Composite coagulant for landfill leachate treatment and preparation method thereof

Abstract

The present application relates to the field of environmental management technology, and more particularly to a composite coagulant for landfill leachate treatment and a preparation method thereof.The composite coagulant comprises inorganic coagulant, organic flocculant and nano coagulant aid; the inorganic coagulant is a mixture of polymeric aluminum ferric silicate and basic aluminum chloride; the organic flocculant is polydimethyl diallyl ammonium chloride; and the nano coagulant aid is a mixture of nano calcium oxide, nano ferric oxide and activated carbon.The composite coagulant has the characteristics of high efficiency in removing solid suspended matter and soluble organic matter in water, fast precipitation speed, one-step flocculation and sedimentation, formation of stable flocculation large particles in sewage, and effective reduction of the load of subsequent leachate treatment equipment.

Description

Technical Field

[0001] This invention relates to the field of environmental remediation technology, and in particular to a composite coagulant for landfill leachate treatment and its preparation method. Background Technology

[0002] Landfill leachate is a high-concentration, difficult-to-treat organic wastewater generated during the processes of landfilling, sorting, compression, landfilling, and fermentation. It primarily originates from the water contained within the landfill itself, water produced by the biochemical reactions of the landfill, and atmospheric precipitation. It is characterized by complex pollutant composition, high concentration, and high levels of heavy metal ions, making treatment extremely challenging. In urban sewage and wastewater, landfill leachate has consistently been a major obstacle to urban ecological environment construction and a recognized problem in the water treatment industry. Currently, most landfill leachate treatment in my country employs a combination of biological and membrane treatment processes. This combination effectively addresses the problems of landfill leachate, significantly reducing the concentration of organic pollutants in the leachate with high efficiency in a short time and noticeably improving the biodegradability of the wastewater. Although membrane-based advanced treatment processes for leachate can achieve effluent standards, these processes suffer from high operating and maintenance costs and difficulties in treating membrane concentrate. For leachate, non-membrane advanced treatment processes mainly include adsorption, coagulation and sedimentation, advanced oxidation, and coupled processes. Coagulation and sedimentation is an important physicochemical treatment method in water treatment. It serves not only as a pretreatment step in the biological treatment of landfill leachate but is also widely used in the advanced treatment of leachate. Coagulation and sedimentation involves adding coagulants to destabilize colloids. The destabilized colloids and particles then aggregate to form large flocs, separating pollutants from the water. Coagulants can be mainly divided into inorganic coagulants and organic flocculants. Inorganic coagulants, when used alone, can lead to problems such as high dosage requirements, large amounts of sludge production, significant pH changes in the water, and residual metals in the treated effluent. Organic flocculants, when used alone, may leave residual organic monomers during coagulation, potentially harming organisms, and may also react with other pollutants in the water to form harmful byproducts. Both inorganic and organic coagulants have their drawbacks when used alone and cannot achieve satisfactory coagulation results. Therefore, the research and application of composite coagulants has gradually become a hot topic in recent years. The type of coagulant directly affects the mechanism of coagulation, making it a crucial factor influencing the process. The dosage of coagulant also significantly impacts coagulation effectiveness. The surface charge of coagulants varies considerably across different pH systems, with the negative charge of colloidal particles typically increasing with increasing pH. The solubility, hydrolysis rate, and precipitation form of inorganic coagulants are all affected by solution pH. Water temperature also influences coagulation effectiveness; under suitable temperatures, the optimal coagulant dosage generally increases as the temperature decreases. Summary of the Invention

[0003] The purpose of this invention is to provide a composite coagulant for landfill leachate treatment and its preparation method. The invention features a unique formulation combining carefully selected inorganic coagulants, high-efficiency organic polymeric flocculants, and nano-coagulant aids. These components, through meticulous formulation, form a composite system with highly efficient coagulation and sedimentation capabilities and strong adsorption capacity. Compared with traditional coagulants, this invention offers advantages such as high treatment efficiency and low dosage.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a composite coagulant for landfill leachate treatment and its preparation method.

[0006] The present invention provides a composite coagulant for landfill leachate treatment, wherein the mass percentage of each component in the composite coagulant is: 70% to 85% inorganic coagulant, 10% to 30% organic flocculant, and 1% to 5% nano coagulant aid; the sum of the mass percentage content of the above components is 100%.

[0007] The inorganic coagulant is a mixture of polyaluminum ferric silicate and basic aluminum chloride, wherein the mass percentage of the two components in the inorganic coagulant is: 50% to 80% polyaluminum ferric silicate and 20% to 50% basic aluminum chloride.

[0008] The organic flocculant is polydimethyldiallylammonium chloride.

[0009] The nano-coagulant is composed of nano-calcium oxide, nano-ferric oxide, and activated carbon. The mass percentages of each component in the nano-coagulant are as follows: nano-calcium oxide 37%–50%, nano-ferric oxide 0.5%–3%, and activated carbon 47%–60%. The particle size of the nano-calcium oxide is 50 nm–200 nm, and the particle size of the nano-ferric oxide is 50 nm–100 nm.

[0010] This invention uses a mixture of inorganic coagulant, organic flocculant and nano-coagulant to formulate a composite coagulant. Through synergistic effect, the composite coagulant can efficiently remove suspended solids and soluble organic matter in water, with fast sedimentation speed, achieving flocculation and sedimentation in one step. It can form stable large floc particles in sewage, effectively reducing the load on subsequent leachate treatment equipment.

[0011] This invention provides a method for preparing a composite coagulant for landfill leachate treatment, comprising the following steps: (1) accurately weighing nano-calcium oxide and nano-ferric oxide according to the formula, adding them to a certain amount of water, and stirring vigorously at 800-1200 r / min for 30-40 minutes to obtain a uniform suspension; (2) accurately weighing activated carbon according to the formula, adding it to the solution in (1), and stirring continuously for 30-50 minutes; (3) accurately weighing polydimethyldiallyl ammonium chloride according to the formula and adding it to the solution in (2) which is being stirred thoroughly, and stirring continuously for 20-30 minutes; (4) accurately weighing polyaluminum ferric silicate and basic aluminum chloride according to the formula, adding them to the solution in (3) which is being stirred thoroughly, and stirring continuously for 30-50 minutes to obtain a composite coagulant. Detailed Implementation

[0012] This invention provides a composite coagulant for landfill leachate treatment, comprising an inorganic coagulant, an organic flocculant, and a nano-coagulant aid; the inorganic coagulant is a mixture of polyaluminum ferric silicate and basic aluminum chloride; the organic flocculant is polydimethyldiallylammonium chloride; and the nano-coagulant aid is a mixture of nano-calcium oxide, nano-ferric oxide, and activated carbon.

[0013] The preferred mass percentage of each component in the composite coagulant provided by the present invention is: 70%–80% inorganic coagulant, 10%–20% organic flocculant, and 1%–5% nano-coagulant aid; more preferably, 75%–80% inorganic coagulant, 15%–20% organic flocculant, and 1%–5% nano-coagulant aid; the sum of the mass percentage content of the above components is 100%.

[0014] The composite coagulant provided by this invention includes an inorganic coagulant, an organic flocculant, and a nano-coagulant aid. In this invention, the inorganic coagulant is a mixture of polyaluminum ferric silicate and basic aluminum chloride, wherein the mass percentage of the two components in the inorganic coagulant is: 50%–80% polyaluminum ferric silicate and 20%–50% basic aluminum chloride; preferably 60%–80% polyaluminum ferric silicate and 20%–40% basic aluminum chloride, more preferably 70%–80% polyaluminum ferric silicate and 20%–30% basic aluminum chloride.

[0015] In this invention, the nano-coagulant is a mixture of nano-calcium oxide, nano-ferric oxide, and activated carbon; the preferred mass percentage of each component in the nano-coagulant is: 38%–48% nano-calcium oxide, 1%–2% nano-ferric oxide, and 50%–60% activated carbon, more preferably 45%–50% nano-calcium oxide, 1%–2% nano-ferric oxide, and 55%–60% activated carbon.

[0016] The composite coagulant of this invention consists of an inorganic coagulant, an organic coagulant, and a nano-coagulant aid. The inorganic coagulant rapidly forms flocs and accelerates sedimentation through the strong charge neutralization of colloidal substances, the excellent bridging and adsorption of suspended solids in water by hydrolysis products, and the selective adsorption of dissolved substances. The organic coagulant, polydimethyldiallyl ammonium chloride, combines with suspended solids and ions in water to form macromolecular complexes, accelerating the sedimentation of suspended solids and ions, making wastewater clear and transparent. It also neutralizes the charge in water, reduces surface tension, and promotes water flow. The nano-coagulant aid works synergistically with the organic flocculant to rapidly remove suspended solids and colloids from water, while also reducing the impact of organic matter on water quality, significantly improving water quality and reducing treatment time.

[0017] The present invention provides a method for preparing a composite coagulant for landfill leachate treatment as described in the above scheme, comprising the following steps: (1) accurately weighing nano-calcium oxide and nano-ferric oxide according to the formula, adding them to a certain amount of water, and stirring vigorously at 800-1200 r / min for 30-40 minutes to obtain a uniform suspension; (2) accurately weighing activated carbon according to the formula, adding it to the solution in (1), and stirring continuously for 30-50 minutes; (3) accurately weighing polydimethyldiallyl ammonium chloride according to the formula and adding it to the solution in (2) which is being stirred thoroughly, and stirring continuously for 20-30 minutes; (4) accurately weighing polyaluminum ferric silicate and basic aluminum chloride according to the formula, adding them to the solution in (3) which is being stirred thoroughly, and stirring continuously for 30-50 minutes to obtain a composite coagulant.

[0018] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0019] The following detailed description, in conjunction with embodiments, of the composite coagulant for landfill leachate treatment and its preparation method provided by the present invention, should not be construed as limiting the scope of protection of the present invention. Example 1

[0020] Weigh 2 g of nano-calcium oxide and 0.5 g of nano-ferric oxide and add them to 1000 ml of water. Stir vigorously at 800-1200 r / min for 40 minutes to obtain a uniform suspension. Weigh 2.95 g of activated carbon and add it to the above suspension. Stir continuously for 40 minutes to obtain a nano-coagulant suspension. Weigh 20 g of dimethyl diallyl ammonium chloride and add it to the nano-coagulant that is being stirred thoroughly. Stir continuously for 30 minutes. Weigh 60 g of polyaluminum ferric silicate and 15 g of basic aluminum chloride and add them to the mixed solution that is being stirred thoroughly. Stir continuously for 50 minutes to obtain a composite coagulant. Example 2

[0021] Weigh 2 g of nano-calcium oxide and 0.5 g of nano-ferric oxide and add them to 1000 mL of water. Stir vigorously at 800–1200 r / min for 40 minutes to obtain a uniform suspension. Weigh 2.95 g of activated carbon and add it to the above suspension. Stir continuously for 40 minutes to obtain a nano-coagulant suspension. Weigh 17 g of dimethyl diallyl ammonium chloride and add it to the nano-coagulant that is being stirred thoroughly. Stir continuously for 30 minutes. Weigh 62.4 g of polyaluminum ferric silicate and 15.6 g of basic aluminum chloride and add them to the mixed solution that is being stirred thoroughly. Stir continuously for 50 minutes to obtain a composite coagulant. Example 3

[0022] Weigh 1.2 g of nano-calcium oxide and 0.3 g of nano-ferric oxide and add them to 1000 mL of water. Stir vigorously at 800–1200 r / min for 40 minutes to obtain a uniform suspension. Weigh 1.77 g of activated carbon and add it to the above suspension. Stir continuously for 40 minutes to obtain a nano-coagulant suspension. Weigh 17 g of dimethyl diallyl ammonium chloride and add it to the nano-coagulant that is being stirred thoroughly. Stir continuously for 30 minutes. Weigh 64 g of polyaluminum ferric silicate and 6 g of basic aluminum chloride and add them to the mixed solution that is being stirred thoroughly. Stir continuously for 50 minutes to obtain a composite coagulant.

[0023] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite coagulant for landfill leachate treatment, characterized in that, The composite coagulant comprises inorganic coagulant, organic flocculant and nano coagulant aid; the inorganic coagulant is a mixture of polymeric aluminum ferric silicate and basic aluminum chloride; the organic flocculant is polydimethyl diallyl ammonium chloride; the nano coagulant aid is a mixture of nano calcium oxide, nano magnetite and activated carbon; The preparation method of the composite coagulant for treating landfill leachate comprises the following steps: (1) accurately weighing nano calcium oxide and nano magnetite according to the formula, adding a certain amount of water, and stirring at a high speed of 800-1200 r / min for 30-40 minutes to obtain a uniform suspension; (2) accurately weighing activated carbon according to the formula, adding to the solution prepared in step (1), and continuously stirring for 30-50 minutes; (3) accurately weighing polydimethyl diallyl ammonium chloride according to the formula, adding to the product prepared in step (2) under continuous stirring, and continuously stirring for 20-30 minutes; (4) accurately weighing polymeric aluminum ferric silicate and basic aluminum chloride according to the formula, adding to the product prepared in step (3) under continuous stirring, and continuously stirring for 30-50 minutes to obtain the composite coagulant.

2. The composite coagulant for treating landfill leachate according to claim 1, characterized by, The mass percentage of each component in the composite coagulant is: inorganic coagulant 70-85%, organic flocculant 10-30%, and nano coagulant aid 1-5%; the sum of the mass percentage of the above components is 100%.

3. The composite coagulant for treating landfill leachate according to claim 1, characterized by, The mass percentage of the two components in the inorganic coagulant is: polymeric aluminum ferric silicate 50-80% and basic aluminum chloride 20-50%; the mass percentage of each component in the nano coagulant aid is: nano calcium oxide 37-50%, nano magnetite 0.5-3%, and activated carbon 47-60%; the particle size of the nano calcium oxide is 50-200 nm, and the particle size of the nano magnetite is 50-100 nm.