Detoxification of nicotine solution using Fe0-based processes: Toxicity evaluation by Daphnia magna neonate and embryo assays

Three Fe0-based techniques were used to treat wastewater containing nicotine. Daphnia magna neonates and embryos were used in bioassays to evaluate the toxicity of nicotine before and after the treatments. The results show that nicotine was highly toxic to Daphnia neonates (EC50, 48h = 0.379 mg L−1, EC50, 72h = 0.125 mg L−1). Although nicotine was moderately toxic to Daphnia embryos after a 48 h exposure (EC50, 48h = 250.8 mg L−1), nicotine was highly toxic to the embryos (EC50, 72h = 1.328 mg L−1) when exposure time was extended to 72 h. Nicotine induced malformations in the second antenna, carapace, and tail spine. The Fe0/air process was unable to effectively degrade nicotine. In contrast, the Fe0/H2O2 process and micro-electrolysis efficiently removed nicotine within 30 min (90.8% and 94.6%, respectively). The chemical oxygen demand removed by micro-electrolysis (70.4%) was clearly higher than that removed by the Fe0/H2O2 technique (58.1%). Micro-electrolysis maintained its effectiveness (>81.3%) after seven reuse cycles. A spectral analysis indicated that the micro-electrolysis process effectively removed the pyridine (A260) and pyrrolidine rings (A206) of nicotine. The toxicity of Fe0/H2O2- and micro-electrolysis-treated solutions were low (3.75% embryo mortality rate after 72 h). The above results show that micro-electrolysis is a potential approach to remove nicotine from solution.