CN103755077B - A kind of method of Phenol-Containing Wastewater Treatment - Google Patents

Abstract

The invention discloses a kind of method of Phenol-Containing Wastewater Treatment, its method is: the first step, chemical flocculation; Second step, the reaction of improvement Zero-valent Iron-Fenton system; 3rd step, secondary flocculate; 4th step, charcoal absorption; Beneficial effect of the present invention: with the reaction of Zero-valent Iron-Fenton system for core, with inorganic flocculation, gac coupling, can Threshold retention high, toxicity is large, the phenolic wastewater of bio-refractory; Materials are few, and cost is low, simple to operate, and treatment effect is good.

Description

A method for treating phenolic wastewater

technical field

The invention relates to a wastewater treatment method, in particular to a method for treating phenol-containing wastewater.

Background technique

At present, phenolic wastewater is a highly toxic and refractory organic wastewater commonly found in industrial wastewater, mainly from coal chemical industry, petrochemical factory, pharmaceutical factory, phenol and phenolic resin production factory, etc. The quality of phenolic wastewater is complex, variable, and difficult to biodegrade. Common methods include adsorption, extraction, and oxidation. However, it is often difficult to achieve the desired treatment effect by using a single treatment method, so the combination of several technologies can be considered. A method that can efficiently, economically and stably treat phenol-containing wastewater must become the research focus and hotspot of scholars at home and abroad.

Advanced oxidation technology uses hydroxyl radical oxidation to remove organic matter in water, and can degrade organic pollutants in water that are difficult to biodegrade or have toxic effects on organisms. The mechanism of traditional Fenton's reagent oxidation reaction is that Fe ²⁺ reacts with H ₂ O ₂ to generate hydroxyl radicals by adding ferrous salt. Therefore, the existing Fenton system reaction has the disadvantages of narrow pH application range, low utilization rate of H ₂ O ₂ , large dosage of reagents, serious loss of Fe ²⁺ , and high cost.

The removal of organic pollutants by the zero-valent iron-Fenton reagent system is also the function of ·OH. In the zero-valent iron-Fenton reagent system, there are two kinds of reactions: homogeneous Fenton reagent oxidation reaction and heterogeneous Fenton reagent oxidation reaction. And the study found that the initial stage of the reaction is dominated by the homogeneous Fenton reagent oxidation reaction. The main mechanism of action is shown in formula (1) - formula (6).

Fe ⁰ +2H ⁺ →Fe ²⁺ +H ₂ (1)

Fe ⁰ +H ₂ O ₂ →Fe ²⁺ +2HO ^- (2)

Fe ²⁺ +H ₂ O ₂ →Fe ³⁺ +2·OH (3)

2Fe ³⁺ +Fe ⁰ →3Fe ²⁺ (4)

Fe ⁰ (surface)+2Fe ³⁺ →3Fe ²⁺ (5)

Fe ⁰ (surface)+H ₂ O ₂ →Fe ²⁺ + OH+HO ^- (6)

In the zero-valent iron-Fenton reagent system, there are two ways to generate hydroxyl radicals: one is generated by the action of homogeneous Fe ²⁺ and H ₂ O ₂ , the other is that zero-valent iron interacts with H ₂ O at its surface active sites ₂ works. Compared with the traditional Fenton reagent, heterogeneous _catalysis , _H2O2 utilization efficiency is higher and the effect is better. Since the specific surface area of zero-valent iron is related to the production efficiency of OH, appropriately increasing the dosage of zero-valent iron will increase the production efficiency of OH. And because of Fe ²⁺ + OH → Fe ³⁺ + 2OH- reaction, adding too much zero-valent iron will produce a large amount of Fe ²⁺ to consume OH, resulting in a decrease in the production efficiency of OH. Therefore, in zero-valent iron -In Fenton, there is an optimal dosage of zero-valent iron. Usually, iron powder or zero-valent nano-iron is added as a catalyst for the zero-valent iron-Fenton reaction. Although the specific surface area is large, it is difficult to recover and the reaction is too violent and difficult to control, which can easily lead to excessive dosage.

Contents of the invention

The object of the present invention is to provide a method for treating phenol-containing wastewater in order to solve the problem that the existing methods for treating phenol-containing wastewater cannot meet the treatment requirements.

The method for processing phenolic waste water of the present invention, its method is as follows:

The first step, chemical flocculation: adjust the pH value of the wastewater sample to 5-9, add polymerized AlCl ₃ with a mass concentration of 10%, and use polyacrylamide with a mass concentration of 0.1% as a coagulant for flocculation, let it stand for 20 minutes and then To filter the flocs, add 14-16mL and 60-80mL of polymerized AlCl ₃ solution with a mass concentration of 10% and a polyacrylamide solution with a mass concentration of 0.1% to treat unit volume (L) of wastewater;

The second step is to improve the zero-valent iron-Fenton system reaction: add the water treated in the first step into the reactor, adjust the pH to 4-6, and first add several pieces of zero-valent iron iron sheets with a thickness of 1-2mm and a square of 100mm , there should be no rust on the surface of the iron sheet, react for 20 minutes, and then react with H ₂ O ₂ at 50°C for 0.5-1h to treat waste water per unit volume (L), and improve the H ₂ O required in the reaction of zero-valent iron-Fenton system The numerical ratio of the volume (ml) of ₂ to the COD (mg/L) of the wastewater raw water is 1:420; the ratio of the volume (ml) of H ₂ O ₂ to the surface area (cm ² ) of the input zero-valent iron sheet is 1 :33;

The third step, secondary flocculation: after the second step of Fenton reaction, adjust the pH value to 7-9, first add CaO suspension with a mass concentration of 5%, and then use polyacrylamide with a mass concentration of 0.1% Use coagulation aid for flocculation, filter flocs, add 5% CaO suspension to 24-26mL of waste water per unit volume (L), add 0.1% polyacrylamide to 80mL;

The fourth step, activated carbon adsorption: use the activated carbon column to absorb the filtered water in the third step, the adsorption time is 1h, the filling capacity of the activated carbon column is 400g per 1L of water, and the activated carbon column can be used repeatedly.

Reaction principle of the present invention:

First use polymerized _AlCl3 and polyacrylamide for flocculation, because polymerized AlCl3 has a wide range _of pH for water quality, making the treated water slightly acidic and relatively clear. Slightly acidic water quality is conducive to the occurrence of the latter step of the reaction, and clear water quality can avoid the deposition of suspended solids on the surface of the zero-valent iron in the latter step of the reaction, which will affect the treatment efficiency of the zero-valent iron. Therefore, the combination of polymerized AlCl ₃ and polyacrylamide flocculation can not only remove part of COD and volatile phenols, but also adjust the pH value of water samples and facilitate the subsequent reactions. The improvement of the zero-valent iron-Fenton reagent system can make the organic matter in the macromolecular phenol-containing wastewater undergo pyrolysis, isomerization and other reactions, and can oxidize most of the macromolecular organic matter into small molecular compounds, and the improved zero-valent iron-Fenton reaction step is simpler , easy to operate; CaO is used as flocculant after the zero-valent iron-Fenton reaction, because CaO reacts with water to form Ca(OH) ₂ flocs, which can not only remove most of the small molecular organics in the water sample, but also remove excess Fe ^{2 +} /Fe ³⁺ is effectively removed; activated carbon plays the role of adsorbing the remaining small molecular compounds and decolorizing. The combination of the three technologies embodies the "coordinated promotion and step-by-step implementation" of wastewater treatment, which can greatly save costs.

Beneficial effects of the present invention:

With zero-valent iron-Fenton system reaction as the core, combined with inorganic flocculation and activated carbon, it can effectively treat phenol-containing wastewater with high concentration, high toxicity, and difficult biodegradation; it uses less material, low cost, simple operation, and good treatment effect.

Description of drawings

Figure 1 is a graph showing the relationship between the removal rate of COD and volatile phenols and the amount of H ₂ O ₂ added.

Detailed ways

Specific implementation plan one:

The water sample is phenol cyanide coking wastewater, COD=5120mg/L, volatile phenol=298mg/L.

Test 1: To determine the amount of polymerized AlCl3, take ₅ wastewater samples, each 500mL, the measured pH value is 6-7, first add the polymerized AlCl3 solution with a mass concentration of ₁₀ %, and the dosage is 5mL respectively. 6mL, 7mL, 8mL, and 9mL were stirred evenly, and then 40mL of polyacrylamide solution with a mass concentration of 0.1% was added as a coagulant aid, stirred evenly, left to stand for 20min, and five water samples were observed. Add 5mL of polymerized AlCl ₃ to the sample, the precipitated flocs become small lumps, the supernatant is turbid, and the interstitial water is turbid, indicating that the amount of polyacrylamide added is appropriate, but the amount of polymerized AlCl ₃ is not enough; add 6mL of polymerized AlCl ₃ The precipitated flocs of the sample were in small pieces, the supernatant was clear, and the interstitial water was relatively clear, indicating that the amount of polyacrylamide added was appropriate, and the amount of polymerized AlCl ₃ added was basically appropriate; the precipitated flocs of the sample added with 7mL polymerized AlCl ₃ In the shape of large blocks, the supernatant liquid is clear, and the interstitial water is clear, indicating that the amount of polymerized AlCl ₃ and polyacrylamide added is appropriate, and the flocculation effect is good _; The solution is clear, and the interstitial water is clear, indicating that the amount of polymerized AlCl ₃ and polyacrylamide added is appropriate, and the flocculation effect is good; the precipitated flocs of the sample added with 9mL of polymerized AlCl ₃ are in the shape of large pieces, the supernatant is clear, and the interstitial water is clear, but There is a lot of scum, indicating that the amount of polyacrylamide added is appropriate, and the amount of polymerized AlCl ₃ added is too large. At this time, the COD values of each supernatant were 4352mg/L, 4220mg/L, 4120mg/L, 4091mg/L, 4080mg/L respectively. The COD removal rates were 14.6%, 17.6%, 19.5%, 20.1%, and 20.3%. The volatile phenol contents were 273.6mg/L, 267.9mg/L, 259.6mg/L, 258.8mg/L, and 257.3mg/L, and the removal rates were 8.2%, 10.1%, 12.9%, 13.2%, and 13.7%, respectively. The pH at this time was all 6-7. The data shows that when 7-8mL of 10% polymerized AlCl ₃ solution and about 40mL of 0.1% polyacrylamide solution are added to each 500mL water sample, the treatment effect is good. Continue to increase the amount of flocculant dosage, and the treatment efficiency is very high. On the contrary, the generation of a large amount of scum is not conducive to the separation and subsequent treatment of water samples, and leads to an increase in cost. Therefore, it is determined that the optimal dosage of flocculant is to add 7-8mL of 10% polymerized AlCl ₃ solution and about 40mL of 0.1% polyacrylamide solution per 500mL water sample.

Test 2: Take 2500mL of wastewater samples, adjust the pH to 5-9, add 35mL of polymerized AlCl ₃ solution with a mass concentration of 10%, and then add 200mL of a polyacrylamide solution with a mass concentration of 0.1%, stir evenly, and let it stand for 20 minutes Take the supernatant and adjust the pH to 4-6. At this time, COD=3990mg/L, volatile phenol=260mg/L, divide the water sample into 5 parts on average, heat to about 50°C, add 1mm thick and 10cm side length 1 piece of square zero-valent iron iron sheet, add 3mLH ₂ O ₂ , 4mLH ₂ O ₂ , 5mL H ₂ O ₂ , 6mL H ₂ O ₂ , 7mL H ₂ O ₂ at one time, and react at constant temperature for about 0.5-1h. The measured COD values are 2110mg/L, 1790mg/L, 1495mg/L, 1290mg/L, 1200mg/L, and the volatile phenol values are 56.4mg/L, 40.3mg/L, 29.2mg/L, 22.9mg/L , 19.5mg/L. Figure 1 shows the relationship between the COD and volatile phenol removal rate and the amount of H ₂ O ₂ added. With the increase of H ₂ O ₂ , the removal efficiency of COD and volatile phenols is significantly reduced. Considering the treatment cost and H ₂ O ₂ utilization efficiency and other factors, the optimal dosage of H ₂ O ₂ is 6 mL of H ₂ O per 500 mL of water sample. ₂ . That is, for every 1L of wastewater, the ratio of the volume of H ₂ O ₂ (mL) to the COD value of wastewater raw water (mg/L) is 1:420.

Take 500mL wastewater sample, adjust the pH to 5-9, add 7-8mL of polymerized AlCl ₃ solution with a mass concentration of 10%, about 40mL of a polyacrylamide solution with a mass concentration of 0.1%, let it stand for 20min, filter, disposable Add 6mL of H ₂ O ₂ , add 1 piece of square zero-valent iron sheet with a side length of 10cm, and react for 0.5-1h. Take the supernatant, add 12mL CaO suspension with a mass concentration of 5%, use 40mL PAM as a coagulant, let stand for 10min, and filter the precipitate. At this time, COD=480mg/L, volatile phenol=11.8mg/L, and the total removal rate of COD and volatile phenol is about 91.6% and 96.1%, respectively.

Take the supernatant and adsorb it on an activated carbon column filled with 200 g of activated carbon for about 1 h at room temperature. At this time COD≈180mg/L, volatile phenol≈5mg/L. At this time, the total removal rate of COD is about 96.5%, and the total removal rate of volatile phenol is about 98.4%, which is a light yellow transparent liquid. It has reached the national secondary standard for comprehensive sewage discharge.

Specific implementation plan two:

Compared with the specific embodiment 1, H 2 O ₂ is added in 3 times, and _{2 mL of H 2 O 2} is added every 15 minutes. After the secondary flocculation is completed, COD=350mg/L, volatile phenol=7.8mg/L, and the total removal rate of COD and volatile phenol is about 93.2% and 97.4% respectively. The effect of multiple dosing of H ₂ O ₂ is better than that of single dosing.

Take the supernatant and adsorb with activated carbon for about 1 h at room temperature. At this time COD≈140mg/L, volatile phenol=3mg/L. At this time, the total removal rate of COD is about 97.5%, and the total removal rate of volatile phenol is about 98.9%, which is a light yellow transparent liquid. It has reached the national secondary standard for comprehensive sewage discharge.

Specific implementation plan three:

Compared with the second embodiment, after adjusting the pH of the water sample to 4-6, first add zero-valent iron iron flakes to react for about 20 minutes, and then add H ₂ O ₂ in 3 times, and react for 0.5-1 hour. After the secondary flocculation, the measured COD=310mg/L, volatile phenol=6.2mg/L. It shows that appropriately increasing the reaction time of zero-valent iron can increase the treatment of organic matter.

Specific implementation plan four:

Take 4 parallel samples, and each water sample is 1L. Compared with the third embodiment, the other conditions are exactly the same, except that the number of zero-valent iron iron sheets added is 1 piece, 2 pieces, 3 pieces, and 4 pieces. After the secondary flocculation, _{1 piece} of COD = 362mg/L, _{1 piece} of volatile phenol = 8.2mg/L; _{2 pieces} of COD ₌ 316mg/L, _{2 pieces} of volatile phenol = 6.5mg/L; _Block = 342mg/L, _{3 blocks} of volatile phenol = 6.4mg/L; _{4 blocks of} COD = 418mg/L, _{4 blocks} of volatile phenol = 6.1mg/L. It can be seen from the comparison that there is an optimal value for the dosage of zero-valent iron flakes. Too much increase of zero-valent iron flakes has no obvious effect on the treatment efficiency of volatile phenols, but it leads to the increase of COD value. It may be caused by excessive Fe ²⁺ in the solution, so the optimal dosage is determined as per 1L of wastewater, adding 2 pieces of zero-valent iron iron sheets, that is, the volume of H ₂ O ₂ (mL) and zero-valent iron iron sheets The surface area (cm ² ) ratio is 1:33.

Specific implementation plan five:

Compared with the third embodiment, after adjusting the pH of the water sample to 4-6, first add zero-valent iron iron sheet, heat to 50°C, and then add H ₂ O ₂ in 3 times, and react for 0.5-1h. Secondary flocculation after the reaction. At this time COD=150mg/L, volatile phenol=3mg/L. The improvement of the treatment effect by heating is particularly obvious.

Finally, it was adsorbed on activated carbon for about 1 hour. At this time, COD=80mg/L, volatile phenol=0.3mg/L, and the water sample was a colorless transparent liquid. The indicators have reached the first-level national sewage comprehensive discharge standard.

Specific implementation plan five:

Take a 20L wastewater sample, adjust the pH of the water sample to 5-9, add 300mL of 10% polymerized AlCl ₃ solution and about 1300mL of 0.1% polyacrylamide solution, stir well, let it stand, and filter the precipitate. Take the supernatant, adjust the pH to 4-6, add 20 pieces of square zero-valent iron sheets with a side length of 10cm and a thickness of 1mm, heat to about 50°C, and react for 20min, add 80mL of H ₂ O ₂ solution every 10min, a total of 3 times, constant temperature reaction for about 0.5-1h.

After the reaction is finished, directly add 480ml of CaO suspension with a mass concentration of 5%, stir evenly, then add 1600mL of a 0.1% polyacrylamide solution, stir evenly, let stand for 10min, and filter the precipitate. The supernatant was absorbed with activated carbon for 1 h at room temperature. At this time COD=68mg/L, volatile phenol=0.2mg/L. At this time, the removal rate of COD is about 98.7%, and the removal rate of volatile phenol is about 99.9%. All meet the first-class standard for comprehensive sewage discharge.

Specific implementation plan six:

Wastewater COD=22100mg/L, volatile phenol=820mg/L.

Take 1L of the original water sample, adjust the pH of the water sample to 5-9, add 16mL of polymerized AlCl ₃ solution with a mass concentration of 10%, and about 80mL of a polyacrylamide solution with a mass concentration of 0.1%, stir well, let stand for 20min, and filter the precipitate Take the supernatant, adjust the pH to 4-6, add 8 pieces of square zero-valent iron iron sheets with a side length of 10cm and a thickness of 1mm, heat to about 50°C, and react for 20min, add 16mL of H ₂ O ₂ solution every 10min, a total of 3 times, constant temperature reaction for about 0.5 ~ 1h. After the reaction is finished, directly add 24ml of CaO suspension with a mass concentration of 5%, stir evenly, then add 80mL of polyacrylamide with a mass concentration of 0.1%, stir evenly, let stand for 10min, and filter the precipitate. Take the supernatant and activated carbon column, fill with 400g activated carbon, and adsorb at room temperature for 1h. The final effluent is yellowish clear liquid, COD=85mg/L, volatile phenol=0.5mg/L, all of which meet the national first-class sewage discharge standard.

Claims (1)

1. a method for Phenol-Containing Wastewater Treatment, is characterized in that: its method is as described below:

The first step, chemical flocculation: regulate waste water water sample pH value to 5-9, add the polymerization AlCl that mass concentration is 10% ₃solution, be that the polyacrylamide solution of 0.1% flocculates for coagulant aids with mass concentration, then standing 20min filters flco, and process unit volume L waste water adds the polymerization AlCl that mass concentration is 10% ₃solution and mass concentration are that the amount of 0.1% polyacrylamide solution is respectively 14-16mL and 60-80mL;

Second step, the reaction of improvement Zero-valent Iron-Fenton system: the water after the first step process is added reactor, regulates pH to 6, first add several pieces thick 1-2mm, the Zero-valent Iron iron plate that 100mm is square, can not there be iron rust on the surface of iron plate, reaction 20min, then under 50 DEG C of conditions and H ₂o ₂reaction 0.5-1h, process unit volume L waste water, improves required H in the reaction of Zero-valent Iron-Fenton system ₂o ₂volume ml and the inatheadearomatizationazone of CODmg/L of the former water of waste water be 1:420; H ₂o ₂volume ml and the surface-area cm dropping into Zero-valent Iron iron plate ²ratio be 1:33;

3rd step, secondary flocculate: after the Fenton's reaction of second step, adjust ph to 9, first add the CaO suspension liquid that mass concentration is 5%, do coagulant aids with the polyacrylamide solution that mass concentration is 0.1% again to flocculate, filter flco, the waste water of unit volume L add mass concentration be 5% CaO suspension liquid be 24-26mL, to add mass concentration be the amount of 0.1% polyacrylamide solution is 80mL;

4th step, charcoal absorption: with the water after filtration in activated carbon column absorption the 3rd step, adsorption time is 1h, and the loading level of activated carbon column is that every 1L water adds 400g, and activated carbon column can Reusability.