【摘要】：硅垢是水體中的硅酸發(fā)生聚合反應或與金屬離子反應形成溶解度很低的沉淀。在水利用系統(tǒng)中,硅垢易附著在設備內壁和膜表面,堵塞管道和膜,減小流速,導致導熱不均勻,嚴重影響設備的正常運行,給工業(yè)生產(chǎn)帶來巨大經(jīng)濟損失與安全隱患。減小水體中的硅酸含量是防止硅垢形成的根本方法,工藝上常用離子交換法去除硅酸。溶解態(tài)的硅酸在水體中多以離子和分子的形式存在,離子交換法只能去除水體中的離子態(tài)硅酸,對分子態(tài)的硅酸處理效果不佳。因此,本研究用沒食子酸(GA)對離子交換樹脂進行接枝改性處理,以期實現(xiàn)對不同形態(tài)硅酸的去除目的。本研究對普通的OH型離子交換樹脂接枝GA,考察了溶液pH、離子強度和GA濃度變化對接枝量的影響,確定了 GA的最佳接枝條件。為研究GA型樹脂對硅酸的吸附性能,對比了改性后的GA型與普通OH型樹脂對硅酸的吸附效果,初步探討了硅酸與GA的反應機理,并研究了溶液中共存陰離子對GA型樹脂吸附硅酸的影響。利用不同的吸附等溫模式、吸附動力學模式和吸附熱力學對實驗數(shù)據(jù)進行擬合,研究GA型樹脂對硅酸的吸附機理。為探討改性樹脂的重復利用性,研究了不同洗脫液對吸硅GA型樹脂的脫附效果,確定最佳洗脫液,同時對GA型樹脂對硅酸的循環(huán)吸附去除效果做出了綜合評價。所得主要結論如下:(1)普通的OH型樹脂可以接枝GA,且其最佳接枝條件為:溶液pH為6-7之間、離子強度為零、GA濃度為2.5g/L,最大接枝量為340.3 mg/g。(2)GA型樹脂對溶液中可溶性的硅酸(分子態(tài)和離子態(tài))都有一定的吸附性,溶液pH變化對GA型樹脂吸附硅酸無明顯影響,且不同pH條件下GA型樹脂對硅酸的去除率和吸附量均遠大于OH型,是OH型的30倍。(3)GA型樹脂對硅酸具有較高的選擇性吸附。低濃度的共存陰離子不影響GA型樹脂對硅酸的吸附,陰離子濃度升高時會降低GA型樹脂對硅酸吸附量,且多種陰離子共存對吸附量的影響要大于單一陰離子的存在。(4)GA型樹脂對硅酸的飽和吸附量為6.471 mg/g(以Si為計),吸附量遠大于OH型樹脂,且受水環(huán)境要素的影響較小。吸附過程更符合Temkin吸附等溫模式和準二級動力學模式,顆粒內擴散和化學反應是控制反應速率快慢的主要步驟,表明硅酸是通過化學吸附作用吸附在GA型樹脂上。熱力學結果表明,反應是自發(fā)、吸熱的物理化學吸附過程。綜合動力學和熱力學研究結果得知,GA型樹脂對硅酸的吸附過程是物理吸附和化學吸附共同作用的結果。(5)吸附硅酸的GA型樹脂在堿性條件下脫附硅酸的效果最好,在不對樹脂進行再接枝的條件下,GA型樹脂對硅酸的兩次循環(huán)吸附去除率均在90%以上,效果良好,可以每循環(huán)吸附兩次進行一次接枝處理。
[Abstract]:Silicon scale is a precipitate in which silicic acid in water is polymerized or reacts with metal ions to form very low solubility. In the water utilization system, silicon dirt is easily attached to the inner wall and the membrane surface of the equipment, clogging the pipes and membranes, reducing the velocity of flow, causing uneven heat conduction, seriously affecting the normal operation of the equipment, and bringing huge economic losses and hidden dangers to the industrial production. Reducing the content of silicic acid in water is the basic method to prevent the formation of silicon scale. The dissolved silicic acid exists in the form of ions and molecules in the water. Ion exchange method can only remove the ionic silicic acid in the water body, but the effect of the molecular silicic acid treatment is not good. Therefore, the ion exchange resin was grafted with Gallic acid (GA) in order to achieve the removal of different forms of silicic acid. In this study, the effects of pH, ion strength and GA concentration on the grafted GA, grafted with common OH ion-exchange resin were investigated, and the optimum grafting conditions of GA were determined. In order to study the adsorption properties of GA resin for silicic acid, the adsorption effect of modified GA resin and common OH resin on silicic acid was compared, and the reaction mechanism of silicic acid with GA was preliminarily discussed. The influence of anions in solution on the adsorption of silicic acid by GA resin was studied. The adsorption mechanism of silicic acid on GA resin was studied by fitting the experimental data with different adsorption isotherm models, adsorption kinetics models and adsorption thermodynamics. In order to study the reusability of modified resin, the desorption effect of different eluents on GA resin was studied, and the optimum elution solution was determined. At the same time, a comprehensive evaluation was made on the removal of silicic acid by circulating adsorption of GA resin. The main conclusions are as follows: (1) ordinary OH resin can graft GA, and the optimum grafting conditions are as follows: solution pH is 6-7, ionic strength is zero, GA concentration is 2.5 g / L. The maximum grafted amount of 340.3 mg/g. (2) GA resin had a certain degree of adsorption on soluble silicic acid (molecular state and ionic state) in the solution, and the change of pH had no obvious effect on the adsorption of silicic acid by GA type resin. The removal rate and adsorption capacity of silicic acid by GA resin under different pH conditions are much higher than those of OH type and 30 times of that of OH type. (3) GA resin has higher selective adsorption of silicic acid. The low concentration of anions did not affect the adsorption of silicic acid on GA resin. The increase of anionic concentration would decrease the amount of silicic acid adsorbed by GA resin. The effect of coexistence of anions on the adsorption capacity of silicic acid was greater than that of a single anion. (4) the saturated adsorption capacity of silicic acid by GA resin was 6.471 mg/g (in terms of Si), and the adsorption capacity was much larger than that of OH type resin. And the influence of water environmental factors is relatively small. The adsorption process is more in line with the Temkin adsorption isotherm model and the quasi-second-order kinetic model. The diffusion in particles and chemical reaction are the main steps to control the reaction rate. It is shown that silicic acid is adsorbed on GA resin by chemical adsorption. Thermodynamic results show that the reaction is a spontaneous, endothermic physicochemical adsorption process. The results of kinetics and thermodynamics show that the adsorption process of silicic acid by GA resin is the result of both physical and chemical adsorption. (5) the desorption of silicic acid by GA resin adsorbed silicic acid is the best in alkaline condition. Under the condition that the resin is not regrafted, the removal rate of twice cyclic adsorption of silicic acid by GA resin is above 90%, and the effect is good, and the graft treatment can be carried out twice per cycle.
【學位授予單位】：內蒙古大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ425.23;O647.3

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