Removal Of Disinfection Byproducts By Graphene-Silica Composite

Graphene-silica was successfully synthesized by a simple hydrothermal method.This composite was used for researching the adsorption properties on humic acid and disinfection byproducts precursors in natural surface water.The effects of the amount of adsorbent,initial concentration,pH,ionic strength on the adsorption process were discussed,and the adsorption mechanism was figured out.Different characterization methods showed that silica particles were uniformly dispersed on the graphene plane.The stretching vibration of Si-O-Si and Si-OH could be distinguished obviously.The existence of silica could effectively reduce the stack of graphene layers.Compared with graphene,the specific surface area of graphene-silica increased 31.2 % to259.43 m2/g.The adsorption of humic acid by graphene-silica showed that the optimum amount of adsorbent was 300 mg/L.About 60 minutes could reach the adsorption equilibrium and,the first 10 minutes was quick adsorption phase,the adsorption efficiency was about 56 %.The factor of pH had significant effect on the adsorption,with the increase of pH,the adsorption efficiency decreased.With the increase of initial concentration of humic acid,the efficiency decreased,but the adsorption quantity increased,when the concentration was more than 300mg/L,the adsorption quantity remained constant.With the increase of ionic strength,the efficiency increased.The efficiency of adsorption of humic acid onto graphene-silica remained at about 58 % after repeatly used several times.Pseudo-second-order kinetic model,intraparticle diffusion model and Langmuir isotherm model described the adsorption behavior of humic acid on graphene-silica well,which indicated that the adsorption was mainly chemisorption and monolayer adsorption.Hydrogen bonds,?-? interactions and electrostatic interactions might be responsible for the adsorption of humic acid on graphene-silica.The research of disinfection byproducts precursors controlled by graphene-silica revealed that the efficiency of natural organic matter in natural surface water adsorbed onto graphene-silica increased with the increasing amount of adsorbent.The higher the pH,the lower the adsorption efficiency.The optimal adsorbent was prepared during the mass ratio of graphene and silica was 1:10.Moreover,the existence of bromide ion had an important influence on the adsorption as it increased the concentration of brominated disinfection byproducts,decreased the concentration of chlorinated disinfection byproducts.The removal efficiency of brominated disinfection byproducts precursors adsorbed onto graphene-silica was higher than chlorinated disinfection byproducts precursors.graphene-silica had a good adsorption performance for natural organic matter in different natural surface water samples.The removal rate of haloacetic acid formation potential was higher than trihalomethane formation potential,the removal rate of chloral formation potential was relatively good,but the removal rate of trichloroacetonitrile formation potential was about zero,which showed that graphene-silica was more effective on the removal of hydrophobic compounds,whereas hydrophilic and nitrogenous compounds were inefficient.The performance of disinfection byproducts precursors in natural surface water adsorbed onto graphene-silica was superior to graphene and silica.The adsorbent could be repeatedly used in the subsequently adsorption–regeneration cycles with little loss of disinfection byproducts precursors' removal efficiency.graphene-silica has the potential for using as an effictive adsorbent to control disinfection byproducts precursors.