TWI749613B - Method of treating waste liquid with heavy metals - Google Patents

Abstract

A method of treating waste liquid with heavy metals includes a collecting step for collecting waste concentrated liquid containing crystallized grains of heavy metals, a sludge layer forming step, a filtering step, and a sludge removing step. The sludge layer forming step is executed by introducing the waste concentrated liquid into a dehydrator in order to attach impurities of the waste concentrated liquid to a filtering layer and then form a sludge layer because of the attachment. In the filtering step, the waste concentrated liquid ready to be filtered is inputted into the dehydrator and outputted by pressurizing, thereby allowing the waste concentrated liquid to be filtered by the sludge layer and obtaining filtered water by the filtering process. In the sludge removing step, the sludge layer is removed from the dehydrator to obtain sludge. Accordingly, the method obtains the effect of recycling the filtered water and the sludge efficiently, prevents the blockage caused by the use of traditional membranes, and produces sludge having high purity for facilitating the economic value.

Description

Treatment method of waste liquid containing heavy metals

The invention relates to a waste liquid treatment method, in particular to a heavy metal-containing waste liquid treatment method.

In recent years, due to the rising awareness of environmental protection, water resources must be effectively used. For this reason, the reuse of industrial waste water has become very important. For example, Lapping Wastewater is waste water produced by thinning and grinding in the semiconductor packaging process. , One of the bulk water used in the packaging process, good water quality (conductivity>10　μs/cm, TOC>3ppm has good water recovery conditions, but because of the high concentration of silicon particles (800~1300 mg/L TS, turbidity> 9000NTU) and the particle size is mostly distributed in the hundreds of nanometers (100~1000nm), which is not easy to handle, but has economic value; the chemical coagulation method is commonly used in the industry for precipitation mixing, adsorption bridging, etc., after solid-liquid separation Release or recycling, but because the addition of chemicals will affect the ion concentration in the water and increase the conductivity (>100 μs/cm), in addition to affecting the quality of the recycled water, this method will also produce a large amount of iron and aluminum-containing silicon sludge. There are many impurities and no economic benefits; or another treatment with ultra-filter UF, which has high operating costs, may also cause problems such as filter blockage and high-concentration backwashing water, which must be improved.

Therefore, the object of the present invention is to provide a treatment method for waste liquid containing heavy metals, which can effectively and smoothly filter and recover the waste concentrated liquid and achieve high economic benefits.

Therefore, the heavy metal-containing waste liquid treatment method of the present invention includes a concentrated liquid collection step, a sludge layer establishment step, a filtration step, and a sludge discharge step; wherein, the concentrated liquid collection step collects heavy metal-containing crystal particles After the waste concentrate, the waste concentrate is used to input into a dewatering machine, the impurities of the waste concentrate adhere to the filter layer to form a sludge layer, and then the dehydration step is used to input the waste concentrate to be filtered into In the dewatering machine, the waste concentrated liquid is filtered through the sludge layer to form filtered water, and in the final step of sludge discharging, after the pressure in the dewatering machine reaches a preset value, the sludge layer is discharged and collected to form a The sludge, in this way, is filtered through the sludge layer established on the filter layer through the impurities of the waste concentrate itself, in addition to achieving a better filtering effect, increasing the water recovery rate, and reducing the electricity consumption and energy consumption of the conventional membrane recovery In addition, at the same time, the sludge obtained after filtration also has a higher purity, which can also increase the added value of the sludge.

The foregoing and other technical content, features, and effects of the present invention will be clearly understood in the following detailed description of the preferred embodiment with reference to the drawings.

Referring to Figure 1, the method for processing heavy metal-containing waste liquid of the present invention includes a concentrated liquid collection step, a sludge layer establishment step, a filtration step, and a sludge discharge step; wherein the concentrated liquid collection step is prepared with heavy metal-containing crystalline particles In the following experimental example of the present invention, the waste concentrate is the product produced after polishing with ultrapure water in the polishing and thinning process of wafers before packaging. In addition, the concentrate collection step It also includes a membrane filtration layer. The waste concentrate is filtered through the membrane filtration layer and intercepted by the membrane filtration layer. The membrane filtration layer can be one of hollow fiber filaments, flat membranes, and tubular membranes. The waste concentrate intercepted by the membrane filtration layer first passes through at least one raw water tank for collection for subsequent treatment, and the membrane filtration layer forms clear water (containing metal particles with a particle size of less than 0.03μm), which can be further processed For example, 1μm filter and RO system are reused (this part is not the technical feature of the present invention, so the clean water treatment will not be described in detail), and in this embodiment, the waste concentrate is filtered by the filter membrane, and its characteristics are mainly Conductivity>10 μs/cm, TOC>3 ppm, pH=6.5~7.5, but high concentration is extremely high, turbidity>9000 NTU, total solids concentration is about 800~1300 mg/L, particle size is 400~600 nm It is the main distribution, with good stability and evenly distributed in the aqueous solution.

Furthermore, when the waste concentrate to be processed is based on the different types of heavy metals contained in it, if the pH value is not between 7 and 11, the pH value of the waste concentrate needs to be adjusted to adjust the pH value of the waste concentrate to Between 7 and 11, so that some heavy metals in the waste solution will form crystalline particles to facilitate subsequent filtration and ensure the quality of the filtered water.

Continuing the foregoing, the sludge layer establishment step is mainly equipped with a dewatering machine with a filter layer, and the dewatering machine can be a plate and frame dewatering machine, which can mainly use a pneumatic pump to transport the waste concentrated liquid. ~2kg/cm ² pumping pressure to pump the waste concentrate in the original water tank to the dehydrator so that the waste concentrate forms a sludge layer on the filter layer, and the sludge layer is established In the step, the turbidity of the waste concentrate should be greater than 30 NTU, the particle size of heavy metal crystal particles should be greater than 0.03 μm, and when the waste concentrate passes through the sludge layer, its turbidity should be less than 30 NTU, and the heavy metal crystal particles should be less than 0.03 μm. It can be confirmed that the sludge layer has been established.

In addition, in order to have a better filtering effect, it can be timely in the sludge layer establishment step, before the sludge layer is established, a filter-aid layer is laid on the filter layer, and the filter-aid layer has a thickness of 1~ 10mm, and the filter-aid layer is one of diatomaceous earth, perlite, cellulose, organic media (such as potato starch granules, lint, polymer fibers, scales, ash from rice burning, etc.), and this implementation Example In the following, the filter-aid layer is illustrated with diatomaceous earth as an example.

Continuing with the foregoing, the filtering step is to input the waste concentrate to be filtered into the dehydrator and output under pressure, so that the waste concentrate is filtered through the sludge layer, so that the impurities in the waste concentrate are filtered. After being intercepted in the sludge layer, a filtered water is formed through the sludge layer, and the pump pressure can be adjusted in a fine-tuning manner. For example, according to the internal pressure or flux of the dehydrator as a parameter, the difference in feed pressure should not be increased Too large, and the quality of the produced water is mainly based on turbidity, for example, the turbidity is less than 30NTU, or even 20NTU.

Finally, at the end of water production, the internal pressure of the dehydrator is close to the set pressure or flux, or after the pump pressure is set to a preset value, the preset value can be adjusted according to the size of the equipment and the actual filtration efficiency, such as this embodiment Set the pump pressure to 5kg/cm ² to enter the sludge discharging step. The input of the waste concentrate into the dewatering machine will be stopped, and the sludge layer will be discharged from the dewatering machine, and the dewatering machine For the plate and frame dewatering machine, the sludge can be unloaded after the second delay, so that the sludge layer can be discharged to form a sludge, and the composition of the sludge obtained is different according to the filtered waste concentrate, and this implementation For example, the following is the polishing and thinning process of wafers before packaging. Ultrapure water is used for grinding. Therefore, the waste concentrate mainly contains a large amount of silicon dioxide, so the sludge has a high The content of silicon dioxide.

In addition, after the actual test, the water quality filtration status is as follows: Water Quality Project Waste concentrate filtered water unit Removal rate Conductivity 3 3 μs/cm - Total organic carbon 1.1 0.3 mg/L 72% Total solids >800 >7 mg/L 99% Turbidity 9600 20 NTU 99% Chlorine salt 0.55 0.08 mg/L 85% Sulfate 1.79 0.21 mg/L 88% Silicon dioxide 125 twenty three mg/L 80% PH value 7.4 7.1 - -

With the filtering effect of the sludge layer, the impurities in the waste concentrate can be effectively filtered, and a good filtering effect can be achieved. Refer to Figure 2 and the particle size analysis result of the waste concentrate is 400-600nm The proportion is 52.2%, and the particle size is less than 500 nm or less, accounting for about 32.8%, which is a size that the filter aid cannot capture, and it is filtered by the sludge layer, and the proportion of particles greater than 500 nm is 67.2%. The sludge layer can be formed by intercepting the surface pores of the filter aid, and it has a good effect after verification.

In addition, in order to evaluate the suitability for reuse, the sludge generated after filtration must be understood in terms of its physical and chemical composition. It uses the three-component table discussed by the Environmental Inspection Institute standard method (NIEA R205.01C). After component analysis, the following table :

project Moisture Ash Combustible sludge 29.67% 65.82% 4.51%

It can be seen from the above table that the sludge discharged by the dehydrator according to the present invention contains a large amount of water and some organic substances, and the chemical composition uses X-ray fluorescence analysis (XRF) to identify the element composition. The results are as follows: Element oxide Oxide content (%) Al2O3 0.034 CaO 0.037 SiO2 82.46 MgO 0.084 K2O 0.127 Fe2O3 0.208 Na2O 0.061

As mentioned above, X-ray diffraction analysis (XRD) is used to analyze the types of crystal phases. As shown in Figure 3, it can be seen that the sludge is mainly composed of SiO ₂ , and the XRD results can be mutually verified; in addition, scanning Microscopic observations with electron microscope (SEM) were carried out to observe the sludge produced by the filtration of the present invention (Figure 4), the sludge produced by the traditional mixed filtration (Figure 5), columnar diatomaceous earth (Figure 6), and disc-shaped Diatomaceous earth (Figure 7), comparing the SEM image of the sludge produced by the traditional mixed filtration and the SEM image of the sludge produced by the filter of the present invention, it can be found that the traditional mixed sludge is fine powder, and the present invention The sludge produced by the filtration in addition to agglomerated particulate sludge (circled in Figure 4) contains both columnar and disc-shaped diatomaceous earth. The reason is that the pre-application technology uses the diatomaceous earth shown in Figure 6 and Figure 7 as a filter aid It is applied on the surface of the filter cloth, so it is discharged together with the mud after being unloaded. After analysis, the present invention is confirmed to be applicable to industrial-grade SiO2 or green building materials. The sludge that originally needed to be discarded and buried is converted into reuse technology. The raw materials or products are returned to the market for use.

Referring to Figure 8, through the treatment method of the present invention, the sludge layer is used as the filtering method, which can effectively remove turbidity and total solids. The initial high flux can be maintained at 300~600 LMH, and the stable water production period is about 100 ~200 LMH, at the end of water production >100 LMH or when the internal pressure of the dehydrator exceeds 5kg/cm ² , it can be operated to unload the sludge as appropriate. The conventional ultra-filter membrane (ultra-filter UF) flux is about 20~40 LMH less than The technology of the present invention, although the use of ultrafiltration membrane has the advantage of high membrane area to treat the same amount of water, high turbidity blocking is still a problem, and through the technology of the present invention, it can effectively recover and solve the problem of traditional membrane blocking. At the same time, it can also produce high-purity sludge with economic value.

To summarize the foregoing, the heavy metal-containing waste liquid treatment method of the present invention includes a concentrated liquid collection step, a sludge layer establishment step, a filtration step, and a sludge discharge step; wherein the sludge layer establishment step utilizes a filter to be filtered and internal Waste concentrate containing heavy metal crystalline particles, and the waste concentrate is used to input into a dehydrator, the waste concentrate is input into the dehydrator, and impurities in the waste concentrate adhere to the filter layer to form a sludge Therefore, in the processing method of the present invention, the waste concentrate is used to filter the sludge layer established on the filter layer with its own impurities, and the filter aid can be timely combined with the sludge layer to achieve better results In addition, it can effectively increase the recovery rate of filtered water and reduce the electricity and energy consumption of conventional membrane recovery. At the same time, the sludge obtained after filtration also has a higher purity, which effectively increases the added value of the sludge.

However, what has been described above is only to illustrate the preferred embodiments of the present invention, and should not be used to limit the scope of implementation of the present invention, that is, simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the description of the invention , Should still fall within the scope of the invention patent.

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Fig. 1 is a flow block diagram of the first embodiment of the present invention. Fig. 2 is a particle size analysis diagram of waste concentrate in the first embodiment of the present invention. Fig. 3 is a diagram showing the types of crystal phases of sludge in the first embodiment of the present invention. Fig. 4 is a microscopic image diagram of sludge in the first embodiment of the present invention. Figure 5 is a microscopic image of the sludge produced by traditional mixed filtration. Figure 6 is a microscopic image of columnar diatomaceous earth. Figure 7 is a microscopic image of the disc-shaped diatomaceous earth. Figure 8 is a graph of flux, solids and operating pressure in comparison between the present invention and conventional technologies.

Claims (9)

A treatment method for waste liquid containing heavy metals, which comprises: A concentrated liquid collection step, which collects a waste concentrated liquid containing heavy metal crystal particles; A sludge layer establishment step, which inputs the above-mentioned waste concentrate into a dehydrator with a filter layer, causes the waste concentrate to be fed into the dehydrator, and is formed by the waste concentrate and impurities attached to the filter layer A sludge layer; In a filtration step, the waste concentrate to be filtered is input into the dehydrator and output under pressure, so that the waste concentrate is filtered through the sludge layer, so that the impurities in the waste concentrate are intercepted by the After the sludge layer, a filtered water is formed through the sludge layer; and A sludge discharge step, when the internal pressure of the dehydrator reaches a preset value, the input of the waste concentrate into the dehydrator will be stopped, and the sludge layer will be discharged and collected from the dehydrator to form a sludge . According to the method for processing heavy metal-containing waste liquid according to claim 1, wherein, in the sludge layer establishment step, a filter-aid layer is laid on the filter layer before the sludge layer is established, and the filter-aid layer The thickness is 1~10mm. According to the method for processing heavy metal-containing waste liquid in claim 1 or claim 2 of the scope of patent application, when the pH value of the waste concentrate in the concentrated liquid collection step is not between 7 and 11, the concentrated liquid collection step Before that, it must go through a pH adjustment step to adjust the pH to between 7 and 11 and form heavy metal particles. According to the method for processing heavy metal-containing waste liquid according to claim 1 or claim 2, wherein the concentrated liquid collection step further includes a membrane filtration layer, and the waste concentrated liquid is intercepted on the membrane filtration layer. According to the method for processing heavy metal-containing waste liquid according to claim 4 of the scope of patent application, the membrane filtration layer is one of hollow fiber filaments, flat membranes, and tubular membranes. According to the method for processing heavy metal-containing waste liquid according to claim 2 of the scope of patent application, the filter-aid layer is one of diatomaceous earth, perlite, cellulose, and organic medium. According to the method for processing heavy metal-containing waste liquid according to claim 6 of the scope of patent application, the organic medium is potato starch granules, cotton lint, polymer fibers, scales, and ash produced by burning rice. According to the method for processing heavy metal-containing waste liquid according to claim 1 of the scope of patent application, the turbidity of the waste concentrate in the sludge layer establishment step needs to be greater than 30 NTU, and the particle size of heavy metal crystal particles is greater than 0.03 μm. According to the claim 1 of the scope of patent application, the heavy metal-containing waste liquid treatment method, wherein, in the sludge layer establishment step, after the waste concentrate passes through the sludge layer, its turbidity is less than 30 NTU, and the heavy metal crystal particles are less than 0.03 μm, it can be confirmed that the sludge layer has been established.

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