Preparation And Properties Of Thiourea Functional Group Modified SPVA And SPVA/BC Composites

With the development of industrialization,the heavy metal wastewater from it enters into the ecosystem and causes serious environmental pollution.Therefore,efficient recovery and recycling of heavy metal ions in water system is of great practical significance to the ecological environment.In this study,Thiosemicarbazide(TSC)modified crosslinked polyvinyl alcohol adsorbent(TSC-SPVA)and Guanylthiourea(GLA)modified cross-inked polyvinyl alcohol/bacterial cellulose composite adsorbent(GLA-SPVA/BC)were prepared,and the selective adsorption of copper ions by the two adsorbents was studied.TSC-SPVA adsorbent is prepared by using polyvinyl alcohol(PVA)as raw material.SPVA was formed by cross-linked polyvinyl alcohol,and then graft-modified with thiosemicarbazide to prepare a white powder sorbent named TSC-SPVA.The material SPVA and TSC-SPVA were investigated by single factor and orthogonal experiments respectively,and the better synthesis conditions were finally obtained.The equilibrium state,kinetics and selectivity of adsorption were studied by batch experiments,and the effect of p H value on adsorption was also studied.Through SEM/EDS-Mapping,Fourier transform infrared spectroscopy(FT-IR)and Raman spectroscopy(Raman),thermogravimetric differential scanning calorimetry(TG-DSC)and other characterization methods,the material properties,morphology and composition.After analysis,these characterization methods confirmed the structure of the material and the corresponding adsorption mechanism.Adsorption thermodynamic experiments show that the adsorption of Cu(?)ions by the adsorbent TSC-SPVA conforms to the Langmuir isotherm model,and the maximum adsorption capacity is 82.36 mg·g^-1.The kinetic data showed that the adsorption of Cu(?)ions on the adsorbent TSC-SPVA conformed to the Elovich kinetic model.The adsorbent TSC-SPVA shows obvious selectivity for Cu(?)ions in the presence of Cu(?),Pb(?),Zn(?),and Ni(?)ions,almost being three times the adsorption capacity of lead,zinc and nickel ions.GLA-SPVA/BC adsorbent is based on polyvinyl alcohol(PVA),mixed with bacterial cellulose(BC)emulsion at a ratio of V_PVA:BC=4:1,and crosslinked to form SPVA/BC,and then it was prepared by graft-modifiedg with guanylthiourea.By comparison,it was found that the adsorption effect of the graft modified GLA-SPVA/BC adsorbent was nearly twice as high as that of the unmodified SPVA/BC adsorbent.In the EDS-Mapping image,the change of S,N and Cu(?)ions of the adsorbant GLA-SPVA/BC before and after adsorption could be observed,and FT-IR and Raman spectroscopy can also prove the successful graft of guanylthiourea.TG-DSC shows that the material has good thermal stability and the addition of bacterial cellulose further improves the thermal stability.Batch adsorption experimental study show that the adsorbent GLA-SPVA/BC to Cu(?)ions adsorption conforms to the Langmuir isotherm model,and the maximum adsorption capacity was 91.86 mg·g^-1.Elovich kinetic model showed that chemisorption occurred on the surface of the adsorbent.The selective adsorption experiments show that the GLA-SPVA/BC adsorbent exhibits high selectivity.The results show that the preparation of thiourea-based composite adsorbents using polyvinyl alcohol(PVA)as a raw material has good application prospects.