Preparation and Characterization of Crop-Waste Biochars

Biochar is a carbon-rich and porous material; it is produced through the pyrolysis of waste biomass. This material is capable of adsorbing chemical constituents from water, air, or other media. This capability has allowed it to become an alternative water filtration option potentially comparable to activated carbon. Raw biomass crop waste including cotton hull, pecan shell, and rice husk were converted to biochar through Top-Lifted Updraft (TLUD) and Muffle Furnace (MF) pyrolysis processes. The material properties of these biochars have been characterized through the use of XRD, FTIR, TGA, DSC, SEM, and BET surface area analytical tools. The analyses reveal the physical and chemical characteristics of the raw materials and biochar. XRD analysis of the raw materials and biochars shows that these materials are noncrystalline (amorphous). FTIR analysis shows the presence of O-H, C-H, C-C, CH2, C-H, and C-O-C functional groups in the cellulose structure of the raw material; this ensures that an oxidizer is present in the cellulose structure of these raw materials. The crop waste biochar predominantly contain the C-O-C functional groups. TGA and DSC analyses show that raw materials and biochars undergo pyrolysis at around 260°C and 340°C, respectively. This indicates a higher thermal stability of biochar and a greater availability of oxidizer in the raw materials. The raw crop wastes undergoes pyrolysis at lower temperatures than biochar. SEM images show the porous structure in biochar while the BET surface analysis reveals the pore size distribution. The presence of a porous structure and active functional groups in biochar makes them an excellent candidate as a filter and membrane for the removal of pollutants from water. The fact that a quality biochar sorbent, as shown in this can study, can be made from commonly found crop waste by inexpensive, simple pyrolysis techniques demonstrates its usefulness in many environmental and chemical process applications.