EVALUATION OF THREE LIGNOCELLULOSE BIOMASS MATERIALS (BARLEY HUSK, CORN COBS, AGAVE LEAVES) AS PRECURSORS OF ACTIVATED CARBON

Lignocellulosic biomass is a promising alternative and renewable energy source that can be transformed into other value-added products such as activated carbon. The objective was to evaluate the barley husk (Hordeum vulgare L.), the corn cobs (Zea Mays L.) and the agave leaves (Agave salmiana) as potential precursors of activated carbon. These precursors were obtained from Almoloya and Apan in the State of Hidalgo, Mexico. The raw materials were washed with distilled water, dried at 105 ºC for 72 h in an oven, ground in a blade mill to obtain a particle size of 0.3-1.0 mm and finally sieved through mesh sieves of 18 and 45. Humidity was determined according to ASTM D3173 (ASTM, 1996), ash according to ASTM D3174 (ASTM, 2000), volatile matter according to ASTM D3175 (ASTM, 1997), fixed carbon according to ASTM D3172 (ASTM, 1997), total sugars and fats according to TAPPI T204 (TAPPI, 1997), Klason Lignin according to TAPPI T222 (TAPPI,   1998), holocellulose according to the method described by (Wise et al., 1946), and (, ( and ( cellulose according to TAPPI T203 (TAPPI 1999). The results show that contents from 82 to 83% for holocellulose, from 52 to 79% for cellulose, and from 15 to 26% for lignin, were determined. Elemental analysis showed high carbon contents with values of 42-45%. Particle sizes between 390.9 mm and 610.7 mm were found. Thermogravimetric analysis showed similar profiles of thermal decomposition, being cellulose the main stage, with peaks around 300 °C. Regarding the surface morphology, the lignocellulosic residues showed fibrous and porous structure. From these findings, it is established that the precursors analyzed can be considered as potential precursors of activated carbons. The results presented here may facilitate improvements in the pyrolysis and activation areas of this lignocellulosic residues. The conditions for an acceptable yield of biochar were tested, these were: carbonization temperature of 400 °C, carbonization time of 30 min, precursor mass of 2-10 g and N2 flow rate of 150 cc/min. The biocarbons produced under these conditions were physically and chemically characterized. Biochar yields of 19.75% were obtained for corn cob (CCB), 32.88% for barley husk (BHB) and 31.14% for Agave salmiana leaves (ALB). Biocarbons with a predominantly macroporous structure, amorphous structure, numerous oxygen functional groups, anionic surface and moderate ash content were obtained. The results of this investigation show that barley husk, corn cob, and agave leaves are likely precursors for biochar production with good dye adsorption capacities.