Bio-derived MgO nanopowders for BOD and COD reduction from tannery wastewater

MgO nanopowders were synthesised via a simple and "greener" route using Carica papaya leaf extract at 500 degrees C. The bio-derived MgO nanopowders (MgONPs) were characterised by Brunauer-Emmett-Teller (BET), differential thermal and thermogravimetric (DTA-TGA) analysis, powder X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) equipped with an energy-dispersive spectroscopy (EDS). The COD and BOD reduction efficiency of the MgO NPs was evaluated in the presence of raw and simulated tannery wastewater. Under optimum conditions, the COD of raw tannery wastewater reduced from 2725.9 mg/L to 126.5 mg/L and BOD from 1899.5 mg/L to 104.5 mg/L in a batch system. Also, the turbidity was reduced from the initial concentration of 588 NTU to a level of 98 NTU within 120 min. Impressively, 93.5% COD reduction and 96.9% BOD reduction were obtained by the fixed-bed system. The spent MgO was regenerated and reused several times without significant loss of capacity. Hence, the bio-derived MgO nanopowders offered potential benefits for BOD and COD removal from tannery wastewater. (C) 2017 Elsevier Ltd. All rights reserved.