A quest for electrode materials: heat stable salts removal from industrial lean amine solution via electro-sorption

The accumulation of heat stable salts (HSS) can cause deterioration performance of gas treatment amine units. In this work, electro-sorption batch experiments using different electrodes such as copper, stainless steel, aluminum foil, platinized coated titanium and nickel foam were conducted for the removal of HSS from industrial lean methyldiethanolamine (MDEA) solutions. Initially, salt removal was examined by using copper electrodes in two different configurations: inside and outside the designed cell i.e. by direct and indirect contact with the lean amine. It was found that copper electrode outside the cell has zero impact on HSS removal and hence all the electrodes were tested in a direct contact electrochemical cell. It was observed that the applied voltage has a significant role on HSS removal and should be adjusted according to the nature of electrode materials in order to achieve maximum separation and also to avoid catalysis. Different experiments were carried out by varying electrode materials and electric potential. Nickle foam (Ni) and platinized (Pt) coated titanium (Ti) showed the maximum HSS removal of 6.5% and 9.6% at a voltage of 0.8V and 1.2V respectively, while naked and modified SS 316 L has zero or negative impact on HSS removal. The electrochemical characteristics such as areal capacitance, cyclic voltammetry and its effect on scan rate for nickel and Pt coated Ti electrode was investigated. The effect of magnetic field and its direction was also analyzed by applying a magnetic force of 1 Tesla on the best electrode so far found (Pt coated Ti) and observed that in a batch mode of operation, the magnetic field cannot enhance the HSS removal efficiency.