A Combined Approach for the Removal of Fe and Zn from Industrial Wastewaters: Electrically-Enhanced Membrane Bioreactor followed by Adsorption using Graphene Oxide and Silica

  • Menatalla AlaaEldeen L. Ahmed

Student thesis: Master's Thesis

Abstract

This study aimed at investigating the potential use of electrically enhanced membrane bioreactor (eMBR) for the removal of iron (Fe), zinc (Zn) and bacteria from industrial steel making wastewater. eMBR is a hybrid reactor that combines biodegradation of organic pollutants, submerged membrane filtration, and electrokinetics. Current density varying between 10 and 20 A/m2 was applied. Hydraulic retention time (HRT) and sludge retention time (SRT) of 13.5 h and 10 d were maintained, respectively. Each run was carried out for 45 d to ensure steady state operation. Fe and Zn concentrations in influent wastewater and treated effluent were measured by HACH LCK 321 and LCK 360 vials, respectively. X-ray Fluorescence Spectrometry (XRF) was used to analyze the concentration of Fe and Zn on electrodes deposits and sludge precipitates. Results showed that Fe removal of 98.4±1.1%, 81.1±12.3%, and 38.8±4.2%, and Zn removal of 93.8±2.7%, 71.8±17.7%, and 50.1±17.2 % were reported at 10, 15, and 20 A/m2, respectively. Also, XRF analysis at 10 A/m2 revealed higher Fe concentration was reported on the electrodes deposits (214.5±8.7 and 3.0±0.1 g/kg on the cathode and anode, respectively) compared to sludge precipitate (48.8±4.85 g/kg). Similarly, XRF analysis at 10 A/m2 revealed higher Zn concentration was reported on the electrodes deposits (19.7±3.2 and 0.62±0.3 g/kg on the cathode and anode, respectively) compared to sludge precipitate (8.2±1.78 g/kg). Consequently, it could be concluded that electrodeposition of ions was the predominant mechanism in eMBR for the removal of Fe and Zn from industrial wastewater. Afterwards, Zn in the treated eMBR effluent was removed by post-treatment via adsorption using nanomaterials. Three nanomaterials were tested, namely, graphene oxide, silica, and tin oxide. pH and adsorbent dosage were optimized, and the maximum Zn removal efficiency from eMBR effluent was reported to be 93.1±2.1%, 99.0±0.3%, and 83.2±3.51% for graphene oxide, silica, and tin oxide, respectively. The maximum Zn adsorption capacity was reported to be 243, 9.107, and 102.0 mg/g for graphene oxide, silica, and tin oxide, respectively. Adsorption isotherms verified a mechanism of monolayer adsorption for the three nanomaterials tested. Moreover, adsorption kinetic studies revealed that chemisorption is the predominant removal mechanism for the three nanomaterials. Inner sphere surface complex mechanism was predominant in the case of Zn adsorption on SnO2; however, adsorption on GO and SiO2 was governed by outersphere surface mechanism at low pH values, and inner-sphere surface mechanism at high pH values. Thus, the proposed two-stage treatment of industrial wastewater that consists of eMBR followed by adsorption using nanomaterial was found to be efficient in removing metals from water. This finding can open doors to introducing a novel integrated technology for industrial wastewater treatment.
Date of AwardMay 2017
Original languageAmerican English

Keywords

  • Iron (Fe)
  • Zinc (Zn)
  • Membrane Bioreactor (eMBR)
  • IndustrialWastewaters
  • Graphene Oxide
  • Silica.

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