Elsevier

Water Research

Volume 171, 15 March 2020, 115472
Water Research

Regeneration and reuse of microbial extracellular polymers immobilised on a bed column for heavy metal recovery

https://doi.org/10.1016/j.watres.2020.115472Get rights and content
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Highlights

  • EPS was immobilised on a column for continuous heavy metal adsorption and recovery.

  • EPS could be regenerated and reused for repetitive adsorption-desorption cycles.

  • 99.9% of Cu2+ and Pb2+ were adsorbed before the breakthrough point.

  • 86–99% of adsorbed metal ions could be recovered.

  • Ion-exchange was the major adsorption mechanism.

Abstract

Microbial extracellular polymeric substances (EPS) have gained increasing attention for various water treatment applications. In this study, EPS produced from nitrogen-limited glycerol/ethanol-rich wastewater were used to recover Cu2+ and Pb2+ from aqueous solutions. Continuous flow-through tests were conducted on a column packed with silica gel coated with polyethyleneimine, to which EPS were irreversibly attached as shown by optical reflectometry. These immobilised EPS excellently adsorbed Cu2+ and Pb2+, with 99.9% of influent metal adsorbed before the breakthrough points. Metal desorption was achieved with 0.1M HCl, with an average recovery of 86% for Cu2+ and 90% recovery for Pb2+. For the first time, we successfully showed the possibility to regenerate and reuse the immobilised EPS for five adsorption-desorption cycles (using Cu2+ as an example) with no reduction in the adsorbed amount at the breakthrough point (qbp). Based on the mass balance of the associated metal ions participating in the adsorption process, ion exchange was identified as the major mechanism responsible for Cu2+ and Pb2+ adsorption by EPS. The results demonstrate the potential of wastewater-produced EPS as an attractive and perhaps, cost-effective biosorbent for heavy metal removal (to trace effluent concentrations) and recovery (86–99%).

Keywords

Biosorption
Column
Extracellular polymeric substances
Ion exchange mechanism
Metal adsorption

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