【作者】 孙文田；

【导师】 董德明；

【作者基本信息】 吉林大学 ， 环境科学， 2008， 博士

【摘要】 本论文系统地研究了不同来源的脱水剩余活性污泥吸附铅、镉的热力学及动力学特性,计算了不同污泥吸附铅、镉的热力学参数,比较了不同污泥的吸附能力,确定了不同污泥吸附铅、镉的动力学特征,分析了动力学参数的差异,研究并讨论了影响污泥吸附铅、镉的因素,完善了脱水剩余活性污泥铅镉的解吸方法,全面地比较了污泥干化和加碱预处理前后吸附铅、镉的动力学及热力学变化并分析了动力学特性变化的原因,探讨了污泥预处理前后吸附特性的改变与预处理的关系,判明了预处理的实效和意义,深化分析了离子交换对污泥吸附铅、镉的贡献及差异,测试分析了参与不同来源的剩余活性污泥吸附铅、镉的官能团类型,测试确定了化学沉淀在污泥吸附铅、镉中的作用情况,初步探讨了污泥吸附铅、镉的作用机制,统计分析了污泥吸附铅、镉的特征参数与污泥组成的相关关系。本论文为污泥吸附重金属废水的应用提供理论支持。研究结果表明,脱水污泥的吸附能力较强;污泥干化后,吸附能力及吸附速率都降低;污泥经碱处理后吸附能力较干污泥有所提高,但不是全部高于湿污泥的吸附能力,所以采用脱水湿污泥直接用于铅、镉的吸附在实际应用上应更简单易行。污泥投加量、pH值对各种污泥吸附铅、镉的影响较大,温度的影响较小,铅镉共存吸附时相互有抑制作用,共存的铅对镉的吸附影响更大。脱水污泥吸附铅、镉后,HCl解吸和EDTA解吸效果各不相同,由于解吸液难于泥水分离,其实用意义有限。离子交换是污泥吸附铅、镉的主要作用机制之一。羟基、氨基、酰基、羧基基团是各种来源污泥吸附铅、镉的主要作用官能团。剩余活性污泥在吸附铅、镉的过程中,形成无机物晶型沉淀的情况不多,离子交换、络合和微沉淀应是铅、镉吸附的主要机制。污泥的组成对污泥吸附特征参数的影响主要表现在吸附热力学参数方面,污泥中的矿物质钙对污泥吸附重金属的能力有影响,而污泥中的钠、铁及锰的含量影响污泥对铅、镉的吸附能力或亲和力,污泥自身的pH不仅影响污泥对镉的吸附强度,也影响污泥吸附镉的动力学特性。更多还原

【Abstract】 The excess activated sludge discharged from the process of biological wastewater treatment is a waste liquid due to the proliferation of sludge microorganisms’, the sludge becomes wet earth type after concentrated and dewatered. Municipal wastewater treatment plant sludge is generated mainly from the excess activated sludge and primary sedimentation tank sludge. At present, lots of unstable sludge has become a heavy burden of sewage treatment plant, how to safely deal with this huge, complex sludge and makes it harmless, minimization, recycling has become an important issue which environmental and social workers concerned about. The current researches are more about the adsorption of heavy metal onto sludge, but little about the ones of the industrial wastewater sludge, more about dry sludge adsorption of heavy metal, and little about the direct application of sewage dewatered sludge. Most of studies did not consider the feasibility of desorption. And there are few comparative studies on the adsorption of heavy metals among the different sludge at the same experimental conditions. In this paper, the excess sludge that comes from different wastewater treatment plant is used to adsorb heavy metal ions, the adsorption characteristics and absorption mechanisms were studied for the aim to supply a theory support for the practical application of treating heavy metal wastewater and find an additional method to cost-effectively treat the heavy metal wastewater. So this study have the dual effect of making sludge resources and treating heavy metal wastewater, This study has the resources to achieve the remainder of the use of sludge, and has a wide range of potential applications.The main content of this study includes basic property analysis of the different dewatered excess sludge, the adsorptive thermodynamic and kinetic properties and it’s comparison of lead and cadmium to different sludge, the factors that influence lead and cadmium adsorption to sludge, the desorption of lead and cadmium from sludge, the pretreatment method of sludge and it’s influences on the adsorptive thermodynamic and kinetic properties of lead and cadmium to pretreated sludge, the further study involves the contribution of ion-exchange mechanism to the lead and cadmium adsorption to sludge, the primary mechanisms about lead and cadmium adsorption to sludge, the correlations between the adsorptive thermodynamic and kinetic parameters and the chemical composition of sludge. Some valuable results were concluded based on this study. The thermodynamic experimental data of lead and cadmium adsorption onto sludge is analyses through non-linear fitting, high correlation coefficient is derived using both the Langmuir and Freundlich isotherm fitting, better fitting accuracy is got with Langmuir isotherm in general which indicates the monolayer adsorption trend of activated sludge adsorption for lead and cadmium. Study shows that the dewatered excess activated sludge had a high adsorptive capacity for lead and cadmium and are appropriate to remove lead and cadmium as bio-absorbent, but also remains adsorptive capacity difference of different sludge. The adsorption process of lead and cadmium to the sludge is generally endothermic process, the enthalpy variation for the adsorption of lead and cadmium is little, the Gibbs free energy change is negative quantity in all the adsorption process which indicates the adsorptions of lead and cadmium to sludge are spontaneous.Most of the adsorption processes of lead and cadmium by excess activated sludge fit the pseudo-second-order kinetic model well, the kinetic constants of the adsorption of lead and cadmium by dewatered sludge is higher than usual, in which the lead kinetic constant are higher than cadmium kinetic constants. The adsorption processes of lead and cadmium by excess activated sludge is so quick that the high adsorptive capacity is attained within 15 to 30 minutes which is very beneficial to the practical operation. The adsorptive rate of lead and cadmium by the excess sludge is controlled by out layer diffusion or by out layer and intraparticle diffusion.Research shows that sludge dosage has much influence on the adsorption of lead and cadmium to sludge, the lead biosorption efficiency increased rapidly with the sludge dosage increasing, while the cadmium biosorption efficiency increased slowly with the sludge dosage increasing, for the cadmium, much more sludge dosage must be added in order to get the same biosorption efficiency as lead. The optimal sludge dosage for the lead and cadmium adsorption varies to different sludge. The pH value is an important factor that affects the adsorption of lead and cadmium to sludge. The lead adsorption to sludge generally has an appropriate pH range which is from 4 to 7, but has a different optimal range rest on the sludge type, the appropriate pH range of cadmium adsorption to sludge is narrow, in which an optimal pH is between 5 and 6. The sludge adsorptive capacity will decrease at low pH due to the competitive adsorption of proton and metal ions, while high pH leads to the hydrolysis and precipitation of heavy metal ions which is removed not by adsorption. Temperature has less effect on sludge’s adsorption to lead and cadmium, so the research and practical application can ignore it. In lead and cadmium coexisting adsorption system, cadmium coexisted inhibits the adsorption of lead to sludge, lead coexisted also inhibits the adsorption of cadmium and even more, this is explained for the heavy metal ion character differences including hydrolysis, electro negativity, plasma potential, ionic radius and redox potential etc.The heavy metal desorption effectiveness is associated with both the metal ion and the sludge type, high desorption efficiency is attained to some of the sludge with HCl and EDTA and problems lies in the low cadmium desorption efficiency to a certain sludge and difficult separation of the sludge from the desorption liquid, which makes the desorption invalidity in practical application.In general, dry sludge adsorption data is fitted the pseudo-second-order kinetic model better than the pseudo-first-order kinetic model, all the kinetic constants decrease after the dewatered sludge is dried and the cadmium adsorptive kinetic constants vary less than the lead adsorptive kinetic constants. The adsorptive mechanism shift from the surface adsorption to the surface and inner sphere together for the lead adsorption to the sludge before and after dewatered sludge is dried and intraparticle diffusion becomes important step for dry sludge.The adsorptive capacity of lead to the sludge treated by the alkali is higher than that of dry sludge, but not necessarily higher than that of wet sludge, therefore, sludge alkali treatment in order to increase adsorptive capacity of lead is valid to dry sludge, but not significance to the dewatered sludge, moreover the affinity of lead to the sludge treated with alkali deteriorations. The absorptive capacity of cadmium on different sludge through alkali treatment changes differently, some higher and some lower, the affinity of cadmium to the sludge strengthen after treated with alkali. Research shows that the sludge adsorptive capacity is not necessarily up after sludge dried and alkali treatment, this reflects the complexity that the differences of structure and composition of the sludge imposed on the absorptive characteristics of lead and cadmium. There is no pretreatment need for some dewatered sludge as it has high adsorptive capacity, the direct use as adsorbent is more simple and convenient without drying.Ion-exchange is one of main adsorption mechanisms that the excess sludge adsorbs lead and cadmium, especially significant on the adsorption of cadmium onto sludge. The contribution of ion exchange to the adsorption of lead and cadmium to sludge is related to both the initial concentration of lead and cadmium and also the type of sludge. Infrared analysis showed that the amines, hydroxyl, carboxyl groups of sludge is the functional groups on the adsorption of lead and cadmium. Little chance of inorganic precipitation happens during the adsorption of lead and cadmium onto various sludges. Ion-exchange, complexation and micro-precipitation should be the main adsorption mechanisms of lead and cadmium to sludge.The correlation analysis shows that the influence of the composition of sludge on the sludge adsorptive characteristic parameters is mainly embodied at the thermodynamics constants. Calcium content influences the sludge adsorptive capacity for heavy metal ions. Moreover, the content of Na, Fe and Mn influence the adsorptive capacity or affinity of the lead and cadmium onto the sludge. The sludge’s pH value influences the adsorptive intensity of cadmium as well as the dynamics of cadmium on sludge.In this paper, a comparative study on the adsorption characteristics including thermodynamics, dynamics and impact factors of lead and cadmium to dewatered activated sludge is accomplished for the first time. A more comprehensive study on the changes of the sludge adsorptive thermodynamics and dynamics for lead and cadmium before and after sludge pretreatment is done with a meaningful result. Further study on the ion-exchange contribution to the sludge adsorption for lead and cadmium is calculated, showing ion exchange is the main mechanism of the adsorption. Acid and complexation desorption of the dewatered sludge is tried. The main functional groups are ascertained on the adsorption process. This paper has a powerful theory support for the sludge reuse and heavy metal biosorption treatment.更多还原