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CN-122010619-A - Fe for synergistic catalysis and nutrient recovery3O4Multifunctional N-P-HC compound and preparation and application thereof

CN122010619ACN 122010619 ACN122010619 ACN 122010619ACN-122010619-A

Abstract

The invention relates to a Fe 3 O 4 @N-P-HC multifunctional compound for synergistic catalysis and nutrient recovery, and preparation and application thereof, comprising the steps of preparing Fe 3 O 4 @N-P-HC compound, carrying out hydrothermal carbonization reaction on agricultural and forestry wastes, preparing struvite crystals and preparing compound fertilizer. The composite prepared by the invention takes magnetic Fe3O4 as a core and nitrogen-phosphorus doped hydrothermal carbon as a carrier, and realizes closed loop circulation of catalysis, fertilizer supply and recovery. The compound fertilizer is a brand new two-in-one functional product of slow release fertilizer and soil conditioner, realizes a synergistic effect, greatly improves the added value of the product, and realizes the maximum utilization of resources by adopting the integrated treatment of waste treatment, resource recovery and high-valued product.

Inventors

  • YAO ZONGLU
  • WANG DAN
  • LIU ZIYUN
  • ZHAO LIXIN
  • HUO LILI
  • SU JINTING
  • LEI QIQI
  • ZHAO YANAN
  • JIA JIXIU

Assignees

  • 中国农业科学院农业环境与可持续发展研究所

Dates

Publication Date
20260512
Application Date
20260205

Claims (10)

  1. 1. A method for preparing a Fe 3 O 4 @ N-P-HC multifunctional complex, characterized in that the method comprises the steps of: (1) Raw material pretreatment, namely crushing lignocellulose agricultural and forestry waste, immersing the crushed lignocellulose agricultural and forestry waste in hydrochloric acid solution for heating reaction, and drying after solid-liquid separation to obtain pretreated solids; (2) Hydrothermal loading, namely placing the pretreated solid and the mixed aqueous solution of Fe 2+ and Fe 3+ into a hydrothermal reaction kettle, reacting for 2-6 hours at 180-240 ℃ in an inert atmosphere, and carrying out solid-liquid separation and drying after the reaction to obtain porous hydrothermal carbon; (3) Adding ammonia water into the porous hydrothermal carbon until the system is alkaline, and magnetically separating and drying after the reaction to obtain a Fe 3 O 4 @HC intermediate; (4) Nitrogen-phosphorus co-doping modification, namely dissolving monoammonium phosphate and urea into a solvent according to the mass ratio of 1.5-2.5:1 to prepare a modified liquid, immersing the Fe 3 O 4 @HC intermediate into the modified liquid, and carrying out solid-liquid separation after dispersion treatment; (5) Step-by-step pyrolysis activation, namely heating the solid obtained in the step (4) to 500-600 ℃ at a temperature rising rate of 3-8 ℃ per minute under inert atmosphere, calcining for 2.5-3.5 hours, soaking the obtained solid in dilute sulfuric acid solution after calcining, stirring, washing and drying, and finally, treating for 0.8-1.2 hours at a temperature of 350-450 ℃ in mixed atmosphere of H 2 and Ar to obtain the Fe 3 O 4 @N-P-HC multifunctional compound.
  2. 2. A Fe 3 O 4 @N-P-HC multifunctional compound is characterized in that the compound takes porous hydrothermal carbon as a carrier, fe 3 O 4 nano particles are loaded on the porous hydrothermal carbon, nitrogen atoms and phosphorus atoms are doped in a framework of the hydrothermal carbon at the same time, and the compound comprises the following characteristics (a) and (b): (a) The alloy comprises, by weight, 56.8-68.5% of C, 3.6-4.9% of N, 2.2-3.1% of P, 13.8-19.5% of Fe, 21.7-28.5% of O and 1.9-2.8% of H; (b) In the Raman spectrum, the intensity ratio (I_D/I_G) of the D peak at about 1355 cm -1 to the G peak at about 1590: 1590 cm -1 is 1.10-1.15.
  3. 3. The Fe 3 O 4 @ N-P-HC multifunctional composite according to claim 2, characterized in that in the X-ray photoelectron spectroscopy (XPS) of the composite, the N1 s spectrum shows the presence of three forms of pyridine nitrogen, pyrrole nitrogen and graphite nitrogen, and the relative content ratio of the three is (35-40)%: (40-45)%: (20-25)%.
  4. 4. The Fe 3 O 4 @N-P-HC multifunctional composite according to claim 2, wherein the specific surface area of the composite is 200-350 m2/g and the pore volume is 0.15-0.30 cm3/g.
  5. 5. The Fe 3 O 4 @ N-P-HC multifunctional complex according to any one of claims 2 to 4, characterized in that the complex has a saturation magnetization of 25 to 50 emu/g.
  6. 6. Use of the Fe 3 O 4 @ N-P-HC multifunctional complex as defined in any one of claims 2 to 5 in biomass recycling treatment.
  7. 7. The method for producing the hydrothermal carbon-struvite compound fertilizer by utilizing lignocellulose agricultural and forestry waste is characterized by comprising the following steps of: A. Catalytic hydrothermal carbonization, namely mixing agriculture and forestry waste, water and the Fe 3 O 4 @N-P-HC multifunctional compound for hydrothermal reaction, and carrying out solid-liquid separation after the reaction is finished to obtain a solid product and a liquid product; B. b, intelligent crystallization recovery, namely adding alkali liquor, a magnesium source and seed crystals into a reaction system under the condition of monitoring the pH value and the conductivity of the liquid product obtained in the step A in real time, performing struvite crystallization reaction, and performing solid-liquid separation after the reaction to obtain struvite crystals; C. And B, compounding the product, namely, magnetically separating the solid product obtained in the step A to recover the Fe 3 O 4 @N-P-HC multifunctional compound to obtain nitrogen-rich hydrothermal carbon, and mixing the nitrogen-rich hydrothermal carbon with the struvite crystal obtained in the step B, and granulating to obtain the hydrothermal carbon-struvite compound fertilizer.
  8. 8. The method according to claim 7, wherein in the step A, the mass ratio of the agricultural and forestry waste to the water to the Fe 3 O 4 @N-P-HC multifunctional composite is 1 (8-12): 0.08-0.15.
  9. 9. The method of claim 7, wherein step B is performed in a feedback pH controlled crystallization system, and the control command is triggered to add struvite seed crystals when the rate of decrease in the conductivity of the reaction system is monitored in real time to exceed 100 μs cm -1 ·min -1 .
  10. 10. The method according to claim 7, wherein the step C comprises the steps of respectively crushing and mixing the nitrogen-rich hydrothermal charcoal and struvite crystals, spraying a binder solution for granulation, and drying the obtained granules to obtain the hydrothermal charcoal-struvite compound fertilizer.

Description

Fe 3O4 @N-P-HC multifunctional compound for synergistic catalysis and nutrient recovery, preparation and application thereof Technical Field The invention belongs to the technical field of agricultural waste recycling and fertilizer. More particularly, the invention relates to a Fe 3O4 @N-P-HC multifunctional compound for synergistic catalysis and nutrient recovery, a preparation method of the compound, and a system method for converting lignocellulose agricultural and forestry waste into a hydrothermal carbon-struvite compound fertilizer by using the compound. Background The amount of agricultural biomass resources in China is huge, and the existing related data show that about 8.65 hundred million tons of crop straws are produced each year. The efficient utilization of these wastes is of great importance for achieving agricultural sustainable development and environmental protection. The hydrothermal technology is used as an effective thermochemical conversion method, can convert agricultural biomass into hydrothermal carbon and high-added-value chemicals, and is a new way for recycling agricultural wastes. Existing studies have shown that the addition of a catalyst can significantly improve the efficiency and product quality of the hydrothermal reaction. CN202310556443.8 discloses a method for promoting biomass humic to synthesize artificial humic acid by iron ion catalysis and application thereof, the iron ion catalysis improves the yield of humic acid in hydrothermal carbon, but the catalysis effect is limited, and the reactivity of the raw materials and the compound can be further enhanced. CN119219448a discloses a method for coupling an external nitrogen source (ammonium sulfate, urea, etc.) by using nanobubble technology, wherein the nitrogen source is used as both a compound and a nitrogen source supplement for producing nitrogen-rich liquid fertilizer. The method has innovation in the aspects of strengthening nitrogen transfer and improving nitrogen content of solid products, but has obvious limitation that nitrogen in liquid phase mainly exists in a form of NH 4 +, so that the utilization rate is low and the volatile loss is easy. In the aspect of nitrogen and phosphorus recovery, a struvite (magnesium ammonium phosphate, MAP) crystallization method has become a research hot spot because the struvite can simultaneously recover nitrogen and phosphorus elements and the product has slow-release fertilizer efficiency. CN110078040a discloses a method and a system for recovering struvite by using waste water from wood activated carbon production, adding nitrogen source and magnesium source into waste water from wood activated carbon production, and producing struvite by struvite crystallization process, but there is a problem that one-time addition of sodium hydroxide solution causes excessive saturation fluctuation of system, and long discharge period causes non-uniform crystal morphology, affecting precipitation separation efficiency. CN118289990a discloses a device and a method for recovering high-purity granular struvite from corn starch wastewater, wherein the magnesium-phosphorus addition ratio is controlled by a metering pump, and the pH is adjusted by an electromagnetic air pump and an alkaline liquid pump. However, the method has single detection index, low pH detection frequency (once every 1-2 hours), needs to regulate and control alkali liquor addition at fixed time, has fixed discharging time (once every 24 hours of discharging), and can cause low mud discharging efficiency, unstable crystallization process and poor product quality controllability. Although each of the above techniques has a focus, there are limitations. For example, CN202310556443.8 mainly focuses on humic acid yield, an iron salt catalyst has single function, and the problems of enrichment and recovery of nitrogen and phosphorus nutrients in products cannot be solved, and the guanite recovery technology such as CN110078040A is characterized in that raw materials depend on wastewater with fixed components, the crystallization process is controlled widely, and the technology is difficult to adapt to agricultural and forestry waste hydrothermal liquefaction liquid with complex and changeable components. More critical, the catalytic conversion, nutrient release and crystallization recovery are generally regarded as separate unit operations in the prior art, and an integrated solution which can penetrate through the whole process, can efficiently catalyze biomass depolymerization, can serve as an internal nutrient reservoir and finally realize full-flow intelligent control is lacking. Therefore, the development of a multifunctional catalyst and a synergistic process matched with the multifunctional catalyst are urgent demands for realizing high-valued and full-scale utilization of agricultural and forestry wastes. Disclosure of Invention The invention aims to improve the yield of a hydrothermal carbon production method, provi