Acetonitrile is regarded as a key solvent in the pharmaceutical industry. However, the volatility in acetonitrile supply in recent years, coupled with its relatively poor environmental profile, has presented significant challenges to its use in manufacturing processes and laboratories. This study investigates the importance of acetonitrile in the pharmaceutical industry and critically examines several options for reducing the exposure of the industry to future supply problems whilst also improving its life cycle management. The physicochemical properties of acetonitrile were compared with other typical process solvents and the Conductor-like Screening Model (COSMO) surfaces and sigma profiles were used to help explain the favourable solvation behaviour of acetonitrile. Several options for the replacement or recovery and recycle of acetonitrile were critically examined in the contexts of environmental, technical and economic feasibility. Azeotropic distillation was found to be the most likely approach to recovering acetonitrile from aqueous waste streams. Several potential breaking agents were assessed against a range of selection rules based on residue curve maps, determined using the Universal Functional Activity Coefficient (UNIFAC) method, and potential processing issues. A range of ionic liquids were screened via the predictive Conductor-like Screening Model for Realistic Solvation (COSMO-RS) approach and several promising candidates were identified. Experimental vapour-liquid equilibria studies were carried out, confirming the feasibility of ionic liquid-enhanced azeotropic distillation as a novel approach to acetonitrile recovery.

Based on continuous electrodeionization (CEDI) technology, a novel hybrid electrochemical acidification process has been developed to extract large quantities of CO 2 from seawater. This indirect approach acidifies seawater to recover CO 2 from bicarbonate. The electrolytic regeneration of cation exchange resin allowed simultaneous and continuous ion exchange and regeneration to occur within the cell along with control of the seawater pH. Lowering seawater pH was found to be proportional to the applied current to the cell, and the CO 2 in the acidified seawater was readily removed at pH less than 6.0. In addition, the cell produced a portion of hydrogen gas without additional energy penalties.

A novel electrochemical acidification process has been developed in a successful feasibility attempt to extract large quantities of CO 2 in the form of bicarbonate and carbonate from seawater for potential use as a source of carbon for hydrocarbon production at sea. This indirect approach acidifies seawater by the electrolytic production of acid. Lowering seawater pH was found to be proportional to the applied current to the cell. Spontaneous degassing and recovery of CO 2 below pH 4.5 was reduced from 92% in synthetic seawater to 30% in natural seawater. The effects of increased operational time, flow rate, current, and natural seawater's complex equilibrium buffer on process performance and CO 2 recovery have been shown to be essential for further improvements in future cell design, efficiency, and scale-up.