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Iron-modified biochar-based bilayer permeable reactive barrier for Cr(VI) removal
Ziyi Zhou1, Peng Liu1, Sheng Wang2
1School of Environmental Studies & State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China.
Journal of Hazardous Materials
|July 31, 2022
Summary
Iron-modified biochar (FeBC) effectively removes hexavalent chromium (Cr(VI)) from groundwater in permeable reactive barriers (PRBs). A FeBC and limestone combination demonstrated superior Cr(VI) removal and iron (Fe) retention.
Area of Science:
- Environmental Science
- Water Treatment Technology
- Materials Science
Background:
- Hexavalent chromium (Cr(VI)) contamination in groundwater poses significant environmental and health risks.
- Iron-modified biochar (FeBC) is a promising material for Cr(VI) remediation in permeable reactive barriers (PRBs).
- Understanding Cr(VI) removal mechanisms and iron (Fe) leaching in FeBC-based PRBs is crucial for effective application.
Purpose of the Study:
- To evaluate the long-term performance of FeBC-based permeable reactive barriers (PRBs) for Cr(VI) removal.
- To investigate the chemical processes governing Cr(VI) removal and Fe release in FeBC systems.
- To assess the efficacy of a bilayer FeBC and limestone system (FeBC_Ca_BC) for cost-effective Cr(VI) remediation.
Main Methods:
- Column experiments were conducted over 563 days using three different FeBC-based PRB configurations.
- Cr(VI) and Fe concentrations, pH, and flow rates were monitored throughout the experiments.
- Cr and Fe speciation and complexation within the biochar matrix were analyzed using advanced characterization techniques.
Main Results:
- The bilayer FeBC_Ca_BC system exhibited the highest Cr(VI) removal efficiency at a low treatment cost.
- Fe corrosion was primarily influenced by pH and Cr(VI) concentration, not flow rate.
- Leached Fe was effectively attenuated by biochar and limestone, with evidence of Fe re-utilization within the FeBC_Ca_BC system.
- Cr(VI) was reduced to Cr(III) and adsorbed/precipitated onto biochars, forming stable inner-sphere complexes that penetrated the biochar structure.
Conclusions:
- The combined FeBC and limestone system is highly effective for long-term Cr(VI) removal from groundwater.
- The FeBC_Ca_BC system minimizes Fe release and promotes Cr sequestration, offering a sustainable water treatment solution.
- This study provides critical insights into the reaction mechanisms and long-term stability of FeBC-based PRBs for chromium remediation.
