Boron removal from saline water by a microbial desalination cell integrated with donnan dialysis

• Donnon dialysis can assist with boron removal in an MDC system.
• The alkaline solution generated by the MDC acts as a stripping medium.
• The key challenge is to convert boron to borate ions.
• Boron removal is via both diffusion and ion exchange.
• Salinity of the salt solution can affect boron removal through ion competition.

Boron has toxic effects on plant growth and thus its removal is necessary from desalinated saline water for irrigation application. Microbial desalination cells (MDCs) are a new approach for effective desalination but boron removal has not been addressed before. Herein, MDCs were studied for boron removal with aid of Donnan Dialysis (DD). The alkaline solution generated by the MDC cathode was used to ionize boric acid to facilitate boron removal. An MDC system with DD pretreatment removed 60 or 52% of boron with the initial boron concentration of 5 or 20 mg L− 1. In the absence of DD, direct cathodic alkalinization of boron in an MDC was not effective in terms of boron removal and had a serious issue of salt accumulation. The MDC with DD post-treatment could reduce the boron concentration below 2 mg L− 1, although the high pH of its final effluent needs to be further addressed. Further investigation will consider an MDC system with both DD pre-treatment and post-treatment for improving boron removal.

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