Adsorption Of Heavy Metals And Organic Carbon In Water By Composite Adsorbent Materials

With the rapid development of industrialization,arbitrary discharge of industrial waste water is a great threat to the ecological environment and human health,especially heavy metal pollution and organic carbon pollution is focused on the current industrial wastewater treatment.In recent years,biosorbents have attracted the attention of domestic and foreign scholars in the field of heavy metal treatment by virtue of their advantages such as wide source,low cost and simple post-processing.The adsorption effect of biosorbents was greatly improved on heavy metals by the academic modified-research.High oil absorption resin is often used in oily wastewater treatment because of its high oil absorption speed,good oil retention effect and strong oil water selectivity.In this paper,the adsorption of heavy metals and organic carbon was studied by different composite adsorbents.Ammoniated magnetic taro stalk adsorbent(MATA)and carboxymethylated magnetic taro stalk adsorbent(MCTA)were designed and synthesized.Adsorbents were analyzed by scanning electron microscopy(SEM),specific surface area and Fourier transform infrared spectroscopy(FT-IR).The effects of pH value,adsorption time,initial concentration of heavy metals,amount of adsorbent and temperature on the adsorption of Ni2+ and Cu2+ on MATA were studied.For the adsorption of organic carbon,the effects of temperature and flow rate on the dynamic adsorption of three polystyrene acrylate copolymers were studied,and the related mathematical models were established.(1)Ammoniated taro stalk adsorbent(ATA)and carboxymethylated taro stalk adsorbent(CTA)were obtained by the modification of taro stalk powder with ethylenediamine and citric acid,then the modified materials were magnetized,and ammoniated magnetic taro stalk adsorbent and carboxymethylated magnetic taro stalk adsorbent were obtained.The unmodified TA and modified MATA and MCTA were characterized by scanning electron microscopy,specific surface area and Fourier transform infrared spectroscopy.The results showed that TA was rich in fibrous structure,and modified MATA was loose spherical structure,and modified MCTA was block structure.Compared with specific surface area and oil absorption effect,MATA and MCTA decreased the specific surface area of TA,but the adsorption capacity increased,so the adsorption of heavy metals on two kinds of magnetic adsorbents is mainly chemical adsorption.From FT-IR analysis,the amino and carboxyl peaks of MATA and MCTA increased,indicating that the surface functional group of modified adsorbents did not decrease,but increased.Comparing the adsorption capacity of Ni2+and Cu2+ by TA,ATA,CTA,MATA and MCTA,the adsorption effect of MATA was the best for Ni2+ and Cu2+ adsorption.(2)The changes of Ni2+ and Cu2+ adsorption capacity of MATA materials with various factors were studied.The optimum adsorption conditions of Ni2+ onto MATA was achieved at the pH of 7.5,the adsorption time of 6 h,the dosage of 0.8 g,the initial concentration of 400 mg/L.The optimum adsorption condition of Cu2+ onto MATA was the pH of 5.5,the adsorption time of 12 h,the amount of adsorbent of 0.8 g and the initial concentration of 400 mg/L.Through the analysis of the dynamic and thermodynamic,the adsorption process of MATA on Ni2+ and Cu2+,they satisfy the quasi dynamics kinetically,and satisfies both the Langmuir isotherm model and the Freundlich adsorption isotherm.The maximum adsorption capacity of Ni2+ is 44.84 mg/L,and the maximum adsorption capacity of Cu2+ is 47.39 mg/L.In addition,by calculating the Gibbs free energy of the thermodynamic adsorption process of MATA on Ni2+ and Cu2+,it is shown that the two adsorption processes are a spontaneous process.(3)Three porous polystyrenes material of polystyrene-methyl acrylate(St-MMA),polystyrene-butyl acrylate(St-BMA),polystyrene-octadecyl acrylate(St-OMA),their dynamic adsorption was investigated to organic carbon.From the results of SEM,BET and FT-IR,the pores are rich,with micropores and mesoporous structures.From the results of static adsorption,it can be seen that the lipophilicity of styrene-acrylate copolymer porous material is better than that of hydrophilicity,and the effect of St-OMA oil absorption is the best.From curves of dynamic adsorption capacity versus temperature,the curves of three materials are the first to rise and fall.The relationship between the dynamic adsorption capacity of porous materials and the solution temperature is in agreement with the Lorentz distribution,and the correlation of the fitting data is over 0.96,and the optimum adsorption temperature of the three materials is:41?,46?,46?.From curves of dynamic adsorption capacity with the flow rate,the curves of three materials showed a rapid increase and decreased slowly.The relationship between the dynamic adsorption capacity and the flow rate of the porous material was the logarithmic distribution,and the correlation of the fitting data is over 0.96.The best adsorption flow rates of St-MMA,St-BMA and St-OMA were 0.15 L/min,0.15 L/min and 0.16 L/min,respectively.