Isolation and characterization of microcrystalline cellulose from cotton stalk waste

An effective method for microcrystalline cellulose (MCC) isolation from cotton stalk is reported. Cotton stalk was subjected to pretreatment and hydrolysis to determine the optimum conditions for isolating cotton stalk MCC (S-MCC). The main purpose of pretreating the cotton stalk with acetic acid was to remove ash. As a result, the ash content was reduced from 5.70% to 1.10%. After acid hydrolysis, the remaining ash was removed. Based on the single factor and orthogonal experiments, the optimum hydrolysis conditions were 85 °C, 1 mol/L HCl, 90 min, and a solid-to-liquid ratio of 1:10. The results showed that the reaction temperature and time strongly influenced the yield and size of the S-MCC particles. In addition to the yield, D90 was shown to be a good parameter to represent the degree of cellulose hydrolysis. The S-MCC had an ash content of 0.06%, α-cellulose content of 98.6%, moisture content of 4.64%, degree of polymerization of 146, and crystallinity index of 80.3%. These chemical and physical properties were comparable to those of commercial MCC. Other structural characterizations were determined by Fourier-transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy, and compared with commercial MCC.