## 1 Introduction  
Despite the decline in oil reserves, dependence on the petrochemical industry is still high, since there is no alternative energy source able to satisfy the demands of the world's population. Treatment of crude gives rise to a range of valuable products, such as fuels, waxes, asphalt, polymers, plastics, paints, tires, and detergents. Among the most important oil fractions are the short paraffins (C\({}_{n}\)H\({}_{2n+2}\)), since these compounds are main components of fuel and natural gas that have relatively low toxicity, because their combustion only generates CO\({}_{2}\). A challenge for the petrochemical industry is olefin/paraffin separation, since both display similar physicochemical properties [1]. The use of membranes, cryogenic distillation, and absorption have emerged as potential methods for the separation of paraffin/olefin [2; 3; 4; 5]. Among them, the most sustainable technology is related to selective adsorption of olefins, since its insaturation favors stronger interactions with the adsorbent [4]. However, the interaction of paraffins is more limited, since these compounds are only formed of C-C and C-H bonds, so the adsorption should take place through nonspecific interactions. Traditionally, molecular sieves such as zeolites [6; 7], activated carbons [8; 9], and metal-organic frameworks (MOFs) [10; 11], which display cavities with a specific pore size, have been used as efficient sieves to separate paraffin. However, these compounds also have some drawbacks related to the low thermal stability of the MOFs and the cost of synthesizing molecular sieves with appropriate pore size at a large scale. Currently, companies demand competitive adsorbents with lower production costs in order to increase the profit margin. Natural clay minerals and zeolites are abundant and inexpensive natural molecular sieves that have been used in several adsorption processes [12; 13; 14] and paraffin separation [7]. Similarly, volcanic glass, a less well-known material than zeolites or clay minerals, has shown interesting behavior in the adsorption of harmful cations [15; 16] and dyes [17; 18; 19] and in the separation of olefin/paraffin [20]. So volcanic glass should be considered as a potential adsorbent to separate \(n\)-paraffins. The genesis of volcanic glass takes place by a sudden cooling of the magma, obtaining a quasi-stable and amorphous structure [21]. The most abundant volcanic glass is obsidian, which was used as a knife blade or scalpel blade since prehistory [22; 23]. Volcanic glass is a material that displays low thermal conductivity, low density, and high resistance to fire and perlite aggregate plasters. Hydration of obsidian leads to perlite, which shows a wider range of applications due to its high adsorption of sound, low bulk density, low thermal conductivity, and fire resistance, all of which provides interesting properties when used in the construction industry as plaster, insulation boards, and concrete, as well as a soil conditioner or carrier for herbicides, insecticides, and chemical fertilizers. In addition, perlite can be used for filtering water and other liquids, in food processing, and in pharmaceutical manufacturing [24]. Volcanic glass has also been used as starting material in the synthesis of clay minerals [25], as smectites, or as zeolites [26; 27]. The aim of this research is to evaluate Cuban volcanic glass in two consecutives processes, the adsorption of transition metal cations and then its application to the separation of liquid paraffins. The adsorption capacity of volcanic glass was evaluated using Cu\({}^{2+}\) cations as target metal. Cu species are considered pollutants from the mineral and metallurgic industries.