KR20090025551A - A method for preparing iron oxide particles for improved performance of membrane separation, and advanced water treatment using the iron oxide particles obtained - Google Patents

Abstract

A method for manufacturing amorphous oxidized steel particle is provided to maximize salt removal efficiency by assembling a physical.chemical preprocessing technology and an electrodialysis membrane separation technique. A method for manufacturing amorphous oxidized steel particle comprises steps of: dissolving FeSO4.7H2O 80g in hyperpure water in which nitrogen is supplied; supplying continuously nitrogen in a glass reaction tub at anoxic condition, monitoring it using a thermometer and controlling reaction temperature to 90°C; dissolving 6.46g KNO3 and 44.9g KOH in the hyperpure water in which no oxygen of 240ml exists if temperature reaches 90°C, confirming reaction for 5 minutes and injecting the solution; heating it for 30-60 minutes if injection of solution is finished, cooling it, washing precipitate and obtaining oxidized steel particle which has magnetism.

Description

A method for preparing Iron Oxide Particles for Improved Performance of Membrane Separation, and Advanced Water Treatment using the Iron Oxide Particles obtained}

The present invention relates to a method for producing iron oxide particles for improving the performance of the separator and a high-efficiency water treatment system using the iron oxide particles obtained therefrom, and more particularly to produce iron oxide particles suitable for improving the performance of the separator, The combination of physical and chemical pretreatment techniques and electrodialysis membrane separation techniques not only maximizes salt removal efficiency but also minimizes the contamination of electrodialysis membranes by integrated filtration pretreatment.

Recently, a membrane process which can reliably separate the target material contained in the raw material, is easy to automate, and has a simple process has been applied to various industries. Here, the separator is a liquid or solid membrane which can separate the mixture by selectively passing a specific component, and the exchange rate of materials and energy is determined by the physicochemical properties of the membrane.

Currently developed membrane separation technologies include microfiltration, ultrafiltration, nanofiltration, reverse osmosis, gas separation and electrodialysis. Separation principles such as adsorption, dissolution and diffusion on the surface of the membrane are applied to separate materials.

This membrane separation technology has several characteristics compared to conventional separation and concentration processes. Membrane is characterized by a simple process by separating the material without phase change and superior energy efficiency compared to other separation process. Conventional methods induce phase changes and require high temperatures, so the properties of the separating material often change. However, the membrane separation is applied as a new alternative in the separation, purification and concentration of specific components because of the separation of the material by applying mechanical pressure, and the range of application is gradually increasing.

Depending on the material, form, and filtration method of the membrane, suspended solids, colloids, enzymes, proteins, organic solvents, salts, etc. can be separated, and specific components can be separated and concentrated in a mixed gas. In particular, when the wastewater is treated using a membrane separation process, the amount of chemicals used during the treatment process can be minimized, thereby minimizing sludge generation. The treated water obtained in the membrane process can be used as raw water or directly in the manufacturing process depending on the water quality. In addition, the capacity of the concentrated wastewater can be reduced to less than 10% of the total generated wastewater, so the membrane separation process is the core technology for the development of a zero discharge wastewater treatment system (Dhawan, Filter, Gaeta).

Such membranes can selectively separate wastewater with low energy, but contamination of membranes that degrade membrane performance slows the spread of membrane separation processes. Membrane contamination causes the suspended solids in the wastewater or the substances that are easily adsorbed on the surface of the membrane to accumulate on the membrane surface and pore size, impeding the flow of fluid, thereby reducing the permeability.

Extensive research is currently underway on membrane fouling. Much of the literature on membrane fouling and cleaning is mainly on RO membranes. Therefore, technology that overcomes the decrease in treatment efficiency and cost increase due to membrane contamination and secures the economic efficiency of membrane has become a hot topic in membrane technology. To meet such social demands, there is a demand for technology that reduces membrane contamination that can occur in membrane separation process. It's happening.

Accordingly, the present inventors confirmed that the iron oxide particles were manufactured by using a specific method to improve the performance of the separator, and then combined with the iron oxide adsorption method and the membrane separation method to reduce membrane contamination and further improve the wastewater treatment efficiency. The invention has been completed.

According to the first aspect of the present invention,

Provided is a method for producing amorphous iron oxide particles having a range of 1 to 100 μm by mixing FeCl ₃ in an ultrapure water of 18 MΩ or more at a weight ratio of 92: 100 (iron / ultra pure water) or less and completely neutralizing the pH to 7. .

According to the second aspect of the present invention,

FeSO ₄ is mixed in ultrapure water of 18 MΩ or more at a weight ratio of 90: 100 (iron / ultra pure water) and dissolved completely. Neutralize pH to 7 while purging nitrogen at 80 ~ 95 C anoxic condition, and then adjust the range of 1 ~ 100 μm. A method for producing amorphous iron oxide particles having is provided.

According to the third aspect of the present invention,

The method of producing amorphous iron oxide particles having magnetic size of 1 to 80 μm obtained by adjusting the pH to 8 while supplying nitrogen and dissolving sufficiently in an ultra pure water without oxygen at a weight ratio of Fe II / Fe III is 2 Is provided.

According to the fourth aspect of the present invention,

A pretreatment step of adsorbing organic matter using raw iron oxide particles obtained by the method of any one of the first to third aspects from raw water,

An electrodialysis membrane separation process for removing ionic substances consisting of MF, UF, NF, RO, and the like,

Recycling a part of the concentrated waste liquid generated in the electrodialysis membrane separation process and discarding the remainder;

Storing the final production water from which the ionic material is removed through the electrodialysis membrane separation process, and

Provided is a high-efficiency water treatment system combining iron oxide adsorption and membrane separation, which comprises adding a disinfectant to the final product and storing the final raw water for reuse.

According to the fifth aspect of the present invention,

After the pretreatment using the iron oxide particles prepared by the precipitation method by the system according to the fourth aspect, 90% of the ions are removed by electrodialysis, and the increment of the irreversible electric resistance obtained is 0.030 Ω / cm ^{2 in the} cation exchange membrane. The anion exchange membrane is provided with a high efficiency water treatment system combining iron oxide adsorption and membrane separation with 0.190 Ω / cm ² .

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

First, FeCl ₃ is mixed in ultrapure water of 18 MΩ or more at a weight ratio of 92: 100 (iron / ultra pure water) or less and completely dissolved, and then neutralized to pH 7 to produce amorphous iron oxide particles having a range of 1 to 100 μm. Is provided.

Specifically, 55.847 g of FeCl ₃ is completely dissolved in 20 l of ultrapure water of 18 MΩ or more, and then the pH is adjusted to 8 using 5N and 0.1N NaOH. Then, all iron oxides are precipitated, and the supernatant is washed away. ^- it can remove ions and obtain amorphous iron oxide particles.

In addition, FeSO ₄ is mixed in ultrapure water of 18 MΩ or more at a weight ratio of 90: 100 (iron / ultra pure water) and dissolved completely. After purging nitrogen at 80 ~ 95 C anoxic condition, neutralize the pH to 7 and then 1 ~ 100 μm Amorphous iron oxide particles having a range can be produced. Specifically, 80 g of FeSO ₄ · 7H ₂ O is dissolved in ultrapure water supplied with nitrogen, and then a glass reaction tank is blocked in which air circulation to the outside is continued. Nitrogen is continuously supplied under anoxic conditions and monitored by a thermometer, and the reaction temperature is 90 ° C. When the temperature reaches 90 ° C, dissolve 6.46 g KNO ₃ and 44.9 g KOH in 240 ml of oxygen-free ultrapure water and inject the solution for 5 minutes to check the reaction. An additional 60 minutes of heating, cooling overnight and washing the precipitate can yield magnetic iron oxide.

Furthermore, Fe Ⅱ / Fe Ⅲ by weight ratio of 2 is dissolved in ultra-pure water without oxygen and sufficiently dissolved to prepare a non-crystalline iron oxide particles having a magnetic size of 1 ~ 80 μm obtained by adjusting the pH to 8 while supplying nitrogen. do. Specifically, 270.30 g of FeCl ₃ 6H ₂ O and FeCl ₂ 198.81 g is dissolved in ultra pure water without oxygen, and then adjusted to pH 8 using 5N and 0.1N NaOH while supplying nitrogen, and the resulting iron oxide precipitates are collected and magnetic iron oxide can be obtained.

The iron oxide particles thus obtained can be applied to a high efficiency water treatment system combining iron oxide adsorption and membrane separation.

That is, the system includes a pretreatment step of adsorbing organic material using iron oxide particles obtained from raw water, an electrodialysis membrane separation step of removing ionic substances consisting of MF, UF, NF, RO, and the like, and the electrodialysis membrane separation step. Part of the concentrated waste liquor from the wastewater is recycled, the remainder is discarded, the process of storing the final product from which the ionic material has been removed through the electrodialysis membrane separation process, and the addition of a disinfectant solution to the final product can be reused. The process of storing the final raw water, including.

That is, referring to Figure 1, the raw water tank is a tank for storing the raw water may be attached to the acidic acid tank. The acid tank is a tank for storing an acid / base solution, and is attached to correspond to various raw water properties, and the acid / base solution in the tank is suitable for operating an acid / base of raw water introduced into an electrodialysis apparatus described later. It is a tank that serves to regulate.

The raw water from the raw water tank is subjected to an iron oxide adsorption tank. At this time, an ion exchange membrane contaminant is removed by using an internal iron oxide adsorption reaction.

As the iron oxide that can be used, amorphous iron oxide particles or magnetic iron oxide particles can be used. The method of manufacturing these is as above-mentioned.

As such, the raw water from which the ion exchange membrane contaminants are removed through the iron oxide adsorption tank is passed through the ED module as an electrodialysis module. The ED module is an electrodialysis apparatus in which cation exchange membranes and anion exchange membranes are alternately mounted, and serves to remove ionic substances contained in raw water pretreated with iron oxide. Of course, a power supply device is attached to the electrodialysis module.

The form of the module may generally use a plate and frame type most commonly used, but is not limited thereto. A spiral module may also be used.

If the ion exchange membrane in the electrodialysis module is contaminated to increase the membrane resistance, the membrane is cleaned using the ion exchange membrane cleaning liquid (eg, NaOH, HCl, etc.), where the ion exchange membrane cleaning liquid is stored in the membrane cleaning tank. .

 The product water passed through this electrodialysis module is sent to the final production water reservoir, and in the disinfectant storage tank, the addition of the disinfectant solution, for example, NaOCl, becomes the final raw water for reuse and discharged through the outlet.

On the other hand, some of the concentrated waste from the electrodialysis module is re-received through the recirculation furnace to the electrodialysis module, the remainder of the concentrated waste liquid is discarded through the waste liquid transport passage.

In addition, as an example of an electrodialysis apparatus, W * H * D = 110 * 190 * 25 cm, a membrane size of 75 * 150 cm, an effective membrane area of 61.875 cm ² , six ion exchange membranes, and a spacer size of 71 * 152 * 1 cm, 0-60V. A power supply capable of supplying power in the 0-2.2A range was used. PLC has 20 I / O terminals. The control speed is 250 ms / Step, the pump has 0-600 rpm, the flow rate is 100-1500 ml / min, the pressure gauge can measure up to 0-10 kPa, and the tubing has excellent heat resistance and low compression. Can be used.

In this case, the number of effective membrane regions and ion exchange membranes in the electrodialysis apparatus is highly variable since it depends on the size of the stack according to the purpose of the apparatus, but the effective membrane region is 61.875 cm ² and three pairs of ions A device in which the exchange membrane is alternately mounted can be used, in which a plate and frame module or a spiral module can be used.

In addition, the ion exchange membrane is composed of a cation exchange membrane and an anion exchange membrane. The cation exchange membrane is a strongly acidic cation-permeable type Na type, which has high mechanical strength, electrical resistance within the range of 1.8-3.8 Ω / cm ² , and burst strength of 0.40 KPa or more. It is possible to use a membrane having a thickness in the range of 0.14-0.20 mm, and the anion exchange membrane is a strong basic anion-permeable Cl type, which has high mechanical strength, electrical resistance in the range of 2.0-3.5 Ω / cm2, and burst strength of 0.30 KPa or more. Films with a thickness in the range of 0.12-0.18 mm can be used. In addition, a pre-manufactured membrane can also be purchased and used, such as a membrane manufactured by Tokuyama Corporation of Japan.

When washing such an ion exchange membrane, a solution prepared by adjusting the pH of NaOH, KOH, etc. to about 7-11 may be used, or a solution having a pH of 1-7, such as HCl, may be used.

In addition, during disinfection, chlorine-based disinfectants such as NaOCl may be injected or ozone or UV may be used to maintain a residual chlorine concentration of about 0.2 ppm depending on the characteristics of the discharged water.

According to the present invention, the results of the system treatment were identified through the following examples.

For reference, in the ratio increment the cation exchange membrane of regional electrical resistance when to remove about 90% without pretreatment of ion components contained in the raw water, and 0.041 Ω / cm ^2, the anion exchange membrane yieoteuna 0.041 Ω / cm ^2, produced by the precipitation method, After pretreatment with iron oxide particles, 90% of the ions were removed by electrodialysis, resulting in an irreversible electrical resistance increment of 0.030 Ω / cm ² for the cation exchange membrane and 0.190 Ω / cm ² for the anion exchange membrane. It was found that the improvement.

According to the present invention, it is possible to minimize the waste of water resources, solve the expected water shortage and dry river problems, and maximize the salt removal efficiency by combining physical and chemical pretreatment technology and electrodialysis membrane separation technology. It is possible to produce treated water that can be completely regenerated with industrial water, industrial water, maintenance water, etc., and it is possible to innovatively improve the economic feasibility of the system by minimizing the contamination of the electric soil separator by integrated filtration pretreatment. Secondary pollutants such as microbial sludge can be minimized, and the generation of chemical sludge can be minimized by using an easy-to-recovery integrated filtration process instead of pretreatment such as chemical flocculation and sedimentation. Energy efficient equipment compared to high pressure nano / reverse osmosis membrane filtration process The development and use of alcohol is expected.

Hereinafter, the present invention will be described in detail with reference to the following examples with reference to the drawings. The following examples are intended to illustrate the invention and are not intended to limit the invention thereto.

< Example >

Experiment apparatus

First, the experimental apparatus used in the present invention will be described in detail.

In general, the electrodialysis apparatus used in the present invention varies in performance due to variables such as current density, spacer configuration, type and concentration of electrolyte, flow rate, and pressure.

Therefore, the present inventors designed and manufactured a spacer having a form that minimizes dead space and is most easily turbulent, based on existing research literature in order to maximize dialysis efficiency, and prevents leakage between spacers. The frame was manufactured by commissioning a professional manufacturer of electrodialysis (Memtech, Korea) (see FIGS. 1 and 2).

The electrodialysis apparatus was manufactured to be configured by alternately arranging a cation exchange membrane and an anion exchange membrane, and the inventors carried out the following dialysis experiments by mounting each of three sets of ion exchange membranes.

The power supply used in the dialysis apparatus was a program power supply (E3645A, Agilent, USA) and a PLC was used to supply pulsating current (Master K120S, LSIS, Korea). In addition, the transfer of the solution used a chemical reaction-safe tube (platinum coated silicon tube, MasterFlex, USA), metering pump (variable metering pump, MasterFlex, USA) and flow meter (acrylic flow meter, Cole-parmer, USA), pressure gauge (ZSE40F, SMC, Japan) secured the reliability of the flow rate.

Details of the electrodialysis machine are shown in Table 1 below.

type details Frame size 110 * 190 * 25 (W * H * D) Conc. Drainage and regeneration Membrane size 75 * 150 Effective membrane area 61.875 cm ² Spacer 7 Spacer size 71 * 152 * 1 Power supply E3645A 0-60V, 0-2.2A PLC K120S 20 I / O, 0.1㎲ / Step Pump 0-600 rpm Flow meter 100-1500 ml / min Pressure gauge 0-10 KPa Tubing Excellent heat resistance, low compression

In this case, the ion exchange membrane is not limited thereto, but Tokuyama Co., Ltd. was used during the experiment, and there are various types of ion exchange membranes, but in this study, ion exchange membranes having strong physical properties (AMX, CMX) in accordance with commercialization, which is the priority of the research, were used. ) Was used.

The characteristics of the ion exchange membrane used in the present invention are shown in Table 2 below.

List Cation exchange membrane Anion exchange membrane type Strongly acidic cation can penetrate Strong basic anion can penetrate Characteristic High mechanical strength (Na-shape) High mechanical strength (Cl-shaped) Electrical resistance 1.8-3.8 2.0-3.5 Burst strength ≥0.40 ≥0.30 thickness 0.14-0.20 0.12-0.18 apply Purification of demineralized organics of whey Demineralization of concentrated sucrose of minerals Demineralization of abrasive water Concentration of Purified Minerals of Demineralized Organics in Whey

Experimental material

Furthermore, look at the experimental material used in the present invention.

Raw water can be used for both sewage and sewage, but the sewage treatment plant secondary sedimentation effluent was directly sampled and used as raw water. This is because it contains bio-residual organic matter (ROM), which satisfies the research purpose of pretreatment of organic matter. In the case of final effluent, chlorine or other oxidants introduced at the end of chlorine disinfection or other disinfection treatment process greatly degrade the performance of the ion exchange membrane. There is a possibility that it will be used.

Iron oxide manufacturing

In the present invention, iron oxide was used as an adsorbent for the organic material, and amorphous iron oxide particles and magnetic iron oxide particles were selected as the kinds thereof.

First, the method for producing amorphous iron oxide particles for improving the performance of the separator in the present invention is as follows. That is, 55.847 g of FeCl ₃ (Express reagent, Dongyang Chemical, Korea) are completely dissolved in 20 L of ultrapure water of 18 MΩ or more, and then the pH is adjusted to 8 using 5N and 0.1N NaOH. After adjusting the pH to 8, all iron oxides were precipitated and the supernatant was discarded to remove the Cl ⁻ ions by continuously washing the iron oxides. In this experiment, the experiment was performed by washing at least 20 times.

In addition, the magnetic iron oxide particles are applied to evaluate the possibility of improving the separation ability between the water and the adsorbent of the amorphous iron oxide particles in the present invention can be divided into the following two methods for improving the performance of the membrane.

The first method is to prepare nitrogen in anoxic conditions by continuously supplying nitrogen in water at 90 ° C. The second is to add 1: 2 ratio of ferric iron and trivalent iron in anoxic conditions that continuously supply nitrogen to oxygen-free water. It is a method of preparing by precipitation.

The first method of the heat precipitation method has the advantage of easy sedimentation because the particle size is large, but has a disadvantage of narrow adsorption area, and the second room temperature sedimentation method has the disadvantage that precipitation is not easy due to the small particle size. Since the adsorption area is wider than iron oxide produced by the heating method, there is an advantage that the organic matter removal ability is excellent.

Next, a method of producing two kinds of magnetic iron oxide particles was described in detail.

<Heat treatment method>

1) Dissolve 80 g of FeSO ₄ · 7H ₂ O in ultrapure water supplied with nitrogen.

2) Create a glass reaction tank that is blocked from air circulation to the outside and supply nitrogen under anoxic conditions and monitor the temperature with a thermometer to adjust the reaction temperature to 90 ℃.

3) When the temperature reaches 90 ℃, dissolve 6.46 g KNO ₃ and 44.9 g KOH in 240 ml of oxygen-free ultrapure water and inject the solution over 5 minutes to confirm the reaction.

4) After injecting the solution, heat it further for about 30-60 minutes, cool it overnight, and wash the precipitate. After the reaction is complete, no blocking with air is necessary.

<Precipitation Method>

1) Add 270.30 g of FeCl ₃ · 6H2O and 198.81 g of FeCl ₂ to the oxygen-free ultrapure water and dissolve it sufficiently. After adjusting the pH to 8 using 5N, 0.1N NaOH while supplying nitrogen, the resulting iron oxide precipitate was used.

Experimental procedure

Specific experimental procedures of the present invention are as follows.

First, the characteristics of the effluent from the sewage treatment plant are analyzed, and then electrodialysis is performed to predict and evaluate the salt removal efficiency and the membrane pollutant.

Subsequently, to evaluate the contribution of pollutants to the ion exchange membrane obtained based on the raw water dialysis results, an appropriate pretreatment method is derived by identifying the substances with high contribution from the organic-inorganic pollutants. As a result, adsorption of pollutants using iron oxide was considered as a proper pretreatment method, and iron oxide species suitable for the purpose of this study were selected by comparing the efficiency of various iron oxide types.

The iron oxides used were three kinds, i.e., amorphous iron oxide particles and two magnetic iron oxide particles.The irreversible main source of ion exchange membrane was evaluated as organic matter (protein). Kind was selected.

The ion exchange membrane is a cation exchange membrane strongly acidic cation-permeable type, having a high mechanical strength Na shape, an electrical resistance in the range of 1.8-3.8, a burst strength of at least 0.40, and a thickness in the range of 0.14-0.20 mm; and As the anion exchange membrane, a strong basic anion permeable type, which has a Cl-type with high mechanical strength, an electric resistance in the range of 2.0-3.5, a burst strength of 0.30 or more, and a thickness in the range of 0.12-0.18 mm, is used to contaminate the membrane. Wastewater can be treated efficiently while reducing

As described above, the wastewater was treated by physical and chemical pretreatment and electrodialysis using an ion exchange membrane, wherein the physical and chemical pretreatment was treated using iron oxide.

Analysis method

The analysis method is as follows.

1) Electrical Characteristic Analysis

Electrical characterization is largely represented by voltage and current measurements, and the measurement of each parameter was measured using a digital multimeter (M3850D, Metex, Korea). In addition, the measurement of the limit current density was calculated by the result of plotting using Excel's dynamic data exchange system by programming to increase the voltage by 0.01V per 10 seconds using a program power supply (E3645A, Agilent, USA).

2) Ion Exchange Membrane Characterization

In the characterization of the ion exchange membrane, the electrical resistance was measured. The electrical resistance was measured by immersing the clean ion exchange membrane in 0.1 N NaCl solution for 6 hours or more, measuring the electrolyte resistance (Rs) of the electrodialysis module filled with 0.1 N NaCl solution, and installing the pre-treated ion exchange membrane on the dialysis module. The resistance was measured (Rt) using a multimeter. Purity The resistance of the ion exchange membrane is the difference in electrolyte resistance in the total resistance after mounting the ion exchange membrane. The formula for the pure electrical resistance of the ion exchange membrane is as follows.

Ion exchange membrane resistance formula: Rm = Rt - Rs

3) Physical and chemical characterization of raw water

Physical and chemical characterization of raw water was carried out in various forms.

First, the hydrogen ion concentration was measured using a pH meter (pH340i, WIW, Germany), and all data were calibrated at 25 ° C. When the second decimal point of the indicated value was stabilized for more than 10 seconds.

Electrical conductivity was measured using a conductivity meter (Cond340i, WTW, Germany), and UV ₂₅₄ was measured at 254 nm wavelength in a quartz cell using a spectrophotometer (DR-4000, Hach, USA).

Total organic carbon analysis was analyzed using a total organic carbon analyzer (Sievers 820, GE, USA), and turbidity was measured using a turbidimeter (2100P, Hach, USA). The alkalinity was measured by titration method, and the unit was converted to CaCO ₃ form after analysis by manual titration according to the Standard Method.

4) Iron oxide particle size analysis

Particle size analysis was performed to characterize the prepared iron oxide, and a particle size analysis was performed using a laser particle size analyzer (LS 13320, Beckman Coulter, USA). Ultra pure water was used as the mobile phase, and the analysis module was statistically analyzed three times using a ULM (Universal Liquid Module).

5) mineral analysis

In the case of cations, inductively coupled plasma luminescence spectroscopy was conducted. All samples were prepared according to standard method ICP pretreatment method. USA). Anions were analyzed by ion chromatography, and ion chromatography (DX 5000, Dionex, USA) was analyzed at a rate of 1.2 ml / min using carbonate buffer as a mobile phase.

6) Organic matter analysis

For the analysis of organics, complex polysaccharides and proteins were analyzed. For each protein, Folin-Ciocalteau's phenol reagent was developed by Frolund, 1996. The procedure is as follows.Add 0.5 ml of Lowery Regent Solution (sigma, USA) to 0.1 ml of Folin-Ciocalteau's phenol reagent (Sigma, USA), react for 45 minutes at room temperature, and absorbance at 750 nm using a spectrophotometer. Measured. The complex polysaccharide was measured by the Phenol method invented in Debois, 1956. The procedure is as follows. First, 2 ml of sample is added to the tube and 0.05 ml of 80 wt% phenol is added. Then, 5 ml of concentrated sulfuric acid (Express, Dongyang Chemical, Korea) is quickly injected, reacted at room temperature for 10 minutes, and further reacted in a constant temperature bath at 25-30 C, and then absorbance is measured at 490 nm using a spectrophotometer.

7) Ion exchange membrane pretreatment

Contaminant desorption of the ion exchange membrane was carried out in the following manner. Each dialysis ion exchange membrane was soaked in 0.1 N NaOH solution and strongly ultrasonically cleaned for 1 hour to desorb organic matter, and the ion exchange membrane desorbed from sodium hydroxide solution was again soaked in 0.1 N HCl for 1 hour strongly ultrasonic cleaning to desorb inorganic matter. It was. The sample thus obtained was placed in a volumetric flask, adjusted to 100 ml, and analyzed.

Reference) Data QC / QA Scheme

For the QC / QA of the data, all experiments were conducted according to the Standard Method. In the case of instrument analysis, the reliability of the data was secured by measuring or calibrating the standard solution before analysis. In addition, all the analyzes used data averaged three times or more to reduce the error.

Experimental Example

end. By iron oxide particle adsorption pretreatment Membrane fouling Reduction

Materials to be treated by pretreatment were analyzed through analysis of the cause of membrane fouling, evaluation of pollution contribution by materials, and electrical resistance change experiments. A total of three types of iron oxides were evaluated. Two types of amorphous iron oxide particles and magnetic iron oxide particles were used in the experiment, and evaluation of removal efficiency of organic matters was the most important issue. Therefore, TOC removal performance was considered first, and iron oxide particles through particle size analysis Was also evaluated. The results are summarized in Table 3 below.

Iron oxide type TOC removal by time (unit mg / L) type Minutes Difference (mg / L) efficiency(%) 0 10 30 60 120 Amorphous iron oxide particles 3.07 1.58 1.48 1.43 1.38 1.69 55.05 Magnetic Iron Oxide Particles (Sediments) 3.07 1.15 1.3 1.08 1.03 2.04 66.45 Magnetic Iron Oxide Particles (Heating) 3.07 2.98 2.63 2.52 1.55 1.52 49.51

As shown in the above table, the organic matter removal ability was shown in the order of magnetic iron oxide particles (precipitation method)> amorphous iron oxide particles> magnetic iron oxide particles (heat treatment method), and in the case of magnetic iron oxide particle heat treatment method, Other contaminant removal trends were shown.

In the case of other iron oxides, the initial adsorption rate was so fast that most of the adsorption reactions were found to be completed within 20 minutes, while in the case of magnetic iron oxide particles prepared by heat treatment, the concentration of organic matter was decreased through continuous adsorption. (See Figure 3).

In addition, the TOC removal rate of the magnetic iron oxide particles produced by the precipitation method was evaluated to be the highest. Therefore, the optimal iron oxide species in the integrated filtration using iron oxide was determined as the magnetic iron oxide particle species produced by the precipitation method.

On the other hand, as a result of evaluating the ability to remove organic matter using amorphous iron oxide particles, the TOC reference removal amount was found to be 0.845 mg based on 120 minutes. This is the second highest TOC removal rate among the three iron oxides.

In this study, two magnetic iron oxide particles were selected as adsorbents. The reason why magnetic iron oxide particles are selected as an adsorbent is that amorphous iron oxide particles have good organic material adsorption capacity but are difficult to separate. Therefore, the applicability of various iron oxide membranes was evaluated by applying magnetic iron oxide particles, which can be used for magnetic separation, as an adsorbent. All magnetic iron oxide particles have polarity and can be separated by magnetic force. However, since the characteristics of the adsorbent vary depending on the preparation method, experiments were performed using both methods.

Performance evaluation results of the magnetic iron oxide particles produced by the heat treatment method are as follows. The TOC removal rate was 0.76 mg based on 120 minutes, showing the lowest adsorption rate among the prepared iron oxides. As a result of particle size analysis, the average particle size was 19.53 μm and the median particle size was 6.808 μm. This confirmed that the average size / median ratio (particle size distribution ratio) of 2.869 was not produced in a uniform size (see Fig. 4).

The performance evaluation of the magetite prepared by the precipitation method showed the highest TOC removal rate among the three iron oxides, and about 1.02 mg of TOC was removed for 120 minutes. As a result of particle size analysis, the average value was 14.29㎛ and the median value was 12.31μm. This was confirmed that the distribution ratio of 1.161 to prepare a fairly uniform particle shape.

I. Optimization of the electrodialysis process

Based on the previous studies, dialysis experiments were carried out with a laboratory-scale electrodialysis apparatus (described above) designed as an optimal process in the form of a mixture of microfiltration, integrated filtration, and electrodialysis.

In order to remove the colloidal material, the raw water pretreated with the microfiltration membrane was subjected to secondary treatment on the magnetic iron oxide particles iron oxide produced by the precipitation method. After dialysis at the proper current density to obtain the following results.

였으나, 혼성공정은

으로써 약20%의 염제거 속도향상을 이루었다(도 5). 초기 120분간의 염 제거 속도는 기존 공정과 혼성 공정 모두

으로 큰 차이가 없었으나, 추가로 기존 공정의 경우 막오염의 증가에 기인한 전류밀도 감소로 인해 염 제거 속도가 감소한 것으로 판단된다. When comparing the hybrid electrodialysis process with the existing dialysis process, the overall process of salt removal is

The hybrid process

As a result, about 20% of the salt removal rate was improved (FIG. 5). Salt removal rate of the initial 120 minutes is better for both conventional and hybrid processes

However, there was no significant difference, but in the case of the existing process, the salt removal rate was reduced due to the decrease in current density due to the increase of membrane contamination.

Table 4 shows the results of comparing pH, total dissolved solids content, total organic carbon content, UV ₂₅₄ and turbidity.

Comparison of Treated Water Quality in Conventional Electrodialysis and Hybrid Processes type enemy ED sole ED + 1OP pH 7.55 7.06 7.28 TDS (㎲ / cm ² ) 789 197.5 102.4 TOC (mg / L) 3.65 3.37 1.01 UV254 0.076 0.068 0.056 Turbidity (NTU) 1.18 0.186 0.162

As a result. In the case of total organic carbon, the removal performance was improved by about 842% compared to the existing electrodialysis process, and in the case of UV254, the performance was remarkably improved by 138%.

On the other hand, the reversible change in the electrical resistance of the ion exchange membrane is summarized in Table 5.

Comparison of Reversible Electrical Resistance and Efficiency of Hybrid Process with Existing Dialysis Process Resistance (Ω / cm ² ) ED sole IOP + ED efficiency(%) Virgin Fouled Virgin Fouled CXM 2.7 3.1 2.91 3.38 -17.5 0.4 0.47 AXM 4.7 5.3 3.71 4.02 51.7 0.6 0.31

As shown in the table above, in the case of cation exchange membranes, the integration process showed a resistance increase of about 0.07Ω / cm ² 17.5% compared to the existing process, but when looking at the contamination tendency of the anion exchange membrane, the membrane resistance was 0.29Ω / cm ^The decrease by ² was about 48.3% improvement compared to the existing process. This may be interpreted as the main cause of membrane resistance was removed through integrated filtration.

Furthermore, the change of the irreversible electrical resistance of the ion exchange membrane is summarized in Table 6.

Comparison of Irreversible Electrical Resistance and Efficiency of Hybrid Process with Existing Dialysis Process Resistance (Ω / cm ² ) ED sole IOP + ED efficiency(%) Virgin Fouled Virgin Fouled CXM 2.7 2.74 2.91 2.94 25 0.04 0.03 AXM 4.7 5.15 3.71 3.90 57.8 0.45 0.19

As a result, the cation exchange membrane showed a decrease in resistance of about 0.01 Ω / cm ² 25% compared to the conventional process, and the anion exchange membrane showed a decrease in resistance of about 0.26 Ω / cm ² 42.2%.

This implies that irreversible contamination means permanent damage to the membrane, so that chemical cleaning is impossible, and the economic burden of replacing the membrane with a new one is very large, and thus the reduction of the non-reciprocal electrical resistance of the anion exchange membrane is a remarkable research achievement.

According to the present invention, the technical aspects 1) minimize the waste of water resources, solve the expected water shortage and dry river problems, reduce the pollution load of the water quality ecosystem, ecological destruction and budget waste due to dam construction, etc. It can be used as a base technology for advanced treatment, regeneration and reuse of wastewater, which can be minimized.2) In particular, when electrodialysis is applied to industrial wastewater reuse of dyeing complexes, the water quality and stable water quality 3) The combination of physical and chemical pretreatment technology and electrodialysis membrane separation technology will maximize salt removal efficiency, making it possible to completely recycle the treated water into agricultural water, industrial water, and maintenance water. Innovative system economics by minimizing the contamination of electrocivil membranes with integrated filtration pretreatment 4) It is possible to minimize secondary pollutant problems such as microbial sludge which is issued in advanced biological treatment of sewage water, and it is possible to minimize the problem of chemical sludge by using an easy regeneration integrated filtration process instead of pretreatment such as chemical flocculation and sedimentation. 5) It is expected to develop and utilize technology that is more energy efficient than high pressure nano / reverse osmosis membrane filtration process applied for desalination.

In addition, in terms of economic and industrial aspects, 1) the development of advanced treatment and recycling technologies for wastewater generated after the use of domestic water, which accounts for about one quarter of the total water use, is not only related to the growth of water recycling environment industry, but also related industries. It can contribute to the construction and market creation of environmental facilities of each industry.2) At present, as a key technology for reuse of desalination technology as well as advanced treatment technology of sewage water for organic and nutrient removal, The greatest demand is expected within the year, and the technology developed in this study is expected to be a competitive technology in this field, and 3) the improvement of the image of local governments and companies by promoting the reorganization into an environment-friendly industrial structure. And develop international competitiveness, and contribute to the development of new technologies and advanced industrial facilities related to the recycling and reuse of sewage water. 4) By promoting the development of electrodialysis membranes and the development of efficient pretreatment systems, domestic technologies and industries in related fields can be activated to induce the localization of key technologies, and import substitution and export promotion can be expected. Due to the energy efficiency of the new membrane separation process, the operating cost can be expected to be less than 1/5 of the high pressure reverse osmosis process.

1 is a schematic diagram of a laboratory scale electrodialysis apparatus used as an embodiment of the present invention;

2 is a view showing a state in which the electrodialysis apparatus shown in FIG.

3 is a graph showing the rate of change of the TOC over time according to an embodiment of the present invention,

Figure 4 is a graph showing the particle size analysis results of the iron oxide particles according to an embodiment of the present invention,

5 is a graph comparing the total removal rate of salts when performing the hybrid electrodialysis process and the conventional electrodialysis process according to the present invention, and FIG. 6 is a schematic view of a water treatment process according to the present invention.

Claims (13)

FeCl ₃ is mixed in ultrapure water of 18 MΩ or more in a weight ratio of 92: 100 (iron / ultra pure water) or less to completely dissolve, and then neutralizes the pH to 7 to produce amorphous iron oxide particles having a range of 1 to 100 μm. Completely dissolving 55.847 g of FeCl _{3 in} 20 L of ultrapure water of 18 MΩ or more, and then adjusting the pH to 8 using 5N and 0.1N NaOH; And Continuously washing the iron oxide in the form of precipitating all of the iron oxide and discarding the supernatant, thereby removing Cl ⁻ ions and obtaining amorphous iron oxide particles; Method for producing amorphous iron oxide particles, characterized in that consisting of FeSO ₄ is mixed in ultrapure water of 18 MΩ or more in a weight ratio of 90: 100 (iron / ultra pure water) or less to completely dissolve and neutralizes the pH to 7 to produce magnetic iron oxide particles having magnetic range having a range of 1 to 100 μm. Way. Dissolving 80 g of FeSO ₄ 7H ₂ O in ultrapure water supplied with nitrogen; Making a glass reaction tank in which air circulation to the outside is blocked, and continuously supplying nitrogen under anoxic conditions and adjusting the reaction temperature to 90 ° C. while monitoring with a thermometer; Dissolving 6.46 g KNO ₃ , 44.9 g KOH in 240 ml of oxygen free ultra pure water when the temperature reached 90 ° C. and injecting the solution while checking the reaction for about 5 minutes; And At the end of injection of the solution, further heated for 30-60 minutes, cooled overnight, and washing the precipitate to obtain magnetic iron oxide particles; Method for producing amorphous iron oxide particles comprising a A method for producing amorphous iron oxide particles having magnetic size of 1 ~ 80 μm obtained by adjusting the pH to 8 while supplying nitrogen and dissolved in ultra pure water without oxygen at a weight ratio of Fe II / Fe III to 2. 270.30 g of FeCl ₃ ㆍ 6H ₂ O and FeCl ₂ as Fe II and Fe III Dissolving 198.81 g in oxygen free ultrapure water to sufficiently dissolve; Then adjusting to pH 8 using 5 N, 0.1 N NaOH while supplying nitrogen, and Collecting the resulting iron oxide precipitates to obtain magnetic iron oxide particles; Method for producing amorphous iron oxide particles, characterized in that consisting of A pretreatment step of adsorbing organic matter from raw water using iron oxide particles obtained by the method of any one of claims 1 to 6, An electrodialysis membrane separation process for removing ionic substances consisting of MF, UF, NF, RO, and the like, Recycling a part of the concentrated waste liquid generated in the electrodialysis membrane separation process and discarding the remainder; Storing the final production water from which the ionic material is removed through the electrodialysis membrane separation process, and A high-efficiency water treatment system combining iron oxide adsorption and membrane separation comprising the step of adding a disinfectant to the final product and storing the final raw water for reuse. 8. The high efficiency water treatment system according to claim 7, wherein the electrodialysis apparatus has an effective membrane area of 61.875 cm ² and combines iron oxide adsorption and membrane separation in which three pairs of ion exchange membranes are alternately mounted. 8. The high efficiency water treatment system as claimed in claim 7, wherein the electrodialysis apparatus uses a plate and frame module or a spiral module. The ion exchange membrane of claim 7, wherein the ion exchange membrane comprises a cation exchange membrane and an anion exchange membrane. The cation exchange membrane is a strongly acidic cation-permeable type Na, which has high mechanical strength and electric resistance within a range of 1.8-3.8 Ω / cm 2 and a burst strength. Is 0.40 KPa or more and the thickness is within the range of 0.14-0.20 mm, and the anion exchange membrane is a strong basic anion-infiltrating Cl type with high mechanical strength and electrical resistance within the range of 2.0-3.5 Ω / cm2 and burst strength. A high-efficiency water treatment system combining iron oxide adsorption and membrane separation, characterized in that each membrane is 0.30 KPa or more and uses a thickness in the range of 0.12-0.18 mm. The method according to claim 7, wherein the ion exchange membrane is washed with a solution prepared by adjusting the pH of NaOH, KOH, etc. to about 7-11, or using a solution of adjusting the pH of 1-7, such as HCl. High efficiency water treatment system combining iron oxide adsorption and membrane separation. The method of claim 7, wherein the disinfectant is infused with iron oxide adsorption and membrane separation, in which disinfectants such as NaOCl are injected at a level capable of maintaining a residual chlorine concentration of about 0.2 ppm according to the discharge water properties. After the pretreatment using iron oxide particles prepared by the precipitation method by the system according to any one of claims 7 to 12, 90% of the ions are removed by electrodialysis and the increment of irreversible electrical resistance obtained is 0.030 in the cation exchange membrane. High efficiency water treatment system combining iron oxide adsorption method and membrane separation method which is Ω / cm ² and 0.190 Ω / cm ² in anion exchange membrane.

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