Preparation And Adsorption Properties Of Thiosemicarbazide Modification Of Microfibrillated Cellulose

Nowadays,global industrialization and scientific research have provided tremendous impetus to social progress,but at the same time it has brought unprecedented challenges to human society.The wastewater which is discharged from industrial production processes contains a large amount of heavy metals or metalloid ions will cause damage to the environment and ecology and bring unimaginable risks to human health when it flows into nature.Therefore,research on wastewater treatment technology with high efficiency and low cost has become a hot issue of widespread concern in the society.As a relatively new technology for removing heavy metal ions,the adsorption method has become the most commonly used method for heavy metal ion treatment in wastewater because of the advantages of low pollution,high efficiency,simple operation flow,low cost and convenient regeneration treatment.Cellulose-based adsorbents are favored by more and more scholars because of their high specific surface area,good physical properties,biodegradability and wide range of sources.In this paper,a high-efficiency,specific and recyclable cellulose-based adsorbent prepared from microfibrillated cellulose was manufactured and applied to the adsorption of mercury ions,and explore its adsorption properties for mercury ions and other metal ions.First,the laboratory-prepared bleached palm cellulose?BPC?was subjected to alkali pretreatment,followed by mechanical treatment to obtain microfibrillated cellulose?MFC?.The prepared MFC is oxidized by using sodium periodate to obtain cellulose?DAMC?with a structure corresponding C₂/C₃ dialdehyde.Then,the thiosemicarbazide is grafted onto DAMC through a Schiff base reaction to manufacture cellulose?TSMC?which have thiosemicarbazide reactive functional groups.The properties of the samples were characterized by FT-IR,XRD,XPS,TGA,elemental analysis and SEM.The effects of different reaction conditions on the yield of the reaction products and the content of reactive functional groups were investigated.The results of FT-IR showed that the functional groups of the cellulose structure after alkali pretreatment and mechanical treatment did not change significantly.After oxidation by sodium periodate,DAMC successfully formed aldehyde groups,and TSMC successfully grafted thiosemicarbazide after modification with thiosemicarbazide.The XRD results show that the cellulose sample maintain the crystal structure of cellulose-I throughout the reaction,but the crystallinity is gradually reduced.The TGA results show that the thermal stability of cellulose after alkali pretreatment,mechanical treatment and oxidation reaction is gradually reduced,which confirms the XRD results.XPS results showed that new nitrogen and sulfur absorption peaks appeared on TSMC,which further confirmed the successful grafting of thiosemicarbazide onto TSMC.The SEM results show that sodium periodate can degrade cellulose during the oxidation reaction,and the higher the amount,the higher the degree of degradation.At the same time,increasing the amount of sodium periodate,prolonging the reaction time and increasing the reaction temperature during the reaction can increase the aldehyde group content of DAMC,but the yield also decreases.When the reaction conditions were sodium periodate 6 mmol/g with a reaction time 6 h and reaction temperature 40?,the yield of DAMC was 89.6%,and the aldehyde group content was 94.6%.Increasing the amount of thiosemicarbazide can increase the amino content of TSMC.The prepared TSMC was used as an adsorbent for Hg?II?ions and other metal ions.The adsorption properties of TSMC for heavy metal ions were studied and the adsorption kinetics and adsorption isotherms of the adsorption process were analyzed.The results show that higher solution concentration,longer adsorption time and appropriate higher pH under acidic conditions can each increase the adsorption capacity of TSMC for Hg?II?ions.The adsorption process of Hg?II?ions by TSMC has a best fit with the kinetic pseudo-second-order equation and the Langmuir adsorption isotherm model,and the maximum adsorption capacity reaches331.13mg/g..The results of selective adsorption showed that the adsorption selectivity of TSMC for Hg?II?ions was more than 50 times that of other metal ions,which indicated that TSMC has relatively high adsorption specificity for Hg?II?ions.Finally,IIP-TSMC was obtained by Hg?II?ion-imprinting treatment on TSMC,and the crystal structure of cellulose and the adsorption performance of metal ions were studied.The results showed that the crystal structure of cellulose did not change after ion-imprinting treatment,and the adsorption capacity for Hg?II?ions decreased by about 10%,but the adsorption specificity was enhanced.