Production and Characterization of Activated Biochar by Co-Pyrolysis of Delonix Regia Biomass and Sodium Hydroxide

Abstract Co-pyrolysis of Delonix regia (DR) and sodium hydroxide (NaOH) has been carried out at 600°C and for 2h in tubular reactor externally fitted with electric furnace. NaOH in co-feed was varied 10–30wt.% relative to mass of DR. Biochar was washed with deionized water to remove wastes and physically attached sodium from the biochar by ultrasonication for 2h. Bio-oil yield was increased with fraction of NaOH in co-feed whereas reverse was true in case of bio-char yield, but yield of non-condensable gases was unaffected. Bulk and tapped densities of biochar were increased with NaOH and these values were higher than those of raw DR biomass feed, whereas reverse was true in case of interparticle packing voidage. HHV of biochar was 23.32MJ/kg when 10% NaOH was co-fed and then by further increasing NaOH, it decreased to ≈20MJ/kg. EDX showed that major fraction of biochar was occupied with carbon (67.2–71.5%), followed by oxygen (15.1–17.1%), and nitrogen (6.4–9.5%) whereas sodium was present in lowest (1.5–3.5%). XRD indicated that biochar crystallite size was large with 43.33nm by DR and 10% NaOH co-pyrolysis and it slightly decreased to 36.62–38.57nm with further NaOH fraction increment. BET indicated that biochar by pyrolysis of DR alone has low surface area but that of by co-pyrolysis of DR and 10% NaOH has highest surface area of 53.8 m2/g.