Enhanced separation of cellulose from bamboo with a combined process of steam explosion pretreatment and alkaline-oxidative cooking

A synergistic process with steam explosion pretreatment (SEP) followed by sodium carbonate-oxygen cooking (SCOC) upon bamboo was evaluated for its effect on separating hemicellulose and lignin from bamboo while preserving cellulose, providing cellulose substrate susceptible to chemicals in producing platform chemicals such as levulinic acid. The results showed that through the SEP with 2.5 MPa for 10 min, the hemicellulose content reduced by 60.85 %, the specific surface area of bamboo fiber increased to 1.9494 m from 0.8061 m of raw material. The synergistic SEP-SCOC significantly removed 73.33 % lignin, and yielded 73.9 % cellulose under the optimal condition of SEP with 2.5 MPa for 10 min and followed by SCOC with 30 % total titratable alkali (TTA) at 180 °C for 2 h and 2 MPa oxygen pressure. The results also proved the total lignin removal was improved by 8.07-18.95 % for the steam exploded bamboo fibers than the untreated one, indicating SEP increased the accessibility of cooking reagents to fibre during subsequent SCOC process. Furthermore, the low value of biological oxygen demand (BOD) and chemical oxygen demand (COD) in the final spent liquor indicated the lower pollution level of the process.