Preparation And Modification Of Polysulfide Polymers And Its Adsorption Properties For Hg (Ⅱ) In Water

Heavy metal pollution has become a global environmental problem,and mercury pollution is particularly serious,which poses a great threat to the ecological environment.Mercury is easily absorbed,concentrated and enriched by biological ingestion,and can also be enlarged step by step through the food chain to the extent of harming human health.Therefore,the treatment of mercury pollution in the water environment has become an important research topic for researchers.In this work,the polysulfide polymer material Waste Oil Polysulfide（WO-Polysulfide）was prepared by reverse vulcanization synthesis.By changing the type or proportion of porogen,porous sulfur-based polymer material Porous Polysulfide（Po-Polysulfide）and Composite Polysulfide（Com-polysulfide）were prepared.Using SEM（EDS）,FT-IR,XPS,TGA/DSC,Laser Particle Size Analysis and other characterization methods to analyze the morphology,structure and properties of the polysulfide polymers and raw materials.Then it was applied to the study of Hg（Ⅱ）adsorption performance in water,showing good adsorption capacity.The main research content and results of this research are as follows:（1）The Hg（Ⅱ）polymer adsorbent synthesized here is a polysulfide polymer.At high temperatures,elemental sulfur（S₈）is ring-opened and polymerized with waste vegetable oil to produce multipolymers,where the sulfur content can reach19.20%.Thermogravimetric analysis shows that WO-Polysulfide material decomposes only above 200°C,and is thermally stable.Adding sodium chloride during the reverse vulcanization process to obtain Po-Polysulfide material,the specific surface area of which is larger than WO-Polysulfide,the particle size is reduced,and the adsorption efficiency is improved.Adjusting the ratio of porogen sodium citrate and sodium chloride to prepare Com-polysulfide material,the adsorption efficiency of Hg（Ⅱ）can reach more than 99%.（2）Under acidic conditions（pH=2.0）,the adsorption rate of WO-Polysulfide to Hg（Ⅱ）solution with an initial concentration of 4.0 mg L^-1 was 98.87%;saturated adsorption was achieved under the initial Hg（Ⅱ）concentration of 150 mg L^-1 and 1.0g WO-Polysulfide adsorbent,with a maximum adsorption capacity of 7.40 mg g¹.Interfering ions Ca²⁺,Mg²⁺,SO₄^2-,NO₃^-,etc.have little effect on the adsorption of Hg（Ⅱ）,but CO₃^2-,HCO₃^-,SiO₃^2-changed the pH value of the system due to hydrolysis,inhibiting Hg（Ⅱ）adsorption.（3）The adsorption efficiency of Po-Polysulfide to Hg（Ⅱ）solution with pH 2.0and initial concentration of 50 mg L^-1 was 99.57%.The maximum adsorption capacity is 8.23 mg g^-1 when saturated adsorption is achieved under the condition of 1.0 g adsorbent and 200 mg L^-1 Hg（Ⅱ）initial solution.In the ion interference experiment,Ca²⁺,Mg²⁺,SO₄^2-,NO₃^-had little effect on the adsorption of Hg（Ⅱ）,and CO₃^2-,HCO₃^-,SiO₃^2-ions had an inhibitory effect on Hg（Ⅱ）adsorption.（4）Under strong acid conditions（pH=1.0）,Com-polysulfide can exist stably without dissolution,and the adsorption efficiency for the initial concentration of 50 mg L^-1 Hg（Ⅱ）solution is 99.78%;When 1.0 g of adsorbent material reaches saturated adsorption of Hg（Ⅱ）solution with initial concentration of 200 mg L_-1,the maximum adsorption capacity is 8.33 mg g^-1.In the dynamic adsorption experiment,the adsorption behavior of the Com-Polysulfide adsorption column conforms to the Thomas dynamic adsorption model.（5）The above adsorption of Hg（Ⅱ）is an endothermic,spontaneous,and entropy-increasing reaction,which is consistent with the Langmuir isotherm adsorption model and quasi-second-order kinetic model,indicating that the adsorption reaction of polysulfide polymer to Hg（Ⅱ）is homogeneous single layer adsorption,mainly based on chemical adsorption.The polysulfide polymer not only has a good effect of removing Hg（Ⅱ）,but also has a simple synthesis method.This material can be mass-produced and has good industrial application prospects.