LAUSR

Abstract Effects of the main variables of the Formosolv fractionation of hemp hurds (formic acid and hydrochloric acid concentrations and treatment time) on delignification and hemicellulose solubilisation were quantified. The conditions that provided a pulp with low lignin content and high cellulose content, while recovering the maximum possible amount of lignin by precipitation, are 30 min of treatment time, 86.6%w formic acid, and 0.095%w hydrochloric acid. Under these conditions, 93.2% hemicellulose removal and 72.1% delignification were achieved. The residual solid from the Formosolv treatment contained a high proportion of formate groups (8.7%w). Four total chlorine-free treatments were used to eliminate the formate groups. Only alkaline treatments (oxygen and sodium hydroxide) completely removed the formate groups. However, the ozone treatment produced a solid with the highest delignification rate (34.7%, 80.1% global) and crystalline index.