改性生物質材料制備及對水中砷吸附性能與處理工藝研究
發(fā)布時間：2018-08-30 12:55
【摘要】：為應對突發(fā)水環(huán)境砷污染事件,研發(fā)大流量、低流阻、低成本的應急吸附材料已成為一種實際的需求。本文以廢棄生物質材料木屑和咖啡渣為基體,采用化學方法制備改性木屑吸附材料和改性咖啡纖維素吸附材料;考查其對水中砷的吸附性能,并開展相關吸附機理的探討;采用改性木屑為吸附材料,分別建立吸附固定床工藝和吸附-超濾組合工藝,為水中砷的去除提供技術支持。以木屑為基體,環(huán)氧氯丙烷為醚化劑,二乙烯三胺為交聯(lián)劑,采用醚化交聯(lián)和鐵氧化物沉積的方法制備改性木屑吸附材料。優(yōu)化后的制備條件為:木屑與環(huán)氧氯丙烷的用量比例為1:3(即每千克木屑需要3 L環(huán)氧氯丙烷),木屑與二乙烯三胺的用量為1:1(即每千克木屑需要1 L二乙烯三胺),醚化反應溫度為90℃,醚化反應60 min,交聯(lián)反應溫度為70℃,交聯(lián)反應時間為120 min。實驗結果表明,醚化反應溫度和醚化劑用量是吸附材料制備過程中的關鍵影響因素。改性木屑吸附材料適用的最佳pH值范圍為5-6,對As(III)和As(V)的最大吸附容量分別為13.2和46.1 mg/g,優(yōu)于文獻中報道的結果。以咖啡渣為基體,經過氫氧化鈉溶液預處理后,用5%次氯酸鈉溶液反復漂洗提取咖啡纖維素,以聚乙烯亞胺(PEI)為氨化劑,以戊二醛為交聯(lián)劑,經絡合Fe(III)后制備改性咖啡纖維素吸附材料。優(yōu)化后的制備條件為:PEI的濃度為5%,氨基反應時間為120 min,交聯(lián)劑戊二醛的濃度為0.1%,交聯(lián)反應時間為240 min,Fe(NO3)3溶液的濃度為500 mg/L。與改性木屑吸附材料不同的是,改性咖啡纖維素絡合Fe(III)后,沒有采用加堿陳化的方法負載鐵氧化物,這是由于絡合Fe(III)可以顯著增加咖啡纖維素表面的Zeta電位,從而更好的實現(xiàn)對As(V)陰離子的吸附。弱酸性條件有利于As(V)的吸附,改性咖啡纖維素對As(V)的最大吸附容量為91 mg/g。改性咖啡纖維素吸附As(V)后,還可以實現(xiàn)對水中Cu(Ⅱ)的連續(xù)吸附,對Cu(Ⅱ)的最大吸附容量達到200 mg/L。分別對上述兩種改性生物質材料的吸附過程進行相關的模型擬合,結合兩種改性生物質材料的特點探討其對水中砷的吸附機理。吸附反應動力學研究結果表明,兩種改性生物質材料對水中砷的吸附過程均較好地符合擬二級反應動力學方程,表明兩種改性生物質材料對砷的吸附是一個以化學吸附為主的過程。Langmuir模型對兩種改性生物質材料吸附砷的擬合效果較好,表明砷在兩種改性生物質材料表面的吸附是單分子層化學吸附。吸附傳質機理模型表明,內部傳質系數[kLa]d在總傳質系數[kLa]g中的比例較大,表明主要的傳質阻力來自于砷與改性木屑表面活性吸附位點之間的物理化學反應,以及砷向吸附材料孔隙內部的擴散;對于改性咖啡纖維素,主要的傳質阻力來自于As(V)與改性咖啡纖維素表面活性吸附位點之間的物理化學反應。結合兩種改性生物質材料的特點探討其對水中砷的吸附機理,結果表明,負載在木屑表面的鐵氧化物對As(III)的吸附起主要作用,而接枝氨基對As(V)的吸附起主要作用;對于改性咖啡纖維素,接枝氨基和絡合三價鐵離子均顯著增加了吸附材料表面的Zeta電位,從而大大提高了對As(V)陰離子的吸附效果,As(V)和Cu(Ⅱ)在改性咖啡纖維素表面的連續(xù)吸附是靜電引力和表面絡合反應共同作用的結果。為了模擬實際應急處置中吸附壩的動態(tài)吸附過程,設計固定床吸附工藝裝置。對比不同填充高度及進水流量下的吸附穿透曲線。采用動態(tài)吸附模型對吸附過程進行擬合分析,Thomas模型擬合結果表明,當總砷的初始濃度為10 mg/L,流量為4.8 mL/min時,改性木屑濾床的飽和吸附容量達到15.6 mg/g;BDST模型擬合結果表明,改性木屑最大動態(tài)吸附速率常數達到3.13×10-4 L/min·mg,固定床穿透時間的模型擬合值和實測值之間的差異很小,表明BDST模型可以較好的預測不同柱高條件下,濾床到達飽和的穿透時間。為模擬實際應急處置中移動式處置過程,設計吸附-超濾組合工藝,完成對水中砷污染物的有效去除,同時實現(xiàn)對吸附飽和后吸附材料的有效分離。實驗結果表明,曝氣攪拌不僅可以使吸附材料在反應器中的混合更加均勻,還會增加水中溶解氧的含量,加速As(III)向As(V)的氧化,從而提高總砷的去除效率。對模擬含砷地表水條件下總砷的去除效果進行了研究,當總砷的初始濃度為0.1 mg/L時,經該組合工藝處理后出水砷濃度優(yōu)于I類地表水環(huán)境質量標準。研究表明,本文研制的生物質吸附材料及吸附處理工藝適用于突發(fā)水環(huán)境砷污染事件的應急處置技術要求。
[Abstract]:In order to cope with the arsenic pollution incidents in the water environment, it has become a practical demand to develop high flow rate, low flow resistance and low cost emergency adsorption materials. Adsorption properties and adsorption mechanism were discussed. Modified wood chips were used as adsorption materials to establish adsorption fixed bed process and adsorption-ultrafiltration combined process, respectively, to provide technical support for the removal of arsenic in water. The optimized preparation conditions were as follows: the ratio of sawdust to epichlorohydrin was 1:3 (that is, 3 L epichlorohydrin per kg of sawdust), the ratio of sawdust to diethylenetriamine was 1:1 (that is, 1 L diethylenetriamine per kg of sawdust), the etherification temperature was 90 C, the etherification reaction was 60 min, and the cross-linking reaction was trans-linked. The results showed that the etherification reaction temperature and the dosage of etherifying agent were the key factors in the preparation of the adsorbent. The optimum pH range of the modified wood chip adsorbent was 5-6, and the maximum adsorption capacity of As (III) and As (V) was 13.2 and 46.1 mg/g, respectively, which were better than those reported in literature. Result: The modified coffee cellulose adsorbent material was prepared by using coffee residue as matrix, pretreated with sodium hydroxide solution, rinsed and extracted repeatedly with 5% sodium hypochlorite solution, polyethylenimine (PEI) as ammoniating agent, glutaraldehyde as crosslinking agent, and complexed with Fe (III). The reaction time was 120 min, the concentration of glutaraldehyde was 0.1%, the crosslinking reaction time was 240 min, and the concentration of Fe (NO3) 3 solution was 500 mg/L. Unlike the modified sawdust adsorption material, the modified coffee cellulose complex with Fe (III) did not use alkali aging method to load iron oxide, because the complex Fe (III) could significantly increase the content of Caffee. The Zeta potential on the surface of enkephalin cellulose can better realize the adsorption of As (V). Weak acidity conditions are favorable for the adsorption of As (V). The maximum adsorption capacity of modified coffee cellulose for As (V) is 91 mg/g. After adsorbing As (V), the modified coffee cellulose can also achieve the continuous adsorption of Cu (II) in water, and the maximum adsorption capacity of Cu (II) can reach the maximum. To 200 mg/L, the adsorption processes of the two modified biomass materials were modeled and the adsorption mechanism of arsenic in water was discussed according to the characteristics of the two modified biomass materials. The Langmuir model showed that the adsorption of arsenic on the surface of the two modified biomass materials was a chemical adsorption process. The Langmuir model showed that the adsorption of arsenic on the surface of the two modified biomass materials was monolayer chemical adsorption. The larger proportion of internal mass transfer coefficient [kLa] D in total mass transfer coefficient [kLa] g indicates that the main mass transfer resistance comes from the physicochemical reaction between arsenic and the surface active adsorption sites of modified sawdust, as well as the diffusion of arsenic into the pores of adsorption materials; for modified coffee cellulose, the main mass transfer resistance comes from As (V) and modified coffee. The adsorption mechanism of arsenic in water was discussed based on the characteristics of two modified biomass materials. The results showed that the adsorption of As (III) by iron oxides loaded on wood chips played a major role, while the adsorption of As (V) by grafted amino groups played a major role. The Zeta potential on the surface of the adsorbent material was significantly increased by grafting amino group and complexing ferric ion, and the adsorption effect of As (V) and Cu (II) on the modified coffee cellulose surface was greatly improved. The continuous adsorption of As (V) and Cu (II) on the modified coffee cellulose surface was the result of the interaction of electrostatic attraction and surface complexation reaction. The adsorption process was fitted and analyzed by dynamic adsorption model. The results of Thomas model showed that when the initial concentration of total arsenic was 10 mg/L and the flow rate was 4.8 mL/min, the modified sawdust filter bed was saturated. The adsorption capacity reached 15.6 mg/g; BDST model fitting results showed that the maximum dynamic adsorption rate constant of modified sawdust reached 3.13 *10-4 L/min.mg, and the difference between model fitting value and measured value of fixed bed penetration time was very small, indicating that BDST model can better predict the filter bed penetration time to saturation under different column heights. A combined process of adsorption and ultrafiltration was designed to remove arsenic pollutants effectively and separate adsorbents saturated by adsorption. The experimental results show that aeration stirring can not only make the mixture of adsorbents more uniform in the reactor, but also increase the dissolution of adsorbents in water. The removal efficiency of total arsenic in simulated arsenic-containing surface water was studied. When the initial concentration of total arsenic was 0.1 mg/L, the concentration of arsenic in effluent treated by the combined process was better than that of the environmental quality standard of class I surface water. Material adsorption materials and adsorption process are suitable for emergency treatment of arsenic contamination in water environment.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：X52
[Abstract]:In order to cope with the arsenic pollution incidents in the water environment, it has become a practical demand to develop high flow rate, low flow resistance and low cost emergency adsorption materials. Adsorption properties and adsorption mechanism were discussed. Modified wood chips were used as adsorption materials to establish adsorption fixed bed process and adsorption-ultrafiltration combined process, respectively, to provide technical support for the removal of arsenic in water. The optimized preparation conditions were as follows: the ratio of sawdust to epichlorohydrin was 1:3 (that is, 3 L epichlorohydrin per kg of sawdust), the ratio of sawdust to diethylenetriamine was 1:1 (that is, 1 L diethylenetriamine per kg of sawdust), the etherification temperature was 90 C, the etherification reaction was 60 min, and the cross-linking reaction was trans-linked. The results showed that the etherification reaction temperature and the dosage of etherifying agent were the key factors in the preparation of the adsorbent. The optimum pH range of the modified wood chip adsorbent was 5-6, and the maximum adsorption capacity of As (III) and As (V) was 13.2 and 46.1 mg/g, respectively, which were better than those reported in literature. Result: The modified coffee cellulose adsorbent material was prepared by using coffee residue as matrix, pretreated with sodium hydroxide solution, rinsed and extracted repeatedly with 5% sodium hypochlorite solution, polyethylenimine (PEI) as ammoniating agent, glutaraldehyde as crosslinking agent, and complexed with Fe (III). The reaction time was 120 min, the concentration of glutaraldehyde was 0.1%, the crosslinking reaction time was 240 min, and the concentration of Fe (NO3) 3 solution was 500 mg/L. Unlike the modified sawdust adsorption material, the modified coffee cellulose complex with Fe (III) did not use alkali aging method to load iron oxide, because the complex Fe (III) could significantly increase the content of Caffee. The Zeta potential on the surface of enkephalin cellulose can better realize the adsorption of As (V). Weak acidity conditions are favorable for the adsorption of As (V). The maximum adsorption capacity of modified coffee cellulose for As (V) is 91 mg/g. After adsorbing As (V), the modified coffee cellulose can also achieve the continuous adsorption of Cu (II) in water, and the maximum adsorption capacity of Cu (II) can reach the maximum. To 200 mg/L, the adsorption processes of the two modified biomass materials were modeled and the adsorption mechanism of arsenic in water was discussed according to the characteristics of the two modified biomass materials. The Langmuir model showed that the adsorption of arsenic on the surface of the two modified biomass materials was a chemical adsorption process. The Langmuir model showed that the adsorption of arsenic on the surface of the two modified biomass materials was monolayer chemical adsorption. The larger proportion of internal mass transfer coefficient [kLa] D in total mass transfer coefficient [kLa] g indicates that the main mass transfer resistance comes from the physicochemical reaction between arsenic and the surface active adsorption sites of modified sawdust, as well as the diffusion of arsenic into the pores of adsorption materials; for modified coffee cellulose, the main mass transfer resistance comes from As (V) and modified coffee. The adsorption mechanism of arsenic in water was discussed based on the characteristics of two modified biomass materials. The results showed that the adsorption of As (III) by iron oxides loaded on wood chips played a major role, while the adsorption of As (V) by grafted amino groups played a major role. The Zeta potential on the surface of the adsorbent material was significantly increased by grafting amino group and complexing ferric ion, and the adsorption effect of As (V) and Cu (II) on the modified coffee cellulose surface was greatly improved. The continuous adsorption of As (V) and Cu (II) on the modified coffee cellulose surface was the result of the interaction of electrostatic attraction and surface complexation reaction. The adsorption process was fitted and analyzed by dynamic adsorption model. The results of Thomas model showed that when the initial concentration of total arsenic was 10 mg/L and the flow rate was 4.8 mL/min, the modified sawdust filter bed was saturated. The adsorption capacity reached 15.6 mg/g; BDST model fitting results showed that the maximum dynamic adsorption rate constant of modified sawdust reached 3.13 *10-4 L/min.mg, and the difference between model fitting value and measured value of fixed bed penetration time was very small, indicating that BDST model can better predict the filter bed penetration time to saturation under different column heights. A combined process of adsorption and ultrafiltration was designed to remove arsenic pollutants effectively and separate adsorbents saturated by adsorption. The experimental results show that aeration stirring can not only make the mixture of adsorbents more uniform in the reactor, but also increase the dissolution of adsorbents in water. The removal efficiency of total arsenic in simulated arsenic-containing surface water was studied. When the initial concentration of total arsenic was 0.1 mg/L, the concentration of arsenic in effluent treated by the combined process was better than that of the environmental quality standard of class I surface water. Material adsorption materials and adsorption process are suitable for emergency treatment of arsenic contamination in water environment.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：X52
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