Comparison of the efficiency of different chitosan composites in immobilisation of chromium in contaminated soils

ABSTRACT

To investigate the effect of different chitosan composites on the immobilisation of chromium in soil, a pot factorial experiment was conducted in greenhouse conditions using a completely randomised design with three replications. Factors studied were soil chromium levels (0, 20, 60, and 180 mg kg⁻¹) and types of adsorbent applied to the soil, including pure chitosan, biochar, zeolite, manganese dioxide and composites of chitosan-biochar, chitosan-zeolite, chitosan-manganese dioxide and control. The application of different adsorbents to soil decreased the concentrations of DTPA and MgCl₂ extractable chromium and chitosan composites, especially chitosan-manganese dioxide, were more effective for the immobilisation of chromium in the soil than the pure adsorbents. Reductions in DTPA-extractable chromium by pure biochar, zeolite, manganese dioxide, and chitosan were 34.9%, 29.4%, 19.8%, and 15.1% and by composites of chitosan-manganese dioxide, chitosan-biochar and chitosan-zeolite were 54.8%, 46.8%, and 39.7% respectively when compared to the control treatment. The use of different adsorbents significantly reduced the labile forms and thus the mobility of chromium in the soil and the composite adsorbents were more effective than the pure adsorbents. It is concluded that coating different adsorbents with chitosan increases their efficiency in immobilising chromium in soil.

KEYWORDS:

• Soil pollution
• chitosan composites
• chromium
• sequential extraction

Acknowledgements

The authors would like to thank professor Ravi Naidu, Global Innovation Chair and Director, Global Centre for Environmental Remediation, The University of Newcastle, Australia for reviewing of the manuscript and giving valuable comments.

Disclosure statement

The authors declare no conflicts of interest.

Additional information

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.