| With the adjustment of the structure and products of China’s paper industry raw materials, the proportion of secondary fiber in papermaking raw materials is growing. The composition of secondary fiber is complex, waste paper pulp often occur irreversible keratinocytes during the drying process, which need to discard a portion of the waste material. Waste paper has the characteristics of stable source, environmentally friendly, low-cost. The main components of these materials are cellulose, hemicellulose, and lignin. It is a potential source of bio-ethanol production, which can be used as the enzymatic hydrolysis and biomass conversion material. However, lignin and filler paper to cellulase adsorption is invalid, and affect the efficiency of enzymatic hydrolysis of waste paper. In this paper, grading process of waste paper pulp is carried out to find the main factors affecting enzymatic hydrolysis. The effect of pretreatment methods and cationic additives added on the efficiency of enzymatic hydrolysis of waste paper pulp is explored. The main conclusions are as follows:Enzymatic hydrolysis experiments are carried out after grading pretreatment. Enzymatic hydrolysis of R80-180 (R80-180 represents the range of 80-to 180-mesh secondry fiber) waste paper pulp gave the highest glucose yield (80.33%). Immediately following was the R80(R80 represents greater than 80-mesh secondry fiber) yield(79.72%). R180 (R180 represents smaller than 180-mesh secondry fiber) exhibited the lowest glucose yield (55.36%). The enzymatic hydrolysis experiments of various ratios of waste paper pulp mixtures R80 (add 1%,5%,10%,15%,20% of R80-18o and R18o respectively), the glucose yield of R80 is increasing, when the amount of R80-180 is 15%, the glucose yield is the highest. Due to the addition of R80-180, the specific surface area of the system is increased and the degree of contact of the cellulase to cellulose is increasing. The glucose yield decreased with different proportions of R180, mainly because of the low content of cellulose R180,and contains a lot of impurities, and led to the invalid adsorption of cellulase, thereby reducing activity. Through scanning electron micrographs, R80 waste paper pulp had a smooth morphology, which could be beneficial to enzymatic hydrolysis. Specific surface area of R80-180 is larger, it can be well contacted with the cellulase, and R180 surface was covered with a large amount of inorganic filler such as calcium carbonate. Thus, cellulase could not completely contact the cellulose in the pulp, thereby reducing the glucose yield.R180 were added to R80 and carried out enzymatic hydrolysis experiments, glucose yield decreases. It can be speculated that R180 contains the enzyme hydrolyzed inhibitor. Through ICP detection, waste paper pulp contains large amounts of metal ions, which Fe3+, Al3+, Mn2+, Mg2+ play a negative role in enzyme hydrolysis. The addition of EDTA can effectively eliminate the influence of metal ions.The results show that hydrogen peroxide pretreatment enzymatic hydrolysis yield is the highest (91.67%), followed by sodium sulfite pretreatment (87.57%) after Na2SO3, H2O2, HCl, water pretreatment. Through the scanning electron microscopy, surface area, crystallinity, waste paper pulp is debillicated and the numbers of small hole is increased, lignin content is decreased, the specific surface area is increased, and cellulose can be well contacted with cellulase, so that the glucose yield increased.Cationic additives (Cationic Polyacrylamides, Polyetherimide, dispersants) and a surfactant were added in waste paper pulp enzymatic hydrolysis process, the results show that under the same reaction conditions, enzymatic hydrolysis efficiency of waste paper pulp with dispersant is the highest, closely followed by PEI, surfactant, CPAM. In addition, contact angle measurement was carried out in waste paper pulp with additives, the effects of the hydrophilic on enzyme hydrolysis was investigated. The study showed that adding additives was capable of reducing the contact angle of the waste paper pulp. The contact angle of adding the dispersant is minimum (39.9°), followed by PEI, CPAM. The contact angle adding additives secondry fiber was less than that Rw(52.2°). This suggests that adding additives are capable of improving hydrophilic of waste paper pulp. Combined with enzymatic efficiency, this fully shows that the hydrophilic is an important factor in enzymatic hydrolysis. The results showed that the adsorption of cellulase, the adsorption capacity of waste paper pulp without additives is strongest before 2 h, followed by CPAM, PEI.Adsorption capacity of waste paper pulp with dispersant is weakest. It can be seen, improving hydrophilicity cf the substrate can reduce the invalid adsorption of cellulase, thereby promoting enzymatic hydrolysis. |
