镁渣基缓释性硅钾肥的制备及性能研究

发布时间：2018-01-01 04:26

本文关键词：镁渣基缓释性硅钾肥的制备及性能研究　出处：《山西大学》2016年博士论文　论文类型：学位论文

【摘要】：镁及镁合金是重要的战略储备物质,我国是最大的镁生产国和出口国。镁冶炼主要采用皮江法炼镁,每生产1吨金属镁,产生6～8吨的镁渣,镁渣的大量排放堆积,不仅占用土地,也对周围环境造成极大影响,制约了镁产业的健康持续发展。此外,我国钾肥资源严重不足,钾肥流失严重,造成钾资源的浪费和环境污染。本研究基于镁渣的理化特性和环境安全性,利用碳酸钾改性镁渣,制备了一种新型缓释性硅钾肥,并对硅钾肥的制备工艺、结晶性能、养分释放特性、肥效和农业安全性进行了系统的理论分析和实验研究。1、以皮江法还原镁渣(MS)为研究对象,通过XRD、FTIR、TG-DT、SEM-EDS等对其进行表征分析,分析了镁渣的理化特性和环境风险,结果表明,镁渣是一种细颗粒粉末状的碱性废渣,颗粒粒径以147μm为主,各粒径镁渣的化学组成存在差异,镁渣的比表面积、表观密度、孔径与硅酸盐水泥特性相近,不适合用于孔吸附材料,较适合用于建材开发；镁渣的主要化学组成为CaO、SiO2、MgO、Fe2O3、 Al2O3,主要物相为β-Ca_2SiO_4、γ-Ca_2SiO_4、MgO和CaO,次要组分相为Ca(OH)2、 Mg(OH)2、CaCO3、MgCO3,主要以稳定的矿物形态存在,可溶性组分很少；镁渣中重金属含量符合有机-无机复混肥国家标准,放射性核素比活度、内照射指数与外照射指数达到A类装饰装修材料国家标准的放射性要求(IRa≤1.0,Iγ≤1.3)。镁渣中重金属主要以稳定的有机态和残渣态存在,镁渣中重金属与氟的浸出浓度均远低于国内外危险废物标准限值,即使在最不利条件下,镁渣中重金属的有效浸出量仍远低于毒性鉴别的最低限值,且镁渣中含量最高的Cr主要以毒性较小的Cr3+存在；Cr、Cu和Ni的浸出量与浸出剂的pH值表现出强的相关性,浸出质量浓度均低于危险废物标准限值。因此,镁渣中含有土壤和作物所需有益元素,环境安全性高,污染风险低,可以进行农业资源化利用。2、通过单因素实验与正交试验相结合考察了碳酸钾改性镁渣制备硅钾肥的工艺。首先以单因素实验确定了正交试验的考察因子及水平；然后以总硅中活性硅含量(AST)和硅钾肥的初期溶出率(Kin)为考察指标,采用正交试验对硅钾肥制备工艺进行了优化。结果表明,各因子对AST和Kin影响的大小次序分别为加热温度镁渣粒径保温时间K_2O含量和镁渣粒径加热温度保温时间K_20含量,其中镁渣粒径与加热温度对AST和Kin影响最为显著(α=0.05),确定硅钾肥制备的最优实验方案为：选用风冷镁渣,K_2O添加量为15～25%,加热温度1300℃,保温时间60min,镁渣粒径≤80μm,冷却方式为风冷；所制硅钾肥的K释放率符合国标《缓释肥料》中“部分缓释肥料”要求,总硅中有效硅含量约为镁渣的2.5倍,钾收率为90%左右；镁渣中Fe2O3、Al2O3的组成变动对硅钾肥性能无明显影响,MgO含量的增加可改善硅钾肥的性能。3、通过XRD、SEM以及SEM-EDS测试了不同条件所制硅钾肥的结晶性能,结果表明,硅钾肥中主要含钾结晶相为Ca1.917K0.166SiO_4、K_2MgSiO_4、K_4CaSi_3O_9,非含钾结晶相为Ca_2SiO_4、方镁石(MgO)与新出现的硅酸钙矿物Ca3Si05,硅钾肥中钾主要以结晶相和非结晶相两种形式存在,由此推知,镁渣与碳酸钾高温反应的主要机制是生成了三元体系K_2O-CaO-SiO2与K_2O-MgO-SiO2的混合物。镁渣类型对硅钾肥的结晶及缓释性能均无明显影响,冷却方式、加热温度、镁渣粒径、保温时间、K_20添加量等对硅钾肥的结晶性能存在一定影响,进而影响了硅钾肥中硅、钾的溶出活性；镁渣中添加2% Fe2O3、1% Al2O3对硅钾肥的结晶及缓释性均无明显影响,添加3%MgO有利于结晶相K_2MgSiO_4的生成,可以改善硅钾肥的硅溶出性与钾缓释性。4、通过水中溶出率法和土柱淋溶法,具体考察了硅钾肥的养分释放特性,并进行了养分释放动力学拟合,结果表明：硅钾肥破碎的最佳粒度为20～40目,微分溶出率为3.79～3.95%,初期溶出率为23.93～24.62%,与硫酸钾肥相比具有明显的缓释性；硅钾肥钾素在柠檬酸中释放速率明显高于其在水中的释放速率,在土壤中的释放速率明显低于其在溶液的释放速率。硅钾肥在水和2%柠檬酸溶液中的钾释放动力学最优模型分别是Elovich模型和一级动力学模型；水和柠檬酸淋溶,硅钾肥在土壤中钾释放动力学的最优模型分别为双常数模型和Elovich模型。硅钾肥经柠檬酸溶出后,晶体结构完全破坏,转变为非晶态结构；经水溶出后,结晶种类无变化,非晶相明显增多。硅钾肥钾素可根据作物和土壤需求有效释放,避免了肥料养分的流失,其养分释放的本质过程是含钾矿物受溶液作用,结晶结构破坏,钾素在溶液中的溶解过程。5、通过硅钾肥在玉米盆栽试验中的应用,考察了硅钾肥的肥效和农业安全性。结果表明,施加硅钾肥可以改善玉米的农艺性状,增加玉米的干物质和籽粒产量,显著提高玉米的吸钾量、吸硅量,提高玉米的钾素、硅素利用率；硅钾肥可不断弥补土壤因作物吸收而减少的速效钾,促进土壤钾素的有效化,改善土壤的供硅能力,可满足玉米整个生长发育期的养分需要,且酸性土壤较碱性土壤更有利于硅钾肥中硅、钾的有效释放；硅钾肥为碱性肥料,施加硅钾肥使土壤pH值升高,且酸性土壤较碱性土壤更为明显。硅钾肥的重金属含量符合《有机-无机复混肥》国家标准,重金属与氟的浸出浓度远低于《危险废物鉴别标准-浸出毒性鉴别》标准限值,且达到地下水Ⅱ类水质量标准,施加硅钾肥后,玉米和土壤重金属含量均在安全范围,环境质量评价结果表明,除水稻土上硅钾肥处理与硫酸钾肥处理的内梅罗综合污染指数(P综)略大于0.7,属于警戒外,其余指数均在安全范围以内,施加硅钾肥不会对作物和土壤环境安全造成影响。综上,利用碳酸钾改性镁渣制备缓释性硅钾肥是可行的,该研究为镁渣的资源化利用和缓释肥料制备提供了新思路,对解决镁渣堆存和肥料流失引发的环境问题具有重要意义。
[Abstract]:Magnesium and magnesium alloy is an important strategic material reserves, China is the largest producer and exporter of magnesium. Magnesium smelting mainly adopts pidgeonmagnesiumprocess, each producing 1 tons of metal magnesium, produce 6 to 8 tons of magnesium slag, a large number of magnesium slag discharge accumulation not only occupy the land, but also on the surrounding environment a great impact, magnesium restricts the healthy and sustainable development of the industry. In addition, a serious shortage of potash resources in China, caused serious loss of potassium fertilizer, potassium resource waste and environmental pollution. This research is based on the physicochemical properties and environmental safety of magnesium slag, magnesium slag modified by potassium carbonate, a new type of slow release silicon potash fertilizer the preparation and preparation process of silicon potash crystallization performance, nutrient release characteristics, fertilizer and agricultural safety through theoretical analysis and experimental research of the.1 system, with Pidgeon magnesium slag (MS) as the research object, through XRD, FTIR, TG-DT, SEM-EDS and other characterized points An analysis of the physicochemical characteristics and environmental risk, the results show that the magnesium slag, magnesium slag is alkaline residue a fine powder particles, the particle size to 147 m, the particle size of magnesium slag chemical composition between magnesium slag surface area, apparent density, pore size and similar Portland cement properties, not suitable for adsorption materials, and is suitable for the development of major chemical building materials; magnesium slag is composed of CaO, SiO2, MgO, Fe2O3, Al2O3, the main phase is -Ca_2SiO_4 -Ca_2SiO_4 beta, gamma, MgO and CaO, the secondary component phase is Ca (OH) 2, Mg (OH) 2, CaCO3, MgCO3, mainly in the stable mineral forms, soluble components less; heavy metal content of magnesium slag with organic inorganic compound fertilizer national standards, radionuclides, radiation of internal exposure index and irradiation index reached a national standard of decoration materials (IRa = 1, I = 1.3 y). Heavy magnesium residue Is mainly organic state and residual state stability, leaching concentration of heavy metals and fluorine magnesium residue are far below the limit of hazardous waste standards at home and abroad, even in the most adverse conditions, the effective leaching amount of heavy metals in magnesium slag is still far lower than the minimum toxicity identification value, and the highest content of magnesium slag Cr is mainly in the less toxic Cr3+; Cr, Cu and Ni leaching and leaching agent pH showed a strong correlation, the leaching concentrations were lower than the standard limit of hazardous waste. Therefore, magnesium slag containing soil and crop of beneficial elements, environmental pollution and high safety, low risk, can.2 utilization of agricultural resources, through the single factor experiment and orthogonal experiment, the process of combining the effects of potassium carbonate by modified silicon and potassium magnesium slag system. Firstly, by single factor experiment to determine the effects of factors and levels of orthogonal test; and then to the total activity of silicon in silicon The content of (AST) and the initial dissolution rate of silicon potash fertilizer (Kin) as index, orthogonal test of silicon potassium fertilizer preparation process was optimized. The results show that the influence of each factor on AST and Kin respectively in order of the size of the heating temperature of magnesium slag particle size holding time K_2O content and particle size of magnesium slag heating temperature the holding time of K_20 content, the particle size of magnesium slag and the heating temperature of AST and Kin has the most significant impact (alpha =0.05), to determine the optimal preparation of silicon potassium fertilizer experiment scheme that use air-cooled magnesium slag, K_2O content is 15 ~ 25%, the heating temperature is 1300 degrees centigrade, the holding time of 60min, magnesium slag particle size less than or equal to 80 m, wind cooling system; the silicon potash fertilizer K release rate in line with the national standard < > "part of the slow-release fertilizer slow-release fertilizers, total effective silicon content in silicon magnesium slag is about 2.5 times the yield of potassium was about 90%; Fe2O3 magnesium slag, changing the composition of Al2O3 on properties of silicon potassium fertilizer no obvious Effect of the increase of the content of MgO can improve the performance of.3, silicon and potassium by XRD, the results showed that the crystallization properties of SEM and SEM-EDS, were tested in different conditions for silicon and potassium, silicon and potassium in potassium containing mainly crystalline Ca1.917K0.166SiO_4, K_2MgSiO_4, K_4CaSi_3O_9, non crystalline potassium periclase phase is Ca_2SiO_4 (MgO) with the emergence of new calcium silicate mineral Ca3Si05, potassium silicon potash fertilizer mainly in the crystalline and non crystalline phase two forms exist, accordingly, the main mechanism of magnesium slag and potassium carbonate at high temperature is generated three yuan mixture system of K_2O-CaO-SiO2 and K_2O-MgO-SiO2. There were no obvious effects on the crystallization of magnesium slag type silicon potassium fertilizer and sustained release performance of cooling, heating temperature, magnesium slag particle size, soaking time, crystallization properties of K_20 adding amount of silicon potassium fertilizer has certain effect, thereby affecting the silicon potassium fertilizer of silicon, dissolving active potassium; adding 2% magnesium slag There were no significant effects of Fe2O3,1% Al2O3 on the crystallization of silicon potassium fertilizer and slow-release, adding 3%MgO to produce crystalline K_2MgSiO_4, and potassium release of dissolution of.4 can improve the silicon silicon potash fertilizer, the water dissolution rate method and soil column leaching method, and analyzes the silicon potash fertilizer nutrient release characteristics, and the nutrient release kinetics, the results show that the optimum size of silicon potassium fertilizer is 20 ~ 40 mesh broken, differential dissolution rate is 3.79 ~ 3.95%, the initial dissolution rate ranged from 23.93 to 24.62%, compared with the sulfuric acid potassium fertilizer has obvious controlled release; silicon potassium potassium in the citric acid release rate was significantly higher than that in the the release rate of water, the release rate in soil was significantly lower than that in solution. The release rate of silicon and potassium in water and 2% citric acid solution of potassium release kinetics of optimal models are the Elovich model and the first-order kinetic model; water and lime Citric acid leaching, the optimal model of release kinetics of silicon and potassium in soil potassium were double constant model and Elovich model. The silicon potassium fertilizer by citric acid dissolution, crystal structure completely destroyed, transformed into amorphous structure; by water dissolution, crystallization type change, amorphous silicon and potassium potassium are increased obviously. According to the demand of crop and soil elements can effectively release, to avoid the loss of nutrients, the nature of the nutrient release is affected by potassium mineral solution, crystal structure damage, the dissolution process of potassium.5 in solution, the application experience in maize pot through silicon potash fertilizer, K fertilizer and silicon were investigated agricultural safety. The results showed that the agronomic traits of maize applied silicon potash fertilizer can improve and increase maize dry matter and grain yield, K significantly increased the amount of corn, Si uptake by maize, improve the utilization rate of potassium, silicon; silicon potassium fertilizer can not Break up the potassium for crop absorption decreased, promote soil effective potassium, improve the silicon supplying capacity of the soil, the whole growth period of corn can meet the nutrient requirements, and more acidic soil alkaline soil is more conducive to the effective release of silicon and potassium silicon, potassium; silicon potassium alkaline fertilizer, applying silicon fertilizer the soil pH value increased, and the soil is acidic alkaline soil is more obvious. The heavy metal content of silicon potassium fertilizer with < semiorganic fertilizer > national standard, the leaching concentration of heavy metals and fluorine is far lower than the identification standard for hazardous wastes - > > standard leaching toxicity identification limits, and reached the groundwater class II water quality standards. Application of silicon potassium fertilizer, heavy metal content in corn and soil in the safe range, environmental quality evaluation results show that in addition to paddy soil silicon potash fertilizer treatment and potassium sulfate fertilizer treatment Nemero comprehensive pollution index (P ensemble) is slightly greater than 0 .7, which belongs to the warning, the rest of the index in the safe range, application of silicon potassium fertilizer will not affect crop and soil environmental safety. In summary, the use of potassium carbonate prepared slow-release silicon modified potassium magnesium slag system is feasible, the study for the resource utilization of magnesium slag and fertilizer preparation provides a new idea that is of great significance to solve the environmental problem of magnesium slag piling and fertilizer loss caused.

【学位授予单位】：山西大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ443

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