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Arsenic sorption by red mud-modified biochar produced from rice straw
Chuan Wu1, Liu Huang1, Sheng-Guo Xue2
1School of Metallurgy and Environment, Central South University, Changsha, 410083, People's Republic of China.
Summary
Red mud-modified biochar (RM-BC) effectively removes arsenic (As) from water. This novel adsorbent shows a significantly higher adsorption capacity for arsenate compared to untreated biochar.
Area of Science:
- Environmental Science
- Materials Science
- Chemistry
Background:
- Arsenic (As) contamination in water poses significant environmental and health risks.
- Conventional adsorbents often have limitations in efficiency and cost-effectiveness.
- Red mud and biochar possess properties suitable for developing advanced adsorbents.
Purpose of the Study:
- To develop and characterize a novel red mud-modified biochar (RM-BC) adsorbent for arsenic removal.
- To investigate the adsorption mechanisms and kinetics of arsenate (As(V)) and arsenite (As(III)) on RM-BC.
- To evaluate the adsorption capacity and efficiency of RM-BC for arsenic remediation.
Main Methods:
- Red mud was modified onto biochar to create RM-BC.
- Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) and X-ray Diffraction (XRD) were used for characterization.
- Adsorption experiments were conducted under varying pH conditions.
- Adsorption kinetics and isotherms were analyzed using pseudo-second-order, Elovich, and Langmuir models.
- X-ray Absorption Near-Edge Spectroscopy (XANES) was employed to study adsorption mechanisms.
Main Results:
- SEM-EDS and XRD confirmed successful loading of red mud onto biochar.
- Adsorption of As(V) decreased with increasing pH, while As(III) adsorption increased.
- Arsenate adsorption followed pseudo-second-order kinetics, and arsenite followed the Elovich model.
- Langmuir model best described the sorption isotherms for both species.
- RM-BC achieved a maximum As(V) adsorption capacity of 5923 μg g⁻¹, approximately ten times higher than untreated biochar.
- XANES suggested that iron and aluminum oxides on RM-BC are key active sites for As(V) adsorption via surface complexation and electrostatic interactions.
Conclusions:
- RM-BC is a highly effective adsorbent for arsenic removal, significantly outperforming unmodified biochar.
- The adsorption mechanism involves interactions with iron and aluminum oxides, influenced by solution pH.
- RM-BC presents a promising, cost-effective solution for arsenic remediation using abundant waste materials.
