【作者】 周崎；

【导师】 龚文琪；

【作者基本信息】 武汉理工大学 ， 环境工程， 2012， 博士

【摘要】 本研究利用白腐真菌Pleurotus ostreatus的培养基废弃物(Spent cottonseed hull substrate, SCHS)作为生物吸附剂吸附水溶液中的阳离子染料。本文进行了可行性研究和论证,并深入研究了吸附等温线、吸附动力学。吸附热力学以及动态吸附模型等机理。实验选取染料中具有代表性的吩嗪类、吩噻嗪类、三苯甲烷类、偶氮类中的中性红、亚甲基蓝、孔雀石绿、刚果红4种常用染料作为污染物,深入研究了SCHS对中性红、亚甲基蓝、孔雀石绿等3种阳离子染料的静态、动态吸附行为,借助微量热仪C80研究了SCHS对3种染料的吸附热力学。在研究SCHS对刚果红不同pH值条件下的吸附试验中,对一部分研究工作者在使用单一波长λmax测量刚果红浓度时未考虑pH值变化对λmax的影响,进行了纠正。实验证明不同pH值测量的刚果红最大吸收波长变化很大,这与SCI期刊中已经报道的文献不一致。实验证明,刚果红的最大吸收波长λmax在不同pH值溶液条件下会发生改变。因此,要准确测量不同pH条件下染料的浓度,必须考虑其最大吸收波长λmax的变化及相应吸光值的变化。通过现代分析测试技术付里叶变换红外光谱和热重分析表明,SCHS中含有胺基、羟基、羰基、羧酸基、磷酸基等活性吸附官能团位点,这些官能团能够与染料离子结合产生吸附作用。通过化学滴定测定了SCHS的零电点(pHPZC),进一步验证了在SCHS吸附剂上存在羰基、羧酸基、磷酸基等活性吸附官能团位点。在静态的系列吸附实验中,通过考察染料溶液pH值、吸附时间、吸附剂用量、吸附剂粒径、温度、离子强度、染料浓度等实验参数对染料吸附的影响,确定了最佳的吸附条件。应用Langmuir, Freundlich, Redlich-Peterson和Sips4种吸附等温线模型对SCHS在不同温度条件下吸附染料的数据进行了拟合分析。用准一级吸附动力学、准二级吸附动力学和粒子扩散模型对不同时间条件下SCHS的动态吸附行为进行了拟合分析。为验证各个模型的线性和非线性拟合的参数可靠性,本论文还比较了各个拟合结果的误差数据。通过对等温吸附模型、吸附动力学的线性回归和曲线回归比较分析,证明线性回归的数据误差明显偏大,非线性回归数据的可靠性要高于线性回归。吸附热力学的研究表明,SCHS吸附3种染料的Gibbs自由能变化AG°均小于0,且温度越高-△G。越小。这证明吸附过程引起Gibbs自由能降低,因此SCHS去除3种染料的吸附反应是自发进行的。焓变表明SCHS吸附3种染料的过程是吸热反应,SCHS对3种染料的吸附除了物理吸附外,化学吸附占有主导作用。溶液环境温度的升高,不仅有利于活化SCHS吸附位点,更重要的是在一定程度上增加了吸附位点的数量。通过用C80微量热仪对SCHS吸附染料的固相-液相体系热量变化的测量,证明SCHS与染料溶液反应过程中的热量变化不仅有吸热过程的吸附热还有放热过程的润湿热。由于吸附热较润湿热的值相差较大且整个体系润湿热起主导作用,因此整个体系放热起主导作用。最后,在动态吸附柱的实验中,通过改变吸附柱的柱高、染料溶液流入速度、初始浓度等单因素条件,研究了各种因素对动态吸附的影响。动态吸附柱的机理研究表明,可以用Thomas模型和BDST模型来描述SCHS生物吸附剂在动态吸附柱中吸附3种染料的行为。动态吸附实验表明, SCHS动态吸附柱可以有效去除溶液中的染料。本论文的主要创新点是：一、对一部分研究工作者在使用单一波长λmax测量刚果红浓度时未考虑pH值变化对λmax的影响,进行了纠正。实验证明有些染料在不同pH值溶液环境条件下,其发色基团的结构会发生改变,因此其最大吸收波长(λmax)及其吸光值也会随着pH值的变化而变化,此研究纠正了一些国内外学者在先前研究中存在的误区。二、通过对等温吸附模型、吸附动力学模型的线性回归和曲线回归比较分析,证明线性回归的数据误差明显偏大,非线性回归数据的可靠性要高于线性回归。三、运用C80微量热仪对吸附染料的固相-液相体系热量变化的测量,证明SCHS与3种阳离子染料溶液反应过程中的热量变化不仅有吸附热,还有放热过程的润湿热,吸附热较润湿热的值相差较大,因此,整个体系润湿热起主导作用。这是目前文献中没有报道的。更多还原

【Abstract】 This study focused on the possible use of the spent cottonseed hull substrate (SCHS), an agricultural waste was used after the cultivation of white rot fungus Pleurotus ostreatus (P. ostreatus), to adsorb three kinds of cationic dyes, Neutral Red (NR), Methylene Blue (MB) and Malachite Green(MG) from aqueous solutions. Meanwhile, the reliable maximum absorption wavelength (λmax) value for Congo Red (CR) dye at different pH values was researched in the paper.It was found that the λmax of CR is576nm at pH2.18-3.16,567nm at pH3.86, and496nm at pH>4.71, for the different structure of CR molecules at different pH. CR is very sensitive to the pH of solution and would change from red to blue, due to π-π transition in azo group shifts to higher wavelength because of protonation. This experiment revealed that at lower pH it becomes cationic and shows two tautomeric forms of protonated CR, i.e. ammonium rich variety and azonium variety. So the test proved that relevant papers about research of λmax of Congo Red published in some Journals are incorrect.Fourier transforms infrared (FTIR) spectroscopy and thermo-gravimeter analyses (TG-DTG) were used for the characterization of the biosorbents. For the pure SHCS adsorbents, the functional groups on the SCHS surface, such as-NH, OH, C=O, COO-and-P=O, have been considered to be potential adsorption sites for entrapment of dyes molecules. The pH at point of zero charge (pHPZC) of the adsorbent was determined by the titration method. The efficient adsorption process is ascribed to the massive functional groups on the biosorbent surface such as hydroxyl and carboxyl. The TG-DTG of the biomass proved that SCHS is mainly composed of hemicelluloses, cellulose and lignin, etc.A batch adsorption study was carried out with variable solution pH, adsorbent amount, adsorption time, temperature and initial concentration. It was found that dyes uptake was favorable at pH>pHzpc. Langmuir, Freundlich, Redlich-Peterson and Sips isotherm models were applied to the analysis of experimental equilibrium data of SCHS adsorption dyes. The effect of contact time at different temperatures was fitted to pseudo-first-order and pseudo-second-order kinetic models. Linear regressive method and nonlinear regressive method were used to obtain the relative parameters. The nonlinear method may be better with the absolute error as limited condition. The adsorption process was spontaneous and endothermic.Thermodynamic parameters of free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°), obtained from biosorption of dyes ranging from different temperature, showed that the adsorption was a spontaneous and endothermic process. The negative value of ΔG°indicates the spontaneity and feasibility of the biosorption process. The decrease in ΔG°value with rising temperature reveals that adsorption of dyes onto SCHS becomes more favorable at higher temperature. By using micro-calorimetry C80to measure the heat change of dyes onto SCHS in the experiment, it is proved that the wetting heat plays a leading role in solid-liquid adsorption system and the wetting is exothermic process during action.At last, the adsorption potential of SCHS to remove dyes from aqueous solution was investigated using fixed-bed adsorption column. The adsorption data were fitted by two fixed-bed adsorption models namely, Thomas and BDST models. The results fitted well to the models at different conditions. The SCHS was shown to be suitable adsorbent for adsorption of dyes using fixed-bed adsorption column.The major innovative points of this paper were summarized as follows.First of all, the experiments proved that the chromophore structure of some dyes will change at different pH and λmax and its value would change with the changes of pHs value. So the tests proved that relevant papers about research of λmax of Congo Red published in some Journals are incorrect by some scholars in the previous study.Second, linear regressive method and nonlinear regressive method were used to obtain the relative parameters of the adsorption isotherm, kinetics model. The data reliability of non-linear regression is higher than the linear regression.The error analysis was conducted to prove that nonlinear method was better to predict the experimental results.Third, by using micro-calorimetry C80to measure the heat change of solid phase-liquid phase adsorption of dye in the experiments, it was proved that the heat change process is composed by the wetting heat of exothermic and the adsorption heat of endothermic. Above all, the wetting heat of the system plays a leading role and its value is much larger than the later. This is not reported in the previous literature.更多还原