106results about How to "Fast decolorization" patented technology

A decoloring ink for ink jet printing containing an Monascus pigment. An inclusion of an Monascus pigment enables printed characters and / or images to be preserved as long as they are kept in the dark, but they are quickly decolored on exposure to visible light and / or ultraviolet light when they are no longer needed.

The invention provides a quinoline bis-spirnaphthoxazine photochromic compound and a preparation method thereof, which relate to organic photochromic materials. The compound has a general chemical structural formula, wherein R1 is equal to CH3 in the formula. The preparation method of the quinoline bis-spirnaphthoxazine photochromic compound includes steps: (1), synthesis of 6-oxyquinoline; (2), synthesis of 5-nitroso-6-oxyquinoline; (3), synthesis of 5-nitroso-6-oxyquinoline metal complex; and (4), synthesis of the quinoline bis-spirnaphthoxazine photochromic compound. The preparation method of the compound is simple and is low in preparation cost, and the compound has better endurance and color, wider application range and higher productivity as compared with an existing spirooxazine photochromic compound.

The invention discloses a device for producing regenerated white cotton of colored cotton textile and its process, where there are two parallel reaction cylinders, there are top and bottom crosswise communicating tail gas pipes on the two reaction cylinders, and each tail gas pipe is installed with a valve, a flow meter and a vacuum pump; there is a UV lamp arranged in each reaction cylinder; another flow meter is installed on each air inlet pipe, and a pressure meter and another vacuum pump are installed on each air outlet pipe; the production process is: firstly humidifying the colored cotton textile to be processed, by steam, to make the water content of the colored cotton textile at 10-25%; making prophase decoloring treatment on the humidified cotton textile by ozone at a concentration of 5-25%; synchronously performing late UV decoloring treatment on the treated cotton textile in an ozone-containing environment to make the cotton textile turn white; and finally making cotton opening treatment on the white cotton textile to make the regenerated white cotton. The invention has the characters of simple process, high production efficiency, no pollution, no damage to cotton spinning material, saving water resources, and safety and reliability in production.

The invention discloses a method utilizing small-molecule diketone to serve as optical active agent for oxidation treatment of dye waste water and belongs to the field of dye waste water treatment. The method comprises the steps: filtering the dye-containing waste water to remove suspended matter; adding a small-molecule diketone compound to the dye-containing water body, and evenly mixing; and placing the dye-containing water body under an ultraviolet source to perform irradiation until dyes are decolorized. The method initially determines the structural characteristics of diketone capable of serving as the dye-decolorizing optical active agent: the molecular configuration is in a chain shape, and molecules are small. The dye-decolorizing method based on diketone is based on a reaction induced by ultraviolet light, can achieve efficient decoloration of various dyes, and has remarkably higher decoloration efficiency than a traditional UV / H2O2 method. Besides, the decoloration efficiency is not subjected to influence of coexistent alcohol in the water body, simultaneously the acid environment is favorable for promoting the reaction, and accordingly the method has more obvious advantages in the acid water body. The method has an autoacceleration performance in degrading the dyes, and the degradation speed is improved along with proceeding of the reaction.

The invention discloses a preparation method and an application of hydrophobization beta-cyclodextrin cation polyelectrolyte. In a water phase, three monomers, namely polymerizable beta-cyclodextrin derivatives, acryloyl oxyethyl trimethyl ammonium chloride and styrene, are subjected to a free radical copolymerization reaction under an oxidation / reduction (potassium peroxodisulfate / sodium hydrogen sulphite) initiating system to obtain the hydrophobization beta-cyclodextrin cation polyelectrolyte product. The hydrophobization beta-cyclodextrin cation polyelectrolyte product is white powder solids and is stable in structure and convenient to store and transport, hydrophilcity is reduced and better solubility is still maintained; the preparation method of the hydrophobization beta-cyclodextrin cation polyelectrolyte product is simple, and low in energy consumption; no other auxiliaries such as a surface active agent is added in an aqueous solution polymerization process, and environmental pollution is less; and the hydrophobization beta-cyclodextrin cation polyelectrolyte product can serve as a novel flocculating agent for decoloration, the specific structure of beta-cyclodextrin (beta-CD) is reserved, toxicity and cost are low, flocculation capacity is strong, decoloration speed is high, an applicable pH range is wider (2-12), and salt tolerance is high.

The invention provides aqueous degradable environment-friendly ink for printing, a special decoloring agent and a preparation method of the ink. The degradable environment-friendly ink contains dye, wherein the dye is azo-dye or triphenylmethane dye, or macromolecular dye synthesized by one of azo-dye or triphenylmethane dye, and aqueous macromolecular material. The preparation method of the degradable environment-friendly ink comprises the steps of dispersing, grinding and filtering aqueous acrylic resin, dye, de-ionized water, an antifoaming agent, a flatting agent, surfactant and amine materials in a high-speed disperser and a sand mill in sequence. The special decoloring agent is sodium dithionite or 2Na2CO3.3H2O2. The ink has the advantages of environment friendliness, no harmfulness, good safety, stable performance and good printing effect. When waste papers is recycled, the ink can be decoloured quickly under the action of the matching decoloring agent, and therefore, the problems that organic solvent in the oily ink volatilizes, the waste paper is difficult to deink and sewage pollution is serious are solved.

The invention relates to a modified and high-efficiency multi-function decolorizer of titanium dioxide acid hydrolysis waste residue and a preparation method thereof. Acid hydrolysis waste residue containing titanium sulfate is successively and respectively added with sodium hydroxide, peroxide, waste acid and calcium and magnesium powder according to the weight rate of the materials, therefore, the acid hydrolysis waste residue containing titanium sulfate generates nanometer titanium dioxide by nutralization, hydrolysis and acidification; added ferrous iron and iron in the acid hydrolysis waste residue are dehydrated at the temperature of 100-200 DEG C, oxidized at the temperature of 400-500 DEG C and then generate polymerization ferrous sulfate after natural cooling, telomerization and aging. The organic pollutants in wastewater are rapidly degraded by nano TiO2 and directly converted into non-toxic and harmless CO2, H2O and inorganic matters. Without changing the pH value of original sewage, the coagulation speed is fast, alumen ustum is big, settlement is quick, and the decolorizer has the functions of decolorization, degerming, removing radioactive elements and heavy metal ions, reducing COD and BOD, small feeding amount and strong adaptability.

The invention relates to the technical field of wastewater treatment, and in particular discloses a wastewater treatment system for bioelectrocatalysis and photocatalysis contact oxidation coupling. The wastewater treatment system comprises a first tube body, a second tube body and a third tube body which are connected in sequence, wherein a liquid inlet hole is formed in the wall of the first tube body; a liquid outlet hole is formed in the third tube body; a biological cathode is arranged inside the first tube body; the biological cathode is connected with an external circuit; a biological anode is arranged inside the second tube body; the biological anode is connected with the external circuit; microorganisms are adhered to the surfaces of the biological anode and the biological cathode; the third tube body is internally provided with mixed packing and an ultraviolet lamp; the center of the mixed parking is a cavity; and the ultraviolet lamp is arranged inside the cavity. Due to reasonable arrangement of the structure and the spatial utilization of a biological membrane inside the mixed parking, dissolved oxygen can be utilized in the wastewater treatment system in a gradient manner, so that the problem that the dissolved oxygen cannot be precisely controlled when a micro oxygen technique is used is solved, and in addition, removal of azo dyes, intermediates and residual COD (Chemical Oxygen Demand) in wastewater by a biological membrane at a contact oxidation part is improved.

The invention relates to a method for decoloring biodiesel prepared from gutter oil. The method comprises the following steps: 1, preparing biodiesel from gutter oil through ester exchange; 2, decoloring: adding 100g of biodiesel to a 250ml flask, adding hydrogen peroxide which is 5-25% oil weight in mass percentage, wherein heating temperature is 70-90 DEG C, stirring, reacting for 18-25min, centrifuging and reserving an upper phase; 3, calculating a decolorization ratio: respectively adding the obtained grease in a 1.0cm cuvette, and implementing absorption spectrum scanning on 465nm, wherein the decolorization ratio is defined as a ratio of a difference in absorbance indexes before and after biodiesel decolorization to an absorbance index before decolorization. The method has the beneficial effects that the method, through a hydrogen peroxide oxidation process, has an obvious decolorization effect on deep-color biodiesel prepared from the gutter oil. And the decolorization method is simple to operate, high in decolorization speed and high in recovery efficiency, and the biodiesel decolorized by the method has no large difference with the biodiesel before decolorization in both physical and chemical property.

The invention discloses a cerium-doped lead dioxide electrode, and a preparation method and application thereof in the quick decolorization and efficient mineralization of basic dyes. The preparation method of the electrode comprises the following steps: etching a titanium plate into a titanium dioxide nanotube array base; filling a small amount of elemental copper into the titanium dioxide nanotube through electrodeposition; then, preparing a cerium-containing lead dioxide electrodeposition solution; and finally, preparing the cerium-doped lead dioxide electrode on the titanium dioxide nanotube array base through electrodeposition. When being used for treating waste water containing basic dyes, the prepared electrode can realize the quick decolorization and efficient mineralization of the basic dyes in the waste water. According to the cerium-doped lead dioxide electrode obtained in the invention, the catalytic activity and service life are greatly improved in comparison with an undoped lead dioxide electrode, and the water treatment cost based on an electrochemical method can be effectively reduced; no other additional chemical substances are introduced in the treatment process of the waste water containing the dyes, thereby avoiding secondary pollution; and the preparation method has mild reaction conditions and is simple to operate.

The invention discloses an acidic dye wastewater treatment agent, belonging to the field of sewage purification treatment. The treatment agent is prepared from polyaluminum chloride, ferrous sulfate, active silica, oxydol, activated carbon and chlorine dioxide. All the components are uniformly stirred and completely dissolved at room temperature. The application temperature is 4-60 DEG C. The acidic dye wastewater treatment agent is suitable for treating acidic sewage. The Fenton reagent composed of the ferrous sulfate and oxydol according to certain parts by weight is combined with the inorganic flocculant polyaluminum chloride to form the main component of the sewage treatment agent; by using the active silica as the assistant, the suspended substance are quickly settled under the synergistic actions of the Fenton reagent, main component and assistant; and the combination of the activated carbon and chlorine dioxide can implement quick disinfection, decolorization and sewage purification. The acidic dye wastewater treatment agent has the advantages of low treatment cost, no corrosiveness, no toxicity and no secondary pollution after treatment.

A process for treating the sewage containing azo dye includes such steps as regulating pH value to less than 2.5, adding iron powder, stirring for decolouring, and radiating by ultraviolet light for optical degradation. Its advantages are high speed and effect, and no secondary pollution.

The invention discloses an apparatus for treating refractory organic wastewater, particularly relates to an apparatus for degrading dye wastewater by using low-temperature plasma technique, and belongs to the field of wastewater treatment. The apparatus comprises an insulating medium pipe and an aerator, wherein the outer surface of the insulating medium pipe is covered with a low-voltage discharge electrode, and the aerator is arranged in the insulating medium pipe; the insulating medium pipe is provided with a gas outlet, a gas inlet, a water outlet and a water inlet, and a high-voltage discharge electrode is disposed in the aerator. The apparatus of the invention is simple in structure, simple to operate, good in discoloring effect and high in water treatment efficiency; through diffusion of the microporous aerator into a liquid, and a route at which plasma enters wastewater can be shortened. The reaction apparatus of the invention can discolor a dye fast and is effective in degrading the dye macromolecular organics in the dye, the obtained small-molecules provide enhanced macromolecular organics in the dye can be effectively degraded, small-molecular wastewater obtained provide enhanced biochemical properties for the wastewater, subsequent biological treatment is facilitated, the apparatus has unique advantages in the dye wastewater treatment process, and at certain voltage, and the apparatus is up to 98% in removal rate 10 minutes after.

This invention discloses an adhesive prepared from papermaking black liquor for activated carbon shaping. The adhesive comprises: black liquor concentrate 55-70 wt.%, adhesive material 10-20 wt.%, starch 5-10 wt.%, plant waste residue 10-20 wt.%, and surfactant 2-5 wt.%. The adhesive can substitute for the present adhesive made from coal tar, and can produce activated carbon product with adjustable frame porosity, abundant surface functional groups, high adsorption ability and high quality. The activated carbon product is suitable for advanced water treatment and deep-processing decolorization in food and fine chemical industries, and has such advantages as rapid adsorption, rapid decolorization and wide applications.

The invention discloses a preparation method of a decolorizing membrane for printing and dyeing wastewater. The decolorizing membrane is prepared from copper acetate monohydrate, sodium borate decahydrate, dopamine hydrochloride, 2-bromoisobutyryl bromide, nanometer titanium dioxide, hydrazine hydrate, chitosan, chloroacetic acid, silver nitrate, beta-cyclodextrin, polyacrylic acid and other raw materials. Obtained silver particles are loaded with the chitosan, the beta-cyclodextrin and the like for embedding, and a stable fiber membrane structure is formed by electrospinning and thermal crosslinking. The obtained fiber membrane is impregnated with grafted nano-titanium dioxide, a large number of active sites on the surface of the membrane are used for increasing the reaction contact surface with the wastewater, and then a layer of nano-copper membrane is impregnated and loaded with the copper acetate monohydrate. The process of a reduction reaction is accelerated by the characteristicof rapid electron conduction, and the dye decolorizing speed is increased, so that the obtained decolorizing membrane has high efficiency and high stability, and the defects of the traditional decolorization treatment of the printing and dyeing wastewater are overcome. The preparation method has significant application value in pollution control.

An embodiment of the present application provides an electrochromic device comprising an electrochromic element, wherein the electrochromic element enters a second state when a first voltage is applied to the electrochromic element in a state where the electrochromic element has a first state, and the electrochromic element enters a third state when the first voltage is applied to the electrochromic element in a state where the electrochromic element has a fourth state.

The invention discloses a preparation method for dihydrostreptomycin sulphate and belongs to the production preparation technology of semi-synthesis antibiotics. The method comprises the following steps: treating with acid; performing ion exchange; adsorbing with large-pore amino resin; hydrogenating; performing secondary ion exchange; purifying by a mixed bed; treating with activated carbon; concentrating through a nanofiltration membrane; decolorizing by activated carbon; and treating with an ultrafiltration membrane and performing spray drying. According to the invention, the dosage of oxalic acid in a preparation process is reduced, the use ratio of the reducing agent is increased, the production cost is lowered, the production efficiency is increased, the method can meet the industrial production requirement and the product purity, quality yield and total recovery of the dihydrostreptomycin sulphate are increased.

The invention discloses a deproteinization and decoloration method for a mango processing by-product polysaccharide. The method comprises the steps of pre-treating mango peel slag to prepare mango peel slag slurry; extracting crude polysaccharide by using an ultrasonic-assisted cellulose enzyme method; and carrying out deproteinization and decoloration on crude polysaccharide to obtain a mango polysaccharide semi-pure product. The crude polysaccharide is extracted by using the ultrasonic-assisted cellulose enzyme method, diffusional release of the polysaccharide can be accelerated by secondary vibration efficiency of an ultrasonic wave, the cell wall can be effectively broken through cellulose enzyme treatment, the yield of the polysaccharide is improved and the biological activity of the polysaccharide can be kept. A relatively good deproteinization effect can be obtained through deproteinization by adopting an optimized TCA-n-butyl alcohol method; and the deproteinized polysaccharide solution is decolored by adopting activated carbon, so that relatively high decoloration rate and polysaccharide retention rate can be obtained. The mango processing by-product is taken as a raw material, so that improvement of the additional value of the mango deep processing industry is facilitated and the environmental pollution is relived. The method is simple and fast; and compared with a traditional dry crushed sample pretreatment method, the extraction process is simplified and the production cost is reduced.

Belonging to the technical field of sewage treatment, the invention discloses a device and method for promoting rapid anthraquinone dye decolorization based on microbial fuel cell technology. The method is based on the combination of anaerobic sludge decolorization and bioelectrochemical treatment technology, a two-chamber microbial fuel cell system is constructed, electrogenesis bacteria and anaerobic sludge with decolorization function are added to the positive electrode, also glucose is added as a co-substrate to coordinate decolorization of the anthraquinone dye reactive brilliant blue KN-R, at the same time a culture solution is added as the nutrient to ensure the anaerobic environment of the positive electrode, air is introduced to the negative electrode to serve as the electron acceptor of the system, and the positive electrode and negative electrode are externally connected to a resistor to compose a loop. The device and method for rapid decolorization of anthraquinone dye provided by the invention have good effect, and have the advantages of small floor area, wide application range, simple equipment, easy operation, good treatment effect, energy recovery and the like, andcan be wide applied to biological treatment of sewage in the printing and dyeing industry and recovery of part electric energy, thus having good economic and environmental protection benefits.

This invention relates to a purification decoloration technique and process by ordinary aggregated alumina, the characters are: adding such as-reduced aluminum materials as aluminum crumbs to ordinary aggregated alumina solution, and heat it to a certain temperature. Through acid dissolution of alumina and the surface arrosion of metal aluminum, metal ion and organic impurities in oxidation reduction solution, the aim of purification and decoloration can be achieved, and its products can be used as precipitant in paper-making. The technique is simple, the decoloration speed is high, the efficiency is high, and it is easy to manipulate, the cost is low and can improve the qualities of aggregated alumina.

The invention discloses a wood modifier, which is prepared from the following components based on a preparation ratio: 1 part of 10-20% hydrogen peroxide solution and 1 part of mixed solution of 1-5% of sodium silicate and 0.1-0.5% sodium hydroxide. A sponge is used to dip the wood modifier, and press pressure and dosage are adjusted to coat the wood modifier so as to achieve the effect of decolorization and modification based on the different color shades of the parts to be processed of the wood floor. The invention has good decolorization and modification effects, improves the utilization rate of solid wood raw materials, lowers cost, maintains the visual effect consistency after the solid wood floor color is coated, and improves the solid wood floor quality.

The invention relates to an actinidia polygama effervescing agent and a preparation method and application thereof. The preparation method comprises the following steps: mixing the following components in parts by mass: 3-5 parts of an extracted active polysaccharide mixture, 24-30 parts of sodium bicarbonate, 15-20 parts of citric acid, 1-3 parts of an adhesive, 10-14 parts of xylitol, 4-6 parts of freeze-dried powder of filtrate obtained after actinidia polygama polysaccharide extraction and 2-5 parts of sodium alga acid, preparing a soft material, granulating, drying, pelletizing, and adding 30-50 parts of a juice clathrate compound, thereby obtaining the effervescing granules. According to the method, the process is simple, the active ingredients of the product are clear, the natural VC retention rate is over 70 percent, a xylitol formula system is adopted, and the effervescing agent is good in taste and is suitable for diabetes mellitus patients to take. The experiment proves that the actinidia polygama active polysaccharides and effervescing granules have a certain treatment effects on type II diabetes mellitus; and moreover, the effervescing agent can be widely applied to antioxidant, anti-fatigue and blood sugar-reducing foods and / or health products.

The invention relates to a method for decolorizing direct dye wastewater and particularly relates to an electrochemical decoloration method of direct dye wastewater. The method utilizes FTO glass as an anode material and carries out electrochemical decoloration of wastewater in an electrolytic cell. The fluorine-doped tin oxide conductive glass (FTO glass) is used as an anode material and has good light transmittance. If needed, a photocatalytic reagent can be simultaneously added to the waste liquid so as to realize photocatalytic and electrochemical decolorization at the same time so that decolorization effects are improved and energy consumption is reduced. The method has the advantages of significant decoloring effects, low chroma of the decolorized solution, good translucency and repeated use of the electrode, can realize quick decolorization of a direct dye and is conducive to environmental protection.

The invention relates to an oil purification device, in particular to an oil decoloring device. The oil decoloring device mainly contains an oil inlet pipe, an oil outlet pipe and a decoloring kettle, wherein the inlet and outlet of the decoloring kettle are connected with the oil inlet pipe and the oil outlet pipe in series; the inside of the decoloring kettle is provided with a decolorizer; and the decolorizer is used to decolor oil. The decoloring kettle is characterized in that the outlet is provided with a filter; and the decoloring kettle is connected with a condenser and a tail gas collection tank in series through pipes and can be used to collect the waste gas generated in the decoloring process. The oil decoloring device has simple process, high production efficiency and simple operation and can be used to perform continuous and fast decoloring treatment; and after decolored by the oil decoloring device, oil has higher combustion efficiency and low pollution.

Provided are preparation and application of a refined decolorizing agent and cleaning for edible oil. Composite available chlorine gas is obtained through a chlorate aqueous solution under the condition of taking inorganic acid or organic acid as an oxidation reductant, a secondary chemical reaction is conducted for adsorption through stabilizer carrier hydroxide and a silicon compound, and a granular composite finished product of the refined decolorizing agent is obtained through concentration, fluidized drying and granulation; particularly, acid reaction mother liquor is not taken as waste liquor to be discharged, and the reaction mother liquor is reused. The preparation and application of the refined decolorizing agent and cleaning for the edible oil can be used for animal and vegetable oil refined decolorizing and specially for edible oil refined decolorizing, and the industry can respond to the important contribution on the aspects of energy conservation and emission reduction provided by the country; the edible oil industry can save energy by over 80 percent, and discharge of the waste clay residue containing oil is reduced by 100 percent, and the preparation and application of the refined decolorizing agent and cleaning for the edible oil can be further used for other food and organic matter decolorizing. The product has important environmental and economic value, wide application and promotion prospects are achieved, and the product takes the leading position in the world.

The invention relates to a water purifying agent for rapid treatment of industrial wastewater and a preparation method thereof, wherein the water purifying agent comprises the following components inparts by weight: 20-35 parts of a nano diatomite powder / cellulose composite material, 5-10 parts of alkyl glycoside or derivative surfactant thereof, 60-75 parts of a flocculating agent and 2-6 partsof nitrifying bacteria. The water purifying agent prepared by the invention is simple in components and reasonable in proportion, does not contain heavy metal components in the formula, is mostly a natural compound, is an environment-friendly water purifying agent, and avoids secondary pollution to a water body; cellulose and diatomite powder are subjected to nanocrystallization and compounding, have huge specific surface area, can adsorb a large number of polluting organic matters, are fully mixed with specific contents of raw material components, and have the effects of rapid sedimentation,decolorization and COD removal; and alkyl glycoside or derivatives thereof are added, so that the water purifying agent has sterilization and disinfection effects on the water body, can effectively kill bacteria and microorganisms in the water body, and avoids water body pollution caused by mass propagation.

A novel coomassie brilliant blue staining method, a related fixative and a related staining agent are disclosed. The related fixative comprises an acid and an alcohol, wherein the alcohol is methanol and / or ethanol, and the acid is an acid mixture of acetic acid phosphoric acid in a volume ratio of 1:1. The related staining agent comprises 0.05-0.12% by mass / volume concentration of coomassie brilliant blue, 5-20 v% of an alcohol, 3-10 v% of an acid and 3-10 % by mass / volume concentration of ammonium sulfate. The method is characterized by better linearity, better mass spectrum compatibility, breakage-proof colloid, little background, reduction of nearly a half of agent using amounts, reduced staining cost, and capability of being more environmental friendly.

The invention discloses a pectin extraction method and, particularly, relates to an industrial production method of sunflower head low-ester pectin; the production method comprises the specific steps of blowing air in a sunflower head oven for drying, crushing, and screening; adding the screened sunflower head powder into weakly basic ethanol solution, adjusting pH, stirring, centrifuging, and washing with water until filtrate is colorless; adding tartrate into filter residue, adjusting solution pH with HCl, extracting, and filtering with a plate frame; diluting extract, and applying to serial ion exchange resin columns; collecting bottom injection, and spray-drying to obtain finished pectin. The pectin obtained herein is high in whiteness and purity, has high extraction rate and is suitable for large-scale production.

The invention discloses a lead dioxide electrode, a preparation method of the lead dioxide electrode and application of the lead dioxide electrode in treatment of reactive dyes. The electrode is prepared by grinding a titanium plate and performing alkaline washing, acid washing, electroplating and calcining. The reactive dyes are subjected to electrochemical treatment by utilizing the prepared modified lead dioxide electrode and by controlling factors such as current density, power-on time and the like under the constant current condition. Other chemical substances are not additionally introduced, secondary pollution cannot be caused, and the lead dioxide electrode and the preparation method of the lead dioxide electrode have the advantages of mild reaction condition, convenience in operation and the like. After the electrode is powered on, the reactive dyes can be effectively decolored in a short period and can be mineralized to a certain extent.

The invention provides a printing and dyeing wastewater purifying flocculating agent, and a printing and dyeing wastewater purifying application thereof. The flocculating agent meets the environmentally-friendly requirement, and has the technical advantages of excellent decolorizing and purifying effects, realization of fast decolorizing, and high purifying efficiency. The printing and dyeing wastewater purifying flocculating agent comprises a mixture of the following powdery components: N-carboxyethylchitosan, cationic starch and bentonite, wherein a mass ratio of the N-carboxyethylchitosan to the cationic starch is 2:(3-4), and a mass ratio of the bentonite to the N-carboxyethylchitosan is 5:(1-4). The invention provides the printing and dyeing wastewater purifying application of the flocculating agent. The flocculating agent has the advantages of natural degradability, non-toxicity, and low prices of above materials; and the decolorizing rate of the flocculating agent can reach 90% or above when the flocculating agent is mixed with wastewater for only 10 minutes.