Desorption of zinc, copper and lead ions from loaded flax fibres

Biosorption is an efficient and cost-effective method for heavy metals' remediation. However, saturated biosorbents may pose a serious problem for the environment. Flax fibres have shown very good adsorption capacities to remove zinc, copper and lead ions from contaminated aqueous solutions. In this study, adsorption-desorption cycles were conducted with loaded flax fibres in batch mode to recover heavy metals using four types of solutions: hydrochloric acid solution, nitric acid solution, sodium hydroxide solution and ultrapure water. Desorption kinetic studies, conducted with loaded flax fibres, showed very fast desorption of zinc, copper and lead when using nitric and hydrochloric acids with a selectivity sequence of Zn (totally desorbed) > Cu (94%) > Pb (80-73%). Desorption kinetic was slower with the use of sodium hydroxide and showed much lower desorption rates of Zn (62%) > Pb (12%) > Cu (7%). Desorption of zinc and copper from previously loaded fibres from binary metal ion system in lead solution was also investigated. Different concentrations ranging from 0.04 to 0.20 mmol/L were tested. The obtained results demonstrated a significant release in the order Zn (18-90%) > Cu (2-42%), while lead was still efficiently adsorbed. Retention efficiencies of zinc and copper and adsorption efficiency of lead resulted in the same adsorption efficiencies of the three metal ions onto flax fibres in the ternary metal ion system.

Automated summary

This study investigated the recovery of heavy metals using different solutions for adsorption-desorption cycles. The results showed that nitric and hydrochloric acids resulted in fast desorption of zinc, copper, and lead, while sodium hydroxide had slower desorption rates. Additionally, the study found that zinc and copper were released to a higher extent from fibers previously loaded in lead solution, while lead still remained efficiently adsorbed.