Application of TiO2 nanoplates anatase [001] impregnated on Luffa Cylindrica for biostimulation of biogas production from cassava wastewater

Anaerobic digestion (AD) has been intensively applied in the treatment of effluents, as it allows the recovery of energy and value-added chemical products. However, limitations such as the reduction of the biomass hydrolysis rate can affect the performance of the process. Thus, the addition of nanoparticles (NPs) with the reactive surface area can favor the metabolism of microorganisms, resulting in the rapid conversion of organic matter into bioenergy. However, the recovery of these NPs and their possible reuse in AD stands out as a limitation not yet evaluated. Consequently, this study explored the interrelationship of the addition of TiO2 nanoplates anatase [001] impregnated on Luffa Cylindrica (LufTiO2) and the reuse of this nanocatalyst (LufTiO2R) in the production of biogas from cassava wastewater. The results showed that the addition of (LufTiO2 and LufTiO2R) caused a reduction in the system delay time and an increase in biogas production by stimulating microbial metabolism. The batches LufTiO2 and LufTiO2R started the stabilization of biogas production from the 5th day of AD, the period in which the pH presented values lower than 4. Differently, the Control and LufTiO2P25 stabilized the biogas production on the 19th day. The COD reduction was noted in the following order: LufTiO2 (39%) > LufTiO2R (34%) > LufTiO2P25 (33%) > control (30%), suggesting the presence of organic acids in the digested materials and hydrogen in the biogas produced. After ecotoxicological evaluation of the digested materials, it was observed that the presence of these compounds formed during the acidogenic phase caused the lethality of Lactuca sativa seeds in all samples with a concentration above 6.25%. Therefore, the results highlight the potential for the application and reuse of TiO2 nanoplates anatase [001] through the combination of nanotechnology and natural fibers as a promising method to stimulate the production of biogas from cassava wastewater.