Study On The Preparation Of DTC Modified Sticky Rice Starch And Its Application Of Pb(?) Chelating Adsorption

The situation of pollution and harm of heavy metals in the environment is becoming more and more serious.Among many effective methods for removing heavy metals at home and abroad,the adsorption technique has been widely used.Dithiocarbamate(DTCS)heavy metal catchers have a strong ability of chelating heavy metals,but its disadvantages of high price and no green and eco-friendly can not be ignored.Starch has the advantages of low price,easy to get,good regeneration and biodegradability.Compared with other starch,sticky rice starch has higher amylopectin content and higher molecular weight,so it is easier to absorb heavy metal ions after modification in theory.In this paper,the pollution hazards of Pb(?),a typical representative of heavy metals,were briefly described.The preparation of DTC modified sticky rice starch and its application in chelating and adsorption of Pb(?)in water were mainly explored,and then its application in municipal solid waste incineration(MSWI)fly ash is expanded.1)The natural sticky rice was purified into sticky rice starch by alkali dissolving method,and then the modified sticky rice starch was prepared by crosslinking,etherification,amination and nucleophilic addition.2)At room temperature,the optimum condition and effect of chelating adsorption of Pb(?)in water by DTC modified sticky rice starch were studied and determined by single factor experiments.The results showed that,at room temperature,in 50 mL solution with initial concentration of Pb(?)of 30 mg/L,the dosage of DTC modified sticky rice starch=0.10 g,the optimal adsorption pH=7.0,the adsorption equilibrium time=30 min,the maximum saturated adsorption amount reached 14.99 mg/g,and the chelate adsorption removal rate of Pb(?)reached 99.9%.3)The adsorption of Pb(?)in water by DTC modified sticky rice starch was studied by using the first and second order adsorption kinetics and particle diffusion models.The results showed that the process of chelating adsorption of Pb(?)by DTC modified sticky rice starch was mainly chemical adsorption,which was consistent with the quasi second-order adsorption kinetic model(R2=0.9998).4)The adsorption of Pb(?)in water by DTC modified sticky rice starch was studied by Langumir,Freundlich and Tempkin adsorption isotherm models.The results showed that the adsorption of Pb(?)in water by DTC modified sticky rice starch was favorable for both monolayer and heterogeneous adsorption,which was in good agreement with the Freundlich adsorption isotherm model(R2=0.9801).5)The Design-Expert.v8.0.6.1 software was used to analyze the process of chelating adsorption of Pb(?)in water by DTC modified sticky rice starch,the best theoretical adsorption conditions were predicted:At room temperature,in 50 mL solution with initial concentration of Pb(?)of 24.23 mg/L,the dosage of DTC modified sticky rice starch=0.09 g,pH=7.43,reaction time=24.47 min,the removal rate of chelating adsorption of Pb(?could close to 100%theoretically.6)Results showed that DTC modified sticky rice starch could be used to remove Pb(?)from MSWI fly ash.The leaching concentration of Pb(?)from MSWI fly ash in Anhui Province after 4 times of washing(0.2 mg/L)is far lower than that of the original MS WI fly ash(56 mg/L),which can meet the national safe landfill standard of MSWI fly ash(0.25 mg/L).The Pb(?)from MSWI fly ash elution to water phase is close to 100%after DTC modified sticky rice starch adsorption treatment under appropriate conditions,which can meet the discharge standard.