Quick-fix agarose beads impregnated with hydrous ferric oxide for As(III) species removal from pharmaceutical wastewater

ABSTRACT

Hydrous ferric oxide (HFO)-impregnated agarose beads were prepared as an adsorbent to reduce As(III) concentration in the pharmaceutical wastewater effluent generated from the manufacturing process of an arsenic-containing chemotherapeutic drug. The adsorbent was prepared by immersing wet agarose beads into FeCl₃ (aq), followed by another immersion into NaOH (aq), resulting in HFO precipitation directly within the agarose beads. The As(III) adsorption rate of HFO-impregnated agarose beads was determined to be external diffusion-limited, and having a Langmuir maximum adsorption capacity of 76.1 mg As(III)/g. Passing 6 L of the pharmaceutical wastewater through a packed column filled with the adsorbent in an upflow mode of 50 mL/min repeatedly for five times resulted in the reduction of As(III) concentration from 250 to 10 μg of As(III)/L of H₂O. Column desorption was performed by passing 0.6 L of 0.1 M NaOH (aq) through the column in an upflow mode of 50 mL/min repeatedly for five times to regenerate the As(III)-adsorbed HFO-impregnated agarose beads. Chemical characterizations revealed that the As(III) species were adsorbed on HFO by the “inner-sphere” bidentate complexation via ligand exchange or “outer-sphere” association via electrostatic interaction, while the “outer-sphere”-associated As(III) species were most likely desorbed.

KEYWORDS:

• Hydrous ferric oxide
• agarose
• arsenic
• adsorption
• desorption

Acknowledgements

This work was supported by the Ministry of Science and Technology of Taiwan, R.O.C. under grant number of 107-2218-E-008-020-, 108-2218-E-008-013-, and 107-2221-E-008-037-MY3. We are grateful for the assistances provided by Precious Instruments Utilization Center of National Central University for XPS, TGA, and SEM. We would like to express our gratitude to Instrumentation Center of National Tsing Hua University and the Instrument Center of National Cheng Kung University for ICP-MS. Assistance provided by Professor Cheng-Yi Liu’s Lab in SEM is gratefully acknowledged. We also express our gratitude to Professor Andrew Tien-Shun Lin’s Lab for the freeze-dryer.

Disclosure Statement

The authors declare no competing financial interest.

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Additional information

Funding

This work was supported by the Ministry of Science and Technology [107-2218-E-008-020-,107-2221-E-008-037-MY3,108-2218-E-008-013-].