Liquid–liquid separation of aqueous ammonia using a hollow-fibre membrane contactor

Abstract

Ammonia in the form of gas or ammonium ion is toxic to the environment. Removal of this compound in either form is important in order to meet the limits set by regulatory authorities. The treatment of the polluted waters can be accomplished by a variety of physical, chemical, and biological methods. Liquid–liquid separation is one of the promising methods that has been developed and demonstrated success for removing ions selectively. In many industrial operations, the solvents used are fossil fuel-based (a non-sustainable source), they have undesirable properties (toxic, corrosive, and health and safety issues). In recent years, there has been research work to examine the feasibility of other solvents from sustainable source and with good characteristics to minimize some of the above adverse effects. In this study, the effectiveness of a new solvent, sunflower oil, is described in the removal of ammonium in a small-scale pilot process at their natural pH. High percentage removal was achieved (in the range 43–73%) from a high feed of concentrated ammonia solution (25,600 ppm). It would require 1,000 L of sunflower oil with 100 L of D2EHPA to treat 1 m3 of ammoniated seawater to reduce the concentration to 3,750 ppm from such high concentration. With this reduced concentration, the treated water is suitable for irrigation purposes. The main attraction of the process is the performance of sunflower oil, which offers the benefit of being environmentally friendly, less costly, non-toxic, and from a sustainable source.