###### Abstract  
A product is characterized by low environmental impact if, during the whole process (from extraction of raw materials from solid natural matter to disposal), its negative contribution to environment modification is significantly reduced or eliminated. According to circular economy, it is important to take into consideration other aspects, such as the possibility to improve the efficiency of extraction process by modifying the principle on which it is based and allowing the recovery of not completely exhausted waste, obtaining other active ingredients, and favoring the recycling of normally eliminated materials. The purpose of this work was to propose more efficient and greener alternatives to conventional solid-liquid extraction processes. Major features are the rapidity of the process, extraction at room temperature and high yields. Rapid Solid-Liquid Dynamic Extraction (RSLDE) represents an innovative solid-liquid extraction technology that allows the solid matrices containing extractable substances in an organic or inorganic solvent and their mixtures to be exhausted in shorter time than current techniques. The principle at the basis of this novel process consists of the generation of a negative pressure gradient between the inside and the outside of the solid matrix, which induces the extraction of compounds not chemically linked to the solid matter, being insoluble in the extractant liquid. Therefore, this work focuses on how RSLDE can potentially bring several improvements in the field of solid-liquid extraction, especially for industrial applications. s +
Footnote †: journal: Applied Sciences  
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Exploiting the pressure-depression effect, this process forces the release of substances that are not chemically linked to the main insoluble structure of solid matrix and accelerates the process [2]. Conventional techniques such as maceration and percolation or solid-liquid extraction occurs essentially for two effects: diffusion and osmosis [3,4]. For this reason, they are defined as passive processes, as it is necessary to wait for the slow diffusion times to complete the process. The increase in temperature and the occasional agitation of the extraction system are the only parameters that can speed up the process. Unfortunately, even if the increase of temperature helps to speed up diffusion (Fick's Law), on the other hand it degrades the molecules extracted from the plant matrices, which in most cases are thermolabile [5, 6, 7]. On the other hand, RSLDE works by alternating a static phase with a dynamic one [8,9]; during the static phase, the extracting solvent is brought to a pressure of about 9 bar and kept in this state for a time sufficient to reach an equilibrium between the pressure of the liquid outside the solid matrix and the liquid inside it (generally 1 to 3 min): the static phase is followed by the dynamic one, produced by the displacement of the pistons, which causes the pressure reduction [10]. At this point, the extraction of the solid matrix takes place, made possible by a pressure difference between the inside and outside of the sample. The extractable substances, at each extraction cycle, are dragged for a sucking effect and that is why this extraction process is considered \"active\". Furthermore, the dynamic phase (following static phase) allows the rapid and complete mixing of the solid matrix and an instant diffusion of the extracted substances throughout the mass of the liquid, avoiding oversaturation phenomena that can take place around solid matrix: a high concentration of extracted compounds brings a premature equilibrium that stops the extractive process. This extraction technology represents a valid alternative to other currently existing solid-liquid extraction techniques and brings considerable innovations and advantages to obtain high-quality extracts.