Adsorption Of Heavy Metal Ions And Endocrine Disruptors From Aqueous Solutions By Modified Wheat Straw

Wheat straw,as one of agricultural byproducts,can be explored as adsorbent to remove some pollutants from solution.In this paper,epichlorohydrin(ECH),citric acid(CA)and polyacrylic acid(PAA)were used as crosslinking agents and iminodiacetic acid(IDA)and β-cyclodextrin(β-CD)were used as modified agents to prepare modified wheat straw(MWS)(IDA-ECH-NWS,β-CD-CA-NWS and β-CD-PAANWS).The modified wheat straw were characterized by Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM),specific surface area analysis(BET)and X-ray photoelectron spectroscopy(XPS)and the results showed that the wheat straw were modified successfully.The adsorption capacities of wheat straw for Cu2+,Pb2+and Cd2+were 3.10 mg·g-1,4.60 mg·g-1 and 2.32 mg·g-1,respectively,but did not adsorb BPA and BPS at 303 K.While in the same experimental conditions,the adsorption capacity of IDA-ECH NWS for Cu2+was 24.2 mg·g-1,βCD-CA-NWS for Pb2+ and BPA were 94.2 mg·g-1 and 19.2 mg·g-1,β-CD-PAA-NWS for Cd2+and BPS were 77.4 mg·g-1 and 13.3 mg·g-1,respectively.The adsorption capacity of wheat straw was significantly improved after modification.The adsorption of Cu2+,Pb2+ and Cd2+ onto MWS is the best at pH 5,but the salinity has a negative effect.There was in favor of BPA and BPS adsorption at pH 7 while there was less effect with coexisting salts.In batch study,the equilibrium data were well fitted by Langmuir model and Koble-Corrigan model for the Cu2+,Pb2+ and Cd2+ adsorption and Langmuir,Temkin and Koble-Corrigan model for the BPA and BPS adsorption.For the kinetic process,the kinetic dates were well fitted Pseudo-second-order kinetic model,Elovich model and Double Constant model for Cu2+,Pb2+ and Cd2+adsorption and Elovich model and Double Constant model for BPA and BPS adsorption.In the column adsorption,the breakthrough curves were well fitted by Thomas model,Yan model and Yoon-Nelson model about all adsorbates on MWS.Thermodynamic data show that the adsorption of Cu2+,Pb2+ and Cd2+ is a spontaneous,endothermic and entropy increasing process,and the adsorption of BPA and BPS is a spontaneous,endothermic and entropy increasing process.0.1 mol·L-1 HNO3 has a better effect of desorption for Cu2+,Pb2+ or Cd2+ loaded adsorbents,and ethanol has a better desorption for BPA and BPS loaded adsorbents,indicating that modified wheat straw has the ability of recycling.Modified wheat straw is potential to remove heavy metal ions and some organic pollutants from solution.