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题名: 新型镧铝复合固磷剂的制备及其应用基础研究
作者: 徐睿1
学位类别: 博士
答辩日期: 2017-06
授予单位: 中国科学院大学
授予地点: 北京
导师: 潘纲
关键词: 湖泊富营养化,磷,吸附剂,镧改性材料,同步辐射 ; Eutrophication, Phosphorus, Adsorbent, Lanthanum-modified materials,X-ray absorption fine structure spectroscopy
其他题名: Phosphorus locking by novel lanthanum/aluminum-hydroxide composite and its basic research on implications
学位专业: 环境科学
中文摘要: 湖泊富营养化现象已成为人类日益严峻的环境问题,而过量的磷进入水体是 导致湖泊富营养化的关键因素之一。因此,探寻高效安全的磷去除新材料和新原 理成为环境领域研究的热点。镧改性吸附剂因其具有较稳定的固磷效果而成为当 今研究最为广泛的除磷材料之一。然而,如何进一步提高镧改性除磷吸附剂的除 磷效果以及镧利用率仍然是我们面临的挑战。本文按照镧铝摩尔比例分别为 1:30,1:20和 1:10,通过氯化镧和氯化铝共沉淀的方法制备出三种镧铝固磷剂 LAH-1/30,LAH-1/20和 LAH-1/10,并采用同步辐射的表征手段研究了镧铝固 磷剂的微观特性及其对水体中正磷酸盐、植酸盐和焦磷酸盐的去除效果和作用机 理,另外还研究了其对太湖天然水体中磷的实际去除效果,从而为长效控制富营 养化水体的磷提供理论和技术支持。主要研究结果如下: (1)制备了三种镧铝固磷剂 LAH-1/30,LAH-1/20和 LAH-1/10,并对其 进行了多种表征。结果表明:镧铝固磷剂的主要成分为氢氧化铝和氢氧化镧的混 合物,平均粒径为 8 ~ 16 µm。镧铝固磷剂 LAH-1/30,LAH-1/20和 LAH-1/10 中镧元素含量依次为 5.3%,7.8%和 13.1%,比表面积依次为 107.1,121.0和 99.3 m2 g-1均高于商业化产品锁磷剂(38.2 m2 g-1)和氢氧化铝(51.2 m2 g-1)。镧 铝固磷剂的电荷零点约为 pH 9.7,而锁磷剂在 pH 4.0 ~ 10.0范围内,表面均带 负电荷(-5.4 mV ~ -43.1 mV)。镧铝固磷剂中镧元素 L3边扩展 X-射线吸收精细 结构(EXAFS)表明镧原子第一配位层 La-O配位数依次为 6.8 ± 0.7,6.5 ± 0.4 和 6.1 ± 0.3,均低于标准物氢氧化镧中 La-O饱和配位数 9.0。并结合电子顺磁 光谱(EPR)测定,表明镧铝固磷剂中镧化合物表面存在着氧空位结构。 (2)研究了镧铝固磷剂对水体中正磷酸盐的去除效果和作用机理。在 pH 为 4.0和 8.5时,镧铝固磷剂 LAH-1/30(镧含量为 5.3%)对正磷酸盐的吸附 量为 76.3和 45.3 mg P g-1,分别是锁磷剂(镧含量为 5.6%)正磷酸盐吸附量的 8.5倍和 5.3倍。磷 K边 X-射线吸收近边结构(XANES)结果表明,酸性条 件 pH 4.0时,磷与镧铝固磷剂中铝化合物的结合能力强;在碱性条件 pH 8.5时, 磷与镧铝固磷剂中镧化合物的结合能力强,证明了配位体交换机理的除磷作用。 镧 L3边 EXAFS结果表明,磷酸根通过形成双齿双核内层络合物的结构结合 在镧铝固磷剂中镧化合物的表面,并且固磷剂中镧化合物表面的氧空位结构对磷 酸盐的也起到一定的吸附作用。镧铝固磷剂主要通过静电引力机理、配位体交换 机理和氧空位的共同作用去除水体中的正磷酸盐。镧铝固磷剂中镧元素和铝元素 的共同作用对以后新型固磷剂的研发提供了一定的指导意义。 (3)研究了镧铝固磷剂 LAH-1/10对水体中不同种类磷如正磷酸盐、植酸 盐和焦磷酸盐的去除效果和作用机理。在 pH 8.5时,镧铝固磷剂 LAH-1/10对 正磷酸盐的最大吸附量为 70.4 mg P g-1,分别是对植酸盐和焦磷酸盐最大吸附量 的 1.9倍和 3.2倍。吸附动力学研究表明 LAH-1/10对植酸盐的吸附速率最快。 并且,LAH-1/10对三种形态磷的解吸率均较小。此外,LAH-1/10吸附三种形态 磷后样品的 Zeta电位、 P固态核磁(SSNMR)分析和磷 K边 XANES结果 共同表明了正磷酸盐、植酸盐和焦磷酸盐均通过吸附作用结合在镧铝固磷剂 LAH-1/10的表面。最小二乘法线性拟合结果(LCF)表明在碱性条件 pH 8.5时, 三种磷化合物均优先结合于镧铝固磷剂中镧化合物表面。 (4)研究了镧铝固磷剂 LAH-1/30和商业化产品锁磷剂对实际太湖水样中 磷的去除效果。结果表明:在低投加量时,即 La/P摩尔比值为 0.5:1时,LAH- 1/30对水体中 TDP的去除率为 20.0%,是锁磷剂对 TDP的去除率 6.1倍;而 当投加量增加至 La/P摩尔比值为 3:1时,LAH-1/30和锁磷剂对 TDP的去 除率差异较小,分别为 33.3%和 30.0%。此外,镧铝固磷剂 LAH-1/30对水体 中的 SRP有较好的去除效果,当 La/P摩尔比为 0.5:1时,其对 SRP的去除 率为 81.0%;当 La/P摩尔比增加至 3.0时,对 SRP去除率能达到 91.9%。 LAH-1/30投加后对水体中 TDN,NH4+ -N和 NO3- -N的含量影响均较小。并且, LAH-1/30中铝离子的浸出量远低于锁磷剂中铝离子的浸出量,但镧离子的浸出 量略高于锁磷剂。LAH-1/30在去除磷的同时对水体中 DOC也有一定的去除作 用,当投加量 La/P摩尔比值为 3:1时,其对水体中 DOC的去除率为 55.7%。
英文摘要: Excessive phosphorus (P) discharge can trigger severe eutrophication in aquatic environments, which is a serious environmental problem in the world. Hence, novel P removal materials and mechanisms have become research hotspot to mitigate eutrophication. Lanthanum (La) bearing materials have been widely used to remove P in water treatment owing to its stable P binding property. However, it remains a challenge to enhance P adsorption capacity and La usage efficiency. Here, a La/Al- hydroxide composite (LAH) with high P adsorption efficiency was synthesized by a co- precipitation method with different La:Al molar ratios of 1:30, 1:20, and 1:10 (LAH- 1/30, LAH-1/20, and LAH-1/10). X-ray absorption fine structure (XAFS) spectroscopy was used to detect the local atomic structures of P and La(III). The objective of this study is to synthesize a highly efficient P adsorption material and to investigate its mechanism to different P compounds including Orthophosphate (Ortho-P), Myo- inositol hexakisphosphate (IHP), and Pyrophosphate (Pyro-P) at the molecular level. The P removal efficiency of Lake Taihu water samples was also investigated. This methodology could be used to guide new development of geo-engineering materials for eutrophication management. The main results are listed as follows: (1) Three LAH were synthesized and investigated using multiple techniques. LAH were mainly composed of Al(OH)3 and La(OH)3 with an average particle size of about 8 ~ 16 μm. The La mass proportions of LAH-1/30, LAH-1/20, and LAH-1/10 were 5.3%, 7.8%, and 13.1%. The BET surface areas of LAH-1/30, LAH-1/20, and LAH- 1/10 were 107.1, 121.0, and 99.3 m2g-1, respectively, which were much higher than ). The LAH had positivethose of Phoslock (38.2 m2 g -1 ) and Al(OH)3 (51.2 m2 g-1 surface charge from pH 4.0 to 9.7, while Phoslock had negative potential from -5.4 to -43.1 mV in the pH range of 4.0 to 10.0. The La-O coordination numbers (CN) of LAH- 1/30, LAH-1/20, and LAH-1/10 were 6.8 ± 0.7, 6.5 ± 0.4, and 6.1 ± 0.3, respectively, which were all less than the saturated La-O CN of 9.0 in La(OH)3. The EPR spectrum of LAH-1/10 showed a clear signal at g = 2.0509 corresponding to oxygen defects on the surfaces. (2) The phosphate removal efficiency and mechanism were studied. The maximum phosphate adsorption capacities of LAH (5.3% La) were 76.3 and 45.3 mg P g-1 at pH 4.0 and 8.5, which were 8.5 and 5.3 times higher than those of commercially available La-modified bentonite (Phoslock, 5.6% La), respectively. P K-edge X-ray absorption near edge structure (XANES) analysis showed that phosphate was preferentially bonded with Al under weakly acid conditions (pH 4.0), while tended to associate with La under alkaline conditions (pH 8.5). La L3-edge extended X-ray absorption fine structure (EXAFS) analysis indicated that phosphate was bonded on La sites by forming inner sphere bidentate-binuclear complexes and oxygen defects exhibited on LAH surfaces, which could be active adsorption sites for phosphate. The electrostatic interaction, ligand exchange, and oxygen defects on LAH surfaces jointly facilitated phosphate adsorption but with varied contribution under different pH conditions. The combined contribution of La and Al may be an important direction for the next generation of commercial products for eutrophication mitigation. (3) The removal efficiencies and mechanisms of three P compounds (Ortho-P, IHP, and Pyro-P) were investigated. Under the same thermodynamic conditions, the maximum adsorption capacities of Ortho-P on LAH-1/10 were 70.4 mg P g-1 , which was 1.9 and 3.2 times higher than those of IHP and Pyro-P, respectively. Kinetic adsorption study showed that LAH-1/10 had the fastest binding ability to IHP. The Ortho-P, IHP, and Pyro-P desorption rates on LAH-1/10 were little. Zeta potential, XANES, and Solid state nuclear magnetic resonance (SSNMR) analyses indicated that the interaction between LAH and three P species was surface adsorption. Least-squares linear combination fittings (LCF) results showed that Ortho-P, IHP, and Pyro-P all showed an affinity preference for La-hydroxide in LAH. This work elucidates the adsorption properties and mechanism of Ortho-P, IHP, and Pyro-P on La/Al-bearing compounds at the molecular level, indicating that LAH was a promising material for P locking in eutrophication control. (4) Effects of Lake Taihu water samples after LAH-1/30 and Phoslock application showed that TDP removal rate by LAH-1/30 was 20.0% with a dosage of La/P molar ratio 0.5:1, which was higher than that of Phoslock (3.3%). While, when the La/P molar ratio increased to 3:1, the TDP removal rates by LAH-1/30 and Phoslock were 33.3% and 30.0%, respectively. The SRP removal rates by LAH-1/30 were 81.0% (La/P molar ratio 0.5:1) and 91.9% (La/P molar ratio 3:1). The application of LAH-1/30 has little effects to the concentrations of TDN, NH4+ -N, and NO3- -N. The Al 3+ dissolution rate of LAH-1/30 was lower than that of Phoslock, while the La3+ dissolution rate was a little higher compared to that of Phoslock. The DOC removal rate by LAH-1/30 was 55.7% as the La/P molar ratio of 3:1.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/38715
Appears in Collections:环境纳米材料研究室_学位论文

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Recommended Citation:
徐睿. 新型镧铝复合固磷剂的制备及其应用基础研究[D]. 北京. 中国科学院大学. 2017.
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