镁改性牛龚生物炭对农田土壤磷吸附性能及其机理研究

发布时间：2019-02-18 13:04

【摘要】：磷是导致水体富营养化的元凶之一,进入水体中磷的源头主要有工业、生活的点源排放和农业的面源流失。随着点源排放的有效控制,农田面源磷流失成为了重点治理对象。在解决方法上,采用在土壤里添加吸附剂从磷污染源头控制是最直接有效的手段,既可避免磷的流失造成污染,还可以在后期作为缓释肥料给植物提供营养。近年来,生物炭因其特殊的环境功能被广泛研究,并用于农田中营养元素流失的控制。为深入探讨生物炭在控制农田面源磷污染上的潜力,本研究采用香格里拉本地牦牛粪作为生物炭原料,用镁离子将其改性以制备出对农田土壤中溶解性无机磷和有机磷有较强吸附能力的改性生物炭,并应用土柱模拟实验测定其吸磷和对土壤的改良效果。同时通过研究改性生物炭对无机磷和有机磷的吸附动力学和吸附等温线模型探讨其吸附机理。其研究结果表明:(1)将风干、破碎后的牛粪用浓度为2 mol/L的镁离子溶液充分浸渍2小时后烘干,然后用马弗炉在充氮气的条件下以5℃/min的升温速率最终温度分别为300℃、450℃和600℃C热解3小时,待其自然冷却后便得到实验所需改性生物炭(分别记为MBC300、MBC450和MBC600)。结果发现他们对磷的吸附能力为MBC600MBC450MBC300。比未用镁离子改性生物炭对磷具有更强的吸附能力,600℃下烧制的改性生物炭对无机磷和有机磷的吸附能力分别提高了 39.89倍和1.33倍。理论上可将其用于控制农田土壤中溶解性无机磷和有机磷的流失。(2)通过对改性生物炭表面形态、比表面积、元素分析、pH值进行研究发现:热解温度越高,改性生物炭的表面越粗糙、比表面积越大、C、H、O、N元素含量减小、pH越高。(3)通过用XRD对镁改性生物炭进行表征,发现其表面生成了许多MgO晶体和水合氯化镁晶体,由于MgO晶粒在溶液中常带正电,进而吸附带负电的磷基团,同时生物炭上的水合氯化镁则易与磷发生化学结合生成微溶的磷酸二氢镁(Mg(H2PO4)2)和磷酸氢镁(MgHPO4)等而附着在生物炭表面。从理论上解释了镁改性生物炭可以有效的吸附磷,而达到控制磷的流失。(4)分别通过测定MBC600对无机磷和有机磷的吸附能力测定,发现它们都比较符合准二级动力学和Langmuir吸附等温线模型,MBC600对磷的吸附主要是以均匀的单分子层吸附方式为主的化学吸附,其理论最大吸附量分别可达19.18 mg/g 和 26.12 mg/g。(5)将镁改性生物炭加入到土柱中进行淋溶实验来模拟,通过对收集的淋滤液进行体积、pH和磷含量的分析,解析其输入农田后对磷流失的控制,结果表明它不仅在前期可以减缓磷的流失,还能在后期持续释放磷(P的解析率达100%),缓慢为植物提供营养,可以起到了先控制磷污染然后作为缓释肥料为植物提供营养的双重作用。优化的结果是MBC600在农田表层土壤应用中的最佳输入量仅为0.05%。因此,可将MBC600作为无机磷和有机磷的良好吸附剂应用到农田土壤中控制磷的流失。(6)通过以上牦牛粪的镁改性方法制备生物炭的方法和吸磷研究所得的基础数据和理论成果,为高原牦牛粪的高附加值应用开辟了一条新路径,应用于农田土壤中控制磷的流失,为改性牦牛粪生物炭应用于农田磷面源污染的防控奠定理论基础,为恢复高原退化湿地、磷污染防治提供技术支持。
[Abstract]:Phosphorus is one of the elements that lead to the eutrophication of the water body, and the source of the phosphorus in the water body mainly has the industrial and living point source discharge and the surface source loss of agriculture. With the effective control of point source emission, the loss of source and phosphorus of farmland has become an important subject. in that solution, the control of the addition of the adsorbent from the phosphorus pollution source head in the soil is the most direct and effective means, so that the pollution can be avoided, and the nutrition can be provided to the plant in the later stage as a fertilizer. In recent years, biochar has been widely studied for its special environmental function and used to control the loss of nutrient elements in farmland. In order to study the potential of biological carbon in controlling the phosphorus pollution in the farmland surface, the study adopted the Shangri-La local yak dung as the biological carbon raw material, and modified with the magnesium ion to prepare the modified biological carbon with strong adsorption capacity to the soluble inorganic phosphorus and the organic phosphorus in the farmland soil, and the soil column simulation experiment is applied to determine the effect of the phosphorus absorption and the improvement of the soil. The adsorption mechanism of the modified biochar on the adsorption kinetics and the adsorption isotherm of inorganic phosphorus and organic phosphorus was also studied. The research results show that: (1) air-dried and crushed cow dung is fully soaked for 2 hours with a magnesium ion solution with a concentration of 2 mol/ L and then is dried, and then the final temperature is 300 DEG C, 450 DEG C and 600 DEG C for 3 hours at a final temperature of 5 DEG C/ min under the condition of nitrogen filling by a muffle furnace, The biological carbon (MBC300, MBC450 and MBC600, respectively) needed to be modified in the experiment was obtained after the natural cooling. The results showed that their adsorption capacity to phosphorus was MBC600MBC450MBC300. and the adsorption capacity of the modified biological carbon fired at 600 DEG C for the inorganic phosphorus and the organic phosphorus is increased by 39.89 and 1.33 times higher than that of the modified biochar which is not modified with the magnesium ion to have a stronger adsorption capacity for the phosphorus and the modified biological carbon fired at the temperature of 600 DEG C. The method can be used for controlling the loss of soluble inorganic phosphorus and organic phosphorus in the farmland soil. (2) The surface morphology, specific surface area, element analysis and pH value of modified biochar were found: the higher the pyrolysis temperature, the more rough the surface of the modified biochar, the larger the specific surface area, the higher the content of C, H, O, and N, and the higher the pH. (3) the magnesium-modified biological carbon is characterized by XRD, and a plurality of MgO crystals and a hydrated magnesium chloride crystal are formed on the surface of the magnesium modified biological carbon, At the same time, the hydrated magnesium chloride on the biological carbon is easily chemically combined with the phosphorus to form the sparingly soluble magnesium dihydro-magnesium (Mg (H2PO4) 2) and the magnesium phosphate (MgHPO4) and the like to be attached to the surface of the biological carbon. It is theoretically explained that the magnesium modified biological carbon can effectively adsorb the phosphorus, and the loss of the control phosphorus can be achieved. (4) The adsorption capacity of MBC600 to the inorganic phosphorus and the organic phosphorus was determined by the determination of the adsorption capacity of the MBC600 to the inorganic phosphorus and the organic phosphorus, respectively. The theoretical maximum adsorption amount is 19.18 mg/ g and 26. 12 mg/ g, respectively. (5) the magnesium-modified biological carbon is added into the soil column for leaching experiments to simulate, and the control of the loss of the phosphorus after the input of the farmland is analyzed through the analysis of the volume, the pH and the phosphorus content of the collected leaching solution, and the result shows that the method not only can slow the loss of the phosphorus in the early stage, can also continuously release the phosphorus in the later stage (the analysis rate of P is up to 100%), and the plant can be slowly provided with nutrition, so that the phosphorus pollution is firstly controlled, and then the fertilizer is used as a fertilizer for supplying the plant with the double action of nutrition. The result of the optimization is that the best input quantity of MBC600 in the application of soil surface soil is only 0.05%. Therefore, the MBC600 can be used as a good adsorbent for inorganic phosphorus and organic phosphorus to control the loss of phosphorus in the farmland soil. (6) the method for preparing the biological carbon by the magnesium modification method of the yak dung and the basic data and the theoretical results obtained by the phosphorus absorption research institute, opens a new path for the high-added value application of the plateau yak dung, and is applied to the control of the loss of the phosphorus in the farmland soil, the invention lays a theoretical foundation for the application of modified yak dung biological carbon to the prevention and control of the pollution of the farmland phosphorus surface source, and provides technical support for the restoration of the high-altitude degraded wetland and the phosphorus pollution prevention and control.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S141

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