Effects of low temperature on aluminum(Ⅲ) hydrolysis:Theoretical and experimental studies

In this study,the effects of low temperature on aluminum(Ⅲ)(Al)hydrolysis were examined both theoretically and experimentally by constructing a solubility diagram for amorphous aluminum hydroxide(Al(OH)_3(am))and a distribution diagram of hydrolyzed Al species.First,thermodynamic data of Al species at 4℃were calculated from that at 25℃.A well confirmed polymeric Al species, AlO_4Al_(12)(OH)_(24)~(7+)(Al_(13)),was involved in building the diagrams and,correspondingly,the non-linear simultaneous equations ...     

纳米Al13的分离方法及混凝效果动态过程的研究

以相同Al13含量、不同浓度的PAC为原料,利用乙醇-丙酮混合溶剂法、SO4^2-／Ba^2 沉淀置换法以及柱层析法分离提纯纳米Al13形态,同时利用Al-Ferron逐时络合比色法、^27Al-NMR等多种现代分析手段进行分析鉴定,比较其分离效果,并采用烧杯实验法和透光率脉动检测技术对Al13形态以及PAC、AlCl3的絮凝效果及絮凝过程中絮集物形成和增长的变化差异作了对比性研究．实验结果表明,乙醇．丙酮混合溶剂法对Al13分离纯化效果最好,分离所得Al13平均粒径大,聚合程度高．柱层析法受柱体积的影响只对低浓度的PAC有较好的分离效果;SO4^2-／Ba^2 沉淀置换法虽具有较好的分离效果,但分离过程有其他杂质离子的加入,影响到产品品质．混凝效果和动态实验结果表明,Al13形态是在絮凝过程中起电中和作用的主要形态,具有较强的除浊及脱色能力,在混凝过程中当絮体受到剪切力的破坏时Al13形态比PAC和AlCl3具有更强重新絮凝的能力．     

化学沉淀分离-置换法提纯Al13的工艺研究

采用AlCl₃溶液和Na₂CO₃粉末在不同温度下制备了不同浓度的聚合氯化铝(PACl). 以选定的中等浓度、高Al₁₃含量的PACl为原液,研究了Al₁₃与硫酸盐沉淀反应过程中SO₄/Al摩尔比、反应体系起始总铝浓度的影响以及Al₁₃硫酸盐与Ba(NO₃)₂置换反应过程中的Ba/SO₄摩尔比、超声、温度等因素的影响. 实验结果表明,在制备温度为50℃条件下,浓度在0.4～0.6　mol/L范围的PACl含有较高的Al₁₃. 沉淀分离反应的最佳SO₄/Al摩尔比为0.6∶1;生成的 Al₁₃硫酸盐沉淀物为正四面体状晶体. 在Al₁₃硫酸盐与Ba(NO₃)₂溶液置换反应过程中,Ba/SO₄的最佳摩尔比为1∶1,反应温度及超声作用对置换反应的影响较小;提高Ba(NO₃)₂的起始浓度可以得到相应较高浓度的纯化Al₁₃溶液. 所得Al₁₃纯度的统计平均值为92.1％.     

聚合氯化铝中Al_(13)形态水解稳定性的研究

采用聚丙烯酰胺凝胶柱层析法分离纯化聚合氯化铝(PAC)中的Al13形态,并采用Al-Ferron逐时络合比色法对比研究了Al13形态、PAC和Al13三种样品水解稳定性。研究结果表明Al13形态无论是对于稀释倍数、介质的pH值和水解时间都具有较高的水解稳定性,是给水和废水处理中的一种较为有效的Al形态。     

沸石强化A/O同步脱氮除磷工艺的生物-化学除磷研究

沸石强化了生物硝化作用,但回流的硝酸盐在A段抑制了聚磷菌释放磷,使生物脱氮工艺无除磷效果,需要化学除磷。铝盐和铁盐均具有很好的化学除磷效果,且与投加位置无关。当按磷与铝的摩尔比1∶1.5投加Al2(SO4)3·18H2O时,磷的去除率在85%以上;当按磷与铁的摩尔比1∶1投加FeSO4·7H2O时,磷的去除率在80%以上;当在A段投加20mgLFeSO4·7H2O和30mgLAl2(SO4)3·18H2O混合除磷剂能去除沸石强化AO生物脱氮工艺90%左右的磷,使磷达到出水排放标准。     

聚合氯化铝中纳米Al13形态的分离纯化及形态表征

采用超滤法和层析法分离纯化聚合氯化铝(PAC)中的Al₁₃形态,并采用Al-Ferron逐时络合比色法、²⁷Al-NMR、TEM和粒度测定仪对分离纯化所得的Al₁₃形态进行了分析和表征.研究结果表明,超滤法分离纯化的效果受超滤膜的孔径及PAC浓度的影响,选择合适孔径的膜和PAC溶液浓度即可以获得高纯度的Al₁₃,在层析法中则随着洗脱时间延长按分子的大小依次洗脱下来,因此截取中间组分即可得到Al₁₃;Al-Ferron逐时络合比色法和²⁷Al-NMR的分析结果表明,采用上述2种方法分离提纯得到的样品中Al₁₃的含量分别可达到90%以上和100%.TEM和粒度测定结果表明,在B=2.5的PAC溶液中,Al₁₃极少以Al₁₂AlO₄(OH)₂₄(H₂O)⁷⁺₁₂的单体形态存在,而是呈两维结构的线性和枝状的聚集体,Al₁₂AlO₄(OH)₂₄(H₂O)⁷⁺₁₂的聚集体尺寸通常在几十至几百nm.     

初始pH值对连续投加铝盐混凝去除小分子有机物的影响机制

以污水厂二级出水中小分子有机物强化混凝去除为目的,提出了连续投加混凝工艺(CDC),并以水杨酸为模型小分子有机物,研究了初始pH值对CDC工艺去除效果的影响以及铝离子与水杨酸的络合特性.结果表明,初始pH值6时CDC工艺的去除率最高,比常规混凝工艺提升了13.8%.但是初始pH值5和7时CDC工艺的提升效果较小.三维荧光结果表明,不同pH值下水杨酸和铝离子的络合特性不同.X射线光电子能谱和电喷雾质谱结果表明,pH值5时CDC工艺前期主要生成1:1络合物Al(OH)(C₇H₄O₃)(H₂O)₂.其络合作用强烈,稳定性较高,难以从水中去除.pH值6时前期主要生成中等聚合铝(如原位Al₁₃),其与水杨酸形成的络合物可以参与到铝离子的生长过程,最终生成表面崎岖形态松散的珊瑚礁状絮体,强化了水杨酸的去除.pH值7时,主要生成不定形氢氧化铝,通过絮体表面吸附小分子有机物.     

Variation on leaching behavior of caustic compounds in bauxite residue during dealkalization process

Bauxite residue, a byproduct of alumina manufacture, is a serious environmental pollutant due to its high leaching contents of metals and caustic compounds. Four typical anions of CO₃^2?, HCO₃^?, Al(OH)₄^? and OH^? (represented caustic compounds) and metal ions (As, B, Mo and V) were selected to assess their leaching behavior under dealkalization process with different conditions including liquid/solid ratio (L/S ratio), temperature and leaching time. The results revealed that washing process could remove the soluble composition in bauxite residue effectively. The leaching concentrations of typical anions in bauxite residue decreased as follows: c(CO₃^2?) > c(HCO₃^?) > c[Al(OH)₄^?] > c(OH^?). L/S ratio had a more significant effect on leaching behavior of OH^?, whilst the leaching concentration of Al(OH)₄^? varied larger underleaching temperature and time treatment. Under the optimal leaching, the total alkaline, soluble Na concentrations, exchangeable Ca concentrations were 79.52, 68.93, and 136.0 mmol/L, respectively, whilst the soluble and exchangeable content of As, B, Mo and V in bauxite residue changed slightly. However, it should be noted that water leaching has released metal ions such as As, B, Mo and V in bauxite residue to the surrounding environment. The semiquantitative analysis of XRD revealed that water leaching increased the content of gismondine from 2.4% to 6.4%. The SEM images demonstrated the dissolution of caustic compounds on bauxite residue surface. The correlation analysis indicated that CO₃^2? and HCO₃^? could effectively reflect the alkalinity of bauxite residue, and may be regarded as critical dealkalization indicators to evaluate alkalinity removal in bauxite residue.     

酸性溶液中铝-氟反应动力学

研究了酸性溶液中铝氟反应的动力学，结果表明，铝氟之间的反应速率随温度和ｐＨ的升高而增加．低ｐＨ下以Ａｌ３＋＋Ｆ－＝ＡｌＦ２＋反应为主，较高ｐＨ下由于ＡｌＯＨ２＋参与反应及ＯＨ－的催化作用，反应速率加快．在铝的浓度比氟过量１０倍的情况下，铝氟之间的反应可以用一级反应动力学方程来拟合，即为假一级反应．当ｐＨ＜３８时，柠檬酸和草酸的存在使反应速度加快，而当ｐＨ＞３８时，有机酸使铝氟反应速度变慢．有机酸在不同的ｐＨ下存在不同的作用机制．     

Effect of in-situ formed Al hydrates through long-term aging on enhanced particle destabilization by PACl coagulation

Aging of polyaluminum chloride (PACl) coagulants could significantly influence hydrolyzed Al speciation ruling coagulation performance. The goal of this study was to investigate Al species transformation through long-term aging and its impact on coagulation performance. Two kinds of commercial coagulants (PACl-1 and PACl-2) were stored for in-situ aging tests in six months to evaluate Al species variation with time and the performance of coagulation with natural turbid waters. The results showed that CaSO₄ precipitation easily occur in a commercial PACl coagulant with time as it contains SO₄^2? and Ca²⁺. It also activates the precipitation of gibbsite Al(OH)₃ in PACl with aging. Through 180 days aging, both monomeric Al (Al_a) and polymeric Al (Al_b) substantially transform into colloidal Al (Al_c) and precipitated for both PACl coagulants. At low turbidity (10 NTU), PACl-1 has a superior turbidity reduction rate than PACl-2, while PACl-2 performs a little better turbidity reduction at high turbidity (1000 NTU) regardless of aging time. With aging time, an obvious decrease in turbidity reduction for PACl-1 coagulation is observed at low turbidity of 10 NTU, while the improvement in turbidity reduction for PACl-2 coagulation by enhanced sweep flocculation can be achieved as Al_b mostly transform into Al_c after 150 days aging. It is concluded that dominant in-situ formed Al_c after a long time hydrolysis can improve PACl coagulation efficiency in turbidity reduction by enhanced sweep flocculation, especially for low turbidity water, but the increase in preformed Al_c in PACl would worsen particle destabilization after aging.     

Quantitative model for species distribution of hydroxy polyaluminum chloride

ＱｕａｎｔｉｔａｔｉｖｅｍｏｄｅｌｆｏｒｓｐｅｃｉｅｓｄｉｓｔｒｉｂｕｔｉｏｎｏｆｈｙｄｒｏｘｙｐｏｌｙａｌｕｍｉｎｕｍｃｈｌｏｒｉｄｅＦｅｎｇＬｉ，ＬｕａｎＺｈａｏｋｕｎ，ＴａｎｇＨｏｎｇｘｉａｏＲｅｓｅａｒｃｈＣｅｎｔｅｒｆｏｒＥｃｏＥｎｖｉｒ...     

光助非均相芬顿体系中羟基自由基的荧光光谱法测定与影响因素研究

以TiO2/Al2O3为载体制备了Fe2O3/TiO2/Al2O3催化剂,建立了三相流化床光助非均相芬顿反应体系.选取香豆素为羟基自由基捕获剂,采用荧光法检测光助非均相芬顿反应体系中产生的活性中间体,发现在体系中有高活性的羟基自由基生成.实验讨论了溶液的pH值、H2O2投加量、催化剂投加量、光强对光助非均相芬顿反应体系中羟基自由基生成量的影响.结果表明,以香豆素为羟基自由基捕获剂的实验方法可以较好地检测不同实验条件下光助非均相芬顿反应体系中产生的羟基自由基,且该光助非均相芬顿反应体系中羟基自由基的生成在30 min内符合零级反应动力学.溶液的pH值、H2O2投加量、催化剂投加量、光强均对反应体系中羟基自由基的生成存在一定的影响.     

Preferential binding between intracellular organic matters and Al13 polymer to enhance coagulation performance

Coagulation is the best available method for removing intracellular organic matter (IOM), which is released from algae cells and is an important precursor to disinfection by-products in drinking water treatment. To gain insight into the best strategy to optimize IOM removal, the coagulation performance of two Al salts, i.e., aluminum chloride (AlCl₃) and polyaluminum chloride (PACl, containing 81.2% Al₁₃), was investigated to illuminate the effect of Al species distribution on IOM removal. PACl showed better removal efficiency than AlCl₃ with regard to the removal of turbidity and dissolved organic carbon (DOC), owing to the higher charge neutralization effect and greater stability of pre-formed Al₁₃ species. High pressure size exclusion chromatography analysis indicated that the superiority of PACl in DOC removal could be ascribed to the higher binding affinity between Al₁₃ polymer and the low and medium molecular weight (MW) fractions of IOM. The results of differential log-transformed absorbance at 254 and 350?nm indicated more significant formation of complexes between AlCl₃ and IOM, which benefits the removal of tryptophan-like proteins thereafter. Additionally, PACl showed more significant superiority compared to AlCl₃ in the removal of < 5?kDa and hydrophilic fractions, which are widely viewed as the most difficult to remove by coagulation. This study provides insight into the interactions between Al species and IOM, and advances the optimization of coagulation for the removal of IOM in eutrophic water.     

MnO2@ Graphite电极类电Fenton降解有毒有机污染物

制备了二氧化锰复合石墨(MnO2@graphite)电极,通过XRD,TEM对电极材料进行表征,并通过电化学工作系统(循环伏安法,线性扫描伏安法,计时电量法)对MnO2@graphite电极的电催化机理进行了研究.以有机染料罗丹明B( RhodamineB,RhB)和2,4-二氯苯酚(2,4-DCP)为对象,探讨了 p...     

贵州草海沉积物纤维素氧同位素研究及其古环境意义

纤维素在湖泊沉积过程中不易发生分解,故其稳定同位素组成能真实地反映原始环境信息。本文在建立一套有效的四阶段(酸洗、碱洗、漂白及碱洗)湖泊沉积物纤维素提取基础上,成功测定了近500年草海沉积物纤维素氧同位素组成。草海纤维素氧同位素组成与董哥洞石笋恢复的降雨量的一致性变化表明纤维素氧同位素主要反映湖水氧同位素组成,进而指示了湖区降雨量变化。     

电凝聚臭氧化耦合工艺的二级出水处理特性与机理研究

构建电凝聚臭氧化耦合工艺对城市污水处理厂二级出水进行深度处理,研究了不同初始pH值、臭氧投加量和电流密度对二级出水处理效果的影响.结果表明,当初始pH值为5、臭氧投加量为1.5 mg·mg^-1、电流密度为15 mA·cm^-2时,该工艺处理效果达到最佳,二级出水中溶解性有机物的去除率可达到58.6%.与单独电絮凝和臭氧氧化工艺相比,耦合工艺对有机物有更好的去除效果.由于金属盐水解产物可以作为臭氧化的催化剂,为了甄别其活性点位,将磷酸盐引入体系中,结果表明磷酸盐占据了混凝剂水解产物表面的羟基,从而阻碍了臭氧与水解铝盐混凝剂之间的反应,使得有机物的去除率降低,傅立叶红外（FT-IR）分析的结果进一步证明表面羟基是产生的铝盐混凝剂催化臭氧化的活性点位.为了进一步明确该耦合工艺去除溶解性有机物的机理,选择对氯苯甲酸（pCBA）探针法间接证明和电子顺磁共振（EPR）实验直接证明体系中羟基自由基（·OH）的存在,结果表明,电凝聚臭氧化耦合工艺较单独臭氧氧化工艺产生了更多的·OH,说明电絮凝产生的铝盐混凝剂水解产物可以作为催化剂催化臭氧产生·OH,提升体系对有机物的去除效率.     

微波诱导催化剂Fe_2O_3/Al_2O_3制备及PEG对其活性影响

以AlCl·36H2O、FeCl·36H2O和CO(NH)22为原料,采用均匀沉淀法制备微波诱导催化剂Fe2O3/Al2O3,用X射线衍射仪(XRD)对其结构进行了表征,研究了加入聚乙二醇(PEG200)作为分散剂对产物的影响。结果表明:加入体积分数为0.05%PEG后,对于20mg/L的甲基橙模拟废水,在微波功率为900W,催化剂投加量为2g/L,处理5min后脱色率可达95.8%。     

锰电解行业铬钝化剂回收利用技术研究

以某电解锰工艺末端铬钝化废水为研究对象,采用氧化、除杂、反应制得成品,污水达标处理及回用的组合工艺,制备达到国家标准的中铬黄产品,以实现铬的回收利用。结果表明:对于H2O2氧化工艺,选用V(水样)/V(30%H2O2)为(600～1000):1;可采取加碱沉淀Mn的工艺去除杂质金属离子;铬酸铅的生成反应适宜温度为55～60℃,硝酸铅投加量为理论值的1.05倍～1.10倍;采取加石灰调pH、投加硫酸铝的方法可去除水样中剩余铅离子,V(上清液)/V(5%硫酸铝溶液)为1000～2000较合适;生产该产品基本上能够做到保本、微利,但具有显著的环境效益和社会效益。     

土壤酸化及天然土壤溶液中铝的形态

采用真空式土壤溶液采样器收集了宜昌、巫山松树林中天然土壤溶液,采用高效液相色谱法Al－Lumogallion柱后荧光检测,分析测试了土壤溶液中可溶性铝的形态,研究了由于土壤酸化引起天然土壤溶液中不同形态铝的迁移转化结果表明,天然土壤溶液中含有不同形态的铝,主要是有机铝、 AISO₄⁺、AIF₂⁺、Al（OH）²⁺、Al³⁺等．宜昌、巫山地区土壤溶液中活性铝（Al³⁺、AlOH^2+F）的含量比较低．土壤的酸化使得天然土壤溶液中总铝含量增加、铝形态的优势态发生变化,即土壤的酸化使得天然土壤溶液中活性铝－Al³⁺、AlOHF²⁺含量和比例增加．土壤酸化还降低了大然土壤溶液中的BC/Al比值,这些变化的结果都增加了对森林潜在的危害．     

基于铁泥的磁性水处理材料制备及应用进展

近年来,固体废弃物铁泥(赤泥、水处理含铁残渣和富铁污泥)已被广泛用于水环境中污染物的去除,但从水环境介质中分离粉末状铁泥的困难导致其作为水处理材料无法大规模应用,而将铁泥制备成易于分离回收的磁性材料是解决此瓶颈的有效策略之一.根据国内外现有铁泥基磁性材料的研究,总结了铁泥基磁性材料的制备方法,包括热分解法、水热与溶剂热...