Pretreatment of lignocellulosic waste as a precursor for synthesis of high porous activated carbon and its application for Pb (II) and Cr (VI) adsorption from aqueous solutions.

Effects of Elm tree sawdust pretreatments using alkali and alkaline earth metals (NaCl, KCl, CaCl2, MgCl2 and Elm tree ash) and deashing solutions (water, HCl, HNO3 and aqua regia) before the carbonization process on the porosity of produced activated carbons and Pb (II) and Cr (VI) adsorption were studied. The activated carbons were characterized by pore size distribution, surface area, FTIR, and SEM-EDX analysies. Based on the results, HCl leaching pretreatment of the biomass increased the activated carbon adsorption capacity of Cr (VI) from 114 to 190 mg g-1. The treatment of biomass with alkali and alkali earth metal salts, especially MgCl2, remarkably increased the activated carbon adsorption capacity of Pb (II) from 233 to 1430 mg g-1. The results indicated that Pb (II) adsorption was attributed to both the mesoporous structure of activated carbon and the abundance of Mg on the activated carbon's surface. On the other hand, the micropores played a major role in Cr (VI) adsorption capacity. The development of the micro- or mesoporous structure of activated carbons through pretreatment of lignocellulosic precursor could be an approach for providing high performance activated carbons for Pb (II) and Cr (VI) removal from aqueous solutions.

Investigating the morphology and reactivity of chars from Triplochiton scleroxylon pyrolysed under varied conditions.

A gasifier may be optimised via a good understanding of the char formation, morphology and reactivity. The effects of varying the pyrolysis pressure and heating rate on the morphology of the char were investigated using a thermogravimetric analyser (TGA), scanning electron microscope (SEM) and micrograph spot analyser. The gasified chars were produced at heating rates of 5, 10 and 20°C/min and pressures of 0.1, 0.4 and 0.6 MPa. All the chars have different degrees of apparent gasification reactivity. The random pore model (RPM) provided a better description of the experiment, with low average error values, θ, in all of the cases considered. The alkaline and alkaline earth metals (AAEM) in the tropical wood biomass Arere (Triplochiton scleroxylon) consist predominantly of calcium and could altogether be partly responsible for the noticeably high reactivity nature of the tropical Arere chars.