Biochar from Grapevine Pruning Residues as an Efficient Adsorbent of Polyphenolic Compounds

Abstract

Agricultural waste, which is produced in large quantities annually, can be a threat to the environment. Biochar (BC) production represents a potential solution for reducing the amount of grapevine pruning residues and, accordingly, the impact on the environment and climate change. Biochar produced by the process of pyrolysis from grapevine pruning residues was investigated and characterized to be applied as an adsorbent of polyphenolic compounds with the aim of using the waste from viticultural production to obtain a quality product with adsorption and recovery potential. Standards of caffeic acid (CA), gallic acid (GA), and oleuropein (OLP) were used as polyphenolic representatives. The obtained data were fitted with the Langmuir and Freundlich isotherms models to describe the adsorption process. The best KL (0.39) and R2 (0.9934) were found for OLP using the Langmuir model. Furthermore, the adsorption dynamics and recovery potential of BC were investigated using an adapted BC column and performed on an HPLC instrument. The adsorption dynamics of biochar resulted in the adsorption of 5.73 mg CA g−1 of BC, 3.90 mg GA g−1 of BC, and 3.17 mg OLP g−1 of BC in a 24 h contact. The online solid phase extraction of the compounds performed on an HPLC instrument yielded a recovery of 41.5 ± 1.71% for CA, 61.8 ± 1.16% for GA, and 91.4 ± 2.10% for OLP. The investigated biochar has shown a higher affinity for low-polar compound adsorption and, consequently, a higher polar compound recovery suggesting its potential as an efficient polyphenolic compound adsorbent.

From Waste to Green: Water-Based Extraction of Polyphenols from Onion Peel and Their Adsorption on Biochar from Grapevine Pruning Residues

“…Biochar adsorption capacity is a complex phenomenon affected by various factors, such as electrolyte content, temperature, pH, surfactant structure, pore volume, and the nature of the activated carbon used [ 39 , 40 ]. As previously reported, biochar from grapevine pruning residues is an efficient adsorbent of polyphenolic compounds [ 41 ].…”

Valorization of Olive Leaf Polyphenols by Green Extraction and Selective Adsorption on Biochar Derived from Grapevine Pruning Residues

“…In this study, the mentioned models were used to determine the adsorption process by which polyphenols from olive leaf extracts adsorb onto the BC from grapevine pruning residues. BC properties and adsorption capacity were described in our previous works [29,39]. Among all investigated compounds, hydroxytyrosol and the total amount of polyphenols fitted better in the Langmuir model, obtaining the R 2 closest to 1, suggesting the suitability of this model for the mentioned compounds' adsorption.…”

“…Those findings suggested that monolayer and heterolayer phenolic compounds may exist on the adsorbent surface due to the heterogeneity of the BC's surface [64]. In our previous work [29], BC from grapevine pruning residues was investigated as an adsorbent for polyphenols. In that paper, the standard of oleuropein, among others, was used.…”

“…The powder was subsequently sifted through a test sieve to achieve particle sizes ranging from 125 to 250 µm. The details of the production process and the characterization of the produced biochar is reported in Prelac et al [29].…”

“…Biochar (BC) from lignin or cellulose-rich plants could form more porous structures [26], making it more suitable for the removal of compounds. Furthermore, due to its properties such as large surface area, the presence of negatively charged organic functional groups, and its cation exchange capacity, it is considered to be an efficient adsorbent [28][29][30]. Several authors have reported biochar's capacity in the removal of pollutants and phenols [26,29,31].…”