CN102491568A - Method for treating wastewater of electrolytic zinc rinsing technology - Google Patents

Abstract

The invention discloses a method for treating wastewater in an electrolytic zinc rinsing process. The method is a combined treatment of countercurrent rinsing, electrodeposition, and membrane separation: countercurrent rinsing: the cathode plate used in electrolytic zinc production enters a countercurrent rinsing device for rinsing, including: entering the first stage first Countercurrent rinsing tank, that is, concentrated water tank, the cleaning direction of the plate is opposite to the direction of water flow, and then enters the last level tank, that is, clear water tank, to complete the rinsing process; electrodeposition: the concentrated water after rinsing enters the flat plate electrodeposition device, three-dimensional electrodeposition device to recover metal zinc in wastewater; membrane separation: the wastewater after electrodeposition enters the ultrafiltration membrane system and reverse osmosis membrane system in turn, and the concentrated solution produced by the membrane system flows back into the electrodeposition device to recover the metal zinc in the membrane concentrated solution , the membrane effluent is returned to the countercurrent rinsing device. The invention has the advantages of realizing the recycling of waste water through the combination of countercurrent rinsing, electrodeposition and membrane separation technology, and basically realizing complete recovery and zero discharge of heavy metal pollutants.

Description

Electrolytic zinc rinsing process wastewater treatment method

technical field

The invention relates to a method for treating industrial waste water, in particular to a combined treatment method for countercurrent rinsing of cathode plates used in the production process of electrolytic zinc, electrodeposition and membrane separation for the waste water after rinsing.

Background technique

In the process of electrolytic production of zinc, a large amount of rinsing wastewater will be generated during the process of metal stripping and plate cleaning. Rinsing wastewater contains zinc, lead, cadmium and other heavy metal ions. Due to its large amount of water and high concentration of heavy metals (especially zinc ions), if it is discharged directly without treatment, it will have a serious impact on the surrounding environment. At the same time, the heavy metal resources contained in it will also be wasted. How to effectively deal with electrolysis Zinc rinsing process wastewater is the focus of attention in mining, electroplating, electrolytic production of zinc and other industries. Efficient and low-cost removal of heavy metal ions in wastewater, while realizing wastewater reuse and heavy metal recovery is the development direction of heavy metal wastewater treatment in the future. Traditional methods for treating heavy metal wastewater include: chemical treatment, biological treatment, and electrochemical treatment. However, when chemical methods are used to treat wastewater containing heavy metals, due to the influence of precipitants and environmental conditions, the effluent concentration of precipitation methods often does not meet the requirements. , needs further treatment; although the biological treatment method has the advantages of low cost and convenient treatment, the tolerance concentration of general microorganisms to heavy metal ions is very small, and it is difficult to treat heavy metal wastewater on a large scale; in the past, electrochemical methods were used for wastewater treatment. When the concentration of medium and heavy metals is reduced, there are problems of high energy consumption and poor treatment effect.

Domestically, electrolysis is mainly used to process industrial wastewater from zinc smelting and electroplating enterprises; it is difficult to meet the standard for heavy metal wastewater treatment by traditional heavy metal precipitation process, and the wastewater will seriously pollute the environment after being discharged, the recovery rate is low, the recycled water quality is poor, and heavy metal pollutants cannot be recycled. In the current situation of wasting resources and easily causing secondary pollution, the new treatment method developed by the present invention can basically realize complete recovery and zero discharge of heavy metal pollutants, and a new process of completely recycling water resources.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies existing in the prior art, and provide a kind of electrolytic zinc rinsing process wastewater treatment method with low investment and high benefit.

The technical scheme of the present invention is: the electrolytic zinc rinsing process wastewater treatment method, the method is a combination of three steps of countercurrent rinsing, electrodeposition, and membrane separation:

Step 1: Rinse with countercurrent

Countercurrent cleaning is composed of several tanks connected in series. Water is fed into the last tank (clean water tank) and drained from the first tank (concentrated water tank). The direction of water flow is opposite to that of the plate cleaning process. The cathode plate used in the production of electrolytic zinc enters the countercurrent rinsing device for rinsing, first enters the first level of countercurrent rinsing tank (concentrated water tank), and finally enters the last level of tank (clear water tank) to complete the rinsing process;

Through countercurrent rinsing, the electrode plate moves with the production direction and the electrode plate is washed more and more cleanly, while the concentration of pollutants in the cleaning water is getting higher and higher, with less water consumption and high cleaning efficiency.

The number of series water tanks used is generally 4-10, preferably 4-8, particularly preferably 6-8, and those skilled in the art can adjust according to the corresponding specific conditions;

Step 2: Electrodeposition

The concentrated water after rinsing enters the regulating tank, adjusts its water volume and flow rate, and then enters the flat-plate electrodeposition device and the three-dimensional electrodeposition device in turn to recover metal zinc in the wastewater;

Electrodeposition refers to flat-plate electrodeposition devices and three-dimensional electrodeposition devices;

The adjusted water volume and flow rate should be determined according to the requirements of specific experiments. In this experiment, the adjusted water volume is 5m ³ and the flow rate is 1m ³ /h.

Step Three: Membrane Separation

The wastewater after electrodeposition enters the ultrafiltration membrane system and the reverse osmosis membrane system in turn. The wastewater passes through the two-stage membrane separation system, that is, the concentrated solution obtained from the ultrafiltration membrane system and the reverse osmosis membrane system, and returns to the regulating tank before electrodeposition, and then Metal zinc in the membrane concentrate is recovered through a flat-plate electrodeposition device and a three-dimensional electrodeposition device. The effluent from the ultrafiltration membrane system enters the reverse osmosis membrane system for further treatment, and the effluent from the reverse osmosis membrane system flows back to the last stage tank (clean water tank) in the countercurrent rinsing device;

Membrane separation refers to the separation of ultrafiltration membrane system and reverse osmosis membrane system;

The wastewater reused after electrodeposition and membrane system treatment has only one outlet, which comes from the reverse osmosis system;

The recovery of metal zinc comes from two parts, one part is from the electrodeposition process of the wastewater after countercurrent rinsing, and the metal zinc in the wastewater after countercurrent rinsing is recovered; the other part comes from the wastewater after electrodeposition, which is passed through the ultrafiltration membrane system, The concentrated solution produced after the reverse osmosis membrane system is returned to the electrodeposition process after the electrodeposition device, and the metal zinc in the concentrated solution produced by the membrane system in this combined treatment method is recovered.

The process conditions and functions of each component are stated below:

Countercurrent rinsing controls the concentration of Zn ²⁺ in the countercurrent rinsing water to about 3000mg/L by the number of times the plates are cleaned;

Adjusting pool: used for water storage, adjusting its water volume and flow rate, and stabilizing water flow; the adjustment of water volume and flow rate should be determined according to the requirements of specific experiments. In this experiment, the adjusted water volume is 5m ³ and the flow rate is 1m ³ /h.

The minimum concentration of Zn ²⁺ in the flat-plate electrodeposition device is reduced to 800mg/L;

Commonly used flat-plate electrodeposition devices include: an electrolytic cell for electrochemical process disclosed in CN1930325, and a diaphragm method metal anode electrolytic cell disclosed in CN1995461.

The conditions for the three-dimensional electrodeposition treatment of zinc-containing wastewater are as follows: the electrode material is a graphite anode/stainless steel cathode paired electrode, and the cell voltage and electrolysis time need to be determined according to the concentration of zinc ions in the wastewater and the hydraulic retention time. Generally, the cell voltage is 4.0V-8.0V, the electrolysis time is 60min-90min; three-dimensional electrodeposition is to fill granular or other debris-like working electrode materials between the electrodes of the traditional two-dimensional electrolytic cell, and to charge the surface of the filled granular electrode materials, which has become a new Pole (third pole), electrochemical reaction can occur on the surface of the working electrode material; the minimum concentration of Zn ²⁺ treated by the three-dimensional electrodeposition device is lower than 80mg/L, and the removal rate of zinc ions is more than 90%;

Commonly used three-dimensional electrodeposition devices include: a three-dimensional electrode reactor disclosed in CN101186361 and a three-dimensional electrode reactor in a method for treating chlorobenzene wastewater using it, a three-dimensional electrode reactor disclosed in CN101514040 and its application in refractory organic wastewater treatment Three-dimensional electrode reactors in applications.

The ultrafiltration membrane system removes suspended solids, colloids and other substances in the water. The water quality meets the requirements of reverse osmosis (mainly SDI (silting index) < 3.0, turbidity is less than 0.10). The average removal efficiency of zinc ions in the ultrafiltration separation process is 60% to 70%, adding 15mg/L potassium sodium tartrate PST, the removal efficiency of zinc ions reaches 99%;

CP压力式超滤系统。Commonly used ultrafiltration membrane systems, such as the Millipore ultrafiltration system (labscale TFF small tangential flow ultrafiltration system, Congent-M ultrafiltration system, Pellicon ultrafiltration system) produced by Millipore Corporation of the United States, GE’s 1500 pressure ultrafiltration membrane system, SIEMENS company

CP pressure ultrafiltration system.

Said in the reverse osmosis separation process, the operating pressure used is controlled at 0.7-1.0MPa, the concentration of Zn ²⁺ in the effluent water is reduced to 0.1-0.5mg/L, the average removal efficiency of zinc ions is 90%, and the conductivity of the effluent water is reduced to 50μS/cm; the working temperature of wastewater is 25℃～35℃, the water production rate of reverse osmosis membrane process is 60%～70%, and the average retention rate is 92%～95%. Used in industrial circulating water systems or water points with high water quality requirements;

Commonly used reverse osmosis membrane systems such as YMRO-0.25-500 reverse osmosis water treatment system produced by Dongguan Yimin Water Treatment Technology Co., Ltd., and 2T/H single-stage reverse osmosis equipment produced by Beijing Kaineng Liyuan Environmental Engineering Technology Co., Ltd.

The waste water after the above treatment is firstly treated with ultrafiltration membrane, and then separated by reverse osmosis membrane to ensure the water effluent effect of reverse osmosis, save the energy required by reverse osmosis equipment, fully concentrate the heavy metals in the waste liquid, and make the concentrated liquid The concentration of metal ions has been greatly improved, which is suitable for the recovery of heavy metals by electrodeposition;

The two-stage membrane separation process produces 30% to 40% of the concentrated solution, which is recycled into the regulating tank for reuse, metal zinc is recovered, and the effluent is reused in the clear water tank in the countercurrent rinsing device, so that the heavy metal pollutants in the entire device are basically eliminated. Complete recycling and zero emissions can be achieved.

Compared with the prior art, the present invention has the following advantages:

First, use a countercurrent rinsing device to rinse the cathode plates used in the electrolytic zinc production process. The electrode plates moving along the production direction become cleaner and cleaner, while the concentration of pollutants in the washing water is getting higher and higher, and the water consumption is less. The cleaning efficiency is high, and it is beneficial to the reuse of waste water and the recovery of heavy metal ions.

Second, using electrodeposition to recover metal zinc from the countercurrent rinsing effluent with high zinc ion content, and then the wastewater is treated with a membrane, which can fully concentrate the heavy metals in the waste liquid and greatly increase the concentration of metal ions in the concentrated liquid , combined with electrodeposition technology, is very suitable for electrolytic recovery of heavy metals, and is easy to realize the recycling of wastewater. Combining electrodeposition technology and membrane separation treatment process, the advantages of electrodeposition and membrane separation technology are fully utilized, and the problems existing in the previous electrochemical reduction treatment method are solved.

Third, the waste water purification reuse and heavy metal recovery of heavy metal wastewater treatment are completed at the same time, realizing a virtuous cycle of production and treatment.

Fourth, propose corresponding treatment process methods for wastewater with different concentrations and compositions, and provide theoretical guidance for rational design of devices and optimization of operating processes.

The waste water treated by the process of the present invention is all returned to the countercurrent rinsing device to supplement the required water volume in the countercurrent rinsing device. From the generation of waste water to the reflux of treated waste water, a water cycle is formed, and the operation cost is low. The whole process only has one clean water tank. It is discharged and reused at the outlet, and the heavy metal pollutants can basically achieve complete recovery and zero discharge.

According to the advantages of countercurrent rinsing, electrodeposition and membrane separation technology, it can achieve the lowest operating cost and the best separation effect, realize the discharge of water up to the standard, and effectively recover the heavy metal resources in the wastewater. While effectively recovering the heavy metals in the wastewater, Realize water recycling.

Description of drawings

Fig. 1 is the process flow chart of the "zero discharge" treatment process of electrolytic zinc rinsing process wastewater of the present invention

Detailed ways

An embodiment is listed below, and the present invention is further described in conjunction with the accompanying drawings, but the present invention is not limited to this embodiment.

Example 1

The method step of the present invention adopts the process combination of countercurrent rinsing-flat plate electrodeposition device-three-dimensional electrodeposition device-ultrafiltration membrane system-reverse osmosis membrane system, and the specific process flow is as follows:

Step 1: Rinse with countercurrent

Countercurrent cleaning is composed of four tanks connected in series. Water is fed into the last tank (clean water tank) and drained from the first tank (concentrated water tank). The direction of water flow is opposite to that of the plate cleaning process. The cathode plate used in the production of electrolytic zinc enters the countercurrent rinsing device for rinsing, first enters the first stage countercurrent rinsing tank (concentrated water tank), and finally enters the last stage tank (clear water tank) to complete the rinsing process, and the concentration of Zn ²⁺ in the countercurrent rinsing water is About 3000mg/L;

Step 2: Electrodeposition

The concentrated water after rinsing enters the regulating tank, adjusts its water volume and flow rate, and then enters the flat plate electrodeposition device and three-dimensional electrodeposition device to recover metal zinc in the wastewater. The concentration of Zn ²⁺ in the wastewater after electrodeposition is about 100mg/L;

Step Three: Membrane Separation

The temperature of the electrodeposited wastewater is controlled at 20°C to 35°C, and it enters the ultrafiltration membrane system, and 15mg/L potassium sodium tartrate PST is added to remove suspended solids, colloids and other substances in the water. The removal efficiency of zinc ions reaches 99%. Enter the reverse osmosis membrane system, the concentration of Zn ²⁺ in the effluent water of the reverse osmosis membrane system is 0.1-0.5mg/L, the effluent water from the membrane separation system is returned to the countercurrent rinsing device, and the waste water passes through the concentrated solution obtained by the two-stage membrane separation system, and then flows back to the electrodeposition The previous regulating tank then passes through a flat-plate electrodeposition device and a three-dimensional electrodeposition device to recover the metal zinc in the membrane concentrate.

There is only one port for wastewater reuse, which comes from the reverse osmosis system. Heavy metal pollutants can basically be completely recovered and zero discharged, and all the treated wastewater is returned to the countercurrent rinsing device to form a water cycle.

Claims (3)

1. electrolytic zinc rinsing process method of wastewater treatment is characterized in that this method comprises three steps of combined treatment of countercurrent rinsing, galvanic deposit, membrane sepn:

First step: countercurrent rinsing

Countercurrent rinsing is to be composed in series by some tanks, water inlet in the one-level groove (that is, Rinsing Area) in the end, and from first step groove (that is, dense tank) draining, the cleaning process of water (flow) direction and pole plate is in the opposite direction.The negative plate that uses in the electrolytic zinc production technique gets in the countercurrent rinsing device and carries out rinsing, is introduced into first step countercurrent rinsing groove (that is, dense tank), gets into the last step groove (that is, Rinsing Area) of countercurrent rinsing groove at last, accomplishes the rinse cycle of pole plate.

Second step: galvanic deposit

Dense water after the rinsing gets into equalizing tank, regulates its water yield and flow velocity, gets into flat electric deposition device, three-dimensional electric deposition device again, reclaims metallic zinc in the waste water;

Third step: membrane sepn

Waste water after the galvanic deposit; Get into ultrafiltration membrane system, reverse osmosis membrane system successively; Waste water is back to galvanic deposit equalizing tank before through two-stage film separating system gained liquid concentrator, passes through flat electric deposition device, three-dimensional electric deposition device then; Metallic zinc in the reclamation film liquid concentrator, the film separating system effluent recycling is in countercurrent rinsing device;

Membrane sepn refers to that ultrafiltration membrane system separates with reverse osmosis membrane system;

And the waste water recycling water outlet has only 1 mouth, from reverse osmosis system;

Metallic zinc retrieve to come from two parts, a part is the electrodeposition process that derives from waste water behind the countercurrent rinsing, recovery be the metallic zinc in the waste water behind the countercurrent rinsing; A part derives from the waste water after the galvanic deposit in addition, is back to the electrodeposition process behind the electric deposition device through the liquid concentrator that produces behind ultrafiltration membrane system, the reverse osmosis membrane system, recovery be the metallic zinc in the liquid concentrator that the film system produces in this combination treatment method.

2. electrolytic zinc rinsing process method of wastewater treatment as claimed in claim 1; It is characterized in that: the operational condition of said three-dimensional galvanic deposit is: electrode materials is selected graphite anode/stainless steel cathode counter-electrodes for use; Bath voltage is 4.0V-8.0V, and electrolysis time is 60min-90min.

3. electrolytic zinc rinsing process method of wastewater treatment as claimed in claim 1 is characterized in that: said in the reverse osmosis isolation process, the working pressure of use is controlled at 0.7～1.0MPa, Zn in the water outlet ²⁺Concentration is 0.1-0.5mg/L, and the average removal efficient of zine ion is 90%.

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