【作者】 方继敏；

【导师】 龚文琪；

【作者基本信息】 武汉理工大学 ， 矿物加工工程， 2008， 博士

【摘要】 铁是自然界中少数常见的变价元素,铁（氢）氧化物矿物在土壤颗粒和岩石、水体沉积物中广泛存在。它们有较大的比表面积和较高的反应活性,环境相容性好,价格低廉,对重金属和有机污染物质有良好的吸附性能。五氯苯酚（pentachlorophenol,PCP）是憎水性可离解有机化合物（hydrophobicionizable organic compounds,HIOCs）的典型代表,PCP在水体中存在形态为PCP分子和PCP离子,随pH不同其存在形态不同。PCP广泛地存在于土壤、地表水和地下水,理化性质受环境pH影响存在较大的差异,环境行为复杂。目前对其环境效应及处理工艺的研究尚不深入。为深入了解土壤和水体中广泛存在的铁（氢）氧化物矿物与PCP的相互作用机理,利用铁（氢）氧化物矿物的界面作用治理土壤与水体的憎水性可离解有机化合物污染,实现廉价、安全的土壤修复和水体净化,研发铁（氢）氧化物矿物单元反应器处理有机污染物,论文在前人的研究基础上进行了α-FeOOH、α-Fe₂O₃、Fe₃O₄三种铁的（氢）氧化物制备、负载、表征及对HIOCs类污染物中代表物PCP的吸附性能研究。采用FeCl₃·6H₂O与NaOH在水溶液中的化学沉淀、40℃恒温陈化4天制备得到了α-FeOOH,通过X射线衍射、FTIR、TEM、激光粒度仪、比表面积测定、表面酸碱滴定等对制备样品进行了分析表征,并对比了天然与合成α-FeOOH的相关性能。结果表明,合成α-FeOOH的FTIR特征吸收峰为893cm^-1和796cm^-1,平均粒径为364.9nm,比表面积52m²/g,零电荷原点pH_ppzc=7.82;天然针铁矿主要成分为Fe₂O₃,其次为Al₂O₃和SiO₂,烧失量较高,除含有结晶水外还含有多糖类有机挥发份。FTIR特征吸收峰为976cm^-1和464cm^-1,微观形貌为螺旋状和管状,管径小于2μm,比表面积179.8m²/g为合成α-FeOOH的3.458倍;天然α-FeOOH零电荷原点pH_ppzc=7.18。合成与天然α-FeOOH对PCP的静态吸附性能研究表明,天然α-FeOOH吸附速率略快于合成α-FeOOH,两种FeOOH在2.5h都达到了吸附-解吸动态平衡,起始浓度为10mg/L的PCP溶液经合成与天然α-FeOOH吸附处理后,去除率分别为53.4%和61.3%。处理后PCP溶液浓度分别从（GB8978-1996）污水综合排放标准中的三级排放标准（10mg/L）达到了一级排放标准（5mg/L）。合成α-FeOOH最大吸附容量发生在pH5.5,达到0.534mg/g,天然α-FeOOH最大吸附容量发生在pH 6.0,达到0.613mg/g。造成吸附容量差异的原因在于天然α-FeOOH的比表面积比合成FeOOH的比表面积大、表面位密度高。天然与合成α-FeOOH对PCP的吸附动力学符合一级动力学,拟合的动力学方程分别为lgC=1-0.1645t和lgC=1-O.1325t;天然α-FeOOH对PCP的吸附符合Freundlich等温式;合成α-FeOOH对PCP的吸附符合Langmuir等温式;α-FeOOH吸附PCP主要作用机理为>FeOH₂⁺和C₆Cl₅O^-两者之间形成电荷-偶极以氢键形式的吸附;天然、合成α-FeOOH吸附PCP后采用500℃热再生后均相变为α-Fe₂O₃,α-Fe₂O₃对PCP吸附能力大于合成α-FeOOH,同时多次500℃热再生效果良好。天然α-FeOOH对造纸废水中有机污染物的吸附性能研究表明,天然α-FeOOH对造纸废水中的COD的吸附速度较快,60min后达到吸附平衡,当废水的COD为394mg/L时,68.89%的COD会从水相转移入固相中,当造纸废水和受纳水体混合后COD在150mg/L以下时,处理后废水的COD达到了GB3883-2002中的地表水Ⅰ类水质;吸附等温线为Langmuir型,饱和吸附量Γm为8.006mgCOD/g,吸附常数k为10.26;天然针铁矿吸附有机物后经过500℃煅烧后发生了相变,转化成α-Fe₂O₃,再生后的一次解吸率为87%,多次吸附解吸后仍然具有很高的吸附能力。采用均匀沉淀法合成了α-Fe₂O₃,经X射线衍射、FTIR、HRTEM分析证明为α-Fe₂O₃,生成的α-Fe₂O₃结晶良好,没有其他杂质,属于六方晶体结构,粒径小于300nm,比表面积37.24m²/g,零电荷原点pH_ppzc=7.65。合成α-Fe₂O₃对PCP的吸附机理研究表明,合成α-Fe₂O₃对PCP的吸附在2.5h达到吸附和解吸动力学平衡,吸附动力学符合一级动力学:适合于采用Langmuir等温方程式拟合,α-Fe₂O₃单位面积上的活性基团数量大于α-FeOOH,α-Fe₂O₃吸附PCP后在500℃灼烧60min后的再次吸附PCP效果良好,六次再生后的吸附容量保持为98.8%。最大吸附容量在pH6.0处达到6.5mg/g,吸附机理以静电吸附为主,氢键作用为辅,在零电荷原点pH7.65时,两者之间主要以氢键作用产生吸附。采用共沉淀法制备了磁铁矿,经过X-射线衍射分析合成的样品为纯度高的Fe₃O₄,按照Debye-Scherrer公式计算出平均晶粒大小为25nm,激光粒度分析结果平均粉体粒径277.2nm。Fe₃O₄对五氯苯酚吸附速率慢于针铁矿和赤铁矿,pH=5时,吸附容量达到最大为0.35mg/g,最大吸附容量小于针铁矿和赤铁矿,吸附等温线适合用Freundlich等温式拟合。α-Fe₂O₃对PCP具有良好的吸附性能,但由于它是一种松散的、易水解的、无定形的粉状物质,用做固定床、移动床反应器时透水性能极差,而用做间歇工艺流程时脱水困难,吸附剂损失大同时产生大量的污泥和额外处理费用。论文在前人将α-Fe₂O₃负载在石英砂制备滤料的基础上,首次采用共沉淀法将α-Fe₂O₃负载在比表面积大、孔隙率高、密度小的陶瓷滤球上,采用扫描电镜（SEM）、比表面积（BET）测定、X射线衍射（XRD）及高分辨透射电镜分析（HRTEM）等检测技术对负载型进行分析表征,从负载铁量、附着性能、抗酸碱能力等方面考察负载型α-Fe₂O₃的性能。以Fe（NO₃）₃.9H₂O为原料,采用尿素作为均匀沉淀剂,采用共沉淀法辅助α-Fe₂O₃负载于陶瓷滤球上。当CO（NH₂）₂与Fe（NO₃）₃.9H₂O摩尔比为1.0,Fe（NO₃）₃.9H₂O与陶瓷滤球重量比为0.2时,经600℃加热1小时,比表面积由陶瓷滤料原来的0.973m²/g增加到5.639m²/g增加了5.8倍,陶瓷滤料在零电荷原点时的pH值为5.8,负载α-Fe₂O₃后增加到7.8,负载型吸附剂α-Fe₂O₃的机械稳定性、耐酸及耐碱性能良好,机械稳定性失重率0.352%,耐酸性失重率2.387%,耐碱性失重率0.568%。负载型α-Fe₂O₃对PCP的静态吸附和粉末状α-Fe₂O₃吸附动力学过程相似,达到平衡时吸附容量为O.19mg/g,只有粉末状α-Fe₂O₃吸附容量（0.65mg/g）的29.23%;PCP去除率与负载型α-Fe₂O₃的比表面积呈现出较好的相关性,明显表现出随着比表面积增加,PCP去除率增加;负载型α-Fe₂O₃对PCP的去除随pH变化规律、吸附机理与粉末α-Fe₂O₃相似;负载型α-Fe₂O₃对PCP吸附分配比与热力学温度回归方程为lnD=2.0577/T-1.8869,吸附反应的吸附热△H=-17.1kJ/mol,为放热反应。负载型α-Fe₂O₃对PCP的动态吸附实验表明,当吸附柱装填高度30cm,EBCT（空床接触时间）分别为8min、12min、16min时,出水符合GB8978-1996一级标准的处理时间分别为271min、516min、805min,累积达标产水量12810.5ml、16211ml、18955.6ml,床积比分别为50.28BV、43BV、34BV,穿透时的吸附容量分别为静态吸附容量的83%、71%、56%。负载型α-Fe₂O₃吸附PCP后的热再生效果良好,600℃三次再生后其吸附PCP的穿透曲线几乎没有变化。为研究固定床蜂窝状α-Fe₂O₃吸附剂对PCP的吸附性能,首次利用吸氧腐蚀作用在金属铁的原位生成α-Fe₂O₃。纯铁板辅助氧气氧化的表层物x射线衍射分析表明,表层物中除了Fe₃O₄外,还出现了α-Fe₂O₃,对表层物顶层的拉曼光谱分析表明,表层物顶层的成分是单一α-Fe₂O₃;表层物中间层的主要成分是Fe₃O₄,同时含有少量γ-FeOOH和α-Fe₂O₃:SEM分析表明表面氧化物形状为树叶状,表面零电荷原点时的平均pH为7.22,铁基原位生成负载α-Fe₂O₃吸附剂对PCP的吸附平衡时间为2.5h,峰值出现在pH5.5左右,最大吸附容量为0.55mg/cm²;吸附适合于用Langmuir等温方程拟合,经过600℃灼烧1h能够获得再生,四次再生后的吸附能力为首次的98.9%。α-Fe₂O₃作为吸附剂用作HIOCs类废水PCP的吸附处理有着潜在的应用前景。更多还原

【Abstract】 Iron belongs to a common variable-valence element with a small number in thenature which widely exists in soil particles and rock, aquatic sediment. They have a larger surface area and high reactivity, environmental compatibility, low price that have a good adsorption property on heavy metals and organic contaminants.Pentachlorophenol （PCP） is a typical representative of hydrophobic ionizable organic compound （HIOCs） which widely exists in soil, surface water and groundwater, in liquid, its existing form is PCP molecule and PCP ion, and different forms by pH values. Physical and chemical properties are extremely determined by environment pH value, complex environmental behavior. At present, its environmental effects and treatment process are not in-depth yet.To better understand the interaction mechanism on PCP of iron oxide （or hydroxide） minerals which widely exist in soil and liquid, the method that use interface interaction of iron oxide （or hydroxide） mineral to treat the hydrophobic ionizable organic compound contaminants in the soil and liquid is performed, so as to realize economical and safety soil remediation and liquid purification, and develop iron oxide （or hydroxide） mineral unit reactor to treat organic contaminants. Based on the previous researches, this essay presented researches on preparations, loads and characterizations of three kinds of iron oxide,α-FeOOH,α-Fe₂O₃, Fe₃O₄, as well as the property of adsorption on PCP which is a typical representative in HIOCs contaminants.Preparedα-FeOOH by aging chemical precipitation from the solution of FeCl₃-6H₂O and NaOH for 4 days under the constant temperature 40℃, and then carried out analysis and characterization in the preparation sample through X-ray diffraction, RTIR, TEM, laser particle sizer, BET surface area, acid-base titration and so on, as well as the related compared performances between natural and syntheticα-FeOOH. The result indicated that the FTIR characteristic absorption peak for syntheticα-FeOOH were 893cm^-1 and 796cm^-1, average particle radius was 364.9nm, BET surface area was 52m²/g, point of zero charge pH_ppzc =7.82; natural goethite be mainly divided into Fe₂O₃, followed by A1₂O₃ and SiO₂, with a high loss on ignition, and besides the crystal water, it also contained polysaccharide organic volatile. The FTIR characteristic absorption peak for syntheticα-FeOOH were 976cm^-1 and 464cm^-1, the micro-morphology was presented as helical and solid tube form, the tube radius is less than 2μm, BET surface area was 179.8m²/g which was 3.458 times of syntheticα-FeOOH’s;point of zero charge of natural a-FeOOH pH_ppzc=7.18.The research on the adsorption property of synthetic and naturalα-FeOOH static on PCP indicated that, the adsorption rate of naturalα-FeOOH is slightly higher than the syntheticα-FeOOH’s, both kinds of FeOOH reach the adsorption-desorption dynamic equilibrium in 2.5 hours, after the adsorption treatment on PCP solution with the initial concentration of 10mg/L, it found that the removal rates of synthetic and naturalα-FeOOH were 53.4% and 61.3% respectively. The concentration of treated PCP solution reduced to less than 5mg/L from 10mg/L that upgraded from third class to first class by （GB8978-1996） integrated wastewater discharge standard. The maximum adsorption capacity of synthetic ofα-FeOOH, 0.534mg/g, took place as the pH=6.0, for naturalα-FeOOH, it is 0.613mg/g at 6.0. The causal factor was that, comparing with syntheticα-FeOOH, naturalα-FeOOH had a larger BET surface area and higher surface site density. The adsorptions dynamics of natural and syntheticα-FeOOH on PCP in line with the first-order kinetics, the fitting kinetic equations were lgC = 1-0.1645t and lgC = 1-0.1325t respectively; the adsorption of naturalα-FeOOH on PCP accorded with the Freundlich isothermal equation; and with Langmuir isothermal equation for naturalα-FeOOH; the major adsorption mechanism forα-FeOOH on PCP was that adsorb PCP as hydrogen bond pattern by forming charge-dipole between >FeOH₂⁺ and C₆Cl₅O^-; after adsorption on PCP, natural and syntheticα-FeOOH could change toα-Fe₂O₃ by 500℃thermal regeneration, which with the adsorption capacity was better thanα-FeOOH’s, and good effect remained after times of 500℃thermal regenerations.The research on adsorption performance of naturalα-FeOOH on organic pollutants in papermaking wastewater indicated that, naturalα-FeOOH had a higher adsorption rate on COD in papermaking wastewater, and adsorption equilibrium took place in 60 minutes, when the concentration of COD in the wastewater was 394mg/L, 68.89% of COD changed to solid from liquid phase, when the concentration of COD below 150mg/L after mix papermaking wastewater and receiving water, the COD level in the treated wastewater met the demand of surface water quality I in GB3883-2002; the type of adsorption isotherm belonged to Langmuir, saturated adsorption rm=8.006mgCOD/g, adsorption constant k=10.26; phase change was carried out from natural goethite adsorption organic compound toα-Fe₂O₃ by 500℃calcinations, desorption rate was 87% after one time regeneration, good effect for adsorption capacity remained after times of adsorption-desorption.Preparedα-Fe₂O₃ by using homogeneous precipitation, and then testified the composition through X-ray diffract, FTIR and HRTEM, the crystallization of generatedα-Fe₂O₃ was good with no other impurities which belonged to hexagonal crystal, particle radius was less than 300nm, specific surface area was 37.24m²/g, point of zero charge of natural pH_ppzc =7.65.The research of adsorption performance for syntheticα-Fe₂O₃ on PCP indicated that, the adsorption on PCP of syntheticα-Fe₂O₃ reached adsorption-desorption dynamic equilibrium in 2.5 hours, the adsorptions dynamics accorded with the first order kinetics; fitting by Langmuir equation was preferred, the active group number in unit area ofα-Fe₂O₃ was larger thanα-FeOOH’s, better effect on PCP ofα-Fe₂O₃ by searing under 500℃for 60 minutes after the first time of adsorption, the adsorption performance could still remain 99.8% after 6 times of regenerations. The maximum adsorption capacity 6.5 mg/g occurred at the time when the pH value was 6.0, adsorption mechanism mainly belonged to electrostatic adsorption and with hydrogen bond as assistant, when the pH value at point of zero discharge reached7.65, the main adsorption method depended on hydrogen bond.Prepared magnetite by using coprecipitation, the synthetic sample was approved to be high purity Fe₃O₄ by X-ray diffraction, and then calculated the average particle radius to be 25nm by formula Debye-Scherrer, the laser particle analysis showed that average radius was 27.2nm. The adsorption rate of Fe₃O₄ on PCP was lower than goethite and hematite’s, when the pH value was 5, the adsorption capacity was the highest, 0.35mg/g, and the minimum adsorption capacity was lower than goethite and hematite’s, Freundlich for adsorption isotherm was preferred.Theα-Fe₂O₃ has a effected adsorption on the PCP, however, it is a powder material which is loose, easy hydrolysis and amorphous, and it has a poor permeability performance when used in fixed bed, moving bed reactor during intermittent process, difficult to dehydrate and big loss of adsorbent are its disadvantages, at the same time, it also produces a large amount of sludge and need additional treatment cost, based on previous which loadedα-Fe₂O₃ on quartz sand to prepare filter, this essay firstly, loadedα-Fe₂O₃ on the ceramic filtration ball which has a lager surface area, high porosity and low density through coprecipitation, and used detection technologies such as scanning electron microscope （SEM）, BET surface area（BET）, X-ray diffraction（XRD）, and high-resolution transmission electron microscopy （HRTEM） and so on to take analysis and characterization on loadα-Fe₂O₃, and load iron amount, adhesive performance, anti-acid and anti-base capacity is tested to show the performance of loadα-Fe₂O₃.Took Fe（NO₃）₃.9H₂O as raw materials and urea for homogeneous precipitant, loadedα-Fe₂O₃ on the ceramic filtration ball by coprecipitation. When molar ratio of CO（NH₂）₂ and Fe（NO₃）₃.9H₂O was 1.0 and the weight ratio of Fe（NO₃）₃.9H₂O and ceramic filtration ball was 0.2, heated ceramic filtration at 600℃for 1 hour, after this, the BET surface area increased from 0.973m²/g to 5.639m²/g which was 5.8 times than before, the pH value at point of zero charge increased from 5.8 to 7.8, load absorbentα-Fe₂O₃ had good performances on mechanical stability, anti-acid and anti-base, the weight loss rates were 0.352%, 2.387% and 0.568% respectively.The dynamic process of static adsorption of loadα-Fe₂O₃ on PCP was similar withα-Fe₂O₃’s, but the equilibrium adsorption capacity, 0.19 mg/g, was only 29.23% ofα-Fe₂O₃’s, 0.65mg/g; PCP removal rate presented a good relativity with the BET surface area of loadα-Fe₂O₃, it was clear that, as the incensement of BET surface area, the removal rate increased; the removal rate changed by the different pH values and adsorption mechanism of loadα-Fe₂O₃ on PCP were similar withα-Fe₂O₃ powder’s; distributive ratio and thermodynamics temperature regression equation of loadα-Fe₂O₃ on PCP, lnD=2.0577/T-1.8869, adsorption heat of adsorption reaction,△H =-17.1kJ/mol. The dynamic adsorption experiment of loadα-Fe₂O₃ on PCP showed that, when the loading height of absorption column was 30cm, empty bed contact time（EBCT） were 8 min, 12min, 16min respectively, the level of out water accorded to GB8978-1996 level 1 treatment time, which were 271min, 516min, 805min, the cumulative water production were 12810.5ml, 16211ml, 18955.6ml, bed rate were 50.28BV, 43BV, 34BV, the absorption capacity were 83%, 71% and 56% of static absorption capacity. Regeneration effect of adsorption of loadα-Fe₂O₃ on PCP was good, and the penetrated curve of PCP almost had no change after three times of regnerations at 600℃.In order to study on the performance of fixed bed honeycomb sorbentα-Fe₂O₃ on PCP, first time used oxygen-consuming corrosion on iron to productα-Fe₂O₃. The X-ray diffraction analysis on the pure iron assisted by oxygen showed that, besides Fe₃O₄, the surface does also includedα-Fe₂O₃, but the Raman Spectraon analysis on surface does indicted that, there was only one component,α-Fe₂O₃; the component in the middle layer of the samples was mainly divided into Fe₃O₄, followed with slight amount ofγ-FeOOH andα-Fe₂O₃; SEM analysis found that the surface oxide presented as dendrite, the pH value on the surface averagely was 7.22, the adsorption equilibrium time of loadα-Fe₂O₃ on PCP generated in-situ was 2.5 hours, peak occurred when the pH value was about 5.5, the maximum adsorption capacity was 0.55mg/cm²; Langmuir isothermal equation was preferred for fitting, it could regenerate by searing under 500℃for 1 hour, and the adsorption performance could still remain 99.9% after 4 times regenerations.As an absorbent on PCP in HIOCs wasterwater for adsorption treatment use,α-Fe₂O₃ will have a potential application prospect.更多还原