Removal of fluoride from electronic industrial effluent by RO membrane separation

The electronics industry generates large amounts of fluoride-containing effluents. The objective of this study is to study the feasibility of applying reverse osmosis (RO) membrane separation to reduce fluoride load to less than 1 kg/d. The effect of transmembrane pressure on the removal of fluoride ion has been investigated in detail, and the design parameters of a small RO separation unit were estimated. The present study indicated that the rejection of fluoride ion is typically higher than 98%, considering that the RO membrane was fully regenerated after each set of experiments. The effect of upstream concentration on the required mechanical pressure was determined by estimating the theoretical osmotic pressure of the feed solution. For industrial effluents, the process developed in this work allows us to reduce the treated volume from 6 m3/d to 0.36 m3/d without any pretreatment or adding additional compounds. The cost of the designed RO separation plant (€76,000) is much less than that of the conventional treatment (€533/m3) that deals mainly with volumes rather than specific fluoride removal.

This feasibility study has demonstrated that RO is suitable to the treatment of the fluorides present in the effluents of the electronics industry. It is the first time that this type of wastewater is treated by RO. It retains all the fluoride ions (retention factor over 98%). The RO can be considered for the retention of fluoride even for high concentration. However, when the upstream concentration increases, the downstream Fig. 7. Mass balance.