总干基)

[0036] The solid content analysis method is as follows: weigh the sample and record it as W1, then calcine it at 850℃ for 1 hour, weigh it again and record it as W2, and the solid content = W2 ÷ W1 × 100%.

[0037] The modified pseudoboehmite acidic colloid is prepared as follows: Pseudoboehmite (Shandong Branch of Aluminum Corporation of China Limited) with a solid content of 15% by weight is added to acidic water (pH value of 3.5), and hydrochloric acid is added with an acid-to-aluminum ratio of 0.4.

[0038] Magnesium oxide, produced by Beijing Chemical Plant.

[0039] The apparent bulk density of the catalytic cracking catalyst additive was determined according to NB / SH / T 0954-2017.

[0040] The pore volume of catalytic cracking catalyst promoters was determined according to NB / SH / T 0955-2017.

[0041] The wear index of catalytic cracking catalyst additives was determined according to NB / SH / T 0964-2017.

[0042] Particle size distribution was determined using laser particle size distribution method, see standard NB / SH / T 0951-2017.

[0043] Example 1

[0044] The citric acid value at 30℃ is 500s. -1 Activated magnesium oxide (D(V, 0.5) = 3.7 μm) was slurried in decationized water, and the solid content was measured to be 45% by weight, with a pH of 12.8. Acidic wastewater containing calcium and magnesium ions was added, the pH was adjusted to 11, and the mixture was stirred at 50°C for 30 minutes to obtain modified magnesium oxide slurry. The calcium and magnesium ions in the acidic wastewater... 2+ The ion concentration is 0.5% by weight, Mg 2+ The ion concentration was 0.5% by weight, the pH value was 1.7, and the volume ratio of the added volume to the magnesium oxide slurry was 0.25:1.

[0045] The modified magnesium oxide slurry was mixed with the prepared modified boehmite acid colloid, wherein the weight ratio of magnesium oxide to boehmite (calculated as Al2O3) was 1:1; the mixture was stirred at 50°C for 60 minutes to obtain magnesium-aluminum colloid, wherein the content of agglomerates in the magnesium-aluminum colloid was 0.3% by weight.

[0046] The carrier was obtained by spray drying and calcination (calcination temperature 600℃, calcination time 3h, the same below);

[0047] The prepared carrier was supersaturated with cerium chloride solution to obtain the sulfur transfer aid product, denoted as RS-1. The cerium content, calculated as CeO2, was 15% by weight, based on the dry weight of the aid.

[0048] Example 2

[0049] Active magnesium oxide (30℃, citric acid value 350s) -1 The particle size distribution (D(V, 0.5) is 2.7 micrometers) was pulped in decationized water, and the pH value was measured to be 12.5, with a solid content of 35% by weight. Acidic wastewater containing calcium and magnesium ions was then added (the acidic wastewater containing calcium and magnesium ions contains Ca...). 2+ The ion concentration is 0.3% by weight, Mg 2+ The ion concentration is 0.4% by weight, Fe 3+ An ion concentration of 0.2 wt% and a pH of 1.3 were added, with a volume ratio of 0.4:1 to the magnesium oxide slurry and a pH of 10.3. The mixture was stirred at 40°C for 90 minutes to obtain a modified magnesium oxide slurry. The modified magnesium oxide slurry was then mixed with a pre-prepared modified boehmite acidic colloid and stirred at 50°C for 30 minutes. The weight ratio of active magnesium oxide to boehmite (calculated as Al2O3) was 1:1 to obtain a magnesium-aluminum colloid with a crust content of 0.2 wt%.

[0050] The carrier is obtained by spray drying and calcination;

[0051] The prepared carrier was supersaturated with cerium chloride aqueous solution and dried to obtain the sulfur transfer aid product. Based on the dry weight of the aid, the cerium content calculated as CeO2 was 15% by weight, denoted as RS-2.

[0052] Example 3

[0053] Activated magnesium oxide (citric acid value 200s at 30℃) -1 The particle size distribution (D(V, 0.5) is 3.2 micrometers) was pulped in decationized water, and the pH was measured to be 12.0 with a solid content of 30% by weight. Acidic wastewater containing calcium and magnesium ions (of which Ca...) was then added. 2+ The ion concentration is 0.2% by weight, Mg 2+ The ion concentration was 0.2% by weight, Fe 3+ The ion concentration is 0.5% by weight, Cu 3+The ion concentration was 0.2 wt%, and the pH value was 1.0. The volume ratio of the added material to the magnesium oxide slurry was 0.6:1, the pH value was adjusted to 9.4, and the mixture was stirred at 30℃ for 120 minutes to obtain a surface-modified active magnesium oxide slurry. The surface-modified active magnesium oxide slurry was mixed with the prepared modified boehmite acidic colloid and stirred at 50℃ for 30 minutes to obtain a magnesium-aluminum colloid, wherein the weight ratio of active magnesium oxide to boehmite (calculated as Al2O3) was 1:1; the content of agglomerates in the magnesium-aluminum colloid was 0.2 wt%.

[0054] The carrier was obtained by spray drying and calcination;

[0055] The prepared carrier was supersaturated with cerium chloride aqueous solution to obtain the sulfur transfer aid product. Based on the dry weight of the aid, the CeO2 content was 17% by weight, which was denoted as RS-3.

[0056] Comparative Example 1

[0057] Activated magnesium oxide (30℃, citric acid value 500s) -1 The mixture was pulped in decationized water, and the pH was measured to be 12.8, the solid content to be 45 wt%, and the temperature to be 50℃. Then it was mixed with the prepared modified boehmite acidic colloid and stirred to obtain magnesium-aluminum colloid, wherein the weight ratio of active magnesium oxide to boehmite (calculated as Al2O3) was 1:1. After stirring at 50℃ for 60 minutes, the content of agglomerates in the magnesium-aluminum colloid was 3.5 wt%.

[0058] The carrier was obtained by spray drying and calcination;

[0059] Following the method of Example 1, the prepared carrier was subjected to supersaturated impregnation to obtain the sulfur transfer aid product, denoted as DB-1.

[0060] Comparative Example 2

[0061] Active magnesium oxide (30℃, citric acid value 350s) -1 The magnesium oxide slurry was slurried in decationized water, and the pH was measured to be 12.5, the solid content to be 35 wt%, and the temperature to be 40°C. This magnesium oxide slurry was then mixed with a pre-prepared modified pseudoboehmite acidic colloid and stirred at 50°C for 30 minutes to obtain a magnesium-aluminum colloid. The content of the sludge in the magnesium-aluminum colloid was 2.1 wt%. After spray drying and calcination, a carrier was obtained. Following the method of Example 2, the prepared carrier was subjected to supersaturated impregnation to obtain the sulfur transfer aid product, denoted as DB-2.

[0062] Comparative Example 3

[0063] Activated magnesium oxide (30℃, citric acid value 200s) -1The magnesium oxide slurry was pulped in deionized water, and the pH was measured to be 12.5, the solid content to be 35 wt%, and the temperature to be 40°C. Deionized water with a volume ratio of 0.6:1 to the magnesium oxide slurry was added and stirred at 30°C for 120 minutes. This magnesium oxide slurry was then mixed with the prepared modified pseudoboehmite acidic colloid and stirred at 50°C for 30 minutes to obtain a magnesium-aluminum colloid. The content of the agglomerated material in the magnesium-aluminum colloid was 1.7% by weight. After spray drying and calcination, a carrier was obtained. Following the method of Example 3, the prepared carrier was supersaturated and impregnated to obtain the sulfur transfer aid product, designated DB-3.

[0064] Table 1 Physicochemical properties of the additives

[0065] RS-1 0.31 1.06 2.1 RS-2 0.29 1.09 2.0 RS-3 0.30 1.11 1.7 DB-1 0.38 0.89 5.1 DB-2 0.39 0.87 6.3 DB-3 0.37 0.88 5.2

[0066] Evaluation of sulfur adsorption performance of sulfur transfer aids (hereinafter referred to as sulfur transfer agents)

[0067] Take 0.5g of the prepared sulfur transfer agent and place it in a quartz tube fixed bed reactor with an inner diameter of 20mm. The two ends of the sulfur transfer agent bed are filled with quartz wool and quartz sand to fix the sulfur transfer agent bed in the constant temperature section in the middle of the reactor. The temperature of the sulfur transfer agent bed is controlled by a thermocouple. The process of pretreatment and evaluation of the sulfur transfer agent to be tested is as follows: (1) After the reactor temperature (650℃) stabilizes, the desulfurizing agent to be tested is pretreated for 60min in N2 atmosphere to fully remove the adsorbed species on the surface of the sulfur transfer agent to be tested; (2) After pretreatment, simulated flue gas containing SO2 is introduced for 10min (gas flow rate data (mL / min), nitrogen: 1757, air: 143, sulfur dioxide: 100, volumetric flow rate under standard conditions, mixed and then introduced into the reactor), the gas after adsorption is collected and the concentration of SO2 in the gas after adsorption in real time is analyzed by an online infrared analyzer. (3) Calculate the desulfurization efficiency: (S 脱硫前 -S 脱硫后 ) / S 脱硫前 S 脱硫前 S represents the volume concentration of SO2 in the simulated gas before desulfurization. 脱硫后 This indicates the volume concentration of SO2 in the simulated gas after desulfurization. The results are shown in Table 2.

[0068] Table 2

[0069] Conventional industrial standard samples 94.5 RS-1 95.1 RS-2 94.2 RS-3 93.9 DB-1 87.1 DB-2 84.4 DB-3 86.4

Claims

1. A method for preparing a composition containing alumina and magnesium oxide, comprising: modifying magnesium oxide with a solution containing magnesium ions and / or calcium ions, and mixing the modified magnesium oxide with a dispersion containing alumina to form a slurry; The magnesium oxide is modified with a solution containing magnesium ions and / or calcium ions, including mixing a magnesium oxide slurry with the solution containing magnesium ions and / or calcium ions, and stirring for at least 5 minutes after mixing; the solid content of the magnesium oxide slurry is 20-45% by weight; the pH value of the solution containing magnesium ions and / or calcium ions is 0.5-2, wherein Ca... 2+ The ion concentration is 0–5% by weight, Mg 2+ The ion concentration is 0–5% by weight, and Ca 2+ and Mg 2+ The total concentration is not less than 0.2% by weight; the amount of the solution containing magnesium ions and / or calcium ions is such that the pH value of the mixture obtained by modifying magnesium oxide with the solution containing magnesium ions and / or calcium ions is 8 to 11. The magnesium oxide is active magnesium oxide, and the citric acid value of the active magnesium oxide measured at 30°C is 100–500 s. -1 ; D of active magnesium oxide particles v 50 is no more than 10 micrometers.

2. The method according to claim 1, characterized in that, The alumina-containing dispersion is a slurry containing boehmite and / or aluminum sol.

3. The method according to claim 1 or 2, characterized in that, The alumina-containing dispersion is acidified, with an acid-to-aluminum ratio of 0.2 to 0.7, where the acid-to-aluminum ratio is the molar ratio of acid to aluminum during acidification. The solid content of the alumina-containing dispersion is 5-20% by weight.

4. The method according to claim 1, characterized in that, The solution containing magnesium ions and / or calcium ions, Ca 2+ and Mg 2+ The total concentration is 0.2-5% by weight.

5. The method according to claim 1 or 4, characterized in that, The solution containing magnesium ions and / or calcium ions is acidic wastewater containing calcium and magnesium ions, wherein Ca 2+ The ion concentration is 0.1–5% by weight, Mg 2+ The ion concentration is 0.1-5% by weight, and the pH value is 0.5-2; the acidic wastewater containing calcium and magnesium ions contains no more than 1% by weight of other impurity ions, wherein the other impurity ions are one or more of Fe, Cu, Co, and Zr.

6. The method according to claim 1, characterized in that, The magnesium oxide is active magnesium oxide, and the D of the active magnesium oxide particles is... v 50 is 2~5 micrometers.

7. The method according to claim 1, characterized in that, The magnesium oxide is modified with a solution containing magnesium ions and / or calcium ions, and then stirred for 10 to 120 minutes after mixing.

8. The method according to claim 5, characterized in that, The acidic wastewater containing calcium and magnesium ions, wherein Ca 2+ The ion concentration is 0.2-1% by weight, Mg 2+ The ion concentration is 0.2-1% by weight; the acidic wastewater containing calcium and magnesium ions may also contain one or more other impurity ions, the content of which does not exceed 1% by weight, and the other impurity ions are one or more of Fe, Cu, Co, and Zr.

9. The method according to claim 1, characterized in that, The modification of magnesium oxide with a solution containing magnesium ions and / or calcium ions is carried out at 5–60°C.

10. The method according to claim 1, characterized in that, The surface modification of magnesium oxide is carried out by first slurrying magnesium oxide in deionized water to prepare a slurry with a solid content of 20-45%. The slurry is then added to acidic wastewater under stirring conditions, and the pH value is controlled at 8-11. Finally, the mixture is stirred for 10-120 minutes at room temperature to 50°C.

11. The application of the method according to any one of claims 1 to 10 in the preparation of catalytic cracking catalysts or catalytic cracking aids containing magnesium and aluminum.

12. A method for utilizing wastewater containing calcium and magnesium ions, the method comprising: A modified activated magnesium oxide slurry was obtained by mixing acidic wastewater containing calcium and magnesium ions (pH 0.5–2) with an activated magnesium oxide slurry. The temperature of the mixed activated magnesium oxide slurry was controlled at room temperature to 50°C, and the pH of the mixed activated magnesium oxide slurry was 8–11. The modified activated magnesium oxide slurry was then used in the preparation of sulfur transfer aids or adsorbents for adsorbing sulfur oxides. The activated magnesium oxide had a citric acid value of 100–500s measured at 30°C. -1 ; D of active magnesium oxide particles v 50 not exceeding 10 micrometers; The acidic wastewater containing calcium and magnesium ions with a pH value of 0.5–2, wherein Ca 2+ The ion concentration is 0.1–5% by weight, Mg 2+ The ion concentration is 0.1-5% by weight, and the pH value is 0.5-2; the acidic wastewater containing calcium and magnesium ions contains no more than 1% by weight of other impurity ions, wherein the other impurity ions are one or more of Fe, Cu, Co, and Zr.

13. A method for preparing a magnesium-containing composition using magnesium oxide, comprising modifying magnesium oxide with a solution containing magnesium ions and / or calcium ions, and then mixing the modified magnesium oxide with other components of the magnesium-containing composition; The magnesium oxide is modified with a solution containing magnesium ions and / or calcium ions, including mixing a magnesium oxide slurry with the solution containing magnesium ions and / or calcium ions, and stirring for at least 5 minutes after mixing; the solid content of the magnesium oxide slurry is 20-45% by weight; the pH value of the solution containing magnesium ions and / or calcium ions is 0.5-2, wherein Ca... 2+ The ion concentration is 0–5% by weight, Mg 2+ The ion concentration is 0–5% by weight, and Ca 2+ and Mg 2+ The total concentration is not less than 0.2% by weight; the amount of the solution containing magnesium ions and / or calcium ions is such that the pH value of the mixture obtained by modifying magnesium oxide with the solution containing magnesium ions and / or calcium ions is 8 to 11. The magnesium oxide is active magnesium oxide, and the citric acid value of the active magnesium oxide measured at 30°C is 100–500 s. -1 ; D of active magnesium oxide particles v 50 is no more than 10 micrometers.