Comparative study of the effect of rice husk-based powders used as physical conditioners on sludge dewatering

The effects of rice husk flour (RHF), rice husk biochar (RHB), and rice husk-sludge cake biochar (RH-SCB, expresses sludge cake biochar deriving from a sludge that has been previously conditioned with rice husk) used as physical conditioners on sludge dewaterability were compared. The effects of characteristics of physical conditioners on sludge compressibility and zeta potential were analyzed. The optimal rice husk-based powder was RH-SCB, which presented the highest net sludge solid yield (YN, expresses the dry mass flow by filtration) at 20.39 kg/(m2 h) for 70% dry sludge (DS). Characterization analysis indicates that the hardness and surface Fe content of powders which could influence the compressibility coefficient of sludge cake and sludge zeta potential were the major factors influencing sludge dewaterability. The comparison of feasibility and economic analysis showed that adding RH-SCB improves the quality of the sludge filtrate and reduces the pollution potential of conditioned sludge (the ratio of secondary and primary (RSP) of Cu, Zn, Cd reduces from 43.05, 144.00, 7.25 to 7.89, 14.63, 4.27, respectively), and the costs of using RH-SCB were the lowest (at 88.4% lower than that of the raw sludge). Therefore, it is feasible to use RH-SCB to improve sludge dewaterability.

Determination of Moisture Sorption Isotherms of Rice and Husk Flour Composites

HighlightsMoisture sorption isotherms of rice and husk flour composites were determined.Adsorption isotherms were best modeled by the Chung-Pfost and Oswin equations.Desorption isotherms were best modeled by the Polynomial and Chung-Pfost equations.The Modified Oswin model was the best for both adsorption and desorption.Abstract. Empirical models describing isotherms specifically for adsorption and desorption have not been described for rough rice and husk flour composites. Such models are vital for process control and monitoring operations which use rice husk and rice flours or their mixtures for food or material processing. The current study was undertaken to determine the moisture sorption isotherms of rice husk flour, rough rice flour and their mixtures subjected to different temperature levels. Effects of rice husk flour to rough rice flour ratio of 0:1 (0.0%), 1:49 (2.0%), 1:16 (5.9%), and 1:0 g/g (100.0%) on rough rice moisture isotherms at temperature levels of 20°C, 40°C, and 60°C were investigated. The dynamic dewpoint isotherm technique (DDI) was used to generate accurate isotherms. Several empirical models were tested to fit the experimental EMC data. All the isotherms showed typical sigmoidal type 2 shapes. The equilibrium moisture content (EMC) over equilibrium relative humidity (water activity) ranging from 10% to 95% showed temperature dependence. Hysteresis was evident for all samples, with a decreasing level at a higher temperature. Rice husk flour to rough rice flour ratio, as a factor, showed a significant effect on the EMC of rough rice. The EMC decreased with an increase in rice husk flour levels. Chung-Pfost and Oswin were the two best models for describing adsorption isotherm, and Polynomial and Chung-Pfost were the best models for fitting the desorption isotherm. Modified Oswin model was the best model amongst the two-variable models for describing both adsorption and desorption isotherms. Keywords: Empirical models, Equilibrium moisture content, Rice husk flour, Rough rice flour, Sorption isotherms.

Reactive Melt Mixing of Poly(3-Hydroxybutyrate)/Rice Husk Flour Composites with Purified Biosustainably Produced Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)

Novel green composites based on commercial poly(3-hydroxybutyrate) (PHB) filled with 10 wt % rice husk flour (RHF) were melt-compounded in a mini-mixer unit using triglycidyl isocyanurate (TGIC) as compatibilizer and dicumyl peroxide (DCP) as initiator. Purified poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) produced by mixed bacterial cultures derived from fruit pulp waste was then incorporated into the green composite in contents in the 5–50 wt % range. Films for testing were obtained thereafter by thermo-compression and characterized. Results showed that the incorporation of up to 20 wt % of biowaste derived PHBV yielded green composite films with a high contact transparency, relatively low crystallinity, high thermal stability, improved mechanical ductility, and medium barrier performance to water vapor and aroma. This study puts forth the potential use of purified biosustainably produced PHBV as a cost-effective additive to develop more affordable and waste valorized food packaging articles.

Dynamic Mechanical Thermal Analysis of Wood Polymer Composite Endurance to Prolonged Ultra Violet Irradiation Exposure

This study was constructed to examine the viscoelastic properties and the microstructure of wood-plastic composites (WPCs) before and after being subjected to UV irradiation. The pellet of the wood polymer composites consists of polypropylene as the matrix and rice-husk flour as the reinforcing filler. The samples were UV irradiated from 5000 hours to 20,000 hours with the increment of 5000 hours to study the effect of weathering on the viscoelastic properties of the WPCs. The microstructures of the surface of the samples were examined using Optical Microscopy (OM). The mechanical properties of WPCs through dynamic mechanical analysis test were assessed for both polyvinyl chloride (PVC) and polypropylene (PP) samples. The value of storage modulus (E’) decreases when been exposed in the ultra violet irradiation, in both glassy and rubbery states. Moreover, the density of the WPC samples is closed to light weight and result is comparable. As for morphological properties test, the surface of cracked, voids appeared at the surface of the WPC samples of both PVC and PP interface and the density of composite decreased.

Effect of Silane Treatment Methods on Physical Properties of Rice Husk Flour/Natural Rubber Composites

In this study, the effect of silane treatment methods on cure characteristics and mechanical, dynamic mechanical, and morphological properties of rice husk flour (RHF)/natural rubber (NR) composites was investigated. The RHF surface was pretreated with alkali solution and then treated with bis(triethoxysilylpropyl) tetrasulfide (TESPT) solution using the unwashing silane treatment method and washing silane treatment method. The expected difference between these two methods was the silane layers presented on the RHF surface. Unwashed TESPT-treated RHF (UW-ST) and washed TESPT-treated RHF (W-ST) were incorporated into NR to prepare RHF/NR composites. The TESPT molecules deposited on UW-ST and W-ST surfaces were confirmed by the additional peaks appeared in the FTIR spectra of UW-ST and W-ST. In addition, the decrement of decomposition temperatures and the changes in the residue amounts of UW-ST and W-ST proved the removal of the physisorbed silane layers after washing. The presence of TESPT molecules on the RHF surface enhanced compatibility and adhesion between RHF and NR matrix. This was confirmed by SEM micrographs of both UW-ST/NR and W-ST/NR composites. This result was also supported by the improvement of the mechanical and the dynamic mechanical properties of these two composites. According to mechanical properties of the NR composites, the washing silane treatment method was more effective than the unwashing silane treatment method for compatibility improvement between RHF and NR. The modulus, tensile strength, and tear strength of W-ST/NR composites can be enhanced without deterioration of their elongation at break.