Fabrication of layered double hydroxide/carbon nanomaterial for heavy metals removal

Layered double hydroxide (LDH)/sheet-shaped carbon composites are recently drawing increasing interests in various fields. Different from the conventional synthesis procedure, the composites in this work were directly prepared by in situ formation of carbon nanosheets via hydrothermal or high-temperature carbonization of organic LDH. The layered structure of LDH can be well retained after the preparation procedures and the carbon materials have sheet-like morphology evenly distributing along with LDH. The composites possess ample functional groups containing C, N, and S. Importantly, the types and relative amounts of the functional groups can be regulated via the two different carbonization methods. Abundant carboxyl and sulfonic groups are presented on the sample from hydrothermal method, while the high-temperature carbonized product mainly contains hydroxyl and thiophenol/thiol. These two different carbonization strategies also cause large differences in specific surface area of the composites; high-temperature carbonization treatment favors the production of large specific surface area. LDH/carbon nanosheets show much better adsorption performance than LDH toward both Cr(VI) and Cd(II), with maximum of 4.4and 6.7-fold increase of the adsorbed capacities, respectively. This work provides facile ways for preparation of LDH/carbon nanosheets materials, which may also be ways for recycling of waste organic clay and organic clay minerals by producing functional materials.