CN110615514A

CN110615514A - Aluminum salt microorganism composite flocculant for treating shale gas drilling wastewater

Info

Publication number: CN110615514A
Application number: CN201910978387.0A
Authority: CN
Inventors: 朱天菊; 任宏洋; 陈丹丹; 李蕊; 王伟
Original assignee: Southwest Petroleum University
Current assignee: Southwest Petroleum University
Priority date: 2019-10-15
Filing date: 2019-10-15
Publication date: 2019-12-27
Anticipated expiration: 2039-10-15
Also published as: CN110615514B

Abstract

The invention discloses an aluminum salt microbial composite flocculant for treating shale gas drilling wastewater, belonging to the field of environmental wastewater treatment. The preparation process of the composite flocculant comprises the following specific steps: adding PDMDAAC (dimethyl diallyl ammonium chloride homopolymer) into an aluminum sulfate solution in a mass ratio of 30: 1-35: 1; obtaining PAS-PDM solution; then adding polysaccharide extracted from mycobacteria into the mixed solution, wherein the addition amount is 1%; stirring to obtain the stable aluminum salt microorganism composite flocculant. The aluminum salt microbial flocculant prepared by the invention has better coagulation effect than that of a conventional coagulant under the condition of similar addition in the wastewater treatment process, and the COD removal rate is increased by 24.10-12.60 percent; the chroma removal rate is increased by 50-10 percent.

Description

Aluminum salt microorganism composite flocculant for treating shale gas drilling wastewater

Technical Field

The invention belongs to the field of environmental wastewater treatment, and particularly relates to an aluminum salt microbial composite flocculant for treating shale gas drilling wastewater.

Background

The novel and high-efficiency water treatment agent is a supporting industry which is mainly developed in the technical field of water treatment environmental protection industry, and is also a basic industry for water industry, water pollution treatment engineering technology and equipment innovation development. The inorganic polymer coagulant has the advantages of strong applicability to various water treatment with complex components, high positive charge density and low cost, but has small generated floc, large dosage and large generated sludge. Generally, the organic polymeric flocculant has hydrophilic groups such as-COO-, -NH-, -OH and the like, has various structures such as chain, ring and the like, is beneficial to pollutants to enter flocs, and has the advantages of small using amount, large formed floc, easy treatment of residual sludge, good decoloration and the like, but has higher cost. Therefore, the development and research of the novel composite flocculant aim to improve the flocculation treatment effect and reduce the use cost at the same time; meanwhile, due to the synergistic effect, the surface morphology structure and charge distribution of the inorganic polymer coagulant can be improved to a certain extent, the adsorption bridging and net capturing capabilities of the inorganic polymer coagulant are increased, and the coagulation performance is enhanced.

Currently, PFC-PDMDAAC, PAC-PDMDAAC, PFS-PAA, PFS-CP, PFC-P (ECH-DAM) and the like are representative in the research of inorganic-organic composite coagulants. According to research, the inorganic-organic composite coagulant has higher treatment effect on different waste water than that of a single polymer inorganic coagulant or organic coagulant, has the coagulation advantages of mainly improving the electric neutralization capacity, increasing the specific surface area and the like, but has to be improved in bridging and net-repairing capacity through analysis of microstructures and the like.

The shale gas drilling wastewater is wastewater generated in the shale gas exploitation drilling process, and the types and the contents of pollutants are related to the used drilling fluid and are simultaneously influenced by the stratum. The main pollutants are high-concentration organic matters, suspended particles, partial metal ions and the like, and the direct discharge can pollute soil, surface water, underground water and the like near the platform. How to efficiently and greenly remove a large amount of organic matters, suspended matters, chromaticity and the like in the coagulant, and the development and the use of the efficient coagulant are the key points of pretreatment.

Disclosure of Invention

In order to overcome the defects and shortcomings in the prior art, the primary object of the invention is to provide an aluminum salt type microbial composite flocculant for treating shale gas drilling wastewater.

The invention aims to realize the following technical scheme that an aluminum salt microbial composite flocculant for treating shale gas drilling wastewater is prepared by the following steps:

s1: culturing the mycobacterium separated and purified from the soil by adopting a beef extract culture medium, wherein the inoculation amount is 1% by volume, after fermenting and culturing for 96 hours, centrifuging the bacterial liquid for 10 minutes at 4000r/min, mixing the centrifuged supernatant with absolute ethyl alcohol according to the proportion of 1: 3-1: 3.5, standing for 12 hours at low temperature, centrifuging the mixed liquid for 15 minutes at 4000r/min, pouring out the supernatant, taking out the precipitate, and drying the precipitate by using a vacuum drying box (the temperature is 35 ℃) to obtain mycobacterium polysaccharide;

s2: preparing industrial-grade aluminum sulfate with the aluminum sulfate content of 90% into a solution with the mass fraction of 20%, filtering, removing impurities, placing the solution into a reaction kettle, heating to the temperature of 75-85 ℃, adding PDMDAAC with the molecular weight of 200-300 ten thousand, wherein the aluminum sulfate solution and Al in the mixed solution are mixed₂O₃The mass ratio of the PDMDAAC to the PDMDAAC is 30: 1-35: 1; adjusting the stirrer to be at a medium speed and stirring for 90-100 min;

s3: keeping the solution prepared in the step S2 at 75-85 ℃ in a reaction kettle, adding the mycobacterium polysaccharide F1 prepared in the step S1 in an amount of 0.8-1.2% by mass, and adjusting a stirrer to be at a medium speed for stirring for 25-30 min;

s4: the solution prepared in step S3 was dried in an oven at a temperature of 50 ℃.

Further, the mixing ratio of the supernatant centrifuged in step S1 to absolute ethanol was 1:3.

Further, Al in step 2₂O₃The mass ratio of the meter to the PDMDAAC was 30: 1.

Further, the addition amount of the mycobacteria polysaccharide added in the step S3 is 1% by mass.

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

according to the aluminum salt microbial composite flocculant obtained by the invention, polymeric aluminum hydroxide exists in the aluminum salt microbial composite flocculant through an infrared spectrometer and an XRD spectrogram, which shows that the aluminum salt microbial composite flocculant F1-PDM/PAS causes the change of the internal structure through the interaction of chemical reactions. The F1-PDM/PAS composite flocculant prepared by the invention has better coagulation effect than that of conventional coagulants such as PAS, PAC, PAM, PAF and the like under the condition of similar addition amount in the treatment of drilling wastewater, the removal rate of COD is increased by more than 20%, and the removal rate of chromaticity is increased by more than 15%; the removal rate of COD in the treatment of the domestic wastewater is increased by more than 15 percent, and the removal rate of chromaticity is improved by more than 5 percent.

The F1-PDM/PAS composite flocculant obtained by the invention is not simply physically connected, PAS is formed after aluminum sulfate is hydrolyzed, and is combined with PDM functional groups to form a sheet structure, and the positively charged mycobacteria polysaccharide (F1) is introduced to the surface of the sheet structure, so that the specific surface area is increased, more adsorption potentials are provided for colloid particles in a liquid phase, the electric neutralization capacity is improved, the composite flocculant is favorable for compressing a double electric layer, and the coagulation effect is improved.

Drawings

FIG. 1 is a graph showing the effect of F1-PDM/PAS dosage on ZETA potential according to the present invention;

FIG. 2 is an IR spectrum of F1-PDM/PAS and F1 according to the present invention;

FIG. 3 is an electron microscope scan of F1-PDM/PAS and F1 of the present invention.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.

The invention relates to an aluminum salt microbial composite flocculant (abbreviated as F1-PDM/PAS) for treating shale gas drilling wastewater, which is prepared by the following steps:

s1: culturing the mycobacterium separated and purified from the soil by adopting a beef extract culture medium, wherein the inoculation amount is 1% by volume, after fermentation culture is carried out for 96 hours, centrifuging the bacterial liquid for 10 minutes at 4000r/min, mixing the centrifuged supernatant with absolute ethyl alcohol according to the proportion of 1: 3-1: 3.5, standing at low temperature for 12 hours, centrifuging the mixed liquid for 15 minutes at 4000r/min, pouring out the supernatant, taking out the precipitate, and drying by using a vacuum drying oven (at the temperature of 35 ℃) to obtain mycobacterium polysaccharide F1;

s2: preparing industrial-grade aluminum sulfate with the aluminum sulfate content of 90% into a solution with the mass fraction of 20%, filtering, removing impurities, placing the solution into a reaction kettle, heating to the temperature of 75-85 ℃, adding PDMDAAC with the molecular weight of 200-300 ten thousand, wherein the aluminum sulfate solution and Al in the mixed solution are mixed₂O₃The mass ratio of the PDMDAAC to the PDMDAAC is 30: 1; adjusting the stirrer to be at a medium speed and stirring for 90-100min to obtain PDM/PAS;

s4: and (4) placing the solution prepared in the step S3 in an oven with the temperature of 50 ℃ for drying to obtain F1-PDM/PAS.

The mixing ratio of the supernatant centrifuged in step S1 to absolute ethanol was 1:3 as the optimal ratio.

Al in step 2 as the optimum ratio₂O₃The mass ratio of the PDMDAAC to the PDMDAAC is 30: 1; the reaction temperature was 75 ℃.

As the optimal ratio, the amount of the added mycobacterial polysaccharide F1 in step S3 is 1% by mass.

Example 1:

preparing industrial-grade aluminum sulfate with the aluminum sulfate content of 90% into a solution with the mass fraction of 20%, filtering, removing impurities, placing the solution into a reaction kettle, heating the reaction kettle to the temperature of 75 ℃, adding PDMDAAC with the molecular weight of 200-300 ten thousand, wherein the aluminum sulfate solution in the mixed solution is Al₂O₃The mass ratio of the powder to PDMDAAC is 30:1, the stirrer is adjusted to be at medium speed for stirring for 90min, the mycobacteria polysaccharide F1 prepared in the step S1 is added, the adding amount is 0.8 percent by mass, the stirrer is adjusted to be at medium speed for stirring for 25min, and thenAnd drying the prepared solution in an oven at the temperature of 50 ℃ to obtain the A-type aluminum salt microbial composite flocculant, wherein the aluminum salt microbial composite flocculant is abbreviated as F1-PDM/PAS.

Wherein F1 is short for mycobacterial polysaccharide, therefore mycobacterial polysaccharide F1 is generally referred to herein as mycobacterial polysaccharide or F1. The aluminum salt microbial composite flocculant obtained by the invention is polymerized from mycobacteria polysaccharide F1, PDMDAAC and aluminum sulfate, so that the aluminum salt microbial composite flocculant is abbreviated as F1-PDM/PAS in the text.

Example 2:

preparing industrial-grade aluminum sulfate with the aluminum sulfate content of 90% into a solution with the mass fraction of 20%, filtering, removing impurities, placing the solution into a reaction kettle, heating the reaction kettle to the temperature of 80 ℃, adding PDMDAAC with the molecular weight of 200-300 ten thousand, wherein the aluminum sulfate solution in the mixed solution is Al₂O₃And (3) counting the mass ratio of the B-type F1-PDM/PAS to PDMDAAC to be 30:1, adjusting a stirrer to be at a medium speed for stirring for 100min, adding the mycobacteria polysaccharide F1 prepared in the step S1, adjusting the stirrer to be at a medium speed for stirring for 25min according to the mass ratio of 1%, and drying the prepared solution in an oven at the temperature of 50 ℃ to obtain the B-type F1-PDM/PAS.

Example 3:

preparing industrial-grade aluminum sulfate with the aluminum sulfate content of 90% into a solution with the mass fraction of 20%, filtering, removing impurities, placing the solution into a reaction kettle, heating the reaction kettle to the temperature of 85 ℃, adding PDMDAAC with the molecular weight of 200-300 ten thousand, wherein the aluminum sulfate solution in the mixed solution is Al₂O₃And (3) calculating the mass ratio of the polysaccharide to PDMDAAC to be 35:1, adjusting a stirrer to be at a medium speed and stirring for 100min, adding the mycobacterium polysaccharide F1 prepared in the step S1, adjusting the stirrer to be at a medium speed and stirring for 25min according to the mass ratio of 1.2%, and drying the prepared solution in an oven at the temperature of 50 ℃ to obtain the C-type F1-PDM/PAS.

Comparison of congealing test of congealing F1-PDM/PAS:

the 6 1L stirred cups to be subjected to coagulation test were filled with 500 mL of drilling wastewater, programmed at 280 r.min^-1Stirring for 1min, 800 r.min^-1Stirring for 5 min. Adding 3 of the stirring cups into the stirring cup respectivelyThe A, B, C three types of F1-PDM/PAS obtained in the above example are 10 mL each and 1 mL of polyacrylamide (0.1% PAM) as a coagulant aid, and are settled for 60 min, and the supernatant of the stirring cup is taken to measure the COD content (COD is Chemical Oxygen Demand) by a COD measuring instrument, and the chromaticity change is measured by a dilution colorimetry. The average COD content in the drilling wastewater without the addition of F1-PDM/PAS was found to be 9560mg/L with a color of 4000 times. The COD content in wastewater added with A, B, C three types of F1-PDM/PAS is obviously reduced, wherein the COD removal rate of the added A type F1-PDM/PAS is 87%, the COD removal rate of the added B type F1-PDM/PAS is 91%, the COD removal rate of the added C type F1-PDM/PAS is 89%, and the results are shown in the following table 1. (Note: in general, when the coagulant is used, a coagulant aid can be added to provide a coagulation effect, not a comparative coagulant).

Table 1: A. b, C coagulation effect table of three types of F1-PDM/PAS

	Class A F1-PDM/PAS	Class B F1-PDM/PAS	Class C F1-PDM/PAS
				COD removal rate	87%	91%	89%

In comparison to conventional coagulant tests:

in order to further understand the coagulation effect of the F1-PDM/PAS composite flocculant applied AS a water treatment agent and in the treatment of drilling wastewater, the F1-PDM/PAS composite flocculant is compared with conventional coagulants such AS Aluminum Sulfate (AS), polyaluminium chloride (PAC), ferric trichloride and the like under the same conditions, and the experiment is AS follows:

500 mL of the drilling wastewater from the previous experiment were placed in 6 1L stirred cups, programmed at 280 r.min^-1Stirring for 1min, 800 r.min^-1Stirring for 5 min. In the coagulation test, 10 mL of C-type F1-PDM/PAS composite flocculant (the adding amount is about 3500 mg/L) is added into one stirring cup, Aluminum Sulfate (AS), polyaluminum chloride (PAC) and ferric chloride which are the same in adding amount are added into the other three stirring cups respectively to serve AS coagulants, 1 mL of coagulant aid polyacrylamide (0.1% PAM) is added while stirring, sedimentation is carried out for 60 min, the COD content of the supernatant of the stirring cup is measured by using a COD measuring instrument, and the chromaticity change of the supernatant is measured by using a dilution colorimetric method. The COD content in the drilling wastewater without the coagulant is 9560mg/L and the chroma is 4000 times. The treatment effect of the drilling wastewater added with the coagulant is shown in the following table.

TABLE 2 treatment effect of different coagulants on drilling wastewater

Name of coagulant	F1-PDM/PAS	AS	PAC	FeCl₃
					COD（mg/L）	917.76	2647.16	1431.13	2042.02
COD removal Rate (%)	89.40	72.31	85.03	78.64
					Chroma (double)	16	200	100	150

Through research and multiple experiments, the reaction kettle is heated in the step S2 until the temperature cannot be too high or too low, because the hydrolysis reaction of the aluminum sulfate is an endothermic reaction, the hydrolysis degree of the aluminum sulfate can be improved by properly heating within a certain range, and the content of aluminum ions is increased in the polymerization process; however, this temperature range is not suitable for the polymerization of aluminum sulfate as the temperature continues to rise, so that the polymer content decreases. After the test, the general temperature range is 75-85 ℃, wherein 80 ℃ is the best.

Through research and multiple experiments, if the adding amount mass ratio of the mycobacteria polysaccharide F1 in the step S3 is low, the introduced high molecular biological coagulant is low in amount, and negative charges of colloidal particles cannot be neutralized, so that the compression double electric layers and the adsorption effect of coagulation are not facilitated; if the addition mass ratio of the mycobacteria polysaccharide is too low, the Zeta potential is increased, so that flocs in the solution are positively charged, and the treatment effect of the composite flocculant is poor due to the adverse destabilization. After the test, the mass ratio of the adding amount is generally 0.8-1.2%, and the best is 1%.

1000 mL of water sample is taken in a coagulation stirring cup, the pH value is adjusted to a preset value, and a certain amount of coagulant is added. And carrying out coagulation stirring for l min at the rotating speed of 350 r/min < -1 >, sampling by using a sample injector, injecting into a detection pool, and measuring the Zeta potential by using a Zeta potential and particle size analyzer. Each sample was automatically measured 3 times, and the average value thereof was calculated, which was the final Zeta potential value. As shown in the figure 1 which is a graph of the influence of the addition amount of F1-PDM/PAS on the Zeta potential, the Zeta potential is increased along with the increase of the addition amount from the figure 1, and the F1-PDM/PAS is a cationic coagulant.

The IR spectrum of F1-PDM/PAS and M.mycorrhiza polysaccharide F1 can be shown in FIG. 2, and it is known from FIG. 2 that: in the figure, F1 is used as a microbial flocculant and F1-PDM/PAS composite flocculant is at 3400 cm^-1、1617 cm^-1The absorption peak values of tensile vibration and bending vibration of-OH are mostly caused by water in a sample; at 2957 cm^-1And 2870 cm^-1Tensile vibration absorption peaks of-CH 4 and-CH 2, respectively; 1476 cm^-1And 1387 cm^-1The absorption peaks of the C-H bond in the plane for the anti-symmetric bending vibration and the plane-symmetric bending vibration are respectively provided; F1-PDM/PAS at 3200-^-1The absorption peak of-OH is between the two, and the content of-OH groups is large; 1600 cm^-1The nearby absorption peak is due to bending vibration of the bound water; 670 cm^-1The peak of (2) is an absorption peak of the aluminum polyhydroxyl. The spectrogram comparison shows that F1 and PDMDAAC are combined to change to a certain extent, the hydroxyl absorption peak is obviously enhanced, and the formed polymeric aluminum has a strong absorption peak, so that the coagulation effect is improved.

FIG. 3 can be obtained by scanning F1-PDM/PAS and Mycobacterium polysaccharide F1 under electron microscope, and it can be seen from FIG. 3 that: at 50000 times magnification, the F1 is clearly visible as a predominantly reticulated structure at a 2 μm size; F1-PDM/PAS is the three-dimensional structure of slice space, has better porosity between the piece, can increase specific surface area, can improve and congeal the effect.

The above description is only exemplary of the present invention and should not be taken as limiting the invention, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An aluminum salt type microbial composite flocculant for treating shale gas drilling wastewater is characterized by being prepared by the following steps:

s2: preparing industrial-grade aluminum sulfate with the aluminum sulfate content of 90% into a solution with the mass fraction of 20%, filtering, removing impurities, placing the solution in a reaction kettle, heating to the temperature of 75-80 ℃, adding PDMDAAC with the molecular weight of 200-300 ten thousand, wherein the mass ratio of aluminum sulfate solution to PDMDAAC in the mixed solution is 30: 1-35: 1 by Al2O 3; adjusting the stirrer to be at a medium speed and stirring for 90-100 min;

s3: keeping the solution prepared in the step S2 at 75-80 ℃ in a reaction kettle, adding the mycobacteria polysaccharide prepared in the step S1 in an amount of 0.8-1.2% by mass, and adjusting a stirrer to stir at a medium speed for 25-30 min;

2. The aluminum salt microbial composite flocculant for treating shale gas drilling wastewater as claimed in claim 1, wherein the mixing ratio of the centrifuged supernatant and the absolute ethanol in step S1 is 1:3.

3. The aluminum salt microbial composite flocculant for treating shale gas drilling wastewater as claimed in claim 1, wherein the mass ratio of Al2O3 to PDMDAAC in step 2 is 30: 1.

4. The aluminum salt type microbial composite flocculant for treating shale gas drilling wastewater as claimed in claim 1, wherein the addition amount of the mycobacterial polysaccharide added in step S3 is 1% by mass.