Enhanced removal of hexavalent chromium by lignosulfonate modified zero valent iron: Reaction kinetic, performance and mechanism

The application of lignin derivative as modifier is an economical and efficient approach to improve the reactivity of raw material towards pollutant removal . In this study, lignosulfonate modified zero valent iron (LS-ZVI) was firstly prepared by ball-milling method and utilized for Cr(VI) removal under different conditions. The comparative experiments showed that lignosulfonate modification could significantly enhance the Cr(VI) removal by ZVI from <10 % to 100 % within 90 min reaction. Compared to ZVI, the specific surface area of LS-ZVI increased 3.4 times and surface Fe(0) content increased from 3.4 % to 10.5 % due to the surface erosion, resulting in the high-efficient Cr(VI) removal. Solution and solid-phase analyses indicated that Fe(0) played dominated role and generated Fe(II) involved in Cr(VI) removal process, which mainly included rapid adsorption, reduction and co-precipitation. Batch experiments revealed that lower pH conditions were beneficial for Cr(VI) removal and the effect of co-existing ions (Ca 2+ , Mg 2+ , NO 3 − , Cl − , and SO 4 2− ) was negligible except the inhibitory effect of NO 3 − . Moreover, LS-ZVI also exhibited excellent removal performance for Ni(II), Zn(II), and Cd(II) with removal efficiency beyond 96.6 %. Overall, this work provides a feasible approach for enhancing the reactivity of commercial ZVI in the treatment of heavy metal pollution.