Lignocellulosic materials have been used as bioadsorbents for contaminants removal from industrial effluents due to their physical-chemical properties, renewable source, low-cost and efficiency that make them competitive to commercial activated carbon. The objective of this work is to develop an efficient and low cost bioadsorbent reusing the cashew nut shell (Anarcadium accidentale L), CNS, for the removal of metal ions (Cu2+ and Cr3+). The CNS was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), the point of zero charge (pHpzc) and the Boehm titration. The kinetics and adsorption equilibrium experiments were carried out in a monoelementary system, in batch runs at room temperature. The adsorption kinetics was evaluated by the mathematical models of pseudo first-order, pseudo second-order and intraparticle diffusion, while the adsorption isotherm was adjusted according to the Langmuir, Freundlich and Redlich-Peterson models. The removal percentage was 91% (Cu2+) and 96% (Cr3+) and adsorption kinetics was better adjusted to the pseudo second-order model, suggesting the predominance of chemisorption. The fit of the Langmuir isotherm was better for the experimental data of Cu2+ and Cr3+ ions, indicating adsorption in monolayers. It is concluded that the bioabsorbent produced from the cashew nut shell has a high potential for the removal of metals, in addition to being an abundant product in nature, is renewable and biodegradable and its reuse contributes to the reduction of environmental pollution, the production of waste and improves the local circular economy through the valorization of the byproduct.

Lignin, a complex aromatic biopolymer abundant as waste in biorefineries and the pulp and paper industry, holds significant potential for valorization. This study presents the oxidative depolymerization of Lignoboost lignin (LB) using H₂O₂ under mild, solvent- and catalyst-free, inherently acidic conditions at 50–70 °C. The process aimed to produce functionalized low-molecular-weight oligomers, retaining aromaticity, and aliphatic dicarboxylic acids, rather than complete monomerization. The depolymerized LB was rich in aromatic dimers-trimers (68.6 wt.%) with high functionalization (2.75 mmol/g OHphen, 3.58 mmol/g OHcarb, 19.5 wt.% of H in -CH=CH-), and aliphatic dicarboxylic acids (53.4 wt.% of monomers). Acidic conditions provided higher depolymerization and functionalization than alkaline, alongside simplified product recovery. The process was also successfully applied to Kraft lignin, demonstrating versatility and robustness even with higher polymeric content feedstocks. The optimized conditions were scaled up (×25), improving efficiency and yielding Mw 464 g/mol and Đ 1.3. As proof of concept, the scaled-up product underwent radical crosslinking, resulting in a new biopolymer with higher thermal stability than LB (54.2 wt.% residual mass at 600 °C versus 36.1 wt.%). This green, scalable process enhances lignin valorization by producing functionalized low-molecular-weight lignin oligomers and dicarboxylic acids that can be used independently or together to form crosslinked networks.

Materiais lignocelulósicos vem sendo estudados como possíveis adsorventes aplicados no tratamento de efluentes contendo íons metálicos. Um exemplo de material é a casca da Pachira aquatica que possui características favoráveis para o processo de biossorção. O presente estudo visou contribuir para os estudos de biossorção utilizando a Pachira aquática Aubl., investigando os fatores influentes no processo biossorção de Fe3+, Ni2+ e Cd2+ através do planejamento experimental. Foi utilizado o planejamento fatorial completo com três pontos centrais, utilizando quatro fatores com dois níveis cada (superior e inferior), totalizando 19 experimentos (24+3). O início dos experimentos se deu a partir da preparação do material bioadsorvente e das soluções metálicas, seguida da aplicação destes em ensaios de biossorção em batelada com variação dos fatores temperatura, pH, massa de bioadsorvente e concentração de adsorbato. Ao final dos ensaios obteve-se resultados satisfatórios para remoção dos íons metálicos principalmente quando os fatores pH, massa de bioadsorvente e concentração de adsorbato estavam em seus níveis superiores. O fator temperatura mostrou-se não significativo para adsorção de Fe3+ e Cd2+ e pouco significativo para Ni2+. Dessa forma a utilização do nível inferior de temperatura (30 °C) torna-se adequado, pois promovem processos mais econômicos. Utilizando os fatores em seus valores ótimos (mb=0,5g e ca=70mg/L) houve remoção de 100%, 99% e 100% de Fe3+, Ni2+ e Cd2+, respectivamente. Concluiu-se a partir dos resultados obtidos que o carvão vegetal produzido a partir da Pachira aquatica é eficiente para biossorção de Fe3+, Ni2+ e Cd2+.

Lignin, a complex aromatic biopolymer abundant as waste in biorefineries and the pulp and paper industry, holds significant potential for valorization. This study presents the oxidative depolymerization of Lignoboost lignin (LB) using H2O2 under mild, solvent- and catalyst-free, inherently acidic conditions at temperatures from 50-70°C. The depolymerized LB was rich in aromatic dimers-trimers (68.6 wt.%) with high functionalization (2.75 mmol/g OHphen, 3.58 mmol/g OHcarb, 19.5 wt.% of H in -CH=CH-), and aliphatic dicarboxylic acids (53.4 wt.% of the monomers). Acidic conditions provided higher depolymerization and functionalization than alkaline conditions, alongside simplified product recovery. The process was also successfully applied to Kraft lignin (KL) from black liquor, demonstrating its versatility and robustness. The optimized conditions were scaled up (×25), improving efficiency and yielding a Mw and Đ of 464 g/mol and 1.3, respectively. As proof of concept, the scaled-up product underwent radical crosslinking, resulting in a new biopolymer with higher thermal stability than LB (54.2 wt.% residual mass at 600°C versus 36.1 wt.%). This green, scalable depolymerization process enhances lignin valorization, producing two high-value compounds—low molecular weight functionalized aromatics and dicarboxylic acids—that can be used independently or together, owing to their inherent capacity to form crosslinked networks.