CN110846356A - A new method for microbial fuel cell treatment of starch substances extracted from waste paper pulp - Google Patents

Abstract

The invention provides a new method for treating starch-like substances as main organic pollutants extracted from waste paper pulp by a microbial fuel cell. The method includes two steps of starch liquid bioenzymatic saccharification and microbial battery purification. The enzymes used in saccharification are a combination of alpha-amylase, beta-amylase, endo-cellulase and cyclodextrinase or pullulanase. After saccharification, the turbidity of the starch saccharification solution is controlled below 10-50 NTU, and it can be used for MFC purification and electric energy conversion treatment; the anode chamber of the biofuel cell is metered into the saccharified starch by a peristaltic pump to extract the saccharified solution, and the batch type aerobic culture activated sludge is used as the Microbial cells, the anode chamber is fed with _N2 for stirring; 0.2mol/L disodium hydrogen phosphate-potassium dihydrogen phosphate buffer solution is used in the cathode chamber as the ionic liquid, and a moderate amount of air is introduced to supplement dissolved oxygen, and the anode is made of carbon fiber material , The cathode adopts stainless steel mesh as the electrode, the treatment temperature is 5-35 ℃, and the COD removal rate can be removed more than 60%-85% within 24 hours.

Description

A new method for microbial fuel cell treatment of starch substances extracted from waste paper pulp

technical field

The invention belongs to the field of papermaking, and relates to starch processing technology, in particular to a new method for microbial fuel cell (Microbial Fuel Cell, MFC) processing of starch-like substances as main organic pollutants extracted from waste paper pulp.

Background technique

The waste paper fiber raw material is heated and shrunk for many times, the structure becomes compact, and the tiny pores on the fiber surface are closed, which leads to a significant decrease in the elasticity and swelling ability of the fiber, which will cause the problem of keratinization of the fiber. In addition, the repeated use of beating leads to shorter fibers, which makes paper difficult to make and the strength of the paper sheet is poor. A large number of reinforcing additives are needed to improve this problem. The molecular structure of starch is very similar to the molecular structure of papermaking fiber, and it is widely used in the papermaking industry due to its wide source and low price. Starch and modified starch products are used in a huge amount in the pulp and paper industry. At present, about 10-14% of the starch organics are in the raw materials of domestic waste paper boxes. Among them, the amount of starch in the sizing process alone accounts for more than 4% of the fiber raw material.

A large amount of starch exists in waste paper, which brings great challenges to papermaking and wastewater treatment. First, the accumulation of anionic waste in the wet end of papermaking increases the complexity of wet end chemistry; second, it increases the waste water treatment load and makes the wastewater treatment system. Difficult to deal with. The 4% yield loss in the recycled papermaking of container board is caused by the decomposition and loss of starch substances in the pulping and papermaking process. These substances accumulate in the papermaking water and produce various organic acids through microbial decomposition, which are the dissolution and loss of papermaking white water. The main source of colloidal substances.

Starch substances are used in large quantities in the papermaking process, resulting in a large amount of starch entering the papermaking water system during the recycling process, which not only affects the chemical balance of the papermaking wet end, but also causes the failure of the amount of papermaking auxiliaries, increases the consumption of auxiliaries, and affects the operation of the paper machine and paper quality. , and will cause great pressure on water treatment, which will directly affect the development of circular economy in papermaking. Extracting starch-like organic matter from waste paper recycling pulping process avoids its accumulation in the papermaking system, helps to purify the pulp, and improves the chemical properties of the papermaking wet end. However, if the extracted starch liquid continues to be processed by the traditional process, a large amount of starch organic matter will be ineffectively consumed in the water treatment process, which will not only increase the burden of water treatment, but also increase the processing cost.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a technology for processing starch-like organic matter extracted from waste paper pulp by using microbial fuel cell technology, to overcome the characteristics of modified starch, especially cationic starch, with low saccharification rate and difficult degradation, and to improve The saccharification rate of starch-like substances was improved, and the influence of modified functional group residues after saccharification on MFC treatment and conversion efficiency was overcome.

A new method for microbial fuel cell treatment of starch substances extracted from waste paper pulp, including two steps of biological enzyme saccharification and microbial fuel cell purification treatment, wherein the enzymes used in the saccharification step are α-amylase, β-amylase, endocut Combination enzymes of cellulase and cyclodextrinase or pullulanase. The dosage of a-amylase is 0-25U/100g starch organic matter, the dosage of β-amylase is 5-50U/100g starch organic matter, the dosage of cyclodextrinase is 0-5U/500g starch organic matter, and the pullulanase is The dosage of 0-5U/500g starch organic matter and endo-cellulase is 500-50000U/ton of waste liquid. The combined enzyme is added to the extracted waste liquid containing starch organics, and is maintained at a certain temperature and pH for a certain period of time to carry out saccharification treatment. After the treatment, the turbidity of the waste liquid is controlled below 10-50 NTU before entering the microbial fuel cell treatment step.

For the starch liquid extracted from waste paper raw materials contains a small amount of fine fibers, endo-cellulase is used to degrade the fine components, so as to avoid the adsorption of fine fibers on the ionic membrane and block the ionic membrane. And different from other saccharification processes, the turbidity index is used to control the saccharification effect, which is used to indicate the degradation effect of starch fragments and fine fibers. Impurities such as semi-fibrous fragments.

In addition to the hydrolysis of amylopectin, the addition of cyclodextrinase or pullulanase has another main effect on the hydrolysis of structurally isomeric oligosaccharides caused by starch modified functional group residues. The structure of functional group residues is similar to that of normal starch. Different glycosyl groups in the molecule often lead to structural heteromorphism of oligosaccharide fragments and affect the function of saccharification enzymes. Using cyclodextrinase or pullulanase to effectively degrade isomeric/isomorphic oligosaccharide fragments can greatly improve the efficiency of saccharification. In the study, it was found that the saccharification rate of double-enzymatic saccharification (ie: amylase + saccharification) was only 70%-82% for starch organics extracted from waste paper, and the saccharification rate of cyclodextrinase or pullulanase was added. It can be improved by 15-22 percentage points to 92%-99%.

The source and structure of starch are the keys to determine its saccharification performance, and the saccharification performance is also the key to determine its power conversion efficiency. The ratio of amylose to amylopectin in starch determines the physical and chemical properties of starch, especially the saccharification rate. In addition, in the papermaking industry, the amount of natural starch used in papermaking auxiliaries is very small, and most of them are various modified/modified starches. Different modified starches have different enzymatic decomposition properties due to different structures. Among them, acetate starch, phosphoric acid Ester starches such as ester starch have higher decomposition performance and are easier to be enzymatically decomposed into monosaccharide substances, followed by oxidized starch, and cationic starch is the most difficult to enzymatically decompose. In the starch industry, about 70% of cationic starch products are currently used as papermaking auxiliaries, and in the papermaking industry, cationic starch is the mainstream papermaking auxiliaries, accounting for the largest proportion among various modified starches. Cationic starch is the most difficult to enzymatically hydrolyze, and its saccharification ratio is the main factor affecting the conversion of starch to electrical energy, and it will also have a great impact on the purification effect of starch extraction wastewater. Therefore, this patent uses different enzyme combinations for the saccharification of various types of modified starch, especially cationic modified starch, in order to improve its saccharification and subsequent wastewater purification effect.

The microbial fuel cell is divided into an anode chamber and a cathode chamber. The anode chamber and the cathode chamber are separated by an ion membrane. The anode chamber is metered into the saccharified starch by a peristaltic pump to extract the saccharified liquid. Bacteria, the anode chamber is fed with _N2 for stirring; ionic liquid is used in the cathode chamber, and a moderate amount of air is introduced into it to supplement dissolved oxygen.

The amount of nitrogen in the anode area is controlled at 1:0.05-0.25, and the amount of activated sludge is 0.10-3.0g/L; the anode is made of carbon fiber material, which can be in the form of carbon fiber rods, carbon fiber surfaces formed by expanding carbon fiber fabrics, Or a cylinder made of fiber cloth, and the carbon material electrodes are connected to the outside through copper wires. The glucose concentration of the saccharification solution in the anode area is controlled at 1500-6000 mg/L. The pH of the anode area is controlled at 4.5-7.2.

The cathode area was filled with 0.2mol/L disodium hydrogen phosphate-potassium dihydrogen phosphate buffer solution (pH 6.0), a stainless steel mesh was used as the cathode electrode, and 1:0.02-0.10 air was filled to supplement dissolved oxygen.

The treatment temperature is 5-35°C, preferably 20-35°C.

Different from natural starch saccharification solution, starch derived from waste paper pulp is mostly various modified starches, which contain a large number of functional group residues. Some functional group residues are toxic to anaerobic microorganisms and affect the conversion effect of batteries. Aiming at this characteristic of the raw material, the present invention adopts the sequence batch culture mode to cultivate and domesticate suitable microbial sludge. The microbial sludge cultured by sequencing batch is a facultative sludge with high bacterial activity and better stability than anaerobic bacteria, and is more suitable for the treatment of saccharification solution containing functional group residues. In the study, it was found that the conversion efficiency of anaerobic sludge and facultative sludge was not much different with glucose as the carbon source, and the anaerobic sludge was higher. The conversion efficiency of sludge decreased significantly, by 15%-22%, while the facultative sludge only decreased by 2%-5% when the starch saccharification solution was extracted from starch waste paper as the carbon source, and the conversion efficiency was higher than that of anaerobic sludge. 10%-15% higher. In addition, the facultative sludge has good stability and is easy to cultivate, which is adopted in this aspect for the characteristics of extracting starch saccharification liquid from waste paper.

The use of MFC to treat industrial wastewater has been developed for many years, but the microbial systems of different wastewater batteries are very different, and anaerobic microorganisms are mainly used in the treatment. Anaerobic microorganisms have poor stability, and are sensitive to better aerobic microorganisms. The modification processes of starch-based organic compounds from waste paper are very different. Different modification methods have various functional groups. After saccharification, these modified functional groups remain. Radicals tend to have a greater impact on the metabolism of some microorganisms, especially some cationic modified residue groups such as amines, ammonium and other nitrogen atoms, which are more toxic to microorganisms. Anaerobic microorganisms grow slowly and are sensitive to pollutants. In view of the characteristics of starch organic matter derived from waste paper, the present invention adopts the SBR domestication method to adjust the structure of the microbial flora to construct a facultative microbial flora suitable for MFC treatment. For the conversion of starch saccharification liquid containing various functional group residues.

Advantages and beneficial effects of the present invention:

The saccharification rate (calculated by glucose) of the starch substances of the present invention is 92%-99%, the voltage between the anode and the cathode of the MFC experimental device (100ml capacity of the anode and the cathode chamber) is between 50-500mV, and the current is 0.01-0.10mA between. The removal rate of CODcr in 24 hours is 45%-86%.

Detailed ways

The present invention will be further described in detail below through specific examples. The following examples are only descriptive, not restrictive, and cannot limit the protection scope of the present invention.

Example 1:

The starch-containing organic matter extraction waste liquid extracted from domestic waste paper box raw materials to produce corrugated base paper waste pulp is used as raw material. After saccharification, MFC is used to purify and convert electric energy. The starch extraction rate is 7% (relative to waste paper box raw materials) .

The saccharification process uses an enzyme-enzyme combination as:

a-amylase: the dosage is 5U/100g starch organic matter; β-amylase dosage is 15U/100g, pullulanase (pullulanase @ Novozymes) is 5U/500g starch organic matter, endo-cellulose The enzyme dosage is 5000U/ton of the waste liquid.

Saccharification conditions: 50°C, pH 6.5 (natural pH of the extract), treatment for 24 hours; the turbidity of the waste liquid after treatment is 12 NTU, which is used as the raw material for MFC treatment.

In the microbial fuel cell, the anode chamber and the cathode chamber are separated by an ionic membrane (membrane dedicated to the desalination EDI module). Oxygen culture activated sludge is used as microbial cells, and N ₂ is introduced into the anode chamber for stirring; ionic liquid is used in the cathode chamber, and a moderate amount of air is introduced into it to supplement dissolved oxygen.

The amount of nitrogen in the anode area is controlled at 1:0.1, and the amount of activated sludge is 2.5g/L; the anode is made of carbon fiber material, and the cylinder made of fiber cloth is used as the anode, and the diameter of the cylinder is 50% of the diameter of the anode chamber. The material electrodes are connected to the outside through copper wires. The pH of the anode zone was controlled at 6.5.

The cathode area was filled with 0.2mol/L disodium hydrogen phosphate-potassium dihydrogen phosphate buffer solution (pH 6.0), a stainless steel mesh was used as the cathode electrode, and 1:0.05 air was filled to supplement dissolved oxygen. The treatment temperature was 30°C.

Under this condition, the starch saccharification rate (calculated as glucose) is 95%, the voltage between the anode and the cathode of the MFC experimental device (100ml capacity of the anode and the cathode chamber) is the highest between the anode and the cathode, and the current is between 0.025mA. The removal rate of CODcr in 24 hours was 76%.

Example 2:

The starch-containing organic matter extraction waste liquid extracted from domestic waste paper box raw materials + 20% imported waste paper boxes from Russia to produce corrugated base paper waste pulp is used as raw material. After saccharification, MFC is used for purification and power conversion, and the starch extraction rate is 6.5%. (relative to waste carton raw material).

The saccharification process uses an enzyme-enzyme combination as:

a-amylase: the dosage is 15U/100g starch organic matter; β-amylase dosage is 15U/100g, cyclodextrinase is 2U/500g starch organic matter, and endocellulase dosage is 2500U/ton of waste liquid.

Saccharification conditions: 50°C, pH 6.8 (natural pH of the extract), treatment for 24 hours; the turbidity of the waste liquid after treatment is 22 NTU, which is used as the raw material for MFC treatment.

In the microbial fuel cell, the anode chamber and the cathode chamber are separated by an ionic membrane (special membrane for desalination EDI module). Oxygen culture activated sludge is used as microbial cells, and N ₂ is introduced into the anode chamber for stirring; ionic liquid is used in the cathode chamber, and a moderate amount of air is introduced into it to supplement dissolved oxygen.

The amount of nitrogen in the anode area is controlled at 1:0.2, and the amount of activated sludge is 3.0g/L; the anode is made of carbon fiber material, and the cylinder made of fiber cloth is used as the anode, and the diameter of the cylinder is 60% of the diameter of the anode chamber. The material electrodes are connected to the outside through copper wires. The pH of the anode zone was controlled at 6.5.

The cathode area was filled with 0.2mol/L disodium hydrogen phosphate-potassium dihydrogen phosphate buffer solution (pH 6.0), a stainless steel mesh was used as the cathode electrode, and 1:0.07 air was filled to supplement dissolved oxygen. The treatment temperature was 30°C.

Under this condition, the starch saccharification rate (calculated as glucose) was 92%, the voltage between the anode and the cathode of the MFC experimental device (anode and cathode chambers were 100ml each) was up to 205mV, and the current was between 0.028mA. The removal rate of CODcr in 24 hours was 62%.

Example 3:

The starch-containing organic matter extraction waste liquid extracted from domestic waste paper box raw materials to produce corrugated base paper waste pulp is used as the raw material. After saccharification, MFC is used to purify and convert electric energy. The starch extraction rate is 7.2% (relative to the waste paper box raw material) .

The saccharification process uses an enzyme-enzyme combination as:

a-amylase: the dosage is 0U/100g starch organic matter; β-amylase dosage is 25U/100g, pullulanase (pullulanase @ Novozymes) is 15U/500g starch organic matter, endo-cellulose The dosage of enzyme is 500U/ton of waste liquid.

Saccharification conditions: 50°C, pH 6.5 (natural pH of the extract), treatment for 24 hours; the turbidity of the waste liquid after treatment is 15 NTU, which is used as the raw material for MFC treatment.

In the microbial fuel cell, the anode chamber and the cathode chamber are separated by an ionic membrane (special membrane for desalination EDI module). Oxygen culture activated sludge is used as microbial cells, and N ₂ is introduced into the anode chamber for stirring; ionic liquid is used in the cathode chamber, and a moderate amount of air is introduced into it to supplement dissolved oxygen.

The amount of nitrogen in the anode area is controlled at 1:0.2, and the amount of activated sludge is 2.5g/L; the anode is made of carbon fiber material, and the cylinder made of fiber cloth is used as the anode, and the diameter of the cylinder is 50% of the diameter of the anode chamber. The material electrodes are connected to the outside through copper wires. The pH of the anode zone was controlled at 6.5.

The cathode area was filled with 0.2mol/L disodium hydrogen phosphate-potassium dihydrogen phosphate buffer solution (pH 6.0), a stainless steel mesh was used as the cathode electrode, and 1:0.10 air was filled to supplement dissolved oxygen. The treatment temperature was 30°C.

Under this condition, the starch saccharification rate (calculated as glucose) was 97%, the voltage between the anode and the cathode of the MFC experimental device (each 100ml capacity of the anode and the cathode chamber) was up to 280mV, and the current was between 0.031mA. The removal rate of CODcr in 24 hours was 85%.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the inventive concept, several modifications and improvements can be made, which belong to the present invention. protected range.

Claims (5)

1. A novel method for treating starch substances extracted from waste paper pulp by a microbial fuel cell is characterized by comprising two steps of biological enzyme saccharification and microbial fuel cell purification treatment, wherein the enzyme adopted in the saccharification step is a combined enzyme consisting of a-amylase, β -amylase, endo-cellulase and cyclodextrin enzyme or pullulanase.

2. The method as claimed in claim 1, wherein the amount of the alpha-amylase is 0-25U/100g of the starch-based organic substance, the amount of the β -amylase is 5-50U/100g of the starch-based organic substance, the amount of the cyclodextrin enzyme is 0-5U/500g of the starch-based organic substance, the amount of the pullulanase is 0-5U/500g of the starch-based organic substance, and the amount of the endo-cellulase is 500-50000U/ton of the discharged waste liquid.

3. The method according to claim 1 or 2, characterized in that: adding the combined enzyme into the waste liquid containing starch organic matters, keeping the temperature at 50 ℃ and pH6.5-6.8 for 24h, carrying out saccharification treatment, controlling the turbidity of the treated waste liquid to be below 10-50NTU, and then entering a microbial fuel cell treatment step.

4. The method of claim 1, wherein: pumping saccharification liquid into an anode chamber of the microbial fuel cell by a peristaltic pump, controlling the glucose concentration of the saccharification liquid at 1500-₂Stirring, adopting intermittent aerobic culture activated sludge as microbial thallus, wherein the inoculation amount of the activated sludge is 0.10-3.0g/L, the pH value of an anode region is controlled at 4.5-7.2, and the anode adopts a carbon fiber material; in the cathode chamber, disodium hydrogen phosphate-potassium dihydrogen phosphate buffer solution is used as ionic liquid, a small amount of air is introduced, the cathode adopts a stainless steel net as an electrode, and the treatment temperature is 5-35 ℃.

5. The method of claim 4, wherein: the culture conditions of the intermittent aerobic culture activated sludge are as follows: taking an extracting solution with the extracted starch content of 0.5-1.0% as a raw material, taking sludge of a municipal sewage treatment plant as seed sludge, taking treatment solution with the inoculation amount of 0.1-0.5% of the system volume at regular time every day, and supplementing the extracting solution with the system volume of 25-30%; aeration is carried out for 2-3 hours every 24 hours, aeration is carried out for 0.5-0.75 hour every 6 hours, and the system SV 30: 15-35 percent, continuously culturing for more than 15 days, taking out a proper amount of sludge, washing twice by using tap water, and inoculating the sludge serving as the activated sludge for intermittent aerobic culture to the anode chamber of the cell.