Tourmaline guiding the electric field and dechlorination pathway of 2,3-dichlorophenol by Desulfitobacterium hafniense

The dehalogenation of organohalides has been a research hotspot in bioremediation field;however,the influence of tourmaline,a natural ore that can generate spontaneous electric field,on organohalide-respiring bacteria(OHRB)and their dechlorination process is not well known.In this study,the effect and mechanism of tourmaline on the reductive dechlorination of 2,3-dichlorophenol(2,3-DCP)by Desulfitobacterium hafniense DCB-2Twere explored.The characterization results confirmed that tourmaline had good stability and the optimal dosage of tourmaline was 2.5 g/L,which shortened the total time required for dechlorination reaction to 72 hr.Besides,tourmaline amendment also increased the proportion of 2-chlorophenol(2-CP)from 18%to 30%of end products,while that of 3-CP decreased correspondingly.The theoretical calculations showed that the bond charge of the orthosubstituted chlorine declined from-0.179 to-0.067,and that of meta-substituted chlorine increased from-0.111 to-0.129,which indicated that the spontaneous electric field of tourmaline affected the charge distribution of 2,3-DCP and was more conducive to the generation of 2-CP.Overall,tourmaline with the spontaneous electric field affected the reductive dechlorination pathway of Desulfitobacterium,and the tourmaline-OHRB combining system might serve as a novel strategy for the bioremediation of environments polluted with chlorinated phenols.

Geobacter sulfurreducens promoted the biosynthesis of reduced graphene oxide and coupled it for nitrobenzene reduction

In order to explore an efficient and green method to deal with nitrobenzene(NB)pollutant,reduced graphene oxide(r GO)as an electron shuttle was applied to enhance the extracellular electron transfer(EET)process of Geobacter sulfurreducens,which was a typical electrochemically active bacteria(EAB).In this study,r GO biosynthesis was achieved via the reduction of graphene oxide(GO)by G.sulfurreducens PCA within 3 days.Also,the r GOPCA combining system completely reduced 50-200μmol/L of NB to aniline as end product within one day.SEM characterization revealed that PCA cells were partly wrapped by rGO,and therefore the distance of electron transfer between strain PCA and r GO material was reduced.Beside,the ID/IGof GO,r GO,and r GO-PCA combining system were 0.990,1.293 and 1.31,respectively.Moreover,highest currents were observed in r GO-PCA-NB as 12.950μA/-12.560μA at -408 m V/156 m V,attributing to the faster electron transfer efficiency in EET process.Therefore,the NB reduction was mainly due to:(I)direct EET process from G.sulfurreducens PCA to NB;(II)r GO served as electron shuttle and accelerated electron transfer to NB,which was the main degradation pathway.Overall,the biosynthesis of r GO via GO reduction by Geobacter promoted the NB removal process,which provided a facile strategy to alleviate the problematic nitroaromatic pollution in the environment.