【作者】 张伟；

【导师】 郑彤； 马军；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2019， 博士

【摘要】 目前,我国水环境中砷污染问题日益严重,特别是在广大农村及偏远地区常常采用地下水、地表水为直接饮用水源,一系列自然和人为因素造成了水体中存在不同程度的砷污染风险。通常,水体中砷污染以无机砷(As(Ⅴ)和As(Ⅲ))和有机砷两种形态存在,且以前者为主;无机As(Ⅲ)比无机As(Ⅴ)具有更高的毒性,更易迁移,更难被调控;对氨基苯砷酸(p-AsA)是一种典型的有机砷,近些年作为禽畜饲料添加剂被广泛使用,由于无法生物降解,导致大量p-AsA排放到自然水体中,威胁了水环境系统的安全。吸附技术被认为是最经济、高效、适合处理农村分散式砷污染的净水技术。传统的吸附材料不能很好地去除水体中的As(Ⅲ)污染物,增设预氧化工艺虽能解决这类问题,但也增加了操作难度及处理成本。此外,在某些水质使用条件与范围下,粉状吸附材料存在难分离和易板结等问题,限制了此类高效吸附材料的实际广泛应用。因此,本课题围绕(1)水体无机As(Ⅴ)、As(Ⅲ)和有机p-AsA有效去除的问题,(2)典型砷污染物在吸附材料表面的迁移转化行为及吸附机制的问题,以及(3)粉状吸附材料难分离、易板结和常规负载材料不环保、不耐碱的问题;研制了一种兼具光催化/氧化/吸附功能的复合吸附材料,并对新型多功能复合材料去除水体中典型砷污染物的效能和机制进行了系统性的探讨。本研究的第一部分首先采用氧化还原、共沉淀一步法技术构建了一种新型高效除砷铁钛锰复合氧化物(FTMO)材料。多种微观光谱检测技术(如SEM、TEM、XRD、BET和XPS)结合分析,得出FTMO材料具有较大的比表面积(434.31 m~2/g),为无定型的纳米介孔吸附材料(10-30 nm);接下来评估了FTMO吸附材料对水体无机As(Ⅴ)和As(Ⅲ)的吸附行为,研究表明,FTMO吸附材料可以快速、有效地去除溶液中As(Ⅴ)和As(Ⅲ),As(Ⅴ)和As(Ⅲ)的最高吸附容量分别为74.4 mg/g和122.3 mg/g;该材料适用的pH范围宽、选择性强,且经过8个循环实验后,FTMO材料对As的去除率仍保持在50%以上,可有效地再生与重复使用。针对FTMO吸附材料在去除水体As(Ⅴ)和As(Ⅲ)中表现的优异性能,本研究的第二部分通过宏观实验和微观检测技术,进一步系统地分析了在反应过程中不同的砷物种种类、浓度的变化,深入探究了在固/液界面上As(Ⅴ)和As(Ⅲ)与吸附材料的相互作用以及各组分材料在反应过程中各自的贡献作用。研究表明,FTMO吸附材料可以有效地将As(Ⅲ)氧化成As(Ⅴ),光照可促进As(Ⅲ)氧化及As(Ⅲ)去除效能。As(Ⅴ)的去除机制主要是As(Ⅴ)与材料表面的羟基发生配体交换作用,在固/液界面形成稳定的内配位表面络合物。As(Ⅲ)去除机制为光催化氧化、氧化还原与吸附相耦合的作用方式;材料中的Ti和Mn组份主要起到了As(Ⅲ)氧化作用,材料中的Fe组份主要起吸附作用。此外,体系中各组分的协同作用可有效提高组分材料的性能及FTMO材料对As(Ⅴ)和As(Ⅲ)的去除效能。除了无机砷,水体中砷污染还常以有机砷的形态存在,对氨基苯砷酸(p-AsA)是一种典型的有机砷,被广泛地应用于禽畜饲料添加剂中。本研究的第三部分研究了FTMO吸附材料对有机p-AsA的去除效能,并运用Zeta电位技术、傅里叶变换红外光谱技术(FTIR)、高效液相色谱-三重四级杆质谱联用仪技术(HPLC/ESI-QqQMS)、电子顺磁共振(EPR)技术、X射线光电子能谱学技术(XPS)和X射线吸收近边结构技术(XANES)等微观检测技术相结合的方法,系统地探究了在固/液界面上p-AsA分子与材料各组份间的相互作用及机制。结果表明,FTMO吸附材料可快速、有效地去除水体中的有机p-AsA污染物,p-AsA的最大吸附量为45.6 mg/g;FTMO吸附材料对p-AsA的去除机制为一种吸附为主,氧化为辅的相耦合的作用方式;在固/液界面上p-AsA分子与材料表面的羟基发生配体交换,形成了稳定的内配位表面络合物,其中部分固定的p-AsA分子在氧化/光催化氧化作用下,生成p-AsA自由基,进而耦合成含肼键的中间产物及其他氧化产物,且并无高毒性的无机As的产生;FTMO吸附材料中的Fe和Ti组份主要起吸附作用,材料中的Ti和Mn组份主要发挥氧化作用,体系中各组分的协同作用有效地提高了p-AsA污染物的去除效能。粉末状FTMO吸附材料虽然对水体中砷污染物有很高的吸附容量,但在某些水质使用范围内粉状材料存在难分离、易板结等问题;此外传统负载材料存在二次污染、不耐碱的问题。本研究的第四部分研制了一种壳聚糖负载的铁钛锰复合氧化物(FTMO/chitosan)颗粒型材料,并系统地研究了颗粒型FTMO/chitosan吸附材料对水体中无机As(Ⅴ)和As(Ⅲ)的去除行为。结果表明颗粒型FTMO/chitosan吸附材料呈均匀的多孔颗粒状,表面由许多纳米级粒子团聚而成;FTMO/chitosan可以快速、有效地去除溶液中As(Ⅴ)和As(Ⅲ),As(Ⅴ)和As(Ⅲ)的最大吸附量分别为16.2 mg/g和22.6 mg/g;颗粒型FTMO/chitosan吸附材料可以有效地再生与重复使用;动态连续流实验中,FTMO/chitosan材料分别可以安全处理2000个柱体积的As(Ⅲ)和1650个柱体积的As(Ⅴ);且在20多天的连续运行试验中,FTMO/chitosan材料外貌完整,有稳定的机械强度。说明颗粒型FTMO/chitosan材料是一种可行的、有潜力的除砷吸附材料。更多还原

【Abstract】 At present,arsenic contamination is increasingly serious in China.Especially,groundwater and surface water are often applied as direct water sources in the rural and remote region of our country.A series of natural and anthropogenic factors have caused significant arsenic contamination problems in the provision of safe drinking water.The commonly existing species of As in natural waters are inorganic arsenic and organic arsenic.Inorganic arsenic(As(Ⅴ)and As(Ⅲ))is the predominant form of arsenic.Compared to inorganic As(Ⅴ),inorganic As(Ⅲ)is more mobile,toxic and difficult to be removed.p-arsanilic acid(p-AsA)is a typical phenylarsonic acid compound,which is widely used as an animal feed additive.The compound is barely metabolized in the animal bodies and is almost completely excreted into the natural water via manure and urine,causing concerns of environmental pollution and posing human health risk.Adsorption is considered to be the most economical and efficient water purification technology for the treatment of rural dispersed arsenic pollution.These traditional adsorbents are highly effective for As(Ⅴ)and p-AsA removal,but fail in the case of As(Ⅲ).To achieve higher removal efficiency,an oxidation pretreatment is adopted prior to adsorption,which results in a complicated operation with high cost.In addition,the difficulties encountered in separating spent adsorbent and propensity to aggregate limit the application of power materials in water treatment under some conditions and ranges of water quality.Development of a novel adsorbent which could efficiently remove As(Ⅴ),As(Ⅲ)and p-AsA and overcoming the difficulties encountered in separating and regenerating spent powdered materials in water treatment were the primary objectives of this study.Moreover,a systematic investigations including optimization of preparation,characterization of adsorbent,evaluation of adsorption performance,and arsenic removal mechanisms were investigated in the current work.In the first section of this work,a novel nanostructured Fe-Ti-Mn composite oxide(FTMO)was synthesized via a simultaneous oxidation and co-precipitation method and was systematically characterized by various techniques.Meanwhile,we evaluated the arsenic removal performance of the FTMO adsorbent.The results showed that the adsorbent(10-30 nm)was amorphous or poorly crystallized with a high specific surface area of 434.3 m~2/g.The adsorbent could effectively and rapidly remove inorganic arsenic,and the maximal adsorption capacities for As(Ⅴ)and As(Ⅲ)at 25°C were 74.4mg/g and 122.3mg/g,respectively.The arsenic removal process was exothermic and spontaneous,and the adsorbent was effective for As(Ⅴ)and As(Ⅲ)removal across a wide pH range.Besides,more than 50%of its original arsenic removal percentage was still maintained for both As(Ⅴ)and As(Ⅲ)after 8 times of regeneration,and the FTMO material could be effectively regenerated and used repeatedly.The FTMO material had an excellent arsenic adsorption performance.In the second section,batch control experiments were carried out with the use of series of spectroscopy detection technologies to investigate the oxidation state change of arsenic and material elements and the respective role of Fe,Ti and Mn content in the arsenic adsorption process.The results showed that the material could effectively oxidize As(Ⅲ)to As(Ⅴ)and light illumination could further apparently enhance the oxidation and removal efficiency of As(Ⅲ).The As(Ⅴ)adsorption mechanism was mainly achieved through the replacement of the surface hydroxyl group and the formation of inner-sphere surface complexes at the water/oxide interface.However,the As(Ⅲ)removal mechanism was a photooxidation,oxidation coupled with adsorption approach;the Ti and Mn contents were dominant for the As(Ⅲ)oxidation,while the Fe content mainly played an important role for the adsorption of newly formed As(Ⅴ).Furthermore,some synergistic effect in the composite oxide system might also enhance both the performance of component materials and the overall arsenic adsorption capacity.Except for inorganic arsenic,organic arsenic is the commonly available species of arsenic in natural waters.p-arsanilic acid(p-AsA)is a typical phenylarsonic acid compound,which is widely used as an animal feed additive.The third section of the current work focused on evaluating the p-AsA removal performance of the FTMO adsorbent.In addition,series of spectroscopy detection technologies such as Zeta,FTIR,HPLC/ESI-QqQMS,EPR,XPS and XANES,were used to investigate the respective role of Fe,Ti and Mn content and the removal mechanism in the p-AsA adsorption process.The results showed that the FTMO adsorbent could effectively and rapidly remove p-AsA,and the maximal adsorption capacity for p-AsA was 45.6 mg/g.The p-AsA removal mechanism was an adsorption coupled with oxidation approach.The p-AsA molecules were primarily adsorbed onto the surface of the adsorbent via replacing the surface hydroxyl group,and then forming the inner-sphere surface complexes.Parts of adsorbed p-AsA molecules were oxidized by Mn and Ti content to produce a p-AsA radical intermediate.The p-AsA radical intermediate could be further transformed through radical-to-radical couping to form a hydrazo intermediate and other oxidation products.The Fe and Ti content mainly played an important role for the p-AsA adsorption,while the Ti and Mn contents were dominant for the p-AsA oxidation.Powdered FTMO material has an excellent adsorption performance for arsenic pollutants,but the difficulties encountered in separating spent adsorbent and propensity to aggregate limit its applications under some ranges of water quality.In addition,the traditional loading granular materials have the problem of secondary pollution and no alkali resistance.In the fourth section of this research,a novel adsorbent of FTMO impregnated chitosan bead(FTMO/chitosan)was fabricated and was systematically evaluated the arsenic removal performance.The results showed that the FTMO/chitosan material was sphere-like and was aggregated from heterogeneous nanosized particles.The prepared FTMO/chitosan was effective at removing both As(Ⅴ)and As(Ⅲ)and the maximal adsorption capacities are 16.2 and 22.6 mg/g,respectively.The arsenic-loaded FTMO/chitosan could be effectively regenerated and reused.In dynamic continuous flow experiments,about 2000 and 1650 bed volumes of simulated groundwater containing about 200μg/L As(Ⅲ)and As(Ⅴ)were respectively treated before breakthrough.The FTMO/chitosan material had complete appearance and stable mechanical strength in more than 20 days of continuous operation tests,indicating that it was a promising candidate for arsenic removal from real drinking water.更多还原