Removal of Cadmium (II) using water hyacinth (Eichhornia crassipes) biochar alginate beads in aqueous solutions

• Published in: Environmental pollution (1987) 2020-09, Vol.264, p.114785-114785, Article 114785
• Main Authors: Liu, Cenwei, Ye, Jing, Lin, Yi, Wu, Jian, Price, G.W., Burton, D., Wang, Yixiang
• Format: Article
• Language: English
• Subjects: Biochar-alginate capsule; Heavy metals; Isotherms; Langmuir and freundlich isotherms; Water hyacinths
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2020.114785

Biochar produced from water hyacinths (Eichhornia crassipes) has been demonstrated to be an effective adsorbent for the removal of certain heavy metals and as a means of control for this highly invasive species. This study involved examined the Cd2+ sorption dynamics of an alginate encapsulated water hyacinth biochar (BAC) generated at different temperatures and modified using ferric/ferrous sulfate (MBAC). The maximum Cd2+ sorption occurred at a pH of 6 and at a solution temperature of 37 °C. Sorption equilibria for the biochar-alginate capsule (BAC) and modified biochar-alginate capsule (MBAC) treatments fit both the Langmuir (R2 = 0.876 to 0.99) and Freundlich (R2 = 0.849 to 0.971) equations. Langmuir isotherms had a better fit than the Freundlich isotherms, with maximum sorption capacities ranging from 24.2 to 45.8 mg Cd2+ g−1. Larger KL values in Freundlich modeling suggest strong bonding of the BAC and MBAC sorbents to Cd2+, with values of KL in the MBAC treatments ranging between 31 and 178% greater than the BAC treatments. Cd2+ sorption followed pseudo first-order kinetics (R2 = 0.926 to 0.991) with greater efficiency of removal using treatments with biochar generated at temperatures >500 °C. Results from this study highlight the potential for biochar-alginate capsules derived from water hyacinth to be effective for the removal of Cd2+ from wastewaters. [Display omitted] •Water hyacinth can be converted into biochar for removal of heavy metals from wastewater.•Biochar-alginate beads are easily dispersed in aqueous solution and can be recovered for reuse.•Water hyacinth biochar-alginate beads have high Cd2+ sorptive capacity.•Temperature regime during biochar generation plays an important role in sorptive capacity.•Biochar activated with iron is more efficient for removal of Cd2+ than biochar alone.