RESUMO
This paper presents an approach for hydrolyzing cellulose nanocrystals from oil palm empty fruit bunch (OPEFB) presented through hydrochloric acid hydrolysis under sonication-hydrothermal conditions. Differences in concentration, reaction time, and acid-to-cellulose ratio affect toward the yield, crystallinity, microstructure, and thermal stability were obtained. The highest yield of cellulose nanocrystals up to 74.82%, crystallinity up to 78.59%, and a maximum degradation temperature (Tmax) of 339.82 °C were achieved through hydrolysis using 3 M HCl at 110 °C during 1 h. X-ray diffraction analysis indicated a higher diffraction peak pattern at 2θ = 22.6° and a low diffraction peak pattern at 2θ = 18°. All cellulose nanocrystals showed a crystalline size of under 1 nm, and it was indicated that the sonication-hydrothermal process could reduce the crystalline size of cellulose. Infrared spectroscopy analysis showed that a deletion of lignin and hemicellulose was demonstrated in the spectrum. Cellulose nanocrystal morphology showed a more compact structure and well-ordered surface arrangement than cellulose. Cellulose nanocrystals also had good thermal stability, as a high maximum degradation temperature was indicated, where CNC-D1 began degrading at temperatures (T0) of 307.09 °C and decomposed (Tmax) at 340.56 °C.
RESUMO
This research has successfully fabricated ion selective electrode (ISE) for Pb2+ using castor oil (Ricinus communis L.)-based polyurethane (PU) membrane with 1,10-phenanthroline as the active agent. The sensitivity of the Pb2+ ISE obtained is 27.25 mV/decade with a linear range of [Pb(NO3)2] of 10−10−10−5 M and a coefficient of determination (R2) of 0.959. The system response reaches stability after 25 s of measurement. The Pb2+ has a detection limit of 10−10 M and gives a stable response at pH 7−8 with a 15-day lifetime. The investigation of the selectivity of the ISE was performed using the mixed solution method with log Kij values of <1. The selectivity order of Pb2+ ISE against the foreign ions is Ag2+ > Ca2+ > K+ > Mg2+ > Cu2+ > Fe3+ > Cr3+> Zn2+ > Cd2+. The Pb2+ ISE shows acceptable reproducibility and repeatability with standard deviation values of 0.065 and 0.0079, respectively. Fourier transform infrared (FT-IR) spectra confirmed that 1,10-phenanthroline was responsible for the formation of the Pb2+ ion entrapment via complexation. Other characterizations (crystallinity, micro-surface morphology, and mechanical strength) suggest the degradation of the membrane structure integrity after the application. The analysis results of Pb levels using the Pb2+ ISE in artificial and wastewater samples were not significantly different from the atomic absorption spectroscopy (AAS) measurement.
RESUMO
This work aims to encourage the use of natural materials for advanced energy applications, such as proton exchange membranes in fuel cells. Herein, a new conductive membrane produced from cassava liquid waste was used to overcome environmental pollution and the global crisis of energy. The membrane was phosphorylated through a microwave-assisted method with different phosphoric acid, (H3PO4) concentrations (10-60 mmol). Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), dynamic mechanical analysis (DMA), swelling behavior test, and contact angle measurement were carried out on the membrane doped with different H3PO4 levels. The phosphorylated NdC (nata de cassava) membrane doped with 20 mmol (NdC20) H3PO4 was successfully modified and significantly achieved proton conductivity (maximum conductivity up to 7.9 × 10-2 S cm-1 at 80 °C). In addition, the fabricated MEA was assembled using an NdC20 membrane with 60 wt% Pt/C loading of 0.5 mg cm-2 for the anode and cathode. Results revealed that a high power density of 25 mW cm-2 was obtained at 40 °C operating temperature for a single-cell performance test. Thus, this membrane has the potential to be used as a proton exchange membrane because it is environment-friendly and inexpensive for fuel cell applications.
