Efficient removal of hazardous benzohydroxamic acid (BHA) contaminants from the industrial beneficiation wastewaters by facile precipitation flotation process

Abstract Benzohydroxamic acid (BHA) is intensively used as collector in the mineral processing industry, and thus tremendous hazardous beneficiation wastewater containing BHA organic contaminant needs urgent treatment. In this work, an efficient removal of BHA organic contaminants from various industrial beneficiation wastewaters via the chelation, flocculation, and precipitation flotation process was studied. The removal efficiency of BHA, COD and turbidity of the purified water, and the chelation mechanism were investigated by optical microscope, SEM, FTIR, XPS, Zeta potential, and thermodynamic analyses. The results showed that organic BHA contaminant can be chelated firstly by Cu(II) to form hydrophobic BHA-Cu precipitate effectively via the “O-O” chelation and a five-membered chelation ring was formed under weak alkaline conditions. The generated precipitate was then successfully removed using CTAB as surfactant and NP-40 as frother in a microbubble flotation column. Over 94% BHA was removed under the optimal chelation, flocculation and flotation conditions: chelation with Cu(II) concentration of 30 mg/L and pH of 8 for 30 min; flocculation with CTAB concentration of 0.2 mg/L for 20 min; followed by flotation with NP-40 frother of 0.6 mg /L and air flow rate of 100 mL/min for over 40 min. Under this condition, 83.91% COD was removed, and the residuel COD and turbidity of the purified water were lower than 25 mg/L and 0.1 NTU, respectively, which met the wastewater discharge requirement. It’s demonstrated that the precipitate flotation can be employed as an effective method to purify industrial wastewater containing BHA. In addition, the interaction mechanism of Cu(II) and BHA under different pH values was also discussed in this work.