Isolation and characterization of mesoporous cellulose from citrus and mango waste

This thesis reports the isolation and characterization of mesoporous cellulose-derived from citrus and mango wastes. Cellulosic matter was isolated successfully using hydrothermal microwave processing technology over a range of temperatures from 140 – 200 oC in good to moderate yield (approx. 5 % by weight and dependent on variety).
Optimum cellulosic yield for orange peel was 12.5% at140oC.The effect of pre-processing of orange peel, i.e., removal of pectin either by enzymes or microwave radiation, prior to microwave-assisted cellulose extraction was investigated. Thus the effect of extraction temperature and the effect of method of extraction on quality of cellulose were investigated. The cellulose produced from enzymatic + microwave method was comparatively of better quality than microwave + microwave even at lower temperatures. ATR-IR revealed that the cellulosic matter produced was in good agreement with the commercial microcrystalline cellulose. Porosimetry data showed that the cellulose obtained had surface area (BET) of 178.5 m2 g-1, pore volume of 0.40 cm3 g-1 and average pore diameter in the range 91.6 Å, indicating a very high propensity of mesoporous character with limited microporosity.C13 solid state NMR and XRD data revealed that at 180 oC the cellulose had a higher degree of crystallinity and that the amorphous regions depolymerised to give sugars.
Extraction of mesoporous cellulose from mango peel waste from different originsunder the optimized conditions was also investigated; it was found that microwave hydrothermal treatment at 180 oC provided the isolation of mesoporous cellulose from the peel waste. It was also observed that cellulose extracted from Alphonso peel (India) had higher porosity (124 m2 g-1) and pore volume (0.38 cm3 g-1) compared to cellulose extracted from Honey peel (Pakistan).
Both citrus and mango wastes both contain inherently structured cellulosic matter. Structuring may be provided by a combination of pectinaceous matter and hemicelluloses which when removed afford crystalline mesoporous cellulose.