Method for treating wastewater by using multifunctional reagent

Abstract

The invention relates to the field of wastewater treatment, and discloses a method for treating wastewater by using a multifunctional reagent. The multifunctional reagent comprises ammonium bicarbonate, and the method comprises the following steps: (1) adding an optional multifunctional reagent into wastewater to be treated, mixing with a Fenton reagent, adding the multifunctional reagent after reaction, standing and filtering; (2) adjusting the pH value of the filtrate to 4-8, adding a flocculant and a surfactant, and adding an optional multifunctional reagent in the flocculation process; after flocculation, carrying out air flotation separation to obtain clarified wastewater; and (3) adding an optional multifunctional reagent into the clarified wastewater obtained in the step (2), and carrying out oil-water separation. The method solves the problems that emulsified oil and dissolved oil in the wastewater are difficult to treat, COD is difficult to degrade and the like, realizes efficient removal of organic matters, suspended solids and heavy metals in the wastewater, has technical feasibility, economical efficiency and environmental friendliness, and provides a reliable solution for wastewater treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wastewater treatment, in particular to a method for treating wastewater by using a multifunctional reagent. BACKGROUND

[0002] Rare earth is an important strategic resource, which is widely used in electronic, new energy, aerospace and other high-tech fields. In the process of rare earth extraction and separation, saponification process is the key link to adjust the pH value of aqueous phase and realize efficient separation of rare earth elements. However, this process will produce a large amount of saponification wastewater with complex components. Such wastewater has the characteristics of complex pollutant composition, high COD value, high oil content and poor biodegradability, and belongs to the category of refractory industrial wastewater. If such wastewater is discharged directly without effective treatment, it will not only cause serious pollution to soil and water, but also harm human health through the food chain.

[0003] At present, the treatment technologies for rare earth extraction saponification wastewater mainly include chemical precipitation method, biological treatment method, membrane separation method, etc. However, these traditional methods generally have the problems of low treatment efficiency, high operation cost and secondary pollution risk in practical application.

[0004] In recent years, advanced oxidation technology (such as Fenton oxidation) has shown significant advantages in the field of organic wastewater treatment. Through the reaction of ferrous ions and hydrogen peroxide, strong oxidizing hydroxyl radicals (·OH) can be generated, which can effectively destroy the molecular structure of refractory organic matter. However, when single Fenton oxidation is used to treat rare earth saponification wastewater, a large amount of sulfuric acid needs to be consumed to adjust the pH value during the reaction process, a large amount of iron sludge is generated, and it is difficult to completely mineralize organic matter. The method for treating rare earth smelting wastewater by using pure Fenton process disclosed in Chinese patent CN102531199A has a COD removal rate of 60-70%, but has the problems of large amount of iron sludge (about 3-5% of the treated water), high H2O2 dosage (molar ratio H2O2 / COD > 3), etc.

[0005] In summary, the existing single treatment technology cannot meet the requirements of efficient, low-cost and stable treatment of rare earth extraction saponification wastewater. Therefore, it is urgent to develop an integrated treatment technology with reasonable process, stable treatment effect and controllable operation cost to meet the urgent needs of sustainable development and environmental protection of the rare earth industry. SUMMARY

[0006] In order to overcome the above technical problems, the present application provides a method for treating wastewater by using a multifunctional reagent, which includes ammonium bicarbonate. This method solves the problems of difficult treatment of emulsified oil and dissolved oil in wastewater and difficult degradation of COD, realizes efficient removal of organic matter, suspended solids and heavy metals in wastewater, and has technical feasibility, economy and environmental friendliness, providing a reliable solution for wastewater treatment.

[0007] The application first creatively selects ammonium bicarbonate (NH4HCO3) as a multifunctional reagent in wastewater treatment, realizes four-in-one of neutralization, flocculation, heavy metal removal, and resource utilization, avoids introducing new impurities, and improves production efficiency and reduces production cost.

[0008] To achieve the above-mentioned purpose, the application provides a method for treating wastewater by using a multifunctional reagent, the multifunctional reagent comprising ammonium bicarbonate, and the method is performed according to the following steps:

[0009] (1) After adding the multifunctional reagent to the wastewater to be treated, the wastewater is mixed with Fenton reagent, the multifunctional reagent is added after reaction, and then the wastewater is filtered after standing;

[0010] (2) The pH value of the filtrate is adjusted to 4-8, a flocculating agent and a surfactant are added, and the multifunctional reagent is optionally added during the flocculation process; and after flocculation, the clarified wastewater is obtained through air flotation separation;

[0011] (3) The multifunctional reagent is added to the clarified wastewater of step (2) and oil-water separation is performed.

[0012] Compared with the prior art, the application has at least the following beneficial effects:

[0013] (1) The steps of the application can be independently regulated, which is convenient for upgrading the existing wastewater treatment facilities, suitable for application in small and medium-sized enterprises, and produces less sludge compared with the single chemical precipitation method, avoids the generation of a large amount of hazardous waste, has no secondary pollution, and reduces disposal cost; and the method has strong process adaptability, low cost, realizes economy and sustainability.

[0014] (2) The application first creatively selects ammonium bicarbonate (NH4HCO3) as a multifunctional reagent in wastewater treatment, which can adjust the pH value, degrade COD, and simultaneously cooperate with demulsification, and create conditions for heavy metal precipitation. Four-in-one of neutralization, flocculation, heavy metal removal, and resource utilization is realized, and the introduction of new impurities when adding NaOH or Ca(OH)2 is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a process flow chart for treating wastewater by using a multifunctional reagent in an embodiment of the application;

[0016] Figure 2 is an influence of different H2O2 dosages on the COD content and the concentrations of P and rare earth ions in the filtrate after Fenton reaction in an embodiment of the application;

[0017] Figure 3 is an influence of different ferrous sulfate heptahydrate dosages on the COD content and the concentrations of P and rare earth ions in the filtrate after Fenton reaction in an embodiment of the application;

[0018] Figure 4 Effect of different pH values before Fenton reaction on COD content and P, rare earth ion concentration in filtrate after Fenton reaction in an embodiment of the present application;

[0019] Figure 5 Effect of different reaction times on COD content and P, rare earth ion concentration in filtrate after Fenton reaction in an embodiment of the present application;

[0020] Figure 6 Effect of different pH values before Fenton reaction on COD content and P, rare earth ion concentration in clarified wastewater after air floatation separation in an embodiment of the present application;

[0021] Figure 7 Effect of different PAC dosages on COD content and P, rare earth ion concentration in clarified wastewater after air floatation separation in an embodiment of the present application;

[0022] Figure 8 Effect of different PAM dosages on COD content and P, rare earth ion concentration in clarified wastewater after air floatation separation in an embodiment of the present application;

[0023] Figure 9 Effect of different air floatation times on COD content and P, rare earth ion concentration in clarified wastewater after air floatation separation and removal rate comparison in an embodiment of the present application;

[0024] Figure 10 Effect of different air floatation flow rates on COD content and P, rare earth ion concentration in clarified wastewater after air floatation separation and removal rate comparison in an embodiment of the present application;

[0025] Figure 11 Infrared spectrum analysis of different types of activated carbon in an embodiment of the present application;

[0026] Figure 12 Comparison of COD removal rates in supernatant after oil-water separation by different types of activated carbon and different activated carbon dosages in an embodiment of the present application;

[0027] Figure 13 Comparison of COD concentration in supernatant after oil-water separation by adjusting different pH values of clarified wastewater and removal rate comparison in an embodiment of the present application;

[0028] Figure 14 Effect of different initial COD concentrations on adsorption effect in an embodiment of the present application;

[0029] Figure 15 Adsorption isotherm of activated carbon adsorbing COD in an embodiment of the present application;

[0030] Figure 16 This is a linear fit of the Langmuir isotherm model for activated carbon adsorption in one embodiment of the present invention;

[0031] Figure 17 This is a linear fit of the Freundlich isotherm model for activated carbon adsorption in one embodiment of the present invention;

[0032] Figure 18 This is an embodiment of the invention showing the effect of different adsorption times on the COD concentration in the supernatant after oil-water separation;

[0033] Figure 19 This is a kinetic curve of activated carbon adsorption of COD in one embodiment of the present invention;

[0034] Figure 20 This is a linear fit of the pseudo-first-order kinetic model of activated carbon adsorption in one embodiment of the present invention;

[0035] Figure 21 This is a linear fit of the pseudo-second-order kinetic model of activated carbon adsorption in one embodiment of the present invention;

[0036] Figure 22 This invention compares the effects of replacing ammonium bicarbonate with sodium hydroxide on the COD content, P, and RE concentrations and their removal rates in the supernatant after oil-water separation in one embodiment of the invention. Detailed Implementation

[0037] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0038] This invention provides a method for treating wastewater using a multifunctional reagent, wherein the multifunctional reagent includes ammonium bicarbonate, and the method is carried out according to the following steps:

[0039] (1) Add an optional multifunctional reagent to the wastewater to be treated and mix it with Fenton's reagent. After the reaction, add the multifunctional reagent, let it stand and filter.

[0040] (2) Adjust the pH of the filtrate to 4-8, add flocculant and surfactant, and optionally add a multifunctional reagent during the flocculation process; after flocculation, perform air flotation separation to obtain clarified wastewater;

[0041] (3) Add an optional multifunctional reagent to the clarified wastewater described in step (2) and perform oil-water separation.

[0042] In the present application, each step can be independently regulated, facilitating the upgrading of existing wastewater treatment facilities, suitable for small and medium-sized enterprises, and producing less sludge than single chemical precipitation, avoiding the generation of a large amount of hazardous waste, no secondary pollution, and reducing disposal costs. The present application first creatively selects ammonium bicarbonate (NH4HCO3) as a multifunctional reagent in wastewater treatment, which can adjust the pH value, degrade COD, and simultaneously break emulsion, and create conditions for heavy metal precipitation. Neutralization, flocculation, heavy metal removal, and resource utilization are achieved in one step, avoiding the introduction of new impurities when adding NaOH or Ca(OH)2.

[0043] In the present application, the mixing method of the wastewater system to be treated and the Fenton reagent in step (1) has no special requirements, which can be simultaneous feeding and mixing, or sequential feeding and mixing, and the mixing of the wastewater to be treated and the Fenton reagent is carried out under continuous stirring for Fenton reaction. The following exemplary description does not limit the scope of the present application.

[0044] In one embodiment of the present application, after adding the optional multifunctional reagent to the wastewater to be treated, the Fenton reagent is slowly added to the system under stirring for Fenton reaction. Generally, the stirring speed is 550 r / min, and the Fenton reagent addition speed is adjusted according to the actual situation, which is not described herein as long as the purpose of the present application can be achieved.

[0045] In one embodiment of the present application, the Fenton reaction conditions include a reaction time of 0.5-2 h.

[0046] According to the present application, there is no special requirement for the source of the wastewater to be treated, and the following exemplary description does not limit the scope of the present application. In one embodiment of the present application, the wastewater to be treated is phosphorus-containing wastewater, preferably rare earth extraction saponification wastewater. The present application can be applied to rare earth extraction saponification wastewater to recover rare earth and reduce resource waste; and the method has strong process adaptability, low cost, and realizes economy and sustainability.

[0047] According to the present application, the pH system of the wastewater to be treated generally needs to be regulated. Too high or too low pH value will affect the removal effect of the target pollutants. In neutral or alkaline conditions, Fe 2+ cannot induce H2O2 to produce ·OH. Therefore, in order to efficiently and continuously degrade organic pollutants, the reaction needs to be controlled under acidic conditions, and the following exemplary description does not limit the scope of the present application. According to one embodiment of the present application, the optional multifunctional reagent is added to the wastewater to be treated to adjust the pH value to 2.5-5, preferably 3-4, and more preferably 3.

[0048] According to the present invention, after the wastewater to be treated is fully reacted with Fenton's reagent, neutralization and precipitation are generally required. When the pH of the wastewater system is adjusted to approximately 7, the addition of the multifunctional reagent can be stopped, completing the precipitation and removal of iron ions, COD (Chemical Oxygen Demand), and other organic matter in the wastewater system. The pH value during neutralization and precipitation needs to be adjusted adaptively according to the iron ion content in the supernatant of the wastewater system. The following illustrative description does not limit the scope of the present invention. According to one embodiment of the present invention, after the reaction, the multifunctional reagent is added to adjust the iron ion concentration in the supernatant to a range of 0.3-0.5 mg / L. At this time, the supernatant in the wastewater system is colorless and transparent, with no obvious yellow color due to iron ions in the solution; and the lower layer, due to Fe... 3+ Hydrolysis produces ferric hydroxide (Fe(OH)3) precipitate, which is reddish-brown, indicating the completion of the precipitation process.

[0049] According to the present invention, there are no special requirements for the standing and filtering methods. They can be adjusted according to the actual situation. The present invention will not elaborate on these methods here, as long as the purpose of the present invention can be achieved.

[0050] According to the present invention, there are no special requirements for the selection of Fenton's reagent. The following illustrative description is not intended to limit the scope of the present invention. According to one embodiment of the present invention, in step (1), Fenton's reagent comprises ferrous sulfate heptahydrate and 30% hydrogen peroxide.

[0051] According to the present invention, there are no special requirements for the amount of Fenton's reagent used. The following illustrative description is not intended to limit the scope of the present invention.

[0052] According to one embodiment of the present invention, Fenton's reagent is added such that the amount of ferrous sulfate heptahydrate added is 5-40 g / L, preferably 15-25 g / L, and more preferably 18-22 g / L.

[0053] According to one embodiment of the present invention, Fenton's reagent is added such that the amount of 30% hydrogen peroxide added is 10-100 mL / L, preferably 40-80 mL / L, and more preferably 50-70 mL / L.

[0054] In this invention, the pH value of the filtrate needs to be adjusted before and during flocculation. If the pH value is too low, hydrolysis will be incomplete, resulting in the formation of Al. 3+ and Al(OH)2 + The flocculation effect is poor; moreover, the flocs are small and their floating effect is not good. When the pH is too high, Al(OH)4 is generated. - Negatively charged ions reduce the flocculation effect; furthermore, the flocs may redisperse, affecting the flotation effect. This invention offers a wide range of options for specific adjustment methods and pH values; the following illustrative descriptions are not intended to limit the scope of this invention.

[0055] According to an embodiment of the present application, in step (2), the pH value of the filtrate is adjusted to 5-7.

[0056] According to an embodiment of the present application, in step (2), the pH value is adjusted to 6-7 by adding an optional multifunctional agent.

[0057] With the above embodiment, the aluminum ions can effectively adsorb the suspended matter and colloidal particles to form larger flocs.

[0058] In an embodiment of the present application, the flocculant comprises polyaluminum chloride (PAC), which is usually prepared into a solution with a mass fraction of 2.5%-5%. The concentration of the prepared PAC solution should not be too high, otherwise the flocculation effect will be reduced due to local excess. For example, the PAC is dissolved into a solution with a mass fraction of 2.5% before being added.

[0059] In an embodiment of the present application, the surfactant comprises polyacrylamide (PAM), which is usually prepared into a solution with a mass fraction of 0.1%-0.5%. The concentration of the prepared PAM solution should not be too high, otherwise the solution viscosity will be too large, making it difficult to add and disperse. For example, the PAM is dissolved into a solution with a mass fraction of 0.5% before being added.

[0060] According to the present application, the addition amount of the flocculant can be selected in a wide range, which is exemplarily described below without limiting the scope of the present application. According to an embodiment of the present application, the flocculant is added so that the addition amount of polyaluminum chloride is 100-400 mg / L, and more preferably 180-220 mg / L.

[0061] According to the present application, the addition amount of the surfactant can be selected in a wide range, which is exemplarily described below without limiting the scope of the present application. According to an embodiment of the present application, the surfactant is added so that the addition amount of polyacrylamide is 20-100 mg / L, and more preferably 30-50 mg / L.

[0062] In an embodiment of the present application, in step (2), the flocculant is added first and then the surfactant. Generally, the addition sequence is to add PAC first and then PAM, so as to ensure that the flocs are fully formed before being strengthened by PAM. After adding an appropriate amount of the flocculant PAC into the filtrate, the polyaluminum chloride is uniformly dispersed in the water, ensuring that the flocculant fully contacts with the pollutants. Then, an appropriate amount of PAM is added to promote the collision of the destabilized particles and promote the slow growth of the flocs to form larger flocs.

[0063] According to the present application, the conditions for flocculation have no special requirements. Generally, in the flocculation air floatation experiment using PAC as flocculant and PAM as surfactant, polyaluminum chloride solution and polyacrylamide solution instead of solid are usually used. The solution can be quickly and uniformly dispersed in water, ensuring the flocculant fully contacts with the suspended matter and promoting flocculation. The solution is also convenient for controlling the dosage, avoiding local excess or deficiency. Therefore, in one embodiment of the present application, the conditions for flocculation include: stirring treatment during the flocculation process.

[0064] According to one embodiment of the present application, the stirring speed is 200-550 r / min, preferably the stirring speed is 450-550 r / min when the flocculant is added or the stirring speed is 200-300 r / min when the surfactant is added.

[0065] According to one embodiment of the present application, the stirring time is 2-20 min, preferably the stirring time is 1-4 min when the flocculant is added or the stirring time is 1-16 min when the surfactant is added.

[0066] The above exemplary descriptions do not limit the scope of the present application.

[0067] In the present application, the air floatation separation using the air floatation device is taken as an exemplary description. After flocculation, the water sample is transferred to the air floatation device, and the foam floc is floated to the surface of the liquid. The floating sludge is separated by scraping. The clarified wastewater is collected from the water outlet at the bottom of the air floatation tank.

[0068] According to the present application, the conditions for air floatation separation have no special requirements. The following exemplary descriptions do not limit the scope of the present application.

[0069] According to one embodiment of the present application, the conditions for air floatation separation include: the time is 5-40 min, preferably 10-20 min.

[0070] According to one embodiment of the present application, the conditions for air floatation separation include: the gas-liquid ratio is 0.02-0.15:1, preferably 0.06-0.1:1.

[0071] According to the present application, the optional multifunctional agent added in step (3) is used to adjust the pH value of the system. The adjustment range is wide, and the following exemplary descriptions do not limit the scope of the present application. According to one embodiment of the present application, in step (3), the optional multifunctional agent is added to adjust the pH value to 6-7.

[0072] According to the present application, the mode of oil-water separation has no special requirements. Generally, the adsorbent is used for adsorption.

[0073] According to the present application, the type of adsorbent has no special requirements. Generally, the adsorbent includes unmodified activated carbon and / or alkali-modified activated carbon.

[0074] According to the present application, the adsorbent addition amount can be selected in a wide range, and generally, the adsorbent addition amount is 1-6 g / L.

[0075] According to the present application, the adsorbent adsorption time can be selected in a wide range, and generally, the adsorption time is 0.25-2.5 h.

[0076] In the present application, the wastewater is first subjected to oxidation pre-removal of impurities by using the above-mentioned embodiments, and then the filtrate is subjected to flocculation and air floatation separation, and the remaining oil content in the clarified wastewater after air floatation separation is further removed by oil-water separation, so that the water can meet the requirements of recycling or discharge.

[0077] In one embodiment of the present application, the present application is described in combination with the accompanying drawings:

[0078] As shown in Figure 1 ,

[0079] S1, adding an optional multifunctional agent to regulate the initial pH value of the wastewater to be treated, adding appropriate Fenton reagent (ferrous sulfate heptahydrate and 30% hydrogen peroxide) to the wastewater, stirring and reacting, and then adding appropriate multifunctional agent to adjust the pH value and neutralize the precipitate, and then filtering after standing;

[0080] S2, continue to regulate the pH value of the filtrate to an appropriate range, add appropriate flocculant and surfactant to the filtrate for flocculation, and then transfer the water sample to an air floatation device for air floatation separation, and then make the foam flocculation float to the surface of the liquid by scraping the slag, and then collect the clarified wastewater from the water outlet at the bottom of the air floatation tank; the flocculant includes polyaluminum chloride, and the surfactant includes polyacrylamide;

[0081] S3, the remaining oil content in the clarified wastewater after air floatation treatment is further removed by an adsorbent; the adsorbent includes at least one of unmodified and alkali-modified activated carbon.

[0082] The optimal implementation conditions of the present application will be explored through the following exploration examples, and the experimental effects of the present application will be compared through the examples and comparative examples. If no specific technology or condition is specified, the technology or condition described in the literature in the field or according to the product manual is used.

[0083] In the following exploration examples and comparative examples:

[0084] The ammonium bicarbonate reagent is 1066-33-7 type produced by Xilong Chemical Co., Ltd.;

[0085] The ferrous sulfate heptahydrate reagent is 7782-63-0 type produced by Xilong Chemical Co., Ltd.

[0086] The hydrogen peroxide reagent is a 7722-84-1 type produced by Xilong Chemical Co., Ltd.;

[0087] The sulfuric acid reagent is a 7664-93-9 type produced by Xilong Chemical Co., Ltd.;

[0088] The polyaluminum chloride reagent (PAC, mass fraction 2.5%, density about 1 g / mL) is a 1237-41-9 type produced by Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0089] The polyacrylamide reagent (PAM, mass fraction 0.5%, density about 1 g / mL) is a 9003-05-8 type produced by Shanghai Shanpu Chemical Co., Ltd.;

[0090] The air floatation device is a JHY type produced by Shandong Jinhao Environmental Protection Technology Co., Ltd.; when the water sample is transferred to the air floatation device for air floatation separation, a certain amount of flocculated wastewater is added to the foam separation column, then gas is introduced, the liquid volume is fixed at 250 ml, the pH of the solution system, the addition amount of flocculant and surfactant, the gas flow rate, and the air floatation time are changed for testing;

[0091] The COD water quality rapid tester is a TR 6900 type produced by Shenzhen Tongao Technology Co., Ltd.;

[0092] The ICP-MS (inductively coupled plasma mass spectrometer) is an iCAP RQ type produced by Thermo Fisher Scientific;

[0093] The removal rate calculation formula is:

[0094] Removal rate (%) = [(C0-C1) / C0]x100%;

[0095] Wherein,

[0096] C0: the initial concentration of the target pollutant in the wastewater before treatment (mg / L, ppm, etc.);

[0097] C1: the residual concentration of the target pollutant in the effluent after treatment (mg / L, ppm, etc.).

[0098] Preparation of modified activated carbon:

[0099] The unmodified activated carbon (64365-11-3 type produced by Xilong Chemical Co., Ltd.) sample is placed in an 80°C oven for drying to constant weight, and is marked as C1;

[0100] 2 mol / L NaOH (1310-73-2 type produced by Xilong Chemical Co., Ltd.) is selected as the modification reagent;

[0101] Take 4g C1 and place it in a 250mL conical flask, add 200mL of 2mol / L NaOH modified reagent, stir at a speed of 550r / min for 8h at room temperature; centrifuge the suspension at a speed of 5000r / min for 5min in a centrifuge, collect the lower layer carbon material, wash several times with deionized water until the pH is neutral; dry in an oven at 80℃ to obtain modified carbon material C2, store for later use;

[0102] The adsorption experiment of activated carbon is carried out at 25℃, 50mL of air floatation treated wastewater is taken in a 250mL conical flask, activated carbon adsorbent is added, and the flask is sealed with a preservative film; the adsorption experiment is carried out by oscillating at a stirring speed of 250r / min for a certain time; after the adsorption is completed, the sample is filtered with an organic filter membrane (13mm, 0.22μm) after standing for a period of time, and the purified wastewater is obtained, i.e. the adsorption process is completed.

[0103] Exploration example 1

[0104] The wastewater to be treated is rare earth extraction saponification wastewater (pH is 0.830, RE concentration is 690mg / L, COD concentration is 722mg / L, and P concentration is 23.7mg / L) from the saponification extraction workshop of Dinhua New Material Resources Co., Ltd., Dinning.

[0105] Y1, 6 groups of 50mL wastewater to be treated are taken in 6 100mL beakers, ammonium bicarbonate is slowly added to the beakers to adjust the pH value to 3, the ferrous sulfate heptahydrate dosage is fixed at 1.0g, the Fenton reaction time is fixed at 1h, and the 30% hydrogen peroxide dosage is 0.5mL, 1mL, 2mL, 3mL, 4mL, 5mL, respectively, and the COD in the wastewater to be treated is oxidized and degraded; after the reaction is completed, ammonium bicarbonate is slowly added to the beakers to adjust the pH value to colorless and transparent supernatant without obvious yellow color of iron ions in the solution. After standing and filtering, the COD content in each filtrate is measured by using a COD water quality rapid determination instrument, and the P and rare earth ion (RE 3+ ) concentrations in each filtrate are measured by using ICP-MS, and the COD, P removal rates, and rare earth ion precipitation rates are calculated as Figure 2 shown.

[0106] Y2, take 6 groups of 50 mL wastewater to be treated in 6 100 mL beakers, slowly add ammonium bicarbonate to the beaker to adjust the pH value to 3, the fixed 30% hydrogen peroxide dosage is 3 mL, the fixed Fenton reaction time is 1 h, the ferrous sulfate heptahydrate dosages are 0.25 g, 0.5 g, 0.75 g, 1.0 g, 1.5 g, 2.0 g, and the COD in the wastewater to be treated is oxidized and degraded; after the reaction is completed, slowly add ammonium bicarbonate to the beaker to adjust the pH value to the supernatant colorless transparent, no obvious yellow color of iron ions in the solution. Stand for filtration, use COD water quality rapid determination instrument to determine the content of COD in each filtrate, use ICP-MS to determine the concentration of P and rare earth ions in each filtrate, calculate the COD, P removal rate, and rare earth ion precipitation rate as shown in Figure 3 ;

[0107] Y3, take 5 groups of 50 mL wastewater to be treated in 5 100 mL beakers, fix the 30% hydrogen peroxide dosage to 3 mL, fix the ferrous sulfate heptahydrate dosage to 1.0 g, fix the Fenton reaction time to 1 h, slowly add ammonium bicarbonate to the beaker, adjust the pH of each beaker to 2.5, 3, 3.5, 4, 5, and the COD in the wastewater to be treated is oxidized and degraded; after the reaction is completed, slowly add ammonium bicarbonate to the beaker to adjust the pH value to the supernatant colorless transparent, no obvious yellow color of iron ions in the solution. Stand for filtration, use COD water quality rapid determination instrument to determine the content of COD in each filtrate, use ICP-MS to determine the concentration of P and rare earth ions in each filtrate, calculate the COD, P removal rate, and rare earth ion precipitation rate as shown in Figure 4 ;

[0108] Y4, take 4 groups of 50 mL wastewater to be treated in 4 100 mL beakers, slowly add ammonium bicarbonate to the beaker to adjust the pH value to 3, fix the 30% hydrogen peroxide dosage to 3 mL, fix the ferrous sulfate heptahydrate dosage to 1.0 g, and the Fenton reaction time in each beaker is 0.5 h, 1 h, 1.5 h, and 2 h, and the COD in the wastewater to be treated is oxidized and degraded; after the reaction is completed, slowly add ammonium bicarbonate to the beaker to adjust the pH value to the supernatant colorless transparent, no obvious yellow color of iron ions in the solution. Stand for filtration, use COD water quality rapid determination instrument to determine the content of COD in each filtrate, use ICP-MS to determine the concentration of P and rare earth ions in each filtrate, calculate the COD, P removal rate, and rare earth ion precipitation rate as shown in Figure 5 ;

[0109] Exploration analysis: from Figures 2-5As can be seen, under the conditions of fixing the 30% hydrogen peroxide dosage at 3 mL, fixing the ferrous sulfate heptahydrate dosage at 1.0 g, fixing the pH value of the solution system at 3, and fixing the Fenton reaction time at 1 h, the COD removal rate in the filtrate reaches 47.46%, and the COD concentration drops to 403 mg / L; the P removal rate reaches 76.10%, and the P concentration drops to 5.7 mg / L; the rare earth ion precipitation rate reaches 94.12%, and the rare earth ion concentration drops to 40 mg / L.

[0110] Exploration Example 2

[0111] The filtrate after standing and filtration under the conditions of fixing the 30% hydrogen peroxide dosage at 3 mL, fixing the ferrous sulfate heptahydrate dosage at 1.0 g, fixing the pH value of the solution system at 3, and fixing the Fenton reaction time at 1 h in Exploration Example 1 is taken as the pre-impurity removal wastewater.

[0112] Y1, 5 groups of 250 mL pre-impurity removal wastewater are taken in 5 500 mL beakers, a small amount of 1:1 sulfuric acid is slowly added to the beakers, and the pH values of the pre-impurity removal wastewater systems are adjusted to 5, 5.5, 6, 6, and 6, respectively; the pH values of the last two beakers are further adjusted to 6.5 and 7, respectively, by adding ammonium bicarbonate; PAC solution (2.5 wt%) is added to the beakers, and the concentration of PAC is fixed at 200 mg / L; the rotation speed is kept at 550 r / min, and the PAC is quickly stirred for 2 min to make the polyaluminum chloride uniformly dispersed in the water; then PAM solution (0.5 wt%) is added to the beakers to make the concentration of PAM 40 mg / L; the rotation speed is kept at 200 r / min, and the PAM is slowly stirred for 15 min to promote the slow growth of the flocs, complete the flocculation process, and add ammonium bicarbonate during the flocculation process to adjust the pH value to about 6.5; then the water samples are transferred to a flotation device for flotation test, the flotation time is fixed at 15 min, and the flotation flow rate is fixed at 80 mL / h; the lower water phase after the flotation experiment is taken, the COD content in each lower water phase is determined using a COD water quality rapid determination instrument, the concentrations of P and rare earth ions in each lower water phase are determined using ICP-MS, and the COD, P, and rare earth ion removal rates are calculated as shown in Table 1. Figure 6

[0113] ​Y2, 6 groups of 250 mL pre-impurity removal wastewater were taken in 6 500 mL beakers, a small amount of 1:1 sulfuric acid was slowly added to the beaker, when the pH value of the wastewater system was adjusted to 6.0, the acid was stopped, and then the pH value was continuously adjusted to 6.5 by adding ammonium bicarbonate. PAC solution (2.5wt%) was first added to the beaker, and the concentration of PAC was fixed at 200 mg / L. The stirring speed was kept at 550 r / min, and the stirring time was 2 min. Then the addition amount of PAM solution (0.5wt%) was changed so that the concentration of PAM was 20 mg / L, 40 mg / L, 60 mg / L, 80 mg / L and 100 mg / L. The stirring speed was kept at 200 r / min, and the stirring time was 15 min to promote the slow growth of the flocs and complete the flocculation process. Ammonium bicarbonate was added during the flocculation process, and the pH value was adjusted to about 6.5. Then the water sample was transferred to the air flotation device for air flotation test, and the air flotation time was fixed at 15 min and the air flotation flow rate was fixed at 80 mL / h. The lower water phase after air flotation test was taken, and the COD content in each lower water phase was determined by using the COD water quality rapid determination instrument. The concentrations of P and rare earth ions in each lower water phase were determined by using ICP-MS, and the removal rates of COD, P and rare earth ions were calculated as shown in Table Y2. Figure 7

[0114] Y3, 5 groups of 250 mL pre-impurity removal wastewater were taken in 5 500 mL beakers, a small amount of 1:1 sulfuric acid was slowly added to the beaker, when the pH value of the wastewater system was adjusted to 6.0, the acid was stopped, and then the pH value was continuously adjusted to 6.5 by adding ammonium bicarbonate. PAC solution (2.5wt%) was first added to the beaker, and the concentration of PAC was fixed at 200 mg / L. The stirring speed was kept at 550 r / min, and the stirring time was 2 min. Then the addition amount of PAM solution (0.5wt%) was changed so that the concentration of PAM was 20 mg / L, 40 mg / L, 60 mg / L, 80 mg / L and 100 mg / L. The stirring speed was kept at 200 r / min, and the stirring time was 15 min to promote the slow growth of the flocs and complete the flocculation process. Ammonium bicarbonate was added during the flocculation process, and the pH value was adjusted to about 6.5. Then the water sample was transferred to the air flotation device for air flotation test, and the air flotation time was fixed at 15 min and the air flotation flow rate was fixed at 80 mL / h. The lower water phase after air flotation test was taken, and the COD content in each lower water phase was determined by using the COD water quality rapid determination instrument. The concentrations of P and rare earth ions in each lower water phase were determined by using ICP-MS, and the removal rates of COD, P and rare earth ions were calculated as shown in Table Y2. Figure 8

[0115] ​​Y4, 5 groups of 250 mL pre-impurity removal wastewater were taken in 5 500 mL beakers, a small amount of 1:1 sulfuric acid was slowly added to the beaker, when the pH value of the wastewater system was adjusted to 6.0, the acid was stopped, and then the pH value was continuously adjusted to 6.5 by adding ammonium bicarbonate; PAC solution (2.5wt%) was first added to the beaker, the concentration of PAC was fixed at 200 mg / L, the stirring speed was kept at 550 r / min, and rapid stirring was carried out for 2 min; then PAM solution (0.5wt%) was added to the beaker, the concentration of PAM was fixed at 40 mg / L; the stirring speed was kept at 200 r / min, slow stirring was carried out for 15 min to promote the slow growth of the flocs, and the flocculation process was completed, ammonium bicarbonate was added during the flocculation process, and the pH value was adjusted to about 6.5; then the water sample was transferred to a flotation device for flotation test, the flotation time was changed to 5 min, 10 min, 15 min, 20 min, 30 min, 40 min, and the flotation flow rate was fixed at 80 mL / h; the lower water phase after the flotation test was taken, the COD content in each lower water phase was determined by using a COD water quality rapid determination instrument, the concentrations of P and rare earth ions in each lower water phase were determined by using ICP-MS, and the removal rates of COD, P and rare earth ions were calculated as shown in Figure 9 ;

[0116] Y5, 5 groups of 250 mL pre-impurity removal wastewater were taken in 5 500 mL beakers, a small amount of 1:1 sulfuric acid was slowly added to the beaker, when the pH value of the wastewater system was adjusted to 6.0, the acid was stopped, and then the pH value was continuously adjusted to 6.5 by adding ammonium bicarbonate; PAC solution (2.5wt%) was first added to the beaker, the concentration of PAC was fixed at 200 mg / L, the stirring speed was kept at 550 r / min, and rapid stirring was carried out for 2 min; then PAM solution (0.5wt%) was added to the beaker, the concentration of PAM was fixed at 40 mg / L; the stirring speed was kept at 200 r / min, slow stirring was carried out for 15 min to promote the slow growth of the flocs, and the flocculation process was completed, ammonium bicarbonate was added during the flocculation process, and the pH value was adjusted to about 6.5; then the water sample was transferred to a flotation device for flotation test, the flotation time was changed to 5 min, 10 min, 15 min, 20 min, 30 min, 40 min, and the flotation flow rate was fixed at 80 mL / h; the lower water phase after the flotation test was taken, the COD content in each lower water phase was determined by using a COD water quality rapid determination instrument, the concentrations of P and rare earth ions in each lower water phase were determined by using ICP-MS, and the removal rates of COD, P and rare earth ions were calculated as shown in Figure 10 ;

[0117] Exploration and analysis: from Figures 6-10As can be seen from the above table, under the conditions of 250 mL of pre-removal of impurities wastewater, fixing the pH value of the pre-removal of impurities wastewater system to 6.5, fixing the concentration of PAC to 200 mg / L, fixing the concentration of PAM to 40 mg / L, fixing the air flotation time to 15 min, and fixing the air flotation flow rate to 80 mL / h, the COD removal rate in the pre-removal of impurities wastewater reaches a maximum of 72.6%, and the COD concentration decreases to 198 mg / L; the P removal rate reaches 99.47%, and the P concentration decreases to 0.13 mg / L; the rare earth ion precipitation rate reaches 99.6%, and the rare earth ion concentration decreases to 2.7 mg / L.

[0118] Exploration Example 3

[0119] The unmodified activated carbon and the alkali-modified activated carbon were analyzed by an Alpha far infrared instrument of the American Brook company, and the infrared spectrum is shown in Figure 11 .

[0120] Under the conditions of 250 mL of pre-removal of impurities wastewater, fixing the pH value of the pre-removal of impurities wastewater system to 6.5, fixing the concentration of PAC to 200 mg / L, fixing the concentration of PAM to 40 mg / L, fixing the air flotation time to 15 min, and fixing the air flotation flow rate to 80 mL / h, the water sample (the COD concentration is 198 mg / L, the P concentration is 0.13 mg / L, and the rare earth ion concentration is 2.7 mg / L) discharged from the bottom outlet of the air flotation tank was taken as the clarified wastewater after air flotation separation.

[0121] Y1, 50 mL of the clarified wastewater was taken in 12 250 mL conical flasks, ammonium bicarbonate was added to adjust the pH value to 6.5, the initial COD concentration was fixed to 198 mg / L, and the adsorption time was fixed to 60 min; the dosing amount of the unmodified and alkali-modified activated carbon was changed, and the dosing amount was 0.05 g, 0.10 g, 0.15 g, 0.20 g, 0.25 g, and 0.3 g, respectively, corresponding to each other in pairs; the adsorption experiment was carried out by oscillating adsorption at a speed of 250 r / min; after adsorption, the supernatant was taken to determine the COD removal rate, and the comparison is shown in Figure 12 .

[0122] Y2, 50 mL of the clarified wastewater was taken in 5 250 mL conical flasks, a small amount of 1:1 sulfuric acid was slowly added to the conical flasks, and the pH value of the clarified wastewater system was gradually adjusted to 5, 5.5, 6, 6, and 6, respectively; the pH values of the last two conical flasks were further adjusted to 6.5 and 7, respectively, by adding ammonium bicarbonate; the initial COD concentration was fixed to 198 mg / L, the adsorption time was fixed to 60 min, and the dosing amount of the alkali-modified activated carbon was fixed to 0.1 g; the adsorption was carried out by oscillating at a speed of 250 r / min; after adsorption, the supernatant was taken to determine the COD content, and the comparison is shown in Figure 13 .

[0123] Exploration analysis: fromFigure 11 It can be seen that the -OH group peak on the curve of alkali-modified activated carbon is obviously enhanced at 3400 cm-1; a clear C=O carbonyl vibration absorption peak appears at 1700 cm-1; the -COOH carboxyl vibration peak at 1480 cm-1 on the curve is obviously weakened, indicating that NaOH reacts with the -COOH carboxyl in the activated carbon, proving that the activated carbon can be successfully alkali-modified by NaOH;

[0124] From Figures 12-13 It can be seen that the alkali-modified activated carbon can better adsorb COD, thereby further reducing the content of organic pollutants in wastewater; in 50 mL of solution, the fixed alkali-modified activated carbon dosage is 0.1 g, the fixed solution system pH is 6.5, the fixed initial COD concentration is 198 mg / L, and the fixed adsorption time is 60 min, the COD removal rate is as high as 80%, and the COD concentration is reduced to 148 mg / L.

[0125] Exploration Example 4

[0126] Take 50 mL of supernatant of the COD solution in Exploration Example 3 with different dilution times of the COD solution, and dilute the COD solution in 7 250 mL conical flasks, with COD concentration gradients of 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, 50 mg / L, 70 mg / L, and 100 mg / L; add ammonium bicarbonate to adjust the pH value to 6.5, fix the alkali-modified activated carbon dosage at 0.1 g, and fix the adsorption time at 60 min; under the condition of 250 r / min, the adsorption experiment is carried out by oscillation, the influence of different COD concentrations on the adsorption effect is explored, and the Langmuir and Freundlich isothermal adsorption model is used to fit the adsorption equilibrium data of COD, and the results are shown in Figures 14-17

[0127] Exploration analysis: from Figures 14-17 It can be seen that the initial COD concentration has an effect on the adsorption capacity of activated carbon, and the adsorption capacity of activated carbon for COD increases with the increase of the initial solution concentration, showing a trend of first increasing fast and then increasing slow. The Langmuir isothermal model can better fit the adsorption process of activated carbon for COD organic matter in water, indicating that the adsorption of this system is mainly monolayer adsorption, and the saturated adsorption capacity is 32.26 mg / g.

[0128] Exploration Example 5

[0129] ​In Example 2, a water sample was taken from 250 mL of pre-removed wastewater, with the pH value of the pre-removed wastewater system fixed at 6.5, the concentration of PAC fixed at 200 mg / L, the concentration of PAM fixed at 40 mg / L, the flotation time fixed at 15 min, and the flotation flow rate fixed at 80 mL / h. The sample was then discharged from the bottom of the flotation tank (COD concentration of 198 mg / L, P concentration of 0.13 mg / L, and rare earth ion concentration of 2.7 mg / L) as the clarified wastewater after flotation separation.

[0130] Nine groups of 50 mL clarified wastewater were placed into nine 250 mL Erlenmeyer flasks. Ammonium bicarbonate was added to adjust the pH to 6.5. The initial COD concentration was fixed at 198 mg / L, and the dosage of alkali-modified activated carbon was fixed at 0.1 g. Adsorption times were varied at 5 min, 10 min, 15 min, 20 min, 30 min, 40 min, 60 min, 80 min, and 100 min. Adsorption experiments were conducted with shaking adsorption at 250 r / min to investigate the effect of adsorption time on COD adsorption. The experimental data were fitted using pseudo-first-order and pseudo-second-order kinetic models. The results are as follows: Figures 18-21 As shown.

[0131] Exploration and Analysis: From Figures 18-21 It can be seen that the adsorption rate is relatively fast when the adsorption time is less than 60 min; when the adsorption time is 60-100 min, the adsorption amount is almost unchanged, and the system can be considered to have reached adsorption equilibrium. The pseudo-first-order kinetic model has a good linear fit and can better describe the adsorption process of COD by activated carbon. The pseudo-first-order kinetic model is mainly affected by the ionic or covalent bonds between the adsorbate and the adsorbent, and it can be inferred that the adsorption of organic matter such as COD on activated carbon is mainly a chemical adsorption process.

[0132] Example 1

[0133] Treatment target: The wastewater to be treated is rare earth extraction and saponification wastewater from the saponification and extraction workshop of Dingnan Dahua New Material Resources Co., Ltd. (pH 0.830, RE concentration 690mg / L, COD concentration 722mg / L, P concentration 23.7mg / L).

[0134] (1) Take 50 mL of wastewater to be treated, use ammonium bicarbonate as pH adjuster, and slowly adjust the pH of the system to 3.0; add 1.0 g of ferrous sulfate heptahydrate and 3 mL of 30% hydrogen peroxide solution, and react for 1 hour; after the reaction is completed, use ammonium bicarbonate as neutralizing precipitant again, and slowly adjust the pH until the supernatant is colorless and transparent, and let it stand and filter.

[0135] (2) Take 250 mL of the filtrate, adjust the pH to 6.0 with dilute sulfuric acid, then finely adjust the pH to 6.5 with ammonium bicarbonate, and further utilize NH4+. +A slightly alkaline environment was created to facilitate deep phosphorus removal. PAC (2.5wt%) was added to a final concentration of 200 mg / L (stirred rapidly at 550 rpm for 2 min), followed by PAM (0.5wt%) to a final concentration of 40 mg / L (stirred slowly at 200 rpm for 15 min). Ammonium bicarbonate was added during flocculation, and the pH was finely adjusted to maintain around 6.5. The water sample was then transferred to an air flotation device for separation. The air flotation time was fixed at 15 min, and the air flotation flow rate was fixed at 80 mL / h. Once the flocs floated to the liquid surface, the scum was separated by scraping. Clarified wastewater was collected from the outlet at the bottom of the air flotation tank.

[0136] (3) Take 50 mL of clarified wastewater, adjust the pH to 6.5 with ammonium bicarbonate, add 0.1 g of alkali-modified activated carbon, shake and adsorb for 60 minutes, and the COD removal rate reaches 80%, the COD concentration drops to 148 mg / L; the P removal rate reaches 99.47%, the P concentration drops to 0.13 mg / L; the rare earth ion precipitation rate reaches 99.6%, and the rare earth ion concentration drops to 2.7 mg / L.

[0137] Comparative Example 1

[0138] Using the method in Example 1, except that ammonium bicarbonate is not added, and sodium hydroxide, a conventional precipitant, is used, the results are as follows. Figure 22 As shown.

[0139] Depend on Figure 22 The effluent COD concentration reached 225 mg / L. The Fe(OH)3 flocs generated by NaOH neutralization were small and loose, with poor ability to capture and sweep organic matter, and easily carried colloidal organic matter into subsequent units, resulting in a higher and more unstable final effluent COD.

[0140] Depend on Figure 22 The effluent P content exceeded the discharge standard, and the NaOH system could not introduce NH4. + This eliminates the deep phosphorus removal pathway that generates magnesium ammonium phosphate (struvite) under weakly alkaline conditions; phosphorus removal also depends on Fe. 3+ FePO4 precipitate is formed; localized over-alkaliness of NaOH can lead to some Fe being precipitated. 3+ It transforms into colloidal Fe(OH)3, reducing its interaction with PO4. 3- The effective contact and sedimentation efficiency is insufficient, resulting in incomplete phosphorus removal and causing the phosphorus content in the effluent to exceed the standard by several times. The deep phosphorus removal effect is significantly worse than that of this invention.

[0141] Depend on Figure 22 The effluent RE recovery rate was low, and NaOH could not provide CO3. 2- RE 3+Only slightly soluble RE(OH)3 can be formed, and the precipitation efficiency is much lower than that of rare earth carbonate precipitation, and stable colloidal filtration is easy to form, causing the loss of rare earth resources. And NaOH introduces a large amount of Na + The sludge composition is complex, and the volume may be larger, which is not conducive to the subsequent extraction and recovery of rare earth, has low value, and is easy to cause secondary pollution.

[0142] It can be seen from the results that the four-in-one synergistic effect of neutralization, optimized flocculation, deep phosphorus removal and rare earth enrichment is achieved by using the multifunctional reagent including ammonium bicarbonate. Although sodium hydroxide is a conventional neutralizing agent, the present application first discovers and verifies that ammonium bicarbonate has an irreplaceable multifunctional synergistic effect in this specific wastewater treatment system, and its effect cannot be achieved by a simple neutralizing agent. The process realizes the two core goals of deep phosphorus removal (P < 0.5 mg / L) and high recovery rate of rare earth enrichment (RE > 99.5%). The present application provides a more efficient, more economical and more environmentally friendly solution, and achieves an unexpected technical effect.

[0143] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all belong to the protection scope of the present application.

Claims

1. A method for treating wastewater using a multifunctional reagent, characterized in that, The multifunctional reagent includes ammonium bicarbonate, and the method is carried out according to the following steps: (1) Add an optional multifunctional reagent to the wastewater to be treated and mix it with Fenton's reagent. After the reaction, add the multifunctional reagent, let it stand and filter. (2) Adjust the pH of the filtrate to 4-8, add flocculant and surfactant, and optionally add a multifunctional reagent during the flocculation process; after flocculation, perform air flotation separation to obtain clarified wastewater; (3) Add an optional multifunctional reagent to the clarified wastewater described in step (2) and perform oil-water separation.

2. The method according to claim 1, characterized in that, In step (1), The wastewater to be treated is phosphorus-containing wastewater, preferably rare earth extraction and saponification wastewater; and / or Add an optional multifunctional reagent to the wastewater to be treated to adjust the pH to 2.5-5, preferably 3-4, more preferably 3; and / or The reaction time is 0.5-2 hours; and / or After the reaction, a multifunctional reagent was added to adjust the iron ion concentration in the supernatant to a range of 0.3-0.5 mg / L.

3. The method according to claim 1, characterized in that, In step (1), Fenton's reagent includes ferrous sulfate heptahydrate and 30% hydrogen peroxide.

4. The method according to claim 3, characterized in that, Fenton's reagent is added so that the amount of ferrous sulfate heptahydrate added is 5-40 g / L, preferably 15-25 g / L, and more preferably 18-22 g / L; and / or Fenton's reagent is added so that the amount of 30% hydrogen peroxide added is 10-100 mL / L, preferably 40-80 mL / L, and more preferably 50-70 mL / L.

5. The method according to claim 1, characterized in that, In step (2), Adjust the pH of the filtrate to 5-7; and / or Add an optional multifunctional reagent to adjust the pH to 6-7.

6. The method according to claim 1, characterized in that, In step (2), The flocculant includes polyaluminum chloride, preferably added at a concentration of 100-400 mg / L, more preferably 180-220 mg / L; and / or The surfactant includes polyacrylamide, preferably added so that the amount of polyacrylamide added is 20-100 mg / L, more preferably 30-50 mg / L.

7. The method according to claim 1, characterized in that, In step (2), Add the flocculant first, then add the surfactant.

8. The method according to claim 1, characterized in that, In step (2), The conditions for flocculation include: stirring during the flocculation process; The stirring speed is 200-550 r / min, preferably 450-550 r / min when adding flocculant or 200-300 r / min when adding surfactant; and / or The stirring time is 2-20 minutes, preferably 1-4 minutes when flocculant is added or 1-16 minutes when surfactant is added; and / or The conditions for air flotation separation include: The time is 5-40 minutes, preferably 10-20 minutes; and / or The gas-liquid ratio is 0.02 to 0.15:1, preferably 0.06 to 0.1:

1.

9. The method according to claim 1, characterized in that, In step (3), Add an optional multifunctional reagent to adjust the pH to 6-7.

10. The method according to claim 9, characterized in that, Oil-water separation methods include adsorption using adsorbents, preferably: The adsorbent includes unmodified activated carbon and / or alkali-modified activated carbon; and / or The adsorbent dosage is 1-6 g / L; and / or The adsorption time is 0.25-2.5 h.

Images