Adsorption Isotherms: Enlightenment of the Phenomenon of Adsorption

Adsorption is a process in which a substance that is in a liquid phase accumulates on a solid surface and is then removed from the liquid phase. An adsorption isotherm describes the equilibrium of adsorption of a substance on a surface at a constant temperature. It represents the amount of material bound to the surface as a function of the material present in the solution. In the adsorption process, the compound to be removed is called the adsorbate and the solid on which the compound is adsorbed is called the adsorbent. The affinity of the adsorbate for the adsorbent is quantified using adsorption isotherms. Adsorption isotherms are mathematical equations that describe the relationship between the amount of adsorbate adsorbed on an adsorbent and the concentration of adsorbate in solution when equilibrium has been reached at constant temperature. Adsorption isotherms are performed by giving a volume-determined solution containing a known amount of adsorbate along with various dosages of the adsorbent. The mixture is held at constant temperature with stirring until it reaches equilibrium. When this is the case, the concentration of the adsorbate in the aqueous phase is measured and the adsorption capacity at equilibrium for each experiment is calculated from the mass balance

Effect of Acid Treatment on the Physicochemical Characteristics and Sorption Capacity of a Natural Zeolite

Mining is a very important industry for the development of emerging economies; however, it generates a large number of environmental externalities such as acid mine drainages; these have acid pH values and high heavy metal content. Although there are several methods for the elimination of metals in different solutions, they require a large economic investment. Recently, the use of adsorbent materials for the removal of heavy metals in acid drains such as agricultural by-products and natural zeolites has been developed as a cheaper alternative. In spite of the environmental benefits of using natural zeolites as adsorbent, one of the disadvantages is dealumination, which to a great extent could depend on the geological origin of the mineral that shapes some of its characteristics. This study characterized chemical and physical properties of natural and modified zeolites using various techniques, such as X-ray diffraction (XRD), N2 adsorption- desorption, inductively coupled plasma − optical emission spectroscopy (ICP-OES), and SEM-EDS to determine the effect of an acid treatment on the physical and chemical characteristics of a natural zeolite, correlating these with their sorption capacity. When giving acid treatment to a zeolite there are no significant changes in the crystal structure, the Si/Al ratio indicates a dealumination of the structure but with minimal changes, the surface area and density of the micropores increased considerably. A significant increase in the capacity of copper adsorption was registered. According to XRD, no significant changes occur to the structures. Keywords: Dealumination; aluminosilicates; AMD; acid treatment; metal removal. DOI: 10.7176/JEES/10-9-05 Publication date:September 30th 202