Development and Performance Test of Choline Chloride Based Natural Deep Eutectic Solvent for Separation of Colloidal Suspensions

Abstract

Clay minerals such as bentonite are considered as a valuable raw material for a variety of industrial applications including drilling fluids for oil and gas industries, cosmetics, papermaking, paint and dyes, pharmaceutical, cement, and water treatment. As a result, large volumes of wastewater contaminated with clay minerals are generated continuously. The presence of clay minerals in water demonstrates a serious problem due to their stability and separation difficulty raising the complexity of the treatment process. Therefore, the development and enhancement of the separation processes are of great interest in the academic and industrial fields. Among the available technologies, coagulation/ flocculation is the most utilized method for the separation of colloids because of its high-performance efficiency, simplicity, and economical properties. Inorganic coagulants like aluminum sulfate and ferric chloride are commonly used destabilizing agents for colloidal particles. However, due to the high dosage requirement, low efficiency, and toxicity, their use in wastewater treatment follows strict regulations. Hence, there has been an increasing need to find more suitable, efficient, and green alternatives for the traditional coagulants. Therefore, the main purpose of this research study was to introduce the novel application of choline chloride (ChCl) based natural deep eutectic solvents (NADESs) as a green coagulant for highly stable colloidal particles in suspension. The influence of ChCl-based NADES on the stability of bentonite suspension in terms of its electrokinetics properties, rheological behavior, and dewaterability was investigated. Furthermore, it analyzed the effect of the constituent components as coagulants of the suspension to determine the role of each component on the destabilization process. Consequently, the influence of water on the NADES interactions and hence on its destabilization efficiency were determined. The impact of each coagulant was illustrated in the floc size, zeta potential, turbidity removal, and the settling and rheological behavior of the produced flocs. And finally, the electrokinetic properties including the floc size, zeta potential, and pH of the system were employed to determine the optimum operating conditions in terms of the coagulant dosage and the bentonite concentration.