Using microwave assisted organic acid treatment to separate cellulose fiber and lignin from kenaf bast

Abstract

According to diverse application purposes, different scales of lignocellulosic fibers were obtained from biomass through various preparation conditions. However, the pollution in the fiber separation process restricted the development of the related industry. This research proposed clean fiber separation technology of kenaf bast that combined microwave and lactic acid treatment. The traditional sulfate method was also carried out for comparison. The raw kenaf bast and produced fibers were characterized with wet chemistry analyses, SEM, FTIR, GPC and NMR. The results showed that compared with the traditional method (lignin removal rate 88.3 %, cellulose Mw = 607 kg/mol), the new method had higher lignin removal capacity (94.68 %) and less damage to cellulose (Mw = 1174 kg/mol). TG and NMR analysis showed that the separated crude lignin had a high pyrolysis temperature (350℃), minor structural changes and better uniformity, which was close to natural lignin. In addition, it was calculated that the processing time of the new method was reduced by 82.3 %, which reduced energy loss and waste liquid pollution. This study proved that microwave-assisted lactic acid treatment could separate kenaf fibers efficiently with less damage and pollution.