TiO₂–AgCl Based Nanoparticles for Photocatalytic Production of Phenolic Compounds from Lignocellulosic Residues

Abstract

Lignocellulosic biomass residues can be used as an interesting resource for the production of biochemicals or sustainable fuels. In this optic, lignin represents an interesting raw material for the production of chemicals, such as aromatic compounds, or fuels. This can contribute in moving away from petroleum-based industries to bio-based industries. The aim of this study was to investigate the application of a photocatalytic process using a commercial solution composed by TiO2 doped with AgCl for wheat straw valorization. The study investigated the effect of pH and catalyst concentrations for optimal phenolic compounds production. It was found that the photocatalytic treatment boosted the phenolic production from wheat straw. The efficiency of the process depended on the initial pH and catalyst concentration. Process optimization towards increased phenolic compounds production was performed. Catalyst concentration of 1 g/L and a treatment time of 1.56 hours in alkaline conditions resulted in the highest phenolics production. Use of the photocatalytic treated wheat straw for anaerobic digestion (AD) was also evaluated. Results showed that the AD microbiome is strongly inhibited by the presence of toxic compounds presented in the catalyst-straw solution and specifically, HNO3 was toxic to methanogenic communities. Hence, to succeed in an efficient biorefinery framework where total phenols and biogas production are combined, the usage of HNO3 for catalyst synthesis should be avoided.

Carbon dioxide anion radical as a tool to enhance lignin valorization

“…To study the effect of radicals on cellulose or hemicellulose of wheat straw, sCOD % change was introduced at the next step during model development. For experiment 10 (control; only water), no change or slightly higher production of TPC for lignin and wheat straw, respectively were found, which is in line with our previous study (Tsapekos et al, 2018).…”

“…For the 2 nd and rd cycles the TPC increased by 44.392 ± 3.280% and 10.30 ± 1.961%, respectively. The final value of TPC at the end of 2 nd and 3 rd cycles were 93.972 ± 3.161 mg/g and 103.651 ± 5.964 mg/g, respectively, which is comparable with the value of 94.6 mg/g reported in our previous study (Tsapekos et al, 2018). It is important to note that these observations are not in accordance with predicted results from Eq.…”

TiO2 supported natural zeolites as biogas enhancers through photocatalytic pre-treatment of Miscanthus x giganteous crops

“…respectively. An interesting work by Tsapekos et al [27] reports production of phenolic compounds from TiO2-AgCl photocatalysis of lignin in wheat straw, which are toxic to anaerobic consortia. In this study, the concentration of phenolic and other aromatic structures was not measured after treatment however, BMP results discussed later in this section demonstrate no inhibition took place, meaning inhibitory levels were not reached during fermentation.…”

“…In fact, where digestion of substrates is characterised by high A:V indicators, this substantially results in decreased methane yield [30,31]. From the ultimate analysis, it can be noticed that the C:N of the feedstock is out of range of the optimal digestion values (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) identified by Chen et al [32] however, the inoculum-to-substrate ratio used in the BMP trials (4:1 w/w as per standard procedure) contributed to normalise this parameter much closer to the ideal range.…”

Cotton fibres functionalized with plasmonic nanoparticles to promote the destruction of harmful molecules: an overview

“…Plasmonic photocatalysis can be a good strategy [28]. This consists in the inclusion of NPs of different nature such as Ag 0 [29,30], Au 0 [31,32], Cu 0 [33], Pt 0 , Pd 0 [34] or their halides such as AgBr [35] or AgCl [36] dispersed in the semiconducting TiO 2 layer. This allows two prominent effects to take place: the formation of a Schottky junction and of a localized surface plasmonic resonance (LSPR).…”