载镧生物炭的优化制备及其对水体中砷的吸附

以玉米秸秆为原材料优化制备用于吸附水体中五价砷的载镧生物炭(La-biochar),对其表面进行了系统表征,同时考察了环境条件对载镧生物炭吸附性能的影响.结果表明:相比负载前生物炭,负载后生物炭表面更粗糙,比表面积增大4.6倍,同时表面成功负载有大量镧元素.以获取对五价砷的最大吸附能力为目的,通过响应面模型获得La-biochar的优化制备条件为:物料比w(La)/w(秸秆)=9.47%,停留时间=20min,热解温度=300oC.中性和酸性环境条件有利于La-biochar对砷酸根的吸附,而碱性条件则有不利影响;较高浓度的CO32-显著降低其对砷酸根吸附,而同样浓度的Cl-和F-不会造成明显影响.     

镧铁羟基氧化物修饰还原氧化石墨烯复合电极材料电吸附除磷效能及机理研究

污水处理厂尾水中低浓度PO₄^3-的排放是水体中总磷的主要来源,是导致水体富营养化的重要原因之一,对其开展深度去除的应用基础性研究具有重要的理论意义和实践价值.复合金属氧化物材料表现出较好PO₄^3-吸附能力,但仍然存在吸附速率较慢的问题.本研究采用溶剂热、复合薄膜压片法制备了镧铁羟基氧化物（LaFeO_xH_y）修饰还原氧化石墨烯（rGO）复合电极材料（LaFe-rGO）,LaFe-rGO复合电极材料显著提高了对PO₄^3-的吸附速率,5 min可达到吸附平衡,在1.2 V电压下对PO₄^3-的最大吸附量为108.69 mg·g^-1.提出了基于晶格氧提供活性位点及LaFe-rGO双电层电容电促吸附除磷机理,LaFe-rGO复合电极材料中晶格氧La-O与Fe-O同时对PO₄^3-吸附提供吸附位点,PO₄^3-与材料中的La/Fe键合以形成内球表面复合物La/Fe-PO₄,掺杂在rGO表面上的LaFeO_xH_y增加了电极材料电容并提高了其电化学活性,促进了LaFe-rGO复合电极材料对PO₄^3-的吸附.     

Adsorption behavior of phosphate on Lanthanum（III） doped mesoporous silicates material

A series of lanthanum doped meosoporous MCM-41 (LaxM41, x is Si/La molar ratio) was prepared by sol-gel method. The surface structure of the materials was investigated with X-ray diffraction and N2 adsorption/desorption technique. The content of La in the materials was determined by ICP. It was found that the La content of La25M41, La50M41 and La100M41 was 7.53%, 3.89% and 2.32%, respectively. The phosphate adsorption capacities increased with increasing amount of La incorporation. With 0.40 g La25M41 99.7% phosphate could be removed. The effects of Si/La molar ratio, LaxM41 dose, pH, initial concentration of phosphate solution, co-ions on phosphate adsorption were also evaluated. The phosphate adsorption kinetics of LaxM41 could be well-described by the pseudo second-order model, and Langmuir isotherm fit equilibrium data much better than the Freundlich isotherm.     

氢氧化铁对砷的吸附与沉淀机理

研究了吸附反应时间为50d和1120d时,As(V)初始浓度和pH值对氢氧化铁吸附砷的影响,并利用傅利叶红外光谱(FTIR)和粉末X射线衍射技术对吸附砷后的氢氧化铁固体进行了表征.结果表明,氢氧化铁对砷的吸附能力与pH有关,在弱酸性到弱碱性条件下,吸附砷的能力最强;在低初始砷浓度(0.01～1 mmol·L-1)和相同pH条件下,吸附率随砷浓度增高而增大.当pH=3、7和12时,吸附等温线都可用Freundlich公式来进行拟合,低初始砷浓度下(0.001～1 mmol·L-1),R2>0.99,高初始砷浓度下(5～1000 mmol·L-1),R2>0.93,吸附反应时间对吸附能力影响不大.红外光谱分析表明,在pH=3条件下,初始砷浓度为50mmol·L-1和500mmol·L-1时,吸附后氢氧化铁固体的红外光谱图上As-O键的伸缩振动谱带分别位于806.11cm-1和821.54cm-1;表明吸附后的氢氧化铁表面有少量的砷酸铁晶体沉淀存在,砷在氢氧化铁表面的平均密度对砷在氢氧化铁表面存在形态有影响.X射线衍射分析表明.在中性和酸性条件下,砷可能是以双配位表面络合的质子化的=FeO2As(O)(OH)-和非质子化的=FeO2As(O)2-形态存在于氢氧化铁表面.     

吐温80与氢氧化钠耦合污泥溶胞及生物水解酸化特性研究

采用吐温80与氢氧化钠耦合进行污泥溶胞,当污泥溶胞时间为15min时,污泥上清液中蛋白质与DNA浓度较初始上清液中分别提高了32.5倍和15.8倍,显示细胞壁已得到有效破解,胞内的蛋白质与DNA溶出进入水相。而且,溶胞后污泥的水解酸化过程中挥发性脂肪酸(VFAs)和氨氮产量随着吐温80浓度的增大和酸化时间的延长而增加,这表明吐温80的加入促进了水解酸化菌对蛋白质和碳水化合物的分解。酸化进行24h时,不同条件下系统的pH均达到7.4左右,此后系统进入稳定运行阶段。     

ATR-FTIR and XPS study on the structure of complexes formed upon the adsorption of simple organic acids on aluminum hydroxide

Information on the binding of organic ligands to metal （hydr）oxide surfaces is useful for understanding the adsorption behaviour of natural organic matter on metal （hydr）oxide. In this study, benzoate and salicylate were employed as the model organic ligands and aluminum hydroxide as the metal hydroxide. The attenuated total reflectance Fourier transform infrared （ATR-FTIR） spectra revealed that the ligands benzoate and salicylate do coordinate directly with the surface of hydrous aluminum hydroxide, thereby forming innersphere surface complexes. It is concluded that when the initial pH is acidic or neutral, monodentate and bridging complexes are to be formed between benzoate and aluminum hydroxide while bridging complexes predominate when the initial pH is alkalic. Monodentate and bridging complexes can be formed at pH 5 while precipitate and bridging complexes are formed at pH 7 when salicylate anions are adsorbed on aluminum hydroxide. The X-ray photoelectron （XP） spectra demonstrated the variation of C 1 s binding energy in the salicyate and phenolic groups before and after adsorption. It implied that the benzoate ligands are adsorbed through the complexation between carboxylate moieties and the aluminum hydroxide surface, while both carboxylate group and phenolic group are involved in the complexation reaction when salicylate is adsorbed onto aluminum hydroxide. The information offered by the XPS confirmed the findings obtained with ATR-FTIR.     

Novel synthesis of aluminum hydroxide gel-coated nano zero-valent iron and studies of its activity in flocculation-enhanced removal of tetracycline

A newly designed aluminum hydroxide gel-coated nanoscale zero-valent iron(AHG@NZVI)with enhanced activity and dispersibility of NZVI was successfully synthesized.The AHG@NZVI composite was synthesized via control of the surface AHG content.AHG@NZVI-1,AHG@NZVI-2 and AHG@NZVI-3 were prepared under centrifugal mixing speeds of 1000,2000 and 4000 r/min,respectively.The activity of AHG@NZVI was evaluated by its tetracycline(TC) removal efficiency.The effects of AHG content,pH value,reaction temperature,and presence of competitive anions on TC removal were investigated.TC could be removed by both adsorption and chemical reduction on AHG@NZVI-2(centrifugal speed 2000 r/min) in a short time with high removal efficiency(≥98.1%) at the optimal conditions.Such excellent performance can be attributed to a synergistic interaction between aluminum hydroxide gel and NZVI:(1) AHG could enhance the stability and dispersity of NZVI;(2) aluminum hydroxide gel could absorb a certain amount of TC and Fe~(2+)/Fe~(3+),which facilitated the mass transfer of TC onto the NZVI surface,resulting in acceleration of the reduction rate of TC by the AHG@NZVI composite;and(3) AHG-Fe~(2+)/Fe~(3+)could absorb a certain amount of TC by flocculation.The kinetics of TC removal by AHG@NZVI composite was found to follow a two-parameter pseudo-first-order model.The presence of competitive anions slightly inhibited the activity of AHG@NZVI systems for TC removal.Overall,this study provides a promising alternative material and environmental pollution management option for antibiotic wastewater treatment.     

Highly efficient and selective removal of low-concentration antibiotics from aqueous solution by regenerable Mg(OH)2

The prevalent presence of fluoroquinolone antibiotics in aquatic environments has attracted considerable attention because of their harmful effects on humans and the ecological environment. Magnesium hydroxide nanocrystals were found to act as a simple and effective adsorbent to remove low-concentration ciprofloxacin (CIP) in aqueous solution. The as-prepared Mg(OH)₂ nanocrystals exhibited excellent CIP adsorption performance and high selectivity toward CIP molecules compared with other antibiotics or aromatics, e.g., norfloxacin (NOR) and eosin B (EB). The adsorbent showed pH-dependent adsorption, indicating that the adsorption process is probably dominated by an electrostatic interaction mechanism. In addition, structural analysis of the adsorbent indicated that coordination and hydrogen bonding between CIP and Mg(OH)₂ nanocrystal might also be involved in the adsorption process. Moreover, the adsorbent could be easily recovered by pyrolysis and hydration without significant reduction of adsorption capacity. The superior adsorption behavior of Mg(OH)₂ nanocrystal indicates that it may serve as a potential adsorbent material candidate for the selective removal of CIP from aquatic environments.     

镧对铅胁迫下小麦幼苗抗氧化酶活性的影响

在铅胁迫的条件下 ,研究了镧对小麦幼苗生长期地上部分及根系超氧化物岐化酶 (SOD)、过氧化氢酶 (CAT)的活性、脂质过氧化产物丙二醛 (MDA)的含量以及对植物生长的影响 .实验在严格控制的人工气候室进行 1 2d .Pb(NO) 3 处理量为 0 ,5 0 ,1 0 0mg·l- 1.在第二天至实验结束的研究结果表明 ,加La组与对照组比较有明显差异 ,根系的SOD和CAT各增加 0 4 5— 1 6 5倍和 32 2— 77 77% ,MDA减少 1 1 0 5—2 7 4 9% .当有铅胁迫时 ,在 0— 5d内 ,与对照组比较 ,镧使小麦幼苗的地上部分及根系的SOD和CAT有少量的但有统计学意义的增加 (p <0 0 5 ) ,MDA含量则减少 .表明La(NO3 ) 3 使抗氧化酶提高 ,增加了小麦抗铅胁迫的能力 ,但是只是在胁迫初期和胁迫不很严重的条件下 ,才具有这一作用 .     

光催化转化并回收水中农药有机磷

经溶胶-凝胶法制备不同镧（La）掺杂量的二氧化钛（TiO₂）,得到光催化转化吸附回收有机磷的复合材料.结果表明,La与TiO₂掺杂物质的量比为0.002并经过煅烧和掺杂物质的量比为0.02未经煅烧的2种材料,以6：4的比例混合,所得复合材料La@TiO₂（6：4）为粒径约13nm的锐钛矿型TiO₂,表面有球形聚集体但分布较均匀,其光谱范围较纯TiO₂发生红移,因而光催化效率提高.当有机磷浓度20mg/L、La@TiO₂（6：4）投加量为1g/L、溶液pH值为9时,有机磷回收率最高达85%.溶液中的NO₃^-、Cl^-、SO₄^2-对磷回收影响不大,CO₃^2-有抑制作用;材料经解吸后可多次重复利用.研究表明La@TiO₂（6：4）为有前景的有机磷回收复合材料.