Preparation and characterization of microcrystalline cellulose from olive stones

Microcrystalline cellulose (MCC) is a bio-based material obtained from purified and partially depolymerized cellulose. The need for cheaper sources of MCC has led to the exploration of other lignocellulosic material based on agricultural residues. Hence, in this study, olive stones were chosen as olive industry produces 37,500 tons of olive-stone waste every year. Microcrystalline cellulose was prepared by acid hydrolysis using hydrochloric or sulfuric acids then bleached. Characterization of the prepared MCC was carried out using attenuated reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and thermal gravimetric analysis (TGA). The crystal structure was studied using XRD. The surfaces of prepared samples were investigated by field emission scanning electron microscope (SEM). In addition, surface area and pore size, as well as particle size distribution of the prepared samples, were measured using nitrogen absorption isotherm and dynamic laser light scattering, respectively. The particle size of samples prepared with sulfuric acid was smaller and therefore the surface area was higher than in case of samples prepared using hydrochloric acid. However, the hydrochloric acid prepared MCC had higher thermal stability than the other sample prepared using sulfuric acid. The properties of prepared MCCs were compared to the commercially available MCC (Avicell PH 101); the results showed good agreement in most properties between olive stone MCC and the commercial one.