Characterization of Urea Encapsulated by Biodegradable Starch-PVA-Glycerol

The influence of the blending ratio of biodegradable starch/polyvinyl alcohol (PVA)/glycerol in encapsulating urea has been investigated. It is found that water absorption capacity increased approximately 135 % as the amounts of starch, PVA and glycerol in the composite film increase. Therefore, the swell ability of the composite film is increased and the urea is released from the composite film in the wet environment. The FTIR shows that the urea had been encapsulated successfully in the composite films. Moreover, the soil burial biodegradation results indicated that the biodegradability of the starch/PVA/glycerol/urea composite film strongly depended on the PVA proportion in the composite film matrix. The DSC results show that the higher the amount of PVA in the composite film, the less change of the melting enthalpy value. The crystalline region of PVA remains after biodegradation

Influence of Heating Temperature and Holding Time on Biochars Derived from Rubber Wood Sawdust via Slow Pyrolysis

Biochar samples were produced from rubber wood sawdust (RWSD), which is a by-product from sawmills, via slow pyrolysis. Biochar is a potential additive for agricultural soil as a soil amendment and for agronomics. The approach proposed in the current study considers the effects of heating temperature and holding time on the surface functional groups and morphologies of RWSD-derived biochars. The pyrolysis was performed in a vertical tube furnace heated at 5 °C/min from room temperature to maximum heating temperatures of 300 °C, 400 °C, 500 °C and 700 °C under nitrogen gas purging at a rate of 30 ml/min. Two sets of biochars were produced with holding times of (i) 1 h and (ii) 3 h. Proximate and ultimate analyses were performed on the raw RWSD using thermogravimetric analysis (TGA) and carbon–hydrogen–nitrogen (CHN) elemental analysis. The influence of heating temperature and holding time on biochar surface functional groups and porosities was investigated using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Boehm titration, pH alkalinity, Brunauer–Emmett–Teller (BET) surface area analysis, scanning electron microscopy (SEM) and SEM with energy-dispersive X-ray (SEM–EDX) spectrocopy. The FT-IR spectra indicated the presence of acidic functional groups, such as carboxylic, phenolic and lactonic groups, and these groups were quantified by Boehm titration. The number of acidic functional groups decreased as the heating temperature and holding time increased. The maximum amount of acidic functional groups was determined to be 1.9 mmol/g at 300 °C for a 1-h holding time compared to 1.3 mmol/g for a 3-h holding time and 1.0 mmol/g with a 1-h holding time at 700 °C. All of the biochars produced at heating temperatures above 400 °C were alkaline, and the pH value increased as the heating temperature and holding time increased. The biochar produced at 300 °C with a 1-h holding time had a pH of 6.72 and the sample produced with a 3-h holding time had a pH of 7.67. In addition, the sample produced when the temperature was increased to 700 °C with a 1-h holding time had a pH of 11.44. The BET surface area analysis reported maximum values of 5.49 m2/g, and the total pore volume was 0.0097 cm3/g at a heating temperature of 700 °C with a 3-h holding time. SEM micrographs clearly showed the development of well-defined pores in the biochars, and the SEM–EDX spectra indicated localised carbon and oxygen content in all the samples. The results indicated that biochars produced from RWSD are potentially beneficial as soil amendments. However, an extensive study of biochar sustainability is worth investigating