KR102526373B1 - Process for Treating Wastewater of Nickel Plating - Google Patents

Abstract

In the present invention, an activated carbon mixture derived from a plurality of sources is used as an adsorbent that can effectively firstly remove nickel and other heavy metals in nickel plating wastewater, and a plurality of membrane processes are subsequently performed to chemical chemicals such as precipitants. A method for treating nickel plating wastewater capable of discharging a purified treatment liquid while minimizing or suppressing the use of materials is described.

Description

Nickel plating wastewater treatment method {Process for Treating Wastewater of Nickel Plating}

The present invention relates to a method for treating nickel plating wastewater. More specifically, the present invention uses an activated carbon mixture derived from a plurality of sources as an adsorbent that can effectively firstly remove nickel and other heavy metals in nickel plating wastewater, and subsequently performs a plurality of membrane processes. A method for treating nickel plating wastewater capable of discharging a purified treatment liquid while minimizing or suppressing the use of chemicals such as precipitating agents.

Plating is generally a process of forming a metal plating layer on a substrate, and a nickel plating process can be exemplified as the most commercially applied metal plating. The nickel plating process is widely applied to semiconductor circuit plating, printed circuit board (PCB) plating, plating of various parts such as pistons, brakes, bearings, and valves of vehicles, and plastic plating.

In the nickel plating process, a cleaning step to remove impurities is performed for the purpose of improving plating quality and efficiency, and various acid components, basic components, cyanide compounds, and the like are used in the process. As a result, nickel plating wastewater contains various heavy metals, especially nickel, and exhibits strong acidity. Moreover, various heavy metal components contained in nickel plating wastewater are widely known as various health hazards, such as not only accumulating in the human body even at low concentrations, but also causing deformities in the fetus.

Therefore, a process of appropriately treating and discharging wastewater discharged from the plating process, particularly the most widely applied nickel plating process, is required. At this time, in the case of nickel in wastewater, the permitted emission concentration has been strengthened to 3 mg/L.

As a method of treating wastewater discharged from the nickel plating process, a precipitation method is typically applied. As an example, Korean Patent No. 1214187 discloses a method in which sodium chloride or sodium nitrate is added to nickel plating wastewater, mixed with ethanol to precipitate components other than nickel, and then caustic soda is added to recover nickel as nickel hydroxide. are starting

In the case of the above-described precipitation method, a metal ion is converted into an insoluble hydroxide in a state where the pH is increased by typically introducing a basic component, thereby coagulating and precipitating the metal ion. In particular, since it does not require separate equipment and facilities other than a precipitating agent, it is economical and easy to operate compared to other treatment methods.

However, there is a limit to effective removal of heavy metals because it may be difficult to form complex ions depending on the metals contained in the wastewater to form hydroxide-type precipitates. In particular, since all metal hydroxides are not completely precipitated at a single pH, it is practically difficult to increase the treatment efficiency of nickel plating wastewater in which a plurality of metals are mixed. Moreover, since the addition of a large amount of chemicals accompanies a required chemical reaction, secondary contamination may be caused, and reaction conditions must be strictly set, requiring specialized knowledge.

In addition to the precipitation method, an ion exchange method, a membrane method, and the like are known in the art, but when the concentration of suspended matter in the nickel plating wastewater is high, the ion exchange resin column is clogged and the operational efficiency is reduced. In addition, in the case of the membrane method, fouling is induced in the membrane due to colloidal substances in wastewater, so frequent membrane replacement or cleaning is required, making stable operation difficult. As such, direct application of nickel plating wastewater to ion exchange or membrane processes is not suitable for commercialization.

On the other hand, with the recent increase in environmental awareness, research is being conducted to utilize natural materials or wastes as much as possible rather than using chemicals in the treatment process of plating wastewater. However, when using natural materials alone, emission requirements that meet environmental standards difficult to meet

In the present invention, it is intended to provide a method for treating nickel plating wastewater containing a large amount of heavy metals to meet environmental standards and further purifying the wastewater to a level that can be used as a drinking water source.

In addition, in the present invention, in order to alleviate problems such as secondary pollution caused by the use of existing chemicals, the use of chemicals is minimized while the use of low-cost natural materials or waste is used to improve nickel plating wastewater We would like to provide a treatment plan.

Furthermore, the present invention intends to provide a method for treating nickel plating wastewater with improved treatment efficiency by utilizing an apparatus capable of effectively removing heavy metals in nickel plating wastewater.

According to one embodiment of the present invention.

a) contains at least 50 mg/L nickel, at least 30 mg/L chromium, at least 20 mg/L zinc, at least 10 mg/L copper, and at least 50 mg/L iron, and has a pH of 5 or less; and providing an aqueous nickel plating wastewater having a total dissolved solids concentration of at least 40 mg/L;

b) providing an aqueous dispersion of an activated carbon mixture combining oak-derived activated carbon and bamboo-derived activated carbon;

c) contacting the water-based nickel plating wastewater with an aqueous dispersion of the activated carbon mixture to adsorb and remove a part of metal components in the nickel plating wastewater by the activated carbon mixture to form a first treatment liquid having a reduced metal content, which is (i) ) separating into a first treatment liquid having a high activated carbon mixture content and (ii) a first treatment liquid having a low activated carbon mixture content;

d) After the first treatment liquid having a high activated carbon mixture content is allowed to stand, the supernatant thereof is transferred to a microfiltration step, while the first treatment liquid having a low activated carbon mixture content is transferred to a microfiltration step without being allowed to stand, thereby forming solids forming a multivalent metal ion-containing second treatment liquid having a reduced content; and

e) transferring the second treatment liquid to a nanofiltration step to form a third treatment liquid from which polyvalent metal ions are removed;

There is provided a method for treating nickel plating wastewater comprising a.

In an exemplary embodiment, prior to step c), the step of pre-treating the aqueous nickel plating wastewater using a filter filled with wood sawdust having a particle size of 2 mm or less in an amount of 15 to 50 g / L is further included. can

In an exemplary embodiment, the step c),

A first discharge pipe for discharging the first treatment liquid having a high activated carbon mixture content in the lower region, a second discharge pipe for discharging the first treatment liquid having a low activated carbon mixture content in the upper region, and a cylinder shape having a cover on the top. outer tank;

It extends from the cover while forming a concentric structure with the outer tank, and a lower end thereof is spaced apart from the bottom of the outer tank at a predetermined distance to provide a first fluid flow space, and has a cylindrical shape with an agitator connected to the cover. an inner tank of the inner tank, wherein the inner tank is configured to transfer contents to the outer tank side through the first fluid flow space;

A recycle pipe communicating with the inside of the inner tank and discharging some of the contents of the inner tank to the outside, a pump arranged to suction the contents of the inner tank through the recycle pipe and discharging them in a pressurized state, and a bottom of the outer tank. A recycling unit including a pressurized recycling pipe communicating with the inner tank through and transferring the contents pressurized by the pump to the inner tank, and a spray pipe for injecting the contents transferred to the end of the pressurized recycling pipe into the inner tank provided;

An activated carbon inlet pipe extending into the inner tank via the bottom of the outer tank to supply an aqueous dispersion of the new activated carbon mixture and connected to the injection pipe, wherein the recycled contents and the aqueous dispersion of the new activated carbon mixture are mixed. is sprayed into the inner tank through the injection pipe; and

an inverted funnel-shaped inclined plate disposed on the bottom surface of the outer tank and having an upper end spaced apart from the outer surface of the inner tank by a predetermined distance to provide a second fluid flow space;

It is performed using a processing device comprising a,

At this time, the treatment liquid that has passed through the second fluid flow space is separated under the action of gravity into (i) a first treatment liquid having a high activated carbon mixture content and (ii) a first treatment liquid having a low activated carbon mixture content, respectively in the first discharge pipe and It can be discharged through the second discharge pipe.

According to an exemplary embodiment, the injection pipe has an orifice area that expands after the width is tapered, and the activated carbon inlet pipe may be connected to the orifice area.

The nickel plating wastewater treatment process according to the present invention can effectively solve the problems of the prior art while suppressing the use of chemicals such as precipitants by sequentially performing an adsorption process using an activated carbon mixture derived from a plurality of natural materials and a membrane process. there is.

Furthermore, in the case of an exemplary embodiment of the present invention, the load of the subsequent membrane process can be effectively reduced by using a treatment device capable of maximizing adsorption by the activated carbon mixture in the adsorption process.

1 is a diagram schematically showing a treatment process of nickel plating wastewater according to the present invention; and
2 is a diagram showing the configuration of an adsorption treatment device applicable in an exemplary embodiment of the present invention.

The present invention can all be achieved by the following description. The following description should be understood as describing preferred embodiments of the present invention, but the present invention is not necessarily limited thereto. In addition, the accompanying drawings are for understanding, and the present invention is not limited thereto, and details of individual components can be properly understood by the specific purpose of the related description to be described later.

Terms used in this specification may be defined as follows.

"Adsorption" may refer to a separation process in which a certain component in a fluid is attached to the surface or inner surface of a solid adsorbent according to affinity, wherein the attachment may be implemented by a physical or chemical method. .

"Membrane" may mean a physical barrier capable of selectively separating a specific component from a mixture containing two or more components, and among the phases that permeate the membrane or are excluded by the membrane The concentration of a particular component is increased or decreased. Membrane-based filtration processes can be classified into reverse osmosis, nanofiltration, ultrafiltration, and microfiltration according to the pore size of the membrane surface.

"Microfiltration" may mean a filtration method using a membrane filter having a pore size in the range of about 0.1 to 10 μm to remove particulate impurities.

“Nanofiltration” may refer to a membrane technique that uses a membrane to separate different components in a fluid mixture. The pore size of the nanofiltration membrane may generally be set within the range of approximately 1 to 100 nm, and may involve a separation process based on molecular size and/or physicochemical interaction with fluid components in contact therewith. there is.

In the present specification, when a component is referred to as “including”, it means that other components may be further included unless otherwise specified.

Terms such as “above” or “upper” and “lower” or “below” may be understood to describe the relative positional relationship between components or elements, and may be understood as “located above” or “below”. The term "located" may be understood to express a relative positional relationship in a non-contact state as well as a state in contact with a specific object.

Provision of nickel-plated wastewater

A process for treating nickel plating wastewater according to the present invention is schematically shown in FIG. 1 .

Referring to Figure 1, first, aqueous nickel plating wastewater is provided. At this time, the composition and properties of the nickel plating wastewater may vary depending on the nickel plating process, but typically contain a plurality of metals, specifically, a plurality of metals other than nickel, specifically chromium, zinc, copper, iron, and the like. In the present invention, the content of nickel in the plating wastewater may be, for example, at least about 50 mg/L, specifically at least about 80 mg/L, and more specifically in the range of about 100 to 200 mg/L. The content of chromium may be, for example, in the range of at least about 30 mg/L, specifically at least about 50 mg/L, and more specifically in the range of about 80 to 150 mg/L. The zinc content may be, for example, at least about 20 mg/L, specifically at least about 40 mg/L, and more specifically in the range of about 50 to 120 mg/L. Meanwhile, the copper content may be, for example, at least about 10 mg/L, specifically at least about 20 mg/L, and more specifically in the range of about 30 to 90 mg/L. Additionally, the iron content may be, for example, in the range of at least about 50 mg/L, specifically at least about 60 mg/L, and more specifically in the range of about 70 to 110 mg/L.

In addition to the above-mentioned metal components, it can be understood that one or more heavy metals such as cadmium and arsenic may be contained depending on the source of plating wastewater or the plating process.

According to one embodiment, since the nickel plating wastewater exhibits acidity, the pH may be in the range of about 5 or less, specifically about 2 to 4.5, and more specifically about 3 to 4.

According to a specific embodiment, when a specific pH range is required in a later step such as an adsorption treatment or a membrane process described later, an acid (eg, hydrochloric acid) or a base (eg, NaOH, KOH, etc.) is added to adjust the pH. might be able to adjust. In particular, due to the addition of various chemicals and mixing of external inflows in the plating process, a significant amount of solids dissolved in aqueous media such as lumps, colloids, and solid substances present in a stabilized state are contained in the plating wastewater. Bar, the concentration of total dissolved solids in the wastewater may be, for example, at least about 40 mg/L, specifically at least about 70 mg/L, and more specifically at least about 80 mg/L. Depending on, it may exceed about 200 mg/L.

Provides an aqueous dispersion of activated carbon mixture

Referring to Figure 1, apart from providing nickel plating wastewater, an aqueous dispersion of activated carbon mixtures from different sources is provided.

In this regard, the activated carbon mixture can be prepared from readily available natural materials, and in the present invention, oak-derived activated carbon and bamboo-derived activated carbon are used in combination. The reason for combining activated carbon derived from two sources is that each pore property is different, so when used in combination, it is effective in adsorbing and removing various metal components or ions and other fine impurities contained in wastewater. because it wins

As an example, oak-derived activated carbon can be typically prepared from bark of oak nuts, oak wood, oak waste (eg, cuts left over from processing oak trees), and the like. At this time, in order to carbonize the oak in the form of activated carbon, a process of crushing it to an appropriate size may be performed first, a mechanical crushing device known in the art, such as a ball mill (specifically, a high energy ball mill), a pin mill , impact mill, edge runner mill, roller mill, hammer mill, etc. may be used, and in some cases, additional grinding may be performed using a jet mill or the like to obtain a finer pulverized product.

A carbonization treatment is performed on the pulverized oak tree formed in this way, and the carbonization or thermal decomposition reaction temperature may be, for example, in the range of about 400 to 800 °C, specifically about 450 to 750 °C, and more specifically about 500 to 700 °C. , and the carbonization time may range from about 5 hours or less, specifically about 4 hours or less, and more specifically about 0.5 to 2 hours. In addition, carbonization may be performed under an inert atmosphere, for example, an atmosphere of at least one gas selected from nitrogen, argon, neon, and the like.

On the other hand, in some cases, carbonization treatment may be performed after activation treatment with potassium hydroxide, phosphoric acid, etc. in order to increase the adsorption effect.

Meanwhile, in the case of bamboo-derived activated carbon, the bamboo skin or body may be pulverized using the above-described device and then carbonized or thermally decomposed to be converted into activated carbon. At this time, the carbonization temperature may be set in the range of, for example, about 300 to 600 °C, specifically about 350 to 500 °C, and more specifically about 400 to 450 °C, and the carbonization time is, for example, about 1 to 4 time, specifically from about 1.5 to 3 hours, more specifically from about 2 to 2.5 hours.

In the case of bamboo, a carbonization reaction may be performed after steam treatment or phosphoric acid treatment in order to increase the adsorption effect. In addition, the atmosphere during the carbonization reaction is as described above.

Exemplary properties of the oak-derived activated carbon and bamboo-derived activated carbon used in the present invention are shown in Table 1 below.

division Oak-Derived Activated Carbon Bamboo-derived activated carbon BET specific surface area (㎡/g) about 200 to 700, specifically about 250 to 600, more specifically about 300 to 500 about 800 to 2500 (specifically about 900 to 2200, more specifically about 1000 to 2000) Pore volume (cm3/g) about 0.1 to 0.,4, specifically about 0.15 to 0.35, more specifically about 0.2 to 0.3 about 0.5 to 1.5, specifically about 0.8 to 1.4, more specifically about 1 to 1.3 Pore diameter (nm) from about 2.5 to 5, specifically from about 3 to 4.5, more specifically from about 3.5 to 4 about 2 to 4, specifically about 2.2 to 3.5, more specifically about 2.5 to 3.4 Adsorbent size (㎛) about 50 to 300, specifically about 100 to 250, more specifically about 150 to 200 about 30 to 800, specifically about 50 to 400, more specifically about 70 to 200

As shown in the table above, oak-derived activated carbon and bamboo-derived activated carbon have distinct pore properties, and in particular, bamboo-derived activated carbon exhibits remarkably high porosity.

According to the present invention, when activated carbon derived from two natural sources is used in combination in consideration of the type and content of metal ions in the nickel plating wastewater and the properties of other impurities, various metal ions contained in the nickel plating wastewater are simultaneously removed. It is possible to provide a pore property capable of effectively adsorbing.

In this regard, the weight ratio of oak-derived activated carbon to bamboo-derived activated carbon in the activated carbon mixture is, for example, 1 : about 0.5 to 4, more specifically 1 : about 0.8 to 3, more specifically 1 : about 1 to 2 can be determined in the range of At this time, if the amount of oak-derived activated carbon is excessively large or small, it shows inefficient results in adsorbing some of the plurality of metals contained in the plating wastewater, so various metals can be adsorbed by adjusting within the above-mentioned range. It is desirable to have As such, oak and bamboo are easy to obtain, and it is advantageous in terms of economy when using wastes thereof.

In this embodiment, an activated carbon mixture containing two types of activated carbon is added to water to prepare an aqueous dispersion, which maximizes adsorption of metal components (or metal ions) through efficient contact with aqueous nickel plating wastewater. , Furthermore, it is to easily implement an efficient adsorption process using an adsorption treatment device described later.

According to an exemplary embodiment, the aqueous dispersion concentration of the activated carbon mixture is, for example, about 1 to 20% (w/w), specifically about 3 to 15% (w/w), more specifically about 5 to 10% (w / w), if the concentration of the aqueous dispersion is too low or high, it is undesirable from the point of view of economics or reduces the flow characteristics of the aqueous dispersion of the activated carbon mixture to the extent that it can cause inefficiency during adsorption. , it is advantageous to properly adjust within the above range.

adsorption process

Referring back to FIG. 1, a step of adsorbing and removing various metal ions and other anions (eg, chlorine anions, phosphate anions, etc.) in the nickel plating wastewater by combining nickel plating wastewater and an aqueous dispersion of an activated carbon mixture is performed. .

Optionally, when the content of suspended solids and solids in the nickel plating wastewater is excessively high, a pretreatment step may be performed to lower the load of the adsorption process. To this end, as a natural material, wood sawdust generated during wood processing may be used. Sawdust is not only easily obtainable, but also inexpensive. Although its adsorption capacity is rather low due to its less developed porosity than activated carbon, in the case of pre-treatment of nickel-plated wastewater using sawdust, it is a downstream process, especially an adsorption process using an activated carbon mixture. It can provide effects such as smooth operation and load reduction.

The shape of the waste wood sawdust applied in this embodiment is not particularly limited, but may be used after being pulverized into particles. In addition, the particle size of the sawdust particles may be, for example, about 2 mm or less, specifically about 1 mm or less, and more specifically about 0.5 mm or less. At this time, it can be applied in the form of filling sawdust in the pretreatment device, for example, about 15 to 50 g / L, specifically about 20 to 45 g / L, more specifically about 25 to 40 g / L It can be used by filling in quantity.

According to an exemplary embodiment, the amount of the aqueous dispersion of the activated carbon mixture in contact with the nickel plating wastewater during the adsorption step may be determined in consideration of the composition and properties of the nickel plating wastewater, the concentration of the activated carbon mixture in the aqueous dispersion, and the like. As an example, the weight ratio of the activated carbon mixture in the nickel plating wastewater:water dispersion is, for example, 1: about 0.01 to 0.5, specifically 1: about 0.05 to 0.3, more specifically 1: about 0.08 to 0.2. It may be, but is not necessarily limited thereto.

According to an exemplary embodiment, the adsorption step may be performed using an apparatus suitable for effectively contacting the aqueous dispersion of the nickel plating wastewater and the activated carbon mixture to maximize adsorption and efficiently operating the subsequent membrane process. The configuration of an adsorption treatment device applicable to an exemplary embodiment of the present invention is shown in FIG. 2 .

Referring to the drawings, the adsorption treatment device 100 largely includes a cylindrical outer tank 101, a cylindrical inner tank 107 concentrically disposed with the outer tank, and an outer tank 101 to close the inside of the device. Includes a cover 112 provided on top of. At this time, the material of each of the outer tank and the inner tank is not particularly limited as long as no phenomenon such as corrosion by plating wastewater occurs. For example, it may be made of stainless steel. In addition, the cover may also be made of the same material as the outer tank and the inner tank, but may be made of a polymer material to facilitate molding.

In the illustrated embodiment, a first discharge pipe 110 is provided on the lower side of the outer tank 101 and a second discharge pipe 111 is provided on the upper side. At this time, as will be described later, the first discharge pipe 110 is a first treatment liquid having a high activated carbon mixture content located near the bottom of the outer tank 101 among the first treatment liquid formed by adsorption treatment of nickel plating wastewater. (100) It is for discharging to the outside. On the other hand, the second discharge pipe 111 transfers the first treatment liquid, which is located near the upper side of the outer tank 101 and has a low activated carbon mixture content, out of the first treatment liquid formed by the adsorption treatment of the nickel plating wastewater to the outside of the device 100. It is intended to be discharged as

On the other hand, the inner tank 107 is formed extending from the cover 112, and at this time, it can be fixed to the cover using a fixing or fastening means (eg, bolt fastening, rivet bonding, etc.), alternatively the cover ( 112) may be manufactured in an integrated form. In the illustrated embodiment, an agitator 108 is installed at the center of the cover to induce uniform mixing of the contents of the inner tank 107, that is, the nickel plating wastewater and the aqueous dispersion of the activated carbon mixture. In addition, the stirrer 108 may include a stirring blade having a shape for pushing the contents of the inner tank 107 downward. Since the shape of the agitation blade capable of transferring the fluid in the downward direction is well known in the art, a detailed description thereof will be omitted.

In the illustrated embodiment, the lower end of the inner tank 107 is spaced apart from the bottom of the outer tank 101 by a predetermined distance, so that the inner space of the outer tank in which the contents of the inner tank are concentrically arranged (the inner tank A movable first fluid flow space (A) is provided, which is bounded by the outer surface and the inner surface of the outer tank.

The inside of the inner tank 107 is configured so that a vortex is generated by the agitator 108 . In contrast, the inner space of the outer tank has a volume of, for example, about 2 to 10 times, specifically about 3 to 8 times, and more specifically about 4 to 7 times the volume of the inner tank, thereby inducing a decrease in flow rate. Under the action of gravity, the activated carbon mixture can be caused to sink toward the bottom of the outer tank. In addition, the width of the first fluid flow space A is not particularly limited, and is not limited to a specific value as long as the contents of the inner tank can move to the inner space of the outer tank during the flow of the fluid by the agitator.

Referring to FIG. 2, the treatment device 100 takes the contents of the inner tank 107 out of the device to increase the contact and adsorption efficiency between the nickel plating wastewater and the aqueous dispersion of the activated carbon mixture, and then the inner tank again. It is provided with a recycling unit for introducing into. At this time, the recycling unit includes a recycling pipe 103, a pump 104 and a pressurized recycling pipe 106. The recycling pipe 103 is installed so that a part of the contents of the inner tank 107 (in the illustrated embodiment, the contents of the upper region in the inner tank) is sucked in by the pump 104 and discharged to the outside of the device. At this time, the recycling pipe 103 may extend via or through the cover 112 provided at the top of the outer tank 101, and the contents sucked by the pump 104 are pressed back into the inner tank ( 107), in the illustrated example, it is transferred to the inner space of the inner tank via the bottom of the outer tank 101 by the pressurized recycle pipe 106. At this time, the pressurized recycling pipe 106 may extend to the inside of the inner tank 107, for example, to the height of the central region.

According to the illustrated embodiment, at the end of the pressurized recycling pipe 106, a spray pipe for injecting a mixture of the contents transferred to the inner tank by the recycling unit and the aqueous dispersion of the new activated carbon mixture into the inner tank 107 ( 109) is provided. At this time, the injection pipe 109 is connected or communicated with the activated carbon inlet pipe 102 for supplying the aqueous dispersion of the new activated carbon mixture, and the contents transferred through the pressurized recycling pipe 106 are mixed with the aqueous dispersion of the new activated carbon mixture. At this time, the mixture is injected toward the agitator 108 through the spray pipe 109 in the inner space of the inner tank 107, specifically, in the inner space of the inner tank 107, in the region below the agitator 108.

In this way, the recycling unit takes out a part of the contents distributed in the relatively upper space in the inner tank 107 and transfers it to the relatively lower space in the inner tank 107 in a pressurized state while passing through the outer loop to move upward. It can perform the function of spraying with.

In the illustrated embodiment, the activated carbon inlet pipe 102 is connected to an external supply source (not shown), and may extend into the inner tank 107 via the bottom of the outer tank, and has an end region thereof. By being bent and configured to be in fluid communication with the injection pipe 109, the recycled contents and the new activated carbon mixture aqueous dispersion can be mixed in the injection pipe 109. The introduction amount of the new activated carbon mixture aqueous solution may be determined by calculating the amount of the activated carbon mixture contained in the first treatment liquid discharged through the first discharge pipe 110 and the second discharge pipe 111, respectively.

On the other hand, in the illustrated embodiment, the injection pipe 109 is configured to have a shape in which the width of the passage through which the fluid flows is tapered and then expanded again (ie, a passage structure having a shape similar to an orifice is formed). At this time, the activated carbon inlet pipe is connected or communicated to or near the orifice region, so that the aqueous dispersion of the new activated carbon mixture introduced through the activated carbon inlet pipe 102 can be easily introduced into the injection pipe.

The first treatment liquid subjected to adsorption treatment contains a mixture of nickel plating wastewater having a reduced metal content and adsorption treatment activated carbon.

Referring back to FIG. 2 , an inverted funnel-shaped inclined plate 105 is provided at the bottom of the outer tank 101 (specifically, along the bottom periphery), so that the first treatment liquid that has undergone adsorption passes through the first fluid flow space. Through (A), it escapes into the inner space of the outer tank (that is, the space between the outer surface of the inner tank and the inner surface of the outer tank), and passes through a flow space that becomes narrower toward the upper side in the inclined plate. At this time, the upper end of the inclined plate 105 is open to form a second fluid flow space B through which fluid can flow. In addition, the inclined plate 105 may be made of stainless steel or the like.

In this way, resistance to the flow of the first treatment liquid that has passed through the first fluid flow space (A) is induced by the inclined plate 105 that induces the flow path to be reduced as it goes upward, and the second fluid flow space (B) As it passes through, the flow velocity of the fluid is significantly reduced due to rapid expansion.

As a result, the fluid containing a relatively large amount of the activated carbon mixture stays in the lower region of the outer tank 101, while the fluid containing a relatively small amount of the activated carbon mixture resides in the upper region of the outer tank. At this time, the first treatment liquid having a high activated carbon mixture content and A first treatment liquid having a low content of the activated carbon mixture is discharged. In this way, the wastewater treatment process and separation process can be implemented in a single device, and in particular, the separation process can be easily performed by arranging a inclined plate having a simple structure in the treatment device 100 and using gravity without a separate complicated device. .

Referring to FIG. 1 , the first treatment liquid having a low activated carbon mixture content is transferred to a subsequent membrane process (ie, microfiltration and nanofiltration) without separate treatment. On the other hand, since the first treatment liquid having a high activated carbon mixture content has a relatively high activated carbon content, once the adsorbed activated carbon mixture is settled through a stationary process, and the supernatant liquid is mixed with the first treatment liquid having a low activated carbon mixture content. It is introduced into the microfiltration stage. At this time, the spent activated carbon separated through the stationary process may be discarded after removing residual wastewater or used through a regeneration process. Since this regeneration process is well known in the art, a detailed description thereof will be omitted.

microfiltration process

Although the metal content of the first treatment liquid formed by the previously performed adsorption process is significantly reduced, there is a limit to reducing the metal content to a level suitable for legal emission standards or drinking water. In addition, it may still contain a part of the activated carbon mixture used as an adsorbent (most of the activated carbon mixture can be removed through separation in the device and subsequent stationary process as described above), fine solids contained in the original nickel plating wastewater, and the like. can

According to FIG. 1 , a microfiltration step is performed on the first treatment liquid to form a second treatment liquid, specifically, a polyvalent metal ion-containing second treatment liquid. At this time, microfiltration corresponds to a membrane separation process using a mechanism by sieving. Microfiltration has accurate filtration precision, and compared to methods such as ultrafiltration, nanofiltration, and reverse osmosis, the filtration resistance is low due to the relatively large pore size, so the filtration capacity is high and the life of the membrane is long.

The pore size of the membrane for this microfiltration treatment is, for example, in the range of about 0.1 to 10 μm, specifically about 0.2 to 5 μm, more specifically about 0.3 to 1 μm, and it is difficult to remove metal ions such as nickel. Although it is practically difficult, it is possible to lower the turbidity by removing suspended particles (activated carbon particles, etc.), colloids, dissolved organic matter, etc. contained in the first treatment liquid, and in particular, by lowering the load of the subsequent nanofiltration step, the membrane for nanofiltration shortening of life can be prevented.

In an exemplary embodiment, the material of the microfiltration membrane can be selected from types known in the art, for example, polysulfone, polyvinylidene fluoride (PVDF), polypropylene, polyethylene, polyether sulfone, and polyamide. , cellulose acetate and the like.

In addition, the permeability of the microfiltration membrane may be, for example, in the range of about 30 to 400 LMH, specifically about 50 to 300 LMH, and more specifically about 80 to 200 LMH. In addition, since the pH is not particularly limited, for example, in the range of about 1 to 14, specifically about 2 to 13, the addition of a material for pH adjustment may not be required in the present invention.

According to an exemplary embodiment, the driving pressure (ie, pressure difference) applied in the microfiltration step is, for example, in the range of about 1 to 3 bar, specifically about 1.5 to 2.5 bar, more specifically about 1.7 to 2 bar. Adjustable, but not limited thereto. In addition, the form of the membrane may be a hollow fiber membrane, a flat membrane, a spiral wound membrane, etc., but a hollow fiber membrane is advantageous in terms of efficiency.

As such, through the microfiltration step, most of the activated carbon mixture particles and fine solids remaining in the first treatment liquid can be removed, which can reduce the load applied to the membrane during nanofiltration, which is a subsequent step. However, during the microfiltration process, multivalent metal ions (specifically, multivalent metal cations) in the first treatment liquid are hardly removed and remain in the form of ions, specifically multivalent cations.

nanofiltration process

Referring back to FIG. 1 , the second treatment liquid subjected to the microfiltration process is transferred to the nano filtration process, thereby forming a purified third treatment liquid. In the case of nanofiltration, since polyvalent ions contained in the introduced fluid can be removed, the third treatment liquid may be a fluid in which polyvalent metal ions are removed or significantly reduced. At this time, heavy metals (nickel, chromium, zinc, copper, iron, etc.) contained in the nickel plating wastewater exist in the form of multivalent cations and therefore do not pass through the nanofiltration membrane, whereas monovalent ions pass through the membrane. In this regard, nanofiltration uses a separation mechanism by solvent diffusion, unlike the previously described microfiltration. In an exemplary embodiment, the driving pressure (pressure difference) during nanofiltration may range, for example, from about 6 to 17 bar, specifically from about 9 to 15 bar, and more specifically from about 10 to 14 bar.

On the other hand, the membrane used for nanofiltration, for example, may exhibit a pore size in the range of about 5 nm or less, specifically about 0.1 to 3 nm, and more specifically about 0.5 to 1 nm, in the second treatment liquid to be treated. It may be determined in consideration of the size of the contained polyvalent metal ion, and the like.

In an exemplary embodiment, such a membrane for nanofiltration may exhibit a separation ability for divalent or higher ionic substances in the first aqueous solution, and has a cutoff molecular weight of, for example, about 200 to 1000 Daltons, specifically about 300 to about 300 Daltons. It may be in the range of 900 Daltons. In addition, the permeability of the membrane for nanofiltration may be, for example, about 20 to 80 LMH, specifically about 30 to 70 LMH, and more specifically about 40 to 60 LMH. However, the present disclosure is not limited to the range of values related to the properties of the membrane described above, and various changes are possible.

According to exemplary embodiments, the membrane for nanofiltration may be made of polyamide, polyamide-polyethyleneimine, polyacrylonitrile, or the like, and may be specifically made of polyamide.

In an exemplary embodiment, the membrane for nanofiltration may be in the form of a flat membrane, spiral wound or hollow fiber membrane, and more specifically, may be in the form of a hollow fiber membrane. According to certain embodiments, the membrane module in nanofiltration can be a hollow fiber cross-flow membrane module.

In this regard, the metal ion removal rate may be expressed by Equation 1 below.

[Equation 1]

In the above formula, C _i and C _f respectively mean the metal concentration (mg/L) before and after the treatment process.

According to an exemplary embodiment, the majority of multivalent metal cations can be removed through the nanofiltration membrane, for example, at least about 85% (specifically, at least about 90%, more than about 90%) of nickel cations compared to the initial nickel plating wastewater. specifically at least about 95%), at least about 80% (specifically at least about 90%, more specifically at least about 95%) of chromium cations, at least about 90% (specifically at least about 95%, more specifically at least about 95%) of zinc cations. at least about 99%), at least about 90% (specifically at least about 92%, more specifically at least about 95%) of copper cations, and at least about 85% (specifically at least about 90%, more specifically at least about 95%) of iron cations. about 95%) can be removed.

The third treatment liquid obtained through the above-described nanofiltration process has significantly reduced polyvalent metal ions, and may contain monovalent ions in addition to water. After being treated in this way, it can be recovered and used as industrial water without additional treatment, or discharged off-site, as long as the legal permissible standards can be met. Alternatively, it may be required to remove monovalent ions, trace amounts of heavy metal ions, etc. remaining in the third treatment liquid in order to use it as drinking water. To this end, a reverse osmosis filtration process may be additionally performed.

Hereinafter, preferred embodiments are presented to aid understanding of the present invention, but the following examples are provided to more easily understand the present invention, but the present invention is not limited thereto.

Example

- Provision of nickel plating wastewater

In this embodiment, nickel plating wastewater discharged from a plating company of a light plating cooperative complex in Ansan, Gyeonggi-do, Korea was procured and used.

The concentrations of metal components in the received nickel plating wastewater are shown in Table 2 below.

ingredient Concentration (mg/L) Nickel (Ni) 135 Chromium (Cr) 109 Zinc (Zn) 52 Copper (Cu) 28 Iron (Fe) 73 Other metals (Cd, As, etc.) 45

In addition, the pH of the nickel plating wastewater was 3.8, and the concentration of total dissolved solids was 78 mg/L.

- Preparation of activated carbon mixtures

In this embodiment, an activated carbon mixture was prepared by preparing activated carbon from oak and bamboo, respectively, and then mixing them in a predetermined ratio.

In the case of oak-derived activated carbon, oak was cut into cubes (2.0 × 2.0 × 2.0 cm), pulverized using a high-energy ball mill, and then dried in an oven maintained at 110 ° C. for 24 hours. Activated carbon was obtained by carbonizing 10 g of dried oak pieces by heating them to 600° C. at a rate of 5° C./min in a nitrogen atmosphere for 2.5 hours. The size (diameter) of the oak-derived activated carbon obtained ranged from 150 to 200 μm.

On the other hand, bamboo-derived activated carbon was first cut into small sizes of bamboo skins, washed with water three times, and then dried at 60° C. for 4 hours. Thereafter, the dried bamboo skins were cut into appropriate sizes and then pulverized using a high-energy ball mill. Thereafter, the pulverized product was heated to 420° C. at a rate of 5° C./min in a nitrogen atmosphere for 2 hours to obtain carbonized activated carbon. The size (diameter) of the obtained bamboo-derived activated carbon ranged from 90 to 180 μm.

The properties of each of the two kinds of activated carbons prepared as described above are shown in Table 3 below.

division Oak-Derived Activated Carbon Bamboo-derived activated carbon BET specific surface area (㎡/g) 335 1128 Pore volume (cm3/g) 0.27 1.21 Pore diameter (nm) 3.7 2.6

After combining the obtained two kinds of activated carbon in the weight ratio shown in Table 4, they were uniformly mixed to prepare activated carbon or activated carbon mixture.

division Oak-Derived Activated Carbon: Bamboo-Derived Activated Carbon Example 1 1:1 Example 2 1:1.8 Comparative Example 1 Use only oak-derived activated carbon Comparative Example 2 Uses only bamboo-derived activated carbon

Thereafter, activated carbon (Comparative Examples 1 and 2) or activated carbon mixtures (Examples 1 and 2) were added to deionized water, respectively, to prepare an aqueous dispersion with a concentration of 8% (w/w).

Then, the nickel plating wastewater and the aqueous dispersion of activated carbon (or activated carbon mixture) provided above were combined. At this time, the weight ratio of nickel plating wastewater: activated carbon (or activated carbon mixture) in the aqueous dispersion was adjusted to 1:0.09. Adsorption treatment was performed for 3 hours under agitation (production of a first treatment liquid), and then the mixture was allowed to stand to separate an upper layer having a low activated carbon concentration and a lower layer having a high activated carbon concentration at a ratio of 1:1 based on volume. The separated lower layer liquid was allowed to stand again, and then activated carbon solids were removed.

Thereafter, the first treatment liquid separated into the supernatant in the adsorption treatment process and the first treatment liquid in which the activated carbon content was reduced by the additional stationary process were combined, transferred to a microfiltration module, and filtered (second treatment liquid). At this time, the microfiltration membrane was a polysulfone membrane commercially available under the trade name MF-Millipore, and at this time, the pore size was about 0.45 μm. During microfiltration, the driving pressure was set to 1.8 bar.

Subsequently, the fluid subjected to the microfiltration step was transferred to the nanofiltration module and filtered (third treatment liquid). At this time, the nanofiltration membrane was a commercially available polyamide-based membrane under the trade name NF-270, and had a pore size of 0.8 nm. The driving pressure during nanofiltration was set to 8.7 bar.

Concentration between the treatment liquid obtained through adsorption treatment using activated carbon or activated carbon mixtures according to Comparative Examples 1 and 2 and Examples 1 and 2, respectively, and subsequent membrane processes (microfiltration and nanofiltration) and raw plating wastewater The removal rate was calculated based on, and the results are shown in Table 5 below.

metal Example 1 Example 2 Comparative Example 1 Comparative Example 2 Nickel (Ni) 98% 99% 89% 91% Chromium (Cr) 94% 96% 88% 91% Zinc (Zn) 96% 98% 87% 87% Copper (Cu) 90% 93% 84% 89% Iron (Fe) 88% 90% 80% 86% Other metals (Cd, As, etc.) 85% 89% 79% 70%

As shown in the table above, the removal rates of nickel in the treatment solutions obtained in Examples 1 and 2 were 98% and 99%, which were less than the legal standard of 3 mg/L.

On the other hand, when bamboo-derived activated carbon was used alone (Comparative Example 2), a relatively good removal rate was shown compared to when oak-derived activated carbon was used alone (Comparative Example 1), but the level was still lower than that of Example. and, in particular, the concentration of nickel in the treatment liquid exceeded the legal standard.

On the other hand, when the adsorbent in the form of an activated carbon mixture in which activated carbon derived from oak and bamboo is combined in a predetermined ratio as in Examples 1 and 2 is used, a good removal rate for metals (or heavy metals) other than nickel in plating wastewater is obtained. could get This is because the non-uniform adsorption phenomenon due to the difference in properties suitable for adsorption of each of a plurality of metal cations in the nickel plating wastewater is mitigated by using a combination of two types of activated carbon having different properties as in the example, so that various metals in the nickel plating wastewater It is judged that it provided good adsorption capacity.

Comparative Example 3

Nickel plating wastewater was treated according to the same procedure as in Example 1, except that microfiltration was not performed, and performance degradation due to fouling or clogging of the nanofiltration membrane was observed over time. In addition, the same observation was made for the nanofiltration membrane used in the treatment process according to Example 1.

As a result of the observation, even when the nanofiltration membrane in Example 1 was repeated three times a day for three weeks, no significant performance problems were observed. On the other hand, in the case of Comparative Example 3, after 1 week, it was confirmed that solids such as colloids present in the nickel plating wastewater were deposited on the surface of the membrane, and the nanofiltration performance was significantly reduced.

Considering the above results, although microfiltration itself is not a decisive factor for metal removal in nickel plating wastewater, solids contained in raw nickel plating wastewater, especially various suspended substances present in the form of fine colloids, are adsorbed during the adsorption process. If it is introduced into the subsequent nanofiltration step without being removed in a significant amount from the activated carbon, it exerts an excessive load on the nanofiltration membrane, which undesirably affects the long-term operation of the entire process. It is determined that the above problems can be effectively suppressed by interposing a microfiltration step between the.

Comparative Example 4

The nickel plating wastewater was treated in the same manner as in Example 1, except that the membrane process (microfiltration and nanofiltration) was not performed. Thus, after performing only the adsorption treatment, the nickel concentration in the treatment liquid was 19.3 mg/L. It can be seen that this is a level that significantly exceeds the allowable value of nickel in the current regulated discharge of wastewater.

As such, although adsorption by two types of activated carbon mixtures is effective in removing various metals in plating wastewater, there is a limit to reducing them to an extremely low level. It is believed that the nickel content can be reduced to a low level of 3 mg/L or less.

As described above, the treatment process according to the embodiment is useful in that it can implement an eco-friendly process performed by a physical method instead of a chemical treatment method according to the addition of a chemical substance.

Example 3

Assessment of impact of pretreatment step using wood sawdust

Sawdust generated in the process of processing oak obtained from a wood sawmill was sieved using a KS standard sieve, and types with a particle size of 2 mm or less were collected. After removing foreign substances in the sawdust by washing with distilled water, it was completely dried for 1 day in a dryer maintained at a temperature of 105 ° C. Then, the dried sawdust was compressed to a density of 40 g/L to prepare a pre-treatment layer, which was then filled in a cylinder tube in a fixed manner.

The plating wastewater was treated according to the same procedure as in Example 1, except that the nickel plating wastewater was first pretreated through a bed filled with sawdust and then combined with an aqueous dispersion of an activated carbon mixture. At this time, the pretreatment device was composed of a cylindrical adsorption tower made of stainless steel with an inner diameter of 10 cm and a height of 150 cm.

As a result, the time required to achieve the same adsorption effect as in Example 1 (i.e., the nickel concentration is reduced from 135 g/L to 19.3 mg/L) during the adsorption process using the activated carbon mixture was reduced by approximately 10%, In particular, it was confirmed that the replacement cycle of the adsorbent was extended by more than 30% in repeated experiments. Despite the fact that sawdust has a lower porosity than activated carbon, it can not only provide metal removal ability during the pretreatment process with sawdust, but also block pores present on the surface of activated carbon by various solids contained in plating wastewater in a considerable amount. It is believed that this is because the phenomenon of shortening the life of the adsorbent is significantly alleviated.

All simple modifications or changes of the present invention belong to the scope of the present invention, and the specific scope of protection of the present invention will be clarified by the appended claims.

Claims (6)

a) contains at least 50 mg/L nickel, at least 30 mg/L chromium, at least 20 mg/L zinc, at least 10 mg/L copper, and at least 50 mg/L iron, and has a pH of 5 or less; and providing an aqueous nickel plating wastewater having a total dissolved solids concentration of at least 40 mg/L;
b) providing an aqueous dispersion of an activated carbon mixture combining oak-derived activated carbon and bamboo-derived activated carbon;
c) contacting the water-based nickel plating wastewater with an aqueous dispersion of the activated carbon mixture to adsorb and remove a part of metal components in the nickel plating wastewater by the activated carbon mixture to form a first treatment liquid having a reduced metal content, which is (i) ) separating into a first treatment liquid having a high activated carbon mixture content and (ii) a first treatment liquid having a low activated carbon mixture content;
d) After the first treatment liquid having a high activated carbon mixture content is allowed to stand, the supernatant thereof is transferred to a microfiltration step, while the first treatment liquid having a low activated carbon mixture content is transferred to a microfiltration step without being allowed to stand, thereby forming solids forming a multivalent metal ion-containing second treatment liquid having a reduced content; and
e) transferring the second treatment liquid to a nanofiltration step to form a third treatment liquid from which polyvalent metal ions are removed;
Including,
In step c),
A first discharge pipe for discharging the first treatment liquid having a high activated carbon mixture content in the lower region, a second discharge pipe for discharging the first treatment liquid having a low activated carbon mixture content in the upper region, and a cylinder shape having a cover on the top. outer tank;
It extends from the cover while forming a concentric structure with the outer tank, and a lower end thereof is spaced apart from the bottom of the outer tank at a predetermined distance to provide a first fluid flow space, and has a cylindrical shape with an agitator connected to the cover. an inner tank of the inner tank, wherein the inner tank is configured to transfer contents to the outer tank side through the first fluid flow space;
A recycle pipe communicating with the inside of the inner tank and discharging some of the contents of the inner tank to the outside, a pump arranged to suction the contents of the inner tank through the recycle pipe and discharging them in a pressurized state, and a bottom of the outer tank. A recycling unit including a pressurized recycling pipe communicating with the inner tank through and transferring the contents pressurized by the pump to the inner tank, and a spray pipe for injecting the contents transferred to the end of the pressurized recycling pipe into the inner tank provided;
An activated carbon inlet pipe extending into the inner tank via the bottom of the outer tank to supply an aqueous dispersion of the new activated carbon mixture and connected to the injection pipe, wherein the recycled contents and the aqueous dispersion of the new activated carbon mixture are mixed. is sprayed into the inner tank through the injection pipe; and
an inverted funnel-shaped inclined plate disposed on the bottom surface of the outer tank and having an upper end spaced apart from the outer surface of the inner tank by a predetermined distance to provide a second fluid flow space;
It is performed using a processing device comprising a,
At this time, the treatment liquid that has passed through the second fluid flow space is separated under the action of gravity into (i) a first treatment liquid having a high activated carbon mixture content and (ii) a first treatment liquid having a low activated carbon mixture content, respectively in the first discharge pipe and A method of treating nickel plating wastewater discharged through the second discharge pipe. The method of claim 1, further comprising pre-treating the aqueous nickel plating wastewater using a filter filled with wood sawdust having a particle size of 2 mm or less in an amount of 15 to 50 g / L prior to step c). Nickel plating wastewater treatment method characterized by. delete The method of claim 1, wherein the injection pipe has an orifice area that expands after its width is tapered, and an activated carbon inlet pipe is connected to the orifice area. The method of claim 1, wherein the combination ratio of oak-derived activated carbon and bamboo-derived activated carbon in step b) is in the range of 1:0.5 to 4 by weight. The method of claim 1, wherein in step c), the weight ratio of the aqueous nickel plating wastewater: the activated carbon mixture in the aqueous dispersion of the activated carbon mixture is controlled in the range of 1:0.01 to 0.5.

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