Iron-carbon micro-electrolysis filler and preparation method thereof

Abstract

The invention discloses an iron-carbon micro-electrolysis filler and a preparation method thereof, and belongs to the technical field of resource utilization. The iron-carbon micro-electrolysis filler comprises the following raw materials in percentage by weight: 60%-70% of laterite-nickel ore leaching residues, 20%-25% of biomass, 5%-10% of activated carbon, 1%-3% of bentonite and 1%-5% of an additive. The invention further discloses a preparation method of the iron-carbon micro-electrolysis filler. According to the iron-carbon micro-electrolysis filler and the preparation method thereof, high value of solid waste serves as a core, low-cost and high-performance preparation of the iron-carbon micro-electrolysis filler is achieved through raw material synergy, process optimization and structural design, meanwhile, the key problems that in the traditional technology, the production cost is high, and products are prone to passivation are solved, and remarkable economic and environmental benefits are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resource utilization, and particularly relates to an iron-carbon micro-electrolysis filler and a preparation method thereof. BACKGROUND

[0002] In recent years, with the rapid development of new energy automobile and other industries, the global demand for nickel has increased explosively. At present, laterite nickel ore is the main raw material for extracting nickel resources, and its hydrometallurgical process, high pressure acid leaching (HPAL), is widely used for processing low-grade ore due to its low energy consumption, low carbon emissions, and high nickel and cobalt recovery rate. However, HPAL process produces about 130 tons of leaching residue per ton of nickel produced, with global annual emissions reaching hundreds of millions of tons. Such leaching residue has characteristics such as high water content, high sulfur content, extremely fine particle size, and complex mineral structure. At present, it is mostly treated by tailings storage, resulting in a large amount of land resource occupation and environmental safety hazards. Notably, the iron content in leaching residue is as high as 40%-60%, and the existing treatment process of laterite nickel ore leaching residue can be divided into two categories: pyrometallurgical process and hydrometallurgical process. The pyrometallurgical process includes magnetization roasting and reduction smelting. Although the magnetization roasting-magnetic separation method can produce iron concentrate, the obtained iron concentrate has a low grade, and the tailings still cannot be resourcefully utilized, which fails to completely solve the problem of storage. The reduction smelting method can realize iron element recovery, but has problems such as high energy consumption and high cost, and the economic benefits are difficult to guarantee. The hydrometallurgical process treats leaching residue with organic acid or inorganic acid to prepare materials such as ferric phosphate and red iron oxide, but has problems such as large acid consumption, complex process flow, high equipment requirements, and generation of a large amount of acidic waste liquid. Therefore, it is an urgent need in the industry to develop a low-cost, simple process, low-energy-consumption, and high-economic-benefit method for resource utilization of leaching residue.

[0003] Iron-carbon micro-electrolysis filler is a functional material based on a micro-battery reaction system composed of metallic iron and carbon components, and is widely used in the field of industrial wastewater treatment. Its mechanism of action is to effectively degrade organic matter, heavy metals, and color in wastewater through the effects of redox, flocculation adsorption, electrochemical enrichment, and physical adsorption generated by micro-electrolysis reaction, and to improve the biodegradability of wastewater. However, the existing iron-carbon micro-electrolysis filler mainly relies on high-purity iron sources (such as cast iron chips and iron powder) and commercial carbon sources (such as coke and activated carbon), which has the following significant defects: (1) the source of raw materials is limited, relying on non-renewable resources and having a high cost; (2) the addition of too much binder leads to a decrease in the efficiency of micro-electrolysis filler; (3) low porosity leads to rapid activity decay; and (4) the filler is prone to hardening and passivation during use, resulting in filler failure.

[0004] At the same time, biomass resources (such as crop straw and forestry waste) are abundant in nature. Rational use of such carbon-rich resources not only alleviates environmental pollution caused by biomass waste incineration, but also provides a sustainable carbon source for material preparation.

[0005] In view of the above problems, a new method for preparing iron-carbon micro-electrolysis filler by using laterite nickel ore leaching residue and biomass is developed, which can effectively solve the environmental problems caused by the storage of leaching residue, realize the resource utilization of waste, provide cheap raw materials for iron-carbon micro-electrolysis filler to reduce production cost, and promote the efficient utilization of biomass resources. This method has significant environmental, economic and social benefits, and has great potential in application prospect and market demand. SUMMARY

[0006] The purpose of the present application is to provide an iron-carbon micro-electrolysis filler and a preparation method thereof, which can solve the technical problems of high production cost, low porosity, easy passivation and easy hardening of the iron-carbon micro-electrolysis filler in the prior art.

[0007] To achieve the above purpose, one embodiment of the present application provides an iron-carbon micro-electrolysis filler, which comprises the following raw materials in percentage by weight: 60%-70% of laterite nickel ore leaching residue, 20%-25% of biomass, 5%-10% of activated carbon, 1%-3% of bentonite, and 1%-5% of additives.

[0008] In one of the preferred embodiments of the present application, the laterite nickel ore leaching residue comprises the following chemical components in percentage by mass: Fe: 40%-60%, Co: 0.01%-0.3%, Ni: 0.01%-0.4%, Mn: 0.05%-0.5%, Cr: 1.0%-3.0%, CaO: 0.01%-0.5%, SiO2: 3%-15%, MgO: 0.3%-5%, Al2O3: 0.5%-8%, and S: 1.5%-4%.

[0009] In one of the preferred embodiments of the present application, the mass fraction of Fe in the laterite nickel ore leaching residue is greater than 50%.

[0010] In one of the preferred embodiments of the present application, the biomass is at least one of sawdust, coconut shell, walnut shell, olive pit, corn straw and sugarcane residue.

[0011] In one of the preferred embodiments of the present application, the additive is at least one of limestone and quicklime.

[0012] In one of the preferred embodiments of the present application, the particle size of the laterite nickel ore leaching residue is 200 mesh with a passing rate of >90%, the particle size of the biomass is 200-300 mesh, the particle size of the activated carbon is 200-300 mesh, and the particle size of the bentonite is 200 mesh with a passing rate of >90%.

[0013] Based on the iron-carbon micro-electrolysis filler disclosed in the present application, a preparation method of the iron-carbon micro-electrolysis filler is also disclosed, which comprises the following steps: The laterite nickel ore leaching residue, biomass, activated carbon, bentonite and additives are mixed to prepare green balls; The green balls are dried to obtain dry balls. The dry balls are fired and cooled to obtain the iron-carbon micro-electrolysis filler.

[0014] In one of the preferred schemes of the present application, the particle size of the green balls is 10-15 mm.

[0015] In one of the preferred schemes of the present application, the green balls are dried to obtain dry balls, which includes drying the green balls at a drying temperature of 110-140 DEG C for 2-4 h.

[0016] In one of the preferred schemes of the present application, the dry balls are fired and cooled to obtain the iron-carbon micro-electrolysis filler, which includes heating the dry balls to 800-900 DEG C at a heating rate of 5-10 DEG C / min for 40-60 min of reduction roasting, heating to 1100-1250 DEG C at a heating rate of 5-10 DEG C / min for 90-120 min of reduction after the roasting is completed, and cooling at a cooling rate of 30-60 DEG C / min to obtain the iron-carbon micro-electrolysis filler.

[0017] In summary, the present application has the following advantages: 1. The iron-carbon micro-electrolysis filler of the present application uses laterite nickel ore leaching residue to replace traditional high-purity iron source, and uses biomass to replace commercial carbon source, thereby realizing the collaborative high-value utilization of metallurgical solid waste and biomass waste, effectively reducing the cost of raw materials, and introducing activated carbon to strengthen the reduction reaction. The metal oxide reduction products in the leaching residue are used to construct a micro-electrolysis anode, which is combined with the cathode composed of biomass carbonization products and activated carbon to form a high-efficiency micro-battery system, thereby significantly improving the degradation efficiency of pollutants.

[0018] 2. The iron-carbon micro-electrolysis filler of the present application uses SiO2 and Al2O3 in the laterite nickel ore leaching residue to react with additives to generate a glass phase structure, thereby replacing traditional binders, enhancing the mechanical strength of the filler, and reducing production costs.

[0019] 3. In the process of dehydration and desulfurization, the laterite nickel ore leaching residue in the iron-carbon micro-electrolysis filler of the present application forms a multi-stage pore structure through the synergistic action of self-generated pores and pores generated by biomass pyrolysis, and the biomass has the functions of reducing agent and pore-forming agent, thereby realizing precise control of the pore structure, optimizing the pore structure of the filler, and delaying the activity decay.

[0020] 4. In the iron-carbon micro-electrolysis filler of the present application, the residual Ni, Co, Mn and other metal elements in the laterite nickel ore leaching residue realize in-situ catalytic reaction without the need for additional catalysts, thereby simplifying the process flow and reducing the risk of pollutant emissions.

[0021] 5、The preparation method of the iron-carbon micro-electrolysis filler in the embodiment of the application adopts a two-stage process of "pre-reduction + high-temperature deep reduction", in the pre-reduction stage, a gas-solid reaction system dominated by biomass volatiles is used to realize preliminary reduction of iron oxides and form a primary pore network skeleton; in the high-temperature deep reduction stage, the metallization rate of iron oxides is more than 93% through solid-solid diffusion reaction, and the Fe / C ratio (Fe / C = 3:1~5:1) of the final product is adjusted, and finally a micro-battery system with porous characteristics and stable structure is formed. The dry pellets after calcination are rapidly cooled in a reducing atmosphere to inhibit the coarsening of metal iron grains and avoid iron oxidation.

[0022] 6、The iron-carbon micro-electrolysis filler of the application simultaneously plays the dual role of reducing agent and pore-forming agent, effectively avoiding the increase in cost and the risk of secondary pollution caused by the addition of pore-forming agents.

[0023] 7、The application has the characteristics of low process energy consumption, controllable production cost, no secondary pollution risk, etc., and the product has high mechanical strength, excellent anti-caking performance and high added value advantage, and is easy to realize industrial production.

[0024] 8、The application takes solid waste high value as the core, realizes the low-cost and high-performance preparation of the iron-carbon micro-electrolysis filler through raw material cooperation, process optimization and structure design, and solves the key problems of high production cost and easy passivation of the product in traditional technology, which has significant economic and environmental benefits.

[0025] 9、The iron-carbon micro-electrolysis filler of the application has a metallization rate of >93%, a compressive strength of >10MPa, a specific surface area of 15-25m 2 / g, a COD (chemical oxygen demand) removal rate of >90%, and the comprehensive performance is better than that of traditional iron-carbon micro-electrolysis filler.

[0026] Other features and advantages of the application will be set forth in the specification, and in part will become apparent from the specification, or can be learned by practice of the application. The objectives and other advantages of the application can be realized and attained by the effects set forth in the specification as written and claims as written. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a flowchart of the preparation method of the iron-carbon micro-electrolysis filler in the embodiment of the application. DETAILED DESCRIPTION

[0028] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0029] The endpoints of the ranges and any values described herein are not limited to the precise values stated. The ranges and values should be construed to be approximations that allow for significant variation. Various embodiments can vary from the described embodiments, as these embodiments are presented for illustrative purposes only. Other embodiments can present differences in order to achieve the same results.

[0030] The present application provides a kind of iron-carbon micro-electrolysis filler, comprising the following raw materials by weight percentage ratio: Laterite nickel ore leaching residue 60%-70%, biomass 20%-25%, activated carbon 5%-10%, bentonite 1%-3%, additives 1%-5%.

[0031] The laterite nickel ore leaching residue is the tailings produced after extracting nickel and cobalt from limonite type laterite nickel ore using high-pressure acid leaching process, and the laterite nickel ore leaching residue comprises the following chemical components by mass percentage ratio: Fe: 40%-60%, Co: 0.01%-0.3%, Ni: 0.01%-0.4%, Mn: 0.05%-0.5%, Cr: 1.0%-3.0%, CaO: 0.01%-0.5%, SiO2: 3%-15%, MgO: 0.3%-5%, Al2O3: 0.5%-8%, and S: 1.5%-4%.

[0032] The laterite nickel ore leaching residue is in a muddy state, with a water content of 29%-32% (free water, which can be removed by drying at about 100°C). The particle size distribution is mainly in microns. The above chemical component data are the analysis results of the dried sample (dry basis). It should be particularly noted that, in addition to free water, the leaching residue also contains a large amount of structural water in the form of crystal water (included in the loss on ignition), which mainly exists in minerals such as hematite (Fe2O3·nH2O) and alunite (K(Al3(SO4)2(OH)6), and the content of crystal water accounts for 8%-15% of the mass of the dry basis.

[0033] Further, the mass fraction of Fe in the laterite nickel ore leaching residue is greater than 50%, and the leaching residue used in the present application requires that the content of Fe is greater than 50%, otherwise the content of metallic iron in the finally prepared iron-carbon micro-electrolysis filler will be insufficient, which will affect the performance of the material.

[0034] The biomass is at least one of wood chips, coconut shells, walnut shells, olive pits, corn stalks and sugar cane residues; and the additive is at least one of limestone and quicklime.

[0035] Preferably, the particle size of the laterite nickel ore leaching residue is 200 mesh passing rate > 90%, the biomass is required to be 200-300 mesh, the particle size of the activated carbon is 200-300 mesh, and the particle size of the bentonite is 200 mesh passing rate > 90%. The laterite nickel ore leaching residue has a high specific surface area due to its extremely fine particle size, which can promote the reduction reaction of iron oxides, but its particle size needs to be controlled within a reasonable range: too fine particle size is easy to cause particle agglomeration, and too coarse particle size makes the reduction reaction kinetics condition deteriorate.

[0036] The gas generated during the pyrolysis of the biomass forms a porous structure and provides a uniformly distributed carbon source at the same time, but too fine particle size of the biomass will weaken the strength of the carbon skeleton structure. The activated carbon, as an auxiliary reduction medium, can significantly enhance the reduction efficiency of iron oxides due to its high specific surface area.

[0037] The iron-carbon micro-electrolysis filler of the present application replaces the traditional high-purity iron source with the laterite nickel ore leaching residue, replaces the commercial carbon source with the biomass, and introduces the activated carbon to strengthen the reduction reaction; the micro-electrolysis anode is constructed by the reduction product of the iron oxides in the laterite nickel ore leaching residue, and is combined with the cathode composed of the carbonized product of the biomass and the activated carbon to form a high-efficiency micro-battery system, thereby significantly improving the degradation efficiency of pollutants; the biomass simultaneously plays the dual role of a reducing agent and a pore-forming agent, effectively avoiding the cost increase and secondary pollution risk caused by the addition of an external pore-forming agent.

[0038] The iron-carbon micro-electrolysis filler of the present application adjusts the material phase by adding limestone or quicklime, and cooperates with SiO2 and Al2O3 in the laterite nickel ore leaching residue to improve the mechanical strength of the filler; specifically, the glass phase structure is generated by the reaction of SiO2 and Al2O3 in the laterite nickel ore leaching residue with the limestone or quicklime, replacing the traditional binder to enhance the mechanical strength of the filler. At the same time, the self-generated pores of the laterite nickel ore leaching residue and the pores generated by the pyrolysis of the biomass cooperate to form a multi-level pore channel during the dehydration and desulfurization process of the laterite nickel ore leaching residue, and the biomass also has the dual functions of a reducing agent and a pore-forming agent, achieving precise control of the pore structure and effectively delaying the activity decay. The residual metal elements such as Ni, Co and Mn in the laterite nickel ore leaching residue can trigger in-situ catalytic reaction, without the need for additional catalysts, thereby simplifying the process flow and reducing the risk of pollutant emission.

[0039] Based on the iron-carbon micro-electrolysis filler disclosed in the present application, a preparation method of the iron-carbon micro-electrolysis filler is also disclosed, as shown in Figure 1 The method comprises the following steps: Step (1): the laterite nickel ore leaching residue, biomass, activated carbon, bentonite and additives are mixed to make green balls; specifically, the laterite nickel ore leaching residue, biomass, activated carbon, bentonite and additives are uniformly mixed, and then green balls are prepared in a disc balling machine, and the particle size of the green balls is 10mm-15mm; Step (2): the green balls are dried to obtain dry balls; specifically, the green balls prepared in step (1) are dried in a drying box, the drying temperature is 110℃-140℃, and the drying time is 2h-4h; through the drying treatment, the water in the green balls is removed, which can avoid the breakage of the balls due to the sudden temperature rise during high-temperature roasting; Step (3): the dry balls are fired and cooled to obtain iron-carbon micro-electrolysis filler; specifically, the dry balls obtained in step (2) are fired in sections, first reduced at 800℃-900℃, the heating rate is 5℃ / min-10℃ / min, and the roasting time is 40min-60min; then high-temperature reduction at 1100℃-1250℃, the heating rate is 5℃ / min-10℃ / min, and the reduction time is 90min-120min; then the fired dry balls are rapidly cooled under the protection of biomass pyrolysis autogenous reducing gas, the cooling rate is 30℃ / min-60℃ / min, and the iron-carbon micro-electrolysis filler is obtained. During the firing process, the heating rate is controlled to avoid the collapse or closure of the pores caused by the rapid release of pyrolysis gas; the rapid cooling treatment of the dry balls in the reducing atmosphere can effectively inhibit the grain coarsening of metallic iron and prevent the formation of surface oxide layer.

[0040] During the roasting process of biomass, the reduction reaction of iron oxides follows a stage reaction mechanism from "gas-solid" to "solid-solid", and the internal structure of the ball presents a shrinking core model. Specifically, the reducing volatile (CO, H2, CH4, etc.) generated by biomass pyrolysis preferentially reacts with the surface of iron oxides in a gaseous reduction reaction; after the consumption of volatile, the fixed carbon directly contacts with iron oxides to realize deep solid-phase reduction. Volatiles form a macro-pore network in the ball, and the micropores of activated carbon provide a diffusion channel for pollutants, both of which optimize the mass transfer efficiency. Volatiles and fixed carbon participate in reduction in stages, promote the generation of elemental iron at high temperature, increase the number of micro-batteries, and are beneficial to improve the pollutant degradation effect.

[0041] The preparation method of the iron-carbon micro-electrolysis filler of the present application adopts a two-stage process of "pre-reduction + high-temperature deep reduction", in the pre-reduction stage, the gas-solid reaction system dominated by biomass volatiles is used to realize the preliminary reduction of iron oxides and form the primary pore network skeleton; in the high-temperature deep reduction stage, the metalization rate of iron oxides is more than 93% through solid-solid diffusion reaction, and the Fe / C ratio (Fe / C=3:1-5:1) of the final product is adjusted, and finally a micro-battery system with porous characteristics and structural stability is formed.

[0042] Example 1 A preparation method of an iron-carbon micro-electrolysis filler, comprising the following steps: S1: the laterite nickel ore leaching residue is passed through a 200-mesh screen; the biomass is crushed and then passed through a 270-mesh screen; the activated carbon is crushed and then passed through a 270-mesh screen, and the bentonite is passed through a 200-mesh screen. The weight percentages of the raw materials are as follows: 68% of the laterite nickel ore leaching residue, 21% of the biomass, 8% of the activated carbon, 1.5% of the bentonite, and 1.5% of the additive; wherein the mass fraction of iron in the laterite nickel ore leaching residue is greater than 50%, the biomass is sawdust, and the additive is limestone; the raw materials are uniformly mixed, and then balling is performed in a disc balling machine, and the size of the green balls is 10-15 mm; S2: the green balls are dried in a drying box to obtain dry balls, the drying temperature is 120℃, and the drying time is 4h; S3: the dry balls are subjected to staged firing, first reduction roasting at 870℃ with a heating rate of 10℃ / min for 45min; high-temperature reduction at 1200℃ with a heating rate of 8℃ / min for 100min. The fired dry balls are rapidly cooled under the protection of the biomass pyrolysis autogenously reducing gas, and the cooling rate is 50℃ / min.

[0043] Example 2 A preparation method of an iron-carbon micro-electrolysis filler, comprising the following steps: S1: the laterite nickel ore leaching residue is passed through a 200-mesh screen; the biomass is crushed and then passed through a 230-mesh screen; the activated carbon is crushed and then passed through a 230-mesh screen, and the bentonite is passed through a 200-mesh screen. The weight percentages of the raw materials are as follows: 70% of the laterite nickel ore leaching residue, 23% of the biomass, 5% of the activated carbon, 1% of the bentonite, and 1% of the additive; wherein the mass fraction of iron in the laterite nickel ore leaching residue is greater than 50%, the biomass is walnut shell, and the additive is quicklime; the raw materials are uniformly mixed, and then balling is performed in a disc balling machine, and the size of the green balls is 10-15 mm.

[0044] S2: the green balls are dried in a drying box to obtain dry balls, the drying temperature is 130℃, and the drying time is 2h; S3: the dry balls are subjected to staged firing, first reduction roasting at 800℃ with a heating rate of 10℃ / min for 60min; high-temperature reduction at 1100℃ with a heating rate of 10℃ / min for 110min. The fired dry balls are rapidly cooled under the protection of the biomass pyrolysis autogenously reducing gas, and the cooling rate is 35℃ / min.

[0045] Comparative Example 1 A preparation method of an iron-carbon micro-electrolysis filler, comprising the following steps: S1: The laterite nickel ore leaching residue is sieved through a 200-mesh sieve; the biomass is crushed and sieved through a 270-mesh sieve; the activated carbon is crushed and sieved through a 270-mesh sieve, and the bentonite is sieved through a 200-mesh sieve. The weight percentages of the raw materials are as follows: 68% of the laterite nickel ore leaching residue, 21% of the biomass, 8% of the activated carbon, 1.5% of the bentonite, and 1.5% of the additive; wherein the mass fraction of iron in the laterite nickel ore leaching residue is greater than 50%, the biomass is sawdust, and the additive is limestone; the raw materials are uniformly mixed, and then balling is performed in a disc balling machine, and the size of the green balls is 10-15 mm; S2: The green balls are dried in a drying box to obtain dry balls, and the drying temperature is 120℃ and the drying time is 4h; S3: The dry balls are fired and reduced at 1200℃, and the heating rate is 8℃ / min, and the reduction time is 100min; the fired dry balls are rapidly cooled under the protection of the reducing gas generated by biomass pyrolysis, and the cooling rate is 50℃ / min.

[0046] Comparative Example 2 A method for preparing an iron-carbon micro-electrolysis filler, comprising the following steps: S1: The laterite nickel ore leaching residue is sieved through a 200-mesh sieve; the biomass is crushed and sieved through a 270-mesh sieve; the activated carbon is crushed and sieved through a 270-mesh sieve, and the bentonite is sieved through a 200-mesh sieve. The weight percentages of the raw materials are as follows: 68% of the laterite nickel ore leaching residue, 21% of the biomass, 8% of the activated carbon, 1.5% of the bentonite, and 1.5% of the additive; wherein the mass fraction of iron in the laterite nickel ore leaching residue is greater than 50%, the biomass is sawdust, and the additive is limestone; the raw materials are uniformly mixed, and then balling is performed in a disc balling machine, and the size of the green balls is 10-15 mm; S2: The green balls are dried in a drying box to obtain dry balls, and the drying temperature is 120℃ and the drying time is 4h; S3: The dry balls are fired and reduced at 870℃, and the heating rate is 10℃ / min, and the reduction time is 45min; the fired dry balls are rapidly cooled under the protection of the reducing gas generated by biomass pyrolysis, and the cooling rate is 50℃ / min.

[0047] Comparative Example 3 A method for preparing an iron-carbon micro-electrolysis filler, comprising the following steps: S1: The laterite nickel ore leaching residue is sieved through a 200-mesh sieve; the biomass is crushed and sieved through a 270-mesh sieve; the activated carbon is crushed and sieved through a 270-mesh sieve, and the bentonite is sieved through a 200-mesh sieve. The weight percentages of the raw materials are as follows: 68% of the laterite nickel ore leaching residue, 21% of the biomass, 8% of the activated carbon, 1.5% of the bentonite, and 1.5% of the additive; wherein the mass fraction of iron in the laterite nickel ore leaching residue is greater than 50%, the biomass is sawdust, and the additive is limestone; the raw materials are uniformly mixed, and then balling is performed in a disc balling machine, and the size of the green balls is 10-15 mm; S2: drying the green balls in a drying oven to obtain dry balls, the drying temperature is 120℃, and the drying time is 4h; S3: the dry balls are subjected to staged sintering, first reduction roasting at 870℃, the heating rate is 10℃ / min, and the roasting time is 45min; high-temperature reduction at 1200℃, the heating rate is 8℃ / min, and the reduction time is 100min; the sintered dry balls are rapidly cooled under the protection of the self-reducing gas generated by biomass pyrolysis, and the cooling rate is 50℃ / min.

[0048] Test Example 1: The performance of the iron-carbon micro-electrolysis fillers prepared in the above Examples 1-2 and Comparative Examples 1-3 is detected, and the detection results are shown in Table 1: Table 1: Performance detection results of iron-carbon micro-electrolysis fillers

[0049] As can be seen from Table 1, the performance of the iron-carbon micro-electrolysis filler prepared in Example 1-2 is better than that of the iron-carbon micro-electrolysis filler prepared in Comparative Example 1-3.

[0050] Specifically, the difference between Comparative Example 1 and Example 1 is only that in step S3, the dry balls are sintered only by high-temperature deep reduction process (high-temperature reduction at 1200℃, the heating rate is 8℃ / min, and the reduction time is 100min), without pre-reduction stage. Compared with Example 1, the micro-electrolysis filler prepared in Comparative Example 1 presents the following characteristic changes: the metallization rate, porosity and specific surface area are all reduced, but the compressive strength is slightly improved. Due to the lack of gas-solid reaction in the pre-reduction stage, the iron oxides cannot be fully pre-reduced, and directly enter the solid-solid reaction with low efficiency, so the metallization rate of the micro-electrolysis filler prepared in Comparative Example 1 is low. Volatile matter is released concentratedly at high temperature, resulting in depletion of carbon source in local area, and part of the iron oxides cannot be completely reduced to elemental iron. The absence of the pre-reduction stage leads to the failure to form the primary pore skeleton, and the biomass pyrolysis gas rapidly escapes at high temperature, causing the collapse or closure of the pores; at the same time, the iron particles rapidly agglomerate at 1200℃, further blocking the pore structure, resulting in the reduction of the porosity and specific surface area of the micro-electrolysis filler prepared in Comparative Example 1. High-temperature direct sintering makes the particles more closely combined, and the filler structure is densified, thereby improving the compressive strength, which is manifested as the increase of the compressive strength of the micro-electrolysis filler.

[0051] Comparative Example 2 differs from Example 1 only in that in Step S3, the dry pellets are fired only by a pre-reduction process (reduction roasting at 870°C, heating rate 10°C / min, roasting time 45 min), without a high-temperature deep reduction stage. Compared with Example 1, the micro-electrolysis filler prepared in Comparative Example 2 presents the following changes in properties: the metallization rate and the compressive strength decrease significantly, and the porosity and the specific surface area increase slightly. Due to the lack of a high-temperature stage, the solid-solid reaction is insufficient, and the iron oxides fail to be completely reduced to elemental iron, resulting in a decrease in the metallization rate. The slow release of volatile matter from the biomass in the pre-reduction stage forms uniform macro-pores, and the material is not subjected to high-temperature sintering, so that the pore structure is well preserved. In Example 1, the high-temperature stage at 1200°C promotes the reaction of SiO2, Al2O3 and limestone to form a glass phase, significantly enhancing the mechanical strength of the filler. In Comparative Example 2, only reduction roasting at 870°C is performed, and the glass phase is not sufficiently formed, so the pellets mainly rely on the binding action of the bentonite, resulting in low strength. In addition, the iron oxides in Comparative Example 2 are not fully reduced, making it difficult to form a stable iron-carbon skeleton, further reducing the material strength.

[0052] Comparative Example 3 differs from Example 1 only in that in Step S1, the weight percentages of the raw materials are adjusted: from “laterite nickel ore leaching residue 68%, biomass 24%, bentonite 2%, additives 1.2%” to “laterite nickel ore leaching residue 68%, biomass 25%, activated carbon 3%, bentonite 2%, additives 2%”, i.e., the proportion of activated carbon is reduced. Compared with Example 1, the micro-electrolysis filler prepared in Comparative Example 3 presents the following changes in properties: the metallization rate, the porosity and the specific surface area all decrease, and the compressive strength increases slightly. In Comparative Example 3, the proportion of biomass is increased, but its fixed carbon content is lower than that of activated carbon, and the volatile matter is mainly consumed in the pre-reduction stage, having limited contribution to deep reduction. Although the proportion of the total carbon source (biomass + activated carbon) changes little, the reduction efficiency of activated carbon is higher, and its reduction leads to a decrease in solid-solid reduction capacity, so the metallization rate decreases slightly. The activated carbon has a rich microporous structure, and its reduced amount directly leads to a decrease in micro-pores, which in turn affects the diffusion channels of pollutants. Although the proportion of biomass is increased, the pores generated by the pyrolysis of biomass cannot completely make up for the loss of micropores of activated carbon. The increase in the amount of bentonite enhances the cold strength of the pellets, and the increase in limestone makes more glass phase generated at high temperature, thereby improving the mechanical strength of the material.

[0053] Other comparisons Example 2 vs. Example 1: 1) The metallization rate of Example 2 is slightly lower than that of Example 1. Due to the reduction of the proportion of activated carbon, the carbon source is insufficient, affecting the solid-solid reduction reaction. At the same time, the high-temperature reduction temperature is reduced from 1200°C to 1100°C, reducing the solid-phase diffusion rate, and making the kinetic conditions for the reduction of iron oxides to elemental iron worse.

[0054] 2) The specific surface area and porosity of Example 2 are slightly lower than those of Example 1. Due to the increase in the particle size of the biomass, the size of the pores formed after pyrolysis is relatively large, reducing the specific surface area. At the same time, the reduction in the amount of activated carbon causes the number of micropores to decrease, thereby affecting the construction of the mass transfer channel.

[0055] 3) The compressive strength of Example 2 is higher than that of Example 1. Although the proportion of bentonite is reduced, the additive is changed to lime (CaO), which is more likely to react with SiO2 and Al2O3 to form a glass phase at high temperatures, thereby enhancing the mechanical strength of the filler.

[0056] Test Example 2: The iron-carbon micro-electrolysis fillers prepared in Examples 1-2 and Comparative Examples 1-3 above were used in the treatment of high-concentration organic wastewater. Specifically, a solution with a COD concentration of 3000 mg / L was selected, the pH was adjusted to 3, and the iron-carbon micro-electrolysis filler was added thereto. After aeration for 120 min, the pH was adjusted to 8, the supernatant was removed after static settling, and the COD concentration was measured. The treatment results are shown in Table 2. The iron-carbon micro-electrolysis filler of the present application was continuously operated for 1 month, and the treatment effect was stable without the occurrence of hardening and passivation.

[0057] Table 2: COD effect of iron-carbon micro-electrolysis filler in wastewater treatment

[0058] As can be seen from Table 2, the COD removal efficiency is ranked as follows: Example 1 > Example 2 > Comparative Example 3 > Comparative Example 1 > Comparative Example 2.

[0059] Examples 1 and 2 use a two-stage calcination combined with an optimized ratio process, and the prepared materials have high metallization rate, large specific surface area, and multi-level pore structure, while also having excellent mechanical strength. This structure can promote the efficient reaction of the micro-battery and exhibit good running stability and anti-hardening performance. The metallization rate of Comparative Example 1 is relatively low, which leads to a decrease in the reaction activity of the micro-battery; at the same time, its small specific surface area and low porosity accelerate the decay of the active components. The metallization rate of Comparative Example 2 is the lowest, and the number of iron-carbon micro-batteries is significantly reduced; although the porosity is relatively high, the compressive strength is insufficient, leading to the breakage of part of the filler and affecting the treatment efficiency. In Comparative Example 3, the amount of activated carbon is reduced, and the iron-carbon ratio exceeds 5:1, which leads to a decrease in the reaction activity of the micro-battery; at the same time, the small specific surface area and low porosity cause the active components to decay quickly, but the high mechanical strength reduces the risk of passivation of the material to some extent.

[0060] In summary, the preparation method of the iron-carbon micro-electrolysis filler of the present application has low process energy consumption, controllable cost, no secondary pollution risk, and is easy to industrialize. The prepared iron-carbon micro-electrolysis filler has high product added value, high mechanical strength, and excellent anti-hardening performance.

[0061] The above-described embodiments are merely intended to describe the preferred embodiments of the present application, and are not intended to limit the scope of the present application. Various changes and modifications of the present application, which are apparent to those skilled in the art, can be made to the present application without departing from the design spirit of the present application, and such changes and modifications should fall within the scope of the appended claims.

Claims

1. An iron-carbon micro-electrolysis packing, characterized in that, The raw materials include the following ingredients in percentage by weight: 60%-70% of laterite nickel ore leaching residue, 20%-25% of biomass, 5%-10% of activated carbon, 1%-3% of bentonite, and 1%-5% of additives.

2. The iron-carbon micro-electrolysis packing according to claim 1, characterized in that: The laterite nickel ore leaching residue includes the following chemical components in percentage by mass: Fe: 40%-60%, Co: 0.01%-0.3%, Ni: 0.01%-0.4%, Mn: 0.05%-0.5%, Cr: 1.0%-3.0%, CaO: 0.01%-0.5%, SiO2: 3%-15%, MgO: 0.3%-5%, Al2O3: 0.5%-8%, and S: 1.5%-4%.

3. The iron-carbon micro-electrolysis packing material according to claim 1, characterized in that: The mass fraction of Fe in the laterite nickel ore leaching residue is greater than 50%.

4. The iron-carbon micro-electrolysis packing material according to claim 1, characterized in that: The biomass is at least one of sawdust, coconut shell, walnut shell, olive pit, corn straw, and sugarcane residue.

5. The iron-carbon micro-electrolysis packing material according to claim 1, characterized in that: The additives are at least one of limestone and quicklime.

6. The iron-carbon micro-electrolysis packing material according to claim 1, characterized in that: The particle size of the laterite nickel ore leaching residue is 90% passing 200 mesh, the particle size of the biomass is 200 mesh-300 mesh, the particle size of the activated carbon is 200 mesh-300 mesh, and the particle size of the bentonite is 90% passing 200 mesh.

7. A method for preparing the iron-carbon micro-electrolysis filler according to any one of claims 1-6, characterized in that, The method includes the following steps: Mixing the laterite nickel ore leaching residue, biomass, activated carbon, bentonite, and additives to make green balls; Drying the green balls to obtain dry balls; Firing the dry balls and cooling to obtain iron-carbon micro-electrolysis filler.

8. The method for preparing the iron-carbon micro-electrolysis filler according to claim 7, characterized in that: The particle size of the green balls is 10 mm-15 mm.

9. The preparation method of the iron-carbon micro-electrolysis filler according to claim 1, characterized in that: The drying of the green balls to obtain dry balls includes drying the green balls at a drying temperature of 110°C-140°C for 2h-4h.

10. The method for preparing the iron-carbon micro-electrolysis filler according to claim 1, characterized in that: The firing of the dry balls and cooling to obtain iron-carbon micro-electrolysis filler includes heating the dry balls to 800°C-900°C at a heating rate of 5°C / min-10°C / min for reduction for 40 min-60 min, heating to 1100°C-1250°C at a heating rate of 5°C / min-10°C / min for reduction for 90 min-120 min after the reduction is completed, and cooling at a cooling rate of 30°C / min-60°C / min to obtain the iron-carbon micro-electrolysis filler.

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