| With the fast development of modern industry, heavy metal and dye contaminants in the world become more and more severe. The heavy metal and dye pollutions do harm to environment and human health as it is able to be biological enriched through the food chain. Therefore, how to eliminate the harm of heavy metals and dyes is a problem that current environmental protection work needs to solve urgently. Treating heavy metal and dye pollutions by biosorption method is a hot focus of study because it has many advantages such as abundant sources, high metal and dye binding capacity and little second pollution etc.In this paper, ephedra waste was chosen as the raw material to prepare two biosorbents SEW and AEW through chemical modification by using H2SO4 and diethylenetriamine, respectively. These two biosorbents were used to adsorb Cu2+, Pb2+, Cd2+, Zn2+, neutral red and methylene blue from aqueous solutions. The ephedra waste before and after modification was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and the functional group titration. Through single factor experiment, the effects of modification time,temperature and so on were investigated, the optimum modification conditions were determined. By dint of static absorption test,the effects of p H, contact time and the amount of the adsorbent were investigated.The optimum absorption conditions were determined. The adsorption kinetics and adsorption isotherms were analyzed systematically. Further more, the technology of desorption and reuse for the modified ephedra waste was tested and the adsorption mechanism was also discussed. The main results are as follow:1. The optimum modification conditions of SEW: the concentration of sulfuric acid was 10 mol/L, the temperature of modification was 95℃, the time of modification was 10 h and the solid-liquid ratio of modification was 1:12; the optimum modification conditions of AEW: the amount of ephedra waste was 1.00 g, the concentration of sodium hydroxide was 5%, the time of etherification reaction was 1 h, the temperature of etherification reaction was 60℃, the volume of epichlorohydrin was 3 m L, the time of amination reaction was 2 h, the temperature of amination reaction was 100℃, the volume of diethylenetriamine reaction was 0.5 m L.2. The results of characterization showed that after chemical modification, SEW and AEW had more loose morphology and more functional groups on surface, surface area was inereased.3. The optimum adsorption p H of Cu2+, Pb2+, Cd2+, Zn2+, neutral red and methylene blue on SEW was 5.0, 5.0, 5.5, 5.0, 5.0 and 6.0, respectively; the optimum adsorption time of Cu2+, Pb2+, Cd2+, Zn2+, neutral red and methylene blue was 1 h, 1 h, 1 h, 1 h, 1 h and 2 h, respectively; the optimum adsorption solid-to-liquid ratio of Cu2+, Pb2+, Cd2+, Zn2+, neutral red and methylene blue was 4 g/L, 6 g/L, 4 g/L, 8 g/L, 6 g/L and 4 g/L, respectively. The sorption kinetics of Cu2+, Pb2+, Cd2+, Zn2+, neutral red and methylene blue on SEW obeyed pseudo-second-order sorption kinetics. The adsorption of Cu2+, Pb2+, Cd2+, Zn2+ and methylene blue on SEW fitted both Langmuir and Freundlich model, but neutral red adsorption only fitted Langmuir model, the maximum adsorption capacities for Cu2+, Pb2+, Cd2+, Zn2+, neutral red and methylene blue on SEW were 139.7,149.1,246.7,81.43,252.4 and 211.4 mg/g, respectively,4. The optimum adsorption p H of Cu2+, Pb2+, Cd2+, Zn2+, neutral red and methylene blue on AEW was 4.5, 5.5, 5.0, 5.5, 5.0 and 6.0, respectively; the optimum adsorption time of Cu2+, Pb2+, Cd2+, Zn2+, neutral red and methylene blue was 3 h, 2 h, 1 h, 1 h, 1 h and 1 h, respectively; the optimum adsorption solid-to-liquid ratio of Cu2+, Pb2+, Cd2+, Zn2+, neutral red and methylene blue was 4 g/L, 10 g/L, 6 g/L, 6 g/L, 4 g/L and 10 g/L, respectively. The adsorption of Cu2+, Pb2+, Cd2+, Zn2+, neutral red and methylene blue on AEW fitted both Langmuir and Freundlich model, the maximum adsorption capacities for Cu2+, Pb2+, Cd2+, Zn2+, neutral red and methylene blue on AEW were 93.11,133.5,92.59,90.25,362.3 and 152.7 mg/g, respectively,5. Metal and dyes loaded biosorbents were be regenerated using 0.1 mol/L HNO3 solutions, it could be used repeatedly for five times with little loss of adsorption capacity, the sorption rate also can be up to 90%.6. The adsorption mechanism of modified ephedra waste on heavy metal ions and dyes may be partly the result of the ion exchange, chelation, hydrogen-bond interaction and encapsulation; another may be a small amount of physical adsorption.The ephedra waste modified by sulfuric acid and diethylenetriamine was a kind of biosorbent with good absorptive property, it can be used to deal with waste water which contain Cu2+, Pb2+, Cd2+, Zn2+, neutral red and methylene blue. Based on the finding above, a new high-performance, low-cost approach will be provide an excellent foundation for treating the heavy metals and dyes contamination pollution, having practical significance to realize comprehensive utilization of resources... |
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