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This study develops a green method to fabricate pH/magnetic sensitive hydrogels based on pineapple peel carboxymethyl cellulose (PCMC), regenerated nanocellulose (rPPNc), and polyvinyl alcohol (PVA), accompanied by in situ incorporation of Fe 3 O 4 . The rPPNc was obtained through a two-stage method involving ionic liquid swelling followed by dilute sulfuric acid hydrolysis. The SEM images revealed the porous structure of the hydrogels. The hydrogels showed a magnetic responsive behavior due to incorporation of Fe 3 O 4 , and an enhanced thermal stability at high temperature due to incorporations of rPPNc and Fe 3 O 4 . The hydrogels displayed a pH-dependent swelling behavior and swelled more due to incorporation of rPPNc. In addition, rPPNc enhanced the naringin loading and entrapment efficiency of the hydrogels, showing an optimum value at 2% addition. The naringin can be gradually released from the hydrogels, which followed Fickian diffusion model. In summary, this work provided a relatively green approach for producing nanocellulose. The prepared hydrogels can be served as promising candidate materials for drug delivery system due to the characteristics of biocompatibility, pH and magnetic sensitivity., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In this study, the oxidized cellulose nanofibrils from pineapple peel (PP-TOCNF) were prepared by TEMPO-mediated oxidation followed by ball milling. The influence of oxidation degree on the structure and properties of PP-TOCNF were investigated, including Fourier transform infrared spectroscopy , X-ray diffraction, atomic force microscope (AFM), X-ray photoelectron spectroscopy and thermogravimetry, as well as the potential application in aerogels. The results suggested that TEMPO oxidation facilitated the dispersion of PP-TOCNF due to the strong electrostatic repulsion between –COO− groups. Regulating oxidation degree by varying NaClO concentration could effectively adjust the –COO− content (0.167–0.550 mmol/g), zeta potential (− 18 to − 34 mV) and rheological properties. The obtained PP-TOCNF showed a long fibrillar structure, whose average diameter and CrI values gradually decreased with the increase of oxidation degree. The PP-TOCNF-based aerogels exhibited a light weight, good porosity, water absorption, and mechanical properties, which also can be easily adjusted by oxidation degree of PP-TOCNF. Furthermore, TEMPO oxidation improved the stability and shape recovery ability of aerogels in water. [ABSTRACT FROM AUTHOR]

The pineapple peel cellulose(PPC) was used as raw material to dissolve in an alkali/urea solution with incorporation of bentonite, then further chemically cross-linked and in-situ embedded with magnetic Fe3O4 to form composite hydrogels. The structure and dye adsorption properties of hydrogels were studied. The results confirmed the successful intercalation of bentonite and Fe3O4 in the hydrogels. The bentonite effectively improved the cross-linked porous network structure, thermal stability and swelling properties of the hydrogel. The bentonite also enhanced the methylene blue adsorption performance of the hydrogels, showing an increased saturated adsorption capacity from 28. 09 mg/g to 55. 87 mg/g. The adsorption process conformed to the pseudo-second-order kinetic model and Langmuir model, belonging to chemical adsorption and monolayer adsorption. [ABSTRACT FROM AUTHOR]

Developing green and facile synthesis techniques for biomaterials has been widely advocated recently. In this study, we report a green and facile approach to prepare pineapple peel cellulose/magnetic diatomite hydrogels in an environmentally benign ionic liquid, 1-butyl-3-methylimidazolium chloride. The structure, swelling and methylene blue (MB) adsorption of the prepared hydrogels were investigated. The results of FTIR, XRD and SEM confirmed the successful embedment and dispersion of m-DE in hydrogel networks. The TG results indicated the improvement of thermal stability due to the presence of m-DE. The VSM results showed the superparamagnetic nature of the prepared hydrogels endowed by m-DE. Moreover, an appropriate addition of m-DE could enhance the swelling ability and MB adsorption capacity of the hydrogels. The MB adsorption process was fast (reaching equilibrium in 30 min) and fitted well with pseudo-second-order kinetic model and Langmuir isotherm model. The maximum adsorption capacity calculated from Langmuir isotherm model was 101.94 mg/g, obviously higher than the hydrogel prepared without m-DE addition (75.87 mg/g). Furthermore, the prepared hydrogels exhibited a good stability and reusability for MB adsorption. This work presents an alternative for the green construction and enhanced performance of cellulose-based hydrogels. [ABSTRACT FROM AUTHOR]

Biorefinery sector has become a serious dispute for cleaner and sustainable development in recent years. In the present study, pretreatment of pineapple peel waste was carried out in high pressure reactor using various pretreatment-enhancers. The type and concentration effect of each enhancer on hemicellulose solubilization was systematically investigated. The binary acid (phenol + sulfuric acid) at 180 °C was found to be superior amongst other studied enhancers, giving 81.17% (w/v) hemicellulose solubilization in liquid-fraction under optimized conditions. Solid residue thus obtained was subjected to enzymatic hydrolysis that resulted into 24.50% (w/v) cellulose breakdown. Treated solid residue was further characterized by scanning electron microscopy and fourier transform infrared spectroscopy to elucidate structural changes. The pooled fractions (acid treated and enzymatically hydrolyzed) were fermented using Clostridium acetobutylicum NRRL B 527 which resulted in butanol production of 5.18 g/L with yield of 0.13 g butanol/g sugar consumed. Therefore, pretreatment of pineapple peel waste evaluated in this study can be considered as milestone in utilization of low cost feedstock, for bioenergy production. [ABSTRACT FROM AUTHOR]

Pineapple peel is a renewable agricultural residue available in abundance whose multipurpose utilization deserves more attention. The present study aimed at the isolation of nanocellulose from pineapple peel and evaluation on its reinforcement capability for gellan gum film. The results from scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated the progressive removal of non-cellulosic components and the non-destruction of cellulose structure following bleaching and alkali treatments. Atomic force microscopy image of the nanocellulose displayed a needle-like structure with averages of 15 ± 5 nm in diameter and 189 ± 23 nm in length. Thermal gravimetric analysis (TGA) indicated that the obtained fibres after bleaching and alkali treatments showed higher thermal stability than the untreated pineapple peel. Although showing an earlier initial degradation temperature, the obtained nanocellulose remained the maximum residue after being heated to 500 °C. The rheological results indicated that the viscosities of the nanocellulose/gellan gum solutions increased slightly with the increase of nanocellulose content. The prepared films were characterized by FTIR, SEM, XRD, TGA, light transmittance and mechanical properties. The introduction of nanocellulose decreased light transmittance values but enhanced the thermal stability of gellan gum film. Compared with the neat gellan gum film, the 4% nanocellulose loaded gellan gum film showed 48.21% improvement in tensile strength. [ABSTRACT FROM AUTHOR]

• A new pretreatment technology of cellulose was developed. • The Fe2+ assisted cold plasma (CP) can successfully de-structured cellulose. • Fe2+ assisted CP pretreated cellulose to fabricate cellulose nanofibrils (CNF). • The mechanism of Fe2+ assisted CP pretreatment cellulose has been discussed. An effective method based on Fe2+ assisted cold plasma (CP) to pretreat pineapple peel cellulose for the preparation of cellulose nanofibrils (CNF) was proposed in this study. The mechanism underlying Fe2+ assisted CP pretreatment based on the structural changes of cellulose was investigated. Results showed that the cellulose preabsorbed Fe2+, followed by 60 min of CP treatment, and then was nanofibrillated into CNF via ultrasonication. Fe2+ assisted CP treatment exhibited strong capacity to significantly decrease the degree of polymerization of cellulose and to enhance electrostatic repulsion of fibrils. Furthermore, the roughness and breakage were observed on the surface of pretreated cellulose. The content of inter-molecular hydrogen bonds and average crystallite size (D hkl) also decreased significantly. The current results provided useful fundamental insights into Fe2+ assisted CP and cellulose interaction, which should be beneficial to developing new pretreatment methods for disintegrating cellulose into CNF. [ABSTRACT FROM AUTHOR]

Pineapple (Ananas comosus L. Merr.) peels as agricultural wastes represent around 35% of the whole fruit mass. By different preparation methods, the pineapple peel fiber was analyzed and evaluated for its composition and functional properties, which would provide a clue to its physiological function. The pineapple peel contained an appreciable amount of insoluble fiber-rich fraction (FRF) (41.8 - 48.0 g/100 g) including insoluble dietary fiber (IDF), alcohol-insoluble solids (AIS), and water-insoluble solids (WIS), which primarily consisted of cellulose, pectic substances and hemicellulose. These fractions also contained notable proportions of lignin (60.7 - 65.8 g/100 g). Compared with cellulose, these FRFs exhibited the greater water- and oil-holding capacities (7.94 - 12.3 mL/g and 5.84 - 8.64 g/g, respectively), swelling properties (10.6 - 18.4 mL/g), and cation-exchange capacities (102 - 120 mequiv/kg). The results indicate that the physicochemical properties of various fibers are dependent on the preparation method and composition. Every insoluble FRF studied possesses interesting characteristics, suggesting possible uses in the development of functional food ingredients for reduction of calories or dietary fiber enrichment. [ABSTRACT FROM AUTHOR]