蟹壳富钙生物炭吸附回收磷酸盐的机理研究

Biochar is promising in phosphorus recovery due to the fact that biochar is efficient in soil amendment and remediation, and phosphorus loaded biochar is more suitable for agricultural application compared to traditional phosphorus adsorbent. However, biochar from common lignocellulosic biomass is poor in bivalent or trivalent metal elements, and it is necessary to dope these elements into these common biochar to make it highly efficient in phosphorus adsorption, like the lanthanum-doped biochar prepared in our previous study. Considering this, we put forward a novel strategy to directly prepare biochar-based phosphorus adsorbent from calcium-rich waste biomass of crustacean (e.g., crab shell). We have conducted the preparation and characterization of calcium-rich biochar from crab shell, and confirmed its high performance in phosphorus adsorption. Herein, the overarching objective of this study is to provide theoretical basis for phosphorus recovery by calcium-rich biochar from crab shell. The specific aims of this study are to investigate the macro- and micro-mechanisms of phosphorus adsorption by static and dynamic adsorption experiments and various physical and chemical analysis methods, to establish relations between physicochemical properties and phosphorus adsorption performance, to reveal phosphorus speciation of biochar after phosphorus adsorption and specify key influencing factors, to elucidate the phosphorus release characteristics of phosphate-loaded calcium-rich biochar, and to analyze phosphorus availability of phosphorus-loaded calcium-rich biochar in soil as slow-releasing phosphorus fertilizer. The results of this study can enrich the methods for preparation of biochar-based phosphorus adsorbent and provide a new material for phosphorus recovery from wastewater.

生物炭具备土壤改良与修复等功能，其磷吸附产物更适宜于农业应用，因此生物炭在磷回收方面具有重要的应用前景。然而常规木质纤维生物质来源的生物炭中二价或三价金属元素的含量较低，需要额外掺杂这些成分才能使其具备高效磷吸附功能，如申请人在前期研究中制备的掺镧生物炭。针对这一问题，申请人提出了利用钙含量高的蟹壳等甲壳类废弃生物质为原料直接制备生物炭基磷吸附材料的新途径，在前期研究中已制备了蟹壳富钙生物炭并分析了其理化性质，初步验证了其较高的磷吸附性能。在此基础上，本研究将利用静态和动态吸附实验方法及多种理化表征手段指明其吸附磷酸盐的宏观及微观机理，明确其吸附磷酸盐的构效关系，解析其磷吸附产物磷形态的分布规律及关键影响因素，指明磷吸附产物的磷释放特征及在土壤中作为缓释磷肥的有效性，最终为其在磷回收中的应用提供理论基础。本研究的结果将丰富生物炭基磷吸附材料的制备途径，并为废水磷回收提供新材料。

近年来生物炭的研究及应用得到的迅猛的发展，但目前生物炭主要来源于木质纤维生物质，而非甲壳类废弃生物质。因此本项目以蟹壳为代表性甲壳废弃物，考察了不同温度条件下所得的蟹壳富钙炭的理化性质，并通过批吸附实验及理化表征手段考察了蟹壳炭对磷酸盐、染料和抗生素等多种类型污染物的吸附性能及机理。研究结果表明，蟹壳炭具有层状纳米结构、超低的C/N、超大的石墨相区尺寸、超高的zeta电位和超丰富的矿物质钙（碳酸钙或氧化钙），这些特征明显区别于常见的木质纤维生物质来源的生物炭。正是由于蟹壳炭的这些性质，使得蟹壳炭对多种污染物都具有高效的去除性能，如对磷的最大吸附量超过100mg/g，而对阳离子型染料孔雀石绿和阴离子型染料刚果红的最大吸附量更是分别可以超过10000和20000mg/g，对金霉素的最大吸附容量也可以达到1400mg/g。同时，蟹壳炭对有机污染物（如染料）具有超快的吸附速率，如吸附刚果红的平衡时间小于2分钟。另外本项目也首次证明了蟹壳炭在低浓度金霉素中主要通过吸附来去除金霉素，而在高浓度金霉素中则是通过絮凝来去除金霉素。因此本项目的研究结果可以为甲壳类废弃生物质的资源化利用提供新的途径，也可以为环境污染的治理提供新型高效材料。目前蟹壳炭的制备及应用已获得授权发明专利1项。