2023 Volume 27 Issue 3-4 Pages 33-39
In this work, the removal of boron (B) in wastewater was investigated by the coprecipitation method using bivalent metal ion as a precipitant. From the preliminary experiments conducted under the fundamental conditions, the removal percentage (coprecipitation degree) of B was found to be quite different depend on the kind of metal ions used, and it became the highest as 95.9% when Ni2+ ion was adopted. Also, the residual B concentration was under the limited value (10 mg/L) of the regulation for wastewater. Then, the optimum conditions in this case were studied in detail and the result was as follows; Initial B concentration=300 mg/L, Ni2+/B molar ratio=12/1, temperature 25°C and pH 9–10. Comparing with the Ni–Al layered double hydroxide prepared under the same condition, this nickel hydroxide precipitate indicated much higher removal ability for B. The precipitate obtained at the optimum condition was mainly the layered nickel hydroxide coordinating borate ion in the interlayer space, which basal spacing being 0.80 nm. Depending on the conditions, several other precipitates such as nickel hydroxide hydrate (3Ni(OH)2·2H2O) and theophrastite (Ni(OH)2) formed highly accompanying borate ion on their surface or inside. In conclusion, new simple method for the B removal by the coprecipitation using Ni2+ ion at higher pH was proposed in this study.
