Influence of feed salinity on ammonia recovery from high-strength effluents in transmembrane chemical absorption process

Abstract

Transmembrane chemical absorption (TMCS) is a promising technology to recover ammonia from high-strength wastewater and sustainably produce fertilizers for agricultural propose. In this study, the effect of ionic strength was analyzed by modelling and experiments, to establish the impact of the salinity of the treated effluent on the performance (ammonia recovery and water vapour transfer). The non-ideality of the solution is considered and the effect of pH, ionic strength and temperature is analyzed by a thermodynamic model approach using Phreeqc software. Results reveal that high ionic strength can play a positive or negative role in ammonia recovery efficiency, depending on the pH of the solution. The salinity also influences water vapour diffusion through the membrane which can negatively impact the process by diluting the ammonium salt produced. Results show that water vapour transfer is linearly correlated to ionic strength. It can occur in both directions from effluent to acid or inversely depending on difference of ionic strength. The impact of salinity of the effluent on ammonia and water vapour transfer through gas-permeable membranes was theoretically and experimentally assessed.