Boron evaporation in thermally-driven seawater desalination: Effect of temperature and operating conditions

The volatilization of boron in thermal desalination processes, namely multi-stage flash (MSF) and air-gap membrane distillation (AGMD) was investigated for the first time. This phenomenon was observed at feed temperatures above 55 °C in both studied processes. In simulated MSF process with two feeds, model boric acid and Red Sea water, boron concentration in distillate increased with feed temperature increase from 55 °C to 104 °C because of the increase in boric acid vapor pressure. Salinity and pH were the main factors controlling boron evaporation. The achieved boron concentrations in simulated MSF process were consistent with those measured in distillate samples collected from commercial MSF plants. The AGMD process also revealed a strong influence of operating temperature on boron removal. However, unlike MSF process, the boron concentration in AGMD permeate decreased with the feed temperature increase from 55 °C to 80 °C due probably to increase in vapor production and corresponding permeate dilution. When AGMD was operated in concentrating mode at a constant feed temperature of 80 °C, permeate boron concentration increased with process time due to concentration polarization and membrane fouling. A 10% flux decline observed after 21 h was attributed to CaCO scaling on the membrane surface.

Citation

Alpatova A, Alsaadi A, Ghaffour N (2018) Boron evaporation in thermally-driven seawater desalination: Effect of temperature and operating conditions. Journal of Hazardous Materials 351: 224–231. Available: http://dx.doi.org/10.1016/j.jhazmat.2018.02.056.

Acknowledgements

The research was supported by funding from King Abdullah University of Science and Technology (KAUST). The authors would like to thank Mr. Abdulrahman Aljadani and Dr. Abdelkader Meroufel and Dr. Mohammed Namazi for supplying water samples from commercial MSF plants. The authors appreciate Mrs. Tong Zhang for the ICP-MS training, Dr. Sheng Li for TOC/DOC analysis, and Mrs. Nini Wei for SEM imaging.