【作者】 刘晴；

【导师】 李德亮；

【作者基本信息】 河南大学 ， 分析化学， 2010， 硕士

【摘要】 本文利用原位修饰法制备的γ-氨丙基三乙氧基硅烷(APS)表面修饰的纳米二氧化硅(AMNS)作为新型吸附剂,探讨了将其作为吸附剂对茜素红AR、刚果红CR、结晶紫CV和孔雀石绿MG等染料模拟废水进行处理的可行性,研究了其对染料的吸附性能、吸附机理和吸附动力学,为开发利用AMNS作为吸附剂提供了理论依据。此外,并与未修饰的纳米SiO2在相同条件下进行了吸附性能的比较;考察了AMNS与活性炭在吸附容量、吸附速度、再生性能方面的对比,实验结果如下:(1)影响吸附的因素有:染料溶液初始pH、吸附剂用量、吸附时间、染料溶液初始浓度和温度。AMNS吸附性能受溶液的pH影响很大,对于AR、CR,随着溶液pH的降低吸附率增加,而CV和MG随pH的降低吸附率减少,这与不同pH值下吸附剂表面电荷有关; CR、CV和MG随着温度升高吸附率增加,AR随着温度升高吸附率减少;增加吸附剂用量和吸附时间、染料初始浓度都能提高对染料的吸附率,但吸附量却随着吸附剂用量的增加而降低,随着染料溶液初始浓度的增加而增加。而随着溶液初始浓度的增加,AMNS对染料的吸附量增加,吸附率降低,因此,在实际应用时要同时考虑这两方面。(2) AMNS吸附两种阴离子染料(AR、CR)和两种阳离子染料(CV、MG)都较好的符合Langmuir吸附等温式。在实验最佳条件下对阴离子染料(AR、CR)和阳离子染料(CV、MG)的饱和吸附量分别达到200.0 mg·g-1、133.3 mg·g-1、40.0 mg·g-1和102.0 mg·g-1。其中,对阴离子染料具有较高的饱和吸附量。(3) AMNS对这四种染料吸附速率都较快,前10min时的吸附率和吸附量上升最快,然后时间持续60min时吸附基本达到平衡,吸附动力学都较好的符合Lagergren准二级反应模型;其吸附阴、阳离子染料主要是通过静电作用完成。(4)热力学分析表明,AMNS吸附AR时,△H 0<0,△S0<0,△G 0<0,是自发放热过程,吸附后体系变得更加有序;AMNS吸附CR、CV和MG时,△H 0>0,△S0>0,△G0<0,是自发吸热过程,吸附后体系变得更加紊乱。(5)将AMNS对阳离子染料、阴离子染料的吸附性能进行了对比,结果表明:对阴离子染料的饱和吸附容量比较大。(6)在相同实验条件下,AMNS吸附AR、CR和MG比未修饰的纳米SiO2效果好,这可能是因为AMNS表面存在活性官能团-NH2,更易于与其他官能团相互作用。(7) AMNS比活性炭相对的更适合用于吸附AR、CR和MG染料废水,主要有下面3个优点:①吸附容量较大;②吸附速度快;③可再生,AMNS在酸性或碱性解吸剂的作用下,能够释放出来被吸附的染料分子,吸附剂达到重复利用,染料浓缩回收,从而获得两方面的效益。因此,AMNS作为一种新型的吸附剂对染料废水的预处理或深度处理具有很大的优势,将它应用于工业化处理,有利于降低成本,提高处理效率。更多还原

【Abstract】 The adsorption behaviors of alizarin red-S, Congo red, crystal violet and malachite green on modified nano-SiO2 (AMNS) were investigated. The adsorption properties, mechanism and dynamics were discussed. The results supported the feasibility that AMNS as an absorbent theoretically. As comparisons, no modified nano-SiO2 and activated carbon was also taken into the experiments. The conclusions were obtained by follow.(1) The factors that affect the adsorption of dyes on AMNS included pH, adsorbent dose, adsorption time, initial concentration of the dyes and temperature. The initial pH of the dyes solution was an important influence factor on adsorption capacity. The adsorption capacities of alizarin red-S and Congo red increased with the medium pH decreased, while those of crystal violet and malachite green decreased. That might be related to adsorbent surface charge state. Adsorption capacities of Congo red, crystal violet and malachite green increased with the temperature increase, while that of alizarin red reduced. Increase the dose of adsorbent could improve removal ratios of dyes, as well as increase adsorption time and the initial concentration of the dyes. The adsorption capacities decreased with adsorbent dose increase and increased with the initial concentration of the dyes increase. The adsorption capacity increased and the adsorption rate decreased with the initial concentration increase of dyes. So, it should be considered in practical process.(2) The adsorption behaviors of the dyes on AMNS were accorded with Langmuir isotherm model. Under the optimum conditions, the maximum adsorption capacities of anionic (alizarin red and Congo red) and cationic dyes (crystal violet and malachite green) were 200.0 mg·g-1, 133.3 mg·g-1, 40.0 mg·g-1 and 102.0 mg·g-1, respectively. Moreover, adsorbent has high adsorption capacity for anionic dyes.(3) All the adsorption processes were rapid. The removal and adsorption capacity of dyes rose rapidest at the beginning of 10 min. The adsorption equilibrium was near to equilibrium at 60 min. The adsorption dynamics were all followed Lagergren pseudo-second-order kinetics. The adsorption mechanisms were shown to be the electrostatic interactions between the anionic dyes (cationic dyes) and adsorbent.(4) The thermodynamic analysis indicated that the standard thermodynamic function changes of the adsorption of AR on modified nano-silica wereΔH0<0,ΔS0<0,ΔG0<0, indicating the adsorption was a spontaneous exothermic process. After the adsorption, the system became order even more;on the other hand, the standard thermodynamic function changes of the adsorption of CR, CV and MG onto the modified nano-silica wereΔH0>0,ΔS0>0,ΔG0<0, which expressed that the adsorption were spontaneous endothermic processes. The increased temperature was advantageous to the adsorption. After the adsorption, the system became more disordered.(5) Comparing the adsorption characteristic of anionic dyes and that of cationic dyes, it indicated that the former had a high adsorption capacity.(6) Under the same experimental conditions, the adsorption efficiencies of AR, CR and MG by AMNS were better than that of unmodified nano-SiO2. It might be attributed to the existed -NH2 on the surface of AMNS, which could react with other functional groups more easily.(7) Comparing with activated carbon, AMNS was more suitable for adsorbing AR, CR and MG from their wastewaters. It had the following advantages: higher adsorption capacity, fast adsorption and regeneration. The adsorpted dye molecules could be released from AMNS with acidic or alkaline desorption agent. Therefore, as a new adsorbent, AMNS has great advantages for the pretreatment or deep processing of dye wastewater. It would reduce costs and improve processing efficiency.更多还原