云南泥炭和褐煤制备腐植酸磷肥的物理化学特性研究

Yunan has vast reserves of peat and lignite, which are rich in carboxyl and hydroxyl structure that provides the opportunity of producing organic chemicals and organimineral fertilizers instead of the conventional utilization as fuel. Comparing to conventional fertilizers, the use of humic acid fertillizers has the potential of increasing the uptake and availability of phosphate, in the meanwhile, decreasing the fixation of phosphorus in soils. This work will focuse on producing effectively humic acid from peat, leonardite and lignite originated from Yunnan, followed by producing compound fertilizer based on the blend of humic acid, metal salt and/or phosphate rock. To achieve the targeted products, this study will firstly investigate the relationship between the property, structure, maceral constituents of lignite, as well as extractants and process parameter on extraction yield and chemical structure and the compositions of the produced humic acids. Secondly, this work will explore some effective methods for characterizing the composition and structural features of humic acids and phosphorus fertillizers that contain phosphate-metal-humic complexes with polar groups. Thirdly, the characteristics of Humic acids extracted from peats, leonardites and lignites will be distinguished by fluorescence spectrometry, combining alkali solution absorbance method and electrofocusing to reveal its influence on the properties of Humic acid fertillizers. For the purpose of producing a stable metal (M) bridges (PMHA) by chelating phosphate and humic acids, (HA)this study will also explore the suitable conditions for the reactions between humic acid and phosphate rock, reaction mechanism, preparation techniques and coordination structure. Finally, the quantum chemical study will be carried out using molecular modeling (density functional theory (DFT) / ab inito method) to test the experimental results. If succeeded, this work will provide a theoretical basis for highly efficient utilization of lignite from Yunnan, and benefit the integration of coal chemical industry and phosphorus chemical industry.

云南省泥炭和褐煤资源丰富，从其富含羧基和羟基的结构出发，用其生产有机化学品和肥料是其非燃料利用的主要途径。腐植酸磷肥可保护水溶性磷，抑制土壤对磷的固定。本项目从云南泥炭、风化褐煤和褐煤中提取腐植酸，腐植酸与金属盐和磷矿粉反应制取腐植酸磷肥。系统研究褐煤的岩相组成、性质和结构、显微组分、不同萃取剂、工艺条件与腐植酸提取率和腐植酸结构的关系。针对腐植酸极性强的特点，研究腐植酸的组成和结构的表征方法。利用分子荧光光谱法，碱溶液吸光度法和等电聚焦相结合区分不同原料制备的腐植酸。研究腐植酸和磷矿粉反应的工艺条件、反应机理、制备技术和配位结构，使磷酸盐（P)通过金属(M)与腐植酸(HA)形成稳定的络合物（PMHA)，采用密度泛函从头算法进行量子化学模拟，计算PMHA的稳定性和配位结构并与实验结果比较。研究HA组成、结构对腐植酸磷肥的结构及性质的影响。本项目有助于云南省褐煤和磷肥的的高效利用。

腐植酸通常可用作肥料、土壤改良剂、钻井助剂、蓄电池阳极，及医药产品等。以高腐植酸煤为生产原料，提取和开发腐植酸类产品，是实现云南褐煤高附加值分质分级利用的重要途径。因煤炭结构特性的复杂性致使不同煤种所制备的腐植酸类产品的性能具有显著差异。研究煤种有云南省昭通、弥勒、峨山、寻甸金所、黑龙江宝清等高腐植酸褐煤，乌海风化煤、离石风化煤、新疆风化煤，云南石屏赤瑞湖泥炭和辽宁新宾泥炭，重点考察腐植酸提取和物化性能的关系；对低腐植酸含量的云南宜良、宣威褐煤、富宁褐煤和内蒙古呼伦贝尔褐煤进行氧化以提高腐植酸含量，制备再生腐植酸。以小麦、棉花种子发牙、盆栽实验等方法研究腐植酸的生物活性。制备了硝基腐植酸和腐植酸磷肥等肥料，研究了植物生长与施用不同种类腐植酸肥料的变化规律。以期为后续腐植酸生产、利用及产品开发提供理论指导。采用红外光谱、拉曼光谱、X射线光电子能谱、固体核磁、X射线衍射、顺磁共振谱、热解-气相色谱-质谱，热重-红外、热重-差示扫描量热等现代分析技术对煤质特性以及提取的腐植酸进行了多尺度表征分析，获得了云南省昭通、弥勒、峨山褐煤和黑龙江宝清褐煤的分子结构模型，获得了腐植酸的结构特性。实验结果表明昭通煤具有高芳香度、高羧基含量、低自由基含量的基本结构特征；弥勒褐煤具有高脂肪链结构、高自由基含量等基本结构特征，造成其结构差异的可能原因与两种煤的成煤因素有关。将煤质特性和腐植酸特性进行了关联，研究表明，腐植酸提取的最佳工艺参数取决于煤种，腐植酸的总酸性基团含量和芳香度皆为风化煤腐植酸>褐煤腐植酸>泥炭腐植酸。不同溶剂提取的腐植酸的特性不同，NaOH溶剂是最佳的提取溶剂。腐植酸的热稳定性和热氧化性与煤的结构特征密切相关，有机结构化学键的强弱是影响热稳定性高低的关键。芳香度高的褐煤所提取的腐植酸热稳定性较好，而热氧化性除了与有机结构有关外，还与结构中的含氧基团有关，较多的含氧基团可在一定程度上增强腐植酸的热氧化性能。通过盆栽实验可知不同原料制备的肥料对紫苏和白菜生产影响作用和产量的促进作用影响不同。双氧水和硝酸氧化的生物活性比机械氧化强，因此能在较低的浓度下就能达到很好的促进种子萌发作用，腐植酸能加速小麦种子的萌发，不会改变最终的种子萌发率，腐植酸浓度过高时会产生抑制作用。