Adsorption and Removal of Organic Dye at Quartz Sand-Water Interface

We studied the transport, sorption and desorption of organic cation (Methylene Blue, MB) through a porous medium consisting of quartz sand particles negatively charged. We examined various parameters such as the ionic strength of the aqueous solution, the flow velocity, the pH of the aqueous phase, the temperature of the medium and the nature of the divalent metal cations present in solution, which affect the transport and the deposition of MB through the porous medium. Step-input experiments were carried out to measure the dye retention. The data showed a decrease in the MB adsorbed amount on the quartz, when the pH of the aqueous phase, or the temperature, decreases, or when the flow rate, or the affinity of the divalent cation (Ca2+, Cu2+, Zn2+ and Ba2+) toward the quartz surface increases. The increase in ionic strength leads to a small decrease in the MB adsorbed amount. However, the increase in temperature leads to an increase in the retained MB amount, which suggests that the adsorption of MB on the surface of quartz is endothermic in nature. The overall data indicate that, at ambient temperature, electrostatic interaction forces, which occur between the cationic organic pollutant and the negative surface of the quartz substrate, mainly control the adsorption process