Tailoring the difference - Tailored biochars for sustainable water treatment: Customizing adsorbents for specific applications

The rapid development of modern society increased the demand for sustainable resource use and switch from fossil resources to greener naturally based alternatives. Together with the world, the water treatment field is looking for ways to implement environmentally friendly solutions and reduce emissions. One of process optimization directions is substitution of activated carbon for adsorption process. Activated carbon is produced from fossil coal, which excavation and transportation have a significant carbon footprint. A potential alternative material for activated carbon is a carbonous adsorbent produced from locally available and renewable biomass, also called biochar. However, the adsorptive properties of biochar cannot compete with the conventional activated carbon and thus require improvement. The adsorptive properties can be improved via manipulation and adjustment of biochar production conditions. This adjustment process is called tailoring. The systematic understanding of the tailoring possibilities is missing despite the extensive research on biochar modification. This dissertation attempts to introduce insights in the knowledge gaps about tailoring and produce a big-picture vision on the process. Due to the broadness of the topic, the dissertation has its boundaries. It focuses on the main factors which affect biochar properties, namely biomass, activation method and temperature control. The compiled from four articles study describes how each production factor affect the final properties of the produced adsorbent, and what challenges they introduce to the tailoring process. Moreover, the dissertation emphasizes how the connection of production factors within the tailoring process can improve the tailored biochar properties. To study the properties of the tailored biochar, the study uses batch adsorption method and utilizes scanning electron microscopy and specific BET surface area measurements for characterization. Finally, dissertation reflects on the implications of the tailoring process in the future. The improvement of biochar properties via the implementation of tailoring in the biochar production process will make biochar an attractive green substitute for activated carbon on adsorbents market. The local availability and optimized production process of tailored biochar would benefit the water treatment field environmentally and economically. Yet, at this moment the tailoring is a theoretical concept which is studied mostly in laboratory scale. The practical implementation of tailoring is not possible without a structured understanding of the process and consideration of the possible limitations. Thereby, mainly the options for further investigation are gathered in the study.