Method for recovering heavy metal and phosphate radical adsorbent synthesized by food heating package

Abstract

The invention provides a method for recycling a heavy metal and phosphate radical adsorbent synthesized by a food heating bag, and belongs to the technical field of adsorbents. The preparation method comprises the following steps: washing a food heating bag material after reaction, drying, grinding, and sieving with a 100-mesh sieve to obtain heating bag powder; adding an acid solution to dissolve the supernate; adding an alkali solution for co-precipitation, standing and aging, and filtering to obtain a solid; and finally, drying and sieving the solid to obtain the adsorbent. According to the method disclosed by the invention, the calcium-aluminum mixed solution is filtered on the basis of a coprecipitation method, the supernate is used for preparing a product, and a high-value recycling product is obtained through simple process conditions, so that large-scale production is facilitated, the problem of reducing the pressure of a refuse landfill is solved, and the negative influence of a used heating bag on the environment is also relieved.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorbents, and particularly relates to a method for recovering an adsorbent for heavy metals and phosphate radicals synthesized from a food heating pack. Background Art

[0002] Currently, the treatment methods for cadmium-containing wastewater mainly include chemical precipitation, ion exchange, membrane separation, adsorption, and microbial methods. The adsorption method is one of the fastest and most effective methods for treating cadmium pollution in aqueous solutions. It is simple to operate, low in cost, and can be used for the treatment of various industrial wastewaters. Bentonite, rice husk biochar, and diatomite are commonly used adsorbents for adsorbing cadmium in sewage.

[0003] The prior art (Shuang Shengqing. Study on the adsorption characteristics of different adsorbents for Cd(II) in sewage [J]. Soda Industry, 2024(4): 13-16) discloses that: using biochar, sodium-based bentonite, and diatomite as adsorbents respectively, adsorbing a 100 mg / L Cd(II) stock solution, and placing it in a reciprocating air bath oscillator at 180 r / min at 25 °C for 8 h. It is obtained that the high-efficiency adsorption time of the three adsorption materials for Cd(II) is 30 min. When the adsorbent dosage is 1 g / L, the unit adsorption amount of the adsorbent is the largest, 22.89 mg / g for bentonite, 22.33 mg / g for biochar, and 14.79 mg / g for diatomite. However, the removal rate is extremely low at this time.

[0004] Self-heating food is a type of convenient food that uses self-heating technology to quickly reheat food to an edible state. Currently, the self-heating food industry is developing rapidly, and the product categories are increasing. Self-heating food has currently become an important food choice in application scenarios such as disaster relief, emergency rescue, and daily meals, playing a significant role. However, there are very few methods for treating and reasonably utilizing the used food heating packs. The main components of the food heating pack are aluminum powder, calcium oxide, and sodium bicarbonate, and may contain magnesium sulfate and other impurity components. For the used heating packs, if not properly treated, it may affect environmental safety, causing waste of resources and environmental pollution.

[0005] Treating and reusing the used heating packs is an important problem to be solved currently.

[0006] As a highly efficient adsorbent, calcium-aluminum hydrotalcite is widely used in the fields of environmental protection, chemical engineering, etc. In wastewater treatment, calcium-aluminum hydrotalcite can be used as an adsorbent to remove harmful substances in wastewater, reduce pollutant emissions, and relieve the pressure on the environment. In addition, calcium-aluminum hydrotalcite can also be used as a catalyst in the fields of chemical engineering, medicine, etc.

[0007] Calcium-aluminum hydrotalcite has a relatively high specific surface area and good pore structure, and these characteristics enable it to fully adsorb harmful substances in wastewater, such as heavy metal ions, organic pollutants, etc. At the same time, calcium-aluminum hydrotalcite also has good chemical stability and thermal stability, and can maintain stable adsorption performance within a relatively wide temperature and pH range.

[0008] Traditional methods for preparing calcium-aluminum hydrotalcite include the co-precipitation method, hydrothermal synthesis method, etc. The hydrothermal synthesis method is to make calcium and aluminum ions react in an alkaline solution in a high-pressure reaction kettle for a certain period of time under hydrothermal conditions of high temperature and high pressure, and then form calcium-aluminum hydrotalcite. Although hydrothermal conditions can accelerate the reaction and improve the crystallinity and purity of the product, the above reaction conditions require the use of a high-pressure reaction kettle, with a relatively high equipment cost and relatively complex operation. At the same time, the reaction time of the hydrothermal synthesis method is relatively long and is not suitable for large-scale rapid production.

[0009] Applying the food heating pack to prepare an adsorbent for heavy metals and phosphate radicals containing calcium-aluminum hydrotalcite is the technical problem to be solved by the present invention. Summary of the Invention

[0010] In view of this, the present invention provides a method for recycling an adsorbent for synthesizing heavy metals and phosphate radicals from a food heating pack. This method filters the calcium-aluminum mixed solution on the basis of the co-precipitation method and uses the supernatant to prepare the product, avoiding the complex ingredient ratio process, obtaining a high-value and high-performance resource product through simple process conditions. The product is not interfered by other impurities in the initial ingredients of the heating pack, which is conducive to large-scale production, and not only solves the problem of reducing the pressure on landfills, but also reduces the negative impact of the used heating pack on the environment.

[0011] The method for recycling an adsorbent for synthesizing heavy metals and phosphate radicals from a food heating pack according to the present invention includes the following steps:

[0012] (1) Wash, dry, grind, and screen the food heating pack material after the reaction through a 100-mesh sieve to obtain heating pack powder;

[0013] (2) Add the heating pack powder to an acid solution, stir to dissolve and filter to obtain a supernatant containing calcium ions and aluminum ions;

[0014] (3) At room temperature, slowly add an alkali solution dropwise to the supernatant while stirring, adjust the pH to 10-12 to cause a co-precipitation reaction of calcium and aluminum, let it stand for aging, and filter to obtain a solid;

[0015] (4) Wash the solid with deionized water more than 3 times, then dry and screen to obtain the adsorbent;

[0016] The main component of the adsorbent is calcium-aluminum hydrotalcite.

[0017] Preferably, the food heating pack material after the reaction in step (2) contains calcium carbonate and calcium metaaluminate components.

[0018] Preferably, the acid solution in step (2) is at least one of hydrochloric acid solution, sulfuric acid solution, and nitric acid solution.

[0019] Preferably, the concentration of the acid solution in step (2) is 2 - 6 mol / L.

[0020] Preferably, the solid-liquid ratio of the heating pack powder to the acid solution in step (2) is 1 g : 10 - 30 mL.

[0021] Preferably, the method of stirring and dissolving in step (2) is: stir for 10 - 60 min and then stand for 10 - 30 minutes.

[0022] Preferably, the alkali solution in step (3) is at least one of sodium hydroxide solution, potassium hydroxide solution, and ammonia water solution.

[0023] Preferably, the concentration of the alkali solution in step (3) is 2 - 6 mol / L.

[0024] Preferably, the standing and aging time in step (3) is 30 - 60 min.

[0025] Preferably, the drying temperature in step (4) is 65 - 100 °C, and the drying time is 60 - 120 min.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention realizes the resource utilization of the heating pack material, and converts the calcium and aluminum components that need to be treated into adsorbents with high resource utilization value.

[0028] 2. The adsorption material prepared by the present invention has excellent performance, can be used to adsorb heavy metals and phosphate radicals in water, has superior adsorption performance, and alleviates the dilemma of heavy metal and phosphate radical pollution treatment.

[0029] 3. The preparation process of the adsorbent of the present invention is simple, economical, environmentally friendly, and resource-saving. Most of the substances contained in the used food heating pack are metal compounds. By recycling these materials, the pressure on landfills can be reduced, and the negative impact on the environment can be alleviated. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is the process flow diagram for recycling the food heating pack to synthesize the adsorbent for heavy metals and phosphate radicals in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention provides a method for recycling the food heating pack to synthesize the adsorbent for heavy metals and phosphate radicals, and the steps are as follows:

[0032] (1) Wash the food heating pack material after the reaction, dry it, grind it, and sieve it through a 100-mesh sieve to obtain the heating pack powder;

[0033] (2) Add the heating pack powder to an acid solution, stir to dissolve and filter to obtain a supernatant containing calcium ions and aluminum ions;

[0034] (3) At room temperature, while stirring, gradually add an alkali solution dropwise to the supernatant, adjust the pH to 10-12 to cause a coprecipitation reaction of calcium and aluminum, let it stand for aging, and filter to obtain a solid;

[0035] (4) Wash the solid with deionized water more than 3 times, then dry it and sieve it to obtain an adsorbent with the main component being calcium-aluminum hydrotalcite;

[0036] The main component of the adsorbent is calcium-aluminum hydrotalcite.

[0037] Preferably, the food heating pack after the reaction in step (1) contains calcium carbonate and calcium metaaluminate components;

[0038] In a specific embodiment of the present invention, first add a certain amount of water to the heating pack (unreacted) according to the requirements of the packaging instructions for reaction. The reaction mainly generates alkali by adding water to calcium oxide, and aluminum powder reacts with the generated alkali to release a large amount of heat to obtain the food heating pack after the reaction; the food heating pack used contains calcium oxide, aluminum powder and sodium bicarbonate as the main components. Specifically, the food heating pack is composed of the following components by mass content: CaO 35-50%, Al 25-45%, NaHCO 3 7-15%, and the balance is inevitable impurities.

[0039] Or use the recycled food heating pack (which has undergone an exothermic reaction) as a raw material, soak it in water to make the unreacted components in it fully react (soak until there is no heat release) to obtain the food heating pack material after the reaction.

[0040] In a specific embodiment of the present invention, the food heating pack material after the reaction is composed of the following raw materials by mass content: CaCO 3 30-40%, Ca(AlO 2 ) 2 30-40% 、 NaAlO 2 7-15%, and the balance is inevitable impurities.

[0041] In a specific embodiment of the present invention, the washing and drying in step (1) are both conventional methods. The purpose of washing is to remove residual strong alkali, and drying is to evaporate the water added during washing to make the surface of the heating pack powder dry, and it can be processed by conventional methods.

[0042] Preferably, the acid solution in step (2) is any one of hydrochloric acid solution, sulfuric acid solution, and nitric acid solution; the concentration of the acid solution is 2-6 mol / L; the solid-liquid ratio of the heating pack powder to the acid solution is 1 g: 10-30 mL.

[0043] In a specific embodiment of the present invention, the acid solution is hydrochloric acid solution; the concentration of the hydrochloric acid solution is 2 mol / L; the mass-volume ratio of the heating pack powder to the acid solution is 6 g: 100 mL.

[0044] Preferably, the method of stirring and dissolving in step (2) is: stir for 10-60 min and then stand for 10-30 minutes.

[0045] Preferably, the alkali solution in step (3) is any one of sodium hydroxide solution, potassium hydroxide solution, and ammonia water solution; the concentration of the alkali solution is 2-6 mol / L.

[0046] In a specific embodiment of the present invention, the alkali solution is sodium hydroxide solution; the concentration of the sodium hydroxide solution is 2 mol / L.

[0047] Preferably, the standing and aging time in step (3) is 30-60 min.

[0048] Preferably, the drying temperature in step (4) is 65-100 °C, and the drying time is 60-120 min;

[0049] In a specific embodiment of the present invention, the drying temperature in step (4) is 80 °C, the drying time is 120 min, and after drying, it is sieved through a 100-mesh sieve to obtain the adsorbent.

[0050] The adsorbent prepared by the present invention can be used for the adsorption of heavy metal ions (cadmium, chromium, lead, copper, zinc) and phosphate in sewage.

[0051] In a specific embodiment of the present invention, the method of using the adsorbent for the adsorption of cadmium ions in sewage is as follows:

[0052] Weigh 0.1 g of the adsorbent and add it to a solution with a cadmium ion concentration of 100-500 mg / L in 100 ml, and carry out the adsorption reaction in a constant temperature oscillator at a temperature of 25 °C and a rotation speed of 150 rpm / min.

[0053] In a specific embodiment of the present invention, the method of using the adsorbent for the adsorption of phosphate in sewage is as follows:

[0054] Weigh 0.1 g of the adsorbent and add it to 100 ml of a solution with a phosphate concentration of 100 - 500 mg / L. Conduct the adsorption reaction in a constant temperature oscillator at 25 °C with a rotation speed of 150 rpm / min.

[0055] The present invention will be further described below in conjunction with embodiments.

[0056] Embodiment 1

[0057] A method for recovering an adsorbent for heavy metals and phosphate synthesized from a food heating pack comprises the following steps:

[0058] (1) React the food heating pack (with a mass content of 45% CaO, 35% Al, 12% NaHCO 3 12, and the balance being inevitable impurities) with water according to the usage instructions. After the reaction, obtain the food heating pack material after the reaction (with a mass content of 45% CaCO 3 45%, Ca(AlO 2 ) 2 32%, NaAlO 2 13, and the balance being inevitable impurities);

[0059] Wash the 6 g of the food heating pack material after the reaction 3 times with water, dry it at 65 °C for 60 min, grind it, and pass it through a 100-mesh sieve to obtain the heating pack powder;

[0060] (2) Add the heating pack powder to 100 ml of hydrochloric acid with a concentration of 2 mol / L, stir for 30 min, then let it stand for 10 min to dissolve, and filter to obtain the supernatant;

[0061] (3) At room temperature, while stirring, gradually add 2 mol / L NaOH solution dropwise to the supernatant, adjust the pH to 11.75, let it stand and age for 30 min, and filter to obtain a solid;

[0062] (4) Wash the solid 3 times with deionized water, then dry it at 80 °C for 120 min, and pass it through a 100-mesh sieve to obtain the adsorbent (HB-s)

[0063] The process flow chart of the process for recovering the adsorbent synthesized from the food heating pack is as Figure 1 .

[0064] Embodiment 2

[0065] A method for recovering an adsorbent for heavy metals and phosphate synthesized from a food heating pack has the same steps as in Embodiment 1.

[0066] The difference is that the acid solution used in step (2) of Embodiment 2 is 1 mol / L.

[0067] Embodiment 3

[0068] A method for recovering adsorbents for synthetic heavy metals and phosphate radicals from food heating packs, the steps are the same as those in Example 1.

[0069] The difference is that the acid solution used in step (2) of Example 3 is 4 mol / L.

[0070] Example 4

[0071] A method for recovering adsorbents for synthetic heavy metals and phosphate radicals from food heating packs, the steps are the same as those in Example 1.

[0072] The difference is that the acid solution used in step (2) of Example 4 is 6 mol / L.

[0073] Example 5

[0074] A method for recovering adsorbents for synthetic heavy metals and phosphate radicals from food heating packs, the steps are the same as those in Example 1.

[0075] The difference is that the acid solution used in step (2) of Example 5 is 7 mol / L.

[0076] Example 6

[0077] A method for recovering adsorbents for synthetic heavy metals and phosphate radicals from food heating packs, the steps are the same as those in Example 1.

[0078] The difference is that the alkali solution used in step (3) of Example 6 is 1 mol / L.

[0079] Example 7

[0080] A method for recovering adsorbents for synthetic heavy metals and phosphate radicals from food heating packs, the steps are the same as those in Example 1.

[0081] The difference is that the alkali solution used in step (3) of Example 7 is 4 mol / L.

[0082] Example 8

[0083] A method for recovering adsorbents for synthetic heavy metals and phosphate radicals from food heating packs, the steps are the same as those in Example 1.

[0084] The difference is that the alkali solution used in step (3) of Example 8 is 6 mol / L.

[0085] Example 9

[0086] A method for recovering adsorbents for synthetic heavy metals and phosphate radicals from food heating packs, the steps are the same as those in Example 1.

[0087] The difference is that the alkali solution used in step (3) of Example 9 is 7 mol / L.

[0088] The following experiments were carried out using the adsorbents (HB-s) prepared in Examples 1-9:

[0089] Weigh 0.1 g of the adsorbent (HB-s, dosage 1 g / L) into a conical flask, add it to 100 ml of solutions with cadmium ion concentrations of 100 mg / L, 300 mg / L, and 500 mg / L respectively, place it in a constant temperature oscillator at 25 °C and a rotation speed of 150 rpm / min for the adsorption reaction. After adsorption for 2 h, take samples to detect the cadmium concentration. The results are shown in Table 1.

[0090] Weigh 0.1 g of the adsorbent (HB-s) into a conical flask, add it to 100 ml of solutions with phosphate ion concentrations of 100 mg / L, 300 mg / L, and 500 mg / L respectively, place it in a constant temperature oscillator at 25 °C and a rotation speed of 150 rpm / min for the adsorption reaction. After adsorption for 2 h, take samples to detect the phosphate ion concentration. The results are shown in Table 2.

[0091] Comparative Example 1

[0092] After the reaction of the food heating pack material (the specific components are the same as in Example 1) is completed, wash it with water 3 times, dry it at 65 °C for 60 min, dry it at 80 °C, and grind it through a 100-mesh sieve to obtain the adsorbent (HB).

[0093] Comparative Example 2

[0094] Using hydrotalcite (pure LDH) directly synthesized from chemical reagents calcium chloride and aluminum chloride as Comparative Example 2, the preparation method of the pure LDH is as follows:

[0095] (1) Weigh 10.38 g of calcium chloride and 5.34 g of aluminum chloride for standby

[0096] (2) Add the above reagents to 100 ml of hydrochloric acid with a concentration of 2 mol / L, stir for 30 min, then let it stand for 10 min to dissolve and filter to obtain the supernatant;

[0097] (3) At room temperature, while stirring, gradually add 2 mol / L NaOH solution to the supernatant, adjust the pH to 11.75, let it stand and age for 30 min, and filter to obtain the solid;

[0098] (4) Wash the solid 3 times with deionized water, then dry it at 80 °C for 120 min, and pass through a 100-mesh sieve to obtain the adsorbent (pure LDH).

[0099] Comparative Example 3

[0100] A method for recovering an adsorbent for heavy metals and phosphate ions synthesized from a food heating pack, the steps are the same as in Example 1.

[0101] The difference lies in that after adding hydrochloric acid in step (2) of Comparative Example 3 and stirring and standing, filtration is not carried out, and the obtained solution is directly used for subsequent reactions to obtain the adsorbent (HB-n).

[0102] The adsorbents prepared in Comparative Examples 1 to 3 were used in the following experiments:

[0103] Weigh 0.1 g of the adsorbent into a conical flask, add it to solutions with cadmium ion concentrations of 100 mg / L, 300 mg / L, and 500 mg / L respectively, each with a volume of 100 ml. Place it in a constant temperature oscillator at a temperature of 25°C and a rotation speed of 150 rpm / min for the adsorption reaction. After 2 hours of adsorption, take samples to detect the cadmium concentration. The results are shown in Table 1.

[0104] Weigh 0.1 g of the adsorbent into a conical flask, add it to solutions with phosphate ion concentrations of 100 mg / L, 300 mg / L, and 500 mg / L respectively, each with a volume of 100 ml. Place it in a constant temperature oscillator at a temperature of 25°C and a rotation speed of 150 rpm / min for the adsorption reaction. After 2 hours of adsorption, take samples to detect the phosphate ion concentration. The results are shown in Table 2.

[0105] Table 1

[0106]

[0107]

[0108] Table 2

[0109]

[0110]

[0111] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for recovering an adsorbent for synthesizing heavy metals and phosphate in a food heating package, characterized in that: The following steps are involved: (1) washing, drying, grinding, and passing through a 100-mesh sieve to obtain a heating pack powder after the reaction is completed; (2) adding the heating bag powder into an acid solution, stirring to dissolve, and filtering to obtain a supernatant containing calcium ions and aluminum ions; (3) adding an alkaline solution dropwise to the supernatant at room temperature while stirring, adjusting the pH to 10-12, causing calcium and aluminum to coprecipitate, allowing the solution to stand for aging, and filtering to obtain a solid; (4) washing the solid with deionized water for more than 3 times, then drying and sieving to obtain the adsorbent; The main component of the adsorbent is calcium aluminum hydrotalcite.

2. The method for recovering the adsorbent of heavy metals and phosphates synthesized from food heating packs according to claim 1, characterized in that: After the reaction in step (1) is completed, the food heating bag contains calcium carbonate and calcium aluminate.

3. The method for recovering the adsorbent of heavy metals and phosphates synthesized from food heating packs according to claim 1, characterized in that: The acid solution in step (2) is at least one of hydrochloric acid solution, sulfuric acid solution and nitric acid solution.

4. The method for recovering the adsorbent of heavy metals and phosphates synthesized from food heating packs according to claim 1, characterized in that: The concentration of the acid solution in step (2) is 2 to 6 mol / L.

5. The method for recovering the adsorbent of heavy metals and phosphates synthesized from food heating packs according to claim 1, characterized in that: The solid-to-liquid ratio of the heating bag powder and the acid solution in step (2) is 1 g: 10-30 mL.

6. The method for recovering the adsorbent of heavy metals and phosphates synthesized from food heating packs according to claim 1, characterized in that: The stirring and dissolving method in step (2) is: stirring for 10 to 60 minutes and then standing for 10 to 30 minutes.

7. The method for recovering the adsorbent of heavy metals and phosphates synthesized from food heating packs according to claim 1, characterized in that: The alkaline solution in step (3) is at least one of a sodium hydroxide solution, a potassium hydroxide solution, and an ammonia solution.

8. The method for recovering the adsorbent of heavy metals and phosphates synthesized from food heating packs according to claim 1, characterized in that: The concentration of the alkaline solution in step (3) is 2 to 6 mol / L.

9. The method for recovering the adsorbent of heavy metals and phosphates synthesized from food heating packs according to claim 1, characterized in that: The standing aging time in step (3) is 30 to 60 minutes.

10. The method for recovering the adsorbent of heavy metals and phosphates synthesized from food heating packs according to claim 1, characterized in that: The drying temperature in step (4) is 65-100° C., and the drying time is 60-120 min.

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