| The hydrotalcite-like materials is a kind of functional materials with special layer structure,which is widely used in adsorption,ion exchange,catalysis and other fields.In this paper,the hydrotalcite-like materials were prepared with electroplating wastewater through instant synthesis method,the application to environmental control such as heavy metals and iodide pollution were also discussed.The study has provided important technical and theoretical support for complex pollutants treatment,and also provided experimental basisfor the resources-recycled management and comprehensive utilization of electroplating wastewater.The technical difficulty of this study lies in that the electroplating wastewater contains different type and valence metal ions.The physical and chemical properties and chemical composition of electroplating wastewater were determined.The adding metal ions were identified which could be prepared for hydrotalcite-like materials with the electroplating wastewater.The effect of metal molar ratio,pH,aging time and aging temperature on Cu-Mg-Al,Cu-Zn-Al,Cu-Ni-Al hydrotalcite-like materials preparation had been discussed.The material composition,structure,performance were analyzed by XRD,FT-IR,SEM,EDS,BET,TG-DTA,ICP-OES and other modern analysis techniques.The four factors of adsorption time,pH value,temperature,solid-liquid ratio had been examined to evaluate adsorption applicability for I-.The saturated adsorption capacitieswere calculated.Take Cu-Mg-Al hydrotalcite-like materials spreparation as an example,the removal of copper and other metal ions in electroplating waste water was discussed under different preparation conditions.The major works and conclusions are as follows:1.The analysis results of physical and chemical properties and chemical composition of electroplating wastewater showed that: the wastewater solution was strongly acidic,the solution density was 1.0313 g/m L,there were large number of metal ions,such as: Al,As,Ca,Cd,Cr,Cu,Mg.Among them,the Cu,Ni,Zn,Mg,Al content were 26078 mg/kg,18877 mg/kg,14425 mg/kg,377 mg/kg,801 mg/kg,respectively.2.The Zn2+,Ca2+,Fe2+,Mg2+,Cd2+-Al3+,Mg2+-Al3+,Zn2+-Al3+,Ni2+-Al3+ were examined to prepare the materials with electroplating wastewater,and the materials prepared directly by electroplating wastewater was also studied.The result showed that the Mg2+-Al3+,Zn2+-Al3+,Ni2+-Al3+ joined with electroplating wastewater could preparedthe materials with hydrotalcite-like structure.3.The effect of metal molar ratio,pH value,aging temperature and aging time on Cu-Mg-Al,Cu-Zn-Al,Cu-Ni-Al hydrotalcite materials preparation were discussed and the preparation conditions were optimized.(1)The preparation process of Cu-Mg-Al hydrotalcite-like materials was: Mg2+-Al3+ molar ratio was 3:1,pH value was 10,aging temperature was 60 ℃,aging time was 1 day.(2)The preparation process of Cu-Zn-Al hydrotalcite-like materials was: Zn2+-Al3+ molar ratio was 2:1,pH value was 11,aging temperature was the normal temperature,aging time was 0.5 day.(3)The preparation process of Cu-Ni-Al hydrotalcite-like materials was: Ni2+-Al3+ molar ratio was 1.5:1,pH value 10,aging temperature was the normal temperature,aging time was 1 day.4.The characterization of Cu-Mg-Al,Cu-Zn-Al,Cu-Ni-Al hydrotalcite-like materials had been studied by XRD,FT-IR,SEM,EDS,BET,TG-DTA,ICP-OES and other modern analysis techniques.The results showed that the Cu-Mg-Al,Cu-Zn-Al hydrotalcite-like materials had good performance such as grain shape,crystallinity,surface area,they were better than the Cu-Ni-Al hydrotalcite-like materials.(1)The Cu-Mg-Al hydrotalcite-like materials prepared under the optimized process had the structure characteristics of Mg-Al hydrotalcite materials,the crystal phase was single,and the order was high.The material interlayer filled with CO32-.The material was layered structure with regular edges and uniform size,the average particle size was 200 nm orso.The chemical formula was Zn0.015Cu0.028Ni0.021Mg0.482-Cd0.018Fe0.0005Al0.427Cr0.01(OH)2(CO3)0.218·0.5H2 O.(2)The Cu-Zn-Al hydrotalcite-like materials prepared under the optimized process had the structure characteristics of Zn-Al hydrotalcite materials,the crystal phase was single,and the order was high.The material interlayer filled with CO32-.The material was layered structure with regular edges and uniform size,the average particle size was 200 nm orso.The chemical formula was: Zn0.515Cu0.046Ni0.037Mg0.002-Cd0.082Fe0.002Al0.357Cr0.013(OH)2(CO3)0.185·0.5H2 O.(3)The Cu-Ni-Al hydrotalcite-like materials prepared under the optimized process condition had the characteristics of Cu-Ni-Al hydrotalcite material structure.The crystal phase was single with poor crystallinity.The material interlayer filled with CO32,the average particle size was 100 nm orso.The chemical formula was: Zn0.027Cu0.045Ni0.533Mg0.004Cd0.028Fe0.0008Al0.349Cr0.014(OH)2(CO3)0.181·0.5H2 O.5.Take Cu-Mg-Al hydrotalcite-like materials as an example,the preparation condition including adsorption time,pH value,temperature,solid-liquid ratio had been examined on removal application of Cu2+ and other metal in the electroplating wastewater.(1)The best removal condition of copper matched with Cu-Mg-Al hydrotalcite material preparation process.Under the best experiment condition,the copper removal rate was the best and its content decreased from 2689.4 mg/L to 0.2 mg/L.At the same time,the other metal concentration in electroplating waste water,such as: Zn,Ni,Cd,Fe,Cr,Mg,Al,significantly decreased.Among them,the Zn,Ni,Fe,Cd,Al concentration decreased from 1487.7 mg/L,1946.8 mg/L,28.5 mg/L,3081.4 mg/L below to emission regulation limit for new enterprise,respectively.(2)The effect of metals removalhad been studied based on the preparation of Cu-Zn-Al,Cu-Ni-Al hydrotalcite-like materials.The results showed that both could effectively remove the metals in the electroplating wastewater.The Zn,Ni,Fe,Cd,Al concentration decreased from 2689.4 mg/L,1487.7 mg/L,1946.8 mg/L,28.5 mg/L,3081.4 mg/L,185.7 mg/L below to emission regulation limit of new enterprise after the Cu-Zn-Al hydrotalcite-like materialswere prepared.The Cu,Zn,Fe,Cd,Al concentration decreased from 2689.4 mg/L,1487.7 mg/L,1946.8 mg/L,3081.4 mg/L,185.7 mg/L below to emission regulation limit for new enterprise after the Cu-Ni-Al hydrotalcite-like materials were prepared,the Mg was completely removed.6.The adsorption properties to I-of Cu-Mg-Al,Cu-Zn-Al and Cu-Ni-Al hydrotalcite-like materials prepared under the optimized process were studied.The effects of adsorption time,pH value,temperature,solid-liquid ratio were discussed.The theoretical adsorption capacities to I-were calculated.(1)The better adsorption condition to I-of Cu-Mg-Al hydrotalcite-like materials was that: adsorption time was 60 min,pH value was 7,adsorption temperature was 25 ℃,solid-liquid ratio(m/v)was 1:100.(2)The better adsorption condition to I-of Cu-Zn-Al hydrotalcite-like materials was that: adsorption time was 30 min,pH value was 8,adsorption temperature was 25 ℃,solid-liquid ratio(m/v)was 1:250.(3)The better adsorption condition to I-of Cu-Ni-Al hydrotalcite-like materials was that: adsorption time was 30 min,pH value was 8,adsorption temperature was 25 ℃,solid-liquid ratio(m/v)was 1:200.(4)The saturation adsorption capacities of Cu-Mg-Al,Cu-Zn-Al,Cu-Ni-Al hydrotalcite-like materials were 1111.12 mg/g,1000 mg/g,476.19 mg/g,respectively.All of the adsorption experimental data were well in line with the Langmuir and Freundlich adsorption models.The order of their adsorption capacities was consistent with material structure characterization. |
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