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An agricultural waste-based source of energy in the form of briquettes from rice husk has emerged as an alternative energy source. However, rice husk-based briquette has a low bulk density and moisture content, resulting in low durability. This study investigated the effect of initial moisture contents of 12%, 14%, and 16% of rice husk-based briquettes blended with 10 wt% of kraft lignin on their chemical and physical characteristics. The briquetting was done using a hand push manual die compressor. The briquette properties were evaluated by performing chemical (ultimate and proximate analysis, thermogravimetric analysis), physical (density, durability, compressive strength, and surface morphology) analyses. The durability values of all briquette samples were above 95%, meeting the standard with good compressive strength, surface morphology, and acceptable density range. The briquette made from the blend with 14% moisture content showed the highest calorific value of 17.688 MJ kg−1, thanks to its desirable morphology and good porosity range, which facilitates the transport of air for combustion. Overall, this study proved the approach of enhancing the quality of briquettes from rice husk by controlling the moisture content. [ABSTRACT FROM AUTHOR]

Membrane fouling is a major drawback of almost all pressure-driven membrane processes that limit their widespread application. This study compares the biological and the hydraulic performances of polyvinylidene fluoride (PVDF) and polysulfone (PSF) membranes when used as external filtration for polishing of a rotating biological contactor (RBC) effluent and as an integrated part in a membrane rotating biological contactor (MRBC). MRBC is an upgrade of the conventional RBC, in which the disk rotations are used not only to provide biological aeration but also as an inherent mechanism for membrane fouling control. Results showed that high biological performances were achieved irrespective of the membrane materials. The steady-state permeabilities of the membranes in MRBC are higher than external filtration by 92.4% and 19.7% for the PVDF and PSF membrane respectively. In the MRBC, smaller membrane-to-disk gaps and high disk rotational speed improve permeability for both membranes reaching the values of 297 and 173 L/(m2 h bar) for PVDF and PSF membranes, respectively. Full-scale energy consumption projection results show that the MRBC consumes only one-fourth of the energy of a referenced membrane bioreactor. The PVDF membrane outperforms PSF membrane thanks to the effective fouling control that maximize the throughput of a lower intrinsic resistance of the PVDF membrane. It implies that apart from membrane material, other operational parameters can still be optimized to further enhance the MRBC performance. ga1 • This study explores the effect of membrane properties in MRBC. • Operation inside of bioreactor enhance permeability irrespective of membrane. • Combination of disk rotation and small gap reaches permeability of 297 L/(m2 h bar). • MRBC with high throughput membrane has a very low energy input of 0.18 kWh/m3. [ABSTRACT FROM AUTHOR]

Various types of activated carbon nanofibers' (ACNFs) composites have been extensively studied and reported recently due to their extraordinary properties and applications. This study reports the fabrication and assessments of ACNFs incorporated with graphene-based materials, known as gACNFs, via simple electrospinning and subsequent physical activation process. TGA analysis proved graphene-derived rice husk ashes (GRHA)/ACNFs possess twice the carbon yield and thermally stable properties compared to other samples. Raman spectra, XRD, and FTIR analyses explained the chemical structures in all resultant gACNFs samples. The SEM and EDX results revealed the average fiber diameters of the gACNFs, ranging from 250 to 400 nm, and the successful incorporation of both GRHA and reduced graphene oxide (rGO) into the ACNFs' structures. The results revealed that ACNFs incorporated with GRHA possesses the highest specific surface area (SSA), of 384 m2/g, with high micropore volume, of 0.1580 cm3/g, which is up to 88% of the total pore volume. The GRHA/ACNF was found to be a better adsorbent for CH4 compared to pristine ACNFs and reduced graphene oxide (rGO/ACNF) as it showed sorption up to 66.40 mmol/g at 25 °C and 12 bar. The sorption capacity of the GRHA/ACNF was impressively higher than earlier reported studies on ACNFs and ACNF composites. Interestingly, the CH4 adsorption of all ACNF samples obeyed the pseudo-second-order kinetic model at low pressure (4 bar), indicating the chemisorption behaviors. However, it obeyed the pseudo-first order at higher pressures (8 and 12 bar), indicating the physisorption behaviors. These results correspond to the textural properties that describe that the high adsorption capacity of CH4 at high pressure is mainly dependent upon the specific surface area (SSA), pore size distribution, and the suitable range of pore size. [ABSTRACT FROM AUTHOR]

Polydopamine has been widely used as an additive to enhance membrane fouling resistance. This study reports the effects of two-step dopamine-to-polydopamine modification on the permeation, antifouling, and potential anti-UV properties of polyethersulfone (PES)-based ultrafiltration membranes. The modification was performed through a two-step mechanism: adding the dopamine additive followed by immersion into Tris-HCl solution to allow polymerization of dopamine into polydopamine (PDA). The results reveal that the step of treatment, the concentration of dopamine in the first step, and the duration of dipping in the Tris solution in the second step affect the properties of the resulting membranes. Higher dopamine loadings improve the pure water flux (PWF) by more than threefold (15 vs. 50 L/m2·h). The extended dipping period in the Tris alkaline buffer leads to an overgrowth of the PDA layer that partly covers the surface pores which lowers the PWF. The presence of dopamine or polydopamine enhances the hydrophilicity due to the enrichment of hydrophilic catechol moieties which leads to better anti-fouling. Moreover, the polydopamine film also improves the membrane resistance to UV irradiation by minimizing photodegradation's occurrence. [ABSTRACT FROM AUTHOR]

The bottleneck of conventional polymeric membranes applied in industry has a tradeoff between permeability and selectivity that deters its widespread expansion. This can be circumvented through a hybrid membrane that utilizes the advantages of inorganic and polymer materials to improve the gas separation performance. The approach can be further enhanced through the incorporation of amine-impregnated fillers that has the potential to minimize defects while simultaneously enhancing gas affinity. An innovative combination between impregnated Linde T with different numbers of amine-functional groups (i.e., monoamine, diamine, and triamine) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA)-derived polyimide has been elucidated to explore its potential in CO2/CH4 separation. Detailed physical properties (i.e., free volume and glass transition temperature) and gas transport behavior (i.e., solubility, permeability, and diffusivity) of the fabricated membranes have been examined to unveil the effect of different numbers of amine-functional groups in Linde T fillers. It was found that a hybrid membrane impregnated with Linde T using a diamine functional group demonstrated the highest improvement compared to a pristine polyimide with 3.75- and 1.75-fold enhancements in CO2/CH4 selectivities and CO2 permeability, respectively, which successfully lies on the 2008 Robeson's upper bound. The novel coupling of diamine-impregnated Linde T and 6FDA-derived polyimide is a promising candidate for application in large-scale CO2 removal processes. [ABSTRACT FROM AUTHOR]

Unprocessed biomass has low energy density and high transportation cost. The energy generated through biomass can be enhanced by the pelletizing technique. In order to evaluate the energy requirement for the pelletizing of agricultural biomass, three different particle sizes (150–300, 300–425, and 425–600 µm) of reed canary grass (RCG), timothy hay (TH), and switchgrass (SW) were selected in the present work. Furthermore, two woody biomasses (spruce and pine) were also considered under similar experimental conditions for comparison purposes. An Instron machine attached to an in-house built pelletizer unit was employed to produce a single pellet. The energy demand for compacting ground biomass (spruce) with a particle size of 150 µm was lower (2.07 kJ) than those required for particle sizes of 300 µm (2.24 kJ) and 425 µm (2.43 kJ). The energy required for compacting ground reed canary grass, timothy hay, and switchgrass was lower (1.61, 1.97, and 1.68 kJ, respectively) than that required for spruce (2.36 kJ) and pine (2.35 kJ), evaluated at a 159-MPa load and at temperature of about 80 °C. The energy demand for blended biomass was around 2 kJ with the pellet quality approaching that of the pellets made from woody biomass. Overall, blending helped to improve the quality of pellets and lower the compaction energy requirements. [ABSTRACT FROM AUTHOR]