Modification Of Bacterial Cellulose And Its Adsorption Properties To Heavy Metal Ions And Methylene Blue

With the improvement of environmental protection requirements,printing and dyeing industry wastewater treatment requirements are also increasing.The pollution of heavy metals and methylene blue exists in printing and dyeing wastewater.It is of practical significance to study the adsorbents which can simultaneously adsorb and treat heavy metal ions and methylene blue.Bacterial cellulose is a kind of"green"adsorbent,which attracts wide attention because of its environmental friendliness.In this paper,the adsorption capacity of bacterial cellulose membrane for heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)and methylene blue in water was investigated.The adsorption process was fitted by adsorption thermodynamics and adsorption kinetics model.The changes of bacterial cellulose membrane before and after modification were characterized by FTIR,XRD and SEM,and the changes of bacterial cellulose membrane before and after modification were studied.The adsorption of heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)and methylene blue by bacterial cellulose membrane and its influencing factors were studied.The adsorption process was fitted by adsorption thermodynamics and kinetic model,and the modified bacterial cellulose membrane with good adsorption effect was selected.The mixed wastewater containing low concentration of heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)/methylene blue was treated by the optimized bacterial cellulose membrane.Adsorption treatment was carried out.The main results of the experiment are as follows:（1）when the concentration of heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)and methylene blue)is less than 400mg/L and 150mg/L,the adsorption of heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)and methylene blue by bacterial cellulose membrane can reach equilibrium with the increase of concentration.The adsorption capacity of blue increased gradually.Quasi-second-order kinetics and Langmuir adsorption isotherm model were used to simulate the adsorption process of heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)and methylene blue on bacterial cellulose membrane.The maximum adsorption capacity of heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)and methylene blue on bacterial cellulose membrane was calculated to be 13.36 mg/g,17.49 mg/g,23.03 mg/g and27.00 mg/g,respectively.（2）Compared with the original bacterial cellulose membrane modified by polyethyleneimine,the FTIR peak broadened from 900 cm^-1to 600 cm^-1,and the absorption peak appeared at 1568.123 cm^-1.Compared with the original bacterial cellulose membrane modified by polyethyleneimine,the XRD peak decreased at 22.625degrees,and the surface of the SEM film showed filaments.The optimum p H range for adsorption of heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)and methylene blue by polyethyleneimine cellulose membranes is 4-6 and 5-8,respectively,and the equilibrium can be reached at 60 minutes.When the concentration of heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)is less than 400 mg/L and the concentration of methylene blue is less than 150 mg/L,with the increase of concentration,the polyethyleneimine bacterial cellulose membranes can adsorb heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺).The adsorption capacity of methylene blue increased gradually.Quasi-second-order kinetics and Langmuir adsorption isotherm model can better fit the adsorption process of heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)and methylene blue on polyvinylimide bacterial cellulose membrane.The maximum adsorption amounts of heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)and methylene blue on polyvinylimide bacterial cellulose membrane are63.09 m/g,62.08 mg/g,69.45 mg/g and 64.81 mg/g.（3）Compared with the original bacterial cellulose membranes,the FTIR values of bacterial cellulose membranes modified by cross-linked carboxymethyl groups decreased,the peak values of 1745.712 cm^-1,1611.432 cm^-1and 1265.402 cm^-1increased significantly,and the absorption peaks of 1054.678 cm^-1appeared;the crystallinity of XRD images decreased,and the crystallization region decreased,and the peak values of SEM images did not change significantly.Change.The suitable p H range for the adsorption of heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)and methylene blue by cross-linked carboxymethyl cellulose membranes is 4-6 and 5-8,respectively,and the equilibrium can be reached when the time is 60 minutes;when the concentration of heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)is less than 400 mg/L and the concentration of methylene blue is less than 150 mg/L,the adsorption of heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)and sub-metals by cross-linked carboxymethyl cellulose membranes increases with the concentration.The adsorption capacity of methyl blue increased gradually.Quasi-second-order kinetics model and Langmuir adsorption isotherm model can better fit the adsorption process of cross-linked carboxymethyl bacterial cellulose membrane for heavy metal ions and methylene blue.The maximum adsorption capacity of cross-linked carboxymethyl cellulose membrane for heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)and methylene blue is 116.98 mg/L,118.13 mg/L,132.25 mg/g and 93.12 mg/g,respectively.（4）The maximum adsorption capacity of cross-linked carboxymethyl bacterial cellulose membrane for heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺))and methylene blue was optimized by orthogonal experiments.Langmuir adsorption isotherm model was used to calculate 76%,80%,92%and 70%of the maximum adsorption capacity for heavy metal ions(Cu²⁺or Zn²⁺or Pb²⁺)and methylene blue.（5）Cross-linked carboxymethyl bacterial cellulose membrane has better adsorption effect on low concentration of Cu²⁺/methylene blue mixed wastewater,followed by low concentration of Zn²⁺/methylene blue mixed wastewater.The application of cross-linked carboxymethyl bacterial cellulose membrane to adsorption of low concentration of heavy metal ions(Cu²⁺or Zn²⁺)/methylene blue mixed wastewater has certain potential.It is not recommended to use cross-linked carboxymethyl bacterial cellulose membrane to treat mixed wastewater containing Pb²⁺/methylene blue.