CN-122012102-A - Method for preparing saline-alkali soil conditioner from sludge decomposed material and application of saline-alkali soil conditioner

CN122012102ACN 122012102 ACN122012102 ACN 122012102ACN-122012102-A

Abstract

The invention belongs to the technical field of solid waste recycling and soil improvement, and relates to a method for preparing a saline-alkali soil conditioner from sludge decomposed materials, which comprises the steps of firstly adding 0.1% -0.2% of calcium acetate into lignocellulose prehydrolysis liquid, and removing macromolecular lignin which is easy to cause surface precipitation by precipitation to obtain a modified eluent rich in micromolecular hydrophilic lignin and organic acid; then, the leaching agent and the sludge humic clinker are mixed and leached according to the liquid-solid ratio of (3-5) to 1, heavy metal and soluble salt are synchronously and efficiently removed, solid-liquid separation is carried out after leaching to obtain purified humic clinker, and finally, the purified humic clinker, the desulfurized gypsum and the humic acid are compounded according to the dry basis mass ratio of (30-50) to (20-40) to (10-30), and the saline-alkali soil conditioner is prepared through aging and granulation. The invention uses waste to treat waste, has low cost, can deeply remove heavy metals and salts, can obviously reduce the pH of soil, promote organic matters, promote plant growth, and realize the dual purposes of sludge safety utilization and saline-alkali soil improvement.

Inventors

WANG LIJIAN
LIANG YIFAN
CUI YAQIN
CUI YUEPING
LI QINGQIN
WANG GUANHUA
ZHAO YUTONG

Assignees

张家口绿垣环境工程有限公司
天津科技大学

Dates

Publication Date: 20260512
Application Date: 20251215

Claims (9)

1. The method for preparing the saline-alkali soil conditioner from the sludge decomposed material is characterized by comprising the following steps: S1, preparing a modified prehydrolysis liquid leaching agent: Taking prehydrolysis liquid, adding calcium acetate solid into the prehydrolysis liquid, continuously stirring at a constant speed to react for 30-60 min, then carrying out solid-liquid separation on the reaction liquid, and collecting supernatant to obtain a modified prehydrolysis liquid eluent, wherein the ratio of the mass of the calcium acetate solid to the volume of the prehydrolysis liquid is 0.1-0.3:100 according to g/mL; S2, leaching heavy metals in the sludge humic acid clinker: Mixing the modified prehydrolysis liquid eluent obtained in the step S1 with sludge clinker containing heavy metals according to the liquid-solid ratio (3-5) L:1 kg, and stirring at the normal temperature at the rotating speed of 50-150 rpm for 2-4 hours; S3, solid-liquid separation: carrying out solid-liquid separation on the heavy metal leacheate of the sludge clinker obtained in the step S2, collecting solids, and drying to obtain purified clinker; S4, compounding a saline-alkali soil conditioner: Uniformly mixing desulfurized gypsum, humic acid and the purified decomposed material obtained in the step S3 according to the dry basis mass ratio of (20-40): (10-30): (30-50); s5, aging and preparing a product: Aging and curing the materials mixed in the step S4 for 5-7 days at room temperature, and then drying, crushing and granulating to obtain the saline-alkali soil conditioner.
2. The method for preparing a saline-alkali soil conditioner from sludge decomposed material as claimed in claim 1, wherein the raw material of the prehydrolysis liquid in the step S1 is lignocellulose, and the lignocellulose is at least one of broadleaf wood, needle-leaved wood, bamboo wood and agricultural straw.
3. The method for preparing a saline-alkali soil conditioner from sludge decomposed materials as claimed in claim 1, wherein the pre-hydrolysate in S1 is obtained by a hydrothermal treatment process; the hydrothermal treatment process is selected from any one of hydrothermal pretreatment, dilute acid prehydrolysis and steam explosion; The prehydrolysis liquid contains hemicellulose degrading sugar, furfural, organic acid and water-soluble lignin.
4. The method for preparing the saline-alkali soil conditioner by using the sludge decomposed material as claimed in claim 1, wherein the content of CaSO 4 ·2H 2 O in the desulfurized gypsum is not less than 85%, the content of organic matters in the humic acid is not less than 40%, the content of organic matters in the purified decomposed material is not less than 35%, and the content of heavy metals is less than a risk screening value specified by soil environmental quality agricultural soil pollution risk management and control standard (GB 15618-2018) in S4.
5. The method for preparing the saline-alkali soil conditioner by using the sludge decomposed material as claimed in claim 1, wherein in the step S5, after aging and curing for 5-7 days at room temperature, the saline-alkali soil conditioner is dried at 50-60 ℃ until the water content is lower than 15%, crushed and sieved by a 100-mesh sieve, water accounting for 10-15% of the weight of the crushed material is added, and granulation is adopted, so that the granular saline-alkali soil conditioner with the particle size of 2-4 mm is prepared.
6. The method for preparing the saline-alkali soil conditioner by using the sludge decomposed material as claimed in claim 1, wherein the desulfurized gypsum, the humic acid and the purified humic acid clinker obtained in the step S4 are mixed according to the dry basis mass ratio of 30:20:50.
7. The method for preparing a saline-alkali soil conditioner from sludge decomposed material as claimed in claim 1, wherein the ratio of the mass of calcium acetate solid in S1 to the volume of the pre-hydrolyzed solution is 0.1:100 in terms of g/mL.
8. The method for preparing a saline-alkali soil conditioner from sludge decomposed materials according to claim 1, wherein the modified pre-hydrolysis liquid eluent obtained in the step S1 is mixed with sludge decomposed materials containing heavy metals in the step S2, and the liquid-solid ratio is 4L:1 kg.
9. Use of the saline-alkali soil conditioner prepared by the method of claims 1-5 in improving saline-alkali soil.

Description

Method for preparing saline-alkali soil conditioner from sludge decomposed material and application of saline-alkali soil conditioner Technical Field The invention belongs to the field of soil stabilizers, and particularly relates to a method for preparing a saline-alkali soil conditioner from a sludge decomposed material and application thereof. Background The sludge aerobic fermentation technology can effectively degrade organic matters and kill pathogenic bacteria, and convert unstable sludge into clinker with stable properties. However, heavy metals such as Cd, pb, cr, etc., present in sludge are the most major environmental risks limiting its agricultural use. If applied directly to the soil, there is a long-term potential ecological safety and agricultural product safety risk. In addition, the higher soluble salt in the humic acid clinker can aggravate the salinization of the soil, destroy the basic physicochemical property of the soil and severely limit the application of the humic acid clinker in the improvement of the saline-alkali soil. Therefore, developing a high-efficiency and low-cost technology for synchronously removing heavy metals and soluble salts is a key bottleneck for realizing the safe utilization of sludge in large-scale land. At present, the technology for removing heavy metals in sludge comprises chemical leaching, bioleaching, electric repairing and the like. The chemical leaching method has higher efficiency, but common leaches such as inorganic acid, chelating agent EDTA and the like have the defects of high cost, easiness in causing secondary pollution, damage to decomposed material nutrients and the like. Therefore, finding a green, inexpensive and efficient alternative to leaches is a research hotspot. The pre-hydrolysis of lignocellulose raw material is a key pretreatment process for selectively degrading and dissolving hemicellulose in raw material by hydrothermal treatment (such as dilute acid pre-hydrolysis and steam explosion), and the main purpose is to realize the full-component high-value utilization of biomass. The prehydrolysis liquid produced in the process is a resource liquid with complex components, and contains products such as hydrolyzed sugar, furfural, organic acid, water-soluble lignin and the like. The organic acid such as acetic acid in the prehydrolysis liquid can effectively promote the dissolution and complexation of heavy metal ions from the decomposed material, and the acidic condition can effectively leach out the easily-soluble salt ions (such as chloride salt, sulfate and the like) so as to be discharged together with the leaching liquid, thereby obviously reducing the risk of secondary salinization of soil and providing important guarantee for the subsequent preparation of safe saline-alkali soil conditioner. On the other hand, the water-soluble lignin in the prehydrolysis liquid has good heavy metal ion chelating ability due to the active functional groups such as phenolic hydroxyl groups, carboxyl groups and the like, and is a potential natural bio-based heavy metal adsorbent. However, lignin has a complex structure, and lignin with a part of high molecular weight and low hydrophilic group content in the prehydrolysis is easy to combine with heavy metal ions to form insoluble precipitate, so that the insoluble precipitate remains in the clinker, the heavy metal ions are low in removal rate, and the environment risk of secondary release exists. The current sludge heavy metal leaching technology in the market mainly depends on inorganic acid (such as hydrochloric acid and sulfuric acid) or synthetic chelating agent (such as EDTA). Although the inorganic acid leaching agent has lower cost, a large amount of soluble salt is introduced while heavy metal is removed, so that the salinization risk of soil is increased, and the synthetic chelating agent is difficult to apply on a large scale because of high price, difficult biodegradation in the environment and easy secondary pollution of underground water. In addition, although the prehydrolysis liquid is green leaching agent, partial lignin contained in the prehydrolysis liquid is easy to form insoluble precipitate with heavy metals and remain in the clinker, so that the removal rate is low, the secondary release risk exists, and the feasibility of direct application of the prehydrolysis liquid is limited. Therefore, the preparation method of the sludge rotting clinker saline-alkali soil conditioner is required to be invented, heavy metals and soluble salts can be removed synchronously with high efficiency and low cost, industrial byproducts can be fully utilized to realize 'waste treatment with waste', and meanwhile, the environmental safety and the soil improvement value of the final product can be ensured. Disclosure of Invention In order to solve the technical problems, the invention provides an integrated method which is efficient, low in cost and environment-friendly. The technical scheme of the