Adsorption of PCB 3 on organomodified LDHs
Résumé
1200 million ton of Polychlorinated biphenyls (PCBs) have been produced worldwide and about 400 million tons are considered to be spread in the Environment. PCBs are persistent pollutants and highly immunotoxic toxic and carcinogenic. They may concentrate in river sediments and strongly affect ecosystems and biodiversity. Conventional cleaning processes are environmental non-friendly methods and there is still need to look for alternative ways of treating these contaminations. Washing sediments with surfactant solutions offers good results. Layered Double Hydroxides (LDH) are synthetic anionic clays that have proved to be good adsorbant for both surfactant and organic pollutants. Modification of LDH by anionic surfactant or polymer enhances their adsorption properties toward hydrophobic xenobiotics. This study aims to develop a new cleaning process based on the adsorption of PCBs by organically modified LDH. 4-chlorobiphenyl (PCB 3) was used as a model. ZnRAl LDH materials with variable anion exchange capacities, intercalated by sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (SDBS) or humic acid were tested as new sorbents. PCB 3 adsorptions were processed either by intercalation or direct coprecipitation (scheme). Surfactant modified LDH show a great ability to trap PCB 3, about 97% adsorbed, all the same by coprecipitation with pollutant. Humic acid adsorbed LDH are less efficient, with a maximum of 50% of adsorption.