ACID HYDROLISYS STUDY OF THE COFFEE FIBERS WITH ORGANIC ACIDS

The most widely used method for obtaining cellulose nanocrystals used as reinforcing agents in polymeric materials has been acid hydrolysis. Currently, sulfuric acid is the most used in fiber hydrolysis to reduce in smaller structures of celluloses. However, it has high environmental impact and cost of recovery. In this sense, the objective of this work is to cellulose isolation from the coffee husk using organic acids. Autoclaved fibers with 5% NaOH were used at 121 °C for 30 min and bleached (PTAC (B)). The hydrolysis reactions were sulfuric (S), phosphoric (F), butyric (B), tartaric (T), citric (C) and oxalic (O). Sulfuric acid was used as a control at 50% (v / v) at 40 °C for 40 min and the other acids at 50% (v / v) at 80 ° C for 40 min. The material was characterized by Infrared Absorption Spectroscopy (FTIR) and the degree of polymerization was analyzed. All samples have the same characteristic cellulose profile, with a band around 3000-3500 cm-1 attributed to the OH groups present in the cellulose structure. Among the organic acids, the one that had the greatest influence on GP on the PTAC fiber (B) was the citric acid, and the others had few differences among themselves. There was a decrease in GP of sulfuric acid hydrolyzed fibers due to the degradation of cellulose chains due to the attack of strong acid. It can be concluded that the acids used reduced the sizes of micro particulate cellulose fibers.