【作者】 姚瑞华；

【导师】 张龙军； 孟范平；

【作者基本信息】 中国海洋大学 ， 环境科学， 2009， 博士

【摘要】 本研究采用三种镧系金属（镧、钕和镨）分别对壳聚糖进行改性制备除氟剂，其最佳制备工艺条件为：壳聚糖用量为1.0 g·L^-1，Ln³⁺浓度为0.015 mol·L^-1，反应时间为6⁸ h。由三种除氟剂的X衍射图谱、红外谱图、电镜扫描图分析推断，在制备过程中，破坏了壳聚糖分子链内或链间的氢键，使原来壳聚糖的有序结构变得无序，形成了一部分无定形结构。在除氟剂的制备过程中，壳聚糖分子链C3位置上羟基同C2位置上的氨基同Ln（H₂O）_n³⁺一起参加反应，并构成稳定的五元环。制备过程中将Ln³⁺负载到壳聚糖分子的骨架上形成了不饱和配合物，配体F-交换除氟剂空腔内水分子的OH^-，完成对F-的吸附。因配位反应只发生在中心离子和配体之间，其它离子无此反应，故表现出高度选择性。通过正交试验优化了三种除氟剂（CTS-La、CTS-Nd和CTS-Pr）对氟离子的最优吸附工作条件：pH值为7，温度为323 K，吸附时间为60 min，吸附剂粒径为0.1 mm，脱乙酰度为95%。对于浓度为20 mg·L^-1的氟离子溶液，当吸附剂用量为1.2 g·L^-1时，去除率达到99%左右，处理后的F-浓度为0.98 mg·L^-1左右，可以满足世界卫生组织对于饮用水中氟含量(＜1.5 mg·L^-1)和《生活饮用水卫生标准》对饮用水的要求(＜1.0 mg·L^-1)。溶液中共存阴离子会对除氟效果产生一定的影响，结果表明，当阴离子浓度为500 mg·L^-1时，SO₄^2-、Cl^-、HCO₃^-、CO₃^2-和PO₄^3-除氟率分别下降14.3%、9.8%、19.1%、28.5%和17.6%，其影响能力大小顺序为：CO₃^2-＞HCO₃^-＞PO₄^3-＞SO₄⁽2-_＞Cl^-。吸附饱和的除氟剂，经0.4 g·L^-1的NaOH解吸24 h，能有效地恢复除氟剂的除氟性能；经吸附和解吸，再次吸附和解吸，连续使用4次后，除氟性能从98%下降到67%，除氟剂有一定的重复使用性。三种除氟剂的吸附等温线基本符合Redlich-Peterson吸附等温线方程，在323K时，CTS-Nd、CTS-Pr和CTS-La对氟离子的饱和吸附容量分别达到42.3、39.7和39.5 mg·g^-1。拟一级以及拟二级扩散模型计算得到平衡量qe,cal与实验得到的平衡吸附量qe,exp能较好的吻合，二者差异不显著（p＞0.05）。在323 K时，CTS-Nd、CTS-Pr和CTS-La的吸附速率常数分别为0.008、0.009和0.012 g·mg^-1·min^-1。颗粒内扩散模型的研究结果表明，在吸附过程中，吸附速率的大小不仅受颗粒的内表面扩散的控制，同时也受液膜形成的边界层等因素的影响。根据Arrhenius公式，计算得到CTS-Nd、CTS-Pr和CTS-La吸附氟离子的活化能E值分别为11.583、8.286和8.333 KJ·mol^-1，均小于42 KJ·mol^-1，说明吸附过程主要为物理吸附。小白鼠的亚急性毒性试验结果表明：在使用剂量范围内(La³⁺：≤106 mg·L^-1；Nd³⁺：≤260 mg·L^-1；Pr³⁺：≤180 mg·L^-1),水样对小鼠的行为、体重、饮食状况以及对生理和生化指标均无不良影响，与对照组无明显差异。用三种除氟剂对高密市大牟家镇的水样进行处理，通过调整吸附剂的用量，均达到了很好的去除效果。其中3#和4#水样由于氟离子浓度高，而且共存阴离子浓度均超V类水质标准的3⁴倍，当吸附剂用量为7.5⁸ g·L^-1时，出水中氟离子浓度可以满足饮用水低于1.0 mg·L^-1的要求。CTS-La、CTS-Nd和CTS-Pr三种壳聚糖的制备成本和运行成本分别为0.22⁰.34元/千克和0.032⁰.056元/千克。针对大牟家镇的实际水样处理，3#和4#水样的处理成本约为0.24⁰.448元/千克，其它站点的水样处理成本均低于0.12元/千克。三种除氟剂比较而言，采用CTS-La除氟剂具有处理成本低，除氟效率高的特点，实际使用，比较可行。采用负载镧系金属离子的壳聚糖应用于含氟水的处理，不但减少了含氟水对人体和环境的毒害作用，而且充分资源化利用了海产品的加工废弃物——壳聚糖，创造了一定的价值。因此，采用以壳聚糖为载体的镧系金属新除氟剂具有一定的社会效益、环境效益和经济效益。更多还原

【Abstract】 In this work, the applicability of chitosan modified by Ln³⁺ （Lanthanum,Praseodymium, Neodymium） as adsorbents for the remova l of excess fluoride ionsfrom water is studied. The synthesis conditions of Ln³⁺ incorporated chitosan areoptimized as: the dose of chitosan is 1.0 g·L^-1, the dosage of Ln³⁺ is 0.015 mol·L^-1, thepreparing time is 6⁸ h. From the XRD, FTIR specture, SEM ima ges, it can beobserved that the hydrogen bonding of intermolecular and intramolecular is weakened ,the crysta l structure is destructed and the particle amorphism structure is formed. TheLn（H2O）n³⁺ can chelated with C-3 hydroxyl groups and C-2 amino groups to form the5-element loop. The unsaturated complex is formed when Ln³⁺ is loaded into chitosanmolecular, F- can excha nge with OH- of water molecular and other ions don’t has thesame ability, so the adsorbent has higher selectivity adsorption capability.The treatment conditions are optimized: pH value is 7, water temperature is 323 K,stirring speed is 400 rpm, contact time is 60 min, particle size is 0.1 mm,deacetylation of chitosan is 95%. A salt rejection against the water containing F- of 20mg·L^-1 was 99% at the dosage of adsorbent was only 1.2 g·L^-1, and the resid ualconcentration of F- is 0.98 mg·L^-1, lower tha n 1.0 mg·L^-1, which is restricted by WHOand Standard for Domestic Drinking Water. The drinking water contains severa lcommon other anions, which can compete with F- in the sorption process, from theadsorption experiment results, the CO₃^2-, HCO₃^-, PO₄^3-, SO₄^2-and Cl^- ions showsnega tive effect on the remova l of fluoride , the remova l efficiency could be decreased28.5%, 19.1%, 17.6%, 14.3%, 9.8%, respectively, and the order is CO₃^2-＞HCO₃^-＞PO₄^3-＞SO₄^2-＞Cl^-. The used adsorbents could be regenerated in 24 h by 0.4 g·L^-1 ofsodium hydroxide , and the remova l efficiency is reduced from 98% to 67% after it isregenera ted four times, it can be reused in applicability.The equilibrium sorption data are fitted reasonably well for Redlich-Petersonisotherm model, the ma ximum equilibrium sorption of CTS-Nd, CTS-Pr and CTS-Lahave found to be 42.3, 39.7 and 39.5 mg·g^-1. The qe,cal obtained from pseudo-first orderand pseudo-second order accord well with the qe,exp from the experiments, and have no significa nt difference between two groups （p＞0.05）. The initia l sorption rate of CTSNd,CTS-Pr and CTS-La are 0.008, 0.009 and 0.012 g·g^-1·min^-1 at 323 K, and thesorption process is complex, both the boundary of liq uid film and intra-particlediffusion contributed to the rate-determining step. The activation energy （E） obtainedfrom Arrhenius equation is 11.583, 8.286 and 8.333 KJ·mol^-1, which is lower tha n 42KJ·mol^-1, the adsorption process is physicosorption.The results of subacute toxicity test shows that it has no any side effects on behavior,feed and water intakes, physiochemica l parameters and histology of the rats, when theconcentration of La³⁺ is lower tha n 106 mg·L^-1, Nd³⁺ lower tha n 260 mg·L^-1, Pr³⁺ lowertha n 180 mg·L^-1.The water sampling from Damujia town in Gaomi area containing high fluorideconcentration, it could be removed effectively by conducting the dosage of adsorbentof CTS-Ln. 3# and 4# water containing fluoride ions and anions simultaneity, which is3⁴ times higher tha n the five class of water. When the dosage of adsorbent is 7.5⁸g·L^-1, the resid ual concentration of F- is 0.98 mg·L^-1, lower tha n 1.0 mg·L^-1. Thepreparing cost and running cost of CTS-Ln （CTS-La, CTS-Nd and CTS-Pr） is￥0.22⁰.34 and￥0.032⁰.056 per kilogram, respectively. When the 3# and 4# water istreated by CTS-Ln, the cost is￥0.24⁰.448 per kilogram, the cost of other samplingwater is lower than￥0.12 per kilogram. The cost of CTS-La is the cheapest and isfeasible to apply in practice.Fluord ie from drinking water can be removed by CTS-Ln, it can minimize thehaza rdous of flurodide water, and ma ximize the utilizing the chitosan obtained fromseafood processing wastes. So, the use of CTS-Ln as adsorbent would be profitablyto socia l, economic and ecological environment.更多还原