| Safe drinking water is the basis of human health, social stability and economic development. During disinfection, the disinfectants can react with organic precursors of source water and result in dinsinfect by-products (DBPs), which are serious damage to the human health. Nitrosamine, as emerging nitrogenous DBPs, has been hot issue of research among the domestic and foreign scholars due to its potential carcinogenicity, teratogenicity and mutangenicity. According to the highly toxic effects of nitrosamines, it is of great significance for keeping human health and developing safe dringing water industry to control and elimitate nitrosamine DBPs in dringking water. On the basis of brief introduction about the toxic effects, occurrence and cotrol technologies of nitrosamine DBPs, the sorption characteristics, structure-activity relationship and affecting factors of N-nitrosodimethylamine (NDMA) with other nitrosamines onto biochar and organic bentonite were mainly studied. Sorption mechanism was also investigated and the results were expected to provide theory basis for developing economic and efficient nitrosamines sorbent and controlling nitrosamine DBPs in drinking water. The main innovative conclusions of this work are drawn as follows:(1) Sorption properties of NDMA onto biochar varied with different pyrolysis temperature and source materials. The removal efficiency of NDMA by the same biochar increased with increasing temperature (300～500℃), but significantly decresed when the pyrolysis temperature rised to 700 ℃. Bamboo biochars showed stronger sorption potential compared with rice straw biochar and wood biochar, and the removal efficiency of BC500 was 2.2 times of that of RC500 and WC500. Deduced sorption mechanisms of NDMA sorption onto biochar included 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 and other micromechanism.(2) Preparation temperature significantly affected the surface structure, property and sorption characteristics of NDMA onto bamboo biochars. The carbon content, surface area, aromaticity and removal efficiency of NDMA by bamboo biochars increased with increasing pyrolysis temperature. Also, the Freundlich parameter KF and Langmuir maximum sorption capacity qm presented positive correlation with aromaticity and surface area, while negaitively correlated with polarity. NDMA sorption onto bamboo biochars producted under low temperature was linear sorption mainly controlled by partition process, while bamboo biochars producted under high temperature showed nonlinear sorption caused by combined inteaaction mechanism.(3) Sorption potential of biochar for different nitrosamines increased with increasing hydrophobicity of nitrosamine, and Freundlich parameter KF and Langmuir parameter qm of sorption isotherms positively correlated with logKow of nitrosamines. Competetitive sorption of coexisted nitrosamines occurred on the surface of bamboo biochar and activated carbon, and more hydrophobic nitrosamine showed stronger inhabitation effect on coexisted compound. Competitive sorption caused dearease of sorption capacity for single nitrosamine, while the total sorption capacity of nitrosamines in multi-solute system was higher than the maximum sorption capacity of nitrosamines in single-solute system.(4) The sorption process of N-nitrosodiphenylamine (NDPhA) and diphenylamine (DPhA) onto organo-bentonite were mainly controlled by chemical sorption. Partition was the main mechanism of N-nitrosodiphenylamine sorption onto organo-bentonite, while sorption contribution of diphenylamine included both surface sorption and partition. The removal efficiency of N-nitrosodimethylamine by organo-bentonite was positively correlated with the reciprocal of sorbent concentration in aqueous solution, and the maximum sorption capacity of diphenylamine decreased with increasing dosage of organo-bentonite. |
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