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题名: 凝聚-吸附去除饮用水中典型有害阴离子的应用研究
作者: 何赞
学位类别: 博士
答辩日期: 2015-05
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 刘会娟 ; 曲久辉 ; 刘锐平
关键词: 除锑,砷锑竞争吸附,除氟,混凝,吸附,铝氟络合,Sb removal, the competitive adsorption of As and Sb, fluoride removal, coagulation, adsorption, Al-F complexation
其他题名: The removal of typical toxic anions from drinking water by coagulation and adsorption and its application
学位专业: 环境工程
中文摘要:      特殊污染物控制是饮用水领域的重要研究内容,砷、锑、氟等是饮用水源中常见的有毒阴离子,如何有效去除控制上述污染物是国内外高度关注的难题。
    天然水体中砷主要以  As(III)和  As(V)的形式存在,电中性  As(III)较电负性As(V)更难去除,将As(III)氧化为As(V)再通过后续吸附工艺去除,这是饮用水除砷的最佳去除策略。铁锰复合氧化物可实现  As(III)和 As(V)的同时一步去除。锑和砷为同族元素,二者有不少相似的化学性质。但研究显示,Sb(III)较Sb(V)更容易去除,锑的最佳去除策略为还原-吸附,但在工程层面上实现 Sb(V)还原非常困难。因此,开发高效除锑吸附材料尤为必要。为此,本研究以铁盐原位水解反应为基础制备了具有巨大比表面积和丰富吸附位点的吸附剂 in-situ FeOxHy。研究显示,in-situ  FeOxHy 可同时高效去除 Sb(III)和 Sb(V),且二者在其表面均主要生成内层络合物。在  pH=5 时其对  Sb(III)和  Sb(V)的最大吸附容量分别为12.77 mmol/g和  10.21 mmol/g,且 Freundlich模型能够很好的描述其吸附过程。在 pH为  3-10范围内,Sb(V)吸附量随着  pH升高而降低而  Sb(III)吸附量却增加,这主要是由二者的主要形态带有相反的电荷所致。硫酸盐和碳酸盐对二者的吸附影响不大,磷酸盐显著抑制 Sb(V)的吸附但对 Sb(III)吸附影响很小。连续流动态试验证实了 in-situ  FeOxHy工程应用的可行性,其平衡吸附容量为  1  mg/g,pH和载体大小为其主要工艺控制参数。
    国内外对具有相似化学性质的砷和锑在共存体系下的竞争吸附行为研究较少。研究显示,二者在共存体系存在复杂的竞争吸附行为,且不同形态砷锑之间的竞争作用有明显不同。具体而言,不同形态的砷和锑在羟基氧化铁上发生竞争吸附时,二者吸附量均较单一体系发生不同程度下降。就吸附速率而言,Sb(III)会降低  As(III)的吸附速率,而   As(III)会提高  Sb(III)的吸附速率;Sb(V)会提高As(III)的吸附速率,而 As(III)会降低 Sb(V)的吸附速率;As(V)和 Sb(V)均能促进彼此的吸附速率;As(V)会提高 Sb(III)的吸附速率,而  Sb(III)会降低  As(V)的吸附速率。此外,研究发现,二者引入先后顺序和间隔时间对竞争吸附行为也有影响,二者引入时间间隔对吸附剂总的吸附量影响不大,但间隔时间越长则先引入的离子最终吸附量越大,反之后引入的离子吸附量越小。表面络合模型结果显示,As(V)和  Sb(V)在羟基氧化铁表面均形成单齿双核络合物。羟基氧化铁表面有两类羟基:一类为 As(V)和  Sb(V)共有吸附点位,二者在此吸附点位可竞争吸附;另一类为 Sb(V)的专属吸附点位。
    目标污染物与吸附剂之间的相互作用将对彼此的形态产生影响,进而显著影响污染物去除性能,但国内外对此关注较少。以铝盐除氟过程为基础,系统研究了基于铝盐凝聚与吸附过程的铝、氟形态相互作用,并在此基础上研究了铝盐混凝和 in-situ  Al2O3•xH2O吸附除氟性能与机制。研究显示,铝盐混凝除氟效果优于 in-situ Al2O3•xH2O吸附,实现某实际高氟地下水达标的铝投量分别为 30和  160mg/L,且最佳 pH 范围均为 6-7。在混凝除氟过程中铝盐水解消耗水中碱度,并发生了自由态氟向络合态氟的转化,且提高铝投量可促进络合态氟的形成;对比而言,吸附过程中络合态氟生成量很少。氟离子的存在会影响铝离子水解,并可有效促进溶解态铝离子和铝氟络合体向颗粒态沉淀的转化。另一方面,铝氟络合作用会促进 in-situ Al2O3•xH2O铝离子的溶出和释放,且在酸性  pH和高氟铝比条件下更为显著。这降低了可用于吸附除氟的有效 in-situ  Al2O3•xH2O沉淀含量,进而对氟的去除产生不利影响。现场中试试验证实,铝盐混凝除氟优于in-situAl2O3•xH2O吸附除氟,氟达标的平衡吸附量分别为  85.2和25.1 mg F/g Al;铝氟络合体生成对于混凝除氟表现出更佳的除氟性能具有重要作用。
    受地球环境化学的作用,有时会出现砷氟共存现象。应用 in-situ Al2O3•xH2O同时去除砷氟结果显示, 铝氟络合作用和氟吸附到 in-situ Al2O3•xH2O表面降低的  zeta 电位会降低 As(V)的吸附,而  As(III)的去除受氟的影响很小。电负性的As(V)对氟吸附的抑制作用要远远大于 As(III)。
    铁、铝盐凝聚与原位生成的金属氧化物吸附可有效去除水中砷、氟、锑等有害阴离子,而污染物与絮凝剂、吸附剂之间的相互作用对其去除有重要影响。
英文摘要:     The removal  of typical  pollutants is  one of the  most important  study areas  in the drinking water, and arsenic, antimony and fluoride are the common toxic anions in the drinking water  source. Therefore,how to  effectively control the  above pollutants is highly concerned by the researchers at home and abroad.
    In natural water, As  mainly exists in the inorganic forms  of As(III) and As(V), and electroneutral  As(III)  is more  difficult  to  be  removed than  the  negatively  charged As(V). The  optimum  removal route  of arsenic  in water  is oxidized  firstly  and then adsorbed, and Fe-Mn Binary Oxide can achivie a step efficient removal  of As(III) and As(V). Arsenic  and antimony locate  in the  same group in  the elements periodic  and have  the  similar  chemical  property whereas  researches  indicate  that  the  optimum removal route  of  antimony is  reduced firstly  and adsorbed  afterward. However,  the above  process  is difficult  to  be  achieved  in  the actual  engineering,  and  thus  it  is another  essential  path  to  look  for   an  adsorbing  material  for  removing  antimony effectively. For this aim,  this study successfully prepared a novel  adsorbent with high specific surface area and adsorptive activity, i.e., in-situ FeOxHy. This  study indicated that in-situ  FeOxHy can effectively  remove Sb(III)  and Sb(V), and  the formation  of inner-sphere complexes  was involved between  Sb and  the adsorbent. The  maximum adsorption  capacity  of  Sb(III)  and  Sb(V)  was  determined  to  be  12.77 and10.21mmol/g  as  Fe,respectively,  at  pH  of   5  and  Freundlich  model   was  better  than Langmuir model to describe the adsorption of Sb(III) and Sb(V). Adsorption  of Sb(V) decreased whereas that of  Sb(III) increased with elevated pH  over pH 3-10, owing  to the different electrical  properties of Sb(III) and  Sb(V). Sulfate and carbonate  showed little effect  on the adsorption  of Sb(III) and  Sb(V). Phosphate  significantly inhibited the   adsorption  of   Sb(V),  whereas   slightly   affected  that   of   Sb(III).  Pilot-scale continuous  experiment indicated  the feasibility  of  using in-situ  FeOxHy  to remove Sb(V) and the equilibrium adsorption capacity  at the equilibrium Sb(V) concentration of 10 μg/L was determined  to be 1 mg/g, and  pH and good porosity was  essential for removing Sb.
   The  competitive adsorption  of As  and  Sb is  rare  to be  studied.  The competitive adsorption kinetic  of  different species  As and  Sb on  iron  hydroxides indicated  that they  affected   the  adsorption  of   each  other.   In  term  of   adsorption  rate,  Sb(III)decreased the  adsorption rate of  As(III) whereas  As(III) increased of  that of Sb(III);Sb(V) favored the  adsorption rate of  As(III) whereas As(III)  inhibited that of  Sb(V);As(V)  and  Sb(V)  elevated  the  adsorption  rate  of  each  other;  As(V)  favored   the adsorption  rate  of  Sb(III)  whereas  Sb(III)  inhibited that  of  As(III).  The  effect  of adding time of the competitive  ion on the first ion added  showed that the adding time barely affect  the  total adsorption  capacity of  the adsorbent,  and  the time  of adding competitive  ion is  later,  the adsorption  capacity  was higher  for  the first  ion  added whereas  it  was smaller  for  the  competitive  ion.  The results  of  surface  complexes model  indicated  that  the  formation  of  monodentate  binuclear  complexes  between As(V) or Sb(V) and iron hydroxides. Iron  hydroxides has surface sites into two types: ones to which both As(V) and Sb(V) adsorb and a smaller number to which only Sb(V) binds.
    The  interaction  between  the targeted pollutant  and  the  adsorbent  will  affect  the species  of  each   other  and  show  significant   effect  on  the  removal   of  pollutants afteraward. The mutual  effect between Al  and F in the  fluoride removal by  Al-based coagulation  and  adsorption  was  systematically investigated  in  this  study,   and  the removal  property  and  mechniasm  of  fluoride  by  Al-based  coagulants  and  in-situ
Al2O3•xH2O adsorbent  was also conducted. The  results indicated that  Al coagulation showed  superiority  to   remove  flruoride  than  Al   precipitate  did.  To  achieve   the maximum contaminant level (MLC) of fluoride (<1 mg/L) in drinking water standard,the optimum  Al  doses were  determined to  be 30  and 160  mg/L in  coagulation and
adsorption process  for the  actual  underground water,  respectively, and  the optimum pH for the  fluoride removal was  pH of 6-7. In  the coagulation system,  the formation of complexed  fluoride occurred  and it  was elevated with  the increasing  of Al  doses whereas  it  barely  occurred   in  the  adsorption  system.  Fluoride   affected  the  Al3+ hydrolysis  and contributed  to  the  transformation of  Al3+  and  Al-F  complexes into precipitate.  However,  the complexed  reaction  between  Al  and  fluoride caused  the dissolution of in-situ Al2O3•xH2O, which was most important at low pH and high ratio of fluoride to Al conditions, and reduced the precipitate available for fluoride removal afterwards. Pilot-scale  filed  experiment indicated  that Al-based  coagulation showed better fluoride removal than adsorption did, and the equilibrium adsorption capacity at the equilibrium fluoride  concentration of 1 mg/L was determined  to be 85.1 and 25.1 mg F/g Al, respectively. The formation of Al-F complexes was important for the better removal of fluoride by Al coagulantion.
    In some cases with special  geochemical conditions, the simultaneous occurrence of As and  F  is observed.  The simultaneous  removal  of As  and F  was  investigated by in-situ Al2O3•xH2O  adsorption, and the  results indicated that  the reduced removal  of As(V)  was  observed owing  to  the  Al-F  complexed  reaction  and the  reduced  zeta
potentian  of  in-situ  Al2O3•xH2O  after  adsorping  fluoride  whereas  the  removal  of As(III) was  rarely affected by the  coexisting fluoride. The  negatively charged As(V) showed higher inhibitive effect on fluoride than As(III).
    Arsenic,  antimony,  and  fluoride can  be  effectively  removed  by  Al  or  Fe-based coagulants  and  the   in-situ  formed  metal  oxide,  and   the  interaction  between  the pollutants and coagulants or adsorbents showed significant effect on their removal.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34330
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何赞. 凝聚-吸附去除饮用水中典型有害阴离子的应用研究[D]. 北京. 中国科学院研究生院. 2015.
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