Preparation Of Two Kinds Of Modified Japonica Porous Starch And Their Application In Heavy Metal Wastewater Treatment

Porous starch is a kind of modified starch,which has many advantages such as absorbability,wide source of raw materials,innocuity,environmental protection.In this paper,the porous starch from Ningxia Japonica Rice was prepared by enzymatic method,and then the porous starch from Japonica Rice was used as raw material,Amino Porous Starch(APS)and Porous Starch Xanthate(PSX)were synthesized by polyethylenimine and carbon disulfide,respectively,and the adsorption of copper and lead ions in the wastewater were studied.The main contents and results are as follows:(1)The porous rice starch was prepared from Ningxia Japonica Rice Starch.The optimum technological conditions were as follows:temperature 40?,reaction time 14 h,enzyme content 3.5%,pH 4.0,ultrasonic time 20 min,ultrasonic power 400 w The Scanning electron microscope shows that the porous starch has more holes and better pore-forming effect The specific volume and water absorption of porous rice starch prepared under this reaction condition were 0.457 g/mL and 97.5%,respectively,which were 3 6.4%and 41.9%higher than the original rice starch.(2)APS and PSX were synthesized.The optimum technological conditions of synthesizing APS were as follows:rotating speed 200 r/min,reaction time 6 h,concentration of Polyethylenimine 0.10 mg/L,reaction temperature 50?;the optimum technological conditions of synthesizing PSX were as follows:stirring time 3 h,dosage of carbon disulfide 2.0 mL,dosage of sodium hydroxide 20 mL,temperature 30?.The structural characterization of APS and PSX by Fourier infrared spectroscopy showed that the porous starch of Japonica Rice was successfully grafted with xanthate and Amino groups respectively.(3)Cu2+and Pb2+ were removed from wastewater by APS and PSX.The results showed that the optimum technological conditions of removing Cu2+by APS were pH 7,time 120 min,temperature 45?,amount of adsorbent 160 mg/L;the optimum technological conditions of removing Cu2+ by PSX were pH 6,time 30 min,temperature 25?,amount of adsorbent 100 mg/L;the optimum technological conditions of removing Pb2+ by APS were pH 5,time 60 min,temperature 35?,amount of adsorbent 1.2 g/L;the optimum technological conditions of removing Pb2+ by PSX were pH 5,time 30 min,temperature 35?,amount of adsorbent 1.8 g/L.(4)The adsorption processes of APS and PSX on Cu2+ and Pb2+ were described through adsorption kinetics and thermodynamics.The results showed that the adsorption of APS and PSX on Cu2+ and Pb2+was more fit to the second-order kinetics law.The adsorption of Cu2+ by APS and PSX was more consistent with Freundlich model of multilayer adsorption,and both of them were preferential adsorption.The adsorption of Pb2+ on APS and PSX was more consistent with Langmuir model of monolayer adsorption,and the adsorption properties of APS and PSX were evaluated by using Langmuir model RL.Both APS and PSX had good adsorption properties,which were beneficial to the adsorption of Pb2+.The maximum adsorption capacity of APS for Cu2+ was 67.2948 mg/g,which was 60.30%lower than that of PSX.The maximum adsorption capacity of PSX for Pb2+ was 212.7660 mg/g,which was 19.15%higher than that of APS.It can be concluded that the maximum adsorption capacity of PSX for Cu2+ and Pb2+is greater than that of APS,and the maximum adsorption capacity of both adsorbents for Pb2+ is greater than that of Cu2+.