CN1541757A

CN1541757A - E-Fenton oxidation technique of dirty blocking agent in reverse osmosis concentrating liquid

Info

Publication number: CN1541757A
Application number: CNA2003101084542A
Authority: CN
Inventors: 杨庆峰
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2003-11-06
Filing date: 2003-11-06
Publication date: 2004-11-03
Anticipated expiration: 2023-11-06
Also published as: CN1235668C

Abstract

The electric Fenton oxidation process for processing scale inhibitor in reverse osmosis concentrated liquid adopts anode of iron plate and cathode of porous graphite and ventilated with air pump and processes reverse osmosis concentrated liquid through electrolyzing in stirring, stirring coagulation via adding aluminum sulfate and filtering the coagulated solution. Bivalent iron ion produced intelligent the electric Fenton process is made to react with hydrogen peroxide to produce strong oxidizing free hydroxy radical oxidizing and destructing the scale inhibitor; and the subsequent coagulation separates out scaling salt to lower the scaling trend, so that the concentrated liquid may be utilized as influent water to raise the water recovering rate of reverse osmosis system.

Description

electro-Fenton oxidation method of scale inhibitor in reverse osmosis concentrated solution

The technical field is as follows:

the invention relates to an electro-Fenton (Fenton) oxidation method for scale inhibitors in reverse osmosis concentrated solution, which adopts the electro-Fenton method to reduce the scaling tendency of the reverse osmosis concentrated solution, improve the water recovery rate of a reverse osmosis system and realize the reutilization of concentrated solution resources. Belongs to the technical field of wastewater treatment in environmental science.

Background art:

reverse Osmosis (RO) desalination is widely used in the industrial fields of brackish water and seawater desalination, medicine production, high-purity water in electronic industry, water for beverages, chemical production and the like. Compared with distillation desalination, reverse osmosis has the outstanding advantages of low energy consumption, simple and convenient operation, no discharge of regenerated waste liquid, small system floor area, economic operation cost and the like. With the improvement of membrane preparation technology, the development of energy recovery systems, the improvement of pretreatment technology and the wide applicability of high and low salinity influent water, the reverse osmosis desalination cost is obviously reduced year by year, and the competitiveness of reverse osmosis technology on economy and technology is continuously enhanced, so that the reverse osmosis desalination technology becomes one of the leading high and new technologies in the field of desalination in the 21 st century.

The fouling of membranes is a very troublesome problem in the long run of reverse osmosis systems, and its presence causes a large reduction in the water yield of reverse osmosis units, limiting the wider application of this technology. In order to overcome the scaling problem, the reverse osmosis system generally adds a scale inhibitor into the inlet water during operation so as to maintain the scaling ions at a high supersaturation degree without scaling, thereby improving the recovery rate of water.

After the recovery rate of the reverse osmosis system reaches a certain degree, if the recovery rate is increased, the scale forming ions in the solution are highly supersaturated, the scale forming ions cannot be maintained in a non-scaling state by the scale inhibitor, and the scale forming ions are scaled and separated out on a membrane, so that only concentrated solution is discharged. There will be a discharge of the final concentrate even if concentrate recycling techniques are employed. The final discharge liquid of reverse osmosis is not well utilized at present, and is generally directly discharged, so that the waste of water resources is caused. In fact, the reverse osmosis influent is also highly water-conditioned due to the severe pretreatment. The concentrated solution contains high salt content, especially Ca²⁺、Mg²⁺、HCO₃ ^-The plasma scaling ions have high concentration and a large scaling tendency, i.e., a high LSI (Langeri saturation index), and are prone to scale and cannot be used continuously.

The invention content is as follows:

the invention aims to provide an electro-Fenton oxidation method of a scale inhibitor in a reverse osmosis concentrated solution aiming at the defects of the prior art, which can reduce the scaling tendency of the reverse osmosis concentrated solution and ensure that the reverse osmosis concentrated solution is reused as inlet water.

In order to achieve the purpose, the technical scheme of the invention adopts an electrochemical oxidation method, namely an electro-Fenton method, to treat the reverse osmosis concentrated solution, and ferrous ions (Fe) generated by the electrochemical process are utilized²⁺) And hydrogen peroxide (H)₂O₂) Strong oxidant generated by the reaction, namely hydroxyl radical (OH), is used for oxidizing and destroying the scale inhibitor in the reverse osmosis concentrated solution to destabilize high supersaturation scale-forming ions in the solution, and then, the solution is coagulated to enable the scale-forming salts in the concentrated solution to be like CaCO₃And the scaling tendency of the solution is reduced by precipitation, so that the concentrated solution can be reused as inlet water, and the water recovery rate of the reverse osmosis system is improved.

In the electro-Fenton method, the anode adopts an iron plate, the cathode adopts porous graphite, the cathode is aerated by air pump, and the gas flow is 0.03-0.12m³And h, electrolyzing the reverse osmosis concentrated solution at the electrolysis voltage of 5V for 30-60 minutes under stirring.

During electrolysis, iron is dissolved at the anode to produce Fe²⁺H is produced by the reaction of the formula (1) at the cathode₂O₂Electrically generated Fe²⁺And H₂O₂The Fenton reaction of the formula (2) is carried out, strong oxidation-OH&is generated in situ, the standard electrode potential of the Fenton reaction is 2.8V, and almost all scale inhibitor organic matters can be oxidized.

(1)

(2)

After the electrolytic treatment, the antisludging agent in the concentrated solution is destroyed, and the scaling ions in the highly supersaturated concentrated solution automatically generate crystal particles to be suspended in the solution, at the moment, the concentrated solution becomes turbid. In order to remove the suspended scaling particles efficiently, the invention adopts a coagulation method: namely, after the electrolysis, 200mg/L of aluminum sulfate was added to carry out coagulation. During coagulation, the solution is firstly stirred and coagulated for half a minute at 300 revolutions per minute to fully mix the coagulant and the solution, then the stirring speed is reduced to 50 revolutions per minute, and coagulation is carried out for 5 minutes to fully grow the formed alum floc. After the mixing and coagulation, the solution is filtered to remove the precipitated alum floc, and the treated reverse osmosis concentrated solution is obtained, the scaling tendency of the concentrated solution is greatly reduced, and the concentrated solution can be reused as the inlet water of a reverse osmosis system.

The ion concentration of the treated reverse osmosis concentrated solution is analyzed, and LSI (Langelier Langerel saturation index) value is calculated, and the result shows that the scaling tendency of the solution is greatly reduced and can be reduced to about 0.6 LSI.

The reverse osmosis concentrated solution adopted by the method has high salt concentration and good conductivity, and the energy consumption can be reduced when the reverse osmosis concentrated solution is treated by an electrolytic method. OH generated by electro-Fenton has strong oxidability, the efficiency of treating the scale inhibitor is high, the speed is high, the scale inhibitor in the concentrated solution can be oxidized, and the scaling tendency of the concentrated solution is greatly reduced; automatic generation of Fe during the process²⁺And H₂O₂，No chemical reagent is added, so that the cost is low; the treatment process is environment-friendly, no harmful substances are discharged, the treated concentrated solution can be reused as inlet water, the concentrated solution is recycled, and the water recovery rate of the reverse osmosis system is improved.

Description of the drawings:

FIG. 1 shows the results of the treatment in example 1 of the present invention.

FIG. 2 shows the results of the treatment in example 2 of the present invention.

The specific implementation mode is as follows:

the technical solution of the present invention is further described below with reference to the accompanying drawings and examples.

Example 1

0.72 g NaHCO was weighed₃1.18 g of CaCl₂0.22 g MgSO₄·7H₂O, 0.228 g NaNO₃Placed in 800 ml of distilled water to prepare a concentrated solution having an initial pH of 7.8 and an initial LSI₀Is 1.86. Adding the scale inhibitor, wherein the concentration of the scale inhibitor is 7 mg/L.

The electrolytic anode adopts an iron plate, the cathode adopts porous graphite, and the areas of the two electrodes are both 45cm². The cathode is aerated by air pump with air flow of 0.12m³The electrolysis voltage is 5V, the time is 30 minutes, and the solution is electrolyzed under stirring. And adding 200mg/L aluminum sulfate after electrolysis for coagulation and filtration to obtain a treated concentrated solution. For the coagulation, the coagulation was carried out at 300 rpm for half a minute, followed by 50 rpm for 5 minutes.

electro-Fenton Oxidation of 8 different commercial Scale inhibitors, designated by letters A to H, containing-COOH, -PO₃H₂，-OH，-SO₃H, -COOR and the like.

FIG. 1 shows the results of electro-Fenton treatment of 8 kinds of scale inhibitors, from which LSI of the concentrated solution is shown_fThe reduction to 0.61 indicates that the scale inhibitor is oxidized, and the treatment results of 8 scale inhibitors are basically the same, which indicates that OH-oxidizes the scale inhibitor with high efficiency and no selectivity, so the invention has universality for the treatment of the scale inhibitor.

Example 2

1.712 g NaHCO were weighed₃2.458 g of CaCl₂0.414 g MgSO₄·7H₂O, 0.428 g NaNO₃Placed in 800 ml of distilled water to prepare a concentrated solution having an initial pH of 7.8 and an initial LSI₀Is 2.44. 3 kinds of scale inhibitors A, B and C were added to the solution for electrolysis, and the concentrations were 21 mg/L.

The results of the electrolysis are shown in FIG. 2. As can be seen from the figure, LSI of concentrated solution_fThe LSI value of the scaling tendency is reduced to 0.59 by 76 percent, and the treatment effect is obviousAnd the treatment results of the 3 kinds of scale inhibitors are basically the same. This further shows that the efficiency is high and thereis no selectivity when OH.O. is oxidized scale inhibitor, and the method of the invention has broad applicability.

Example 3

0.72 g NaHCO was weighed₃1.18 g of CaCl₂0.22 g MgSO₄·7H₂O, 0.228 g NaNO₃Placed in 800 ml of distilled water to prepare a concentrated solution having an initial pH of 7.8 and an initial LSI₀Is 1.86. Adding scale inhibitor B, and electrolyzing at 3 concentrations of 7mg/L, 21mg/L and 35mg/L respectively.

The electrolytic anode adopts an iron plate, the cathode adopts porous graphite, and the areas of the two electrodes are both 45cm². The cathode is aerated by air pump, and the air flow is 0.03m³The electrolysis voltage is 5V, the time is 30 minutes, and the solution is electrolyzed under stirring. And adding 200mg/L aluminum sulfate after electrolysis for coagulation and filtration to obtain a treated concentrated solution. For the coagulation, the coagulation was carried out at 300 rpm for half a minute, followed by 50 rpm for 5 minutes.

Calculating to obtain LSI of the treated concentrated solution by solution ion analysis_fThe values were reduced to 0.58, 0.62 and 0.70, respectively, indicating that the fouling tendency of the solution has been greatly reduced. Meanwhile, the change of the concentration of the scale inhibitor has little influence on the effect of electro-Fenton oxidation treatment, which shows that the oxidation capacity of OH&generated in the process is very strong.

Example 4

0.72 g NaHCO was weighed₃1.18 g of CaCl₂0.22 g MgSO₄·7H₂O, 0.228 g NaNO₃Placed in 800 ml of distilled water to prepare a concentrated solution having an initial pH of 7.8 and an initial LSI₀Is 1.86. Adding scale inhibitor C withconcentration of 7 mg/L.

The electrolytic anode adopts an iron plate, the cathode adopts porous graphite, and the areas of the two electrodes are both 45cm². The cathode is aerated by air pump, and the air flow is 0.03m³The electrolysis was carried out with stirring at an electrolysis voltage of 5V for 30 minutes and 60 minutes, respectively. And adding 200mg/L aluminum sulfate after electrolysis for coagulation and filtration to obtain a treated concentrated solution. During coagulationCoagulation was performed at 300 rpm for half a minute, followed by coagulation at 50 rpm for 5 minutes.

Calculating to obtain LSI of the treated concentrated solution by solution ion analysis_fThe reduction to 0.61 and 0.57, respectively, indicates that the fouling tendency of the solution has been greatly reduced. Meanwhile, the effect of the electro-Fenton oxidation treatment is not greatly influenced by the electrolysis time, which shows that the oxidation capability of OH&generated in the process is very strong, and the oxidation reaction of the scale inhibitor is basically completed within 30 minutes.

Claims

1. The electro-Fenton oxidation method of scale inhibitor in reverse osmosis concentrated solution is characterized in that an electro-Fenton method is adopted to oxidize the scale inhibitor containing-COOH and-PO₃H₂，-OH，-SO₃Treating reverse osmosis concentrated solution of scale inhibitor containing H-COOR group with anode made of iron plate, cathode made of porous graphite, air pumped by air pump and gas flow rate of 0.03-0.12m³And h, electrolyzing the reverse osmosis concentrated solution under stirring, wherein the electrolysis voltage is 5V, the time is 30-60 minutes, adding 200mg/L aluminum sulfate for coagulation after theelectrolysis is finished, stirring and coagulating the solution at 300 revolutions per minute, fully mixing the coagulant and the solution, reducing the stirring speed to 50 revolutions per minute for coagulation for 5 minutes, and filtering the solution after the coagulation is finished to obtain the treated reverse osmosis concentrated solution.