Strategies for strengthening toughened poly(lactic acid) blend via natural reinforcement with enhanced biodegradability: A review.

The growing popularity of poly(lactic acid) (PLA) can be attributed to its favorable attributes, such as excellent compostability and robust mechanical properties. Two notable limitations of PLA are its high brittleness and slow biodegradation rate. Both of blending and copolymerization strategies work well to improve PLA's toughness while sacrificing the good tensile strength and modulus properties of PLA. One of the most effective and economical approaches to address this challenge is to incorporate natural reinforcing agents into the toughened PLA system, thereby simultaneously promoting the biodegradation rate of PLA. Nevertheless, the enhancement of tensile strength and modulus is accompanied by a notable decrease in elongation. Therefore, this review provides comprehensive information on the literature works related to the tensile strength, modulus, elongation at break and impact strength of the toughened PLA and its natural fiber reinforced composites. The impact of natural reinforcing agent on the tensile fracture mechanism as well as the synergistic effect on strengthening and toughening performance will be discussed. This review also focuses on the factors boosting the biodegradability of toughened PLA blend by using natural reinforcing fiber. Review presents potential future insights into the development of biodegradable and balanced strengthened-toughened PLA based advanced materials.

Methylene Blue Dye Photocatalytic Degradation over Synthesised Fe3O4/AC/TiO2 Nano-Catalyst: Degradation and Reusability Studies.

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.

Application of Efficient Magnetic Particles and Activated Carbon for Dye Removal from Wastewater.

Since the turn of the 21st century, water pollution has been a major issue, and most of the pollution is generated by dyes. Adsorption is one of the most commonly used dye-removal methods from aqueous solution. Magnetic-particle integration in the water-treatment industry is gaining considerable attention because of its outstanding physical and chemical properties. Magnetic-particle adsorption technology shows promising and effective outcomes for wastewater treatment owing to the presence of magnetic material in the adsorbents that can facilitate separation through the application of an external magnetic field. Meanwhile, the introduction of activated carbon (AC) derived from various materials into a magnetic material can lead to efficient organic-dye removal. Therefore, this combination can provide an economical, efficient, and environmentally friendly water-purification process. Although activated carbon from low-cost and abundant materials has considerable potential in the water-treatment industry, the widespread applications of adsorption technology are limited by adsorbent recovery and separation after treatment. This work specifically and comprehensively describes the use of a combination of a magnetic material and an activated carbon material for dye adsorption in wastewater treatment. The literature survey in this mini-review provides evidence of the potential use of these magnetic adsorbents, as well as their magnetic separation and recovery. Future directions and challenges of magnetic activated carbon in wastewater treatment are also discussed in this paper.

An improved physico-mechanical performance of macropores membrane made from synthesized cellulose carbamate.

Under hydrothermal condition, kenaf cellulose carbamate (KCC) was synthesized using urea and kenaf core pulp (KCP) without catalyst and organic solvent. The KCC was prepared with various urea/KCP ratios (2:1, to 4:1 and 6:1) with the aid of autoclave and oil bath, whereas the regenerated KCC membranes were formed via solution casting method. The physical and thermal properties of KCC were studied. The urea/KCP ratio used in preparing KCC corresponds with the nitrogen percentage obtained in KCC. The formation of the regenerated KCC membranes could be confirmed by the existence of cellulose II through X-ray diffraction (XRD) study. As examined by Field emission scanning electron microscope (FESEM), the regenerated KCC membranes possessed the greater pore size structures at higher urea concentration. Mechanical results showed the tensile strength and modulus of regenerated KCC membranes have improved up to 43.4% and 76.9%, respectively, as compared to native KCP membrane. It can be concluded from the findings that synthesizing KCC and its membranes with improved mechanical properties has broad prospects for potential industrial applications such as biomembranes and packaging materials.

Interconnected macropores cryogel with nano-thin crosslinked network regenerated cellulose.

Dissolved oil palm empty fruit bunch cellulose (EFBC) and sodium carboxymethylcellulose (NaCMC) were chemically crosslinked with epichlorohydrin (ECH) to generate designated hydrogel. After swelling process in distilled water, the swollen hydrogel was frozen and freeze-dried to form cryogel. The swelling phenomenon of hydrogel during the absorption process gave substantial effects on thinning of crosslinked network wall, pore size and volume, steadiness of cryogel skeletal structure, and re-swelling of cryogel. The swelling effects on hydrogel were confirmed via microscopic study using variable pressure scanning electron microscope (VPSEM). From the retrieved VPSEM images, nano-thin crosslinked network wall of 24.31 ± 1.97 nm and interconnected pores were observed. As a result, the amount of water, the swelling degree, and the freeze-drying process indirectly affected the VPSEM images that indicated pore size and volume, formation of interconnected pores, and re-swelling of cryogel. This study determined the intertwined factors that affected both hydrogel and cryogel properties by investigating the swelling phenomenon and its ensuing effects.

Superabsorbent hydrogel from oil palm empty fruit bunch cellulose and sodium carboxymethylcellulose.

A green regenerated superabsorbent hydrogel was fabricated with mixtures of dissolved oil palm empty fruit bunch (EFB) cellulose and sodium carboxymethylcellulose (NaCMC) in NaOH/urea system. The formation of hydrogel was aided with epichlorohydrin (ECH) as a crosslinker. The resultant regenerated hydrogel was able to swell >80,000% depending on the NaCMC concentrations. The hydrogel absorbed water rapidly upon exposure to water up to 48 h and gradually declined after 72 h. The crosslinked of covalent bond of COC between dissolved EFB cellulose (EFBC) with NaCMC was confirmed with Attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy. Crystallinity and thermal stability of the hydrogel samples were depended on the concentrations of NaCMC, crosslinking, and swelling process. The strength and stability of crosslinked network was studied by examining the gel fraction of hydrogel. This study explored the swelling ability and probable influenced factors towards physical and chemical properties of hydrogel.

Chemically crosslinked hydrogel and its driving force towards superabsorbent behaviour.

Dissolved oil palm empty fruit bunch (EFB) cellulose in NaOH/urea solvent was mixed with sodium carboxymethylcellulose (NaCMC) to form a green regenerated superabsorbent hydrogel. The effect of concentration of epichlorohydrin (ECH) as the crosslinker on the formation, physical, and chemical properties of hydrogel was studied. Rapid formation and higher gel content of hydrogel were observed at 10% concentration of ECH. The superabsorbent hydrogel was successfully fabricated in this study with the swelling ability >100,000%. Hydrogel with higher concentration of ECH showed opposite trend by having higher superabsorbent property than that of lower concentration. The covalent bond of COC was observed with Attenuated total reflectance fourier transform infrared (ATR-FT-IR) spectroscopy to confirm the occurrence of crosslinking. The physical and chemical properties of hydrogel were affected by swelling phenomenon. Hydrogel with higher degree of swelling exhibited lower moisture retention and higher transparency. Moreover, the weight of the superabsorbent hydrogel increased with the decrement of pH value of external media (distilled water). This study provided substantial information on the effect of different percentage of ECH as crosslinker on hydrogel basic properties. Furthermore, this study affords correlation of many essential driving forces that affected hydrogel superabsorbent property.

Enhanced mechanical properties of hydrothermal carbamated cellulose nanocomposite film reinforced with graphene oxide.

Cellulose carbamate (CC) was synthesized via hydrothermal process and mixed with graphene oxide (GO) to form a homogeneous cellulose matrix nanocomposite films. The properties of CC/GO nanocomposite films fabricated using simple solution-mixing method with different GO loadings were studied. Transmission electron microscope analysis showed the exfoliation of self-synthesized GO nanosheets within the CC matrix. X-ray diffraction results confirmed the crystalline structure of CC/GO films as the CC/GO mass ratio increased from 100/0 to 100/4. The mechanical properties of CC/GO film were significantly improved as compared to neat CC film. From thermogravimetric analysis result, the introduction of GO enhanced the thermal stability and carbon yields. The 3D homogeneous porous structures of the CC/GO films were observed under Field emission scanning electron microscope. These improvements in nanocomposite film properties could be confirmed by Fourier transform infrared spectroscopy due to the strong and good interactions between CC and GO.

Highly porous regenerated cellulose hydrogel and aerogel prepared from hydrothermal synthesized cellulose carbamate.

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.

Synthesis of kenaf cellulose carbamate and its smart electric stimuli-response.

Cellulose carbamate (CC) was produced from kenaf core pulp (KCP) via a microwave reactor-assisted method. The formation of CC was confirmed by Fourier transform infrared spectroscopy and nitrogen content analysis. The degree of substitution, zeta potential and size distribution of CC were also determined. The CC was characterized with scanning electron microscopy, X-ray diffraction and thermogravimetry analysis. The CC particles were then dispersed in silicone oil to prepare CC-based anhydrous electric stimuli-responsive electrorheological (ER) fluids. Rhelogical measurement was carried out using rotational rheometer with a high voltage generator in both steady and oscillatory shear modes to examine the effect of electric field strength on the ER characteristics. The results showed that the increase in electric field strength has enhanced the ER properties of CC-based ER fluid due to the chain formation induced by electric polarization among the particles.

Effect of acid hydrolysis on regenerated kenaf core membrane produced using aqueous alkaline-urea systems.

Bleached kenaf core pulps (BKC) were hydrolyzed in H2SO4 (0.5M) at different time (0min to 90min) at room temperature. After the hydrolysis process, the viscosity average molecular weight (Mŋ) for BKC sample has reduced from 14.5×10(4) to 2.55×10(4). The hydrolyzed BKC was then dissolved in NaOH:urea:water and in LiOH:urea:water mixed solvent at the ratio of 7:12:81 and 4.6:15:80.4, respectively. The increased in hydrolysis time has decreased Mŋ of cellulose leading to easy dissolution process. Higher porosity and transparency with lower crystallinity index (CrI) of regenerated membrane produced can be achieved as the Mŋ reduced. The properties of membrane were observed through FESEM, UV-vis spectrophotometer and XRD. This study has proven that acid hydrolysis has reduced the Mŋ of cellulose, thus, enhanced the properties of regenerated membrane produced with assisted by alkaline/urea system.

Effect of hydrothermal pretreatment on solubility and formation of kenaf cellulose membrane and hydrogel.

The hydrothermal pretreatment on kenaf core pulp (KCP) was carried out using an autoclave heated in a oil bath at 140°C for 0.5/1/3/5h. The hydrothermal pretreated kenaf (HPK) was dissolved in a LiOH/urea aqueous solution and subsequently used to produce cellulose membrane and hydrogel. The effects of hydrothermal pretreatment time on solubility, viscosity, crystallinity and morphology of the cellulose membrane and hydrogel were investigated. The hydrothermal pretreatment leads to higher cellulose solubility and higher viscosity of the cellulose solution. The formation of cellulose II and crystallinity index of the cellulose membrane and hydrogel were examined by X-ray diffraction (XRD). The pore size of the cellulose membrane and hydrogel displayed an upward trend with respect to the hydrothermal pretreatment period observed under a field emission scanning electron microscope (FESEM). This finding provides an efficient procedure to improve the solubility, viscosity and properties of regenerated cellulose products.

Synthesis of kenaf cellulose carbamate using microwave irradiation for preparation of cellulose membrane.

Cellulose carbamate (CCs) was produced from kenaf core pulp (KCP) using microwave reactor-assisted method. The effects of urea concentration and reaction time on the formation of nitrogen content in CCs were investigated. The CCs' solubility in LiOH/urea system was determined and its membranes were characterized. As the urea content and reaction time increased, the nitrogen content form in CCs increased which enhanced the CCs' solubility. The formation of CCs was confirmed by Fourier transform infrared spectroscopy (FT-IR) and nitrogen content analysis. The CCs' morphology was examined using Scanning electron microscopy (SEM). The cellulose II and crystallinity index of the membranes were confirmed by X-ray diffraction (XRD). The pore size of the membrane displayed upward trend with respect to the urea content observed under Field emission scanning electron microscope (FESEM). This investigation provides a simple and efficient procedure of CCs determination which is useful in producing environmental friendly regenerated CCs.