Choline chloride based natural deep eutectic solvent for destabilization and separation of stable colloidal dispersions

In solid-liquid separation processes, coagulation/flocculation is one of the most popular techniques in treating wastewater, as it is efficient, simple, and economical. Consequently, the formation of a new environment friendly destabilizing agent needed for the development of this processes. Hence, the aim of this paper is to introduce a new green and cheap choline chloride (ChCl) based natural deep eutectic solvent (NADES) as a coagulant for clay-based dispersions which are known to be a highly stable colloidal systems. For the NADES preparation, lactic acid (LA) and ChCl were used as the hydrogen bond donor and acceptor, respectively with a 1:1 ratio. Furthermore, the individual components of the NADES; ChCl and LA were also separately tested as coagulants as well as a binary mixture of both. Zeta potential, turbidity, floc size distribution, settling behavior, and viscosity measurements were conducted to study the potential of NADES in destabilizing and separating of high-stable bentonite dispersions and determine the strength of the resultant flocs. Initially, at pH 10, bentonite suspension had a high turbidity of 347 NTU and zeta potential of − 45 mV. At optimum concentration the reduction in turbidity and zeta potential were as follows: 5.32 NTU with − 30.6 mV, and 4.3 NTU with − 22 mV was achieved using ChCl alone and mixture of ChCl and LA (ChCl-Cl), respectively. NADES showed the most efficient performance with almost 100% turbidity removal and a significant reduction in the zeta potential of − 18 mV. For the three tested coagulants (ChCl, ChCl-LA, and NADES), produced flocs ranged in size from 5 μm to 36 μm depending on the coagulant type and dosage were achieved. NADES produced the largest flocs followed by ChClLA and ChCl. The obtained results were also confirmed through settling rate and sediment volume in addition to the viscosity measurements of the resultant flocs

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Published in: Separation and Purification Technology
License: http://creativecommons.org/licenses/by/4.0/
See article on publisher's website: https://dx.doi.org/10.1016/j.seppur.2020.117737