| With the rapid development of modern's economy,a large number of industrial wastewater containing heavy metals not in accordance have been discharged into the water,resulting in the situation of heavy metal pollution of water increasingly serious.Heavy metals in the water is toxic and not easy to be degraded,it can ultimately into the human body through the food chain enrichment.And then it can cause the injury and pathological changes of various organs when the accumulation of copper in the human body over a long time.Therefore,how to effectively control the heavy metal wastewater has become a hot topic in the research of water treatment.Adsorption method is a simple,low cost,good effect of the treatment of heavy metals in water.Pectin has a large number of-OH radicals,have chelating ability for metal ions.Pectin binding with magnetic material has high absorption capacity,which make it easier for pectin to separated from solution after the adsorption,so it is a kind of green economy adsorbent for heavy metal removal.Therefore,this paper uses pectin and magnetic Fe3O4 to prepare a material,and modify pectin with methods of hydroxyl,calcium chloride crosslinking.The prepared modified pectin microspheres adsorption materials are used to remove heavy metals from water and shellfish tissues,compared with unmodified material,the effect is better.In this paper,two kinds of modified Fe3O4-pectin adsorbent were prepared by using pectin as raw material,and the pectin was first saponified by NaOH,and then the graft copolymerization of acrylamide and epoxy chloropropane on pectin was carried out respectively,mixing this pectin with nano Fe3O4articles.Two adsorbents were prepareded,and the adsorbent has strong magnetic and chemical stability to adsorb copper ions.The structural characterization of the two adsorbents was carried out by means of modern instrumental analysis.And effects on the adsorption was studied by the factors such as the adsorption time,the initial concentration,the temperature,the adsorbent dosage and solution pH.The main conclusions were shown as follows:(1)The samples were characterized by Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM)and X-ray powder diffraction(XRD).The results showed that pectin was successfully modified,Scanning electron microscopy results show that the magnetic particles are irregular and scattered,acrylamide modified Fe3O4-pectin magnetic microspheres with an average diameter of 3.2 ?m,and the epoxy chloropropane was 2.8 ?m.XRD analysis results showed that the peak positions of the modified Fe3O4-pectin magnetic microspheres and Fe3O4 two were the same,basically no change,illustrate the spinel structure of Fe3O4 nanoparticles did not change in the process of modified pectin coated Fe3O4.(2)The effects of adsorption time,pH,temperature,initial concentration of Cu2+ d the amount of adsorbent on-Fe3O4 removal rate of two kinds of modified pectin were studied.The orthogonal experimental results showed that the adsorption effect was best when the solution volume was 10 mL,adsorption time of acrylamide modified adsorbent was 120 min,pH was 7,adsorption temperature was 30?,initial concentration of Cu2+solution was 200 mg/L,and the amount of adsorbent was 20 mg,the unit adsorption capacity reached 86.99 mg/g;adsorption time of epoxy chloropropane modified adsorbent was 90 min,pH was 7,adsorption temperature was 60?,initial concentration of Cu2+solution was 160 mg/L,and the amount of adsorbent was 20 mg,the adsorption capacity reached 74.89 mg/g.And the two Adsorbents removal rate reached 90?99%.(3)The study of adsorption kinetics and thermodynamics of acrylamide modified Fe3O4-pectin magnetic microspheres and epoxy chloropropane modified Fe3O4-pectin magnetic microspheres showed that adsorption of two kinds of modified adsorbent on Cu2+reached equilibrium after 200-400 min.Sorption equilibrium studies indicated that the bio-sorption obeyed Langrnuir isotherm model,the saturated adsorption capacity of the two adsorbents reached 136.36 mg/g and 142.85 mg/g.The adsorption process between the modified pectin and Cu2+was in line with pseudo secondary dynamics equations,the correlation coefficient R2was above 0.99.It indicated that the adsorption process was mainly controlled by chemical adsorption,while the surface adsorption also existed.We speculate that the main mechanism was ion exchange.(4)At the desorption experiment,the adsorbents were desorbed by 0.1 mol/L EDTA,and the desorption rate was 95.3?96.5%.The adsorbents were regenerated by EDTA after desorption and the adsorption capacity decreased little,which indicated that the modified pectin magnetic microspheres had good regeneration ability.(5)The copper ions in Enzymatic solution of Conch,Neptunea cumingi and the green willow clams were adsorbed with the adsorbent,the removal rate of copper ions was about 80?85%.The result was satisfactory. |
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