Study On The Adsorption Of Endocrine Disrupting Chemical Bisphenol A In Water On Activated Carbons With Various Modification

Endocrine disrupting chemicals(EDCs)are exogenous substances or mixtures that alter function(s)of the endocrine system and consequently cause adverse health effects on an intact organism,its progeny or(sub)populations even at low doses.This emerging pollution has caused great attention of public.Among EDCs,bisphenol A-(BPA)served as an important chemical raw material was widely applied,And the pollution of this chemical is very serious woldwide,which make it become a representative pollutant of endocrine disruptors.Therefore this study applied bisphenol A(BPA)as the main pollutants.The adsorption of organic contaminants by activated carbons is the most effective and widely used methods to purify water.Activated carbon has characteristics of high specific surface area,and stable chemical properties,which is generally considered to be one of the most adsorptive material appling in the advanced treatment of wastewater.However,the commercial activated carbons are mainly used to removal common pollutants,less for new endocrine pollutant removal.Therefore,this paper studies two commercial activated carbons and activated carbons modified by different approaches,explored the behavior and capacity of BPA absorpted on different activated carbons.The results of this work can provide theoretical guidance for practical use.Two activated carbons,F6(coal-based)and OLC(wood-based),were selected in this study.The activated carbons with different surface physical and chemical properties were obtained by method of N2 outgassing heat treatment,HCl treatment or NaOH treatment.Adsorption behavior and adsorption capacity of BPA were analyzed by adsorption kinetics experiments and adsorption isotherm experiments.And the adsorption mechanism was discussed.On this basis,the effects of operated temperature,solution pH and ionic strength on the adsorption of bisphenol A onto two original carbon samples were explored.The experimental results show that the textural and chemical characteristics of the activated carbons were changed by modification.The N2 outgassing treatment increased the specific surface areas of activated carbon,but decreased the total acidity of activated carbon.As a result,the pHpzc values of the two original carbons was increased.However,HCl treatment and Na OH treatment resulted in slight change in the BET surface area,where the former increased the total acidity of activated carbon but reduced the pHpzc,while the latter was contrary to it.Kinetic experiments showed that the adsorption of activated carbon on BPA followed a pseudo-second order kinetic model.The isothermal experiments further indicated that the adsorption of BPA on activated carbons followed Langmuir adsorption.The modified activated carbons showed better adsorption capacity.The HCl modified sample(F6-A and OLC-A)presented the best adsorption capacity,and the equilibrium adsorbances reached 347.22 and 234.19 mg/g,respectively.The N2 outgassing treatment modified activated carbon obtained lower capacity,and the NaOH treatment had the worst adsorption ability.The analyzing results of mechanism indicated that the adsorption of bisphenol A on carbons mainly followed π-π dispersion interaction.There is a π-π dispersion force between the surface of the activated carbon graphite layer electrons and BPA aromatic electron.Activated carbon pHpzc determines the surface charge amount,When the pHpzc of activated carbon was close to adsorption system pH,the stronger π-π dispersion interaction between the surface of the activated carbon and molecular BPA,the better adsorption ability.The two original carbons were choosed to examine the effects of operated temperature,solution pH and ionic strength on the adsorption of bisphenol A.The adsorption capacity of activated carbon to BPA decreased with the increase of temperature.The thermodynamic parameters showed that the adsorption process was spontaneous and exothermic.The adsorption capacity of activated carbon to BPA was obviously affected by the solution pH which determines the charge of both the carbon and the adsorbate.The sample F6 and OLC represented the high adsorbance at pH =8,which attributed to the enhanced π-π dispersion interaction.Activated carbon and ionic state BPA generate electrostatic repulsion force at pH =11 leading to the worst capacities.In addition,the presence of NaCl(0.01M)in solution caused a salting-out effect via decreasing the solubility of BPA,thereby enhancing its adsorption on activated carbon.When the NaCl concentration was above 0.01 M,the adsorption capacity decreased slightly due to the competition adsorption of NaCl and BPA for the adsorption sites on activated carbons.