Method for treating and recycling high-concentration organic phosphorus chemical wastewater

Abstract

The application relates to a high-concentration organic phosphorus chemical wastewater treatment and resource utilization method, and belongs to the technical field of wastewater treatment. According to weight parts, the method comprises the following steps: adding acid into wastewater to be treated, adjusting the pH value of the wastewater to 2-3, continuously performing condensation treatment on the wastewater, adjusting the temperature of the wastewater to 2-6 DEG C, then separating white suspensions generated in the condensation process to obtain wet solids and first filtrate, adding ferric salt into the wet solids obtained through the screening treatment and stirring, obtaining slurry after sufficient reaction, performing pressure filtration treatment on the slurry to obtain filter cake and second filtrate, sequentially performing drying and calcination treatment on the filter cake to obtain iron phosphate, mixing the first filtrate and the second filtrate to obtain a mixed solution, and performing oxidation treatment on the mixed solution by using ozone. The application can effectively recover phosphorus in wastewater during purification treatment of chemical wastewater containing high-concentration organic phosphorus, effectively reduces the wastewater treatment cost, and avoids waste of phosphorus resources.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater treatment, and particularly relates to a high-concentration organic phosphorus chemical wastewater treatment and resource utilization method. BACKGROUND

[0002] Diphenyl phosphate industry has been plagued by its sewage treatment problem for a long time. Diphenyl phosphate has a large solubility in water. In a medium pH or alkaline environment, the solubility of diphenyl phosphate in water can usually reach more than 60 g / L, and it is very difficult to biodegrade. This characteristic causes the current diphenyl phosphate wastewater to be usually treated into low-concentration wastewater by a method of cooling after pressure reduction distillation, and the concentrated liquid obtained after distillation is disposed as hazardous waste. The treatment cost of this sewage treatment method is extremely high, generally reaching more than 1500 yuan per ton of water treatment (including hazardous waste disposal), which is difficult for enterprises to bear, and a large amount of valuable phosphorus resources in the diphenyl phosphate wastewater cannot be recovered. In view of the above problems, the application provides a high-concentration organic phosphorus chemical wastewater treatment and resource utilization method, which realizes the resource utilization of phosphorus while treating the diphenyl phosphate wastewater at a low cost. SUMMARY

[0003] The purpose of the application is to provide a high-concentration organic phosphorus chemical wastewater treatment and resource utilization method to solve the above problems.

[0004] The application achieves the above purpose by the following technical scheme:

[0005] The application provides a high-concentration organic phosphorus chemical wastewater treatment and resource utilization method, which comprises the following steps:

[0006] Step S1, adding acid to the wastewater to be treated to adjust the pH value of the wastewater to 2-3;

[0007] Step S2, continuing to condense the wastewater to adjust the temperature of the wastewater to 2-6℃, and then separating white suspensions generated in the condensation process to obtain wet solids and a first filtrate;

[0008] Step S3, adding ferric salt to the wet solids obtained by the screening treatment and stirring, fully reacting to obtain a slurry, and performing pressure filtration on the slurry to obtain a filter cake and a second filtrate;

[0009] Step S4, sequentially performing drying and calcination on the filter cake to obtain iron phosphate;

[0010] Step S5, mixing the first filtrate and the second filtrate to obtain a mixed liquid, oxidizing the mixed liquid by ozone, and then adding a coagulant to the oxidized mixed liquid and performing coagulation treatment according to the requirements of conventional coagulation;

[0011] Step S6, the coagulated mixed liquid is precipitated to obtain dischargeable sewage and sludge;

[0012] Step S7, the sludge is dewatered and treated to obtain iron phosphate, and the treatment means is the same as that for the filter cake in step S4.

[0013] As a further optimization scheme of the present application, in step S2, a 150-300 mesh screen is used to separate the white suspended matter in the wastewater by screening.

[0014] As a further optimization scheme of the present application, in step S3, the amount of the added trivalent iron salt is close to the theoretical amount required for the reaction with the diphenyl phosphate in the wet solid, and can be slightly greater or slightly less than the theoretical value.

[0015] As a further optimization scheme of the present application, in step S4, the calcination temperature is 650-800°C.

[0016] As a further optimization scheme of the present application, in step S5, the coagulant is trivalent iron salt.

[0017] The present application has the following beneficial effects:

[0018] The present application can convert most of the diphenyl phosphate in the wastewater into suspended matter by using strong acid acidification and condensation treatment, and then convert the diphenyl phosphate in the suspended matter into iron diphenyl phosphate by using trivalent iron salt, and finally convert the iron diphenyl phosphate into iron phosphate by calcination, thereby purifying the wastewater and recycling the phosphorus resources in the wastewater. For the low-concentration diphenyl phosphate remaining in the water, the present application uses ozone to oxidize the diphenyl phosphate to convert the phosphorus on the benzene ring into orthophosphate (PO4 3- ), and then converts the oxidized diphenyl phosphate into insoluble phosphorus-containing precipitate by coagulation for recycling. The main pollutant in the treated wastewater is COD, which can be directly discharged into the municipal pipe network. Compared with existing wastewater treatment technologies, the wastewater treatment method provided by the present application has a ton of water agent consumption cost of about 120-150 yuan (excluding ozone) and a power consumption cost of about 50-80 yuan (including ozone), which can save more than 80% of the cost. The resource treatment of phosphorus in the wastewater treatment process can achieve a phosphorus recovery rate of more than 84%, which indirectly reduces the wastewater treatment cost. BRIEF DESCRIPTION OF DRAWINGS

[0019] Fig. 1 is a flow chart of organic phosphorus chemical wastewater treatment and resourceization.

[0020] In the figure, S represents solid or semi-solid residue or sludge, and L represents water. DETAILED DESCRIPTION

[0021] Further detailed description of the present application is made below, it is necessary to point out here that the following detailed description is only for further illustrating the present application, and cannot be understood as limiting the protection scope of the present application, and the skilled in the art can make some non-essential improvements and adjustments to the present application according to the above application content.

[0022] The method used in the present application is a conventional method known to those skilled in the art, and the reagents and other materials used are commercially available products unless otherwise specified.

[0023] In this embodiment, the acid added to the wastewater to adjust the pH value is concentrated hydrochloric acid or concentrated nitric acid, and the base is calcium oxide or calcium hydroxide, and the types of the acid and the base are not limited to this;

[0024] The ferric salt is solid ferric chloride (without crystal water);

[0025] In the actual operation process, the process of adding acid to wastewater to adjust the pH value in step S1 affects the theoretical required amount of ferric salt in step S3, resulting in that the theoretical required amount of ferric salt in step S3 cannot be accurately quantified. In the following examples and comparative examples, for the wastewater samples used, the theoretical required amount of ferric salt is calculated as 0.74 grams of ferric chloride per gram of diphenyl phosphate based on the mass of the wastewater, within a certain range, a certain floating can still obtain a better removal effect, and the specific best value still needs to be determined by on-site test.

[0026] Example 1

[0027] A high-concentration organic phosphorus chemical wastewater treatment and resource utilization method, comprising the following steps:

[0028] Step S1, adding acid to the wastewater to be treated to adjust the pH value of the wastewater to 2.5;

[0029] Step S2, condensing the wastewater to adjust the temperature of the wastewater to 4°C, using a 200-mesh screen to separate the white suspended solids in the wastewater by screening, and obtaining wet solids and a first filtrate;

[0030] Step S3, adding ferric salt to the wet solids obtained by screening and stirring, the amount of ferric salt added is 40 g / L, and after sufficient reaction, a slurry is obtained, and the slurry is subjected to pressure filtration to obtain a filter cake and a second filtrate;

[0031] Step S4, sequentially drying and calcining the filter cake to obtain iron phosphate, wherein the calcination temperature is 800°C;

[0032] Step S5, mixing the primary filtrate and the secondary filtrate to obtain a mixed solution, and performing an oxidation treatment on the mixed solution by using ozone, and then adding a ferric salt into the mixed solution after the oxidation treatment and performing a coagulation treatment according to a conventional coagulation requirement;

[0033] Step S6, precipitating the mixed solution after the coagulation to obtain dischargeable sewage and sludge;

[0034] Step S7, performing a dewatering treatment on the sludge, and performing a treatment on the sludge after the dewatering to obtain iron phosphate, and the treatment means is the same as the treatment means of the filter cake in Step S4.

[0035] 1. Influence of pH value of wastewater on wastewater treatment effect

[0036] On the basis of Example 1, a test is performed by adjusting a target value when the pH value of the wastewater is adjusted or omitting the step of adjusting the pH value of the wastewater, and a comparative test is performed under the condition that the pH value of the wastewater is not adjusted, and the test conditions and results are shown in the following table:

[0037]

[0038]

[0039] The test results show that a suitable strong acid environment is conducive to achieving better wastewater purification effect and better phosphorus recovery effect, because the solubility of diphenyl phosphate in a strong acid environment will decrease, which is conducive to the conversion of diphenyl phosphate in the wastewater into insoluble particulate white suspensions. However, when the acidity is too strong, the phosphorus recovery rate decreases, and the reason is unknown. If the pH value is not adjusted, there is also a certain amount of suspensions in the wastewater, but the filter residue can be ignored, so the recovery rate is considered to be 0.

[0040] 2. Influence of temperature of wastewater on wastewater treatment effect

[0041] On the basis of Example 1, a test is performed by adjusting only a target temperature when the wastewater is condensed or omitting the step of condensing the wastewater, and a comparative test is performed under the condition that the wastewater is not condensed, and the test conditions and results are shown in the following table:

[0042]

[0043] The test results show that a low-temperature environment is conducive to achieving better wastewater purification effect and better phosphorus recovery effect, because the solubility of diphenyl phosphate in a low-temperature environment will decrease, which is conducive to the conversion of diphenyl phosphate in the wastewater into particulate white suspensions.

[0044] 3. Influence of addition amount of ferric salt on wastewater treatment effect

[0045] On the basis of Example 1, only the amount of ferric salt added in step S3 is adjusted to carry out the test, and the test conditions and results are shown in the following table:

[0046]

[0047]

[0048] Example 8 in the table is an experimental group containing multiple tests.

[0049] The test results show that the amount of ferric salt needs to be controlled within a suitable range, and too much or too little will affect the phosphorus recovery rate. As can be seen from the above data, for the wastewater sample used (the theoretical required amount of ferric salt is 46 g / L), when the amount of ferric salt added is in the range of 25-60 g / L, a higher phosphorus recovery rate can be achieved, especially when the amount of ferric salt added is in the range of 40-50 g / L, the phosphorus recovery rate can reach more than 84%. In summary, when the amount of ferric salt added is equivalent to the theoretical required amount for the reaction of diphenyl phosphate in wet solids, the best phosphorus recovery rate can be achieved.

[0050] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application.

Claims

1. A method for treating and recycling high-concentration organic phosphorus chemical wastewater, characterized in that, The method comprises the following steps: Step S1, adding acid to the wastewater containing diphenyl phosphate to be treated, and adjusting the pH value of the wastewater to 2-3; Step S2, continuing to condense the wastewater, adjusting the temperature of the wastewater to 2-6℃, and then separating white suspensions generated in the condensation process to obtain wet solids and a first filtrate; Step S3, adding a ferric salt to the wet solids and stirring, fully reacting to obtain a slurry, and then performing pressure filtration on the slurry to obtain a filter cake and a second filtrate; Step S4, sequentially drying and calcining the filter cake to obtain ferric phosphate; Step S5, mixing the first filtrate and the second filtrate to obtain a mixed solution, oxidizing the mixed solution by using ozone, and then adding a ferric salt to the oxidized mixed solution and performing coagulation treatment according to the requirements of conventional coagulation; Step S6, precipitating the coagulated mixed solution to obtain dischargeable wastewater and sludge; Step S7, dehydrating the sludge, and treating the dehydrated sludge to obtain ferric phosphate, and the treatment method is the same as the treatment method of the filter cake in step S4.

2. The method according to claim 1, wherein the method is characterized by, In step S2, a 150-300 mesh screen is used to separate the white suspensions in the wastewater by screening.

3. The method according to claim 2, wherein the method is characterized by, In step S3, the amount of the ferric salt added is close to the theoretical amount required for the reaction of diphenyl phosphate in the wet solids.

4. The method according to claim 1, wherein the method is characterized by, In step S4, the calcination temperature is 650-800℃.

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