Fixed-bed operation for manganese removal from water using chitosan/bentonite/MnO composite beads

Journal article

Authors / Editors

Ochieng, Aoyi

Research Areas

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Publication Details

Author list: Muliwa AM, Leswifi TY, Maity A, Ochieng A, Onyango MS

Publisher: Springer

Place: HEIDELBERG

Publication year: 2018

Journal: Environmental Science and Pollution Research (0944-1344)

Journal acronym: ENVIRON SCI POLLUT R

Volume number: 25

Issue number: 18

Start page: 18081

End page: 18095

Number of pages: 15

ISSN: 0944-1344

eISSN: 1614-7499

Languages: English-Great Britain (EN-GB)

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Abstract

In the present study, a new composite adsorbent, chitosan/bentonite/manganese oxide (CBMnO) beads, cross-linked with tetraethyl-ortho-silicate (TEOS) was applied in a fixed-bed column for the removal of Mn (II) from water. The adsorbent was characterised by scanning electron microscopy (SEM), Fourier transform infra-red (FT-IR), N-2 adsorption-desorption and X-ray photoelectron spectroscopy (XPS) techniques, and moreover the point of zero charge (pH(pzc)) was determined. The extend of Mn (II) breakthrough behaviour was investigated by varying bed mass, flow rate and influent concentration, and by using real environmental water samples. The dynamics of the column showed great dependency of breakthrough curves on the process conditions. The breakthrough time (t(b) ), bed exhaustion time (t(s) ), bed capacity (q(e) ) and the overall bed efficiency (R%) increased with an increase in bed mass, but decreased with the increase in both influent flow rate and concentration. Non-linear regression suggested that the Thomas model effectively described the breakthrough curves while large-scale column performance could be estimated by the bed depth service time (BDST) model. Experiments with environmental water revealed that coexisting ions had little impact on Mn (II) removal, and it was possible to achieve 6.0 mg/g breakthrough capacity (q(b) ), 4.0 L total treated water and 651 bed volumes processed with an initial concentration of 38.5 mg/L and 5.0 g bed mass. The exhausted bed could be regenerated with 0.001 M nitric acid solution within 1 h, and the sorbent could be reused twice without any significant loss of capacity. The findings advocate that CBMnO composite beads can provide an efficient scavenging pathway for Mn (II) in polluted water.

Keywords

Adsorption, Breakthrough, Composite beads, Fixed-bed column, Manganese

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