| The pollution of heavy metal ions and the waste of biomass resources are one of the most serious environmental safety problems faced by countries all over the world.How to remove heavy metal ions from water and select economical and efficient renewable adsorption materials have been the research importance of scientific researchers.For the purpose of the modification of biomass materials and the removal of heavy metal ions,the lignin in loofah complex was separated by glycerol to obtain porous loofah complex,the loofah complex with a large number of adsorption groups was grafted by polyethyleneimine,and the orange mesocarp was obtained from Fengjie navel orange.The adsorption properties and adsorption mechanism of the three materials for heavy metal ions were systematically studied.The specific work is divided into the following three parts:1.With loofah as raw material,glycerol and water as solvent,lignin in loofah was separated,and porous loofah was prepared without changing the main structure of loofah.The effects of preparation conditions such as volume fraction of solvent glycerol,reaction temperature and reaction time on the adsorption of Cr(Ⅵ)on porous loofah complex were investigated by single factor experiment.The results showed that the adsorption effect of porous loofah complex was the best when the volume fraction of solvent glycerol was 50%,the reaction temperature was 200 ℃ and the reaction time was 70 min.The porous loofah complex,original loofah complex and lignin were characterized by Fourier transform infrared spectrometer,scanning electron microscope and UV-Vis spectrophotometer.The results showed that lignin was extracted from loofah complex,and the pores on the surface of porous loofah complex increased.The adsorption mechanism of porous loofah complex and original loofah complex was studied.When the amount of adsorption material was 100 mg,10 mg/L Cr(Ⅵ)solution was 20 ml,p H = 2.00,adsorption temperature was 293.15 K and adsorption time was 2 h,the adsorption rate of porous loofah complex material to Cr(Ⅵ)was 61.36%,while that of original loofah complex material was 49.11%.The thermodynamic study on the adsorption of Cr(Ⅵ)by porous loofah complex material and original loofah complex material shows that the adsorption process of Cr(Ⅵ)by porous loofah complex material and original loofah complex material is exothermic reaction in the temperature range of 293.15～318.15 K,and it is an entropy reduction process,which can not be carried out spontaneously,indicating that physical adsorption has taken place.The adsorption processes of the two materials accord with lagergren’s Quasi second-order kinetic equation.The adsorption of Cr(Ⅵ)on porous loofah complex material conforms to Langmuir isothermal adsorption model,which is monolayer adsorption.The fitting results show that the saturated adsorption capacity is 5.34mg/g.the original loofah complex material conforms to Freundlich isothermal adsorption model,and the adsorption is on non-uniform surface.The adsorption capacity of sponge gourd is still not good enough than that of the original sponge gourd material.The adsorption rates of porous loofah complex and original loofah complex materials for Cr(Ⅵ)in natural lake water were 46.54% and 16.89% respectively.2.With loofah complex as the main structure,polyethyleneimine(PEI)as the graft,3-(2-aminoethylamino)propyl triethoxysilane(APTES)and glutaraldehyde as the crosslinking agent,the loofah complex was chemically grafted and modified to prepare PEI/loofah complex.The effects of five preparation conditions such as APTES,the amount of glutaraldehyde,the feed ratio(M:m),time and temperature of loofah complex and polyethyleneimine on the composite adsorption of Cr(Ⅵ)by PEI/loofah complex were studied by orthogonal experiment.It was determined that the primary and secondary order of the five factors on the results was APTES dosage > feed ratio(PEI)> GA dosage > time >temperature,and there was no interaction between these factors;The optimum experimental conditions for the preparation of PEI/loofah complex material are as follows: the amount of APTES is 1.5 ml,the ratio of loofah complex: Pei is 1:7.5,the amount of glutaraldehyde is0.5 ml,the reaction time is 12 hours and the temperature is 60 ℃.The material was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy.The results showed that Pei was successfully attached to the surface of loofah.The adsorption mechanism of PEI/loofah complex was studied.When the addition amount of PEI/loofah complex was 30 mg,10 mg/L Cr(Ⅵ)solution was 20 ml,p H = 2.00,adsorption temperature was 303.15 K and adsorption time was 2 h,the adsorption rate of PEI/loofah complex for Cr(Ⅵ)was 85.99%.In the temperature range of 298.15～318.15 K,the adsorption process of PEI/loofah complex for Cr(Ⅵ)is exothermic reaction,entropy decreases and can proceed spontaneously;It conforms to lagergren’s Quasi second-order kinetic equation.The adsorption of Cr(Ⅵ)by PEI/loofah complex conforms to Langmuir isothermal adsorption model,which is monolayer chemical adsorption and conforms to Langmuir isothermal adsorption model.The saturated adsorption capacity is 138.70 mg/g.After four times of cyclic adsorption,the adsorption rate of PEI/loofah complex still reached 62.64%,which can be used for cyclic adsorption.PEI/loofah complex has better adsorption rate for mixed metal ions Pb(Ⅱ),Cu(Ⅱ),Ni(Ⅱ)and Cd(Ⅱ),but the adsorption rate for Pb(Ⅱ)is lower than that of the original loofah complex.The adsorption rate of PEI/loofah complex for Cr(Ⅵ)in natural lake water were 68.49%.3.The mesocarp of Fengjie navel orange was used as the adsorption material to study the adsorption effect and mechanism of Pb(Ⅱ)in water.The results showed that when the addition amount of orange mesocarp material was 100 mg,10 mg/L Pb(Ⅱ)solution was 20 ml,p H = 4.00,adsorption temperature was 303.15 K and adsorption time was 2 h,the adsorption rate of orange mesocarp material for Pb(Ⅱ)was 94.61%.The adsorption of Pb(Ⅱ)by orange mesocarp material is an endothermic reaction in the temperature range of293.15～318.15 K,the entropy increases and can proceed spontaneously;The adsorption process conforms to lagergren’s Quasi second-order kinetic equation;The adsorption of Pb(Ⅱ)by orange mesocarp material conforms to Freundlich isothermal adsorption model,which is the adsorption on non-uniform surface and a chemical adsorption process.After four times of recycling,the adsorption rate of orange mesocarp material still reached 79.69%,and the recycling capacity was good.The adsorption rate of orange mesocarp material for Pb(Ⅱ)in natural lake water were 97.50%,which can be applied to the adsorption of Pb(Ⅱ)in actual Lake lead containing waste water. |
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