Fabrication Of Functionalized 3D Bi-continuous Cubic Silica-based Materials And The Removal Of As(?),Pb(?),Cr(?)

In this paper,three kinds of functionalized silica composite adsorbents were successfully synthesized by organic and inorganic modification.The structure and properties of the adsorbent materials were investigated and analyzed by a series of characterization methods.The adsorption behavior of heavy metal ions As?III?,Pb?II?,Cr?VI?in single system and multi-system was further investigated.The specific experiments are as follows:Three-dimensional mesoporous KIT-6 with large specific surface area was prepared using tetraethyl orthosilicate as the silicon source and triblock copolymer P123 as the template.Silica-based materials loaded iron compounds were prepared with impregnation method.FeCl3·6H2O was firstly loaded onto KIT-6 and then MnSO4 and KMnO4 were further loaded to obtain the final odsorbent which was abbreviated as MnO2/FeOOH/KIT-6.N2 adsorption-desorption,XRD,TEM,FT-IR and XPS indicated that the adsorbent was successfully synthesized.The maximum adsorption capacity of MnO2/FeOOH/KIT-6 for As?III?can reach 39.77 mg·g^-1 at pH 1 and the pseudo-second-order kinetic model and Langmuir model were fitted better for the adsorption process.The adsorption mechanism of MnO2/FeOOH/KIT-6 for As?III?may be electrostatic attraction berween M-OH functional groups and As?V?as well as chelation reaction between M-OH,MnO2and As?III?.In addition,the adsorbent has good reusability and practicability after five cycles experiments.Sodium silicate as the silicon source,chitosan solution was added in the process of hydrolysis of sodium silicate.And the immobilization of chitosan was realized through the reaction between aldehyde group of glutaraldehyde and-NH2of chitosan by adding the glutaraldehyde.After hydrothermal reaction,the CS/KIT-6 was obtained by one-pot method.Then,thiosemicarbazide was further grafted into the CS/KIT-6 using glutaraldehyde as crosslinking agent.We obtained the final odsorbent which was abbreviated as m2TSC-VGA@m1CS/KIT-6.N2adsorption-desorption,XRD,SEM,elemental analysis,FT-IR and XPS indicated that the adsorbent was successfully synthesized.The results of adsorption experimentindicatedthatthemaximumadsorptioncapacityof1.0TSC-5.0GA@0.5CS/KIT-6 for Cr?VI?could reach 188.30 mg·g^-1 at pH 3 and the process of adsorption fitted better to the Langmuir model.The kinetic experiments showed that the adsorption conformed to the pseudo-second-order kinetic model.The adsorption mechanism of the adsorbent was the chelation reaction between nitrogen,sulfur-containing group and Cr?VI?.The results of selective adsorption experiment indicated that 1.0TSC-5.0GA@0.5CS/KIT-6 can effectively separate Cr?VI?from solutions containing Cr?VI?,Cu?II?,Ni?II?,Cd?II?and Zn?II?at pH 2?SelCr/M>1.5?,while it could also adsorb Cu?II?at pH 3⁵?SelCr/Cu<1.5?.Finally,the results of elution cycle experimental showed that the1.0TSC-5.0GA@0.5CS/KIT-6 has good stability and reusability.Sodium silicate as the silicon source,chitosan solution was added in the process of hydrolysis of sodium silicate.And the immobilization of chitosan was realized through the reaction between aldehyde group of glutaraldehyde and-NH2of chitosan by adding the glutaraldehyde.After hydrothermal reaction,the CS/KIT-6 was obtained by one-pot method.Then,polyethyleneimine was further grafted into the CS/KIT-6 using epichlorohydrin as crosslinking agent by microwave-assisted method.We obtained the final odsorbent which was abbreviated as 0.2gPEI-T1/t1-CS/KIT-6-T2/t2.The adsorbent was characterized by N2 adsorption-desorption,XRD,TEM,FT-IR,elemental analysis and XPS.The maximum adsorption capacity of 0.2gPEI-50/20-CS/KIT-6-115/15 were observed to be 248.49 mg·g^-1 for Pb?II?at pH 6 and 225.89 mg·g^-1 for Cr?VI?at pH 5,respectively.In addition,the adsorption behavior for Pb?II?and Cr?VI?obeyed the Langmuir model and pseudo-second-order dynamic model.The results of selective adsorption experiment indicated that 0.2gPEI-50/20-CS/KIT-6-115/15 can effectively separate Pb?II?from solutions containing Pb?II?,Cr?III?,Cd?II?and Mg?II?at pH 4⁶?Sel Pb/M>1.5?and separate Cr?VI?from solutions containing Cr?VI?,Cd?III?,Zn?II?and Ni?II?at pH 2⁵?SelCr/M>1.5?.However,0.2gPEI-50/20-CS/KIT-6-115/15 had a certain adsorption capacity for Cu?II??SelM/Cu<1.5?.The adsorption mechanisms of Pb?II?and Cr?VI?could be attributed to the coordination between nitrogen-containing group and Pb?II?,Cr?VI?and positive and negative charge attraction between-NH3⁺and oxyanions of Cr?VI?.Moreover,the adsorbent showed better stability and reutilization performance after six-cycles adsorption elution experiment.