發(fā)布時間：2018-06-05 01:34

  本文選題：果膠 + 可變電荷土壤��； 參考：《南京林業(yè)大學(xué)》2017年博士論文

【摘要】：我國南方熱帶和亞熱帶地區(qū)分布著大面積的可變電荷土壤�？勺冸姾赏寥赖挠坞x鐵鋁氧化物含量較高,pH值和陽離子交換量較低。因此這類土壤中重金屬的活性和生物有效性較北方恒電荷土壤要高,也更容易受重金屬的污染。果膠是植物根尖粘液中的一種成分,果膠參與土壤中許多重要的反應(yīng)。植物通過根系吸收土壤溶液中的有效金屬,這使得土壤溶液中重金屬的濃度對生態(tài)系統(tǒng)尤為重要。植物分泌的粘液可以進(jìn)去根際土壤,粘液可以被可變電荷土壤吸附,正如有機酸能增加重金屬吸附作用那樣,從而降低重金屬在根際土壤中的活性�；谝陨涎芯勘尘�,論文應(yīng)用果膠添加到可變電荷土壤中,模擬根際土壤中的真實情況。旨在探明植物根尖粘液中的果膠對可變電荷土壤吸附重金屬的影響,揭示植物根尖分泌物對重金屬在根-土-水界面中的化學(xué)行為的影響。研究果膠的添加量、重金屬離子的初始濃度、體系的pH對可變電荷土壤吸附銅(Cu)、鎘(Cd)的影響。研究果膠對無定形鐵鋁氫氧化物吸附重金屬的影響,闡明果膠增強可變電荷土壤吸附重金屬的直接機理。研究果膠參與的鋁水解物的表面性質(zhì)及其吸附重金屬的影響,闡明果膠增強可變電荷土壤吸附重金屬的間接機理。綜合運用多種分析技術(shù)(紅外光譜、Zeta電位、表面電荷測定、電子顯微鏡、X射線衍射)探究果膠影響可變電荷吸附重金屬吸附的機理。主要結(jié)果如下:(1)果膠促進(jìn)了兩種可變電荷土壤(磚紅壤和紅壤)對銅的吸附。增加量與果膠的添加量成線性關(guān)系,磚紅壤的增加量比紅壤的增加更大。Langmuir和Freundlich方程擬合可變電荷土壤對銅的吸附等溫線。兩個方程的擬合參數(shù)表明,果膠不僅增加了土壤對銅吸附量,也增加了吸附強度。在體系pH 3.0-6.0條件下,隨著pH的升高,雖然靜電吸附有所增加,但是果膠增加靜電吸附的作用減小。傅里葉變換紅外光譜分析和Zeta電位測定表明:土壤膠體吸附果膠后,使得其表面負(fù)電荷更大,導(dǎo)致可變電荷土壤對銅的靜電吸附增加。總之,果膠能增強可變電荷土壤對銅的吸附,特別是在低pH值的條件下。果膠可以降低銅在酸性可變電荷土壤中的活性性和可移動性。(2)果膠促進(jìn)了兩種可變電荷土壤(磚紅壤和紅壤)對鎘的吸附。當(dāng)果膠用量小于30 g/kg時,隨著添加量的增加,其對可變電荷土壤吸附鎘的促進(jìn)作用大于其添加量大于30g/kg時。雖然Langmuir和Freundlich方程都能擬合鎘的等溫吸附和靜電吸附的等溫線,朗格繆爾方程具有較好的擬合效果。由于果膠的存在,兩種可變電荷土壤對鎘的最大吸附量的增加幾乎相等,而磚紅壤對鎘的最大靜電吸附的增加遠(yuǎn)大于紅壤。因為磚紅壤比紅壤含有更大量的游離鐵、鋁氧化物,導(dǎo)致磚紅壤表面的負(fù)電荷增加更多。因此,果膠主要通過靜電機制增加可變電荷土壤對鎘的吸附。果膠增加可變電荷土壤對鎘的吸附,從而降低鎘在可變電荷土壤中的活性和可移動性。(3)研究了果膠對無定形鐵鋁氫氧化物吸附銅鎘的影響,揭示果膠對可變電荷土壤吸附重金屬直接影響的證據(jù)。運用電子顯微鏡和X衍射儀對礦物表面進(jìn)行觀察;運用紅外光譜儀對礦物的表面官能團(tuán)進(jìn)行分析。在pH 3.5-6.5之間,無定形鋁氫氧化物對果膠的吸附量遠(yuǎn)遠(yuǎn)大于無定形鐵的吸附量,因為無定形鋁氫氧化物具有更高的正電荷密度,因此與果膠之間具有更大的靜電作用。果膠的加入降低了無定形鐵鋁氫氧化物表面的正電荷。果膠增加了無定形鐵鋁氫氧化物對銅的吸附。無定形鐵氫氧化物對銅的吸附增量,在低pH條件下高于高pH條件下;而無定形鋁氫氧化物具有相反的趨勢。當(dāng)pH3.9,4.3,4.9時,無定型鐵氫氧化物對銅的吸附量分別從24.4,76.6,177.0 mmol/kg升高到61.6,98.8,192.0mmol/kg,增加了37.2,22.2,15.0 mmol/kg。當(dāng)pH為4.3和4.9時,無定型鋁氫氧化物對銅的吸附量分別從3.7和27.0 mmol/kg升高到17.3和69.4 mmol/kg,增加了13.6和42.4mmol/kg。相對與無定形鐵氫氧化物,無定形鋁氫氧化物吸附更多的果膠,主要導(dǎo)致在高pH條件下對銅的吸附增加。無定形鐵鋁氫氧化物吸附果膠,降低了其表面正電荷,增加了鐵鋁氫氧化物對銅的吸附。果膠對無定形鐵鋁吸附鎘的影響與銅的影響相類似。(4)研究了果膠對鋁水解產(chǎn)物的表面性質(zhì)的影響,揭示了果膠促進(jìn)可變電荷土壤吸附重金屬的間接影響的機制。通過X衍射、表面形貌和紅外光譜對果膠存在下鋁的水解產(chǎn)物的表面結(jié)構(gòu)進(jìn)行表征,證實了果膠使得鋁水解產(chǎn)物的結(jié)晶度下降,形成了結(jié)構(gòu)中的缺陷。果膠降低了鋁水解產(chǎn)物的等電點和表面正電荷。隨著果膠添加量增加,效果越明顯。果膠增加了鋁水解產(chǎn)物對銅的吸附。綜上所述,本文選取磚紅壤和紅壤兩種可變電荷土壤為研究對象,通過模擬實驗的方法,研究發(fā)現(xiàn)果膠可以促進(jìn)可變電荷土壤對銅鎘的吸附。通過對無定形鐵鋁氧化物的研究,果膠的吸附,降低了氧化物表面的正電荷,揭示了果膠促進(jìn)可變電土壤吸附重金屬的直接影響的機制。其次,在我國南方地區(qū),果膠也可以通過影響鋁水解產(chǎn)物,降低其表面正電荷,對果膠促進(jìn)可變電荷土壤吸附重金屬具有間接影響的作用。因此,果膠可以促進(jìn)可變電荷土壤中的重金屬的吸附,從而降低毒重金屬在可變電荷土壤中的活性。
[Abstract]:A large area of variable charge soil is distributed in the tropical and subtropical regions of the south of China. The free iron and aluminum oxide content of the variable charge soil is higher, the pH value and the cation exchange rate are lower. Therefore, the activity and bioavailability of heavy metals in this kind of soil are higher than that in the northern constant charge soil, and are more susceptible to heavy metal pollution. Pectin is planted. A component in the mucus of the root apex. Pectin participates in many important reactions in the soil. Plants absorb the effective metals in the soil solution by the root system. This makes the concentration of heavy metals in the soil solution important to the ecosystem. The mucus secreted by plants can go into the rhizosphere soil, and the mucus can be adsorbed by the variable charge soil, just as there is one. Organic acid can increase the adsorption of heavy metals to reduce the activity of heavy metals in the rhizosphere soil. Based on the above research background, the paper uses pectin into the variable charge soil to simulate the true situation in the rhizosphere soil. The purpose is to explore the effect of pectin on the adsorption of heavy metals on variable charge soil in the root tip mucus. The effect of plant root exudates on the chemical behavior of heavy metals in the root soil water interface. The effect of the amount of pectin, the initial concentration of heavy metal ions, the effect of pH on the adsorption of copper (Cu) and cadmium (Cd) on the variable charge soil. The effect of pectin on the adsorption of heavy metals on the amorphous iron and aluminum hydrogen oxidizing substances was studied, and the enhanced variable charge of pectin was clarified. The direct mechanism of soil adsorption on heavy metals. The study of the surface properties of the aluminum hydrolysates involved in pectin and the influence of heavy metals on the adsorption of heavy metals, and to elucidate the indirect mechanism of the adsorption of heavy metals by pectin reinforced variable charge soils. The comprehensive application of various analytical techniques (infrared spectroscopy, Zeta potential, surface charge determination, electron microscope, X ray diffraction) to explore pectin The main results are as follows: (1) pectin promotes the adsorption of two variable charge soils (brick red soil and red soil) to copper. The increase is linear with the addition of pectin, and the increase of red soil is greater than that of red soil by.Langmuir and Freundlich equation fitting variable charge soil to copper The adsorption isotherm. The fitting parameters of the two equations show that pectin not only increases the adsorption capacity of soil to copper, but also increases the adsorption strength. Under the condition of system pH 3.0-6.0, the electrostatic adsorption increases with the increase of pH, but the effect of pectin on the increase of electrostatic adsorption is reduced. The Fourier transform infrared spectrum analysis and the Zeta potential meter The soil colloid adsorbed pectin on the pectin, which makes the surface charge more negative, which leads to the increase of electrostatic adsorption of copper in variable charge soil. In conclusion, pectin can enhance the adsorption of copper by the variable charge soil, especially under the low pH value. Pectin can reduce the activity and mobility of copper in the acid variable charged soil. (2) pectin promotion Two kinds of variable charge soils (brick red soil and red soil) adsorb cadmium. When the amount of pectin is less than 30 g/kg, with the increase of adding amount, the promotion effect on the adsorbed cadmium in variable charge soil is greater than that of 30g/kg. Although both Langmuir and Freundlich equation can fit the isothermal adsorption isotherm of cadmium and the electrostatic adsorption isotherm, Lange The Muir equation has a good fitting effect. Due to the existence of pectin, the increase of the maximum adsorption of cadmium in two kinds of variable charge soils is almost equal, while the maximum electrostatic adsorption of cadmium in red soil is much greater than that in red soil. Adding more. Therefore, pectin mainly increases the adsorption of cadmium in variable charge soil by electrostatic mechanism. Pectin increases the adsorption of cadmium in variable charge soil, thus reducing the activity and mobility of cadmium in variable charge soil. (3) the effect of pectin on the adsorption of copper and cadmium on amorphous iron aluminum hydroxide is studied, and the effect of pectin to variable charge soil is revealed. Evidence of the direct influence of soil adsorption on heavy metals. The surface of minerals is observed by electron microscope and X diffraction instrument; the surface functional groups of minerals are analyzed by infrared spectrometer. Between pH 3.5-6.5, the adsorption amount of amorphous aluminum hydroxide on pectin is much greater than that of amorphous iron because of amorphous aluminum hydroxide. There is a higher positive charge density, so there is greater electrostatic interaction with pectin. The addition of pectin reduces the positive charge on the amorphous iron aluminum hydroxide surface. Pectin increases the adsorption of amorphous iron aluminum hydroxide to copper. The adsorption increment of amorphous iron hydroxide on copper is higher under the low pH condition than the high pH condition; Aluminum hydroxide has the opposite trend. When pH3.9,4.3,4.9, the adsorption capacity of amorphous iron hydroxide on copper increases from 24.4,76.6177.0 mmol/kg to 61.6,98.8192.0mmol/kg, respectively, increasing 37.2,22.2,15.0 mmol/kg. when pH is 4.3 and 4.9, and the adsorption of amorphous aluminum hydroxide on copper increases from 3.7 and 27 mmol/kg to 17, respectively. .3 and 69.4 mmol/kg increased 13.6 and 42.4mmol/kg. relative to amorphous iron hydroxide, and amorphous aluminum hydroxide adsorbed more pectin, which mainly resulted in increased adsorption of copper under high pH conditions. The effect of amorphous iron and aluminum on cadmium adsorption is similar to that of copper. (4) the effect of pectin on the surface properties of aluminum hydrolysates was studied, and the mechanism of the indirect effect of pectin on the adsorption of heavy metals on variable charge soil was revealed. Surface structure of the hydrolysate of aluminum in the presence of fruit gum was observed by X diffraction, surface morphology and infrared spectroscopy. It is confirmed that pectin makes the crystallinity of the hydrolysate of aluminum decrease and forms a defect in the structure. Pectin reduces the isoelectric point and surface positive charge of the hydrolysate of aluminum. As the amount of pectin is increased, the effect is more obvious. The pectin increases the adsorption of aluminum hydrolysate to copper. In this paper, two kinds of variable charges in red soil and red soil are selected. The soil is the research object. Through the simulation experiment, it is found that pectin can promote the adsorption of copper and cadmium by the variable charge soil. Through the study of the amorphous iron and aluminum oxide, the adsorption of pectin, the positive charge of the oxide surface is reduced, and the mechanism of the effect of pectin to promote the adsorption of heavy metals on the variable electric soil is revealed. Secondly, the mechanism of the effect of the pectin on the adsorption of heavy metals on the variable electric soil is revealed. In southern China, pectin can also reduce the surface positive charge by influencing the hydrolysate of aluminum, which has an indirect effect on the adsorption of heavy metals by pectin on variable charge soil. Therefore, pectin can promote the adsorption of heavy metals in variable charge soil, thus reducing the activity of toxic heavy metals in variable charge soils.
【學(xué)位授予單位】：南京林業(yè)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：X53;S153

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