Retrievable and Reusable Nanoparticle-Pinched Polymer Brushes Enable Highly Efficient Microalgae Dewatering for Cost-Effective Biofuel Production

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1160291LiangVarious analyses based on the production rate and environmental considerations have suggested that biofuels from microalgae are likely the only realistic substitute capable of releasing our reliance on fossil fuels. Despite decades of effort, commercial production of microalgae-derived biofuels has not emerged because current technologies for microalgae dewatering add a huge cost to the final product, and present a major barrier between algaculture and biofuels. A knowledge gap exists in the underlying principles governing microalgae dewatering, particularly for the rational design of coagulation agents. The long-term goal of the proposed work is to understand the underlying principles that govern the stability of a colloidal suspension of living cells, and to direct the phase separation of free-floating cells in a controllable fashion. The overall objective of this proposal is to identify the rational correlations between inter-algal pair interactions and coagulation-agent structures in order to achieve highly efficient microalgae dewatering at a negligible cost. The central hypothesis is that nanoparticle-pinched polymer brushes, i.e., radiating polymer chains covalently bonded to a nanoparticulate core, are far more effective in dewatering microalgae than conventional flocculants; in addition, using solid-state nanoparticles allows low-cost operations (e.g., using magnetic fields) to be designed to collect algal biomass and retrieve the coagulation agents for multiple cycles of microalgae dewatering, which further reduces the operational cost significantly. We have formulated this hypothesis based on our strongly supportive preliminary data. The rationale underlying the proposed research is that, once the structural characteristics responsible for the unusually high performance of this novel coagulation agent are understood, precise control of its structure is expected to enable unprecedentedly cost-effective microalgae dewatering. Hence the bottleneck preventing commercialization of microalgae-derived biofuels will be cleared. We plan to test our central hypothesis and accomplish the overall objective of this application by pursuing the following three specific aims: 1. Identify a facile and highly efficient approach to synthesize paramagnetic nanoparticle-pinched polymer brushes with well-defined structures; 2. Determine how the microalgae dewatering efficiency is regulated by the structural characteristics of the coagulation agents; 3. Determine the efficiency of retrieving nanoparticle-pinched polymer brushes for continuous cycles of microalgae growth and dewatering. The expected contribution of this work is to determine the structural characteristics of engineered coagulation agents that endow them with an unusually high efficiency in microalgae dewatering and an unusually low operational cost. This contribution is significant, because it creates a class of super coagulation agents via examining rational correlations between inter-algal pair interactions and flocculants of well-defined structures. This aspect has been poorly understood despite decades of relentless trial-and-error experiments with commercially available chemicals. Energy and environment represent the top challenges for the sustainable development of our societies. It is well understood that securing renewable energy sources is the grand challenge of our time, but it is not always recognized that any engineered material proposed to address that challenge must be sustainable itself, an example is the design of microalgae coagulation agent in this application. The researchers plan to bring broad societal awareness on this aspect with the following integrated activities: Incorporating research into teaching. The assembled research team will be a nucleus to enhance biofuel research at Mines by giving seminars, developing course materials, and attracting industry sponsorship. The PI will build a webpage devoted to microalgae harvesting issues, and disseminate the video clips of microalgae dewatering experiments to Youtube to advertise sustainable materials for sustainable energy; Outreach to Underrepresented Groups. The researchers plan to build a focused and sustainable outreach program by developing lecture materials and classroom demonstration experiments on algal biofuels, which will be used by the PI and his graduate students, to participate in an existing outreach program at Mines that spans grades kindergarten through the twelfth in two school districts, Adams County District 50 (AC50) and Meeker County (MC). Both school districts are rurally located and have a high proportion of students who are living in poverty