Removal of ionic liquid by engineered bentonite from aqueous solution

Understanding the adsorption of ionic liquids onto zeolite ZSM-5 from aqueous solution: experimental and computational modelling

Ionic liquids are considered as emergent pollutants as these compounds possess high persistence in aqueous solution and toxicity toward aquatic organisms. In this work, the adsorption equilibrium of 27 ionic liquids, with different cation head groups, alkyl chain lengths, and anions, onto ZSM-5 was measured experimentally at several compositions and at temperature 298.15 K and 0.1 MPa. The extensive number of ionic liquids studied allows a comprehensive study on the impact of adsorbate chemical structures toward their adsorption process. The gathered experimental results show that the anions have a dominant effect, when compared to the cation head group and the alkyl chain length, in ruling the adsorption of ionic liquids from aqueous solution onto ZSM-5. The adsorption isotherms reveal that the adsorption process is a combination between Langmuir and Freundlich behaviors, with the latter leading the general process. Moreover, computational modelling using COSMO-RS demonstrates the existence of several molecular forces that rule the adsorption process, reinforcing the idea that the ionic liquid anion rules the adsorption. The results collected in the present work provide new understanding on the molecular mechanism for the development of efficient adsorbents for removal and recovery of ionic liquids from aqueous solution.

Ionic liquid-based water treatment technologies for organic pollutants: Current status and future prospects of ionic liquid mediated technologies

Water scarcity motivated the scientific researcher to develop efficient technologies for the wastewater treatment for its reuse. Ionic liquids have been applied to many industrial and analytical separation processes, but their applications in the wastewater treatment, especially in the removal of organic pollutants, are still not well explored. Potential applications of ionic liquids include solvent extraction, solvent membrane technologies and ionic liquid-modified materials that are mainly used as adsorbents. Aforementioned technologies have been examined for the abatement of phenol, chloro- and nitrophenols, toluene, bisphenol A, phthalates, pesticides, dyes, and pharmaceuticals etc. Present review enlightens the application of different ionic liquids in wastewater treatment and suggests the versatility of ionic liquids in the development of rapid, effective and selective removal processes for the variety of organic pollutants. Implementation of ionic liquid based technologies for wastewater treatment have lots of challenges including the selection of non-hazardous ionic liquids, technological applications, high testing requirements for individual uses and scaling-up of the entire pollutant removal, disposal, and ionic liquid regeneration process. Toxicity assessment of water soluble ionic liquids (ILs) is the major issue due to the widespread application of ILs and hence more exposure of environment by ILs. The development of effective technologies for the recovery/treatment of wastewater contaminated with ILs is necessary from the environmental point of view. Furthermore, the cost factor is the major challenge associated with ionic liquid-based technologies.

Recovery and purification of ionic liquids from solutions: a review

With low melting point, extremely low vapor pressure and non-flammability, ionic liquids have been attracting much attention from academic and industrial fields. Great efforts have been made to facilitate their applications in catalytic processes, extraction, desulfurization, gas separation, hydrogenation, electronic manufacturing, etc. To reduce the cost and environmental effects, different technologies have been proposed to recover the ionic liquids from different solutions after their application. This review is mainly focused on the recent advances of the recovery and purification of ionic liquids from solutions. Several methods for recovery of ionic liquids including distillation, extraction, adsorption, membrane separation, aqueous two-phase extraction, crystallization and external force field separation, are introduced and discussed systematically. Some industrial applications of ionic liquid recovery and purification methods are selected for discussion. Additionally, considerations on the combined design of different methods and process optimization have also been touched on to provide potential insights for future development of ionic liquid recovery and purification.

Removal of Ionic Liquids from Oil Sands Processing Solution by Ion-Exchange Resin

Ionic liquids (ILs) have been reported to be good process aids for enhanced bitumen recovery from oil sands. However, after the extraction, some ionic liquids are left in the residual solids or solutions. Herein, a washing–ion exchange combined method has been designed for the removal of two imidazolium-based ILs, ([Bmim][BF4] and [Emim][BF4]), from residual sands after ILs-enhanced solvent extraction of oil sands. This process was conducted as two steps: water washing of the residual solids to remove ILs into aqueous solution; adsorption and desorption of ILs from the solution by the sulfonic acid cation-exchange resin (Amberlite IR 120Na). Surface characterization showed that the hydrophilic ionic liquids could be completely removed from the solid surfaces by 3 times of water washing. The ionic liquids solution was treated by the ion-exchange resin. Results showed that more than 95% of [Bmim][BF4] and 90% of [Emim][BF4] could be adsorbed by the resins at 20 °C with contact time of 30 min. The effects of some typical coexisted chemicals and minerals, such as salinity, kaolinite (Al4[Si4O10](OH)8), and silica (SiO2), in the solution on the adsorption of ionic liquids have also been investigated. Results showed that both kaolinite and SiO2 exerted a slight effect on the uptake of [Bmim][BF4]. However, it was observed that increasing the ionic strength of the solution by adding salts would deteriorate the adsorption of [Bmim]+ on the resin. The adsorption behaviors of two ILs fit well with the Sips model, suggesting the heterogeneous adsorption of ionic liquids onto resin. The adsorption of ionic liquids onto Amberlite IR 120Na resin was found to be pseudo-second-order adsorption. The regeneration tests showed stable performance of ion-exchange resins over three adsorption–desorption cycles.

Facile preparation of 3D GO/CNCs composite with adsorption performance towards [BMIM][Cl] from aqueous solution

A novel three-dimensional crumpled graphene oxide/cellulose nanocrystals (GO/CNCs) composite was successfully synthesized and firstly used as adsorbent for the removal of ionic liquid [BMIM][Cl] from aqueous solution. The 3D crumpled structure and abundant oxygen of the functional groups on GO/CNCs composite can provide more chance for the sorption of [BMIM][Cl] compared with CNCs and GO, respectively. Therefore, a series of batch experiments were carried out to evaluate the adsorptive property of 3D GO/CNCs composite towards [BMIM][Cl], such as the GO mass content, the pH value and contact time. The results showed that pseudo-second-order kinetic model and Eovlich model were well fitted with the sorption kinetic. The isotherm adsorption data indicated that it was better described by Langmuir model, with the maximum sorption capacity of 0.455mmol/g. This work provides a facile method for the preparation of 3D structure adsorbent from graphene oxide and cellulose nanocrystals which has high adsorption capacity of [BMIM][Cl] in aqueous solution.

Biosorbents based on agricultural wastes for ionic liquid removal: An approach to agricultural wastes management

Modified biochars produced from different agricultural wastes were used as low-cost biosorbents to remove hydrophilic ionic liquid, 1-butyl-3-methyl-imidazolium chloride ([BMIM][Cl]). Herein, the biosorbents based on peanut shell, corn stalk and wheat straw (denoted as PB-K-N, CB-K-N and WB-K-N) all exhibited higher [BMIM][Cl] removal than many other carbonaceous adsorbents and the adsorption capacities were as the following: PB-K-N > CB-K-N > WB-K-N. The characterizations of biosorbents indicated that they had great deal of similarity in morphological, textural and surface chemical properties such as possessing simultaneously accessible microporous structure and abundant oxygen-containing functional groups. Additionally, adsorption of [BMIM][Cl] onto PB-K-N, CB-K-N and WB-K-N prepared from the modified process, which was better described by pseudo-second order kinetic and Freundlich isotherm models. Therefore, the viable approach could also be applied in other biomass materials treatment for the efficient removal of ILs from aqueous solutions, as well as recycling agricultural wastes to ease their disposal pressure.