The depletion of fossil fuels calls for the development of renewable alternatives such as biodiesel and has inspired much research on catalysts for the production of biodiesel through the esterification of biomass-derived materials. Herein, a green heterogeneous catalyst for highly efficient biodiesel synthesis was fabricated from rice straw–derived cellulose, hematite, and zirconia and was shown to contain porous irregularly shaped α-Fe2O3–ZrO2 composites (average particle size = 42.5 nm) evenly distributed on the nanocellulose surface. The optimal catalyst (nanocellulose:α-Fe2O3–ZrO2 = 2:1, w/w) afforded biodiesel in a yield of 92.50% and with specifications close to those prescribed by international standards. This catalyst could be reused for up to five cycles without a marked activity loss, with the biodiesel yield in the fifth cycle equaling 80.0%. The developed nanocomposite holds great promise for cutting the costs of biodiesel production, as it is derived from biodegradable raw materials and is renewable, non-corrosive, easy to handle, and green. In addition, the large-scale discharge of this catalyst after use does not pose a hazard to the environment.

In the present work, sustainable green catalysts with high activity, and excellent stability were prepared and thoroughly characterized by XRD, FT-IR, BET, VSM, SEM, EDX, HR-TEM, and TGA techniques. The combined sodium alginate (SA) and carboxymethyl cellulose (CMC) biopolymers were functionalized with Fe₃O₄ nanoparticles to immobilize copper nanoparticles to form Fe₃O₄@SA-CMC-CuNP nanocomposites in batch experiments. Furthermore, the Fe₃O₄@SA-CMC-CuNP nanocomposites were utilized as the heterogeneous catalyst for 4-nitrophenol (4-NP) reduction to 4-aminophenol (4-AP) in the presence of NaBH₄, and the progress of the catalytic reaction was monitored using UV-visible spectrophotometry. The Fe₃O₄@SA-CMC-CuNP nanocomposite exhibited much higher catalytic activity for the 4-nitrophenol reduction reaction than individual components Fe₃O₄ and Fe₃O₄@SA-CMC. The effect of parameters such as the amount of catalyst was evaluated and 30 mg of the catalyst amount with a 95.0% reduction of 4-nitrophenol for 1.5 min was obtained. The effect of reaction temperature was also investigated to find out the activation energy. The analyses of kinetics and thermodynamics were carried out to understand the catalytic behavior. Furthermore, the catalyst can be separated from the reaction system through the usage of a magnet and recycled up to five times without any loss of activity. Therefore, the development of sustainable green catalyst biopolymer-based nanocomposites is promising for new catalysts in the future for treating organic wastewater.

A nanocomposite from cellulose-ZnO/SiO₂ has been successfully synthesized. Cellulose derived from rice husk has been converted into nanocellulose, then used as nanocomposite support material. Nanosilica is derived from calcination of rice husk ash as filler which combined with ZnO nanoparticle. The combination of ZnO/SiO₂ composite with nanocellulose biopolymers, a form of cellulose-ZnO/SiO₂ nanocomposite. The success of this work is supported by characterization with FTIR, XRD, and SEM-mapping. The distribution for each element of the SEM-mapping shows the Si element as filler in the pores and spread on the cellulose surfaces and the element of ZnO distributed evenly throughout the surface of cellulose and silica. The nanocomposite was applied as heterogeneous catalyst for transesterification of virgin coconut oil into biodiesel methyl ester. The optimum reaction time at 270 minutes and temperature at 60 °C obtained the methyl ester yield at 95 %. Application of nanocomposite-based biopolymers as heterogeneous catalysts for transesterification of virgin coconut oil into biodiesel methyl esters was succeeded, and promising for catalysts in the future.

In this study, nanocomposite based on biopolymer using sodium alginate (NaAlg) and bentonite intercalated by TiO₂ was synthesized. Bentonite in the nanocomposite was used as a template for TiO₂ nanoparticles formation through in-situ method and NaAlg was used as catalyst supporter in order to obtain nanocomposite material, which was expected as dye waste removal. The nanocomposite was characterized using Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) and Tunneling Electron Microscopy (TEM). The obtained nanocomposite had TiO₂ average nanoparticles size around 35 nm. Nanocomposite was applied for photocatalysis to remove the dye waste of methylene blue (MB). Degradation percentage was achieved at 90.50 % with the optimum condition at pH 8 with photocatalysis time at 30 min and 30 mg nanocomposite mass. Biopolymer-based sodium alginate and TiO₂-bentonite nanocomposite can be applied to reduce dyestuff that is biodegradable and environmentally friendly waste.