本文選題：砷 + 混凝�。� 參考：《西安建筑科技大學》2015年博士論文

【摘要】：世界上許多地區(qū)都存在地下水砷污染問題,長期使用砷含量超標的水會導致皮膚癌和各種內(nèi)臟癌癥,嚴重威脅人體健康。如何高效地去除污染水中的砷,是安全飲用水供給要解決的重要問題之一。天然水中的砷主要是無機的三價砷(As(Ⅲ))和五價砷(As(Ⅴ)),其中As(Ⅲ)比As(V)毒性更大,更難去除。本論文提出了一種新的以鈦鹽為混凝劑的紫外光催化氧化混凝方法。研究這種方法氧化及高效去除As(Ⅲ)的效能,并提出了硫酸鈦紫外光催化混凝氧化As(Ⅲ)的機理。同時以鐵鹽為混凝劑,研究了鐵鹽水解初期沉淀物的粒徑和Zeta電位對鐵鹽混凝-過濾去除As(Ⅲ)和As(V)的影響。研究結果表明,以硫酸鈦為混凝劑的UVC (λ=254nm)紫外光催化氧化混凝(UVC/Ti(SO4)2混凝)可以在短時間內(nèi)有效地將As(Ⅲ)氧化成As(V),并能在pH=4-6時高效地將其去除。As 3d XPS分析表明,pH=5時,在UVC/Ti(SO4)2混凝去除As(Ⅲ)時產(chǎn)生的沉淀物表面,84.7%的砷是以As(V)的形態(tài)存在的。UVC/Ti(SO4)2混凝過濾后,濾液中剩余的砷都是氧化態(tài)的As(V)。在pH=4-6, As(Ⅲ)初始濃度為200μg/L,混凝劑投量中等(10mg/L)時,UVC/Ti(SO4)2混凝-微濾幾乎可以將As(Ⅲ)完全去除(99%)。由于As(Ⅲ)被氧化成As(Ⅴ), pH=5時,UVC/Ti(SO4)2混凝-微濾對As(Ⅲ)的去除率顯著大于單獨Ti(SO4)2混凝-微濾對As(Ⅲ)的去除率,這種優(yōu)勢在混凝劑投量較低(2.5mg/L)時更明顯。在As(Ⅲ)初始濃度為10～1000μg/L范圍內(nèi),UVC/Ti(SO4)2混凝對As(Ⅲ)的去除率受As(Ⅲ)初始濃度的影響較小。pH=5時,硅酸鹽對UVC/Ti(SO4)2混凝-微濾去除As(Ⅲ)的影響較小,磷酸鹽對UVC/Ti(SO4)2混凝-微濾去除。As(Ⅲ)的影響較大,增加混凝劑投量可以減少硅酸鹽和磷酸鹽對As(Ⅲ)去除的影響。pH=7時,Ca2+和Mg2+通過壓縮雙電層作用明顯降低了Ti(SO4)2水解沉淀物的負電位,從而減小了As(V)與Ti(SO4)2水解沉淀物之間的靜電斥力,提高了UVC/Ti(SO4)2混凝-微濾對As(Ⅲ)的去除率。單獨UVC紫外光對As(Ⅲ)的氧化效率較低(在反應21min后,僅為4.1%),由此表明UVC/Ti(SO4)2混凝對As(Ⅲ)的高效氧化不是由于紫外光的單獨氧化作用。通過對UVC/Ti(SO4)2混凝去除As(Ⅲ)時產(chǎn)生的沉淀物的Ti 2p XPS能譜分析表明,As(Ⅲ)的氧化也不是由As(Ⅲ)不Ti(Ⅳ)之間的直接電子轉(zhuǎn)移實現(xiàn)的。通過對羥基自由基捕獲劑(TBA、MeOH)、空穴捕獲劑(Ⅰ-)以及電子捕獲劑(Cu2+)對UVC/Ti(SO4)2混凝氧化去除As(Ⅲ)的影響的研究,結果表明As(Ⅲ)的氧化機理主要包括羥基自由基(OH·)及過氧自由基(HO2·/O2·-)的作用。研究進一步表明,與UVC/Ti(SO4)2混凝類似,UVA/Ti(SO4)2混凝(λ=365nm)也是一種有效的As(Ⅲ)氧化去除方法。對UVA/Ti(SO4)2混凝去除As(Ⅲ)的研究結果表明,在pH=4-6, As(Ⅲ)初始濃度為200μg/L,混凝劑投量較低(5mg/L)時,UVA/Ti(SO4)2混凝-微濾對As(Ⅲ)的去除率大于96.1%,顯著大于相同條件下單獨Ti(SO4)2混凝-微濾對As(Ⅲ)的去除率(68.7%)。pH=7～10時,UVA/Ti(SO4)2混凝-微濾對As(Ⅲ)的去除率下降。砷氧化態(tài)分析結果表明,UVA/Ti(SO4)2混凝-微濾后濾液中剩余的砷都是As(V)。在pH=8～10范圍內(nèi),SO42-的存在降低了UVA/Ti(SO4)2混凝-微濾對As(Ⅲ)的去除率。F-的存在在pH=4～10范圍內(nèi)均使UVA/Ti(SO4)2混凝-微濾對As(Ⅲ)的去除率有所降低,降低程度在pH=4時最大。本論文同時也對鐵鹽水解初期沉淀物的粒徑和Zeta電位對鐵鹽混凝-過濾去除As(Ⅲ)和As(V)的影響進行了系統(tǒng)的研究。結果表明,pH=5～10時,鐵鹽水解初期形成的沉淀物的顆粒粒徑都在膠體范圍內(nèi)(4-755nm)opH小于7時,顆粒帶正電,pH大于7時,顆粒帶負電。由于在pH=5～10范圍內(nèi)As(Ⅲ)主要以不帶電的中性分子形式存在,As(Ⅲ)與鐵鹽水解沉淀物之間不存在靜電力的作用,鐵鹽水解沉淀物的Zeta電位對鐵鹽混凝-過濾去除As(Ⅲ)沒有影響。而在pH=5～10范圍內(nèi)As(V)以帶負電的氧化陰離子形式存在,As(V)與鐵鹽水解沉淀物之間的靜電力作用對鐵鹽混凝-過濾去除As(V)影響較大。在鐵鹽水解沉淀物的Zeta電位為正(pH=5～7)時,As(V)與顆粒之間的靜電引力促進As(V)在顆粒表面的吸附,As(V)的去除率達到最大。顆粒的負電位較大時(pH=8～10), As(Ⅴ)與顆粒之間的靜電斥力阻礙As(V)的吸附,使As(V)的去除率明顯下降。在本研究的pH范圍內(nèi),含砷的鐵鹽水解沉淀物顆粒都可以被微濾和砂濾去除,顆粒粒徑對鐵鹽混凝-過濾去除As(Ⅲ)和As(V)沒有影響。pH=5～10時,增加一價電解質(zhì)(NaCl)濃度或加入二價電解質(zhì)(Ca(OH)2、 MgCl2)均會通過壓縮雙電層作用使FeCl3水解沉淀物的顆粒粒徑顯著增加。增加一價電解質(zhì)濃度對FeCl3水解沉淀物的Zeta電位影響較小,而加入二價電解質(zhì)顯著減小了pH=8～10時FeCl3水解沉淀物的負電位。增加一價電解質(zhì)濃度對FeCl3混凝-過濾去除As(Ⅲ)和As(Ⅴ)的影響較小。加入二價電解質(zhì)對As(Ⅲ)的去除影響較小但明顯增加了pH=8～10時As(Ⅴ)的去除率。加入HA時,FeCl3水解沉淀物的等電點由pH=7減小到pH=6。在pH=7～10時,HA的存在增加了FeCl3水解沉淀物的負電位。HA的存在使鐵鹽混凝-過濾去除As(Ⅲ)的效率在pH=5～10范圍內(nèi)均有所降低。在pH=5～8時,HA對As(Ⅴ)去除率的降低程度隨著pH的升高而增大�；炷コ榈膬煞N機理-吸附和共沉淀-的相對重要性取決于溶液pH。
[Abstract]:In many parts of the world, there is a problem of arsenic pollution in groundwater. Long term use of water with excessive arsenic content can lead to skin cancer and various visceral cancers. It is a serious threat to human health. How to effectively remove arsenic in polluted water is one of the important problems to be solved in the supply of safe drinking water. The arsenic in natural water is mainly inorganic arsenic (As). (III)) and pentvalent arsenic (As (V)), of which As (III) is more toxic than As (V) and is more difficult to remove. A new method of UV photocatalytic oxidation with titanium salts as coagulant was proposed in this paper. The efficiency of oxidation and efficient removal of As (III) by this method was studied and the mechanism of coagulation oxidation of As (III) by UV photocatalytic oxidation of titanium sulfate was proposed. For coagulant, the effect of the particle size and Zeta potential on the removal of As (III) and As (V) by the coagulation filtration of iron salt at the initial stage of hydrolysis was studied. The results showed that the UVC (UVC/Ti (SO4) 2 coagulation) with titanium sulfate as the coagulant (UVC/Ti (SO4)) could effectively oxidize As (III) to As (V) in a short time and can be in pH=4. .As 3D XPS analysis at -6 showed that the precipitate surface produced by UVC/Ti (SO4) 2 coagulating As (III) when UVC/Ti (SO4) 2 was coagulated, and the arsenic in As (V) was filtered by As (V), and the remaining arsenic in the filtrate was oxidized. The initial concentration was 200 mu, and the dosage of coagulant was moderate (10). At mg/L), UVC/Ti (SO4) 2 coagulation microfiltration can almost completely remove As (99%). As As (III) is oxidized to As (V), pH=5, UVC/Ti (SO4) 2 coagulation microfiltration is significantly greater than single Ti (SO4) 2 coagulation microfiltration for the removal of (III). This advantage is more obvious when the coagulant dosage is low. In the range of 10~1000 mu g/L, when the removal rate of UVC/Ti (SO4) 2 coagulation on As (III) is less affected by the initial concentration of As (III), the effect of silicate on the removal of As (III) by UVC/Ti (SO4) 2 coagulation microfiltration is smaller, and the effect of phosphate on UVC/Ti (SO4) 2 coagulation microfiltration to remove.As (III) is greater, and the dosage of coagulant can be increased to reduce the silicate and to reduce the silicate. When phosphate affects the removal of As (III), Ca2+ and Mg2+ significantly reduce the negative potential of Ti (SO4) 2 hydrolysate by compressing the double layer effect, thus reducing the electrostatic repulsion between As (V) and Ti (SO4) 2 hydrolysate precipitates, and increasing the removal rate of UVC/Ti (SO4) 2 coagulation micro filtration. The rate is low (only 4.1% after reaction 21min), which indicates that the efficient oxidation of UVC/Ti (SO4) 2 coagulation to As (III) is not due to the separate oxidation of ultraviolet light. The Ti 2p XPS energy spectrum analysis of the precipitates produced by UVC/Ti (SO4) 2 coagulation removal of As (III) shows that the oxidation of As (III) is not a direct electron transfer between As (III)). The effect of hydroxyl radical trapping agent (TBA, MeOH), hole capture agent (I) and electron capture agent (Cu2+) on the removal of As (III) by UVC/Ti (SO4) 2 by coagulation oxidation of As (III) was studied. The results showed that the oxidation mechanism of As (III) was mainly composed of hydroxyl radical (OH) and peroxy free radicals (HO2 /O2.). C/Ti (SO4) 2 coagulation is similar, UVA/Ti (SO4) 2 coagulation ([lambda] =365nm) is also an effective As (III) oxidation removal method. The results of UVA/Ti (SO4) 2 coagulation removal of As (III) show that when pH=4-6, As (III) initial concentration is 200 micron, and when the dosage of coagulant is low, the removal rate of 2 coagulant microfiltration is greater than 96.1%, significantly greater than that of 96.1%. Under the same condition, the removal rate of As (III) by UVA/Ti (SO4) 2 coagulation microfiltration was reduced when the removal rate of As (SO4) 2 coagulation microfiltration (68.7%) was.PH=7 ~ 10, and the arsenic oxidation state analysis showed that the remaining arsenic in the filtrate after UVA/Ti (SO4) 2 coagulation and microfiltration was As (V). Within the range of pH=8 to 10, the existence of 2 coagulation micro (2) was reduced. The removal rate of the removal rate of As (III).F- in the range of pH=4 ~ 10 makes UVA/Ti (SO4) 2 coagulation microfiltration decrease the removal rate of As (III), and the degree of reduction is maximum in pH=4. This paper also systematically studies the effect of the particle size and Zeta potential on the removal of As (III) and As (V) by molten iron salt coagulation filtration at the initial stage of hydrolysis of iron salts. The results show that the particle size of the precipitate formed at the initial stage of hydrolysis of iron salt from pH=5 to 10 is all in the colloid range (4-755nm) opH less than 7, the particles are positive, and when pH is more than 7, the particle band is negative. Because As (III) is mainly in the neutral form in pH=5 to 10, there is no electrostatic between As (III) and the hydrolytic precipitate of iron salt. The Zeta potential of iron salt hydrolyzed precipitate has no effect on the removal of As (III) by iron salt coagulation filtration. In the range of pH=5 ~ 10, As (V) exists in the form of negative oxide anion, and the electrostatic force between As (V) and the hydrolyzed precipitate of iron salt has great influence on the removal of As (V) by iron salt coagulation filtration and removal of As (V) in the iron salt solution. When the potential is positive (pH=5 to 7), the electrostatic attraction between As (V) and particles promotes the adsorption of As (V) on the surface of particles, and the removal rate of As (V) is maximum. When the negative potential of the particles is larger (pH=8 to 10), the electrostatic repulsion between As (V) and particles hinders the absorption of As (V), and the removal rate of As is obviously decreased. Within the scope of this study, the iron containing arsenic is in the range of this study. The particles of saltwater precipitate can be removed by microfiltration and sand filtration. When the particle size is not affected by As (III) and As (V), the concentration of monovalent electrolyte (NaCl) or the addition of two valence electrolyte (Ca (OH) 2, MgCl2) will increase the particle size of the hydrolysate precipitate by pressing the double layer. The concentration of monovalent electrolyte has little effect on the Zeta potential of FeCl3 hydrolysate, while adding two valence electrolyte significantly reduces the negative potential of FeCl3 hydrolysate at pH=8 ~ 10. Increasing the concentration of monovalent electrolyte has little effect on the removal of As (III) and As (V) by FeCl3 coagulation filtration. The addition of two valence electrolytes has little effect on the removal of As (III). The removal rate of As (V) at pH=8 ~ 10 was obviously increased. When the isoelectric point of FeCl3 hydrolysate was reduced from pH=7 to pH=6. at pH=7 to 10, the existence of HA increased the existence of the negative potential.HA of the FeCl3 hydrolysate precipitate, which reduced the efficiency of the removal of As (III) in the range of pH=5 ~ 10. The removal rate decreases with the increase of pH. The two mechanism of arsenic removal by coagulation is the adsorption and co precipitation. The relative importance depends on the solution pH..

【學位授予單位】：西安建筑科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TU991.2

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