Preparation methods and applications of polyethylene glycol / hydroxyapatite

Abstract

This invention discloses a method for preparing polyvinyl alcohol / hydroxyapatite, firstly through the pretreatment of a copper sheet, and then through the electrochemical preparation of polyvinyl alcohol / hydroxyapatite (PEG / HAP). This invention also discloses an application of polyvinyl alcohol / hydroxyapatite. This invention solves the problems of uneven pore structure distribution and limited number of micropores in hydroxyapatite in existing technologies.

Description

Technical Field

[0001] This invention belongs to the field of composite material preparation technology, specifically relating to a method for preparing polyethylene glycol / hydroxyapatite, and also relating to an application of polyethylene glycol / hydroxyapatite. Background Technology

[0002] Polyethylene glycol (PEG) is a nonionic surfactant with the molecular formula HO(CH2CH2O). n Hydroxyapatite (HAP) possesses strong hydrophilicity due to its presence of only ether bonds and hydroxyl groups. It can form a hydrophilic protective film on the particle surface, increasing the range of hydration repulsion between particles and effectively preventing particle aggregation. Due to its hydrophilicity and non-toxicity, it is widely used in the surface modification of various biomaterials and adsorbents. A PEG / HAP composite material was synthesized by electrodeposition, enhancing the uniformity of pore structure distribution in hydroxyapatite, broadening the range of micropore numbers, and was applied to the removal of fluoride ions from wastewater. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing polyethylene glycol / hydroxyapatite, which solves the problems of uneven pore structure distribution and limited number of micropores in the prior art.

[0004] Another object of the present invention is to provide an application of polyethylene glycol / hydroxyapatite.

[0005] The first technical solution adopted in this invention is a method for preparing polyethylene glycol / hydroxyapatite, characterized by the following steps:

[0006] Step 1: Pre-treatment of copper sheets;

[0007] Step 2: Electrochemical preparation of polyethylene glycol / hydroxyapatite (PEG / HAP).

[0008] The first technical solution of the present invention is further characterized in that,

[0009] Step 1 is implemented in the following steps:

[0010] Remove the oxide film from the surface of the high-purity oxygen-free copper sheet, grind it until the surface is smooth and shiny, and then ultrasonically clean it in anhydrous ethanol and acetone for 3 minutes in sequence to remove impurities. After drying, it is ready for use.

[0011] Step 2 is implemented in the following steps:

[0012] In a traditional three-electrode working system, cyclic voltammetry was used. The pretreated, smooth copper sheet electrode (copper sheet), platinum electrode, and saturated calomel electrode were used as the working electrode, counter electrode, and reference electrode, respectively. Electrochemical deposition was performed on the surface of the copper sheet electrode at a scanning potential range of -0.8 to -1.45 V, a scanning rate of 0.2 V / s, and 300 scan cycles. The supporting electrolyte for the electrodeposition process was a mixed electrolyte solution with a pH of 6.0, a polyethylene glycol content of 1%, a Ca(NO3)2·4H2O concentration of 0.0025 mol / L, a NaNO3 concentration of 0.15 mol / L, and an NH4H2PO4 concentration of 0.025 mol / L. The calcium phosphate salt content in the electrolyte solution was kept in a supersaturated state, which was greater than the solubility product constant of HAP.

[0013] After the electrodeposition process is completed, the copper sheet is removed, washed several times with distilled water, and then air-dried to obtain polyethylene glycol / dicalcium phosphate dihydrate PEG / DCPD. It is then soaked in a 0.05-0.25 mol / L NaOH solution for 5-30 hours. After soaking, it is rinsed with distilled water until the pH of the copper sheet surface is neutral, and then air-dried to obtain polyethylene glycol / hydroxyapatite PEG / HAP. The surface coating is then scraped off for later use.

[0014] The second technical solution adopted in this invention is to apply polyethylene glycol / hydroxyapatite (PEG / HAP) to remove fluoride ions from wastewater.

[0015] The second technical solution of the present invention is further characterized in that,

[0016] Specifically as follows:

[0017] Analysis of factors affecting the defluorination efficiency of polyethylene glycol / hydroxyapatite:

[0018] (1) Effect of PEG / HAP dosage on polyethylene glycol / hydroxyapatite

[0019] Prepare equal amounts of F with concentrations of 2-10 mg / L. - The solutions were divided into six plastic centrifuge tubes and incubated in a constant temperature water bath at 15-55℃ for 2-6 h with different dosages of polyethylene glycol / hydroxyapatite (PEG / HAP): 0.1 g / L, 0.3 g / L, 0.5 g / L, 0.7 g / L, 0.9 g / L, and 1.0 g / L. The supernatant was then used to determine the Fibre concentration. - concentration;

[0020] (2) F - Effect of initial concentration

[0021] Pour equal amounts of F, but at different concentrations, into five plastic centrifuge tubes. - Solution, F- The solution concentrations were 2 mg / L, 4 mg / L, 6 mg / L, 8 mg / L, and 10 mg / L, respectively. The dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) was fixed at 0.1–1.0 g / L. The reaction was carried out in a constant temperature water bath at 15–55 °C for 2–6 h. After the reaction, the supernatant was taken to determine the F. - Concentration; i.e., F - Initial concentration determination;

[0022] (3) Effect of pH

[0023] Prepare equal amounts of 2 mg / L F - The solution was placed in plastic centrifuge tubes, and the pH of the solution was adjusted to 3, 4, 5, 6, 7, 8, 9, and 10 sequentially with HCl or NaOH. The dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) was fixed at 0.1-1.0 g / L. The solution was then shaken in a constant temperature water bath at 15-55℃ for 2-6 h. The supernatant was then used to determine the F... - concentration;

[0024] (4) The effect of temperature

[0025] Prepare different concentrations of F - The solution was placed in plastic centrifuge tubes, and the dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) was fixed at 0.1-1.0 g / L. The mixture was subjected to isothermal shaking at different temperatures, and the supernatant was then used to determine the F-value. - concentration;

[0026] (5) The effect of coexisting anions

[0027] Prepare equal volumes of 2 mg / LF containing different concentrations of anions. - The solution was placed in a plastic centrifuge tube, and the anions were Cl- and Cl-. - NO3 - SO4 2- CO3 2- The dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) was fixed at 0.1-1.0 g / L, and the reaction was carried out with shaking at 15-55℃ for 2-6 h. The supernatant was then used to determine the F content. - concentration.

[0028] (6) Regeneration of the adsorbent

[0029] Prepare 2 mg / LF - The solution was placed in plastic centrifuge tubes, with a fixed dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) of 0.1–1.0 g / L. The mixture was shaken and reacted at 15–55 °C for 2–6 h. After one adsorption experiment was completed, the supernatant was used to determine the Fo. -Concentration; then the PEG / HAP adsorbent was regenerated for 10-20 h under NaOH concentration of 0.1-0.3 mol / L, and after regeneration, 2-10 mg / L of fresh adsorbent was added. - The adsorption reaction was carried out in the solution, and the supernatant was taken to determine F after 2-6 hours of reaction. - Concentration; this process is recorded as one regeneration adsorption experiment.

[0030] The wastewater is as follows:

[0031] Contains Na + Concentration 25 mg / L, NO3 - Concentration 10 mg / L, SO4 2- Concentration 10 mg / L, CO3 2- Concentration 20 mg / L, Mg 2+ Concentration 40 mg / L, Ca 2+ Concentration 15 mg / L, K + Concentration 15 mg / L, Cl - 2 mg / LF at a concentration of 150 mg / L - The solution was placed in plastic centrifuge tubes to simulate actual fluoride-containing wastewater. The dosage of PEG / HAP was fixed at 0.5 g / L, and the mixture was shaken and reacted at 25 °C for 3 h. The supernatant was then used to determine the fluoride content. - concentration.

[0032] The beneficial effects of this invention are: polyethylene glycol improves the uniformity of the pore structure distribution of hydroxyapatite, increases the number of micropores, and increases the adsorption capacity of hydroxyapatite for fluoride ions. Attached Figure Description

[0033] Figure 1(a) shows the effect of the effective area of ​​the copper sheet on the amount of DCPD deposition in the preparation method of polyethylene glycol / hydroxyapatite of the present invention;

[0034] Figure 1(b) shows the effect of the effective area of ​​the copper sheet on the unit deposition amount of DCPD in the preparation method of polyethylene glycol / hydroxyapatite of the present invention;

[0035] Figure 2 This invention relates to the effect of the number of scan cycles on the amount of DCPD deposition in the preparation method of polyethylene glycol / hydroxyapatite.

[0036] Figure 3 This invention relates to the effect of scanning rate on DCPD deposition in the preparation method of polyethylene glycol / hydroxyapatite.

[0037] Figure 4 This invention relates to the effect of PEG content on defluorination efficiency in the preparation method of polyethylene glycol / hydroxyapatite.

[0038] Figure 5 The effect of PEG / HAP dosage in the preparation method of polyethylene glycol / hydroxyapatite in this invention;

[0039] Figure 6(a) shows the preparation method of polyethylene glycol / hydroxyapatite in this invention. - The effect of initial concentration on defluorination efficiency;

[0040] Figure 6(b) shows the preparation method of polyethylene glycol / hydroxyapatite in this invention. - The effect of initial concentration on adsorption capacity;

[0041] Figure 7 This invention relates to the effect of pH on the fluoride removal efficiency of PEG / HAP in the preparation method of polyethylene glycol / hydroxyapatite.

[0042] Figure 8 In the preparation method of polyethylene glycol / hydroxyapatite of this invention, temperature affects different initial concentrations of F. - The effect of solution adsorption;

[0043] Figure 9 The influence of coexisting anions in the preparation method of polyethylene glycol / hydroxyapatite of this invention;

[0044] Figure 10 This invention relates to the effect of NaOH concentration on the fluoride removal efficiency of PEG / HAP in the preparation method of polyethylene glycol / hydroxyapatite.

[0045] Figure 11 This invention relates to the effect of regeneration time on the fluoride removal efficiency of PEG / HAP in the preparation method of polyethylene glycol / hydroxyapatite.

[0046] Figure 12 The number of times PEG / HAP is used in the preparation method of polyethylene glycol / hydroxyapatite in this invention affects the effluent F - The effect of concentration;

[0047] Figure 13 This refers to the parallel adsorption efficiency of PEG / HAP on simulated actual fluoride-containing wastewater in the preparation method of polyethylene glycol / hydroxyapatite of this invention. Detailed Implementation

[0048] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0049] A method for preparing polyethylene glycol / hydroxyapatite, characterized by comprising the following steps:

[0050] Step 1: Pre-treatment of copper sheets;

[0051] Step 2: Electrochemical preparation of polyethylene glycol / hydroxyapatite (PEG / HAP).

[0052] Step 1 is implemented in the following steps:

[0053] High-purity oxygen-free copper sheets with dimensions of 1 cm × 5 cm × 0.2 mm were polished with 1000-grit sandpaper to remove the oxide film on the surface of the high-purity oxygen-free copper sheets. After polishing until the surface was smooth and shiny, they were ultrasonically cleaned in anhydrous ethanol and acetone for 3 minutes in sequence to remove impurities. After drying, they were ready for use.

[0054] Step 2 is implemented in the following steps:

[0055] In a traditional three-electrode working system, cyclic voltammetry was used. The pretreated, smooth copper sheet electrode (copper sheet), platinum electrode, and saturated calomel electrode were used as the working electrode, counter electrode, and reference electrode, respectively. Electrochemical deposition was performed on the surface of the copper sheet electrode at a scanning potential range of -0.8 to -1.45 V, a scanning rate of 0.2 V / s, and 300 scan cycles. The supporting electrolyte for the electrodeposition process was a mixed electrolyte solution with a pH of 6.0, a polyethylene glycol content of 1%, a Ca(NO3)2·4H2O concentration of 0.0025 mol / L, a NaNO3 concentration of 0.15 mol / L, and an NH4H2PO4 concentration of 0.025 mol / L. The calcium phosphate salt content in the electrolyte solution was kept in a supersaturated state, which was greater than the solubility product constant of HAP.

[0056] After the electrodeposition process is completed, the copper sheet is removed, washed several times with distilled water, and then air-dried to obtain polyethylene glycol / calcium bicarbonate dihydrate PEG / DCPD. It is then soaked in a 0.05-0.25 mol / L NaOH solution for 5-30 hours. After soaking, it is rinsed with distilled water until the pH of the copper sheet surface is neutral, and then air-dried to obtain polyethylene glycol / hydroxyapatite PEG / HAP. The surface coating is then scraped off for later use.

[0057] Applications of polyethylene glycol / hydroxyapatite: PEG / HAP is used to remove fluoride ions from wastewater.

[0058] Specifically as follows:

[0059] Analysis of factors affecting the defluorination efficiency of polyethylene glycol / hydroxyapatite:

[0060] (1) Effect of PEG / HAP dosage on polyethylene glycol / hydroxyapatite

[0061] Prepare equal amounts of F with concentrations of 2-10 mg / L. -The solutions were divided into six plastic centrifuge tubes and incubated in a constant temperature water bath at 15-55℃ for 2-6 h with different dosages of polyethylene glycol / hydroxyapatite (PEG / HAP): 0.1 g / L, 0.3 g / L, 0.5 g / L, 0.7 g / L, 0.9 g / L, and 1.0 g / L. The supernatant was then used to determine the Fibre concentration. - concentration;

[0062] (2) F - Effect of initial concentration

[0063] Pour equal amounts of F, but at different concentrations, into five plastic centrifuge tubes. - Solution, F - The solution concentrations were 2 mg / L, 4 mg / L, 6 mg / L, 8 mg / L, and 10 mg / L, respectively. The dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) was fixed at 0.1–1.0 g / L. The reaction was carried out in a constant temperature water bath at 15–55 °C for 2–6 h. After the reaction, the supernatant was taken to determine the F. - Concentration; i.e., F - Initial concentration determination;

[0064] (3) Effect of pH

[0065] Prepare equal amounts of 2 mg / L F - The solution was placed in plastic centrifuge tubes, and the pH of the solution was adjusted to 3, 4, 5, 6, 7, 8, 9, and 10 sequentially with HCl or NaOH. The dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) was fixed at 0.1-1.0 g / L. The solution was then shaken in a constant temperature water bath at 15-55℃ for 2-6 h. The supernatant was then used to determine the F... - concentration;

[0066] (4) The effect of temperature

[0067] Prepare different concentrations of F - The solution was placed in plastic centrifuge tubes, and the dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) was fixed at 0.1-1.0 g / L. The mixture was subjected to isothermal shaking at different temperatures, and the supernatant was then used to determine the F-value. - concentration;

[0068] (5) The effect of coexisting anions

[0069] Prepare equal volumes of 2 mg / LF containing different concentrations of anions. - The solution was placed in a plastic centrifuge tube, and the anions were Cl- and Cl-. - NO3 - SO4 2- CO3 2-The dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) was fixed at 0.1-1.0 g / L, and the reaction was carried out with shaking at 15-55℃ for 2-6 h. The supernatant was then used to determine the F content. - concentration.

[0070] (6) Regeneration of the adsorbent

[0071] Prepare 2 mg / LF - The solution was placed in plastic centrifuge tubes, with a fixed dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) of 0.1–1.0 g / L. The mixture was shaken and reacted at 15–55 °C for 2–6 h. After one adsorption experiment was completed, the supernatant was used to determine the Fo. - Concentration; then the PEG / HAP adsorbent was regenerated for 10-20 h under NaOH concentration of 0.1-0.3 mol / L, and after regeneration, 2-10 mg / L of fresh adsorbent was added. - The adsorption reaction was carried out in the solution, and the supernatant was taken to determine F after 2-6 hours of reaction. - Concentration; this process is recorded as one regeneration adsorption experiment.

[0072] The wastewater is as follows:

[0073] Contains Na + Concentration 25 mg / L, NO3 - Concentration 10 mg / L, SO4 2- Concentration 10 mg / L, CO3 2- Concentration 20 mg / L, Mg 2+ Concentration 40 mg / L, Ca 2+ Concentration 15 mg / L, K + Concentration 15 mg / L, Cl - 2 mg / LF at a concentration of 150 mg / L - The solution was placed in plastic centrifuge tubes to simulate actual fluoride-containing wastewater. The dosage of PEG / HAP was fixed at 0.5 g / L, and the mixture was shaken and reacted at 25 °C for 3 h. The supernatant was then used to determine the fluoride content. - concentration.

[0074] HAP regeneration experiment

[0075] Prepare a 2 mg / L F- solution, fix the HAP dosage at 0.5 g / L, and shake the reaction at 25 ℃ for 3 h. Then, take the supernatant to determine the F- concentration. After the adsorbed HAP is placed in 0.2 mol / L NaOH solution for 12 h, the next defluorination experiment can be carried out.

[0076] Results and Discussion

[0077] Optimization of electrodeposition conditions for HAP

[0078] Optimization of preparation condition parameters

[0079] The electrochemical deposition process for preparing PEG / HAP is influenced by various factors, including the substrate area, number of scan cycles, scan rate, and PEG content. This experiment employed cyclic voltammetry, using the deposition amount of DCPD on the substrate and the F content in the solution as parameters. - The removal rate was optimized as an indicator, and various parameters in the electrochemical deposition process for preparing PEG / HAP were optimized.

[0080] (1) Optimization of the optimal area of ​​the copper sheet

[0081] Under the same electrochemical deposition conditions, the amount of DCPD deposited on copper sheets with different immersed areas in the electrolyte also varies. Therefore, the effective area (1.3 cm²) of different copper sheets was investigated under the conditions of a mixed electrolyte containing 0.5% PEG, a scan potential range of -0.8 to -1.45 V, a scan rate of 0.2 V / s, and 300 scan cycles. 2 2.2 cm 2 3.8 cm 2 4.4 cm 2 5.7 cm 2 7.2 cm 2 9.6 cm 2 The effect of PEG doping on the amount of DCPD deposition.

[0082] Figures 1(a) and 1(b) are curves showing the influence of the effective area of ​​the copper sheet on the deposition amount and deposition amount per unit area of ​​DCPD, respectively. As shown in Figure 1(a), the DCPD deposition amount is [data missing] when the effective area of ​​the copper sheet is 5.7 cm². 2 The deposition rate reaches its maximum at this time. As shown in Figure 1(b), the deposition rate per unit area of ​​DCPD is 4.4 cm² on the effective copper sheet area. 2 Therefore, considering both the maximum utilization rate and cost of the copper sheet, the optimal effective area of ​​the copper sheet was determined to be 4.4 cm². 2 That is, the size of the copper sheet is 1 cm × 5 cm.

[0083] (2) Optimization of scanning circle count

[0084] The effects of different scan numbers (200, 250, 300, 350, 400, and 450 scans) on the deposition amount of DCPD after PEG doping were investigated under the conditions of a mixed electrolyte containing 0.5% PEG, a scan potential range of -0.8 to -1.45 V, and a scan rate of 0.2 V / s.

[0085] The results are as follows Figure 2As shown, when the number of scan cycles is too small, the amount of DCPD deposited on the copper sheet is relatively small. As the number of scan cycles increases, the amount of DCPD deposited on the copper sheet increases accordingly. However, after 300 scan cycles, further increasing the number of scan cycles causes the deposition amount to basically stabilize, and even slightly decrease with increasing scan cycles. This is because the effective area of ​​the copper sheet is limited. When the number of scan cycles is too large, the DCPD deposition layer becomes loose and easily falls off, causing too much DCPD to float in the electrolyte instead of continuing to deposit on the copper sheet surface, resulting in significant loss. Therefore, 300 scan cycles were chosen as the optimal number of scan cycles for preparing PEG / HAP.

[0086] (3) Optimization of scan rate

[0087] The scan rate also affects the deposition amount of DCPD on the copper sheet. Under the conditions of a mixed electrolyte containing 0.5% PEG, a scan potential range of -0.8 to -1.45 V, and 300 scan cycles, the effect of different scan rates (0.1 V / s, 0.2 V / s, 0.3 V / s, 0.4 V / s, 0.5 V / s) on the deposition amount of PEG-doped DCPD was investigated. The results are as follows: Figure 3 As shown, within the scan rate range of 0.1~0.5 V / s, the deposition amount of DCPD first increases and then decreases, reaching a maximum at a scan rate of 0.2 V / s. Therefore, 0.2 V / s is determined to be the optimal scan rate for the electrodeposition preparation process of PEG-modified HAP.

[0088] (4) Optimization of PEG content

[0089] The fluoride removal efficiency of the prepared PEG / HAP adsorbent varies depending on the PEG doping content. Under the optimal electrochemical deposition conditions of -0.8 to -1.45 V, 300 scan cycles, and a scan rate of 0.2 V / s, with F... - The removal rate was used as the optimization index, and the effect of different PEG contents (0.1%, 0.5%, 1.0%, 1.5%, 2.0%) on the performance of the prepared PEG / HAP was investigated. Figure 4 As shown, the defluorination efficiency of HAP first increases and then decreases with increasing PEG content. This may be because when the PEG content is low, it can further alleviate the agglomeration of particles during HAP deposition, thereby increasing its specific surface area and improving defluorination performance. However, excessively high PEG content will result in an overly thick protective film on the surface of HAP particles, which is detrimental to its defluorination performance. - The adsorption of PEG was observed. Therefore, the optimal doping content of PEG during the HAP modification process was determined to be 1%.

[0090] Adsorbent regeneration (PEG / HAP recyclability)

[0091] Regeneration conditions:

[0092] (1) Effect of NaOH concentration

[0093] Using NaOH solution as the regenerator for PEG / HAP, and with defluorination efficiency as the optimization index, the effects of different concentrations of NaOH solution (0.05 mol / L, 0.10 mol / L, 0.15 mol / L, 0.20 mol / L, 0.25 mol / L) on the defluorination performance of PEG / HAP after regeneration were investigated. Figure 10 The study demonstrated the effect of NaOH concentration on the defluorination efficiency of PEG / HAP. Within the NaOH concentration range of 0.05-0.20 mol / L, the regeneration adsorption efficiency of the adsorbent increased with increasing NaOH concentration, reaching a maximum of 66%. Further increases in NaOH concentration subsequently reduced the defluorination efficiency. Therefore, the optimal alkaline concentration for PEG / HAP regeneration was selected as 0.2 mol / L.

[0094] (2) The effect of regeneration time

[0095] The duration of alkaline regeneration affects the regeneration and adsorption efficiency of the adsorbent. Using 0.2 mol / L NaOH solution as the regeneration solution for PEG / HAP adsorbent, the effects of different regeneration soaking times (8 h, 12 h, 16 h, 20 h, and 24 h) on its defluorination performance were investigated. The results are as follows: Figure 11 As shown, the defluorination efficiency of PEG / HAP first increases and then decreases with the increase of alkaline regeneration time. The defluorination efficiency of the adsorbent is the highest when the regeneration time is 12 h. Therefore, the optimal regeneration time of PEG / HAP is determined to be 12 h.

[0096] Regeneration and repeatability

[0097] Figure 12 This is a regeneration-adsorption cycle diagram for the PEG / HAP adsorbent. Figure 12 It can be seen that after the first alkaline regeneration, PEG / HAP can still achieve a defluorination efficiency of 75%, and the effluent F - The concentration was 0.5 mg / L; with the increase of regeneration cycles, the fluoride removal efficiency of PEG / HAP decreased, and the effluent fluoride removal efficiency in the second, third, fourth, and fifth regeneration adsorption tests was [not specified]. - The concentrations were 0.64 mg / L, 0.73 mg / L, 0.86 mg / L, and 0.94 mg / L, respectively. This PEG / HAP adsorbent can be used continuously for 6 times while still producing high effluent quality. - The concentration is below 1 mg / L, which meets the national standards for the discharge of fluoride-containing wastewater.

[0098] Simulated actual wastewater experiment

[0099] Simulated fluoride-containing wastewater was treated with PEG / HAP, and the results are as follows: Figure 13 As shown, the treated fluoride-containing wastewater can all meet the national standard for fluoride content. - The concentration required for safe discharge is below 1 mg / L, and the deviation of the fluoride removal rate values ​​in the five parallel adsorption experiments is small, indicating that the actual fluoride removal performance of PEG / HAP synthesized by electrochemical method is reproducible.

[0100] Effects of PEG / HAP on F-containing - Factors affecting wastewater removal efficiency

[0101] Effect of PEG / HAP dosage on defluorination efficiency

[0102] In the initial F - The effects of different PEG / HAP dosages (0.1 g / L, 0.3 g / L, 0.5 g / L, 0.7 g / L, 0.9 g / L, 1.0 g / L) on defluorination efficiency at a concentration of 2 mg / L are as follows: Figure 5 As shown in the figure. From the figure, it can be seen that when the PEG / HAP dosage is 0.1 g / L, the F in the solution... - The removal rate was low, only 48%; while when the PEG / HAP dosage was 0.5 g / L, the F in the solution... - The removal rate reached 79%; when the dosage was increased to 1.0 g / L, the F in the solution... - The removal rate was the highest, approaching 100%. According to my country's national standards, the fluoride content in wastewater should be reduced to a minimum of [specific value missing]. - Since the concentration should not exceed 1 mg / L, the optimal dosage of PEG / HAP in the solution is 0.5 g / L when treating 2 mg / L fluoride-containing water.

[0103] F - Effect of initial concentration

[0104] Under the condition of PEG / HAP dosage of 0.5 g / L, the effects of different F were investigated. - The effect of initial concentrations (2 mg / L, 4 mg / L, 6 mg / L, 8 mg / L, 10 mg / L) on the fluoride removal efficiency and adsorption capacity of PEG / HAP was investigated. The results are shown in Figure 6(a). With increasing F... - With increasing initial concentration, the effect of PEG / HAP on F - The removal efficiency gradually decreases because when F in the solution... - At lower concentrations, the amount of adsorbent is relatively excessive, which can fully absorb F in the solution. - This results in high defluorination efficiency, while with F - As the concentration increases, the active adsorption sites on the adsorbent surface are completely occupied, naturally reducing the fluoride removal efficiency. However, its adsorption capacity is related to F...- The initial concentration showed a positive correlation, as shown in Figure 6(b), with the increase of F in the solution. - With increasing concentration, the amount of fluoride absorbed per unit mass of PEG / HAP increases, when F - After the initial concentration was increased to 6 mg / L, the increase in PEG / HAP adsorption slowed down, reaching a maximum of 6.2 mg / g.

[0105] Effect of pH on removal rate

[0106] The pH of the solution was adjusted with sodium hydroxide and HCl, and the effect of different pH values ​​(3, 4, 5, 6, 7, 8, 9, 10) on the fluoride removal efficiency of PEG / HAP was investigated. Figure 7 This is a graph showing the fluoride removal efficiency of PEG / HAP at different pH levels, such as... Figure 7 As shown, when the pH value increases from 3 to 6, the effect of PEG / HAP on F - The removal efficiency of fluoride also continued to increase, reaching its highest level of approximately 80% at pH 6. This may be because, in a strongly acidic environment, F... - In aqueous solution, it exists in the form of HF, which is detrimental to the adsorption of PEG / HAP adsorbents, resulting in low fluoride removal efficiency; while in strongly alkaline conditions, excessive OH- ions in the solution... - Will with F - This creates competition, thereby weakening F. - The increased likelihood of PEG / HAP adsorbents occupying more adsorption sites within the adsorbent enhances their effectiveness against F. - The removal capacity is reduced. Within a pH range of 3 to 10, the fluoride removal efficiency of PEG / HAP adsorbent can reach over 55%, thus the fluoride-containing wastewater can meet the discharge standards after treatment. This indicates that PEG / HAP adsorbent has a wide pH tolerance range and certain application value.

[0107] The effect of temperature

[0108] The effects of PEG / HAP on different initial concentrations of F at different temperatures (15 ℃, 25 ℃, 35 ℃, 45 ℃, 55 ℃) were investigated. - The adsorption effect of the solution is shown in the following results. Figure 8 As shown, increasing the temperature is beneficial for PEG / HAP to react with F in the solution. - The adsorption capacity of PEG / HAP increased with increasing temperature, with a maximum adsorption capacity of 9.56 mg / g.

[0109] Effects of coexisting anions

[0110] In actual fluoride-containing wastewater treatment processes, other types of anions coexist, therefore, at a concentration of 2 mg / L F... - In the solution, the presence of F was investigated. -Coexisting anions (Cl) at concentrations of 5, 10, 20, and 40 times - NO3 - SO4 2- CO3 2- The effect of ) on the defluorination performance of PEG / HAP. The test results are as follows. Figure 9 As shown, during the entire adsorption process, it is F - 40 times the concentration of coexisting anions Cl - NO3 - SO4 2- CO3 2- The presence of all of these factors has a certain promoting effect on the adsorption capacity of PEG / HAP; in the case of F - CO3 concentrations of 5, 10, and 20 times 2- In the solution system, the adsorption capacity of PEG / HAP decreased significantly, by up to approximately 17%, possibly due to the fact that higher valence anions are more readily adsorbed by PEG / HAP; Cl - The presence of [a substance] does not significantly affect the defluorination capacity, possibly because it is less effective than [another substance]. - The larger ionic radius makes it difficult for the ions to enter the internal structure of PEG / HAP. In summary, this indicates that PEG-modified HAP has a greater effect on Cl... - NO3 - and SO4 2- All of them have good anti-interference performance.

Claims

1. A method for preparing polyethylene glycol / hydroxyapatite, characterized in that, The specific steps are as follows: Step 1: Pre-treatment of copper sheets; Step 1 is implemented in the following steps: Remove the oxide film from the surface of the high-purity oxygen-free copper sheet, grind it until the surface is smooth and shiny, and then ultrasonically clean it in anhydrous ethanol and acetone for 3 minutes in sequence to remove impurities. After drying, it is ready for use. Step 2: Electrochemical preparation of polyethylene glycol / hydroxyapatite (PEG / HAP); Step 2 is implemented in the following steps: In a traditional three-electrode working system, cyclic voltammetry was used. The pretreated, smooth copper sheet electrode (copper sheet), platinum electrode, and saturated calomel electrode were used as the working electrode, counter electrode, and reference electrode, respectively. Electrochemical deposition was performed on the surface of the copper sheet electrode at a scanning potential range of -0.8 to -1.45 V, a scanning rate of 0.2 V / s, and 300 scan cycles. The supporting electrolyte for the electrodeposition process was a mixed electrolyte solution with a pH of 6.0, a polyethylene glycol content of 1%, a Ca(NO3)2·4H2O concentration of 0.0025 mol / L, a NaNO3 concentration of 0.15 mol / L, and an NH4H2PO4 concentration of 0.025 mol / L. The calcium phosphate salt content in the electrolyte solution was kept in a supersaturated state, which was greater than the solubility product constant of HAP. After the electrodeposition process is completed, the copper sheet is removed, washed several times with distilled water, and then air-dried to obtain polyethylene glycol / dicalcium phosphate dihydrate PEG / DCPD. It is then soaked in a 0.05-0.25 mol / L NaOH solution for 5-30 hours. After soaking, it is rinsed with distilled water until the pH of the copper sheet surface is neutral, and then air-dried to obtain polyethylene glycol / hydroxyapatite PEG / HAP. The surface coating is then scraped off for later use.

2. The application of the polyethylene glycol / hydroxyapatite PEG / HAP prepared by the method described in claim 1 for removing fluoride ions from wastewater; Specifically as follows: Analysis of factors affecting the defluorination efficiency of polyethylene glycol / hydroxyapatite: (1) Effect of PEG / HAP dosage on polyethylene glycol / hydroxyapatite Prepare equal amounts of F with concentrations of 2-10 mg / L. - The solutions were divided into six plastic centrifuge tubes and incubated in a constant temperature water bath at 15-55℃ for 2-6 h with different dosages of polyethylene glycol / hydroxyapatite (PEG / HAP): 0.1 g / L, 0.3 g / L, 0.5 g / L, 0.7 g / L, 0.9 g / L, and 1.0 g / L. The supernatant was then used to determine the F-value. - concentration; (2) F - Effect of initial concentration Pour equal amounts of F, but at different concentrations, into five plastic centrifuge tubes. - Solution, F - The solution concentrations were 2 mg / L, 4 mg / L, 6 mg / L, 8 mg / L, and 10 mg / L, respectively. The dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) was fixed at 0.1–1.0 g / L. The reaction was carried out in a constant temperature water bath at 15–55 °C for 2–6 h. After the reaction, the supernatant was taken to determine the F. - Concentration; i.e., F - Initial concentration determination; (3) Effect of pH Prepare equal amounts of 2 mg / L F - The solution was placed in plastic centrifuge tubes, and the pH of the solution was adjusted to 3, 4, 5, 6, 7, 8, 9, and 10 sequentially with HCl or NaOH. The dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) was fixed at 0.1-1.0 g / L. The solution was then shaken in a constant temperature water bath at 15-55℃ for 2-6 h. The supernatant was then used to determine the F... - concentration; (4) The effect of temperature Prepare different concentrations of F - The solution was placed in plastic centrifuge tubes, and the dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) was fixed at 0.1-1.0 g / L. The mixture was subjected to isothermal shaking at different temperatures, and the supernatant was then used to determine the F-value. - concentration; (5) The effect of coexisting anions Prepare equal volumes of 2 mg / LF containing different concentrations of anions. - The solution was placed in a plastic centrifuge tube, and the anions were Cl- and Cl-. - NO3 - SO4 2- CO3 2- The dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) was fixed at 0.1-1.0 g / L, and the reaction was carried out with shaking at 15-55℃ for 2-6 h. The supernatant was then used to determine the F content. - concentration; (6) Regeneration of the adsorbent Prepare 2 mg / LF - The solution was placed in plastic centrifuge tubes, with a fixed dosage of polyethylene glycol / hydroxyapatite (PEG / HAP) of 0.1–1.0 g / L. The mixture was shaken and reacted at 15–55 °C for 2–6 h. After one adsorption experiment was completed, the supernatant was used to determine the Fo. - Concentration; then the PEG / HAP adsorbent was regenerated for 10-20 h under NaOH concentration of 0.1-0.3 mol / L, and after regeneration, 2-10 mg / L of fresh adsorbent was added. - The adsorption reaction was carried out in the solution, and the supernatant was taken to determine F after 2-6 hours of reaction. - Concentration; this process is recorded as one regeneration adsorption experiment; The wastewater specifically includes the following: Contains Na + Concentration 25 mg / L, NO3 - Concentration 10 mg / L, SO4 2- Concentration 10 mg / L, CO3 2- Concentration 20 mg / L, Mg 2+ Concentration 40 mg / L, Ca 2+ Concentration 15 mg / L, K + Concentration 15 mg / L, Cl - 2 mg / LF at a concentration of 150 mg / L - The solution was placed in plastic centrifuge tubes to simulate actual fluoride-containing wastewater. The dosage of PEG / HAP was fixed at 0.5 g / L, and the mixture was shaken and reacted at 25 °C for 3 h. The supernatant was then used to determine the fluoride content. - concentration.

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