The Preparation Of Modified Silica Gel Composite Materials And Its Adsorption Properties Of Heavy Metals

Heavy metal ions is a type of highly toxic pollutants.It poses a serious threat to human health.Therefore,it is particularly important to design and synthesis highperformance materials that can efficiently remove the heavy metal ions.Silica gel with high mechanical strength,large specific surface and easy modificability often used as a substrate material.The novel silica gel composites are synthesized by conjugating functional groups or compounding with graphene oxide,the adsorption properties of the materials to Hg2+ were investigated as well.Silica-gel adsorbents modified by the dithiocarbamater is successfully designed and sythesized,and the adsorption of Hg2+ from aqueous solution are also studied.The maximum adsorption capacity for Hg2+ is up to 113 mg/g at 25 ?,which shows excellently selective adsorption for Hg2+.The process of SG-PDC for adsorbing Hg2+ conform to pseudo-second-order equation and Langmuir model,and the calculated values of the thermodynamic parameters indicate that this adsorption process is a spontaneous and endothermic reaction.According to the mechanism analysis,the improvement in mercury adsorption is attributed to the anchored N and S function groups of the modified silica gel surface.After several adsorption-desorption cycles,the adsorption rates of SGPDC also remained above 80% to show their good reproducibility.This study uses a one-step method to prepare Polyamino motified silica-graphene composites hydrogel(SG-NH2-r GH,SG-TETA-r GH,SG-PEI-r GH).A great quantity of nitrogen functional groups are loaded in the surface of SG-PEI-r GH,and a large number of oxygen functional groups are anchored on the surface of r GH.Therefore,Hg2+ can be efficiently removed by SG-PEI-r GH.The saturated adsorption capacity of SG-PEI-r GH for Hg2+ is 265.9 mg/g.Meanwhile,the absorpition efficiency can still reach 75% after many recycled times showing high recoverability and good separability.It resolves the problem that it is difficult to be recycled and regenerated for the most adsorbents in practical applications.