Adsorbing material for treating thallium-containing wastewater and preparation method thereof

Abstract

The invention discloses an adsorption material for treating thallium-containing wastewater and a preparation method thereof, and relates to the technical field of wastewater treatment.The adsorption material comprises biochar and gadolinium oxide doped cerium oxide loaded on the biochar, and the biochar is prepared with walnut green seedcase as a raw material through a carbon thermal method. The biochar-loaded gadolinium oxide-doped cerium oxide adsorbing material disclosed by the invention is good in adsorption performance, high in adsorption efficiency and suitable for adsorption treatment of high-concentration thallium-containing wastewater.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to an adsorption material for treating thallium-containing wastewater and a preparation method thereof. Background Art

[0002] Thallium is a highly toxic rare earth element, which is far more toxic to organisms than common heavy metals such as As, Cr, and Cd. A trace of thallium can cause human poisoning. Currently, thallium is listed as a pollutant that needs to be controlled by the U.S. Environmental Protection Agency and the EU Framework Convention on Water. my country has also clearly stated that thallium is one of the heavy metal pollutants that need to be protected.

[0003] The content of thallium in natural water is very low. Due to the highly toxic nature of thallium, my country has formulated the world's most stringent discharge standard for thallium-containing wastewater, 5 μg·L -1 , which puts forward higher requirements on the treatment technology of thallium-containing industrial wastewater.

[0004] At present, conventional treatment technologies for thallium-containing wastewater mainly include precipitation, adsorption, ion exchange, etc. Although precipitation is a widely used thallium removal method in industrial production, the large amount of sedimentation agent added may introduce new impurities to block the flow channel, increasing the risk of secondary pollution. The ion exchange method has the advantages of simple operation, good selectivity, not easy to produce secondary pollution, and easy recovery of valuable metals. However, the types of impurity ions in industrial wastewater are complex, and the exchange capacity of the resin will be interfered by other ions, resulting in a decrease in exchange capacity and selectivity, and the efficiency is low. The adsorption method has the advantages of large adsorption capacity, simple operation, and high treatment depth. The most widely used adsorption materials are metal oxides, activated carbon and microorganisms. Metal oxide adsorption is the most effective, but factors such as large fluid resistance still limit its application. Based on this, it is very meaningful to produce adsorption materials for thallium-containing wastewater with stronger adsorption performance. Summary of the invention

[0005] In view of the above problems, the present invention provides an adsorption material for treating thallium-containing wastewater and a preparation method thereof.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows: The invention provides an adsorption material for treating thallium-containing wastewater. The adsorption material comprises biochar and gadolinium oxide-doped cerium oxide loaded on the biochar.

[0007] Furthermore, the biochar is prepared by carbon thermal method using walnut green peel as raw material.

[0008] The present invention also provides a method for preparing an adsorbent material for treating thallium-containing wastewater, which specifically comprises the following steps: S1: preparing modified walnut green peel biochar: drying, crushing, sieving, and calcining the walnut green peel to obtain walnut green peel biochar; then mixing the walnut green peel biochar with nitric acid, heating, cooling, washing with water to neutrality, and drying to obtain modified walnut green peel biochar; S2: preparing gadolinium oxide doped cerium oxide: dissolving cerium nitrate and gadolinium nitrate in deionized water to prepare a mixed solution of a certain concentration; adding the mixed solution dropwise into a precipitant under continuous stirring, allowing the mixture to stand for aging after the reaction is completed, and then drying, calcining, ball milling, and sieving to obtain gadolinium oxide doped cerium oxide powder; S3: Preparation of adsorption material: adding water and anhydrous ethanol to biochar, mixing by ultrasonication to obtain a mixed solution; adding gadolinium oxide-doped cerium oxide powder to the mixed solution, heating and stirring to obtain biochar-loaded gadolinium oxide-doped cerium oxide, i.e., adsorption material, after drying, calcining, grinding, and sieving.

[0009] Furthermore, in the step S1, the sieving number is 100 mesh; the calcination temperature is 500°C, the calcination time is 2h, and the heating rate is 3°C / min; the dosage ratio of walnut green peel biochar to nitric acid is 1g:10mL; the heating temperature is 60°C, and the treatment time is 2h.

[0010] Furthermore, in step S2, the molar ratio of cerium nitrate to gadolinium nitrate is 4:1.

[0011] Furthermore, in step S2, the precipitant is an oxalic acid precipitant; the preparation method of the precipitant is: dissolving oxalic acid in deionized water to prepare an oxalic acid solution to obtain the oxalic acid precipitant; the concentration of the precipitant is 0.1 mol / L.

[0012] Furthermore, in step S2, the aging time is 2 hours; the drying temperature is 80°C; the calcination temperature is 600°C, the calcination time is 2 hours, and the heating rate is 3°C / min; the ball milling speed is 1500r / min, and the ball milling time is 12 hours; and the sieving number is 150 meshes.

[0013] Furthermore, in step S3, the usage ratio of biochar, water and anhydrous ethanol is 1 g:20 mL:10 mL; the mass ratio of biochar to gadolinium oxide-doped cerium oxide powder is 10:2-4; the heating temperature is 80° C., and the stirring time is 30 min.

[0014] Furthermore, the drying temperature is 80° C., and the drying time is 24 h; the calcination temperature is 600° C., and the calcination time is 2 h; and the sieving number is 60 meshes.

[0015] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, the biochar prepared by using agricultural waste walnut green peel as raw material has a certain adsorption capacity; by subjecting the biochar to acid treatment, on the one hand, it has more pores, which is convenient for improving the adsorption capacity, and on the other hand, the surface of the biochar contains a variety of functional groups, which is convenient for specific binding with thallium, thereby improving the adsorption selectivity and adsorption capacity of thallium. By loading gadolinium oxide doped cerium oxide, on the one hand, its high specific surface area and regular pore structure are conducive to further improving the adsorption performance; on the other hand, as an electrolyte, it has the functions of adsorption, decolorization and flocculation, which can improve the adsorption efficiency. Based on this, the biochar loaded with gadolinium oxide doped cerium oxide adsorption material of the present invention has good adsorption performance and high adsorption efficiency, and the preparation method is simple, which is suitable for the adsorption treatment of high-concentration (10 mg / L) thallium-containing wastewater. The thallium residue in the thallium-containing wastewater after adsorption treatment is low, which meets the national standards. DETAILED DESCRIPTION

[0016] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] The instruments, reagents, materials, etc. involved in the following examples, unless otherwise specified, are all conventional instruments, reagents, materials, etc. in the prior art and can be obtained through regular commercial channels. The experimental methods, detection methods, etc. involved in the following examples, unless otherwise specified, are all conventional experimental methods, detection methods, etc. in the prior art.

[0018] Example 1 This embodiment provides an adsorption material for treating thallium-containing wastewater, including walnut green peel biochar and gadolinium oxide-doped cerium oxide loaded on the walnut green peel biochar.

[0019] The preparation method of the adsorbent material comprises the following steps: S1: Preparation of modified walnut green peel biochar: Dry, crush and sieve the walnut green peel through a 100-mesh sieve in a tube furnace, heat the temperature to 500°C at a heating rate of 3°C / min, and calcine for 2 hours to obtain walnut green peel biochar; then mix the walnut green peel biochar with nitric acid (dosage ratio of 1g:10mL), heat at 60°C for 2 hours, cool, wash with water to neutrality, and dry to obtain modified walnut green peel biochar; S2: Preparation of gadolinium oxide doped cerium oxide: dissolve cerium nitrate and gadolinium nitrate (molar ratio of 4:1) in deionized water to prepare a mixed solution with a metal ion concentration of 0.2 mol / L; dissolve oxalic acid in deionized water to prepare a 0.1 mol / L oxalic acid solution, and adjust the pH to 6.8 with ammonia water to obtain an oxalic acid precipitant. Under continuous stirring, add the mixed solution dropwise to the oxalic acid precipitant. After the reaction is completed, let it stand for aging for 2 hours, dry at 80°C, heat it to 600°C at a heating rate of 3°C / min, calcine it for 2 hours, ball mill it at 1500r / min for 12 hours, and pass it through a 150-mesh sieve to obtain gadolinium oxide doped cerium oxide powder; S3: Preparation of adsorption material: Add water and anhydrous ethanol (in a dosage ratio of 1 g: 20 mL: 10 mL) to the biochar, mix them evenly by ultrasonication to obtain a mixed solution; add gadolinium oxide-doped cerium oxide powder (the mass ratio of biochar to powder is 10:2) to the mixed solution, heat and stir at 80°C for 30 min, dry at 80°C for 24 h, calcine at 600°C for 2 h, grind, and pass through a 60-mesh sieve to obtain biochar-loaded gadolinium oxide-doped cerium oxide, i.e., the adsorption material.

[0020] Example 2 The difference from Example 1 is that in step S3, the mass ratio of biochar to powder is 10:3.

[0021] Example 3 The difference from Example 1 is that in step S3, the mass ratio of biochar to powder is 10:4.

[0022] Comparative Example 1 Preparation of modified walnut green peel biochar adsorption material: the walnut green peel was dried, crushed, and passed through a 100-mesh sieve, placed in a tubular furnace, heated to 500°C at a heating rate of 3°C / min, and calcined for 2 hours to obtain walnut green peel biochar; then the walnut green peel biochar was mixed with nitric acid (dosage ratio of 1g:10mL), heated at 60°C for 2 hours, then cooled, washed with water to neutrality, and dried to obtain the modified walnut green peel biochar adsorption material.

[0023] Comparative Example 2 Preparation of walnut green peel biochar adsorption material: The walnut green peel was dried, crushed, and passed through a 100-mesh sieve, placed in a tubular furnace, heated to 500°C at a heating rate of 3°C / min, and calcined for 2h to obtain the walnut green peel biochar adsorption material.

[0024] The adsorption performance test of the adsorption materials of the above embodiments 1-3 and comparative examples 1-2 was carried out as follows: thallium-containing wastewater with a pH value of 8 and an initial concentration of 10 mg / L was prepared, 20 mL of thallium-containing wastewater was added to 5 centrifuge tubes respectively, and then 10 mg of the adsorption materials prepared in the above embodiments 1-3 and comparative examples 1-2 were added respectively (i.e., the addition amount was 0.5 g / L), the reaction was carried out for 30 minutes, and the adsorption materials were filtered out after standing, the clean water was discharged, the thallium concentration in the water was detected, and the thallium removal rate was calculated. The results are shown in Table 1.

[0025] Table 1 Thallium removal effects of Examples 1-3 and Comparative Examples 1-2

[0026] It can be seen from the results in Table 1 that the effluent thallium concentration of the high-concentration (10 mg / L) thallium-containing wastewater treated by the adsorption materials of Examples 1-3 is 3.5-4.6 μg / L, which is below the national standard of 5 μg / L. The effluent thallium concentration of the high-concentration (10 mg / L) thallium-containing wastewater treated by the adsorption materials of Comparative Example 1 is 319 μg / L, which is much higher than 5 μg / L and cannot meet the national standard. The effluent thallium concentration of the high-concentration (10 mg / L) thallium-containing wastewater treated by the adsorption materials of Comparative Example 2 is 1518 μg / L, which is much higher than 5 μg / L and cannot meet the national standard. It can be seen that the adsorption material of the present application has good adsorption performance, high adsorption efficiency and short adsorption time. By acid treating the biochar, the adsorption capacity and the adsorption selectivity for thallium are significantly improved; by loading gadolinium oxide doped with cerium oxide, the adsorption performance is further improved. The residual thallium in the thallium-containing wastewater after adsorption treatment is low, which meets the national standards.

[0027] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An adsorbent material for treating thallium-containing wastewater, characterized in that: The adsorption material includes biochar and gadolinium oxide doped cerium oxide loaded on the biochar.

2. The adsorbent material for treating thallium-containing wastewater according to claim 1, characterized in that: The biochar is prepared by carbon thermal method using walnut green peel as raw material.

3. A method for preparing an adsorbent material for treating thallium-containing wastewater as claimed in any one of claims 1 to 2, characterized in that: The specific steps include: S1: preparing modified walnut green peel biochar: drying, crushing, sieving, and calcining the walnut green peel to obtain walnut green peel biochar; then mixing the walnut green peel biochar with nitric acid, heating, cooling, washing with water to neutrality, and drying to obtain modified walnut green peel biochar; S2: preparing gadolinium oxide doped cerium oxide: dissolving cerium nitrate and gadolinium nitrate in deionized water to prepare a mixed solution of a certain concentration; adding the mixed solution dropwise into a precipitant under continuous stirring, allowing the mixture to stand for aging after the reaction is completed, and then drying, calcining, ball milling, and sieving to obtain gadolinium oxide doped cerium oxide powder; S3: Preparation of adsorption material: adding water and anhydrous ethanol to biochar, mixing by ultrasonication to obtain a mixed solution; adding gadolinium oxide-doped cerium oxide powder to the mixed solution, heating and stirring to obtain biochar-loaded gadolinium oxide-doped cerium oxide, i.e., adsorption material, after drying, calcining, grinding, and sieving.

4. The method for preparing an adsorbent material for treating thallium-containing wastewater according to claim 3, characterized in that: In the step S1, the sieving number is 100 mesh; the calcination temperature is 500° C., the calcination time is 2 h, and the heating rate is 3° C. / min; the dosage ratio of walnut green peel biochar to nitric acid is 1 g:10 mL; the heating temperature is 60° C., and the treatment time is 2 h.

5. The method for preparing an adsorbent material for treating thallium-containing wastewater according to claim 3, characterized in that: In the step S2, the molar ratio of cerium nitrate to gadolinium nitrate is 4:

1.

6. The method for preparing an adsorbent material for treating thallium-containing wastewater according to claim 3, characterized in that: In step S2, the precipitant is an oxalic acid precipitant; the preparation method of the precipitant is: dissolving oxalic acid in deionized water to prepare an oxalic acid solution, thereby obtaining the oxalic acid precipitant; the concentration of the precipitant is 0.1 mol / L.

7. The method for preparing an adsorbent material for treating thallium-containing wastewater according to claim 3, characterized in that: In the step S2, the aging time is 2 hours; the drying temperature is 80°C; the roasting temperature is 600°C, the roasting time is 2 hours, and the heating rate is 3°C / min; the ball milling speed is 1500r / min, and the ball milling time is 12 hours; and the sieving number is 150 meshes.

8. The method for preparing an adsorbent material for treating thallium-containing wastewater according to claim 3, characterized in that: In the step S3, the usage ratio of biochar, water and anhydrous ethanol is 1 g:20 mL:10 mL; the mass ratio of biochar to gadolinium oxide-doped cerium oxide powder is 10:2-4; the heating temperature is 80° C., and the stirring time is 30 min.

9. The method for preparing an adsorbent material for treating thallium-containing wastewater according to claim 3, characterized in that: In step S3, the drying temperature is 80° C. and the drying time is 24 h; the calcination temperature is 600° C. and the calcination time is 2 h; and the sieving number is 60 meshes.

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