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Sustainable agriculture aims to meet the needs of the people in the present as well as in the future. The inadequate supply of vegetables raises dependency on imports for the growing population. To reduce import dependency, effective approaches in urban farming are emerging. One of the approaches is the application of hydrogel as a growth substrate in urban farming. This comparative study focuses on the characterisation of cellulose-based hydrogel sourced from cotton and its application as a seed germination medium in comparison to soil and perlite. Hydrogel is prepared by using cotton linter, sodium hydroxide, urea and epichlorohydrin as the cross-linker. Analyses to characterize soil, perlite and hydrogel (cryogel) were performed through gel fraction, field emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD), and thermogravimetric analysis (TGA). Seedling growth performance for four plant species (Ipomoea aquatica, Brassica juncea, Lactuca sativa, Solanum lycopersicum) was recorded after 15 days on each growth medium. Hydrogel crosslinking strength was at 92.49% based on the gel fraction analysis and the swelling of the hydrogel reached 65.00% in ten days. The FESEM analysis shows the hydrogel has a porous structure. Growth of Ipomoea aquatica in hydrogel medium was better than in soil. Hydrogel medium has room for further improvement through future research and development in urban farming. [ABSTRACT FROM AUTHOR]

High-fiber loading green composites were prepared from recycled high-density polyethylene (rHDPE)/recycled polyethylene terephthalate (rPET) blend matrix and rice husk (RH) as filler (from 40 wt% up to 80 wt%) via corotating twin-screw extruder and compression molding. The water absorption (WA) upon immersion in sea water, mechanical behavior, and combustion enthalpy of green composites were examined. The WA mechanisms obeyed the Fickian diffusion. The computed diffusion coefficient (D), thermodynamic solubility (S), permeability (P), and orthotropic swelling were generally increased as a function of RH filler. The increment of tensile strength and modulus of composites were maximized up to 16% and 121%, respectively, which was achieved at 70 wt% RH filler. The theoretical prediction of tensile strength and Young's modulus from micromechanical models for random oriented RH fiber/blend composites were compared with the experimental results. As the RH weight fraction increased, the combustion enthalpy decreased (by approximately 30–48%) and thereby the enhancing the fire retardancy of green composite. [ABSTRACT FROM AUTHOR]

Cellulose cryogels crosslinked with epichlorohydrin (ECH) were successfully developed from kenaf core biomass via green urea/alkaline solvent system. The effect of ECH concentration (from 3 to 9 wt%) on the pore structure, density, morphology, thermal stability, mechanical properties, water absorption performance and acoustic insulation of cellulose cryogels were studied. It was found that the introduction of ECH affected the porosity and pore volume as well as density and water absorption of cryogels. The increase percentage of ECH has delayed the thermal decomposition of the cellulose cryogels thereby improving their thermal stability. Moreover, the compress stress and the sound absorption coefficient of the cellulose cryogels were enhanced significantly by about 50% and 27%, respectively. This work provides a facile approach to produce cost-effective biomass-derived cellulose cryogels with improved mechanical and thermal stability properties as well as acoustic insulation for preliminary studies of industrial applications. [ABSTRACT FROM AUTHOR]

Abstract: By combining the waste of oil palm empty fruit bunch (EFB) and graphene oxide (GO), a GO/cellulose aerogel bio-nanocomposite was produced via a simple mixing method. The thermal properties of this nanocomposite were examined using thermogravimetric analysis (TGA), and the GO/cellulose aerogel bio-nanocomposite exhibited good thermal stability indicated by a delay in the degradation of the nanocomposite even at low GO incorporation. Experimental and modeled TGA curves were compared. The morphology of the GO/cellulose aerogel composite was observed under field emission scanning electron microscope. In GO/cellulose aerogel composite with 4 wt% GO, the pore volume and porosity decreased by more than 50% compared to aerogel without GO, and the density of the 4 wt% GO/cellulose aerogel composite showed a onefold increase compared with the pure cellulose aerogel. The degree of swelling and equilibrium-swelling ratio of regenerated GO/cellulose hydrogel and aerogel decreased with the higher GO concentration. The phase transition from EFB to regenerated GO/cellulose aerogel composite was evaluated using X-ray diffraction. This study has provided a simple pathway to produce environmentally friendly biocomposite materials.Graphical abstract: [ABSTRACT FROM AUTHOR]

High cellulose solubility is an essential to successful production of regenerated cellulose, from which hydrogels can be produced. Additionally, some pretreatment usually facilitates cellulose solubility. Bleached cellulose pulp from kenaf core (BK), consisting of lignin (0.3%), hemicellulose (5.2%) and ash (0%), was treated with an electron beam irradiation (EBI) at 10, 30, 50 and 70 kGy. The BK and irradiated bleached cellulose pulp (IK) were then dissolved in either sodium hydroxide/urea or lithium hydroxide/urea solvents which subsequently crosslinked with epichlorohydrin (ECH) solution to stabilize the formation of regenerated cellulose hydrogels. The amount of α-cellulose component in IK samples decreased as much as 38% and caused the viscosity average molecular weight (Mv) and degree of polymerization of IK samples to be reduced significantly by 84 and 87%, respectively. This resulted in an increase in cellulose solubility (up to 30%) for the IK samples in both solvent systems. However, this treatment resulted in a reduction in the overall cellulose fibre strength. X-ray diffraction of the hydrogels showed a transformation from cellulose I to amorphous cellulose. These hydrogels exhibited a higher degree of swelling, transparency and porosity compared to hydrogels prepared from non-irradiated pulp. [ABSTRACT FROM AUTHOR]

Green composite materials were made from agricultural and plastic wastes which were rice husk (RH), recycled high‐density polyethylene (rHDPE), and recycled polyethylene terephthalate (rPET), by twin‐screw extrusion and hot/cold pressing molding. The dimensional stability, orthotropic swelling, and mechanical performance of the green composites were determined as a function of bio‐filler concentration for neat (uncompatibilized) and compatbilized rHDPE/rPET blend based composites. Water absorption and swelling results showed a linear increase with the RH concentration. The highest swelling occurred in the thickness of the composites, followed by the width and length, respectively. Water absorption and dimensional instability of compatibilized recycled polymer blend (rPB)‐based composites were lower than those of neat rPB‐based composites. As RH concentration increased, the flexural properties increased significantly. The optimum tensile strength and modulus were achieved at 70 wt% RH. It is interesting to note that compatibilization of polymer blend matrix had further increased the strength and elongation properties of composites. POLYM. COMPOS., 39:2695–2704, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Here, a stable derivative of cellulose, called cellulose carbamate (CC), was produced from Kenaf (Hibiscus cannabinus) core pulp (KCP) and urea with the aid of a hydrothermal method. Further investigation was carried out for the amount of nitrogen yielded in CC as different urea concentrations were applied to react with cellulose. The effect of nitrogen concentration of CC on its solubility in a urea-alkaline system was also studied. Regenerated cellulose products (hydrogels and aerogels) were fabricated through the rapid dissolution of CC in a urea-alkaline system. The morphology of the regenerated cellulose products was viewed under Field emission scanning electron microscope (FESEM). The transformation of allomorphs in regenerated cellulose products was examined by X-ray diffraction (XRD). The transparency of regenerated cellulose products was determined by Ultraviolet–visible (UV–Vis) spectrophotometer. The degree of swelling (DS) of regenerated cellulose products was also evaluated. This investigation provides a simple and efficient procedure of CC determination which is useful in producing regenerated CC products. [ABSTRACT FROM AUTHOR]

Cellulose hydrogel was produced from pretreated oil palm empty fruit bunch fiber (EFB) that went through acid hydrolysis and thermal hydrolysis. The pretreated EFB was dissolved in LiOH/urea aqueous solution using the rapid dissolution method and was subjected to a crosslinking process with the aid of epichlorohydrin to form hydrogel. The effects of both hydrolyses' time on average molecular weight (Mŋ), solubility, and properties of EFB hydrogels were evaluated. Both hydrolyses led to lower Mŋ, lower crystallinity index (CrI) and hence, resulted in higher cellulose solubility. X-ray diffraction (XRD) characterization revealed the CrI and transition of crystalline structure of EFB from cellulose I to II. The effects of hydrolysis time on the transparency, degree of swelling (DS), and morphology of the regenerated cellulose hydrogel were also investigated using an ultraviolet-visible (UV-Vis) spectrophotometer and a Field emission scanning electron microscope (FESEM), respectively. These findings provide an efficient method to improve the solubility and properties of regenerated cellulose products. [ABSTRACT FROM AUTHOR]

Cellulose carbamate (CC) prepared using microwave irradiation was reinforced with graphene oxide (GO) to fabricate homogeneous and highly ordered CC-GO membranes using a simple solution-mixing method. The effect of GO content on the properties of the membranes was investigated. Atomic force microscope and transmission electron microscope images indicated that the self-synthesized GO nanosheets exhibited exfoliated layers within the CC. X-ray diffraction results confirmed the crystalline structure of cellulose I and cellulose II in the CC pulp and CC-GO membranes, respectively. Increasing the GO content from 0 to 4 wt% resulted in a slight decrement in the crystallinity index. The membrane containing 4 wt% GO possessed a tensile modulus and strength higher by approximately 525 and 93 %, respectively, compared to the neat CC. Thermogravimetric analysis proved that the GO promoted higher thermal stability and carbon yields. The 3D homogeneous porous structures of the CC-GO membranes were viewed under a field emission scanning electron microscope. These improvements in the membrane properties were confirmed by Fourier transform infrared spectroscopy and are attributed to the strong and effective interactions between CC and GO. [ABSTRACT FROM AUTHOR]

ABSTRACT Nanocomposites based on recycled high density polyethylene (rHDPE), recycled polyethylene terephthalate (rPET), and organoclay (C10A) were made using twin screw extruder followed by hot pressing. The independent effects of polymer/clay compatibility, preparation method, extrusion parameters, and clay loadings were investigated. Ethylene-glycidyl methacrylate could effectively improve the compatibilization of immiscible rHDPE/rPET blend with clay, which confirmed by the good polymers-clay adherence and domain size reduction obtained in scanning electron microscopy images. Although intercalated structures were observed in the composites made by one-step compounding, in the composites prepared by two-step extrusion method, enhanced dispersion of clay in polymer blend was found from X-ray diffraction results. Higher extrusion temperature and intermediate speed of rotation (90 rpm) appeared to increase the mechanical properties due to improvement of nanofiller dispersion in matrix. Results showed that the stiffness increased whereas tensile and impact strength decreased with clay content. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42287. [ABSTRACT FROM AUTHOR]

In this study, activated carbon (AC) from coconut shell, as a widely available agricultural waste, was synthesised in a simple one-step procedure and used to produce a magnetic Fe3O4/AC/TiO2 nano-catalyst for the degradation of methylene blue (MB) dye under UV light. Scanning electron microscopy revealed that TiO2 nanoparticles, with an average particle size of 45 to 62 nm, covered the surface of the AC porous structure without a reunion of its structure, which according to the TGA results enhanced the stability of the photocatalyst at high temperatures. The photocatalytic activities of synthesised AC, commercial TiO2, Fe3O4/AC, and Fe3O4/AC/TiO2 were compared, with Fe3O4/AC/TiO2 (1:2) exhibiting the highest catalytic activity (98%). Furthermore, evaluation of the recovery and reusability of the photocatalysts after treatment revealed that seven treatment cycles were possible without a significant reduction in the removal efficiency. [ABSTRACT FROM AUTHOR]