Sorption characteristics of N-nitrosodimethylamine onto biochar from aqueous solution

N-nitrosodimethylamine (NDMA) is an emerging carcinogenic disinfection by-product in water environment. Biochars utilized as sorbents for the removal of NDMA from aqueous solution, and the sorption characteristics and mechanism were investigate. Biochars were prepared from bamboo, rice straw and wood sawdust at 300-700°C. The pseudo-second-order model provided the best fit for the sorption kinetics of NDMA onto biochar and the sorption isotherms were described best with the Slips model. Biochar produced at 500°C removed NDMA from aqueous solution relatively efficiently, and the bamboo char demonstrated the best sorption potential among the three types of biochars. Solution chemistry such as pH and metal ions did not show obvious effect on NDMA removal. Three sorption mechanisms are suggested for NDMA sorption onto biochars, H-bond attraction between -N=O and the O-containing moieties, hydrophobic force between -CH3 and the ordered graphitic structure, and partition process of NDMA into the non-carbonization part of biochar.