The Characterization Of Microscale And Nanoscale Bamboo Charcoals And Their Influence On Phenanthrene Sorption By Soils

Nano-technology has undergone rapid developments,and its excellent properties are attracting more attention from all walks of life.Owing to its active surface and high reaction speed,the stability of nano-material is closely linked with its surface properties.Thus,how to improve the stability of nano-material is an urgent issue in need of solution.Bamboo charcoal is a carbonaceous material,and qualified with various advantages,including porous structure,large surface area and high stability.Considering the stability of bamboo charcoal and the amazing properties nano-material,this paper chose microscale bamboo charcoal(MBC)and nanoscale bamboo charcoal(NBC)as objectives,and investigated their sorption to phenanthrene from aspects of soil type,addition rate and particle size.Besides,we have estimated the relative and absolute contribution of functional groups(carboxyl and hydroxyl)in phenanthrene sorption,enhancing our knowledge of sorption process.Based on our work,MBC and NBC had similar elemental composition(high C,low H and low N)and functional groups(carboxyl,hydroxyl etc.).However,compared to MBC,NBC had larger surface area and total pore volume.And owing to mesopores and marcopores between NBC particles,NBC could generate multilayer sorption without limitations in relatively high pressure.So,compared to MBC,NBC was more porous and had meso-and macropores,which led to a more intricate structure.XRD result showed that both MBC and NBC had graphene-similar structure but not ordered.And 13C NMR explained that NBC contained more nonpronated aromatic carbon,carbon with oxygen attachments(per cluster)and aromatic carbon(per cluster).In aqueous system,influenced by particle size,the sorption parameters of MBC and NBC were quite different.The n value of NBC was much smaller than that of MBC,indicating the stronger nonlinearity of NBC.The performance of NBC in aqueous was conspicuous and impressing.By virtue of its larger pore volume,surface area and nonprotonated aromatic carbon,the Kd(sorption coefficient)of NBC reached up to 1.24×106,almost 10 times higher than that of MBC.In comparison with some other common biochars and nano-material,the sorption ability of MBC was similar to current references.But NBC still showed a promising capacity for phenanthrene sorption.In soil-water system,the sorption of phenanthrene was impacted by soil type,addition rate and particle size.At first,brown soil form Jilin province was more capable of phenanthrene sorption than latosol from Hainan province.After addition of NBC,the difference of soil properties between brown soil and latosol was weakened,suggesting that NBC could diminish the influence of soil type to some extent.With the increase of addition rate,phenanthrene sorption was enhanced and arrived at peak of 1.0%addition.Notably,although it could aggregate and react with compounds in soil,the performance of NBC was not weakened by the complicated soil properties,and was still more capable of phenanthrene sorption than MBC,even at an extremely low addition rate 0.2%in soils.This phenomenon indicated that we could reduce the additional rate through decreasing the particle size of bamboo charcoal.Compared to other experiments about biochars addition to soils,the result of MBC addition was similar with that of current references,but soil amended with NBC still had greater ability of phenanthrene sorption.Additionally,this study blocked carboxyl and hydroxyl groups of bamboo charcoals through chemical methods(esterification and aldol condensation),and calculated their relative and absolute contributions in phenanthrene sorption based on partition-sorption model.Results suggested that blocking methods could fix corresponding functional groups without affecting other groups.The sum of relative contribution of two groups was about 10%for MBC and NBC,40%for control biochar(SBC).Although the sorption capacity of SBC was much smaller than that of MBC and NBC,the absolute contribution of functional groups for SBC was larger than that of MBC and NBC.