Effects of different concentrations of Fe3O4@ZnO and Fe3O4@CNT magnetic nanoparticles separately and in combination on aquaculture wastewater treatment

The present study is aimed at improving aquaculture wastewater quality using nanomaterials while producing minimal environmental impact. For this purpose, zinc oxide (ZnO) and carbon nanotubes (CNT) nanoparticles were coated with iron oxide (Fe3O4) to create magnetic nanoparticles. After inclusion in the wastewater, these particles are capable of treating wastewater, facilitating their removal using a magnetic device. Properties of Fe3O4@ZnO and Fe3O4@CNT coated nanoparticles properties were analyzed by FT-IR, VSM, XRD and SEM methods. Experiments were conducted in three stages: in the first, triplicate treatments of Fe3O4@ZnO and Fe3O4@CNT were evaluated separately using a static system (10-1). During the second stage, combinations of the two best Fe3O4@ZnO and Fe3O4@CNT concentrations determined in the first stage were compared. In the third stage, the treated wastewater was then exposed to Daphnia magna zooplankton for 12 h to evaluate daphnia survival as a test of treatment toxicity. In the first and second stages, the wastewater parameters measured included: nitrate,phosphate,BOD5, TDS, coliform MPN, Cu and Cr heavy metal. According to the first stage results, 30 and 50 mg/L Fe3O4@ZnO and 15 and 20 mg/L Fe3O4@CNT showed the greatest improvement on wastewater quality. These treatments were then evaluated during the second stage, in combination. Results revealed that interactions between both nanoparticles strongly affected (P<0.05) all the wastewater quality parameters except TDS. In the third stage, the findings showed that removal of the coated magnetic nanoparticles by a magnet is very efficient and does not produce any toxic effects to the water causing significant mortality on the Daphnia magna. The results of this study indicate that the combination of these magnetic nanoparticles at 30 mg/L Fe3O4@ZnO and 20 mg/L Fe3O4@CNT is optimal for aquaculture wastewater treatment while producing minimal environmental impact. (C) 2019 Elsevier B.V. All rights reserved.