Sulfur-rich pei-based adsorbent and preparation method and use thereof

Abstract

A method for prepanng a sulfur-rich polyethyleneimine (PEI)-based adsorbent, comprises mixing PEI, an episulfide and an organic solvent to obtain a mixture, and subjecting the mixture to ring-opening

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of composite materials, and in particular to a sulfur-rich polyethyleneimine (PEI)-based adsorbent and a preparation method and use thereof. BACKGROUND

[0002] Noble metals such as gold and palladium are widely used in jewelry, corrosion-resistant materials, electronic technology, chemical catalysts and other fields due to their gloss and properties of ductility, non-corrosiveness, and high stability. However, as a non-renewable resource, the noble metals such as gold and palladium are very sparsely distributed worldwide, and thus secondary recovery of them is particularly important. Therefore, selective recovery of gold ions and palladium ions from industrial wastewater has attracted the attention of a large number of researchers.

[0003] The recovery of the noble metals mainly includes membrane separation technology, solvent extraction technology, chemical sedimentation technology, electrochemical technology, and adsorption separation technology. As one of the most widely used physicochemical technologies, adsorption method has easy operation and a large scale, and could efficiently remove spent noble metals with a low concentration from the industrial wastewater. Currently, adsorbents commonly used for the recovery of the noble metals include activated carbons, metal organic framework MOFs materials, biological adsorbents, and organic polymer materials. The organic polymeric material adsorbents have low cost, simple preparation and operation, clear mechanism analysis, thus being widely used. With many side chain amine groups, a molecule-structured PEI porous material could be added with a crosslinking agent to synthesize a water-insoluble organic polymer, which has advantages such as a large adsorption amount, a rapid adsorption rate and a low boiling point in an adsorption region, capable of being desorbed and degraded, enriched with the noble metals easily, multiple recovery, and acid and alkali resistance, thus being widely used in industrial recovery and other aspects. For example, Chinese patent with publication number CN 107837791 A discloses a PEI-modified cellulose membrane adsorbent and a preparation method thereof, in which a PEI-modified cellulose membrane body is used to improve adsorptivity for heavy metal ions. However, an adsorption amount for metal ions is relatively low, and could only reach 105.3 mg / g. As another example, Chinese patent with publication number CN 108855014 A discloses a heavy-metal adsorbent and a preparation method and use thereof, in which sodium alginate is oxidized by potassium periodate to form a dialdehyde structure, and then primary amine on a branched polyethyleneimine and an aldehyde group are subjected to Schiff base reaction for grafting, and then reduction to obtain a copolymer. Although this method could improve the adsorption ability for heavy metal ions compared to an adsorbent without addition of PEI, an adsorption capacity is relatively low. Chinese patent with publication number CN 115626681 A discloses a new method for adsorbing and recovering gold ions and palladium ions with a PEI-based network polymer, in which the PEI and an alkyl dialdehyde are subjected to solution polymerization to prepare an adsorbent with an adsorption amount of up to 2,575 mg / g for trivalent gold ions and an adsorption amount of up to 497 mg / g for divalent palladium ions. It can be seen that although the PEI is used to prepare adsorbents in prior art, an adsorption capacity for the metal ions is still relatively low.

[0004] Therefore, a method for preparing a sulfur-rich PEI-based adsorbent with a high adsorption capacity and selectivity is desirable. SUMMARY

[0005] Objects of the present disclosure are to provide a sulfur-rich PEI-based adsorbent with a high adsorption capacity and selectivity, and a preparation method and use thereof.

[0006] In order to achieve the aforementioned objects, the present disclosure provides the following technical solutions.

[0007] The present disclosure provides a method for preparing a sulfur-rich PEI-based adsorbent, including the steps of: mixing PEI, an episulfide and an organic solvent to obtain a mixture, and subjecting the mixture to ring-opening reaction to obtain the sulfur-rich PEI-based adsorbent.

[0008] In some embodiments, the PEI has a number-average molecular weight of 600-70,000.

[0009] In some embodiments, the episulfide includes at least one selected from the group consisting of ethylene sulfide, 2-(chloromethyl) ethylene sulfide, propylene sulfide, isobutylene sulfide and trimethylene sulfide.

[0010] In some embodiments, the ratio of an amount of substance of the PEI to an amount of substance of the episulfide is in a range of 5 : 1 to 1 : 5.

[0011] In some embodiments, the organic solvent includes one selected from the group consisting of ethanol and N,N-dimethylformamide.

[0012] In some embodiments, the ring-opening reaction is conducted at a temperature of 0-45°C for 1-72 h.

[0013] The present disclosure also provides a sulfur-rich PEI-based adsorbent prepared by the method described in the aforementioned technical solutions.

[0014] The present disclosure also provides use of the sulfur-rich PEI-based adsorbent described in the aforementioned technical solutions in treatment of a wastewater containing noble metal ions, where the use is realized by a process including the steps of: mixing the sulfur-rich PEI-based adsorbent, hydrochloric acid, and the wastewater containing the noble metal ions to obtain a mixed solution; subjecting the mixed solution to adsorption reaction, and subjecting a resulting reaction product to solid-liquid separation to obtain a saturated adsorbent and a treated wastewater; where the saturated adsorbent is reused after desorption.

[0015] In some embodiments, the wastewater containing the noble metal ions has a gold ion concentration of 0-2,000 mg / L, and a palladium ion concentration of 0-1,000 mg / L.

[0016] In some embodiments, the adsorption reaction is conducted at room temperature for 0-72 h.

[0017] The present disclosure provides a method for preparing a sulfur-rich PEI-based adsorbent, including the steps of: mixing PEI, an episulfide and an organic solvent to obtain a mixture, and subjecting the mixture to ring-opening reaction to obtain the sulfur-rich PEI-based adsorbent. PEI and the episulfide are subjected to ring-opening reaction to obtain the sulfur-rich PEI-based adsorbent, which has a hierarchically porous structure including micropores, mesopores and macropores, and additionally the sulfur-rich PEI-based adsorbent adsorbs gold ions and palladium ions onto a surface and channels of the sulfur-rich PEI-based adsorbent through mechanisms such as electrostatic attraction, chelation-coordination, and oxidation-reduction. The results of examples show that the sulfur-rich PEI-based adsorbent prepared by the present disclosure not only has an adsorption capacity of up to 5558.43 mg / g for the gold ions and an adsorption capacity of up to 1067.34 mg / g for the palladium ions at 25°C, but also has excellent selectivity. Among Pb (II), Zn (II), K (I), Na (I), Ni (II), Co (II), Cu (II), Fe (III), Al (III) nitrate hetero-ions etc., the gold ions and the palladium ions could be selectively adsorbed and recovered. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The present disclosure provides a method for preparing a sulfur-rich PEI-based adsorbent, including the steps of: mixing PEI, an episulfide and an organic solvent to obtain a mixture, and subjecting the mixture to ring-opening reaction to obtain the sulfur-rich PEI-based adsorbent.

[0019] In the present disclosure, unless otherwise specified, reagents used in the present disclosure are all commercially available products commonly used in the art.

[0020] In some embodiments of the present disclosure, the PEI has a number-average molecular weight of 600-70,000, and preferably 1,000-10,000. In the present disclosure, amine groups and vinyl groups present in the PEI are combined with different substances to improve adsorptivity of adsorbent; additionally, the PEI is highly cationic in water, and could neutralize and adsorb anions or chelate heavy metal ions, thereby improving adsorptivity for noble metal ions; furthermore, the amine groups in PEI structure could react with epoxy compounds, and introduce a large amount of sulfur to the PEI, thereby improving adsorptivity for the heavy metal ions. Therefore, the present disclosure employs the PEI as a raw material to prepare the adsorbent, and employs the PEI with the aforementioned number-average molecular weight, which is more conducive to improving an adsorption capacity of the adsorbent for noble metal ions.

[0021] In some embodiments of the present disclosure, the episulfide includes at least one selected from the group consisting of ethylene sulfide, 2-(chloromethyl) ethylene sulfide, propylene sulfide, isobutylene sulfide, and trimethylene sulfide, and preferably ethylene sulfide, the 2-(chloromethyl) ethylene sulfide, the isobutylene sulfide, and the trimethylene sulfide. The present disclosure uses the episulfide as a raw material to prepare the adsorbent, and introduces sulfur to the adsorbent, which could improve the adsorption capacity for noble metal ions.

[0022] In some embodiments of the present disclosure, a ratio of an amount of substance of the PEI to an amount of substance of the episulfide is in a range of 5 : 1 - 1:5, and preferably 3:1-1 : 5. In the present disclosure, the ratio of the amount of substance of the PEI to the amount of substance of the episulfide is controlled to be in the aforementioned range, which is more conducive to improving the adsorptivity of the adsorbent.

[0023] In some embodiments of the present disclosure, the organic solvent includes one selected from the group consisting of ethanol and N,N-dimethylformamide, and preferably the ethanol. The present disclosure adopts the aforementioned organic solvent, which is more environment-friendly.

[0024] In the present disclosure, there are no particular limitations on an amount of the organic solvent, which may be adjusted according to an amount of the PEI, so as to realize full ring-opening reaction. In some embodiments of the present disclosure, when a mass of the PEI is 0.10-0.12 g, a volume of the organic solvent is 0.3-0.45 mL.

[0025] In the present disclosure, there are no particular limitations on a way for mixing the PEI, the episulfide and the organic solvent, and a conventional way for dissolving the PEI and the episulfide in the organic solvent may be adopted. In some embodiments of the present disclosure, the way for mixing the PEI, the episulfide and the organic solvent includes the steps of dissolving the PEI in the organic solvent to obtain a PEI solution, and dripping the episulfide into the PEI solution.

[0026] In some embodiments of the present disclosure, the ring-opening reaction is conducted at a temperature of 0-45°C, and preferably 45°C. In some embodiments of the present disclosure, the ring-opening reaction is conducted for 1-72 h, and preferably 6-24 h. In the present disclosure, the temperature and a duration of the ring-opening reaction are controlled to be in the aforementioned ranges, which is more conducive to full ring-opening reaction.

[0027] In some embodiments of the present disclosure, the reaction product obtained through the ring-opening reaction is subjected to centrifugation, washing and drying in sequence to obtain the sulfur-rich PEI-based adsorbent. In the present disclosure, unreacted impurities and the solvent could be removed from the sulfur-rich PEI-based adsorbent by the centrifugation, the washing and the drying. In the present disclosure, there are no particular limitations on operating methods for the centrifugation, the washing and the drying, and conventional methods for the centrifugation, the washing and the drying may be adopted. In some embodiments of the present disclosure, a reagent for the washing is 95% ethanol and ultrapure water; the drying is lyophilization, the lyophilization is conducted at a temperature of -40°C to -50°C for 6-24 h.

[0028] In the method provided by the present disclosure, the solvent is environment-friendly, a process is simple, synthesis is fast, materials have stable properties, and the adsorbent prepared by the same is acid and alkali resistant, with sufficient adsorption saturation sites, and an excellent adsorption effect.

[0029] The present disclosure also provides a sulfur-rich PEI-based adsorbent prepared by the method described in the aforementioned technical solution. In the present disclosure, the sulfur-rich PEI-based adsorbent has a hierarchically porous structure including micropores, mesopores and macropores.

[0030] The present disclosure also provides use of the sulfur-rich PEI-based adsorbent described in the aforementioned technical solution in treatment of a wastewater containing noble metal ions, where the use is realized by a method including the steps of: mixing the sulfur-rich PEI-based adsorbent, hydrochloric acid, and the wastewater containing the noble metal ions to obtain a mixed solution; subjecting the mixed solution to adsorption reaction, and subjecting a resulting reaction product to solid-liquid separation to obtain a saturated adsorbent and a treated wastewater; where the saturated adsorbent is repeated after desorption.

[0031] In the present disclosure, the sulfur-rich PEI-based adsorbent, hydrochloric acid and a wastewater containing noble metal ions are mixed to obtain a mixed solution.

[0032] In some embodiments of the present disclosure, a ratio of a mass of the sulfur-rich PEI-based adsorbent to a volume of the wastewater containing the noble metal ions is in a range of (0.001-1) g : (1-1,000) mL, and preferably (0.003-0.5) g : (20-100) mL.

[0033] In some embodiments of the present disclosure, the wastewater containing the noble metal ions has a gold ion concentration of 0-2,000 mg / L, and preferably 390-1,900 mg / L. In some embodiments of the present disclosure, the wastewater containing the noble metal ions has a palladium ion concentration of 0-1,000 mg / L, and preferably 200-2,000 mg / L.

[0034] In some embodiments of the present disclosure, the hydrochloric acid has a concentration of 0.1-2 mol / L, and preferably 0.1-1 mol / L. In the present disclosure, the hydrochloric acid functions to adjust a pH of the wastewater containing the noble metal ions and thereby improve adsorption ability of the sulfur-rich PEI-based adsorbent for the noble metal ions. In the present disclosure, there are no particular limitations on an amount of the hydrochloric acid, so long as a pH of the mixed solution may meet the requirement.

[0035] In some embodiments of the present disclosure, the pH of the mixed solution is 1-13, and preferably 1-6. In the present disclosure, the pH of the mixed solution is controlled to be in the aforementioned range, and thereby the adsorption ability of the sulfur-rich PEI-based adsorbent for the noble metal ions could be improved.

[0036] After obtaining the mixed solution, the mixed solution is subjected to adsorption reaction, a resulting reaction product is then subjected to solid-liquid separation to obtain a saturated adsorbent and a treated wastewater.

[0037] In some embodiments of the present disclosure, the adsorption reaction is conducted at room temperature, and preferably 25°C. In some embodiments of the present disclosure, the adsorption reaction is conducted for 0-72 h, and preferably 12-48 h. In the present disclosure, with the aforementioned temperature and a duration, adsorption equilibrium could be achieved, and the noble metal ions in wastewater could be fully adsorbed.

[0038] In some embodiments of the present disclosure, the adsorption reaction is conducted under shaking, which could improve mass transfer and maximize adsorption. In the present disclosure, there are no particular limitations on a shaking device, a conventional shaking device may be adopted. In some embodiments of the present disclosure, the shaking device is a shaker instrument.

[0039] In the present disclosure, there are no particular limitations on the process for the solid-liquid separation, and a conventional process for solid-liquid separation may be adopted.

[0040] In the present disclosure, there are no particular limitations on the process for the desorption, and a conventional process for removing metal ions from the adsorbent may be adopted. In the present disclosure, due to its better stability, the prepared sulfur-rich PEI-based adsorbent may be reused after desorption.

[0041] The sulfur-rich PEI-based adsorbent prepared in the present disclosure has a hierarchically porous structure including micropores, mesopores and macropores, and additionally the sulfur-rich PEI-based adsorbent adsorbs gold ions and palladium ions onto a surface and channels of the sulfur-rich PEI-based adsorbent through mechanisms such as electrostatic attraction, chelation-coordination, and oxidation-reduction, and thus could be used to selectively adsorb the gold ions and the palladium ions in a wastewater.

[0042] The technical solutions of the present disclosure will be clearly and completely described below in conjunction with examples of the present disclosure. Apparently, the described examples are merely a part rather than all of the examples of the present disclosure. All other examples obtained by those skilled in the art based on the examples of the present disclosure without creative efforts should fall within the scope of the present disclosure.

[0043] Example 1

[0044] A method for preparing a sulfur-rich PEI-based adsorbent was performed by the following steps: 0.12 g of PEI with a number-average molecular weight of 10,000 was dissolved in 4.5 mL of ethanol under sonication to obtain a PEI solution, and then with a ratio of an amount of substance of the PEI to an amount of substance of ethylene sulfide being 1 : 5, the ethylene sulfide was dripped into the PEI solution, and a resulting mixture was subjected to reaction at 10°C for 6 h. Then, in a high-speed centrifuge, a resulting system was subjected to centrifugation at 6,000 r / min for 10 min, and then a solid precipitate at the lower layer was taken, washed with 95% ethanol and ultrapure water respectively to remove impurities that have not been fully reacted, and then lyophilized and left to stand overnight to obtain a flour-like sulfur-rich PEI-based adsorbent.

[0045] Example 2

[0046] A method for preparing a sulfur-rich PEI-based adsorbent was performed by the following steps: 0.12 g of PEI with a number-average molecular weight of 10,000 was dissolved in 4.5 mL of ethanol under sonication to obtain a PEI solution, and then with a ratio of an amount of substance of the PEI to an amount of substance of 2-(chloromethyl) ethylene sulfide being 1 : 5, the 2-(chloromethyl) ethylene sulfide was dripped into the PEI solution, and a resulting mixture was subjected to reaction at 10°C for 6 h. Then, in a high-speed centrifuge, a resulting system was subjected to centrifugation at 6,000 r / min for 10 min, and then a solid precipitate at the lower layer was taken, washed with 95% ethanol and ultrapure water respectively to remove impurities that have not been fully reacted, and then lyophilized and left to stand overnight to obtain a flour-like sulfur-rich PEI-based adsorbent.

[0047] Example 3

[0048] A method for preparing a sulfur-rich PEI-based adsorbent was performed by the following steps: 0.12 g of PEI with a number-average molecular weight of 10,000 was dissolved in 4.5 mL of ethanol under sonication to obtain a PEI solution, and then with a ratio of an amount of substance of the PEI to an amount of substance of isobutylene sulfide being 1 : 5, the isobutylene sulfide was dripped into the PEI solution, and a resulting mixture was subjected to reaction at 10°C for 6 h. Then, in a high-speed centrifuge, a resulting system was subjected to centrifugation at 6,000 r / min for 10 min, and then a solid precipitate at the lower layer was taken, washed with 95% ethanol and ultrapure water respectively to remove impurities that have not been fully reacted, and then lyophilized and left to stand overnight to obtain a flour-like sulfur-rich PEI-based adsorbent.

[0049] Example 4

[0050] A method for preparing a sulfur-rich PEI-based adsorbent was performed by the following steps: 0.12 g of PEI with a number-average molecular weight of 10,000 was dissolved in 4.5 mL of ethanol under sonication to obtain a PEI solution, and then with a ratio of an amount of substance of the PEI to an amount of substance of propylene sulfide being 1 : 5, the propylene sulfide was dripped into the PEI solution, and a resulting mixture was subjected to reaction at 10°C for 6 h. Then, in a high-speed centrifuge, a resulting system was subjected to centrifugation at 6,000 r / min for 10 min, and then a solid precipitate at the lower layer was taken, washed with 95% ethanol and ultrapure water respectively to remove impurities that have not been fully reacted, and then lyophilized and left to stand overnight to obtain a flour-like sulfur-rich PEI-based adsorbent.

[0051] Example 5

[0052] A method for preparing a sulfur-rich PEI-based adsorbent was performed by the following steps: 0.12 g of PEI with a number-average molecular weight of 10,000 was dissolved in 4.5 mL of ethanol under sonication to obtain a PEI solution, and then with a ratio of an amount of substance of the PEI to an amount of substance of trimethylene sulfide being 1 : 5, the trimethylene sulfide was dripped into the PEI solution, and a resulting mixture was subjected to reaction at 10°C for 6 h. Then, in a high-speed centrifuge, a resulting system was subjected to centrifugation at 6,000 r / min for 10 min, and then a solid precipitate at the lower layer was taken, washed with 95% ethanol and ultrapure water respectively to remove impurities that have not been fully reacted, and then lyophilized and left to stand overnight to obtain a flour-like sulfur-rich PEI-based adsorbent.

[0053] Use example 1

[0054] 950 mg / L of an aqueous Au (III) solution and 200 mg / L of an aqueous Pd (II) solution were prepared, respectively. 13 centrifuge tubes were taken, and 20 mL of the aqueous Au (III) solution was added to the centrifuge tubes, respectively. And pHs of the aqueous Au (III) solutions in the centrifuge tubes were respectively adjusted, so that the pHs of the aqueous Au (III) solutions were sequentially 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 and 13. 6 additional centrifuge tubes were taken, and 20 mL of the aqueous Pd (II) solution was added to the centrifuge tubes, respectively. And pHs of the aqueous Pd (II) solutions in the centrifuge tubes were adjusted respectively, so that the pHs of the aqueous Pd (II) solutions were sequentially 1, 2, 3, 4, 5 and 6.

[0055] 3 mg of the adsorbent prepared in example 1 was respectively added to each of the aforementioned centrifuge tubes, and then the centrifuge tubes were placed in a thermostatic 25°C water bath shaker instrument and shaken for 48 h. After adsorption was completed, a metal ion solution at the upper layer was taken, and subjected to dilution in a corresponding dilution rate. An atomic absorption spectrophotometer (AA-6680) was used to measure a concentration after the dilution, and corresponding adsorption rate and adsorption capacity were calculated by the following formula: q (Co-Ct)xK

[0056] Formula (I) _ (Co-Ce)xK

[0057] Formula (II) 7?%=-^^^xl00

[0058] Co Formula (III)

[0059] Where, subscripts t and e respectively denote time t and equilibrium state, and a subscript 0 denotes an initial value; qt denotes an adsorption capacity at time t, qe denotes an adsorption capacity at equilibrium; R% denotes an adsorption rate.

[0060] The effect of a pH on the adsorption rate and adsorption capacity for Au (III) was calculated, and results are as shown in Table 1.

[0061] Table 1 Results of the effect of pH on the adsorption rate for Au (III)

[0062] PH 1 2 3 4 5 6 7 8 9 10 11 12 13 Adsorp tion rate 55.0 6% 52.8 8% 52.2 0% 50.6 2% 47.9 0% 44.5 7% 32.9 1% 15.2 6% 14.8 9% 13.6 7% 11.4 0% 6.4 9% 6.8 0%

[0063] Results of the effect of pH on the adsorption rate and adsorption capacity for Pd (II) are shown in Table 2.

[0064] Table 2 Results of the effect of pH on the adsorption rate for Pd (II)

[0065] PH 1 2 3 4 5 6 Adsorption rate 71.32% 60.46% 54.46% 40.55% 40.08% 41.38%

[0066] As can be seen from Tables 1 and 2, as the pH decreases, the adsorption effect becomes better and better for both Au (III) ions and Pd (II) ions. When the pH is 1, for the Au (III), a maximum adsorption capacity reaches 3,492.98 mg / g, and the adsorption rate is 55.06%; and for the Pd (II), the adsorption capacity reaches 844.92 mg / g, and the adsorption rate is 71.32%.

[0067] Use Example 2

[0068] 390 mg / L of an aqueous Au (III) solution and 200 mg / L of an aqueous Pd (II) solution were prepared, and hydrochloric acid was added thereto to adjust pH to 1. 20 mL of the solutions were respectively taken and respectively added to two 50 mL centrifuge tubes, and then 3 mg of the adsorbent prepared in example 1 was respectively added to the centrifuge tube containing the aqueous Au (III) solution and the centrifuge tube containing the aqueous Pd (II) solution. The centrifuge tubes were placed in a thermostatic 25°C water bath shaker instrument, and shaken for 0-72 h. After adsorption was completed, a metal ion solution at the upper layer was taken according to different classified time, and subjected to dilution in a corresponding rate. An atomic absorption spectrophotometer (AA-6680) was used to measure a concentration after the dilution, and corresponding adsorption rate and adsorption capacity were calculated. For Au (III) and Pd (II), equilibrium was achieved in 24 h, and adsorption rates at the equilibrium were 72.52% and 54.86%, respectively.

[0069] Use example 3

[0070] 10 mg / L of an aqueous Au (III) solution and 10 mg / L of an aqueous Pd (II) solution were prepared, and hydrochloric acid was added thereto to adjust the pH to 1. 20 mL of the solutions were respectively taken and respectively added to two 50 mL centrifuge tubes, and 3 mg of the adsorbent prepared in example 1 was respectively added to the aforementioned centrifuge tubes, and then the centrifuge tubes were placed in a thermostatic 25°C water bath shaker instrument and shaken for 0-12 h. After adsorption was completed, a metal ion solution at the upper layer was taken according to different classified time, and subjected to dilution in a corresponding rate. An atomic absorption spectrophotometer (AA-6680) was used to measure a concentration after the dilution, and corresponding adsorption rate and adsorption capacity were calculated. For Au (III) and Pd (II), equilibrium was achieved respectively in 10 min and 20 min, and adsorption rates were respectively 97.54% and 100%. An adsorption rate for Au (III) reached 100% in 45 min.

[0071] Use example 4

[0072] 20 mL of an Au (III) solution with a concentration of 950 mg / L was respectively added to five 50 mL centrifuge tubes, and 20 mL of hydrochloric acid solutions respectively having concentrations of 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L and 2 mol / L were added to the aforementioned five centrifuge tubes in sequence. 3 mg of the adsorbent prepared in example 1 was respectively added to the aforementioned five centrifuge tubes, and then the centrifuge tubes were placed in a thermostatic 25°C water bath shaker instrument and shaken for 48 h. After adsorption was completed, a metal ion solution at the upper layer was taken, and subjected to dilution in s corresponding rate. An atomic absorption spectrophotometer (AA-6680) was used to measure a concentration after the dilution, and corresponding adsorption rate and adsorption capacity were calculated. Results show that: when the hydrochloric acid solution with the concentration of 0.1 mol / L was added, the adsorption rate for the Au (III) solution was 61.64%; when the hydrochloric acid solution with the concentration of 0.5 mol / L was added, the adsorption rate for the Au (III) solution was 62.95%; when the hydrochloric acid solution with the concentration of 1 mol / L was added, the adsorption rate for the Au (III) solution was 49.78%; when the hydrochloric acid solution with the concentration of 1.5 mol / L was added, the adsorption rate for the Au (III) solution was 45.41%; and when the hydrochloric acid solution with the concentration of 2 mol / L was added, the adsorption rate for the Au (III) solution was 44.87%.

[0073] Use example 5

[0074] The steps in use example 5 were the same as those in use example 4, with the only exception that a metal solution was a Pd (II) solution with a concentration of 167 mg / L. Result show that when the hydrochloric acid solution with the concentration of 0.1 mol / L was added, the adsorption rate for the Pd (II) solution was 68.02%; when the hydrochloric acid solution with the concentration of 0.5 mol / L was added, the adsorption rate for the Pd (II) solution was 66.91%; when the hydrochloric acid solution with the concentration of 1 mol / L was added, the adsorption rate for the Pd (II) solution was 63.87%; when the hydrochloric acid solution with the concentration of 1.5 mol / L was added, the adsorption rate for the Pd (II) solution was 62.31%; when the hydrochloric acid solution with the concentration of 2 mol / L was added, the adsorption rate for the Pd (II) solution was 60.42%.

[0075] Use example 6

[0076] Aqueous Au (III) solutions that have a pH of 1 and that respectively have concentrations of 10 mg / L, 50 mg / L, 70 mg / L, 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, 450 mg / L, 550 mg / L, 736 mg / L, 900 mg / L, 1,000 mg / L, 1,100 mg / L, 1,200 mg / L, 1,300 mg / L, 1,400 mg / L, 1,500 mg / L, 1,600 mg / L, 1,800 mg / L, 1,900 mg / L and 2,100 mg / L were respectively prepared, and 20 mL of the aqueous Au (III) solutions were respectively pipetted and added to 21 centrifuge tubes;

[0077] Then, aqueous Pd (II) solutions that have a pH of 1 and that respectively have concentrations of 12 mg / L, 30 mg / L, 57 mg / L, 79 mg / L, 100 mg / L, 158 mg / L, 216 mg / L, 224 mg / L, 277 mg / L, 318 mg / L, 325 mg / L, 398 mg / L, 399 mg / L, 438 mg / L, 460 mg / L, 513 mg / L, 541 mg / L and 550 mg / L were prepared, and 20 mL of the aqueous Pd (II) solutions were respectively pipetted and placed in eighteen 50 mL centrifuge tubes.

[0078] 3 mg of the adsorbent prepared in example 1 was respectively added to the aforementioned centrifuge tubes, and then the centrifuge tubes were sealed and placed in a thermostatic 25°C water bath shaker instrument and shaken for 72 h. After adsorption was completed, dilution was performed, and then an atomic absorption spectrophotometer (AA-6680) was used to measure a concentration after the dilution, a corresponding adsorption rate was calculated, and results are as shown in Table 3.

[0079] Table 3 Results of the effect of solution concentration on the adsorption rate

[0080] Aqueous Au (III) solution concentration (mg / L) Adsorption rate (%) Aqueous Pd (II) solution concentration (mg / L) Adsorption rate (%) 10 100 12 100 50 100 30 100 70 100 57 100 100 100 79 100 200 100 100 100 300 99.89 158 82.84 400 99.57 216 61.82 450 99.66 224 49.44 550 99.61 277 46.43 736 99.44 318 50.20 900 87.97 325 38.19 1000 75.32 398 32.94 1100 66.09 399 33.16 1200 63.12 438 33.18 1300 56.13 460 23.18 1400 52.17 513 30.24 1500 50.23 541 21.02 1600 53.94 550 21.66 1800 48.30 - - 1900 41.98 - - 2100 38.93 - -

[0081] The results show that: as an initial concentration increases, the adsorption rate decreases, and the adsorbent has a maximum adsorption capacity of 5558.43 mg / g for Au (III), and a maximum adsorption capacity of 1067.34 mg / g for Pd (II).

[0082] Use example 7

[0083] A mixed solution was prepared so that an ion concentration ratio of Au (III), Pd (II) and hetero-ions was 10 mg / L : 10 mg / L : 100 mg / L. Where, the hetero-ions included 9 species such as Pb (II), Zn (II), K (I), Na (I), Ni (II), Co (II), Cu (II), Fe (III), Al (III), etc., and were provided in a form of nitrate, and a ratio of amounts of 9 species of ions was 1:1:1:1:1:1:1:1:1. 20 mL of the mixed solution was pipetted into a 50 mL centrifuge tube, and the 50 mL centrifuge tube was added with 3 mg of the adsorbent prepared in example 1, sealed, placed in a thermostatic 25°C water bath shaker instrument, and shaken for 2 h. After adsorption was completed, dilution was performed, and then an atomic absorption spectrophotometer (AA-6680) and inductively coupled plasma-mass spectrometry (ICP-MS) were used to measure a concentration after the dilution. Corresponding adsorption rate and adsorption capacity were calculated. Experiment results show that the Au (III) and the Pd (II) are fully adsorbed in 2 h, while the adsorption rates for other hetero-ions were as follows: Pb (II) was 3.4%, Zn (II) was 0%, K (I) was 4.11%, Na (I) was 2.4%, Ni (II) was 0.8%, Co (II) was 1.8%, Cu (II) was 0%, Fe (III) was 1.52%, and Al (III) was 0%. This indicates that the adsorbent prepared in example 1 has an excellent selectivity for gold ions and palladium ions.

[0084] Use example 8

[0085] 950 mg / L of an aqueous Au (III) solution and 200 mg / L of an aqueous Pd (II) solution were prepared, respectively. 13 centrifuge tubes were taken, and 20 mL of the aqueous Au (III) solution was added to the centrifuge tubes, respectively. And pHs of the aqueous Au (III) solutions in the centrifuge tubes were respectively adjusted, so that the pHs of the aqueous Au (III) solutions were sequentially 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 and 13. 6 additional centrifuge tubes were taken, and 20 mL of the aqueous Pd (II) solution was added to the centrifuge tubes, respectively. And pHs of the aqueous Pd (II) solutions in the centrifuge tubes were adjusted 13 respectively, so that the pHs of the aqueous Pd (II) solutions were sequentially 1, 2, 3, 4, 5 and 6.

[0086] 3 mg of the adsorbent prepared in example 2 was added to each of the aforementioned centrifuge tubes, and then the centrifuge tubes were placed in a thermostatic 25°C water bath shaker instrument and shaken for 48 h. After adsorption was completed, a metal ion solution at the upper layer was taken, and subjected to dilution in a corresponding dilution rate. An atomic absorption spectrophotometer (AA-6680) was used to measure a concentration after the dilution, and corresponding adsorption rate and adsorption capacity were calculated. As the pH decreases, adsorption effect becomes better and better for both Au (III) ions and Pd (II) ions.

[0087] Use example 9

[0088] 950 mg / L of an aqueous Au (III) solution and 200 mg / L of an aqueous Pd (II) solution were prepared, respectively. 13 centrifuge tubes were taken, and 20 mL of the aqueous Au (III) solution was added to the centrifuge tubes, respectively. And pHs of the aqueous Au (III) solutions in the centrifuge tubes were respectively adjusted, so that the pHs of the aqueous Au (III) solutions were sequentially 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 and 13. 6 additional centrifuge tubes were taken, and 20 mL of the aqueous Pd (II) solution was added to the centrifuge tubes, respectively. And pHs of the aqueous Pd (II) solutions in the centrifuge tubes were adjusted respectively, so that the pHs of the aqueous Pd (II) solutions were sequentially 1, 2, 3, 4, 5 and 6.

[0089] 3 mg of the adsorbent prepared in example 3 was added to each of the aforementioned centrifuge tubes, and then the centrifuge tubes were placed in a thermostatic 25°C water bath shaker instrument and shaken for 48 h. After adsorption was completed, a metal ion solution at the upper layer was taken, and subjected to dilution in a corresponding dilution rate. An atomic absorption spectrophotometer (AA-6680) was used to measure a concentration after the dilution, and corresponding adsorption rate and adsorption capacity were calculated. As the pH decreases, adsorption effect becomes better and better for both Au (III) ions and Pd (II) ions.

[0090] Use example 10

[0091] 950 mg / L of an aqueous Au (III) solution and 200 mg / L of an aqueous Pd (II) solution were prepared, respectively. 13 centrifuge tubes were taken, and 20 mL of the aqueous Au (III) solution was added to the centrifuge tubes, respectively. And pHs of the aqueous Au (III) solutions in the centrifuge tubes were respectively adjusted, so that the pHs of the aqueous Au (III) solutions were sequentially 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 and 13. 6 additional centrifuge tubes were taken, and 20 mL of the aqueous Pd (II) solution was added to the centrifuge tubes, respectively. And pHs of the aqueous Pd (II) solutions in the centrifuge tubes were adjusted respectively, so that the pHs of the aqueous Pd (II) solutions were sequentially 1, 2, 3, 4, 5 and 6.

[0092] 3 mg of the adsorbent prepared in example 4 was added to each of the aforementioned centrifuge tubes, and then the centrifuge tubes were placed in a thermostatic 25°C water bath shaker instrument and shaken for 48 h. After adsorption was completed, a metal ion solution at the upper layer was taken, and subjected to dilution in a corresponding dilution rate. An atomic absorption spectrophotometer (AA-6680) was used to measure a concentration after the dilution, and corresponding adsorption rate and adsorption capacity were calculated. As the pH decreases, adsorption effect becomes better and better for both Au (III) ions and Pd (II) ions.

[0093] Use example 11

[0094] 950 mg / L of an aqueous Au (III) solution and 200 mg / L of an aqueous Pd (II) solution were prepared, respectively. 13 centrifuge tubes were taken, and 20 mL of the aqueous Au (III) solution was added to the centrifuge tubes, respectively. And pHs of the aqueous Au (III) solutions in the centrifuge tubes were respectively adjusted, so that the pHs of the aqueous Au (III) solutions were sequentially 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 and 13. 6 additional centrifuge tubes were taken, and 20 mL of the aqueous Pd (II) solution was added to the centrifuge tubes, respectively. And pHs of the aqueous Pd (II) solutions in the centrifuge tubes were adjusted respectively, so that the pHs of the aqueous Pd (II) solutions were sequentially 1, 2, 3, 4, 5 and 6.

[0095] 3 mg of the adsorbent prepared in example 5 was added to each of the aforementioned centrifuge tubes, and then the centrifuge tubes were placed in a thermostatic 25°C water bath shaker instrument and shaken for 48 h. After adsorption was completed, a metal ion solution at the upper layer was taken, and subjected to dilution in a corresponding dilution rate. An atomic absorption spectrophotometer (AA-6680) was used to measure a concentration after the dilution, and corresponding adsorption rate and adsorption capacity were calculated. As the pH decreases, adsorption effect becomes better and better for both Au (III) ions and Pd (II) ions.

[0096] Use example 12

[0097] 7 centrifuge tubes were respectively added with 20 mL of an aqueous Au (III) solution with a concentration of 1020 mg / L, and added with hydrochloric acid thereto to adjust a pH to 1. 3 mg of the adsorbent prepared in example 1 was added to each of the aforementioned centrifuge tubes, and then the centrifuge tubes were placed in a thermostatic water bath shaker instrument respectively with constant temperatures of 5°C, 15°C, 20°C, 25°C, 30°C, 35°C and 45°C, and shaken for 72 h. An additional group was used to perform an experiment under the same conditions. After adsorption was completed, a metal ion solution at the upper layer was taken and subjected to dilution. An atomic absorption spectrophotometer (AA-6680) was used to measure a concentration after the dilution, and corresponding adsorption rate and adsorption capacity were calculated, and results are as shown in Table 4.

[0098] Table 4 Results of the effect of temperature on the adsorption rate and the adsorption capacity

[0099] Temper ature / ° C Sample Total before adsorption / PPm Total after adsorptio n / ppm Adsorpti on rate Average adsorptio n rate Adsorption capacity Average adsorption capacity (mg / g) 5°C 1 1020.7 735.048 27.99% 27.84% 1904.35 1894.21 2 1020.7 738.088 27.69% 1884.08 15°C 1 1020.7 675.048 33.86% 32.95% 2304.35 2241.92 2 1020.7 693.776 32.03% 2179.49 20°C 1 1030.14 533.272 48.23% 49.90% 3312.45 3426.83 2 1030.14 498.96 51.56% 3541.20 25°C 1 1020.7 377.28 63.04% 60.39% 4289.47 4109.08 2 1020.7 431.395 57.74% 3928.70 30°C 1 1030.14 317.02 69.23% 71.10% 4754.13 4882.93 2 1030.14 278.38 72.98% 5011.73 35°C 1 1030.14 214.69 79.16% 79.46% 5436.32 5457.22 2 1030.14 208.42 79.77% 5478.12 45°C 1 1020.7 88.242 91.35% 90.49% 6216.39 6157.31 2 1020.7 105.964 89.62% 6098.24

[00100] As can be seen from the results in Table 4, as an adsorption temperature increases, the adsorption rate and the adsorption capacity gradually increase, and the adsorbent has better adsorption rate and adsorption capacity for gold ions at 45°C.

[00101] As can be seen from the aforementioned experiment results, through a method for preparing a sulfur-rich PEI-based adsorbent in the present disclosure, the sulfur-rich PEI-based adsorbent could adsorb gold ions and palladium ions onto a surface and channels of the sulfur-rich PEI-based adsorbent through mechanisms such as electrostatic attraction, chelation-coordination, and oxidation-reduction, and has good selectivity for the gold ions and the palladium ions.

[00102] The above descriptions are merely preferred embodiments of the present disclosure. It should be noted that a person of ordinary skill in the art may further make several improvements and modifications without departing from the principle of the present disclosure, but such improvements and modifications should also be deemed as falling within the scope of the present disclosure.

Claims

S CLAIMED IS:

1. A method for preparing a polyethyleneimine (PEI)-based adsorbent, comprising the steps of:mixing PEI, an episulfide and an organic solvent to obtain a mixture, and subjecting the mixture to ring-opening reaction to obtain the PEI-based adsorbent,wherein the organic solvent comprises one selected from the group consisting of ethanol and N,N-dimethylformamide.

2. The method for preparing the PEI-based adsorbent of claim 1, wherein the PEI has a number-average molecular weight of 600-70,000.

3. The method for preparing the PEI-based adsorbent of claim 1, wherein the episulfide comprises at least one selected from the group consisting of ethylene sulfide, 2-(chloromethyl) ethylene sulfide, propylene sulfide, isobutylene sulfide and trimethylene sulfide.IDCM4. The method for preparing the PEI-based adsorbent of claim 1, wherein a ratio of an amount1—of substance of the PEI to an amount of substance of the episulfide is in a range of 5 : 1 to 1 : 5.1—5. The method for preparing the PEI-based adsorbent of claim 1, wherein the ring-opening reaction is conducted at 10°C for 6 h.