Silica removal from brine by using ion exchange
Local governments have been forced to look for additional water sources to satisfy the ever increasing demand for fresh water. Very often, the new water sources such as the underground water in continental territories have high salt content. Currently, reverse osmosis technology (RO) is one of the most common processes for water desalination. However, this process is limited by high silica and salt concentrations in water. At high concentrations silica clogs the membranes used in the RO process, reducing their life and increasing operational costs. In this study, quaternary ammonium resins and sulfonic acid resins were used to remove silica and hardness, respectively from brines of both a nano-filtration pilot plant and a synthetic silica solution. Experiments were performed under bath and flow conditions at neutral pH. For batch experiments two anionic quaternary ammonium resins and one cationic sulfonic acid resin were used at 0.02 to 10 g in 50 mL of solution to carry out equilibrium tests. The resins were also tested for silica removal from a synthetic solution (without hard cations) at pH values from 3 to 11 and from brines of a nano-filtration pilot plant (NFPP) at pH ranging from 8 to 10. For flow experiments, the resins were used at flow rates from 8.7 to 10.5 cm/min, and pH values from 8 to 10. In all cases the amounts of silica and hard cations were determined by inductively coupled plasma optical emission spectroscopy, or by the photometric determination of molybdate-reactive method or using the titrimetic method with EDTA. Results showed that pH highly influenced silica removal from water solutions using quaternary ammonium resins in the chloride form. For both resins, silica removal efficiencies were higher than 80% at pH > 9.0 and less than 5% at pH < 8.0. Removal efficiency from the synthetic solution was about 62% and from the brine of the NFPP it was about 14%. The hardness of the brine from the NFPP was found to be about 700 mg/L, which suggests that hard cation complexes in solution limit the efficiency of silica removal using quaternary ammonium resins.
Inorganic chemistry|Environmental engineering
Acevedo, Carlos R, "Silica removal from brine by using ion exchange" (2009). ETD Collection for University of Texas, El Paso. AAI1473845.