GOALI: Understanding the anomolous adsorption capacity of hydrothermal char

1605916 timko水热炭是一种廉价的碳基材料，通过在液态水存在下加热废原料合成。水热炭最近引起了人们极大的兴趣，因为它们在从土壤添加剂到电催化的各种应用中表现出了良好的性能。这个GOALI项目的目的是了解和控制水热炭对无机和有机化合物的异常高的吸附能力。这种吸附能力可以用来隔离对环境有危害的化合物。该研究将与Cabot公司合作进行，Cabot公司将提供复杂水热炭材料的综合表征。该项目的成果将被纳入伍斯特理工学院？学生专题课程。研究小组将与总部位于伍斯特的非营利组织“有毒土壤破坏者”合作，进行额外的研究和指导。水热炭虽然比表面积相对较小，但具有显著的吸附能力。据推测，表面结合的羧酸基团自缔合介导了一种只有在提供氢键的分子存在下才能进入的超微孔结构。使用分子氮的传统气体吸附测量不能打开羧酸门控的超微孔结构，导致低表观表面积。然而，羧酸在水中去质子化，水热炭结构膨胀，模拟水凝胶在适当pH条件下的膨胀。因此，水热炭的吸附能力是其实际表面积远大于测量表面积的结果。为了验证这一假设，将使用两种单独的球磨技术来独立控制水热炭的表面积和表面化学性质：(1)用于修饰水热炭表面组成的干式球磨技术，以及(2)溶剂辅助湿式球磨技术，该技术可增加碳质材料的表面积。利用这两种相关技术，PI将系统地研究水热炭的吸附能力，以确定为什么水热炭的吸附能力与活性炭的吸附能力相当，尽管水热炭的氮测量表面积不到活性炭测量表面积的1%。该项目的三个目标是：(1)了解表面积和吸附能力之间的关系，使用反应气铣削来改变表面组成；(2)了解测量表面积与吸附能力之间的关系，采用溶剂辅助磨粉技术增加热解生物炭的测量表面积；(3)通过测量一系列具有不同特性和分子大小的山梨酸酯的吸附特性来测试水热炭超微孔区域的羧酸浇注。通过解开表面面积和表面组成的竞争效应，结果将为水热炭的显著吸附能力提供坚定的理解。

1605916TimkoHydrothermal chars are inexpensive carbon-based materials that are synthesized by heating waste feedstock in the presence of liquid water. Hydrothermal chars have recently attracted significant interest because they exhibit promising performance in a variety of applications ranging from soil additives to electrocatalysis. The objective of this GOALI project is to understand and control the unusually high adsorption capacity of hydrothermal chars for inorganic and organic compounds. This adsorption capacity can be exploited to sequester compounds that pose environmental risks. The research will be performed in collaboration with Cabot Corporation, who will provide comprehensive characterizations of complex hydrothermal char materials. Results from the project will be incorporated into Worcester Polytechnic Institute?s student projects curriculum. The research team will partner with the Worcester-based non-profit group, The Toxic Soil Busters, for additional research and mentoring.Hydrothermal chars have remarkable adsorption capacities despite their relatively low surface areas. It has been hypothesized that surface-bound carboxylic acid groups self-associate to mediate an ultramicropore structure that is accessible only in the presence of hydrogen bond donating molecules. Traditional gas sorption measurements that use molecular nitrogen do not open the carboxylic acid gated ultramicropore structure, resulting in low apparent surface areas. However, the carboxylic acids deprotonate in water, and the hydrothermal char structure swells, mimicking the swelling of a hydrogel under appropriate pH conditions. Therefore, the sorption capacity of hydrothermal char is a result of its actual surface area being much greater than measured. To test the hypothesis, two separate ball milling techniques will be used to independently control the surface area and surface chemistry of the hydrothermal chars: (1) a dry-milling technique that is useful for modifying hydrothermal char surface composition, and (2) a solvent-assisted wet-milling technique that increases the surface area of carbonaceous materials. Using these two related techniques, the PI will investigate systematically the adsorption capacity of hydrothermal char to determine why measured adsorption capacities of hydrothermal chars are comparable to those measured for activated carbon, despite the fact that the nitrogen-measured surface areas of hydrothermal chars are less than 1% of those measured for activated carbon. The three aims of the project are: (1) to understand the relationship between surface area and sorption capacity using a reactive gas milling to modify surface composition; (2) to understand the relationship between measured surface area and sorption capacity, using solvent-assisted milling as a technique for increasing measured surface areas of pyrolysis biochar; and (3) to test the carboxylic acid gating of hydrothermal char ultramicropore area by measurement of sorption characteristics for a series of sorbates with varying characteristics and molecular sizes. By disentangling the competing effects of surface area and surface composition, the results will provide a firm understanding of the remarkable sorption capacities of hydrothermal chars.