壳聚糖改性石膏晶须及其汞吸附性能研究

发布时间：2018-10-13 17:07

【摘要】：石膏晶须又称硫酸钙晶须(CSW),是一种成本较低、性价比较高而用途广泛的新型无机材料,目前在涂料、橡胶、塑料、造纸等领域正获得越来越多的应用。已有人初步尝试将石膏晶须用于含磷、油或染料等模拟废水的净化,显示出一定效果。但是,石膏晶须在环境工程领域的研究应用还相当缺乏,尤其是石膏晶须对污染物的亲和性较弱、稳定性欠佳等方面都是需要系统解决的技术问题。研究硫酸钙晶须的表面改性方法,强化其对常见污染物的去除能力,无疑对拓展石膏晶须在环境领域的应用潜力具有现实意义。常规的硫酸钙晶须的制备方法主要有水压热法和常压酸化法两种,但仍然存在工艺过程较复杂、生产成本偏高等不足。本论文采用反应结晶法制备硫酸钙晶须,系统探讨了聚合物添加剂P123的浓度、溶液的过饱和度SI、温度、溶液的pH值、反应时间等操作条件对CSW的生长习性和形貌的影响,结果表明:实验条件下,溶液的过饱和度、温度、反应时间是影响晶须形貌的关键因素,适量的P123有助于晶须长径比的改善,而pH值的影响则不明显。在30~60℃、过饱和度0.25~0.57、溶液pH=7左右、反应时间为4~12h的条件下,可制备出长径比大且形貌比较均匀的硫酸钙晶须。反应结晶法具有流程操作简单、生产成本低、效率较高的优点。为改善石膏晶须与重金属的亲和性,本文采用复合改性剂壳聚糖-己二酸对反应结晶法制备出的硫酸钙晶须进行表面改性,研究了改性剂用量、改性温度、改性pH、搅拌速度等操作参数对改性产物用于实验室模拟废水中重金属汞(Hg2+)的净化效果的影响,结果表明:改性温度、改性pH、搅拌速度均对改性晶须吸附汞的效果有影响,温度升高、搅拌速度增大,改性晶须吸附汞的效率呈上升趋势;改性溶液pH值在7.5左右时,改性晶须吸附汞的效率达95%左右;改性剂的用量,即壳聚糖与己二酸的质量百分数之比对改性晶须吸附汞的效率影响不明显。为了解壳聚糖-己二酸改性石膏晶须净化二价汞的规律和机理,论文通过间歇吸附试验研究了改性石膏晶须净化重金属汞的过程,探讨了吸附时间、pH值、吸附温度、晶须用量等操作条件对除汞效果的影响,同时考察了晶须对汞的吸附动力学和吸附等温线,并结合扫描电镜(SEM)、红外光谱分析以及热重等分析手段来分析晶须除汞的机理。结果显示:pH值是影响石膏晶须吸附汞效果的关键性因素,改性晶须对汞的吸附率随pH值的增大呈现先增大后不变的趋势,在pH=7.5时,晶须对二价汞的去除效果大于95%;在pH=7.5时,晶须除汞过程在2~3h左右完成。当汞的初始浓度在1000~4000ug/L的范围内时,晶须对汞的吸附与Langmuir吸附等温线模型保持很好的一致性,吸附动力学符合准二级吸附动力学模型。石膏晶须与汞的作用机理为包覆到晶须表面的壳聚糖中的氨基、羟基与汞发生螯合作用形成稳定的内络盐(-N-Hg-O-)而被吸附,这个过程主要是化学吸附过程。除此之外,还有可能存在石膏晶须与汞之间的物理吸附作用。
[Abstract]:The gypsum crystal whisker, also known as calcium sulfate whisker (CSW), is a new type of inorganic material with low cost, high cost performance and wide application, and is currently getting more and more applications in the fields of coating, rubber, plastics, paper making and so on. A preliminary attempt has been made to purify the gypsum whiskers in simulated wastewater containing phosphor, oil or dye, and show the effect. However, the application of gypsum crystal whisker in the field of environmental engineering is also quite deficient, especially the weak affinity and poor stability of gypsum crystal whisker in environmental engineering. It is of great practical significance to study the surface modification method of calcium sulfate whisker and strengthen its ability to remove common pollutants. The preparation method of the conventional calcium sulfate crystal whisker is mainly composed of a water pressure thermal method and a normal pressure acidification method, but still has the defects of complex process process, high production cost and the like. The effects of operating conditions such as concentration of polymer additive P123, supersaturation SI, temperature, pH value of solution and reaction time on the growth habit and morphology of CSW were discussed. The supersaturation, temperature and reaction time of the solution are the key factors affecting whisker morphology, and a proper amount of P123 contributes to the improvement of whisker aspect ratio, and the effect of pH is not obvious. The calcium sulfate whisker with large aspect ratio and uniform morphology can be prepared under the conditions of 30 ~ 60 鈩，

本文编号：2269343