Abstract
The present study examined the effect of pyrolysis temperature on the physicochemical properties of biochar, activation process and carbon capture. Two different categories of biochars were synthesized from herbaceous (miscanthus and switchgrass) or agro-industrial (corn stover and sugarcane bagasse) feedstock under four different pyrolysis temperatures- 500, 600, 700 and 800 oC. The synthesized biochars underwent sono-amination activation comprising low-frequency acoustic treatment followed by amine functionalization to prepare adsorbents for CO2 capture. As per the elemental analysis, the elevated pyrolysis temperature resulted in increased %C and %ash contents and reduced %N contents of biochar. The textural analysis exhibited almost 3-times enhancement of micro surface area and pore volume upon increasing the pyrolysis temperature from 500 to 700 oC, though further increase to 800 oC reduced the micro-porosity and the surface area. The intermediate temperatures of 600 and 700 oC revealed the highest interactions with ultrasound-amination, which significantly intensified CO2 adsorption. Accordingly, the CO2 capture capacity of sono-aminated biochars synthesized at 600 and 700 oC were almost 200% greater than that of raw biochars. There were 127-159% and 115-151% increases in adsorption capacity of biochars synthesized at 800 and 500 oC upon ultrasono-amine functionalization. Miscanthus biochar synthesized at 700 oC and treated sono-chemically demonstrated the highest adsorption ability of 2.89 mmol/g at 70 oC and 0.10 atm partial pressure, which is 211% higher than its pristine condition. The superior adsorption capacity of miscanthus (at 700 oC) can be attributed to its large surface area (324.35 m2/g), high carbon content (84%), and low ash content (4.9%), as well as its %N content after sono-amination that was twice that of raw char.
Highlights
One of the most critical issues of this century is to accommodate the global energy demand which is increasing as a result of increased population and higher standards of living
The present study investigated the importance of pyrolysis temperature on biochar properties, acoustic-based amination of biochar, and CO2 adsorption
The biochars underwent twostep sonochemical activation: low-frequency low-temperature ultrasound activation followed by TEPA functionalization
Summary
One of the most critical issues of this century is to accommodate the global energy demand which is increasing as a result of increased population and higher standards of living. In order to reduce the concentration of greenhouse gases such as CO2 from the atmosphere, technologies need to be implemented that would (1) consume greenhouse gas emissions and (2) use bioenergy as an alternate energy source (Haszeldine, 2009). The biomass is heated to produce a gas that can be used to generate power while producing a solid by-product called biochar. This biochar can be effectively used for preparing adsorbent materials for carbon sequestration. Integrating bioenergy production with carbon sequestration would provide a viable way to mitigate the issue associated with global warming
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