Fabrication of mesoporous lignin-based biosorbent from rice straw and its application for heavy-metal-ion removal. 
Lignocellulosic biomass offers the most abundant renewable resource in replacing traditional fossil resources.  However, it is still a major challenge to directly convert the lignin component into value-added materials.  The availability of plentiful hydroxyl groups in lignin macromolecules and its unique three-dimensional structure make it an ideal precursor for mesoporous biosorbents.  In this work, we reported an environmentally friendly and economically feasible method for the fabrication of mesoporous lignin-based biosorbent (MLBB) from lignocellulosic biomass through a SO3 micro-thermal-explosion process, as a byproduct of microcrystalline cellulose.  BET analysis reveal the average pore-size distribution of 5.50nm, the average pore value of 0.35cm3/g, and the specific surface area of 186m2/g. The physicochemical properties of MLBB were studied by fourier transform infrared spectroscopy (FTIR), attenuated-total-reflection fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and element analysis.  These results showed that there are large amounts of sulfonic functional groups existing on the surface of this biosorbent.  Pb(II) was used as a model heavy-metal-ion to demonstrate the technical feasibility for heavy-metal-ion removal.  Considering that lignocellulosic biomass is a naturally abundant and renewable resource and SO3 micro-thermal-explosion is a proven technique, this biosorbent can be easily produced at large scale and become a sustainable and reliable resource for wastewater treatment.