Development and characterization of poly (vinyl) alcohol/cellulose nanofibril hybrid aerogel [EMBARGOED]

Abstract

The fast industrialization and urbanisation have contributed to water pollution, which has decreased the availability of clean water. Inorganic compounds make up the majority of the contaminants found in wastewater. Adsorption has been acknowledged as a practical and affordable approach of treating wastewater. The purpose of this study is to develop an adsorbent material based on poly(vinyl) alcohol/cellulose nanocrystal hybrid aerogel (PCHA) for the removal of toxic organic chemicals like methylene blue (MB) dyes from wastewaters. Cellulose nanocrystal (CNC) has good interaction with cationic dyes like methylene blue. Poly(vinyl) alcohol (PVA) is cheap and has excellent biodegradability, biocompatibility, and non-toxicity which is suitable as the base material. However, cellulose PVA aerogel has weak stability in water. The PVA based aerogels were prepared and reinforced with various amount of glutaraldehyde (GA) (80, 120, 160 µL) and the renewable CNC (0.25, 0.5, 0.75 wt%) via crosslinking, followed by freeze-dry process. The fabricated PCHA was further modified with electron beam (EB) irradiation (5, 10, 20 kG?). The carboxylated CNC was produced using two-step oxidation treatment involving bleaching and ammonium persulfate (APS) from oil palm residue. Detailed chemical and physical characterization studies of CNC were performed using XRD, FTIR, TG/DTG, and SEM/TEM. The crystallinity index of CNC improved significantly compared to raw fibre. FTIR analysis confirmed the presence of carboxyl groups. Both XRD and FTIR also proved that majority the non-cellulosic components had been removed. TEM revealed the CNCs have spherical-shaped about 16.33 ± 8.5 nm in diameter. On the contrary, the thermal stability of the CNC had slightly decreased. Furthermore, the PCHAs were also characterized with various characterization techniques. The FTIR results proved that the GA assisted the crosslinking between the PVA and CNC. From the SEM analysis, PCHA samples exhibited different pore shapes and sizes that were associated with the various CNC and GA contents. The crosslinking percentage and mechanical properties were further improved after EB modification; over 90% of crosslinking yield and had 18 times higher of compressive strength, respectively. The MB adsorbed percentage decreased as the GA content increased. However, the addition of CNC has positive effect on the rapid MB adsorption. Meanwhile, EB irradiation further decreased the overall MB adsorption performance of PCHA-4 samples.